Note: Descriptions are shown in the official language in which they were submitted.
1 339 ~ 68
A POLYSTYRENE-BASED RESIN COMPOSITION
1 BACKGROUND OF THE INVENTION
As is well known, polymers of styrene widely under
practical use are usually obtained by the free-radical poly-
merization and they have an atactic structure in respect of
the stereospecificity of the molecular structure. These
styrene-based resins, however, are not quite satisfactory in
their relatively poor heat resistance and mechanical strengths.
The inventors have continued extensive investigations to obtain
a styrene-based resin freed from the disadvantages of conven-
tional styrene-based resins and arrived at a discovery that
the requirement can well be satisfied by using a styrene-based
resin of which the molecular structure relative to the
stereospecificity is-mainly syndiotactic. While such a
styrene-based polymer having a mainly syndiotactic molecular
structure relative to the stereospecificity, which is referred
to as a syndiotactic polystyrene hereinbelow, has as such
excellent heat resistance in comparison with conventional
polystyrenes having an atactic molecular structure, various
other properties of the resin should desirably be improved in
order that the resin is very useful in a wide variety of
applications.
SU~MARY OF THE IN~IENTION
The present invention accordingly has an object to provide
1339168
1 a resin composition based on a syndiotactic polystyrene and
having greatly improved properties to be freed from the disad-
vantages of conventional styrene-based resin compositions.
The polystyrene-based resin composition of the present
inventlon compr1ses:
(a) a styrene-based polymer of which the molecular structure
relative to the stereospecificity is mainly syndiotactic; and
(b) an additive selected from the group consisting of thermo-
plastic resins excluding of the styrene-based polymer of which
the molecular structure relative to the stereospecificity is
mainly syndiotactic (referred to as "thermoplastic resins"
hereinunder) and inorganic fillers.
Namely, the present invention proposes, on one hand, to
compound a syndiotactic polystyrene with a thermoplastic resin
lS such as polycarbonate resins so that the resultant polystyrene-
based resin composition is imparted with greatly improved heat
resistance, mechanical strengths and other properties in good
balance as a useful molding resin composition. The invention
proposes, on the other hand, to compound a syndiotactic poly-
styrene with an inorganic filler such as glass fibers, optionally,in combination with a thermoplastic resin so that the resultant
resin composition is imparted with further improved heat re-
sistance and mechanical strengths to satisfy the requirements
for molding resin compositions.
Accordingly, the invention in one aspect provides a
polystyrene-based resin composition which comprises: (a) a
styrene-based polymer of which the molecular structure
relative to the stereospecificity is mainly syndiotactic,
Bl
1 33q 1 6P~
1 selected from the group consisting of homopolymeric
polystyrenes, poly (alkyl styrenes), poly (halogenated
styrenes), poly (alkoxy styrenes), poly (styrene
carboxylates), mixtures thereof and copolymers mainly
composed thereof; and (b) an additive selected from the
group consisting of a thermoplastic resin other than said
styrene-based polymer having said syndiotactic molecular
structure, and selected from styrene-based polymers and
copolymers, polystyrenes having an atactic molecular
structure, polystyrenes having an isotactic molecular
structure, acrylonitrile-styrene resins, acrylonitrile-
butadiene-styrene resins, styrene-butadiene-styrene block
copolymers, rubbers obtained by partially or completely
hydrogenating the butadiene portion of a styrene-butadiene
block copolymers, condensation-polymerized polymers,
polyesters, polycarbonates, polyethers, polyamides,
polyoxymethylenes, acrylic polymers, poly (acrylic acid),
poly (acrylic acid esters), poly (methyl methacrylate),
polyolefins, polyethylene, polypropylene, polybutene, poly
(4-methylpentene-1), copolymers of ethylene and propylene,
polymers of vinyl halides, poly (vinyl chloride), poly
(vinylidene chloride), poly (vinylidene fluoride); and an
inorganic filler.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The syndiotactic polystyrene implied in the present
~'
- 4 - I 339 1 68
1 invention is a polymer of styrene of which the molecular
structure relative to the stereospecificity is mainly syn-
diotactic or, in other words, a polymer of styrene in which
the phenyl or substituted phenyl groups as the pendant groups
to the main chain of the polymeric structure are positioned
alternately to the reverse directions relative to the carbon-
to-carbon linkages in the polymeric main chain. The tacticity
thereof can be quantitatively determined by the nuclear magnetic
resonance absorption spectrometric method, referred to as the
NMR method hereinbelow.
