U.S. patent application number 13/282533 was filed with the patent office on 2012-05-03 for overmolded polyamide composite structures and processes for their preparation.
This patent application is currently assigned to E. I. DU PONT DE NEMOURS AND COMPANY. Invention is credited to Andri E. Elia, Olaf Norbert Kirchner, David V. Mesaros, Martyn Douglas Wakeman, Shengmei Yuan.
Application Number | 20120108124 13/282533 |
Document ID | / |
Family ID | 44936546 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120108124 |
Kind Code |
A1 |
Elia; Andri E. ; et
al. |
May 3, 2012 |
OVERMOLDED POLYAMIDE COMPOSITE STRUCTURES AND PROCESSES FOR THEIR
PREPARATION
Abstract
Disclosed are overmolded composites structures and processes for
their preparation. The overmolded composite structures comprise i)
a first component having a surface, having at least a portion made
of a surface resin composition, and comprising a fibrous material
impregnated with a matrix resin composition, ii) a second component
comprising an overmolding resin composition, and adhered to said
first component over at least a portion of the surface of said
first component. The matrix resin composition and the surface resin
composition are identical or different and are selected from
polyamide compositions comprising a blend of (A) one or more fully
aliphatic polyamides selected, and (B) one or more semiaromatic
polyamides having a melting point of at least 280.degree. C.
Inventors: |
Elia; Andri E.; (Chadds
Ford, PA) ; Kirchner; Olaf Norbert; (Genolier,
CH) ; Mesaros; David V.; (Salida, CO) ;
Wakeman; Martyn Douglas; (Gland, CH) ; Yuan;
Shengmei; (Newark, DE) |
Assignee: |
E. I. DU PONT DE NEMOURS AND
COMPANY
Wilmington
DE
|
Family ID: |
44936546 |
Appl. No.: |
13/282533 |
Filed: |
October 27, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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61408166 |
Oct 29, 2010 |
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61410093 |
Nov 4, 2010 |
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61410100 |
Nov 4, 2010 |
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61410104 |
Nov 4, 2010 |
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61410108 |
Nov 4, 2010 |
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Current U.S.
Class: |
442/59 ;
264/257 |
Current CPC
Class: |
B29C 45/14786 20130101;
Y10T 442/674 20150401; B32B 2605/00 20130101; B32B 2260/046
20130101; B29K 2709/08 20130101; B32B 5/024 20130101; Y10T
428/24994 20150401; Y10T 442/2041 20150401; B32B 2260/023 20130101;
Y10T 428/249924 20150401; Y10T 428/31728 20150401; Y10T 442/20
20150401; Y10T 442/2992 20150401; Y10T 442/2721 20150401; B29C
45/0001 20130101; B32B 2264/12 20130101; Y10T 442/2762 20150401;
B29K 2677/00 20130101; B32B 27/34 20130101; Y10T 442/2631 20150401;
B32B 2264/10 20130101; Y10T 428/31725 20150401; C08K 7/20 20130101;
Y10T 428/249921 20150401; B29K 2077/00 20130101; B32B 2307/546
20130101; C08L 77/06 20130101; B32B 2260/021 20130101; B32B
2307/306 20130101; Y10T 428/31623 20150401; C08J 5/043 20130101;
C08L 77/06 20130101; C08L 77/06 20130101; C08L 77/06 20130101; C08K
7/20 20130101; B32B 27/12 20130101; B32B 2262/101 20130101; B32B
2307/308 20130101; C08L 2205/02 20130101; C08J 2377/06 20130101;
C08L 77/06 20130101; Y10T 442/2861 20150401; B32B 5/26 20130101;
Y10T 442/2984 20150401 |
Class at
Publication: |
442/59 ;
264/257 |
International
Class: |
B32B 27/04 20060101
B32B027/04; B29C 45/14 20060101 B29C045/14 |
Claims
1. An overmolded composite structure comprising: i) a first
component having a surface, which surface has at least a portion
made of a surface resin composition, and comprising a fibrous
material selected from non-woven structures, textiles, fibrous
battings and combinations thereof, said fibrous material being
impregnated with a matrix resin composition, wherein the matrix
resin composition and the surface resin composition are identical
or different and are selected from polyamide compositions
comprising a blend of (A) one or more fully aliphatic polyamides
selected from group (I) polyamides, and (B) one or more
semiaromatic polyamides selected from group (II) polyamides having
a melting point of at least 280.degree. C.; and ii) a second
component comprising an overmolding resin composition, wherein said
second component is adhered to said first component over at least a
portion of the surface of said first component, and
2. The overmolded composite structure according to claim 1, wherein
the overmolding resin composition is selected from polyamide
compositions comprising a blend of (A) one or more fully aliphatic
polyamides selected from group (I) polyamides, and (B) one or more
semiaromatic polyamides selected from group (II) polyamides having
a melting point of at least 280.degree. C.
3. The overmolded composite structure according to claim 1 wherein
the one or more fully aliphatic polyamides selected from group (I)
polyamides have a melting point of less than 280.degree. C.
4. The overmolded composite structure according claim 1, wherein
the fibrous material is made of glass fibers, carbon fibers, aramid
fibers, natural fibers or mixtures thereof.
5. The overmolded composite structure according to claim 1, wherein
the fibrous material is made of glass fibers.
6. The overmolded composite structure according to claim 1 wherein
the fibrous material is from 30 volume percent to 60 volume percent
of the first component.
7. The overmolded composite structure according to claim 1, wherein
the weight ratio of the one or more polyamides selected from group
(I) polyamides (A) and the one or more polyamides selected from
group (II) polyamides (B) (A:B) of the polyamide composition is
between from about 99:1 to about 5:95.
8. The overmolded composite structure according claim 1 further
comprising one or more additives selected from the group consisting
of heat stablizers, oxidative stabilizers, reinforcing agents,
flame retardants or combination thereof.
9. The overmolded composite structure according to claim 1 wherein
the one or more fully aliphatic polyamides selected from group (I)
polyamides is selected form the group consisting of PA46, PA 6, PA
66; PA510, PA512, PA6/66, PA6/610, PA6/612, PA613, PA615,
PA6/66/610, PA6/66/612, PA6/66/610/612, PA D6/66, PA1010, PA1012,
PA11, PA12, PA612, PA1212, and their copolymers and
combinations.
10. The overmolded composite structure according to claim 1 wherein
the one or more fully semi-aromatic polyamides selected from group
(II) polyamides is selected form the group consisting of PA6/4T,
PA6/6T, PA6/10T, PA6/12T, PA610/6T, PA612/6T, PA614/6T, PA6/6I/6T,
PA D6/66/6T, PA 6TDT, PA1010/10T, PA1010/1210/10T/12T, PA11/4T,
PA11/6T, PA11/10T, PA11/12T, PA12/4T, PA12/6T, PA12/10T PA1212/12T,
PA66/6T, PA6I/6T, PA66/6I/6T, PA6T/6I, and their copolymers and
combinations.
