U.S. patent application number 14/759427 was filed with the patent office on 2015-12-10 for an electrically insulating composite material and an electrical device comprising the same.
The applicant listed for this patent is ABB TECHNOLOGY LTD., Jiansheng CHEN, Yong FENG, Chau-Hon HO, Delun MENG, Jens ROCKS, Lars SCHMIDT, Zhaoxia SUN, Sufeng ZHANG. Invention is credited to JIANSHENG CHEN, YONG FENG, CHAU-HON HO, DELUN MENG, JENS ROCKS, LARS SCHMIDT, ZHAOXIA SUN, SUFENG ZHANG.
Application Number | 20150354144 14/759427 |
Document ID | / |
Family ID | 51427502 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150354144 |
Kind Code |
A1 |
CHEN; JIANSHENG ; et
al. |
December 10, 2015 |
AN ELECTRICALLY INSULATING COMPOSITE MATERIAL AND AN ELECTRICAL
DEVICE COMPRISING THE SAME
Abstract
Electrically, insulating composite material is obtained from the
form of a paper of a pressboard with an electrical device through
post-treating by electron beam irradiation treatment, gamma
irradiation treatment or x-ray irradiation treatment.
Inventors: |
CHEN; JIANSHENG; (BEIJING,
CN) ; HO; CHAU-HON; (STEIN, CH) ; ROCKS;
JENS; (FREIENBACH, CH) ; ZHANG; SUFENG;
(SHAANXI, CN) ; SCHMIDT; LARS; (OSKARSHAMN,
SE) ; FENG; YONG; (BEIJING, CN) ; MENG;
DELUN; (BEIJING, CN) ; SUN; ZHAOXIA; (SHAANXI,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CHEN; Jiansheng
HO; Chau-Hon
ROCKS; Jens
ZHANG; Sufeng
SCHMIDT; Lars
FENG; Yong
MENG; Delun
SUN; Zhaoxia
ABB TECHNOLOGY LTD. |
Switzerland
Switzerland
Oskarshamn
Beijing
Beijing
Xi'an, Shaanxi
Zurich |
|
US
CH
CH
US
SE
CN
CN
CN
CH |
|
|
Family ID: |
51427502 |
Appl. No.: |
14/759427 |
Filed: |
May 7, 2013 |
PCT Filed: |
May 7, 2013 |
PCT NO: |
PCT/CN2013/075262 |
371 Date: |
July 7, 2015 |
Current U.S.
Class: |
162/157.4 |
Current CPC
Class: |
H01F 27/32 20130101;
H01B 3/47 20130101; D21H 25/04 20130101; H01B 3/42 20130101; H01B
3/52 20130101; D21J 1/20 20130101 |
International
Class: |
D21J 1/20 20060101
D21J001/20 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2013 |
CN |
PCT/CN2013/072081 |
Claims
1. An electrical insulating composite material in the form of a
paper or a pressboard, wherein the electrically insulating
composite material is obtained through post-treating by irradiation
treatment.
2. The electrically insulating composite material of claim 1,
wherein the irradiation treatment for post-treating is electron
beam irradiation treatment, gamma irradiation treatment, x-ray
irradiation or combinations thereof.
3. The electrically insulating composite material of claim 2,
wherein the electron beam irradiation treatment, gamma irradiation
treatment and x-ray irradiation is under ambient air or with the
injection of inert gas.
4. The electrically insulating composite material of claim 2,
wherein the dose for the electron beam irradiation, gamma
irradiation or x-ray irradiation is from 30 kGy to 300 kGy.
5. The electrically insulating composite material of claim 1,
wherein the electrically insulating composite material is composed
of fiber and fibrid.
