- Email: [email protected]
mica ternary composites
October 2001
Materials Letters 51 Ž2001. 120–124 www.elsevier.comrlocatermatlet
Mechanical properties and morphologies of poly žether ketone ketone/ rglass fibersrmica ternary composites Daoji Gan ) , Wenjing Cao, Caisheng Song, Zhijian Wang Department of Materials Science and Engineering, Nanchang Institute of Technology, Nanchang, Jiangxi 330034, People’s Republic of China Received 9 January 2001; accepted 12 January 2001
Abstract PolyŽether ketone ketone. ŽPEKK. composites were developed using glass fibers ŽGF. and mica as combining fillers. For the composites having 30 wt% of the total fillers, the highest tensile strength was observed at the filler containing ca. 50 wt% of mica. Partial replacement of GF with mica resulted in reduced coefficient of friction and wearing rate of the materials. The fractured surface of the composites did not have large voids and microcracks. q 2001 Elsevier Science B.V. All rights reserved. Keywords: PolyŽether ketone ketone.; Composites; Mechanical properties; Frictional behavior
1. Introduction Many commercial polymer materials are composites, since they provide reduced costs and improved thermal, mechanical and electrical properties that cannot be obtained from simple polymers. A great variety of the physical properties can be obtained through alternating compositions of the polymer composites w1x. PolyŽaryl ether ketones. ŽPAEK., as a type of high-performance polymers, have found many applications in aerospace, coating and insulating material fields w2–8x. Reinforcement of PAEK with carbon or glass fibers could result in significant ) Corresponding author. Present address: School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State St., Atlanta, GA 30332, USA. Tel.: q1-404-367-8645; fax: q1-404894-7452. E-mail address: [email protected] ŽD. Gan..
improvement of the physical, mechanical and frictional properties w6,9–11x. Mica, due to its excellent mechanical, electrical and thermal properties, has been widely used as reinforcing filler in polymeric matrices, such as polyolefins, polyesters, polyamides, epoxies and polyurethanes w12x. However, there are few reports on the PAEK composites filled with mica w13x. Previously, we investigated the PAEK composites filled with different contents of mica w14x. Increased rigidity of the materials was observed as a function of mica amounts, while the highest mechanical strength could be obtained at a particular content of mica. Here, we report the preparation of the PEKK composites with combining fillers of glass fibers and mica. The goals are to maintain the mechanical property and to reduce the cost of the composites, since micas are much cheaper than glass fibers. Therefore, the effects of filler ratios on the mechani-
00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 1 . 0 0 2 7 6 - 2
D. Gan et al.r Materials Letters 51 (2001) 120–124
cal and frictional properties of the materials were examined. 2. Experimental PolyŽether ketone ketone. ŽPEKK, Scheme 1., synthesized via polycondensation of diphenyl ether with terephthaloyl chloride ŽTPC.risophthaloyl chloride ŽIPC. Žmolar ratio: 0.7:0.3. in the presence of AlCl 3 and 1,2-dichloroethanerdimethylformamide ŽDMF. w15,16x, has a glass transition temperature ŽTg . at 1608C and a reduced viscosity Žhinh . of 0.95. The phlogopite-type mica used here has an average diameter larger than 50 mm. The glass fibers ŽGF. are chopped strands, which have the average length of 3–6 mm. Before using, both mica and GF were coated with a thin layer of sulfonated polyŽether ketone ketone. ŽS-PEKK. through immersion in 2 wt% S-PEKKrDMF solution, as described previously w14x. Mica and GF were first mechanically ground and mixed by a miller. PAEK and fillers, at appropriate ratio, were blended in a Brabender Plastic-corder Model PLE 330 at 3808C. A rotation speed of 70 rpm was maintained for 12 min to get finely dispersed composites, which were then compressed, at 1658C, in molds to get the specimen sheets. The specimens were heated on a steel stage at 3508C for a short time and dropped immediately into ice water to yield amorphous glassy samples, which was demonstrated by the disappearance of the crystallization peak during differential scanning calorimetry ŽDSC. measurements w17x. An instron machine, Model 5583 ŽInstron, Canton, MA, USA., having a video-monitored optical extensometer, was used to measure the mechanical properties. The specimen films, ca. 2-mm thick and cut into a dumbbell shape using a die, were tested at room temperature with a crosshead rate of 2 mmrmin, according to ASTM D-638. Tensile modulus was calculated from the initial slope of the stress–strain curve, while both the tensile strength and elongation were the values at the breaking point.
Scheme 1. Structure of polyŽether ketone ketone. ŽPEKK..
