U.S. patent application number 14/350794 was filed with the patent office on 2014-09-11 for distillate fuel with improved seal swell properties.
The applicant listed for this patent is Sasol Technology (Pty) Ltd.. Invention is credited to Christopher Woolard.
Application Number | 20140250772 14/350794 |
Document ID | / |
Family ID | 47505372 |
Filed Date | 2014-09-11 |
United States Patent
Application |
20140250772 |
Kind Code |
A1 |
Woolard; Christopher |
September 11, 2014 |
DISTILLATE FUEL WITH IMPROVED SEAL SWELL PROPERTIES
Abstract
The invention provides a distillate fuel blend with improved
seal swell properties comprising at least one highly paraffinic
distillate fuel fraction having a mass swelling ratio less than 9%
when measured according to ASTM D1414 or ASTM D471 at 50.degree. C.
and for 20 days when using an NBR (nitrile butadiene rubber) O-ring
with a hardness of 70 that has been de-plasticised; and about 0.5
volume percent to about 15 volume percent of at least one component
selected from a group of aromatic ethers wherein the blend exhibits
a mass swelling ratio of at least 10% when measured according to
ASTM D1414 or ASTM D471 at 50.degree. C. and for 20 days when using
an NBR (nitrile butadiene rubber) O-ring with a hardness of 70 that
has been de-plasticised. The invention extends to the use of an
aromatic ether fraction in a blend with a synthetic middle
distillate fraction for the purposes of achieving seal swell
characteristics more comparable with those characteristic of
crude-derived middle distillate fuel product.
Inventors: |
Woolard; Christopher; (Cape
Town, ZA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sasol Technology (Pty) Ltd. |
Johannesburg |
|
ZA |
|
|
Family ID: |
47505372 |
Appl. No.: |
14/350794 |
Filed: |
October 17, 2012 |
PCT Filed: |
October 17, 2012 |
PCT NO: |
PCT/ZA2012/000071 |
371 Date: |
April 9, 2014 |
Current U.S.
Class: |
44/448 |
Current CPC
Class: |
C10L 10/00 20130101;
C10L 1/04 20130101; C10L 2200/0492 20130101; C10L 2200/0438
20130101; C10L 2200/043 20130101; C10G 2/30 20130101; C10L 1/1852
20130101; C10G 2300/1022 20130101; C10G 2300/1096 20130101; C10G
2400/08 20130101; C10L 1/02 20130101; C10G 2300/1051 20130101 |
Class at
Publication: |
44/448 |
International
Class: |
C10L 10/00 20060101
C10L010/00; C10L 1/185 20060101 C10L001/185 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2011 |
ZA |
2011/07576 |
Claims
1-16. (canceled)
17. A distillate fuel blend with improved seal swell properties
comprising: at least one synthetic paraffinic middle distillate
fuel fraction derived from a Fischer-Tropsch process or a
biological source, the synthetic paraffinic middle distillate fuel
fraction having a mass swelling ratio less than 9% when measured
according to ASTM D1414 or ASTM D471 at 50.degree. C. and for 20
days when using a nitrile butadiene rubber O-ring with a hardness
of 70 that has been de-plasticised; and about 0.5 volume percent to
about 15 volume percent of at least one component selected from the
group consisting of aromatic ethers.
18. The distillate fuel blend of claim 17, wherein the synthetic
paraffinic middle distillate fuel fraction has a mass swelling
ratio less than 6.5% when measured according to ASTM D1414 or ASTM
D471 at 50.degree. C. and for 20 days when using a nitrile
butadiene rubber O-ring with a hardness of 70 that has been
de-plasticised.
19. The distillate fuel blend of claim 17, wherein the distillate
fuel blend comprises about 0.5 volume percent to about 10 volume
percent of at least one component selected from the group
consisting of aromatic ethers.
20. The distillate fuel blend of claim 17, wherein the distillate
fuel blend comprises about 0.5 volume percent to about 6 volume
percent of at least one component selected from the group
consisting of aromatic ethers.