The tacticity determined by the NMR method can be expressed
by the proportion of a plural number of the structural units
existing in consecutive sequence such as diads, triads and
pentads for two, three and five structural units, respectively.
The tacticity of the syndiotactic polystyrene as the component
(a) of the inventive resin composition should be at least 85%
and at least 50% for the diads and pentads, respectively. The
polystyrene having such a stereospecificity is not limited to
homopolymeric polystyrenes but includes poly(alkyl styrenes),
poly(halogenated styrenes), poly(alkoxy styrenes), poly(styrene
carboxylates) and mixtures thereof as well as copolymers mainly
composed thereof. Exemplary of the poly(alkyl styrenes), poly-
(halogenated styrenes) and poly(alkoxy styrenes) are: poly-
(methyl styrene), poly(ethyl styrene), poly(isopropyl styrene),
poly(tert-butyl styrene) and the like; poly(chlorostyrene),
poly(bromostyrene) and the like; and poly(methoxy styrene),
poly(ethoxy styrene) and the like, respectively.
B~
- 4A - 1 3 3 9 1 6 8
1 The syndiotactic polystyrene of the present invention has
a weight-average molecular weight of at least 100,000, prefer-
ably at least 200,000. When said molecular weight is smaller
than 100,000, the resin composition with sufficient heat
resistance and mechanical strength can not be obtained.
When the polystyrene-based resin composition of the
invention is composed of the syndiotactic polystyrene and a
thermoplastic resin, the amount of the syndiotactic polystyrene
in the resin composition should be in the range from 1 to 99
by weight, preferably from 5 to 95~ by weight. When the
amount thereof is smaller than 1% by weight, the desired effect
cannot be fully exhibited in the improvement of the heat
resistance of the thermoplastic resin while an amount thereof
- larger than 99% by weight results in the loss of the object
of the present invention to improve the heat resistance of
thermoplastic resins in general.
The basic ingredient of the inventive resin composition
is an ordinary thermoplastic resin other than the above mentioned
styrene-based polymers having a syndiotactic molecular structure.
The thermoplastic resin is not limited to a specific one but
can be selected from a variety of thermoplastic resins depend-
ing on the intended application of the resin composition.
Exemplary of the thermoplastic resin are styrene-based polymers
and copolymers including polystyrenes having an atactic molecular
structure, polystyrenes having an isotactic molecular structure,
Acrylonitrile-styrene resins, Acrylonitrile-butadiene-styrene
resins, Styrene-butadiene-styrene block copolymers, Rubbers
obtained by partially or completely hydrogenating the butadiene
portion of a styrene-butadiene block copolymers an~ the like,
condensation-polymerized polymers including polyesters,
D~
- 5 - 1 33 9 1 68
1 polycarbonates, polyethers, polyamides, polyoxymethylenes
and the like, acrylic polymers including poly(acrylic acid),
poly(acrylic acid esters), poly(methyl methacrylate) and the
like, polyolefins including polyethylene, polypropylene,
polybutene, poly(4-methylpentene-1), copolymers of ethylene
and propylene and the like, polymers of vinyl halides including
poly(vinyl chloride), poly(vinylidene chloride), poly(vinylidene
fluoride) and the like, and so on.
The alternative additive ingredient in the inventive
resin composition is an inorganic filler which is not limited
to a specific one but can be selected from a variety of known
inorganic fillers depending on the intended application of
the resin compositiOn. Exemplary of suitable inorganic fillers
are glass fibers, carbon fibers, alumina fibers, carbon black,
graphite, titanium dioxide, silica, talc, mica, asbestos,
calcium carbonate, calcium sulfate, barium carbonate, magnesium
carbonate, tin oxide, alumina, kaolin, silicon carbide, metal
powders and the like. These inorganic fillers can be used
either singly or as a combination of two kinds or more accord-
ing to need.
When the inventive resin composition is composed of the
syndiotactic polystyrene and the inorganic filler, the weight
ratio of the syndiotactic polystyrene to the inorganic filler
should be in the range from 15:85 to 99:1 or, preferably, from
50:50 to 95:5.
Further, when the inventive resin composition comprises
the syndiotactic polystyrene, the thermoplastic resin and the
- 6 - 1 339 1 68
1 inorganic filler, the formulation of the composition should
contain from 5 to 50 parts by weight of the inorganic filler
per 95 to 50 parts by weight of the total amount of the syn-
~diotactic polystyrene and the thermoplastic resin.