11. The overmolded composite structure according to claim 1 wherein
the one or more fully aliphatic polyamides selected from group (I)
polyamides is selected form the group consisting of PA66, PA46 and
PA6 and wherein the one or more fully semi-aromatic polyamides
selected from group (II) polyamides is selected form the group
consisting of PA66/6T, PA6TDT, PA6I/6T, PA66/6I/6T, PA6T/6I, and
their copolymers and combinations thereof.
12. The overmolded composite structure according to claim 1 in the
form of a component for automobiles, trucks, commercial airplanes,
aerospace, rail, household appliances, computer hardware, hand held
devices, recreation and sports, structural component for machines,
structural components for buildings, structural components for
photovoltaic equipments or structural components for mechanical
devices.
13. A process for making the overmolded composite structure of
claim 1 comprising a step of overmolding a second component
comprising an overmolding resin composition on a first component,
wherein the first component comprises a fibrous material and has a
surface, said surface having at least a portion made of a surface
resin composition, said fibrous material is selected from non-woven
structures, textiles, fibrous battings and combinations thereof and
said fibrous material being impregnated with a matrix resin
composition, wherein the matrix resin composition, and the surface
resin composition are identical or different and are selected from
polyamide compositions comprising a blend of (A) one or more fully
aliphatic polyamides selected from group (I) polyamides, and (B)
one or more semiaromatic polyamides selected from group (II)
polyamides having a melting point of at least 280.degree. C.
14. The process according to claim 13, wherein the overmolding
resin composition is selected from polyamide compositions
comprising a blend of (A) one or more fully aliphatic polyamides
selected from group (I) polyamides, and (B) one or more
semiaromatic polyamides selected from group (II) polyamides having
a melting point of at least 280.degree. C.
15. The process according to claim 13 wherein the one or more fully
aliphatic polyamides selected from group (I) polyamides have a
melting point of less than 280.degree. C.
16. The process according to claim 13, further comprising a step of
shaping the first component before the step of overmolding.
17. The process according to claim 13, wherein the first component
is heated before the step of overmolding to soften and partially
melt a surface which will form an interface with the overmolding
resin composition.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Application No. 61/408,166, filed Oct. 29, 2010, which
is now pending, the entire disclosure of which is incorporated
herein by reference; and U.S. Provisional Application Nos.
61/410,093, filed Nov. 4, 2010; 61/410,100, filed Nov. 4, 2010;
61/410,104, filed Nov. 4, 2010; and 61/410,108, filed Nov. 4, 2010,
all of which are now pending, the entire disclosures of which are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to the field of overmolded
composite structures and processes for their preparation,
particularly it relates to the field of polyamide overmolded
composite structures.
BACKGROUND OF THE INVENTION
[0003] With the aim of replacing metal parts for weight saving and
cost reduction while having comparable or superior mechanical
performance, structures based on composite materials comprising a
polymer matrix containing a fibrous material have been developed.
With this growing interest, fiber reinforced plastic composite
structures have been designed because of their excellent physical
properties resulting from the combination of the fibrous material
and the polymer matrix and are used in various end-use
applications. Manufacturing techniques have been developed for
improving the impregnation of the fibrous material with a polymer
matrix to optimize the properties of the composite structure.
In highly demanding applications, such as for example structural
parts in automotive and aerospace applications, composite materials
are desired due to a unique combination of lightweight, high
strength and temperature resistance.
[0004] High performance composite structures can be obtained using
thermosetting resins or thermoplastic resins as the polymer matrix.
Thermoplastic-based composite structures present several advantages
over thermoset-based composite structures such as, for example, the
fact that they can be post-formed or reprocessed by the application
of heat and pressure, that a reduced time is needed to make the
composite structures because no curing step is required, and their
increased potential for recycling. Indeed, the time consuming
chemical reaction of cross-linking for thermosetting resins
(curing) is not required during the processing of thermoplastics.
Among thermoplastic resins, polyamides are particularly well suited
for manufacturing composite structures. Thermoplastic polyamide
compositions are desirable for use in a wide range of applications
including parts used in automobiles, electrical/electronic parts,
household appliances and furniture because of their good mechanical
properties, heat resistance, impact resistance and chemical
resistance and because they may be conveniently and flexibly molded
into a variety of articles of varying degrees of complexity and
intricacy.
[0005] U.S. Pat. No. 4,255,219 discloses a thermoplastic sheet
material useful in forming composites. The disclosed thermoplastic
sheet material is made of polyamide 6 and a dibasic carboxylic acid
or anhydride or esters thereof and at least one reinforcing mat of
long glass fibers encased within said layer.
[0006] For making integrated composite structures and to increase
the performance of polymers, it is often desired to "overmold" one
or more parts made of a polymer onto a portion or all of the
surfaces of a composite structure so as to surround or encapsulate
said surfaces. Overmolding involves shaping, e.g. by injection
molding, a second polymer part directly onto at least a portion of
one or more surfaces of the composite structure, to form a two-part
composite structure, wherein the two parts are adhered one to the
other at least at one interface. The polymer compositions used to
impregnate the fibrous material (i.e. the matrix polymer
composition) and the polymer compositions used to overmold the
impregnated fibrous material (i.e. the overmolding polymer
composition) are desired to have good adhesion one to the other,
extremely good dimensional stability, and to retain their
mechanical properties under adverse conditions, including thermal
cycling, so that the composite structure is protected under
operating conditions and thus has an increased lifetime.
[0007] Unfortunately, conventional thermoplastic polyamide resin
compositions that are used to impregnate one or more fibrous layers
and to overmold the one or more impregnated fibrous layers may show
poor adhesion between the overmolded polymer and the surface of the
component comprising the fibrous material, i.e. the composite
structure. The poor adhesion may result in the formation of cracks
at the interface of the overmolded composite structures leading to
reduced mechanical properties, premature aging and problems related
to delamination and deterioration of the article with use and
time
In such case of weak adhesion, the interface between the composite
structure and the overmolding resin will break first, rendering the
overmolded composite structure weaker than either of its
components. Therefore, high adhesion strength between the
components is highly desirable. However, once the bonding strength
is high enough that the interface can sustain the applied load
without being the first to break, yet higher mechanical performance
of the structure is highly desirable as is needed for the most
highly demanding applications. Lower mechanical performance in
these most demanding applications may impair the durability and
safety of the article upon use and time. Flexural strength, i.e.
the maximum flexural stress sustained by the test specimen during a
bending test, is commonly used as an indication of a material's
ability to bear (or to sustain, or to support) load when flexed.