21. The distillate fuel blend of claim 17, wherein the distillate
fuel blend has a total aromatic content of less than 8 mass %.
22. The distillate fuel blend of claim 17, having seal swell
characteristics comparable with those characteristic of
crude-derived middle distillate fuel products.
23. The distillate fuel blend of claim 22, wherein the synthetic
paraffinic middle distillate fuel fraction is highly
paraffinic.
24. The distillate fuel blend of claim 22, wherein the synthetic
paraffinic middle distillate fuel fraction is a jet fuel or a
kerosene fraction.
25. The distillate fuel blend of claim 22, wherein the synthetic
paraffinic middle distillate fuel fraction is derived or partly
derived from Fischer-Tropsch product.
26. The distillate fuel blend of claim 22, wherein an aromatic
ether fraction of the distillate fuel blend comprises a single
aromatic ether species.
27. The distillate fuel blend of claim 22, wherein an aromatic
ether fraction of the distillate fuel blend comprises a combination
of aromatic ether species.
28. The distillate fuel blend of claim 22, wherein an aromatic
ether fraction of the distillate fuel blend has a boiling point or
boiling point range that lies in a middle distillate boiling point
range.
Description
[0001] This invention is directed to a synthetic distillate fuel
blend which has improved seal swell characteristics.
BACKGROUND OF THE INVENTION
[0002] It is well known that synthetic middle distillate fuel
streams, such as Fischer Tropsch derived distillates, do not cause
the same degree of swelling of the traditional elastomeric
materials (such as nitrile O-rings) used in aircraft and other
vehicles as does crude-derived fuel. This has significant potential
to cause problems in situations where synthetic fuels would be
treated as a drop-in component (e.g. Fully Synthetic Jet Fuel
(FSJF). This is potentially far more problematic than where
synthetic fuels are blended with crude-derived fuels to provide a
Semi Synthetic Fuel (SSJF)). It has been further established that
this lack of swelling can be rectified through the addition of
various levels of aromatic species to the synthetic fuels. For
example, U.S. Pat. No. 7,608,181 teaches the use of
distillate-boiling alkylcycloparaffins and alkylaromatics in order
to achieve improved seal swell behaviour in highly paraffinic
Fischer Tropsch-derived distillate fuel.
[0003] Critically, these aromatic species require usage at levels
that are comparable to the lower levels of aromatic species
observed in crude-derived middle distillate fuel in order to
achieve an analogous effect. Aromatic species in fuels are not
themselves highly desirable from both an environmental and a
combustion perspective. Hence the addition of generic aromatic
species to synthetic middle distillate fuels may enable achieving
the desired seal swell, lubricity and density properties; but is
itself not inherently positive.
[0004] A means of achieving a synthetic middle distillate blend
with suitable properties such as seal swell behaviour, but with
reduced aromatic content is therefore much sought after.
SUMMARY OF THE INVENTION
[0005] According to a first aspect of the invention, there is
provided a distillate fuel blend with improved seal swell
properties comprising: [0006] a) at least one highly paraffinic
distillate fuel fraction having a mass swelling ratio less than 9%
when measured according to ASTM D1414 or ASTM D471 at 50.degree. C.
and for 20 days when using an NBR (nitrile butadiene rubber) O-ring
with a hardness of 70 that has been de-plasticised; and [0007] b)
about 0.5 volume percent to about 15 volume percent of at least one
component selected from a group of aromatic ethers wherein the
blend exhibits a mass swelling ratio of at least 10% when measured
according to ASTM D1414 or ASTM D471 at 50.degree. C. and for 20
days when using an NBR (nitrile butadiene rubber) O-ring with a
hardness of 70 that has been de-plasticised.
[0008] The highly paraffinic distillate may have a mass swelling
ratio less than 6.5% when measured according to ASTM D1414 or ASTM
D471 at 50.degree. C. and for 20 days when using an NBR (nitrile
butadiene rubber) O-ring with a hardness of 70 that has been
de-plasticised.