S The compounding work of the above described components
to prepare the inventive resin composition can be performed
by using a conventional blending machine such as a Bànbury
mixer, Henschel mixer, roller mill and the like. It is of
course optional that the resin composition is prepared by the
solution blending method.
The blending work of the components shoul~ be performed
at an elevated temperature so that heat stabilizers convention-
ally used in the compounding works of atactic polystyrenes
cannot be used due to the dissipation and thermal decomposition.
Instead, the object of heat-stabilization of the inventive
resin composition can be achieved by admixing the resin
composition with from 0.005 to 5 parts by weight or, preferably,
from 0.01 to 1 part by weight, per 100 parts by weight of the
resinous ingredients, of a combination of a phenolic anti-
oxidant and a phosphorus compound represented by the general
formula
~O-CH2 ~CEI2 ~ \ p O R2
\ O--CH2 / CH2-~
in which Rl and R2 are each, independently from the other, a
monovalent hydrocarbon group selected from the class consisting
_ 7 _ 1 3 3 9 1 68
1 of alkyl groups having 1 to 20 carbon atoms, cycloalkyl
groups having 3 to 30 carbon atoms and aryl groups having
6 to 20 carbon atoms. The weight ratio of the phosphorus
compound to the phenolic antioxidant should usually be in
the range from 100:1 to 1:1 or, preferably, from 10:1 to 2:1
Exemplary of the above mentioned phosphorus compound are
distearyl pentaerithritol diphosphite, dioctyl pentaerithritol
diphosphite, diphenyl pentaerithritol diphosphite, bis(2,4-
di-tert-butyl phenyl) pentaerithritol diphosphite, bis(2,6-
di-tert-butyl-4-methyl phenyl) pentaerithritol diphosphite,
dicyclohexyl pentaerithritol diphosphite and the like.
The phenolic antioxidant can be any of knwon ones
exemplified by 2,6-di-tert-butyl-4-methyl phenol, 2,6-
diphenyl-4-methoxy phenol, 2,2'-methylene bis(6-tert-butyl-
4-methyl phenol), 2,2'-methylene bis(6-tert-butyl-4-ethyl
phenol), 2,2'-methylene bis[4-methyl-6-(~-methyl cyclohexyl)
phenol], l,l-bis(5-tert-butyl-4-hydroxy-2-methyl phenyl)
butane, 2,2'-methylene bis(4-methyl-6-cyclohexyl phenol),
2,2'-methylene bis(4-methyl-6-nonyl phenol), 1,1,3-tris(5-
tert-butyl-4-hydroxy-2-methyl phenyl) butane, 2,2-bis(5-
tert-butyl-4-hydroxy-2-methyl phenyl 4-n-dodecyl mercapto
butane, ethylene glycol bis[3,3-bis(3-tert-butyl-4-hydroxy
phenyl) butyrate], l,l-bis(3,5-dimethyl-2-hydroxy phenyl)-
3-(n-dodecylthio) butane, 4,4'-thio-bis(6-tert-butyl-3-methyl
phenol), 1,3,5-tris(3,5-di-tert-butyl-4-hydroxy benzyl)-2,4,6-
trimethyl benzene, 2,2-bis(3,5-di-tert-butyl-4-hydroxy benzyl)
malonic acid octadecyl ester, n-octadecyl 3-(4-hydroxy-3,5-di-
- 8 - 1 339 1 68
1 tert-butyl phenyl) propionate, tetrakis[methylene(3,5-di-
tert-butyl-4-hydroxy hydrocinnamate)]methane and the like.
When the inventive resin composition is prepared by com-
~pounding an inorganic filler having electroconductivity, such
as carbon black, graphite and the like, in an amount of 10 to60% by weight based on the overall amount of the resin composi-
tion with thorough mixing, the resultant resin composition can
be a heat-sensitive resistive composition having a positive
temperature coefficient. It is preferable that the electro-
conductive inorganic filler such as carbon black used in theabove mentioned object has a particle diameter in the range
from 10 to 200 nm.
The thus obtained resin composition has greatly improved
properties in the heat resistance and mechanical strengths as
compared to the polystyrene-based resin compositions convention-
ally used in various applications. Accordingly, the resin com-
position of the invention is useful in a wide field of applica-
tions as a material for various industrial uses and a material
of various machines and instruments in which heat resistance
and mechanical strengths higher than conventional are essential.