6. The electrically insulating composite material of claim 5,
wherein the said fiber comprises at least one of the following
fibers: polyethylene terephthalate fiber, polyethylene naphthalate
fiber, polytrimethylene terephthalate fiber, polybutylene
terephthalate fiber, polyacrylonitrile fiber, poly (metaphenylene
isophthamide) fiber, poly(paraphenylene terephthalamide) fiber,
polysulfonamide fiber, polyphenylene sulphide fiber, polyphenylene
oxide fiber, polyethersulfone fiber, polyetheretherketone fiber,
polyetherimide fiber, and cellulose fiber.
7. The electrically insulating composite material of claim 5,
wherein the said fibrid comprises at least one of the following
fibrids: polyacrylonitrile fibrid, polyethylene terephthalate
fibrid, polyethylene naphthalate fibrid, polytrimethylene
terephthalate fibrid, polybutylene terephthalate fibrid, poly
(metaphenylene isophthamide) fibrid, and polysulfonamide
fibrid.
8. The electrically insulating composite material of claim 5,
wherein the fiber is present in an amount of 5 wt % to 95 wt % and
the fibrid is present in an amount of 5 wt % to 95 wt %, based on
the total weight of the electrically insulating composite
material.
9. An electrical device comprising the electrically insulating
composite material according to claim 1.
10. The electrical device of claim 9, wherein the said device is an
electrical transformer or an electrical motor.
11. The electrical device of claim wherein the electrically
insulating composite material is in the form of a spacer, barrier,
strip, a paper wrapped conductor or press ring for insulation.
12. The electrically insulating composite material of claim 2,
wherein the dose for the electron beam irradiation, gamma
irradiation or x-ray irradiation is from 50 kGy to 200 kGy.
13. A method of forming electrically insulating composite material,
comprising: mixing fibrids and fibers; pressing the mixed fibrids
and fibers into an electrically insulating composite material using
at least one of a paper press or a multi-daylight hot press; and
irradiating the electrically insulating composite material.
14. The method of claim 13, wherein pressing includes: heating the
mixed fibrids and fibers; cooling the heated mixed fibrids and
fibers; pressing the cooled mixed fibrids and fibers into the
electrically insulating composite material formed as
pressboard.
15. The method of claim 14, wherein irradiating includes:
irradiating by at least one of electron beam irradiation, gamma
radiation, or x-ray irradiation.
16. The method according to claim 13, wherein the irradiating
includes a dose from 30 kGy to 300 kGy.
17. The method according to claim 13, wherein the irradiating
includes a dose from 50 kGy to 200 kGy.
18. The method of claim 13, wherein the said fiber comprises at
least one of the following fibers: polyethylene terephthalate
fiber, polyethylene naphthalate fiber, polytrimethylene
terephthalate fiber, polybutylene terephthalate fiber,
polyacrylonitrile fiber, poly (metaphenylene isophthamide) fiber,
poly(paraphenylene terephthalamide) fiber, polysulfonamide fiber,
polyphenylene sulphide fiber, polyphenylene oxide fiber,
polyethersulfone fiber, polyetheretherketone fiber, polyetherimide
fiber, and cellulose fiber; and wherein the said fibrid comprises
at least one of the following fibrids: polyacrylonitrile fibrid,
polyethylene terephthalate fibrid, polyethylene naphthalate fibrid,
polytrimethylene terephthalate fibrid, polybutylene terephthalate
fibrid, poly (metaphenylene isophthamide) fibrid, and
polysulfonamide fibrid.
19. The method of claim 13, wherein the fiber is present in an
amount of 5 wt % to 95 wt % and the fibrid is present in an amount
of 5 wt % to 95 wt %, based on the total weight of the electrically
insulating composite material.