[0009] The distillate fuel blend may comprise about 0.5 volume
percent to about 10 volume percent of at least one component
selected from the group of aromatic ethers.
[0010] The distillate fuel blend may comprise about 0.5 volume
percent to about 8 volume percent of at least one component
selected from the group of aromatic ethers.
[0011] The distillate fuel blend may comprise about 0.5 volume
percent to about 6 volume percent of at least one component
selected from the group of aromatic ethers.
[0012] The distillate fuel blend may exhibit a mass swelling ratio
of at least 12% when measured according to ASTM D1414 or ASTM D471
at 50.degree. C. and for 20 days when using an NBR (nitrile
butadiene rubber) O-ring with a hardness of 70 that has been
de-plasticised.
[0013] The distillate fuel blend may exhibit a mass swelling ratio
of at least 14% when measured according to ASTM D1414 or ASTM D471
at 50.degree. C. and for 20 days when using an NBR (nitrile
butadiene rubber) O-ring with a hardness of 70 that has been
de-plasticised.
[0014] The distillate fuel blend may exhibit a mass swelling ratio
of at least 12% when measured according to ASTM D1414 or ASTM D471
at 23.degree. C. and for 20 days when using an NBR (nitrile
butadiene rubber) O-ring with a hardness of 70 that has been
de-plasticised.
[0015] The distillate fuel blend may exhibit a mass swelling ratio
of at least 10% when measured according to ASTM D1414 or ASTM D471
at 23.degree. C. and for 20 days, under switch loading conditions,
when using an NBR (nitrile butadiene rubber) O-ring with a hardness
of 70 that has been de-plasticised.
[0016] The distillate fuel blend may have a total aromatic content
of less than 8 mass %.
[0017] According to a second aspect of the invention, there is
provided the use of an aromatic ether fraction in a blend with a
synthetic middle distillate fraction for the purposes of achieving
seal swell characteristics more comparable with those
characteristic of crude-derived middle distillate fuel product.
[0018] The synthetic middle distillate fraction is highly
paraffinic.
[0019] The synthetic middle distillate fraction may be a jet fuel
or kerosene fraction.
[0020] The synthetic middle distillate fraction may be derived, or
partly derived from Fischer Tropsch product.
[0021] The aromatic ether fraction may comprise a single aromatic
ether species.
[0022] The aromatic ether fraction may comprise a combination of
aromatic ether species.
[0023] The aromatic ether fraction may comprise a range of aromatic
ether species such that the fraction does not have a single boiling
point, but rather is characterised by a boiling point range.
[0024] The aromatic ether fraction may have a boiling point or
boiling point range that lies in the middle distillate boiling
point range.
[0025] The aromatic ether fraction may have a boiling point or
boiling point range that lies in the kerosene boiling point
range.
[0026] The aromatic ether fraction may have a boiling point or
boiling point range that lies between 140.degree. C. and
320.degree. C. It may have a boiling point (or range) that lies
between 150.degree. and 320.degree. C. It may have a boiling point
(or range) that lies between 150.degree. and 280.degree. C.
[0027] In one embodiment, the aromatic ether fraction may be
comprised of an aromatic ring that is entirely comprised of carbon
atoms.
[0028] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a phenyl group.
[0029] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a benzyl group where R' is
either a methyl or an ethyl group.
[0030] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a phenyl group and an ether
species that has a benzyl group where R' is either a methyl or an
ethyl group.
BRIEF DESCRIPTION OF FIGURES
[0031] FIG. 1: The swelling behaviour of highly paraffinic Fischer
Tropsch-derived kerosene
[0032] FIG. 2: The swelling behaviour of as-received O-ring samples
exposed to blends of SPK with various aromatic additives
[0033] FIG. 3: The swelling behaviour of de-plasticised O-ring
samples in SPK +2%, 4% and 8% dibenzyl ether
[0034] FIG. 4.1: Switch loading experiment between Jet A-1 and SPK
conducted on de-plasticised O-rings. (The swelling curves for neat
Jet A-1 and SPK are provided for reference.)