When overmolding a resin composition onto at least a portion of a
composite structure, high mechanical performance such as flexural
strength of the structure is desired beyond that realized by good
bonding strength between the composite structure and the
overmolding resin.
[0008] There is a need for an overmolded polyamide composite
structure that exhibits good mechanical properties, especially
flexural strength and having at least a portion of its surface
allowing a good adhesion between its surface and an overmolding
resin comprising a polyamide resin.
SUMMARY OF THE INVENTION
[0009] Described herein is an overmolded composite structure
comprising: i) a first component having a surface, which surface
has at least a portion made of a surface resin composition, and
comprising a fibrous material selected from non-woven structures,
textiles, fibrous battings and combinations thereof, said fibrous
material being impregnated with a matrix resin composition, ii) a
second component comprising an overmolding resin composition,
wherein said second component is adhered to said first component
over at least a portion of the surface of said first component, and
wherein the matrix resin composition and the surface resin
composition and optionally the overmolding resin composition are
identical or different and are selected from polyamide compositions
comprising a blend of (A) one or more fully aliphatic polyamides
selected from group (I) polyamides preferably having a melting
point of less than 280.degree. C., and (B) one or more semiaromatic
polyamides selected from group (II) polyamides having a melting
point of at least 280.degree. C.
[0010] Further described herein is a process for making the
overmolded composite structure described above. The process for
making the overmolding composite structure described above
comprises a step of overmolding a second component comprising an
overmolding resin composition on the first component described
above.
DETAILED DESCRIPTION
[0011] The overmolded composite structure according to the present
invention has improved flexural strength and allows a good adhesion
when a part made of an overmolding resin composition comprising a
thermoplastic polyamide is adhered onto at least a portion of the
surface of the composite structure. A good flexural strength of the
overmolded composite structure and a good adhesion between the
composite structure and the overmolding resin leads to structures
exhibiting good resistance to deterioration or delamination of the
structure with use and time.
[0012] Several patents and publications are cited in this
description. The entire disclosure of each of these patents and
publications is incorporated herein by reference.
[0013] As used herein, the term "a" refers to one as well as to at
least one and is not an article that necessarily limits its
referent noun to the singular.
[0014] As used herein, the terms "about" and "at or about" are
intended to mean that the amount or value in question may be the
value designated or some other value about the same. The phrase is
intended to convey that similar values promote equivalent results
or effects according to the invention.
[0015] As used herein, the term "melting point" in reference to a
polyamide refers to the melting point of the pure resin as
determined with differential scanning calorimetry (DSC) at a scan
rate of 10.degree. C./min in the first heating scan, wherein the
melting point is taken at the maximum of the endothermic peak. In
customary measurements of melting behavior of blends of polymers,
more than one heating scans may be performed on a single specimen,
and the second and/or later scans may show a different melting
behavior from the first scan. This different melting behavior may
be observed as a shift in temperature of the maximum of the
endothermic peak and/or as a broadening of the melting peak with
possibly more than one peaks, which may be an effect of possible
transamidation in the case of more than one polyamides. However,
when selecting polyamides for Group I or for Group II polyamides in
the scope of the current invention, always the peak of the melting
endotherm of the first heating scan of the single polyamide is
used. As used herein, a scan rate is an increase of temperature per
unit time. Sufficient energy must be supplied to maintain a
constant scan rate of 10.degree. C./min until a temperature of at
least 30.degree. C. and preferably at least 50.degree. C. above the
melting point is reached.
[0016] The present invention relates to overmolded composite
structures and processes to make them. The overmolded composite
structure according to the present invention comprises at least two
components, i.e. a first component and a second component. The
first component consists of a composite structure having a surface,
which surface has at least a portion made of a surface resin
composition, and comprises a fibrous material selected from
non-woven structures, textiles, fibrous battings and combinations
thereof, said fibrous material being impregnated with a matrix
resin composition.
[0017] The overmolded composite structure may comprise more than
one first components, i.e. it may comprise more than one composite
structures and may comprise more than one second components.
[0018] The second component is adhered to the first component over
at least a portion of the surface of said first component, the
portion of the surface being made of the surface resin composition
described herein. The first component may be fully or partially
encapsulated by the second component, or the second component may
be adhered to only a portion of the surface of the first
component.
[0019] As used herein, the term "a fibrous material being
impregnated with a matrix resin composition" means that the matrix
resin composition encapsulates and embeds the fibrous material so
as to form an interpenetrating network of fibrous material
substantially surrounded by the matrix resin composition. For
purposes herein, the term "fiber" refers to a macroscopically
homogeneous body having a high ratio of length to width across its
cross-sectional area perpendicular to its length. The fiber cross
section can be any shape, but is typically round. The fibrous
material may be in any suitable form known to those skilled in the
art and is preferably selected from non-woven structures, textiles,
fibrous battings and combinations thereof. Non-woven structures can
be selected from random fiber orientation or aligned fibrous
structures. Examples of random fiber orientation include without
limitation chopped and continuous material which can be in the form
of a mat, a needled mat or a felt. Examples of aligned fibrous
structures include without limitation unidirectional fiber strands,
bidirectional strands, multidirectional strands, multi-axial
textiles. Textiles can be selected from woven forms, knits, braids
and combinations thereof. The fibrous material can be continuous or
discontinuous in form.
[0020] Depending on the end-use application of the overmolded
composite structure and the required mechanical properties, more
than one fibrous materials can be used, either by using several
same fibrous materials or a combination of different fibrous
materials, i.e. the first component described herein may comprise
one or more fibrous materials. An example of a combination of
different fibrous materials is a combination comprising a non-woven
structure such as for example a planar random mat which is placed
as a central layer and one or more woven continuous fibrous
materials that are placed as outside layers. Such a combination
allows an improvement of the processing and thereof of the
homogeneity of the first component thus leading to improved
mechanical properties. The fibrous material may be made of any
suitable material or a mixture of materials provided that the
material or the mixture of materials withstand the processing
conditions used during impregnation by the matrix resin composition
and the surface resin composition.