121
Sliding friction and wearing loss were determined using a China-made MZ 200 friction-and-wear tester under ambient environment at a sliding speed of 0.5 mrs. The specimens Žrectangular dimension: 30 = 7 = 9 mm. were held by a loading arm, which recorded the friction force Ž Ff .. Coefficient of friction Ž m . was calculated by m s FfrFn , where Fn is the normal loading force used in the test. The weight of the specimens before and after the test was determined and converted into volume using their density. Wearing rate ŽWs . was calculated by Ws s Ž V0 y V1 . r Ž Fn = L .
mm3r Ž N m .
where V0 is the volume of the sample before the test, V1 is the volume after the test, and L is the sliding distance. For the tensile tests and sliding friction measurements, the data shown here are the average values of six replicated tests. The cryogenically fractured surfaces of the specimens were examined by a JEOL 6300 scanning electron microscope ŽSEM.. Before the experiment, the surfaces were coated with a thin layer of gold.
3. Results and discussion To optimize the appropriate ratio of fillers, the mechanical properties of the composites filled with a single filler of GF were first investigated. With the increase of GF content in the materials, tensile modulus increased, ultimate elongation decreased, while tensile strength exhibited a maximum value at a weight ratio of ; 30% GF used ŽTable 1.. This could be attributed to the counterbalance of increased surface fracture energy and increased sizes of voids or GF aggregates as GF contents in the polymer composites increased w1,18x. Since dispersed GF in the composites made the crack propagation path longer, absorbed a portion of the energy and enhanced the plastic deformation, the surface fracture energy of the materials increased and the strength of the composites should increase as well, as a function of GF contents w18x. However, with the increase of the GF contents, the size of the voids due to the detachment of PEKK from GF gradually increased, and might initiate, the main crack w18x. In addition, the inevitably increased agglomeration of dispersed filler particles resulted in decreased me-
D. Gan et al.r Materials Letters 51 (2001) 120–124
122
Table 1 Tensile properties of PEKK and its compositesa Composition Žweight. PEKKrGF
Modulus ŽGPa. b
PEKKrGFrmica
Value
S.D.
70:25:5 70:20:10 70:15:15 70:10:20 70:5:25 70:0:30
4.20 5.64 8.45 12.57 13.53 13.94 14.08 14.85 16.08 16.89 17.25 18.14
0.81 0.32 0.15 0.84 0.95 0.97 1.23 0.23 0.27 0.32 0.21 0.74
100:0 95:5 90:10 80:20 70:30 60:40
Strength ŽMPa. c e
Value
S.D.
102.0 130.2 175.4 200.3 215.1 195.6 220.9 230.2 235.5 222.1 210.3 180.4
3.9 0.8 1.3 2.2 1.1 1.9 2.3 1.1 2.0 1.5 1.9 3.0
Elongation Ž%. d e
Value
S.D.e
62.1 51.0 40.1 18.3 7.5 3.2 6.0 6.7 7.1 5.2 4.8 4.0
2.5 1.2 0.8 1.1 0.7 1.2 0.5 0.4 0.5 0.2 0.3 0.6
a
Average value of six replicated measurements. Tensile modulus. c Tensile strength. d Ultimate elongation. e Standard deviation. b
chanical strength because of the low strength of the agglomerates themselves w1x. Since the composites containing 30 wt% of GF exhibited the highest tensile strength in our examination, the total filler content in the composites afterwards was kept constant at 30 wt%, and mica was used to gradually replace GF ŽTable 1.. The tensile modulus of the composites increased with the increasing replacement of GF by mica that has a higher modulus than GF. Interestingly, the highest tensile strength and ultimate elongation were obtained at a point where 50 wt% of GF were replaced by mica. Many factors, such as the properties and distribution of fillers, the morphology of the system and the nature of the interface between phases, affect the properties of polymer composites. In general, the composites containing two or more fillers, due to the existence of large voids and inhomogeneous distribution of fillers in the system, exhibit reduced mechanical properties in comparison with those containing single-component fillers w18x. The improved mechanical properties, in our case, may be explained by the fact that GF and mica tended to move and orient in different ways in the process of melt blend, while the fine-grained particles were capable of locating among the large particles, and even facilitating, the melt flow. The same phenomenon was found in polypropylene composites w19x.
Frictional properties of these materials were measured using a friction-and-wear tester. A normal loading force of 100 N was used in the measurements, since there would be no significant difference in the frictional properties if the normal loading force smaller than 60 N was used in the tests. The frictional properties of the materials as a function of GFrmica are shown in Fig. 1. Addition of GF to the polymer led to the increase of frictional coefficient and wearing rate, while replacement of GF with mica
Fig. 1. Frictional properties of PEKK and its composites measured under a normal loading force of 100 N.