20. An electrically insulated composite material, comprising: fiber
comprises at least one of the following fibers: polyethylene
terephthalate fiber, polyethylene naphthalate fiber,
polytrimethylene terephthalate fiber, polybutylene terephthalate
fiber, polyacrylonitrile fiber, poly (metaphenylene isophthamide)
fiber, poly(paraphenylene terephthalamide) fiber, polysulfonamide
fiber, polyphenylene sulphide fiber, polyphenylene oxide fiber,
polyethersulfone fiber, polyetheretherketone fiber, polyetherimide
fiber, and cellulose fiber; fibrid comprises at least one of the
following fibrids: polyacrylonitrile fibrid, polyethylene
terephthalate fibrid, polyethylene naphthalate fibrid,
polytrimethylene terephthalate fibrid, polybutylene terephthalate
fibrid, poly (metaphenylene isophthamide) fibrid, and
polysulfonamide fibrid; and wherein the fiber is present in an
amount of 5 wt % to 95 wt % and the fibrid is present in an amount
of 5 wt % to 95 wt %, based on the total weight of the electrically
insulating composite material.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electrically insulating
composite material in the form of a paper or a pressboard, wherein
the electrically insulating composite material is obtained through
post-treating by irradiation treatment.
BACKGROUND
[0002] Insulation of oil-filled distribution and power transformers
may be made from cellulose, polymer paper and pressboard. The
cellulose papers or pressboards are mainly used in transformers
with relatively lower thermal stability requirements, and polymer
papers or pressboards are mainly for transformers with relatively
higher thermal stability requirements. Nomex from Dupont and
Thermal shield from 3M are typical commercially available polymer
papers or pressboards. Generally speaking, cellulose papers or
pressboards are more extensively used than polymer ones. The major
reason is that the cost of cellulose paper and pressboard is much
lower than those made of polymer. However, the use of cellulose
papers or pressboards at high temperature is limited by the low
thermal stability of cellulosic materials. On the other hand, it is
unsatisfactory to use the polymer paper or pressboard due to its
relatively high cost. Furthermore, for some uses, it is necessary
that the paper or pressboard not only have a suitably high thermal
stability, but also possess enhanced mechanical property, so that
the paper or the pressboard can provide better electrical
insulation performance.
[0003] In the past, many attempts have been made to improve the
property of the papers or the pressboards and most of them are
focused on the selecting of different polymers and different
processing methods. Irradiation treatment, such as electron beam
irradiation treatment, gamma irradiation treatment and x-ray
irradiation treatment, is an effective method to increase the
crosslinking density of some polymer materials, thus enhance the
mechanical property of the polymers. Few works have been reported
related to irradiation treatment in the application of electrically
insulating paper or pressboard until now.
[0004] U.S. Pat. No. 6,824,728 B2 relates to a process for
crosslinking polyacrylate compositions, wherein, by selective
irradiation of the pressure-sensitive adhesive composition with
electron beams, the polymer is cured only in certain structures
and, as a result, structured pressure-sensitive adhesive
compositions can be prepared.
[0005] U.S. Pat. No. 3,707,692 discloses a method of increasing the
dimensional stability of cellulosic material by impregnating the
cellulose with a composition including a cellulose swelling agent
and a compound capable of crosslinking with the cellulose
molecules. The crosslinking takes place at elevated temperatures in
the absence of an acidic catalyst and the crosslinked cellulosic
materials are useful as insulators in electrical apparatus.
[0006] There is still a need to provide an electrically insulating
composite material in the form of a paper or a pressboard with
improved performance, such as higher thermal stability and better
mechanical property.
SUMMARY
[0007] According to the present invention, an electrically
insulating composite material in the form of a paper or a
pressboard is provided, wherein the electrically insulating
composite material is obtained through post-treating by irradiation
treatment.
[0008] One aspect of the present invention relates to an
irradiation treatment for post-treating, wherein the irradiation
treatment for post-treating is electron beam irradiation treatment,
gamma irradiation treatment, x-ray irradiation treatment or
combinations thereof. According to one embodiment of the present
invention, the electron beam irradiation, gamma irradiation or
x-ray irradiation is under ambient air atmosphere or with the
injection of inert gas. According to another embodiment of the
present invention, the dose for the electron beam irradiation,
gamma irradiation or x-ray irradiation is from 30 kGy to 300 kGy
and preferably 50 kGy to 200 kGy.