[0021] Preferably, the fibrous material comprises glass fibers,
carbon fibers, aramid fibers, graphite fibers, metal fibers,
ceramic fibers, natural fibers or mixtures thereof; more
preferably, the fibrous material comprises glass fibers, carbon
fibers, aramid fibers, natural fibers or mixtures thereof; and
still more preferably, the fibrous material comprises glass fibers,
carbon fibers and aramid fibers or mixture mixtures thereof. By
natural fiber, it is meant any of material of plant origin or of
animal origin. When used, the natural fibers are preferably derived
from vegetable sources such as for example from seed hair (e.g.
cotton), stem plants (e.g. hemp, flax, bamboo; both bast and core
fibers), leaf plants (e.g. sisal and abaca), agricultural fibers
(e.g., cereal straw, corn cobs, rice hulls and coconut hair) or
lignocellulosic fiber (e.g. wood, wood fibers, wood flour, paper
and wood-related materials). As mentioned above, more than one
fibrous materials can be used. A combination of fibrous materials
made of different fibers can be used such as for example a
composite structure comprising one or more central layers made of
glass fibers or natural fibers and one or more surface layers made
of carbon fibers or glass fibers. Preferably, the fibrous material
is selected from woven structures, non-woven structures or
combinations thereof, wherein said structures are made of glass
fibers and wherein the glass fibers are E-glass filaments with a
diameter between 8 and 30 microns and preferably with a diameter
between 10 to 24 microns.
[0022] The fibrous material may further contain a thermoplastic
material and the materials described above, for example the fibrous
material may be in the form of commingled or co-woven yarns or a
fibrous material impregnated with a powder made of a thermoplastic
material that is suited to subsequent processing into woven or
non-woven forms, or a mixture for use as a uni-directional material
or a fibrous material impregnated with oligomers that will
polymerize in situ during impregnation. Preferably, the ratio
between the fibrous material and the polymer materials in the first
component. i.e. the fibrous material in combination with the matrix
resin composition and the surface resin composition, is at least 30
volume percent fibrous material and more preferably between 40 and
60 volume percent fibrous material, the percentage being a
volume-percentage based on the total volume of the first
component.
[0023] The matrix resin composition of the first component is made
of a thermoplastic resin that is compatible with the surface resin
composition. The matrix resin composition and the surface resin
composition are selected from polyamide compositions comprising a
blend of (A) one or more group (I) polyamides defined as fully
aliphatic polyamides, preferably fully aliphatic polyamides having
a melting point of less than 280.degree. C. and (B) one or more
polyamides selected from group (II) polyamides defined as
semi-aromatic polyamides having a melting point of at least
280.degree. C. The matrix resin composition and the surface resin
composition may be identical or different. When the surface resin
composition and the matrix resin composition are different, it
means that the component (A), i.e) the one or more group (I) fully
aliphatic polyamides, and/or the component (B), i.e. the one or
more semi-aromatic polyamides selected from group (II) polyamide,
are not the same and/or that the amounts of component (A) and/or
(B) are different in the surface resin composition and the matrix
resin composition.
[0024] The overmolding resin composition can be any polyamide
composition. It is preferred that the overmolding resin composition
is selected from the polyamide compositions comprising a blend of
(A) one or more polyamides selected from group (I) polyamides and
(B) one or more polyamides selected from group (II) polyamides
described herein and may be identical or different from the surface
resin composition and/or the matrix resin composition.
[0025] When the overmolding resin composition is selected from the
polyamide compositions comprising a blend of (A) one or more
polyamides selected from group (I) polyamides and (B) one or more
polyamides selected from group (II) polyamides described herein,
and the matrix resin composition, the overmolding resin composition
and the surface resin composition are different, it means that the
component (A), i.e. one or more polyamides selected from group (I)
polyamides, and/or the component (B), i.e. one or more polyamides
selected from group (II) polyamides, are not the same and/or that
the amounts of component (A) and (B) are different in the matrix
resin composition, the overmolding resin composition and the
surface resin composition.
[0026] Polyamides are condensation products of one or more
dicarboxylic acids and one or more diamines, and/or one or more
aminocarboxylic acids, and/or ring-opening polymerization products
of one or more cyclic lactams. Polyamides may be fully aliphatic or
semi-aromatic and are described hereafter.
[0027] The term "semi-aromatic" describes polyamides that comprise
at least some monomers containing aromatic groups, in comparison
with "fully aliphatic" polyamide which describes polyamides
comprising aliphatic carboxylic acid monomer(s) and aliphatic
diamine monomer(s). The one or more semi-aromatic polyamides (B)
may be derived from one or more aliphatic carboxylic acid
components and aromatic diamine components such as for example
m-xylylenediamine and p-xylylenediamine, it may be derived from one
or more aromatic carboxylic acid components, such as terephthallic
acid, and one or more aliphatic diamine components, it may be
derived from mixtures of aromatic and aliphatic dicarboxylic acid
components and mixtures of aromatic and aliphatic diamine
components, it may be derived from mixtures of aromatic and
aliphatic carboxylic acids and aliphatic diamines or aromatic
diamines, it may be derived from aromatic or aliphatic carboxylic
acids with mixtures of aliphatic and aromatic diamines.
[0028] Preferably, the one or more semi-aromatic polyamides (B) are
formed from one or more aromatic carboxylic acid components and one
or more diamine components. The one or more aromatic carboxylic
acids can be terephthalic acid or mixtures of terephthalic acid and
one or more other carboxylic acids, like isophthalic acid,
substituted phthalic acid such as for example 2-methylterephthalic
acid and unsubstituted or substituted isomers of
naphthalenedicarboxylic acid, wherein the carboxylic acid component
contains at least 55 mole-% of terephthalic acid (the mole-% being
based on the carboxylic acid mixture). Preferably, the one or more
aromatic carboxylic acids are selected from terephthalic acid,
isophthalic acid and mixtures thereof and more preferably, the one
or more carboxylic acids are mixtures of terephthalic acid and
isophthalic acid, wherein the mixture contains at least 55 mole-%
of terephthalic acid. More preferably, the one or more carboxylic
acids is 100% terephthalic acid. Furthermore, the one or more
carboxylic acids can be mixed with one or more aliphatic carboxylic
acids, like adipic acid; pimelic acid; suberic acid; azelaic acid;
sebacic acid and dodecanedioic acid, adipic acid being preferred.
More preferably the mixture of terephthalic acid and adipic acid
comprised in the one or more carboxylic acids mixtures of the one
or more semi-aromatic polyamide (B) contains at least 55 mole-% of
terephthalic acid. The one or more semi-aromatic polyamides (B)
described herein comprises one or more diamines that can be chosen
among diamines having four or more carbon atoms, including, but not
limited to tetramethylene diamine, hexamethylene diamine,
octamethylene diamine, decamethylene diamine,
2-methylpentamethylene diamine, 2-ethyltetramethylene diamine,
2-methyloctamethylene diamine; trimethylhexamethylene diamine,
bis(p-aminocyclohexyl)methane; and/or mixtures thereof. Preferably,
the one or more diamines of the one or more semi-aromatic
polyamides (B) described herein are selected from hexamethylene
diamine, 2-methyl pentamethylene diamine and mixtures thereof, and
more preferably the one or more diamines of the one or more
semi-aromatic polyamides (B) are selected from hexamethylene
diamine and mixtures of hexamethylene diamine and 2-methyl
pentamethylene diamine wherein the mixture contains at least 50
mole-% of hexamethylene diamine (the mole-% being based on the
diamines mixture). Examples of semi-aromatic polyamides (B) useful
in the polyamide composition described herein are commercially
available under the trademark Zytel.RTM. HTN from E. I. du Pont de
Nemours and Company, Wilmington, Del.