[0035] FIG. 4.2: Switch loading experiment conducted on
de-plasticised samples with graphs of O-rings exposed to Jet A-1
and SPK+8% toluene. (The swelling curves for neat Jet A-1 and
SPK+8% toluene are provided for reference.)
[0036] FIG. 4.3: Switch loading experiment conducted on
de-plasticised samples with graphs of O-rings exposed to Jet A-1
and SPK+4% dibenzyl ether. (The swelling curves for neat Jet A-1
and SPK+4% dibenzyl ether are provided for reference.)
DETAILED DESCRIPTION OF THE INVENTION
Aromatic Ether Fraction
[0037] The species of this invention comprising the aromatic ether
fraction is defined as an ether moiety attached to an aromatic
ring. Examples of such suitable aromatic ethers include anisole,
benzyl methyl ether and dibenzyl ether.
[0038] The ether moiety may contain no carbon atoms connecting the
oxygen atom of the ether moiety to the aromatic ring (such as
anisole); or it may contain a single carbon atom or multiple carbon
atoms connecting the oxygen atom and aromatic ring (such as benzyl
methyl ester). The ether moiety can also function as a bridging
chain between multiple aromatic rings.
##STR00001##
[0039] The aromatic moiety may therefore be a phenyl group, where
the structure could be expressed in the general form as:
##STR00002##
where R can be an alkyl or aryl group;
[0040] Or the aromatic moiety may be a benzyl group, where the
structure could be expressed in the general form as:
##STR00003##
where R' can be an alkyl group and R'' can be an alkyl or aryl
group;
[0041] The aromatic ether fraction may have a boiling point or
boiling point range that lies between 140.degree. C. and
320.degree. C. It may have a boiling point (or range) that lies
between 150.degree. and 320.degree. C. It may have a boiling point
(or range) that lies between 150.degree. and 280.degree. C.
[0042] In one embodiment, the aromatic ether fraction may be
comprised of an aromatic ring that is entirely comprised of carbon
atoms.
[0043] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a phenyl group.
[0044] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a benzyl group where R.sup.1
is either a methyl or an ethyl group.
[0045] In one embodiment, the aromatic ether fraction may be
comprised of an ether species that has a phenyl group and an ether
species that has a benzyl group where R.sup.1 is either a methyl or
an ethyl group.
Paraffinic Fraction
[0046] The synthetic middle distillate fraction is highly
paraffinic. It can be derived from the Fischer Tropsch process (a
CTL, GTL or XTL process), or derived from biological sources--for
example, hydrogenated vegetable or animal oil.
[0047] The synthetic middle distillate fraction may be a kerosene
fraction.
[0048] Where it is derived from a Fischer Tropsch process, this
fraction can be defined as Synthetic Paraffinic Kerosene (SPK).
Table 1 illustrates the general properties of two SPK fuels
suitable for use in this invention compared to crude-derived
product Jet A-1. SPK denotes a paraffinic CTL kerosene; and SPK-g
denotes a paraffinic GTL kerosene.
TABLE-US-00001 TABLE 1 Properties of SPK fuels Property Limits Jet
A-1 SPK SPK-g Composition Aromatics, v % 8.0*-25** 19 1 0
n-Paraffins, m % -- 20 2 23 iso-Paraffins, -- 26 87 76 m %
cyclic-Paraffins, <15.sup.# 31 10 1 m % Volatility Density @
771-836 800 765 735 15.degree. C., kg/m.sup.3 Thermal Stability
Filter pressure 25 (max) 0 0 0 drop, mm Hg Tube deposit <3
.sup.$ <1(275.degree. C.) <1(325.degree. C.)