[0009] According to another aspect of the present invention, it
relates to an electrically insulating composite material, wherein
the composite material is composed of fiber and fibrid. According
to one embodiment of the present invention, the said fiber
comprises at least one of the following fibers: polyethylene
terephthalate fiber, polyethylene naphthalate fiber,
polytrimethylene terephthalate fiber, polybutylene terephthalate
fiber, polyacrylonitrile fiber, poly (metaphenylene isophthamide)
fiber, poly(paraphenylene terephthalamide) fiber, polysulfonamide
fiber, polyphenylene sulphide fiber, polyphenylene oxide fiber,
polyethersulfone fiber, polyetheretherketone fiber, polyetherimide
fiber, and cellulose fiber. According to another embodiment of the
present invention, the said fibrid comprises at least one of the
following fibrids: polyacrylonitrile fibrid, polyethylene
terephthalate fibrid, polyethylene naphthalate fibrid,
polytrimethylene terephthalate fibrid, polybutylene terephthalate
fibrid, poly (metaphenylene isophthamide) fibrid, and
polysulfonamide fibrid.
[0010] According to one embodiment of the present invention, the
fiber in the electrically insulating composite material is present
in an amount of 5 wt % to 95 wt % and the fibrid is present in an
amount of 5 wt % to 95 wt %, base on the total weight of the
electrically insulating composite material.
[0011] According to one embodiment of the present invention, the
electrically insulating composite material is in the form of a
paper or a pressboard.
[0012] Another aspect of the present invention relates to an
electrical device comprising the above electrically insulating
composite material, such as an electrical transformer or an
electrical motor.
[0013] The inventors have found unexpectedly that, by post-treated
with electron beam irradiation gamma irradiation or x-ray
irradiation, it is possible to provide an electrical device,
especially high voltage insulating device, with improved mechanical
property and thermal stability. Specifically, the electrically
insulation composite material displays significant different
performance after such irradiation treatment. For example, for the
electrically insulation composite material composed by
polyacrylonitrile fibrid and polyethylene terephthalate fiber
(Example 1), the 5% decomposition temperature is increased from
323.degree. C. to 339.degree. C., the tensile strength is increased
from about 100 MPa to about 115 MPa and the compressibility is
lowered from 3.5% to 3.1% after electron beam irradiation
treatment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Embodiments will be described, by way of example, with
reference to the accompanying drawings, in which:
[0015] FIG. 1 is a schematic flow chart of an embodiment of a
method according to the present invention.
DETAILED DESCRIPTION
[0016] Embodiments will now be described more fully hereinafter
with reference to the accompanying drawings, in which certain
embodiments are shown. However, other embodiments in many different
forms are possible within the scope of the present disclosure.
Rather, the following embodiments are provided by way of example so
that this disclosure will be thorough and complete, and will fully
convey the scope of the disclosure to those skilled in the art.
[0017] According to the present invention, an electrically
insulating composite material in the form of a paper or a
pressboard is provided, wherein the electrically insulating
composite material is obtained through post-treating by irradiation
treatment.
[0018] Preferably, the pressboard according to the present
invention has a thickness of higher than 0.9 mm. More preferably,
the thickness of the pressboard is 1-12 mm, and most preferably 1-8
mm. A paper of the present invention has a thickness of less than
0.9 mm, preferably less than 0.8 mm, and more preferably is between
0.05 to 0.5 mm.
[0019] An important factor to impact the mechanical property and
thermal stability of the polymer material is the crosslinking
degree. Crosslinking is the term used to denote the reaction in
which a large number of linear or branched macromolecules, which
initially are still soluble, become linked together to form
three-dimensional polymeric networks (crosslinked polymers, network
polymers) which are insoluble and now only swellable. Crosslinking
is possible as a result of the formation of covalent and
noncovalent (coordinative, ionic physical, saltlike) bonds.
Crosslinking can be carried out during the actual construction of
the macromolecules and/or by reaction on performed (pre)polymers
which generally contain functional groups.
