CA1102107A

CA1102107A - Arc resistant composition

Info

Publication number: CA1102107A
Application number: CA274,006A
Authority: CA
Inventors: Donald G. Needham
Original assignee: Phillips Petroleum Co
Current assignee: Phillips Petroleum Co
Priority date: 1976-07-01
Filing date: 1977-03-15
Publication date: 1981-06-02
Also published as: DE2728233B2; GB1526159A; DE2728233A1; JPS535252A; AU497588B1; CH623842A5; DE2728233C3

Abstract

ARC RESISTANT COMPOSITION
Abstract of the Disclosure An arc resistant composition is produced by incor-porating into poly(arylene sulfide) about 30-60 percent by weight of fillers comprising 0-75 weight percent of glass, 0-50 weight percent of calcium carbonate, and the remainder in-cluding at least one of clay and talc. Preferably the con-tent in clay and talc comprises from about 20 to about 50 weight percent of the arc resistant composition. Addition of small quantities of silanes to the arc resistant composition improves its water resistance or physical properties. Elec-trical components which must be arc resistant and electric arc-heater electrodes can be produced from the compositions made in accordance with this invention.

Description

ARC RESISTA~T COMPOSITION
Background _ the Invention This invention relates to arc resistant compositions. In par-ticular, it relates to arc resistant compositions having poly(arylene sulfide)as their basic ingredlent.
In many commercial applications involving the use of high-voltage electric current, such as electric power transmission, or electric resistance heating, it is either necessary or desirable to employ com-ponents made of materials which are arc resistant as defined in ASTM-D-495-73. Even more desirable are arc resistant compositions which are water resistant and which have acceptable physical properties.
The present invention provides an arc resistant composition which is suitable for being made into electrical components.
It is therefore one object of the invention to provide an arc resistant composition of matter and a process for making same.
Another object of the invention is to provide an arc resistant composition which possesses acceptable physical properties.
; A further object of the invention is to provide an arc resistant composition which is water resistant.
Still another object of the invention is to provide an arc re-sistant composition which has an improved linear coefficient of expansion.
A still further object of the inven-tion is to provide articles made of the arc resistant composition.
Still another object of the invention is to provide an arc re-sistant article having acceptable physical properties and improved water resistance and linear coefficient of expansion.

~'j,l, Summary of the Invention In accordance with one aspect of the invention, an arc resistant composition comprises poly(arylene sulfide) and 30-60 percent by weight of fillers comprising 0-30 wei~ht percent of glass, 0-20 weight percent of calcium carbonate, and the rest being at least one of clay and talc. Preferably the content of clay and talc comprises from about 20 to about 50 weight percent of the arc resistant composition.