<1(325.degree. C.) rating *Minimum specification applicable to
SSJF and FSJF. There is no minumum specification for
petroleum-derived Jet A-1 **Maximum specification for Jet A-1, SSJF
and FSJF .sup.#Maximum specification applicable to FSJF. There is
no maximum specification for petroleum-derived Jet A-1 .sup.$
Temperature of tube deposit rating dependent on fuel, 275.degree.
C. for petroleum-derived, 325.degree. C. for synthetically
derived
Blending Process
[0049] The effects of various additives were investigated by making
solutions of the respective blending components in SPK. All
solution blends were prepared by volume according to standard
laboratory practice.
Swelling Characterisation Methods
[0050] 1. Method for the Determination of Mass Swelling Ratio (Q
%)
[0051] ASTM method D1414 (Standard Test Method for Rubber O-rings)
and D471 (Standard Test Method for Rubber Property-Effect of
Liquids) contain the base methods for the solution exposure
experiments.
[0052] The static gravimetric method was conducted as follows:
[0053] the initial mass of the samples was recorded [0054] the
samples were then placed in the specified solvent [0055] at
specified times the samples were removed from the solvent and
blotted dry before weighing [0056] finally the samples were
returned to the solvent.
[0057] The containers were placed inside a closed box in order to
eliminate any influence of light exposure. Although this is not
specified in the ASTM methods it was, however, deemed important for
the long exposure treatments, continuing for durations longer than
100 days. The procedure was continued until the samples had reached
equilibrium, i.e. until a change of mass was no longer observed.
From the data obtained the mass swelling ratio (Q %) was determined
as a function of time. Q % is given by the equation below.
Q % = 100 .times. M t - M o M o ##EQU00001## [0058] where: [0059]
M.sub.0 mass before swelling [0060] M.sub.t mass at time, t
[0061] For certain experiments the O-rings were removed from
solution after equilibrium had been reached and exposed to air for
1 day, allowing the bulk of the remaining fuel in the polymer to
evaporate. The sample was then placed in the vacuum oven at
50.degree. C. for 5 days. Final mass measurements after solvent
extraction where then made to allow the extent of mass loss due to
plasticiser extraction to be determined. [0062] 2. Method for the
Determination of Volume Swelling Ratio (%)
[0063] ASTM method D1414 (Standard Test Method for Rubber O-rings)
and D471 (Standard Test Method for Rubber Property-Effect of
Liquids) contain the base methods for the solution exposure
experiments.
[0064] In ASTM D1414, volume changes may be observed using a hand
micrometer of O-ring diameter according to which the
cross-sectional diameter is measured at four points equally
distributed around the circumference. This method was found to be
inaccurate; so optical microscopy was used.
[0065] A similar experimental procedure was used to that of
gravimetric method. However, the change in O-ring volume was
determined using an optical microscope at 40.times. (optical)
magnification. The average diameter of the O-rings were measured
from six points equally distributed around the sample by taking
images of the O-rings undergoing solution treatment. Each diameter
reading was determined using the circular measurement option of the
ShuttleRix.RTM. software. This allowed for the inside diameter
(i.d.) and outside diameter (o.d.) to be measured and thus the
thickness of the sample to be determined at one of the six
measuring points. The change in cross-sectional area can be used to
determine the change in volume of the sample using the
equation:
R % = 100 ( ( d f d o ) 3 - 1 ) ##EQU00002## [0066] where: [0067]
d.sub.o=initial cross-sectional diameter [0068]
d.sub.f=cross-sectional diameter at time, t [0069] 3. As-Received
and De-Plasticised O-rings
[0070] The nitrile butadiene rubber (NBR) O-rings used in this
study were supplied by Bearing Man Ltd (Johannesburg, South
Africa). These had an inside diameter of 20 mm, a 2.5 mm
cross-sectional diameter and a Shore-A hardness of approximately
70. Later measurements were performed on smaller O-rings of inside
diameter 4.2 mm and cross-sectional diameter 1.9 mm and Shore-A
hardness 70. These were also supplied by Bearing Man Ltd.