[0020] Generally speaking, the crosslinking of the polymers can be
initiated by heat or irradiation. Due to the relatively poor
thermal stability of some electrically insulation composite
material, irradiation treatment should be a better method to
conduct the crosslinking. Irradiation treatments usually include
ultraviolet light (UV) irradiation, electron beam (EB) irradiation,
gamma irradiation and x-ray irradiation treatment. In particularly,
UV crosslinking is a very simple process requiring only a simple
coating used with a few low-pressure Hg lamps. UV crosslinking
functions very well for polymer compositions with low film
thickness. The EB, gamma irradiation and x-ray irradiation
technologies are more expensive in terms of apparatus but tolerate
the crosslinking of greater film thicknesses and faster web
speeds.
[0021] One aspect of the present invention relates to an
irradiation treatment for post-treating, wherein the irradiation
treatment for post-treating is electron beam irradiation treatment,
gamma irradiation treatment, x-ray irradiation treatment or
combinations thereof. According to one embodiment of the present
invention, the electron beam irradiation, gamma irradiation or
x-ray irradiation is under ambient air atmosphere or with the
injection of inert gas.
[0022] It is believed that the post-treating by electron beam
irradiation, gamma irradiation or x-ray irradiation could increases
the crosslinking density in the electrically insulation composite
material and also could induce the material degradation, with
appropriate irradiation post treatment to balance the crosslinking
reaction and degradation reaction, we can enhance the thermal
stability and mechanical property of the electrically insulation
composite material. According to the present invention, the thermal
stability of the electrically insulation composite material is
evaluated by 5% decomposition temperature, which is known to the
skilled in the art and is commonly used in this field. For example,
for the electrically insulation composite material composed by
polyacrylonitrile fibrid and polyethylene terephthalate fiber
(Example 1), the volume increase of the pressboard after EB
irradiation is only 35%, much lower than the corresponding
pressboard without EB irradiation (50%), indicating the increased
crosslinking density. Furthermore, after such EB irradiation
treatment, the 5% decomposition temperature of the pressboard is
increased from 323.degree. C. to 339.degree. C., the tensile
strength of the pressboard is increased from about 100 MPa to about
115 MPa and the compressibility of the pressboard is lowered from
3.5% to 3.1%, implying the improved mechanical property.
[0023] According to another aspect of the present invention, it is
related to an electrically insulating composite material, wherein
the composite material is composed of fiber and fibrid. The fiber
may be a polymer fiber. The polymer fiber for paper and pressboard
preparation is a short fiber which is generally made of normal
continuous fiber with regular diameter. The short polymer fiber
could be treated by further beating to develop their sheetmaking
properties. The said fibrid may be a polymer fibrid. The polymer
fibrid, a type of fibrous particle used for binding, is with
irregular shape and made from polymer solution.
[0024] According to one embodiment of the present invention, the
said fiber comprises at least one of the following fibers:
polyethylene terephthalate fiber, polyethylene naphthalate fiber,
polytrimethylene terephthalate fiber, polybutylene terephthalate
fiber, polyacrylonitrile fiber, poly (metaphenylene isophthamide)
fiber, poly(paraphenylene terephthalamide) fiber, polysulfonamide
fiber, polyphenylene sulphide fiber, polyphenylene oxide fiber,
polyethersulfone fiber, polyetheretherketone fiber, polyetherimide
fiber, cellulose fiber or the combinations thereof.
[0025] According to one embodiment of the present invention, the
said fibrid comprises at least one of the following fibrids:
polyacrylonitrile fibrid, polyethylene terephthalate fibrid,
polyethylene naphthalate fibrid, polytrimethylene terephthalate
fibrid, polybutylene terephthalate fibrid, poly (metaphenylene
isophthamide) fibrid, polysulfonamide fibrid, or combinations
thereof.