[0029] The one or more fully aliphatic polyamides (A) are formed
from aliphatic and alicyclic monomers such as diamines,
dicarboxylic acids, lactams, aminocarboxylic acids, and their
reactive equivalents. A suitable aminocarboxylic acid is
11-aminododecanoic acid. Suitable lactams include caprolactam and
laurolactam. In the context of this invention, the term "fully
aliphatic polyamide" also refers to copolymers derived from two or
more such monomers and blends of two or more fully aliphatic
polyamides. Linear, branched, and cyclic monomers may be used.
Carboxylic acid monomers comprised in the fully aliphatic
polyamides are aliphatic carboxylic acids, such as for example
adipic acid (C6), pimelic acid (C7), suberic acid (C8), azelaic
acid (C9), sebacic acid (C10), dodecanedioic acid (C12) and
tetradecanedioic acid (C14). Preferably, the aliphatic dicarboxylic
acids of the one or more fully aliphatic polyamides (A) are
selected from adipic acid and dodecanedioic acid. The one or more
fully aliphatic polyamides (A) described herein comprise an
aliphatic diamine as previously described. Preferably, the one or
more diamine monomers of the one or more fully aliphatic polyamide
copolymer (A) according to the present invention are selected from
tetramethylene diamine and hexamethylene diamine. Suitable examples
fully aliphatic polyamides include polyamide 6; polyamide 6,6;
polyamide 4,6; polyamide 6,10; polyamide 6,12; polyamide 6,14;
polyamide 6,13; polyamide 6,15; polyamide 6,16; polyamide 11;
polyamide 12; polyamide 9,10; polyamide 9,12; polyamide 9,13;
polyamide 9,14; polyamide 9,15; polyamide 6,16; polyamide 9,36;
polyamide 10,10; polyamide 10,12; polyamide 10,13; polyamide 10,14;
polyamide 12,10; polyamide 12,12; polyamide 12,13; polyamide 12,14.
Preferred examples of fully aliphatic polyamides (A) useful in the
polyamide composition of the present invention are
poly(hexamethylene adipamide) (polyamide 66, PA66, also called
nylon 66), poly(hexamethylene dodecanoamide) (polyamide 612, PA612,
also called nylon 612), poly(tetramethylene hexanediamide)
(polyamide 46, PA46) and are commercially available.
[0030] Preferred group (I) Polyamides having a melting point of
less than 280.degree. C., preferably of less than 280.degree. C.
comprise a fully aliphatic polyamide selected from the group
consisting of, poly(.epsilon.-caprolactam) (PA 6), and
poly(hexamethylene hexanediamide) (PA 66), poly(pentamethylene
decanediamide) (PA510), poly(pentamethylene dodecanediamide)
(PA512), poly(.epsilon.-caprolactam/hexamethylene hexanediamide)
(PA6/66), poly(.epsilon.-caprolactam/hexamethylene decanediamide)
(PA6/610), poly(.epsilon.-caprolactam/hexamethylene
dodecanediamide) (PA6/612), poly(hexamethylene tridecanediamide)
(PA613), poly(hexamethylene pentadecanediamide) (PA615),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene decanediamide) (PA6/66/610),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene dodecanediamide) (PA6/66/612),
poly(.epsilon.-caprolactam/hexamethylene
hexanediamide/hexamethylene decanediamide/hexamethylene
dodecanediamide) (PA6/66/610/612), poly(2-methylpentamethylene
hexanediamide/hexamethylene hexanediamide/) (PA D6/66),
poly(decamethylene decanediamide) (PA1010), poly(decamethylene
dodecanediamide) (PA1012), poly(11-aminoundecanamide) (PA11),
poly(12-aminododecanamide) (PA12), PA6,12, PA12,12, and their
copolymers and combinations.
[0031] Preferred group (II) polyamides having a melting point of at
least 280.degree. C., comprise a semiaromatic polyamide selected
from the group poly(.epsilon.-caprolactam/tetramethylene
terephthalamide) (PA6/4T), poly(.epsilon.-caprolactam/hexamethylene
terephthalamide) (PA6/6T), poly(.epsilon.-caprolactam/decamethylene
terephthalamide) (PA6/10T),
poly(.epsilon.-caprolactam/dodecamethylene terephthalamide)
(PA6/12T), poly(hexamethylene decanediamide/hexamethylene
terephthalamide) (PA610/6T), poly(hexamethylene
dodecanediamide/hexamethylene terephthalamide) (PA612/6T),
poly(hexamethylene tetradecanediamide/hexamethylene
terephthalamide) (PA614/6T),
poly(.epsilon.-caprolactam/hexamethylene
isophthalamide/hexamethylene terephthalamide) (PA6/6I/6T),
poly(2-methylpentamethylene hexanediamide/hexamethylene
hexanediamide/hexamethylene terephthamide) (PA D6/66/6T),
poly(hexamethylene terephthamide/2-methylpentamethylene
terephthamide) (PA 6TDT), poly(hexamethylene
hexanediamide/hexamethylene terephthamide (PA66/6T),
poly(hexamethylene terephthamide/hexamethylene isophthamide
(PA6T/61), poly(hexamethylene hexanediamide/hexamethylene
terephthamide/hexamethylene isophthamide (PA66/6T/6I),
poly(decamethylene decanediamide/decamethylene terephthalamide)
(PA1010/10T) poly(decamethylene decanediamide/dodecamethylene
decanediamide/decamethylene terephthalamide/dodecamethylene
terephthalamide (PA1010/1210/10T/12T),
poly(11-aminoundecanamide/tetramethylene terephthalamide)
(PA11/4T), poly(11-aminoundecanamide/hexamethylene terephthalamide)
(PA11/6T), poly(11-aminoundecanamide/decamethylene terephthalamide)
(PA11/10T), poly(11-aminoundecanamide/dodecamethylene
terephthalamide) (PA11/12T),
poly(12-aminododecanamide/tetramethylene terephthalamide)
(PA12/4T), poly(12-aminododecanamide/hexamethylene terephthalamide)
(PA12/6T), poly(12-aminododecanamide/decamethylene terephthalamide)
(PA12/10T) poly(dodecamethylene dodecanediamide) (PA1212), and
poly(dodecamethylene dodecanediamide/dodecamethylene
dodecanediamide/dodecamethylene terephthalamide)) (PA1212/12T), and
their copolymers and combinations.