In the following, the polystyrene-based resin composition
of the invention is described in more detail by way of examples
and comparative examples.
Polymer Preparation 1. Preparation of a polystyrene resin
having a mainly syndiotactic molecular structure.
Into a solution of 20 m moles of cyclopentadienyl
titanium trichloride and 0.8 mole as aluminum atoms of methyl
1 339 1 68
1 aluminoxane as the catalyst constituents dissolved in 2
liters of toluene were added 3.6 liters of styrene and the
polymerization of styrene was performed at 20~C for 1 hour.
After completion of the polymerization reaction, the reaction
product was washed with a mixture of hydrochloric acid and
methyl alcohol to decompose and remove the catalyst constituents
followed by drying to give 330 g of dried polymeric product.
The polymeric product was then subjected to extraction
with methyl ethyl ketone as the extraction solvent using a
Soxhlet extractor. The amount of the polymer remaining as
unextracted was 95% by weight of the amount before extraction.
This polymer had a weight-average molecular weight of about
280,000, number-average molecular weight of about 57,000 and
melting point of 270~C. The NMR analysis of this polymer
utilizing the 13C carbon isotope indicated that the NMR
absorption spectrum had a peak of absorption at 145.35 ppm
which could be assigned to the syndiotactic molecular struc-
ture of polystyrene. Calculation from the area of this peak
gave a result that the polymer had a syndiotactivity of 96%
in pentads (refer to H. Sato & Y. Tanaka, J. Polym. Sci.
Polym. Phys. Ed. 21, 1667-1674 (1983)).
Polymer Preparation 2. Preparation of a polystyrene resin
having a mainly syndiotactic molecular structure.
Into a solution of 13.4 m moles of titanium tetraethoxide
and 1340 m moles as aluminum atoms of methyl aluminoxane as
the catalyst constituents dissolved in 1.2 liters of toluene
were added 33 liters of styrene and the polymerization
- 10 - 1 3 3 q 1 6 8
1 reaction was performed for 1.5 hours at 55~C. After comple-
tion of the polymerization reaction, the reaction product
was washed with a mixture of hydrochloric acid and methyl
,~alcohol to decompose and remove the catalyst constituents
followed by drying to give 3.5 kg of a dried polymeric
product.
The polymeric product was then subjected to extraction
with methyl ethyl ketone as the extraction solvent using a
Soxhlet extractor. The amount of the polymer remaining unex-
tracted was 95% by weight of the amount before extraction.This polymer had a weight-average molecular weight of about
800,000, number-average molecular weight of about 26,700 and
melting point of 270~C. The NMP analysis of this polymer
utilizing the 13C carbon isotope indicated that the NMR
absorption spectrum had a peak of absorption at 145.35 ppm
which could be assigned to the syndiotactic molecular struc-
ture of polystyrene. Calculation from the area of this peak
gave a result that the polymer had a syndiotacticity of 97%
in pentads.
Example 1
~ resin composition was prepared by compounding 80 parts
by weight of a polycarbonate resin (Idemitsu Polycarbonate
A2500, a product by Idemitsu Petrochemical Co.) as a thermo-
plastic resin and 20 parts by weight of the syndiotactic
polystyrene obtained in Polymer Preparation 1 described above.
The resin composition was shaped by using a Minimat molding
- 11 1 339 1 68
1 machine into test specimens of which the mechanical strengths
as well as the Vicat softening point as a thermal property
were measured to give the results shown in Table 1.
Example 2
The same experimental procedure as in Example 1 was
undertaken except that the blending ratio of the polycarbonate
resin and the syndiotactic polystyrene was 50:50 by weight
instead of 80:20 by weight. The results of the experiment
are also shown in Table 1.
Example 3
The same experimental procedure as in Example 1 was
undertaken except that the blending ratio of the polycarbonate
resin and the syndiotactic polystyrene was 20:80 by weight
instead of 80:20 by weight. The results of the experiment
are also shown in Table 1.
Example 4
The same experimental procedure as in Example 1 was
undertaken except that the polycarbonate resin as a thermo-
plastic resin was replaced with the same amount of a poly-
ethylene terephthalate resin (Pyropet RY 533~ a product by
Toyo Boseki Co.). The results of the experiment are also
shown in Table 1.
~ Tr~e ~
- 12--
1 339 1 68
1 Example 5
The same experimental procedure as in Example 4 was
undertaken except that the blending ratio of the polyethylene
~terephthalate resin and the syndiotactic polystyrene was
50:50 by weight instead of 80:20 by weight. The results of
the experiment are also shown in Table 1.