[0026] According to one embodiment of the present invention, the
fiber in the electrically insulating composite material is present
in an amount of 5 wt % to 95 wt % and preferably 20 wt % to 60 wt
%. According to another embodiment of the present invention, the
fibrid is present in an amount of 5 wt % to 95 wt %, and preferably
40 wt % to 80 wt %, based on the total weight of the electrically
insulating composite material.
[0027] After extensive research, the present inventors have found
that specific dose under a temperature within a certain range
achieves a great balance in producing an electrically insulating
composite material without destruction degradation to the final
material, which possesses unexpected comprehensive properties, such
as mechanical strength and thermal stability. According to one
embodiment of the present invention, the suitable dose for the
electron beam irradiation, gamma irradiation and x-ray irradiation
is from 30 kGy to 300 kGy. In order to achieve better crosslinking,
the dose can be further optimized. According to some embodiments of
the present invention, the dose for EB, gamma irradiation or x-ray
irradiation is preferred to be 50 kGy to 200 kGy. Particularly, for
the pressboard made from polyethylene terephthalate fibrid and
polyethylene terephthalate fiber, the preferred dose for EB
irradiation is about 200 kGy (Example 2). More particularly, for
the pressboard made from polyacrylonitrile fibrid and cellulose
fiber, the preferred dose for EB irradiation is about 100 kGy
(Example 4).
[0028] The composite material is electrically insulating and is
suitable for use as insulation material in an electrical device.
The composite material may be, for example, used as electrical
insulation in an electrical device, such as in a power transformer,
whereby the composite material may be a high voltage insulation
material.
[0029] As mentioned above, the electrically insulating composite
material may have especially beneficial electrically insulating
properties in an oily environment. Thus, the electrically
insulating composite material may be at least partly soaked in
oil.
[0030] The present invention further provides an electrical device
comprising the electrically insulating composite material according
to the present invention. The electrical device may be any
electrical device which comprises electrical insulation, e.g. an
electrical transformer or a conductor of electricity or an
electrical motor, which may especially benefit from the composite
material, such as with improved mechanical properties, less time is
needed for insulation height adjustment during transformer
fabrication and the total insulation thickness can be reduced.
Especially, the electrical device according to the present
invention is an electrical transformer.
[0031] The electrically insulating composite material may be in the
form of a paper, spacer, barrier, strip or press ring for
insulation in or of an electrical device, such as a conductor of
electricity, an electrical transformer. The electrically insulating
composite material has electrically insulating properties which may
be useful in any electrical device, such as for insulating an
electricity conduit, but the electrically insulating composite
material may be especially advantageous in an oily environment,
such as in an electrical transformer. Specifically, the
electrically insulating composite material may be used for making
electrically insulating spacers in a transformer winding.
[0032] An improved electrical device is obtained by using the
electrically insulating composite material in accordance with the
present invention. In particular, the electrically insulation
composite material displays improved mechanical properties, such as
an improved compressibility.
[0033] FIG. 1 is a schematic flow chart of an embodiment of a
method 1 which is the-state-of-the-art method for insulation paper
and pressboard preparation. Fibrids are provided, see 2, and fibers
are also provided, see 3. The fibrids and fibers are then mixed
with each other, see 4. A paper press, multi-daylight hot press of
the like, is then used for pressing the mixture to provide a
pressboard or a presspaper or the like of the composite material
discussed herein, see 5. The pressing also comprises heating, see
6, and drying the mixture, see 7, as well as pressing the mixture
to the pressboard, see 8. The pressboard was then cooled, see 9.
The cooled pressboard may then be cut into desired insulation
parts, for example, for use in a transformer or any other
electrical device. For instance, a spacer, barrier, strip or press
ring for insulation of an electrical transformer can be produced
from the composite material from this invention.
EXAMPLES
[0034] An electrically insulation composite material in the form of
a paper or a pressboard, which is first produced according to
the-state-of-the-art method as shown in FIG. 1, is obtained through
post-treating by irradiation treatment. The properties of the
electrically insulation composite material are tested according to
the IEC (International Electrotechnical Commission) standard
60641-2.