[0032] The matrix and the surface polyamide resin composition
described herein comprises a blend of (A) the one or more group (I)
polyamides and (B) one or more polyamides selected from group (II)
polyamides wherein the one or more group (I) polyamides are
preferably selected from the group consisting of PA6, PA46 and PA66
and wherein the one or more polyamides selected from group (II)
polyamides are selected from the group consisting of PA66/6T,
PA6TDT and PA6T/6I and their combinations and copolymers.
[0033] Preferably, the polyamide composition described herein
comprises a blend of (A) the one or more group (I) polyamides and
(B) one or more polyamides selected from group (II) polyamides in a
weight ratio (A:B) from about 99:1 to about 5:95, more preferably
from about 97:3 to about 50:50 and still more preferably from about
95:5 to about 65:35.
[0034] The overmolded composite structure comprises a second
component comprising an overmolding resin composition. The second
component is adhered to the first component described above over at
least a portion of the surface of the first component. The
overmolding resin composition can be any polyamide, or is
preferably selected from the polyamide compositions described
above, i.e. polyamide compositions comprising a blend of (A) one or
more polyamides selected from group (I) polyamides and (B) one or
more polyamides selected from group (II) polyamides (B) as
described for the surface resin composition.
[0035] The surface resin composition described herein and/or the
matrix resin composition and/or the overmolding resin composition
may further comprise one or more impact modifiers, one or more heat
stabilizers, one or more oxidative stabilizers, one or more
ultraviolet light stabilizers, one or more flame retardant agents
or mixtures thereof.
[0036] The surface resin composition described herein and/or the
matrix resin composition and/or the overmolding resin composition
may further comprise one or more reinforcing agents such as glass
fibers, glass flakes, carbon fibers, carbon nanotubes, mica,
wollastonite, calcium carbonate, talc, calcined clay, kaolin,
magnesium sulfate, magnesium silicate, boron nitride, barium
sulfate, titanium dioxide, sodium aluminum carbonate, barium
ferrite, and potassium titanate. When present, the one or more
reinforcing agents are present in an amount from at or about 1 to
at or about 60 wt-%, preferably from at or about 1 to at or about
40 wt-%, or more preferably from at or about 1 to at or about 35
wt-%, the weight percentages being based on the total weight of the
surface resin composition or the matrix resin composition, as the
case may be.
[0037] As mentioned above, the matrix resin composition and the
surface resin composition may be identical or different. With the
aim of increasing the impregnation rate of the fibrous material,
the melt viscosity of the compositions may be reduced and
especially the melt viscosity of the matrix resin composition.
[0038] The surface resin composition described herein and/or the
matrix resin composition and/or the overmolding resin composition
may further comprise modifiers and other ingredients, including,
without limitation, flow enhancing additives, lubricants,
antistatic agents, coloring agents (including dyes, pigments,
carbon black, and the like), nucleating agents, crystallization
promoting agents and other processing aids known in the polymer
compounding art.
[0039] Fillers, modifiers and other ingredients described above may
be present in the composition in amounts and in forms well known in
the art, including in the form of so-called nano-materials where at
least one of the dimensions of the particles is in the range of 1
to 1000 nm.
[0040] Preferably, the surface resin compositions and the matrix
resin compositions and the overmolding resin composition are
melt-mixed blends, wherein all of the polymeric components are
well-dispersed within each other and all of the non-polymeric
ingredients are well-dispersed in and bound by the polymer matrix,
such that the blend forms a unified whole. Any melt-mixing method
may be used to combine the polymeric components and non-polymeric
ingredients of the present invention. For example, the polymeric
components and non-polymeric ingredients may be added to a melt
mixer, such as, for example, a single or twin-screw extruder; a
blender; a single or twin-screw kneader; or a Banbury mixer, either
all at once through a single step addition, or in a stepwise
fashion, and then melt-mixed. When adding the polymeric components
and non-polymeric ingredients in a stepwise fashion, part of the
polymeric components and/or non-polymeric ingredients are first
added and melt-mixed with the remaining polymeric components and
non-polymeric ingredients being subsequently added and further
melt-mixed until a well-mixed composition is obtained.
[0041] The overmolded composite structure according to the present
invention may be manufactured by a process comprising a step of
overmolding the first component described above with the
overmolding resin composition. By "overmolding", it is meant that a
second component comprising the overmolding resin composition
described herein is molded or extruded onto at least one portion of
the surface of the first component, which surface is made of a
surface resin composition.
[0042] The overmolding process includes a process whereby the
second component is molded in a mold already containing the first
component, the latter having been manufactured beforehand as
described hereafter, so that the first and second components are
adhered to each other over at least a portion of the surface of the
first component. The first component is positioned in a mold having
a cavity defining the outer surface of the final overmolded
composite structure. The overmolding resin composition may be
overmolded on one side or on both sides of the first component and
it may fully or partially encapsulate the first component. After
having positioned the first component in mold (optionally after
preheating and performing the first component), the overmolding
resin composition is then introduced in a molten form. The first
component and the second component are adhered together by
overmolding. The at least two parts are preferably adhered together
by injection or compression molding as an overmolding step, and
more preferably by injection molding.
[0043] Depending on the end-use application, the first component
according to the present invention may have any shape. In a
preferred embodiment, the first component according to the present
invention is in the form of a sheet structure. The first component
may be flexible, in which case it can be rolled.
[0044] The first component can be made by a process that comprises
a step of impregnating the fibrous material with the matrix resin
composition, wherein at least a portion of the surface of the first
component, i.e. the composite structure, is made of the surface
resin composition. Preferably, the fibrous material is impregnated
with the matrix resin by thermopressing. During thermopressing, the
fibrous material, the matrix resin composition and the surface
resin composition undergo heat and pressure in order to allow the
resin compositions to melt and penetrate through the fibrous
material and, therefore, to impregnate said fibrous material.
[0045] Typically, thermopressing is made at a pressure between 2
and 100 bars and more preferably between 10 and 40 bars and a
temperature which is above the melting point of the matrix resin
composition and the surface resin composition, preferably at least
about 20.degree. C. above the melting point to enable a proper
impregnation. Heating may be done by a variety of means, including
contact heating, radiant gas heating, infra red heating, convection
or forced convection air heating, induction heating, microwave
heating or combinations thereof.
