8 Effect of Temperature on the Friction and Wear of Some Heat-Resistant Polymers Downloaded by UNIV OF CINCINNATI on May 19, 2016 | http://pubs.acs.org Publication Date: September 12, 1985 | doi: 10.1021/bk-1985-0287.ch008
Kyuichiro Tanaka and Yoshinori Yamada Faculty of Engineering, Kanazawa University, Kanazawa 920, Japan
Friction and wear of polyimide, polyamide-imide, polyether ether keton, polyphenylene sulfide (filled with glass fibers) and polyether sulphone sliding against a smooth steel disk were studied at various disk temperatures. A friction experiment in which a steel sphere was slid on flat polymer plates was also carried out at various temperatures. Friction of the heat resistant polymers generally varied markedly with the temperature. Polyimide, polyamide-imide and polyether ether ketone exhibited relatively low friction at the temperatures above 200°C in their wear process. Polyimide and polyamide-imide showed wear peak at given temperatures ; this appeared to be due to chemical reaction in the polymer chains during sliding at high temperatures. Polyether ether ketone, polyphenylene sulfide and polyether sulphone exhibited little variation in wear rates with temperature up to a certain temperature. A thick transferred polymer layer was generally produced at high temperatures, decreasing the friction and wear of polymers. I t i s w e l l known that the generation of heat at s l i d i n g contact of polymers can produce l o c a l decomposition, hence l i m i t i n g the u s e f u l ness of polymers i n a s l i d i n g a p p l i c a t i o n . Some of the heat r e s i s t a n t polymers developed i n r e l a t i v e l y recent years are expected t o be u s e f u l under severe s l i d e conditions. F r i c t i o n and wear of polyimide which does not flow at high temperatures have been studied by a few authors (1,2,2.). Some of the r e s u l t s obtained indicate that v a r i a t i o n s of f r i c t i o n and wear of polyimide with temperature and s l i d i n g speed are r e l a t i v e l y large. Buckley (l.) reported that polyimide produced a transferred f i l m on the countersurface which then decreased f r i c t i o n . Matsubara et a l . (g) found that polyimide exhibited the peak of wear at a c e r t a i n s l i d i n g speed as s l i d i n g speed was increased and at a c e r t a i n temperature as the temperature was increased. They 0097-6156/ 85/ 0287-0103$07.25/ 0 © 1985 American Chemical Society
Lee; Polymer Wear and Its Control ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
104
POLYMER
W E A R A N D ITS C O N T R O L
a t t r i b u t e d t h i s wear peak t o a chemical reaction during the wear process. I n addition t o polyimide, there are some heat r e s i s t a n t polymers such as polyamide-imide, polyether ether ketone, polyphenylene s u l f i d e and polyether sulphone. At present, however, there e x i s t few studies on f r i c t i o n and wear of heat r e s i s t a n t polymers other than polyimide. Thus, i t i s important t o investigate the f r i c t i o n and wear o f these heat r e s i s t a n t polymers. The purpose of t h i s work is t o study the effect of temperature on the f r i c t i o n and wear of some t y p i c a l heat r e s i s t a n t polymers and the mechanisms of wear of these polymers.
Downloaded by UNIV OF CINCINNATI on May 19, 2016 | http://pubs.acs.org Publication Date: September 12, 1985 | doi: 10.1021/bk-1985-0287.ch008
Experimental Procedures f o r Studying the Fundamental F r i c t i o n a l Properties of the Polymers. To study the fundamental f r i c t i o n a l properties of the heat r e s i s t a n t polymers, a s t e e l sphere of 2.38 mm i n radius was s l i d on f l a t polymer plates at a low speed o f 0 . 2 5 mm/s under various loads ranging from 1 Ν t o 8 Ν and at various temperatures up t o 300 *C, and the f r i c t i o n a l force was measured. The temperature of the specimen polymer surface was c o n t r o l l e d by thermocouple and e l e c t r i c heater. A s t e e l b a l l for b a l l bearing use was used as the sphere i n the experiments. The polymer sufaces were abraded with a 1000-grade abrasive c l o t h and cleaned w i t h e t h y l alcohol. Wear-Testing Apparatus and Experimental Procedures. To study the e f f e c t of temperature on the wear behavior of specimen polymers, the pin-on-disk type wear t e s t i n g apparatus used i n our previous work (h) was employed and the f r i c t i o n a l force and wear depth of the f l a t ended polymer pins 3 mm i n diameter were measured at a s l i d i n g speed of 0 . 1 m/s under a load of 10 Ν and at various experimentally possible disk temperatures up t o 300*0 . The disk was made of s t a i n less s t e e l (SUS 30h) and heated by an e l e c t r i c heater mounted under the disk. The surface roughness of the f r i c t i o n a l surface of the disk was about 0 . 0 2 yum c . l . a . The diameter o f the f r i c t i o n a l track on the disk was 7 cm. The specimen p i n was i n i t i a l l y rubbed against 1000-grade Emery paper placed on the disk. This pre-rubbing was u s e f u l f o r allowing uniform contact between the specimen surface and the disk. A f t e r the pre-rubbing the specimen and disk surfaces were cleaned by rubbing w i t h a soft c l o t h soaked i n e t h y l alcohol. A l l experiments i n t h i s work were c a r r i e d out i n ambient a i r of 60 ±10 % R.H. and room temperature o f 23 ±k*C . Polymer Specimens. The materials used i n t h i s work were polyimide (PI;,polyamide-imide (PAl), polyether-ether-ketone (PEEK), polypheny lene s u l f i d e (PPS) and polyether sulphone (PES). The chemical formulas and p h y s i c a l properties of the specimen polymers are summarized i n Table I . The specimen polymers, except PPS, were u n f i l l e d while the PPS specimen was f i l l e d w i t h glass f i b e r o f kO wt. % . PAI and PES are amorphous polymer with considerably high glass temperature . The polymers, except P I , can flow at high temperatures and allow the use of i n j e c t i o n molding. Experimental Results and Discussion S l i d i n g o f a S t e e l Sphere on F l a t Plates o f Specimen Polymers. Figures 1 (a) and (b) show v a r i a t i o n s i n the c o e f f i c i e n t s of f r i c t i o n Lee; Polymer Wear and Its Control ACS Symposium Series; American Chemical Society: Washington, DC, 1985.
8.
T A N A K A A N DY A M A D A
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Temperature Effects on Friction and Wear
Downloaded by UNIV OF CINCINNATI on May 19, 2016 | http://pubs.acs.org Publication Date: September 12, 1985 | doi: 10.1021/bk-1985-0287.ch008
Table I . Polymer specimens - Chemical formula and some properties.
Chemical type (Abbr.)
Chemical formula
Melting point
Glass temp,
Heat Tensile d i s t o r - strength tion temp. *C kg/cm 2
"Tradename"
°C
°C
/900
polyimide
7^0
(23'C)
( PI )
v -r u
"Vespel-SPl"
polyamideimide ( PAI ) "Torlon"
polyether ether ketone ( PEEK )
s . r
—
y
ca.280
1
33h
lk3
27^ 1900 (23°C)
135-
l60
910
(23°C)
- O O O - s
polypheny lene sulfide ( PPS ) "Ryton R-U": (PPS+G.F. k0%) polyether sulphone ( PES )
J
^