Example 1
[0035] A pressboard was made according to the process in FIG. 1.
The solid materials used in the making of this pressboard were 60
weight percent of polyacrylonitrile fibrid (Shanghai Labon
Technical Fiber Co., Ltd) and 40 weight percent of polyethylene
terephthalate fiber (Woongjin Chemical Co., Ltd). This pressboard
had a basic weight of 2420 g/m.sup.2, a thickness of 2 mm and a
density of 1.21 g/cm.sup.3.
[0036] An electron beam source of 1.5 MeV was used for the
post-treating of the pressboard and the irradiation was carried out
at room temperature under ambient air. The pressboard samples were
placed in an open steel tray on a conveyer band which passed the
electron beam scan horn with a speed of 3 m/min and in 6 turns. In
each turn the pressboard samples were irradiated with 25 kGy and
total dose of 150 kGy was applied on the samples.
[0037] Swelling measurements for the comparison of the network
density in pressboard were performed on the basis of these
described in "Cross-Linking-Effect on Physical Properties of
Polymers" (Nielsen, L. E., Journal of Macromolecular Science, Part
C, 1969, 3, 69-103). In this test, the volume change of the
pressboard is measured after immersing in a solvent at a certain
temperature for a certain duration.
[0038] For each swelling measurement, 3 specimens per pressboard
with and without irradiation treatment of approximately 25*15*2 mm
were cut and measured with an accuracy of 0.05 mm. The specimens
were immersed in 100 mL of m-cresol at 70.degree. C. for 24 hours.
The specimens were removed from the solvent thereafter, shortly
cooled to room temperature and the dimensions were remeasured. The
increase in volume after swelling of the pressboard without
irradiation treatment is about 50% and that of the pressboard with
irradiation treatment is about 35%.
[0039] The 5% decomposition temperature of the untreated pressboard
determined by thermogravimetry analyzer (TGA) in air atmosphere is
about 323.degree. C. and that of the treated pressboard is
339.degree. C. The tensile strength of the untreated pressboard is
about 100 MPa and that of the treated pressboard is about 115 MPa;
the compressibility of the untreated pressboard is about 3.5% that
of the treated pressboard is about 3.1%.
[0040] Another test was carried out as described in Example except
that the pressboard was irradiated with an irradiation dose of 300
kGy in air, the result showed that the properties of the treated
pressboard were quite similar to those of the untreated pressboard.
It is assumed that the higher irradiation dose in air could induce
the higher degree of degradation of pressboard.
[0041] Another test was carried out as describe in Example except
that the pressboard was irradiated with an irradiation dose of 150
kGy in nitrogen atmosphere, the result showed that the properties
of the treated pressboard is a little better than the properties of
the treated pressboard with an irradiation dose of 150 kGy in air,
we assume that the nitrogen atmosphere can avoid some competing
oxidation processes during the irradiation treatment which is
beneficial to the final material properties.
Example 2
[0042] A pressboard was made according to the process in FIG. 1.
The solid materials used in the making of this pressboard were 60
weight percent of polyethylene terephthalate fibrid (Shanghai Labon
Technical Fiber Co., Ltd) and 40 weight percent of polyethylene
terephthalate fiber. This pressboard had a basic weight of 1160
g/m.sup.2, a thickness of 1 mm and a density of 1.16
g/cm.sup.3.
[0043] An electron beam source of 1.5 MeV was used for the
post-treating of the pressboard and the irradiation was carried out
at room temperature under ambient air. The pressboard samples were
place in an open steel tray on a conveyer band which passed the
electron beam scan horn with a speed of 3 m/min and in 8 turns. In
each turn the pressboard samples were irradiated with 25 kGy and
total dose of 200 kGy was applied on the samples.
[0044] For each swelling measurement, 3 specimens per pressboard
with and without irradiation treatment of approximately 25*15*1 mm
were cut and measured with an accuracy of 0.05 mm. The specimens
were immersed in 100 mL of m-cresol at 70.degree. C. for 24 hours.