[0046] The impregnation pressure can be applied by a static process
or by a continuous process (also known as dynamic process), a
continuous process being preferred for reasons of speed. Examples
of impregnation processes include without limitation vacuum
molding, in-mold coating, cross-die extrusion, pultrusion, wire
coating type processes, lamination, stamping, diaphragm forming or
press-molding, lamination being preferred. During lamination, heat
and pressure are applied to the fibrous material, the matrix resin
composition and the surface resin composition through opposing
pressured rollers or belts in a heating zone, preferably followed
by the continued application of pressure in a cooling zone to
finalize consolidation and cool the impregnated fibrous material by
pressurized means. Examples of lamination techniques include
without limitation calendering, flatbed lamination and double-belt
press lamination. When lamination is used as the impregnating
process, preferably a double-belt press is used for lamination.
[0047] Should the matrix resin composition and the surface resin
composition be different, the surface resin composition always
faces the environment of the first component so as to be accessible
when the overmolding resin composition is applied onto the first
component.
[0048] The matrix resin composition and the surface resin
composition are applied to the fibrous material by conventional
means such as for example powder coating, film lamination,
extrusion coating or a combination of two or more thereof, provided
that the surface resin composition is applied on at least a portion
of the surface of the composite structure, which surface is exposed
to the environment of the first component.
[0049] During a powder coating process, a polymer powder which has
been obtained by conventional grinding methods is applied to the
fibrous material. The powder may be applied onto the fibrous
material by scattering, sprinkling, spraying, thermal or flame
spraying, or fluidized bed coating methods. Optionally, the powder
coating process may further comprise a step which consists in a
post sintering step of the powder on the fibrous material. The
matrix resin composition and the surface resin composition are
applied to the fibrous material such that at least a portion of the
surface of the first component is made of the surface resin
composition. Subsequently, thermopressing is performed on the
powder coated fibrous material, with an optional preheating of the
powder coated fibrous material outside of the pressurized zone.
[0050] During film lamination, one or more films made of the matrix
resin composition and one or more films made of the surface resin
composition which have been obtained by conventional extrusion
methods known in the art such as for example blow film extrusion,
cast film extrusion and cast sheet extrusion are applied to the
fibrous material, e.g. by layering. Subsequently, thermopressing is
performed on the assembly comprising the one or more films made of
the matrix resin composition and the one or more films made of the
surface resin composition and the one or more fibrous materials. In
the resulting first component, the films melt and penetrate around
the fibrous material as a polymer continuum surrounding the fibrous
material.
[0051] During extrusion coating, pellets and/or granulates made of
the matrix resin composition and pellets and/or granulates made of
the surface resin composition are melted and extruded through one
or more flat dies so as to form one or more melt curtains which are
then applied onto the fibrous material by laying down the one or
more melt curtains. Subsequently, thermopressing is performed on
the assembly comprising the matrix resin composition, the surface
resin composition and the one or more fibrous materials.
[0052] In some situations it may be desired to preheat the first
component at a temperature close to but below the melt temperature
of the matrix resin composition prior to the overmolding step so as
to improve the adhesion between the surface of the first component
and the overmolding resin and then to rapidly transfer the heated
composite structure for overmolding; such a step can be improved or
even eliminated by using the overmolding resin composition and the
surface resin composition. Due to the high adhesion and high bond
strength between the overmolding resin and the surface resin
composition of the overmolded composite structure according to the
present invention, the need for a preheating step is strongly
reduced or even eliminated. Should a preheating step be used, the
transfer time may not be as critical as for conventional composite
structures, meaning that the transfer time may be increased thereby
increasing the processing window and reducing molding equipment and
automation costs. Such a preheating step may be done by a variety
of means, including contact heating, radiant gas heating, infra red
heating, convection or forced convection air heating, induction
heating, microwave heating or combinations thereof.
[0053] Depending on the end-use application, the first component
may be shaped into a desired geometry or configuration, or used in
sheet form prior to the step of overmolding the overmolding resin
composition. The first component may be flexible, in which case it
can be rolled.
[0054] The process for making a shaped first component further
comprises a step of shaping the first component, said step arising
after the impregnating step. The step of shaping the first
component may be done by compression molding, stamping or any
technique using heat and/or pressure, compression molding and
stamping being preferred. Preferably, pressure is applied by using
a hydraulic molding press. During compression molding or stamping,
the first component is preheated to a temperature above the melt
temperature of the surface resin composition and preferably above
the melt temperature of the matrix resin composition by heated
means and is transferred to a forming or shaping means such as a
molding press containing a mold having a cavity of the shape of the
final desired geometry whereby it is shaped into a desired
configuration and is thereafter removed from the press or the mold
after cooling to a temperature below the melt temperature of the
surface resin composition and preferably below the melt temperature
of the matrix resin composition. With the aim of further improving
the adhesion between the overmolding resin and the surface resin
composition, the surface of the first component may be a textured
surface so as to increase the relative surface available for
overmolding, such textured surface may be obtained during the step
of shaping by using a press or a mold having for example porosities
or indentations on its surface.
[0055] Alternatively, a one step process comprising the steps of
shaping and overmolding the first component in a single molding
station may be used. This one step process avoids the step of
compression molding or stamping the first component in a mold or a
press, avoids the optional preheating step and the transfer of the
preheated first component to the molding station. During this one
step process, the first component, i.e. the composite structure, is
heated outside, adjacent to or within the molding station, to a
temperature at which the first component is conformable or shapable
during the overmolding step. In such a one step process, the
molding station comprises a mold having a cavity of the shape of
the final desired geometry. The shape of the first component is
thereby obtained during overmolding.
[0056] The overmolded composite structures according to the present
invention may be used in a wide variety of applications such as for
example as components for automobiles, trucks, commercial
airplanes, aerospace, rail, household appliances, computer
hardware, hand held devices, recreation and sports, structural
component for machines, structural components for buildings,
structural components for photovoltaic equipments or structural
components for mechanical devices.
Examples of automotive applications include without limitation
seating components and seating frames, engine cover brackets,
engine cradles, suspension arms and cradles, spare tire wells,
chassis reinforcement, floor pans, front-end modules, steering
column frames, instrument panels, door systems, body panels (such
as horizontal body panels and door panels), tailgates, hardtop
frame structures, convertible top frame structures, roofing
structures, engine covers, housings for transmission and power
delivery components, oil pans, airbag housing canisters, automotive
interior impact structures, engine support brackets, cross car
beams, bumper beams, pedestrian safety beams, firewalls, rear
parcel shelves, cross vehicle bulkheads, pressure vessels such as
refrigerant bottles and fire extinguishers and truck compressed air
brake system vessels, hybrid internal combustion/electric or
electric vehicle battery trays, automotive suspension wishbone and
control arms, suspension stabilizer links, leaf springs, vehicle
wheels, recreational vehicle and motorcycle swing arms, fenders,
roofing frames and tank flaps.