Example 6
The same experimental procedure as in Example 1 was
undertaken except that the polycarbonate resin was replaced
with the same amount of an ABS resin (JSR ABS 15, a product
by Japan Synthetic Rubber Co.). The results of the experi-
ment are also shown in Table 1.
Example 7
The same experimental procedure as in Example 6 was
undertaken except that the blending ratio of the ABS resin
and the syndiotactic polystyrene was 50:50 by weight instead
of 80:20 by weight. The results of the experiment are also
shown in Table 1.
Example 8
The same experimental procedure as in Example 1 was
undertaken except that the polycarbonate resin was replaced
with the same amount of a polysulfone resin (Udel Polysulfone
P-1700, a product by Union Carbide Corp.). The results of
the experiment are also shown in Table 1.
- 13 - 1 3391 68
Example 9
The same experimental procedure as in Example 8 was
undertaken except that the blending ratio of the polysulfone
resin and the syndiotactic polystyrene was 50:50 by weight
instead of 80:20 by weight. The results of the experiment
are also shown in Table 1.
Comparative Examples 1 to 4
Without blending with the syndiotactic polystyrene,
measurement of the properties was undertaken of each of the
polycarbonate resin, polyethylene terephthalate resin, ABS
resin and polysulfone resin used in the preceding examples
in Comparative Examples 1, 2, 3 and 4, respectively. The
results of the measurements are also shown in Table 1.
- 14 - 1339168
Table 1
1 Tensile Ultimate Elastic Vicat soften-
strength, elongation, modulus, ing point,
kg/cm2 % kg/cm2 oC
Example 1 600 4.5 21,800 170
2 610 4.1 29,200 190
3 620 10.0 32,500 200
4 650 2.8 28,200 200<
580 2.6 29,200 200<
6 520 2.6 22,500 150
7 560 2.5 26,000 180
8 650 3.5 25,900 200<
9 490 3.0 28,300 200<
Comparative
15Example 1 590 120 15,200 150
2 710 7.6 26,900 200<
3 500 15.3 20,300 110
4 710 60 21,700 190
Example 10
A resin compound was prepared by blending, in a Henschel
mixer, 80 parts by weight of the syndiotactic polystyrene ob-
tained in Polymer Preparation 2 described above, 20 parts by
weight of chopped glass fibers having an average fiber length
of 3 mm (a producb by Asahi Fiber Glass Co.), 0.5 part by
weight of bis(2,4-di-tert-butyl phenyl) pentaerithritol
diphosphite and 0.2 part by weight of n-octadecyl 3-(4-hydroxy-
2,5-dikutyl phenyl)propionate and the resin compound was
1 339 1 68
- 15 -
1 pelletized by kneading in and extruding out of an extruder
machine. The pelletized resin compound was molded into test
specimens of which the mechanical strengths were measured to
give results including 1050 kg/cm2 of tensile strength, 1490
kg/cm2 of flexural strength and 98,000 kg/cm2 of elastic
modulus of bending. The heat distortion temperature of the
test specimens was 250~C.
Example 11
The same experimental procedure as in Example 10 was
undertaken except that the blending ratio of the syndiotactic
polystyrene and chopped glass fibers was 70:30 by weight
instead of 80:20. The test specimens prepared from the resin
compound had properties including 1120 kg/cm2 of tensile
strength, 1600 kg/cm2 of flexural strength, 104,000 kg/cm2
of elastic modulus of bending and 250~C of heat distortion
temperature.
Example 12
The same experimental procedure as in Example 10 was
undertaken except that the chopped glass fibers as an
inorganic filler were replaced with the same amount of chopped
carbon fibers having a diameter of 9 ~m and an average fiber
length of 3 mm. The test specimens prepared from the resin
compound had properties including 1100 kg/cm2 of tensile
strength, 1500 kg/cm2 of flexural strength, 90,000 kg/cm2
of elastic modulus of bending and 250~C of heat distortion
temperature.
- 16 - 1 33~ 1 6~
1 Example 13
The same experimental procedure as in Example 12 was
undertaken except that the blending ratio of the syndiotactic
~polystyrene and the chopped carbon fibers was 70:30 by weight
instead of 80:20. The test specimens prepared from the resin
compound had properties including 1200 kg/cm2 of tensile
strength, 1600 kg/cm2 of flexural strength, 90,000 kg/cm2
of elastic modulus of bending and 250~C of heat distortion
temperature.