-la-,~, ,~, 11~ 37 In accordance with another aspect of the invention, an arc resistant composition having improved water resistance is provided. The composition comprises poly(phenylene sulfide) and 30-60 percent by weight of Eillers with the total amount of fillers comprised of 0-75 weight percent of glass, 0-50 weight percent of calcium carbonate, and about 0.5-5 weight percent oE silanes, and the balance of at least one of clay and talc.
In accordance with a further aspect of the invention, a method for producing an arc resistant composition is provided. Uncured or partially cured poly(phenylene sulfide) is placed in a suitable blender together with 30-60 weight percent of fillers with the total amount of filler comprised of 0-75 weight percent of glass, 0-50 weight percent of calcium carbonate, and at least one of clay and talc. The ingredients are mixed until a homogeneous blend is produced. The blend is then injection molded to form an arc resistant composition.
In accordance with still another aspect of the invention, a method for producing an arc resistant composition which has improved water resistance is provided. Uncured or partially cured poly(phenylene sulfide) is blended in a tumbler together with about 30-60 percent by weight of fillers with the amount of fillers comprised of 0-75 weight percent of glass, 0-50 weight percent of calcium carbonate, about 0.5-5 weight percent of silanes, and a remainder including at least one of talc and clay. The blend is then compression molded to form an arc resistant compositionofdesiredshape.
In accordance with still another aspect of the invention, an article of manufacture is produced using the composition of this invention.
Further aspects of the invention will become apparent to those skilled in the art upon study of this specification and the appended claims.
Detailed Description of the Invention Poly(arylene sulfides) having no additives do not exhibit good arc resistance properties. For example, poly(phenylene sulfide) has arc resistance of about 10 seconds, measured in accordance with ASTM-D-495-73, l~Z~7 whereas the minimum acceptable value for arc resistant materials is about 120 seconds.
Surprisingly, it was discovered that addition of large amounts of fillers with the total amount of fillers comprised of 0-75 weight percent glass, 0-50 weight percent calcium carbonate, and the remainder of at least one of clay and talc to poly(arylene sulfide) produces a composition which is arc resistant, i.e., has arc resistance equal to or greater than 120 seconds as measured by ASTM-D-495-73. Moreover, it was discovered that addition of small amounts of silanes to the new arc resistant composition imparts improved water resistance to the composition and decreases, or at least stabilizes, its linear coefficient of expansion.
Any uncured or partially cured poly(arylene sulfide), whether homopolymer, copolymer, terpolymer, and the like, or a blend of such polymers, can be used in the practice of this invention. In this application an uncured or partially cured polymer is a polymer and the molecular weight of which can be increased by either lengthening of a molecular chain or by cross-linking or by combination of both by supplying thereto sufficient energy, such as heat, preferably in the presence of oxygen. The process which increases the molecular weight of the polymer shall be designated as a curing process. Particularly suited for use in this invention are those poly(arylene sulfides) having inherentviscosities in chloronaphthalene (0.2 gram polymer in 100 cc chloronaphthalene) at 206C (402.8F) of at least about 0.08, preferably between about 0.1 and about 0.3, and more preferably about 0.13 and 0.23. Examples of polymers which can be used in this inventionare disclosed in U.~.3,354,129, James T. Edmonds, Jr. et al, issued November 21, 1967. Other examples of poly(arylene sulfides) are poly(4,4'--biphenylene sulfide); poly(2,4-tolylene sulfide); a copolymer from p-dichlorobenzene, 2,4-dichloratoluene, and sodium sulfide, and blends thereof. Of all of the poly(arylene sulfides) poly(phenylene sulf~ide) (PPS~ polymers are presently preferred for use with the invention.

Any commercially available clay, talc, calcium carbonate, or glass can be used as fillers; high purity of these ingredients is not required.

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Although it is believed that any silane can be utilized to impart improved water resistance and linear coefficient of expansion to the new arc resistant composition, presently preferred are the alkylsilanes, alkoxy-silanes, and polymers thereof. Examples of these are: Y-glycidoxypropyl-trimethoxysilane, methyltrimethoxysilane, and polyisoxymethoxysilane.
The proportion oE fillers added to poly(arylene sulfide) can vary from about 30 to about 60 weight percent of the total composition. The fillers comprise 0-30 weight percent of glass, 0-20 weight percent of calcium carbonate, and the remainder at least one of talc and clay. One presently preferred arc resistant composition comprises:

PPS 45 weight percent Clay 17.5 weight percent Talc 17 5 weight percent Glass 20.0 wei~ht percent The concentration of silanes that can optionally be incorporated into the improved arc resistant composition can vary between about 0.5 and about 5 weight percent, usually between about 0.5 and about 1 weight percent of the total composition.
The method for producing the improved arc resistant composition is best explained by following in sequence the steps of the process.
If the composition is made by injection molding, i-t is desirable to partially cure the polymer to reduce its melt flow to a value below 75 g/10 minutes according to ASTM Method D-1238-74 (343C and 5 kg load).
The polymers having melt flow below that level can be injection molded with greater efficiency. The curing process is accomplished by subjecting the uncured or partially cured polymer, preferably in air, to elevated temperatures until desired melt flow is obtained. Elevated temperatures of at least 500F (2~0C) are normally used; the preferred temperature ranges from 550-900F (288-482C).
The uncured or partially cured polymer is placed in a tumbler or other suitable mixer together with preselected amounts of a filler or fillers, and, opt~onally, a predetermined amount of silanes. The ingredients are compounded in accordance with a known process until a homogeneous blend is produced.
The blend is then introduced into an injection molding apparatus to form, upon processing, an arc resistant composition. The product of the injection molding step can be shaped to a desired form during injection molding or it can be machine- or otherwise-shaped after the injection molding step is completed.
When the composition is not produced by injection molding, but instead by a process such as compression molding, the melt flow character-istics of the poly(arylene sulfide) are normally not as important. Any solid or liquid, uncured or partially cured poly(arylene sulfide) can be blended with the enumerated fillers and the composition cured by application of energy such as heat without first bringing the melt flow of the poly(arylene sulfide) to a preferred minimum level.
The follo~ing examples are provided merely to illustrate the practice of the invention rather than to in any way limit the scope of the invention.
EX~MPLE I
Powder poly(phenylene sulfides), known under the trademark Ryto ~ P3 and having a density of 1.3 measured in accordance with ASTM
D 1505-68 and a melt flow of 75 g/10 minutes measured in accordance with ASTM D 1238-74, (343C and 5 kg load) was blended with varying amounts of clay, talc, calcium carbonate9 mica, and fiberglass. The weight percentage of each filler in each one of -the blends is shown in Table I. The blending was performed by tumbling the ingredients of each sample in a rotating drum blender.
;~ Each of the blends and a batch of pure poly(phenylene sulfide) of the typP used for making the blends were injection molded into bar specimens having dimensions (8.5 inch x 1/2 inch x 125 mils) and shape suitable for ASTM tensile strength. Each specimen was then tested to determine its tensile strength, % elongation, arc resistance (in accordance with ASTM D 495-73). The results are shown in Table I.

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The results indicate that addition of the enumerated fillers decreases the tensile strength of poly(phenylene sulfide) and the % elongation.
However, each one of the fillers improved the arc resistance of the polymer.
The degree to whlch the arc resistance was improved varied greatly depending on the amount and type of the fil]er. The best arc resistance was obtained with blends A, B, and I. Considerably less improvement in arc resistance was observed with blends G and H. Othex blends specifled in Table I resulted in only slight improvement of arc resistance, not sufficient to satisfy the minimum 120 second arc resistance as measured by ASTM D 495-73.
It should be noted that blend I composed of 17% of clay, 17% of talc, and 20% of iberglass resulted in a composition having not only vastly improved arc resistance but also having tensile strength reduced least of any of the other compositions formed through compounding poly(phenylene sulfide).
EXAMPLE II
Since talc and clay in combination with poly(phenylene sulfide) appeared to have good arc resistance, another series of tests was made using varying amounts of these two fillers. The tests were conducted by procedures outllned in Example I. The results are summarized below.
TABLE II

Filler, Wt. % Melt Flow( ) Talc Clay Arc Resistance, seconds g~10 minutes 132 93.6 183 68.1 188 37.
193 10.7 (1) ASTM ~ 1238-7~, 3~3C and 5 kg load The data show that all the blends exceed the minimum accepted value for arc resistance of 120 seconds but that the blends containing 15 wt. % of each filler have by far superior combined properties of arc resistance and melt flow. Good melt flow properties are required for good processability of the composition especially by injection molding.

_ ~ _ EXAMPLE III
A blend of the following ingredients at specified concentrations was produced by mixing in a tumbler:
Ingredient Concentration (wt. %) Partially cured pol.y(phenylene sulfide) 45 Clay 17.5 Talc 17.5 - Glass 20.0 The blend was then subdivided into seven samples. Six of the samples were compounded with 0.8 weight percent of various silanes as follows:
Sample 1 Control, no silane Sample 2 ~-glycidoxypropyltrimethoxysilane (Union Carbide) Sample 3 ~-glycidoxypropyltrimethoxysilane (Dow) Sample 4 methyltrimethoxysilane (Dow) : Sample 5 polyisoxymethoxysilane (Dow) Sample 6 methy.lmethoxysilane (Union Carbide) Sample 7 long chain alkyl silane (Experimental) (Dow) The samples were injection molded to produce specimens of a shape suitable for testing. The physical and electrical properties and coefficients of - linear thermal expansion of each specimen were then tested. The results of the tests appear in Tables III-V.