[0057] Examples of household appliances include without limitation
washers, dryers, refrigerators, air conditioning and heating.
Examples of recreation and sports include without limitation
inline-skate components, baseball bats, hockey sticks, ski and
snowboard bindings, rucksack backs and frames, and bicycle frames.
Examples of structural components for machines include
electrical/electronic parts such as for example housings for hand
held electronic devices, computers.
EXAMPLES
[0058] The following materials were used for preparing the
composites structures according to the present invention and
comparative examples.
Materials
[0059] The following materials were used for preparing examples
(abbreviated as "E" in the table) of overmolded composites
structures according to the present invention and comparative
examples (abbreviated as "C" in the table) of composite
structures.
[0060] Polyamide 1 (PA1): a group II polyamide made of terephtalic
acid and 1,6-hexamethylenediamine (HMD) and
2-methylpentamethylenediamine (MPMD) (HMD:MPMD=50:50). PA1 has a
melting point of about 297.degree. C. to about 303.degree. C. This
semi-aromatic polyamide is called PA6TDT and is commercially
available from E. I. du Pont de Nemours and Company, Wilmington,
Del.
Polyamide 2 (PA2): a group I polyamide made of adipic acid and
1,6-hexamethylenediamine with a weight average molecular weight of
around 32000 Daltons. PA2 has a melting point of about 260.degree.
C. to about 265.degree. C. This polyamide is called PA6,6 and is
commercially available, for example, from E. I. du Pont de Nemours
and Company. Overmolding resin: a composition comprising a group II
polyamide (PA1) made of terephtalic acid and
1,6-hexamethylenediamine (HMD) and 2-methylpentamethylenediamine
(MPMD) (HMD:MPMD=50:50), and 50% glass fibers by weight of the
total resin composition; the overmolding resin is commercially
available from E. I. du Pont de Nemours and Company.
Preparation of Films
[0061] The resin compositions used in the Example (abbreviated as
"E" in Table 1), and Comparative Examples (abbreviated as "C" in
Table 1) were prepared by melting or melt-blending the ingredients
in a twin-screw extruder. Upon exiting the extruder, the
compositions listed in Table 1 were cast into films by exiting the
extruder through an adaptor and a film die at about 310.degree. C.
and cast onto a casting drum oil-heated at 150.degree. C., then
drawn in air and wound around a core at room temperature. The
matrix and surface resin compositions were made into about 150
micron thick films. The thickness of the films was controlled by
the rate of drawing.
Preparation of the Composite Structures
[0062] The composite structures used for preparing the overmolded
composite structures E1, C1, and C2 were made by laminating
multiple layers of film of compositions shown in Table 1, and woven
continuous glass fiber textile (prepared from E-glass fibers having
a diameter of 17 microns, sized with 0.4% of a silane-based sizing
agent and a nominal roving tex of 1200 g/km that have been woven
into a 2/2 twill (balanced weave) with an areal weight of 600
g/m.sup.2). The lamination sequence for the composite structures
used in E1, and C2 was as follows: 4 layers of film of surface
resin composition, one layer of woven continuous glass fiber
textile, 6 layers of film of matrix resin composition, one layer of
woven continuous glass fiber textile, 4 layers of film of surface
resin composition. The lamination sequence for the composite
structure used in C1 was as follows: 2 layers of film of surface
resin composition, 2 layers of film of matrix resin composition,
one layer of woven continuous glass fiber textile, 6 layers of film
of matrix resin composition, one layer of woven continuous glass
fiber textile, 2 layers of film of matrix resin composition, 2
layers of film of surface resin composition.
[0063] The composite structures were compression molded by a Dake
Press (Grand Haven, Mich.) Model 44-225, Pressure range 0-25K, with
an 8 inch platten. A 6.times.6'' specimen of film and glass textile
layers as described above was placed in the mold and heated to a
temperature of about 340.degree. C., held at the temperature for 2
minutes without pressure, then pressed at the 340.degree. C.
temperature with the following pressures: about 6 bar for about 2
minutes, then with about 22 bar pressure for about 2 additional
minutes, and then with about 45 bar pressure for about 2 additional
minutes; it was subsequently cooled to ambient temperature. The
composite structures had an overall thickness of about 1.5 mm.
Preparation of the Overmolded Composite Structures
[0064] The overmolded composite structures listed in Table 1 were
made by over injection molding about 1.65 mm of the overmolding
resin composition onto the composite structures obtained as
described above. The overall thickness of the overmoded composite
structure was about 3.15 mm. The composite structure was cut into
3.times.5'' (about 76 mm.times.127 mm) specimens and placed into a
heating chamber (a Hotpack oven Model 273601) at 150.degree. C. for
about 10 minutes. The composite structure was then transferred
manually into a mold cavity and was over injection molded with the
overmolding resin by a molding machine (made by Nissei Corp., Model
FN4000, 1752 KN, 148 cc (6 oz.)). The mold was electric heated at
150.degree. C. and fitted with a 1/8''.times.3''.times.5'' plaque
cavity with a bar gate. The injection machine was set at
320.degree. C.
Flexural Strength of Overmolded Composite Structures of Table 1
[0065] The overmolded composite structures obtained as described
above were cut into 1/2'' (about 12.7 mm) by 3'' (about 76 mm) long
test specimens (bars) using a MK-377 Tile Saw with a diamond edged
blade and water as a lubricant. Flexural Strength was tested on the
test specimens via a 3-point bend test. The apparatus and geometry
were according to ISO method 178, bending the specimen with a 2.0''
support width with the loading edge at the center of the span. The
composite structure component of the overmolded specimen was on the
tensile side (outer span, down) resting on the two side supports
(at 2'' apart), while indenting with the single support (the load)
on the compression side (inner span, up) on the overmolding resin
component of the specimen. The tests were conducted with 1 KN load
at 2 mm/min until fracture. The results are shown in Table 1.
[0066] It is seen in Table 1 that the example E1 exhibits higher
flexural strength than comparative examples C1, C2, demonstrating
the higher flexural strength of the overmolded composite structure
comprising a composite structure of a Group I aliphatic polyamide
(polyamide A)+a group II semiaromatic polyamide (polyamide B) in
the matrix resin composition and in the surface resin
composition
TABLE-US-00001 TABLE 1 E1 C1 C2 First Component Matrix Resin
Composition PA1 90 100 100 PA2 10 Surface Resin Composition PA1 90
90 100 PA2 10 10 Second Component Overmolding resin PA1 + 50% PA1 +
50% PA1 + 50% glass fibers glass fibers glass fibers ISO-178 3
Point Flex Flexural Strength at 321 284 271 Break (Mpa), laminate
down (in tension)
* * * * *