Example 14
The same experimental procedure as in Example 10 was
undertaken except that the chopped glass fibers as an
inorganic filler were replaced with the same amount of pulver-
rized mica having a fineness of 60 mesh or finer by the Tyler
standard. The test specimens prepared from the resin compound
had a heat distortion temperature of 230~C.
Example 15
The same experimental procedure as in Example 14 was
undertaken except that the blending ratio of the syndiotactic
polystyrene and the mica powder was 50:50 by weight. The
test specimens prepared from the resin compound had a heat
distortion temperature of 250~C.
Comparative Example 5
The same experimental procedure as in Example 10 was
- 17 - 1 33~ 1 68
1 undertaken except that the syndiotactic polystyrene was
replaced with the same amount of a commercial product of
polystyrene resin having an atactic structure of the polymer
in the stereospecificity and a weight-average molecular weight
of about 300,000 (a product by Idemitsu Petrochemical Co.).
The test specimens prepared from the resin compound had
properties including 650 kg/cm2 of tensile strength, 690
kg/cm2 of flexural strength, 36,000 kg/cm2 of elastic modulus
of bending and 110~C of heat distortion temperature.
Example 16
A resin compound was prepared by blending, in a Henschel
mixer, 40 parts by weight of the syndiotactic polystyrene
obtained in Polymer Preparation 2 described above, 40 parts
by weight of a commercial product of a polystyrene resin
having an atactic molecular structure as a thermoplastic
resin (Idemitsu Styrol US 315, a product by Idemitsu Petro-
chemical Co.), 20 parts by weight of chopped glass fibers
having an average fiber length of 3 mm (a product by Asahi
Fiber Glass Co.), 0.5 part by weight of bis(2,4-di-tert-
butyl phenyl) pentaerithritol diphosphite and 0.2 part byweight of tetrakis[methylene (3,5-di-tert-butyl-4-hydroxy
hydrocinnamate)3 methane and the resin compound was pel-
letized by kneading in and extruding out of an extruder
machine. The pelletized resin compound was shaped into
test specimens of which the mechanical and thermal properties
were measured to give the results shown in Table 2 below.
- 18 -
1 33~ 1 68
1 Examples 17 to 20
The same experimental procedure as in Example 16 was
undertaken in each of Examples 17 to 20 except that the
~atactic polystyrene used as a thermoplastic resin was replaced
each with the same amount of the polycarbonate resin used in
Example 1, the polyethylene terephthalate resin used in
Example 4, the ABS resin used in Example 6 and the polysulfone
resin used in Example 8, respectively. Table 2 also shows
the mechanical and thermal properties of the test specimens
prepared from the resin compounds.
Table 2
Tensile Ultimate Elastic Vicat soften-
Example strength, elongation, modulus, ing point,
No. kg/cm2 % kg/cm2 ~C
16 870 1.3 80,000 200<
17 920 2.0105,000 200<
18 950 1.4110,000 200<
19 840 1.4 94,000 200<
740 1.6102,000 200<
Example 21
A resin compound was prepared, in a Labo-plastomill,
by blending 60 parts by weight of the syndiotactic polystyrene
prepared in Polymer Preparation 2 described above and 40
parts by weight of carbon black having an average particle
diameter of 43 nm (Diablack E, a product by ~itsubishi
Chemical Industry Co.) and kneading the blend at 295~C for
19 - 1 339 1 68
1 20 minutes. The resin compound was pelletized and then
compression-molded into a sheet in a compression molding
machine at 300~C under a pressure of 150 kg/cm2 taking 10
minutes.
The thus prepared resin sheet was sandwiched between two
foils of electrolytic nickel and pressed under the same
conditions as above so that the nickel foils were bonded to
and integrated with the resin sheet to give a laminated sheet
having a thickness of 1 mm. Test pieces of each 1 cm by 1 cm
wide were prepared by cutting the laminated sheet and sub-
jected to the measurement of the electric properties
utilizing the two nickel foils on both sides of the resin
sheet as the electrodes.
The electrical measurement gave a result that the
specific resistance of the resin sheet was 1.0 ohm cm at
room temperature. The specific resistance showed a rapid
increase by temperature elevation at 280~C to give a value
which was larger than that at room temperature by 102 5
times. The characteristic of power consumption as a heater
element was examined to find that the heat evolution cor-
responded to 2.4 watts in the steady-value region where the
product of the current and voltage had a constant value.