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The tests of electrical properties in Table IV reveal that all samples had good arc resistance. The dielectric constants of the samples were of the same order of magnitude for all samples but after 7 day-immersion in water, dielectric constants of silane containing samples were about 10-20%
lower than that of the control sample. Volume resistivity of the control after immersion was poorer by a factor of 1000 (103) whereas the silane treated samples showed comparatively little change.
TABLE _ Coefficient of Linear Thermal Expansion Temperature Range: All values x 106/degree C
Property -30 to +30C +70C +125C +140C +225C
Sample 1 20.7 21.8 13.4 23.8 42.7 2 20.1 18.2 22.4 21.6 32.3

3 16.8 14.9 17.5 17.5 17.4

4 19.4 erratic 10.7 16.9 39.6 17.1 17.1 17.4 17.4 16.9 6 16.9 9.9 15.6 17.8 22.2 7 23.7 19.2 31.3 28.3 58.9 The results indicate that silanes contained in samples 3, 5 and 6 cause a significantly lower coefficient of th rmal linear expansion. Silanes in samples 3 and 5 resulted in stabilizing the coefficient of thermal linear expansion over the temperature range of the tests.
Only the silane in sample 7 resulted in increasing the coefficient above that of the control sample (sample 1~. The effect on the coefficient of linear expansion was totally unexpected and no explanation for this effect is offered.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. An arc resistant composition which comprises at least partially cured poly(arylene sulfide) and about 30-60 weight percent of the total composition of fillers com-prising both (1) at least one of glass and calcium carbonate and (2) at least one of clay and talc.

2. An arc resistant composition as claimed in claim 1 wherein said at least one of clay and talc comprises about 20 to about 50 weight percent of the total arc re-sistant composition.

3. An arc resistant composition as claimed in claim 2 further comprising about 0.5 to about 5 percent by weight of silanes.

4. An arc resistant composition as claimed in claim 2 further comprising about 0.5 to about 1% by weight of alkylsilanes, alkyloxysilanes, and polymers thereof.

5. An arc resistant composition as claimed in claim 3 wherein said silanes are selected from the group con-sisting of:
.gamma.-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and polyisoxymethoxysilane.

6. An arc resistant composition as claimed in claim 4 wherein said silanes are selected from the group con-sisting of:
.gamma.-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and polyisoxymethoxysilane.

7. An arc resistant composition as claimed in claim 2 wherein said poly(arylene sulfide) is poly(phenylene sulfide).

8. An arc resistant composition as claimed in claim 7 wherein said poly(phenylene sulfide) comprises about 45 weight percent of the total composition and clay, talc, and glass comprise about 17.5, 17.5, and 20 weight percent of the total composition, respectively.

9. An arc resistant composition as claimed in claim 8 further comprising about 0.5 to about 1 weight percent of silanes selected from the group consisting of:
.gamma.-glycidoxypropyltrimethoxysilane, methyltrimethoxysilane, and polyisoxymethoxysilane.

10. A process for producing an arc resistant composi-tion which comprises:
blending uncured or partially cured poly(arylene sul-fide) with about 30-60 weight percent of the total composi-tion of fillers, said fillers comprising both (1) at least one of glass and calcium carbonate and (2) at least one of clay and talc.

11. A process as claimed in claim 10 in which said at least one clay and talc comprises about 20 to about 50 weight percent of the total arc resistant composition.

12. A process as claimed in claim 11 wherein the blended composition of poly(arylene sulfide) and fillers is further cured by injection molding.

13. A process as claimed in claim 10 wherein said poly(arylene sulfide) is poly(phenylene sulfide).

14. A process as claimed in claim 11 wherein said poly(arylene sulfide) is poly(phenylene sulfide).