[0071] Extractable polymeric additives, such as plasticisers and
curatives complicate the interpretation of swelling data obtained
from as-received samples undergoing solution treatment, since the
measured data is the result of solvent entering the polymer and the
extraction of additives. It was found that solvents/fuel blends
that show seal swell potential will remove plasticisers from the
NBR O-rings. For this reason, O-ring conditioning with
CH.sub.2Cl.sub.2 was employed in certain circumstances to remove
plasticisers. After the conditioning process it was determined that
10.0%.+-.0.2% mass loss occurred which was attributed to
extractible additives in the O-ring samples under investigation.
This value was supported by TGA (Thermal Gravimetric Analysis)
results. (Note that this value is highly dependent on the polymeric
component being used.).
[0072] The method used for generating the deplasticised O-rings was
as follows:
[0073] 20 O-rings were placed in 800 mL of solvent
(CH.sub.2Cl.sub.2) for 3 days at a constant temperature of
23.degree. C. The solvent was then replaced with fresh supply and
samples were left for an additional 3 days. After the extraction of
plasticiser the solvent in the O-ring was evaporated off by
allowing the samples to air dry for 1 day, followed by vacuum
extraction at 50.degree. C. for 5 days at -0.80 bar.
[0074] The invention will now be illustrated by the following
non-limiting examples:
EXAMPLES
Example 1
Comparative Example Base Cases
[0075] As a base case, the swelling behaviour of two samples of
highly paraffinic Fischer Tropsch-derived kerosene was determined.
They are designated SPK (an FT coal-derived isomerised kerosene)
and SPK-g (an FT gas-derived kerosene that contains less isomerised
paraffin than does SPK (see Table 1)). FIG. 1 shows the swelling
behaviour of these samples over time, in tests conducted on
as-received NBR O-rings at 50.degree. C. The dramatic decrease in
seal swelling as a result of plasticiser loss with these samples is
easily observed.
[0076] Table 2 shows the swelling behaviour of blends of Jet A-1
and SPK (showing the effect of SSJF composition) in a series of
experiments using de-plasticised O-rings exposed to the blends at
50.degree. C. As more Jet A-1 is incorporated, the swelling
behaviour increases. Note that, whilst the volume change seems
positive for the pure SPK sample in this case, this measurement is
made after removal of the plasticiser (which reduces the volume by
12.5%), so the net change is actually negative.
TABLE-US-00002 TABLE 2 Swelling of de-plasticised O-rings exposed
to blends of Jet A-1 and SPK Volume change at Volume change at Mass
change at equilibrium (%) - equilibrium (%) - % Jet A-1 equilibrium
(%) large O-rings small O-rings 0 (neat SPK) 4.8 (0.1) 8.8 (0.3)
7.7 (0.9) 25 7.0 (0.1) 11.9 (0.3) 11.0 (0.6) 50 9.0 (0.0) 13.9
(0.3) 13.1 (0.4) 75 10.8 (0.1) 17.1 (0.1) 16.1 (0.5) 100 (neat 14.4
(0.1) 20.7 (0.2) 20.1 (0.6) Jet A-1) The values in brackets are the
standard deviations of the mean. The standard deviations for volume
changes of small O-rings are larger because the contribution of
flash to projected area is larger.
Example 2
[0077] A range of various aromatic additives (anisole, dibenzyl
ether, toluene and benzyl alcohol (designated BzOH) were tested in
blends with SPK on as-received NBR O-rings at 50.degree. C. in
order to ascertain their effect on seal swell. FIG. 2 shows the
swelling behaviour of O-rings exposed to these blends over time
under static conditions. A sample of SPK blended 50/50 with Jet A-1
representative of a commercially approved SSJF was also included
for comparison purposes. It is clear that the aromatic ether
samples are significantly more efficacious in achieving seal swell
than the other two aromatic species tested. It is also evident that
at an 8% additive level, both aromatic ether species provide seal
swell behaviour far in excess of what is observed for SSJF.