The specimens were removed from the solvent thereafter, shortly
cooled to room temperature and the dimensions were remeasured. The
increase in volume after swelling of the pressboard without
irradiation treatment is about 48% and that of the pressboard with
irradiation treatment is about 32%. When the specimens were
immersed in 100 mL of m-cresol at 90.degree. C. for 14 hours, the
increase in volume after swelling of the pressboard without
irradiation treatment is about 86% and that of the pressboard with
irradiation treatment is about 54%.
[0045] The 5% decomposition temperature of the untreated pressboard
determined by thermogravimetry analyzer (TGA) in air atmosphere is
about 360.degree. C. and that of the treated pressboard is
377.degree. C. The tensile strength of the untreated pressboard is
about 80 MPa and that of the treated pressboard is about 90 MPa;
the compressibility of the untreated pressboard is about 3.4% that
of the treated pressboard is about 3.0%.
Example 3
[0046] A pressboard was made according to the process in FIG. 1.
The solid materials used in the making of this pressboard were 60
weight percent of polyacrylonitrile fibrid, 10 weight percent of
poly (metaphenylene isophthamide) fiber (Yantai Tayho Advanced
Materials Co., Ltd) and 30 weight of polyethylene naphthalate
fiber. This pressboard had a basic weight of 1120 g/m.sup.2, a
thickness of 1 mm and a density of 1.12 g/cm.sup.3.
[0047] A gamma irradiation source of 1.5 MeV was used for the
post-treating of the pressboard and the irradiation was carried out
at room temperature under ambient air. The pressboard samples were
placed in an open steel tray on a conveyer band which passed the
gamma irradiation scan horn with a speed of 2 m/min and in 8 turns.
In each turn the pressboard samples were irradiated with 25 kGy and
total dose of 200 kGy was applied on the samples.
[0048] For each swelling measurement, 3 specimens per pressboard
with and without irradiation treatment of approximately 25*15*1 mm
were cut and measured with an accuracy of 0.05 mm. The specimens
were immersed in 100 mL of m-cresol at 70.degree. C. for 24 hours.
The specimens were removed from the solvent thereafter, shortly
cooled to room temperature and the dimensions were remeasured. The
increase in volume after swelling of the pressboard without
irradiation treatment is about 60% and that of the pressboard with
irradiation treatment is about 50%.
[0049] The 5% decomposition temperature of the untreated pressboard
determined by thermogravimetry analyzer (TGA) in air atmosphere is
about 370.degree. C. and that of the treated pressboard is
380.degree. C. The tensile strength of the untreated pressboard is
about 100 MPa and that of the treated pressboard is about 110 MPa;
the compressibility of the untreated pressboard is about 3.2% that
of the treated pressboard is about 2.9%.
Example 4
[0050] A pressboard was made according to the process in FIG. 1.
The solid materials used in the making of this pressboard were 20
weight percent of polyacrylonitrile fibrid and 80 weight percent of
cellulose fiber. This pressboard had a basic weight of 1140
g/m.sup.2, a thickness of 1 mm and a density of 1.14
g/cm.sup.3.
[0051] An electron beam source of 1.5 MeV was used for the
post-treating of the pressboard and the irradiation was carried out
at room temperature under ambient air. The pressboard samples were
placed in an open steel tray on a conveyer band which passed the
electron beam scan horn with a speed of 3 m/min and in 4 turns. In
each turn the pressboard samples were irradiated with 25 kGy and
total dose of 100 kGy was applied on the samples.
[0052] The 5% decomposition temperature of the untreated pressboard
determined by thermogravimetry analyzer (TGA) in air atmosphere is
about 316.degree. C. and that of the treated pressboard is
325.degree. C. The tensile strength of the untreated pressboard is
about 105 MPa and that of the treated pressboard is about 115 MPa;
the compressibility of the untreated pressboard is about 4.2% that
of the treated pressboard is about 3.9%.
* * * * *