Example 3
Effect of Additive/Solvent Concentration on Swelling
[0078] A range of concentrations of dibenzyl ether additive in SPK
was tested on de-plasticised O-rings at 50.degree. C. in order to
ascertain the level of the blending component required to produce a
similar swell to that seen in samples exposed to Jet A-1. (The Jet
A-1 sample used in these experiments contained approximately 18%
aromatics.)
[0079] FIG. 3 shows the swelling of de-plasticised O-ring samples
in SPK+2%, 4% and 8% dibenzyl ether. Table 3 shows the key results
in tabulated form. The effect on mass swelling ratio at various
concentrations (as shown in FIG. 3) indicates that seal swell
levels comparable to those observed for Jet A-1 (the red dotted
line on the graph) can be easily achieved at levels of just 5.3
volume % dibenzyl ether.
TABLE-US-00003 TABLE 3 Key data showing impact of dibenzyl ether
additive levels on swelling Calculate average Average mass uptake
volume change at Solution at equilibrium (%) equilibrium (%)* Jet
A-1 14.4 (0.1) 20.7 SPK 4.8 (0.1) 8.9 SPK + 1% Dibenzyl ether 6.7
(0.1) 11.2 SPK + 2% Dibenzyl ether 8.5 (0.1) 13.4 SPK + 4% Dibenzyl
ether 12.2 (0.1) 17.9 SPK + 8% Dibenzyl ether 19.3 (0.1) 26.6** The
values in brackets are the standard deviations of the mean. N = 3
*includes the volume increase due to SPK component **Measured
change was 26.4
Example 4
Temperature Effects on Swelling
[0080] The effect of temperature on the seal swell ability of SPK
additised with two different types of aromatic species was
assessed. This experiment was of interest because of the
requirement that these additives be able to function effectively
across the temperature range of the operating environment where the
O-rings are to be used. The two blends were SPK+0.5 vol % benzyl
alcohol (BzOH) and SPK+8 vol % dibenzyl ether. These experiments
were performed on statically treated O-ring samples at temperatures
of 23.degree. C. and 50.degree. C. respectively. Swelling was
measured until an equilibrium state was reached
[0081] FIG. 4.1 shows the effect of temperature on the swelling of
O-rings exposed to SPK+0.5% BzOH (referred to as BzA in the
figure). It is clear that O-rings treated at 23.degree. C. reach a
greater equilibrium mass swelling ratio (which is in excess of the
samples exposed to Jet A-1) than do the rings treated at 50.degree.
C. FIG. 4.2 shows the effect of temperature on the swelling of
de-plasticised O-rings exposed to a blend of SPK+8% dibenzyl ether.
It is clear that, in the case of dibenzyl ether, the behaviour at
ambient and 50.degree. C. conditions was far more consistent than
was the case for benzyl alcohol.
Example 5
Switch Loading Experiment
[0082] An investigation was conducted into the swelling behaviour
that occurs when switching between petroleum-derived fuel and
synthetic fuels, known as switch loading. These experiments were
done in order to represent more realistic conditions that an O-ring
may face in service should the fuel chemistry be changed.
[0083] Initial switch loading experiments were run on statically
treated O-ring samples by switching solvents every 7 days from Jet
A-1 to SPK, and recording the mass changes. This was followed by
experiments using switching between Jet A-1 sample and blends of
SPK with one of two additive components--toluene (at 8 vol %) and
dibenzyl ether (at 4 vol %). The effect of switching fuel types was
hence monitored as Q % (mass swelling ratio) over time. These
experiments were performed using deplasticised O-rings and
conducted at room temperature. In all these switching experiments,
the samples were exposed to the Jet A-1 sample first.
[0084] FIG. 5.1 shows the experimental results of switching between
Jet A-1 and pure SPK. (The swelling curves for Jet A-1 and pure SPK
are included for comparison.) The swell is contained between upper
and lower limits defined by the swell behaviour in the respective
solvents when no switching occurs.
[0085] FIG. 5.2 shows the experimental results of switching between
Jet A-1 and a blend of SPK+8 vol% toluene. (As before, the swelling
curves for neat Jet A-1 and the SPK+8 vol % toluene blend are
included for comparison.) FIG. 5.3 shows the analogous experiment
switching between Jet A-1 and a blend of SPK+4 vol % dibenzyl
ether.
[0086] The blend of SPK+4 vol % dibenzyl ether shows far less
change during the switching experiment than does the blend of SPK+8
vol% toluene. At equilibrium, the swelling of the SPK+8 vol %
toluene blend is clearly less than that obtained for the SPK+4 vol
% dibenzyl ether blend.
Example 6
Impact of Various Additive Species on Seal Swell (Measured as
Volume % Change) at Higher Temperatures
[0087] For the purpose of further quantifying the effect on seal
swell of various classes of additive, SPK was blended with various
aromatic additives according to the concentrations described in
Table 4 below. These blends were then run on statically treated
O-ring samples. The swelling of de-plasticised O-rings was measured
at 50.degree. C. until an equilibrium state was reached. This
swelling was then characterised as a volume % change.
TABLE-US-00004 TABLE 4 Solvent properties, additive levels and
experimental results showing solvent effects at higher
temperatures. % Volume Swelling Boiling Concentration Mass swelling
change (at efficacy Solvent Formula point (.degree. C.) (v/v) ratio
at 50.degree. C. 50.degree. C.) (%) Jet Fuel product Jet A-1 100%
13.9 20.5% SPK 100% 6.0 9.1% Cycloparaffins Decalin
C.sub.10H.sub.18 187 8% in SPK 6.6 11.6% 0.17% Aromatics Benzene
C.sub.6H.sub.6 80 8% in SPK 11.1 16.8% 0.98% Toluene C.sub.7H.sub.8
111 8% in SPK 9.5 15.4% 0.79% Cumene C.sub.9H.sub.12 151 8% in SPK
7.8 13.2% 0.51% p-Cymene C.sub.10H.sub.14 177 8% in SPK 7.5 12.2%
0.39% Tetralin C.sub.10H.sub.12 207 8% in SPK 9.5 15.6% 0.81%
Methyl C.sub.11H.sub.10 240 8% in SPK 8.0 16.2 1.64% Napthalene
Aromatic ethers Anisole C.sub.7H.sub.8O 154 8% in SPK 14.8 22.1%
1.63% Dibenzyl Ether (C.sub.6H.sub.5CH.sub.2).sub.2O 158 8% in SPK
23.3 26.1% 2.13% Other aromatic oxygenates Furan C.sub.4H.sub.4O 31
8% in SPK 10.8 16.4% 0.94% Benzyl Alcohol C.sub.6H.sub.5CH.sub.2OH
158 0.5% in SPK 8.6 12.4% 6.60% Note that these experiments were
carried out on de-plasticised O-rings, so they do not represent the
net volume or mass change from "as received" O-rings where the
plasticiser is removed by the solvent/additive. (The de-plasticised
O-ring has already seen a mass loss of approximately 10.0% and a
volume change of approximately 12.5% due to the removal fo the
plasticiser.)
Table 4 shows that the aromatic ethers outperform the other
additives with very high swelling values.
[0088] In order to calculate a swelling efficacy factor, the
effective volume change (due to the use of additive solvent itself)
was calculated by subtracting the volume change that occurs with
neat SPK; and then dividing this value by the concentration of the
additive. This gives a value indicating the capacity of the
additive to improve swelling, normalised by the amount of additive
that was used.
[0089] When these values are normalised by the additive
concentration, the aromatic ethers still score very highly,
especially against the other aromatic species.
* * * * *