D. Gan et al.r Materials Letters 51 (2001) 120–124
resulted in reduced coefficient of friction and wearing rate. The frictional behavior of polymer composites is determined by both components, rigid particles and deformable polymers, which are interactive during the frictional process. The coefficient of friction and wearing rate are directly proportional to the real contact area, which decreases with the increasing modulus of the materials in a given system w20x. Therefore, both GF and mica are efficient components to reduce the coefficient of friction and wearing rate of polymer composites, given the increased modulus of the polymer composites, as observed by the tensile tests. However, as fillers are added to polymer, the friction-induced thermal and mechanical effects inevitably increase, which results in enhanced softening and plastic deformation of polymer as well as detachment of the filler from polymer matrix, leading to the increase of frictional coefficient and wearing rate of the materials w20x. The final frictional behavior of the resulted materials depends on the balance of these two phenomena, which become very complicated in the ternary-composite system. We assumed that the friction-induced thermal and mechanical effects were dominated in the frictional process of PEKKrGF composites. These effects diminished in the PEKKrGFrmica system as a result of reduced detachment of fillers from polymer, since addition of mica into the materials led to improved distribution of the fillers due to the small particles’ capability of locating around big particles, as observed by the tensile tests. SEM was used to examine the morphologies of these materials ŽFig. 2.. As expected, pure PEKK had a relatively smooth morphology on the fractured surface ŽFig. 2Ža... Upon addition of GFrmica to PEKK, the morphologies of the fractured composites changed dramatically, and a very rough surface was observed ŽFig. 2Žb... It was hard to discern the planar-shaped micas from the polymer matrix, but GF could be clearly seen from the image. A thin layer of polymer, indicating strong interfacial adhesion between fillers and PEKK, covered the pulledout GF. It was interesting to note that the GF oriented in one direction, which could be the flow direction during injection. The fractured surface did not show large voids or microcracks, confirming the assumption of the tensile tests and frictional behavior that the fine-grained particles were located among
123
Fig. 2. SEM of cryogenically fractured surface for Ža. PEKK and Žb. PEKKrGFrmica composites Žweight ratios 70:15:15..
big particles. This was the reason why partial replacement of GF with mica as fillers resulted in enhanced mechanical strength and reduced coefficient of friction and wearing loss.
4. Summary In summary, PEKK composites filled with combining fillers of GF and mica were studied for the purpose of possibly reducing costs and maintaining mechanical properties of the materials. Keeping the total fillers constant at 30 wt%, partial replacement of GF with mica, at an appropriate ratio, improved the mechanical properties of the composites. The composition of the fillers also affected the frictional behavior of the composites. SEM confirmed the assumption that the finely ground particles were able to locate around big particles, leading to improved
124
D. Gan et al.r Materials Letters 51 (2001) 120–124
mechanical properties of the PEKKrGFrmica ternary composites.
References w1x L.E. Nielsen, Mechanical Properties of Polymers and Composites, vol. 1, Marcel Dekker, New York, 1974. w2x O.B. Searle, R.H. Pfeiffer, Polym. Eng. Sci. 25 Ž1985. 474. w3x M. Cakmak, Plast. Eng. ŽN. Y.. 41 Ž1997. 931. w4x P. Davies, C.J.G. Plummer, Adv. Thermoplast. Compos. 1 Ž1993. 141. w5x D.P. Jones, D.C. Leach, D.R. Moore, Polymer 26 Ž1985. 1385. w6x H.X. Nguyen, H. Ishida, Polym. Compos. 8 Ž1987. 57. w7x S. Nilsson, NTIS Report ŽFFA-TN-1988-37, ETN-89-94545. Ž1988., 55 pp. w8x J.B. Rose, Polym. Prepr. 27 Ž1986. 480.
w9x J.C. Seferis, Polym. Compos. 7 Ž1986. 158. w10x S. Khan, J.F. Pratte, I.Y. Chang, W.H. Krueger, Int. SAMPE Symp. Exhib. 35 Ž1990. 1579. w11x K. Friedrich, J. Karger-Kocsis, Z. Lu, Wear 148 Ž1991. 235. w12x M. Fenton, G. Hawley, Polym. Compos. 3 Ž1982. 218. w13x O.R. Hughes ŽHoechst Celanese, USA., WO9641836 Ž1996., 27 pp. w14x D. Gan, S. Lu, C. Song, Z. Wang, Mater. Lett. 48 Ž2001. 299. w15x M.-Z. Cai, C.-S. Song, D.-J. Gan, S.-R. Sheng, L.-Y. Zhou, Gaofenzi Cailiao Kexue Yu Gongcheng 16 Ž2000. 36. w16x C. Song, M. Cai, L. Zhou, Gaofenzi Xuebao 11 Ž1995. 99. w17x Z. Qiu, Z. Mo, Y. Yu, H. Zhang, S. Sheng, C. Song, J. Appl. Polym. Sci. 77 Ž2000. 2865. w18x A.A. Berlin, S.A. Volfson, N.S. Enikolopian, S.S. Negmatov, Principles of Polymer Composites, Springer, Berlin, 1986. w19x P.A. Jarvela, P.K. Jarvela, J. Mater. Sci. 31 Ž1996. 3853. w20x F.P. Bowden, D. Tabor, Friction and Lubrication of Solid: Part 2, Clarendon, Oxford, 1964.
Materials Letters 51 Ž2001. 120–124 www.elsevier.comrlocatermatlet
Mechanical properties and morphologies of poly žether ketone ketone/ rglass fibersrmica ternary composites Daoji Gan ) , Wenjing Cao, Caisheng Song, Zhijian Wang Department of Materials Science and Engineering, Nanchang Institute of Technology, Nanchang, Jiangxi 330034, People’s Republic of China Received 9 January 2001; accepted 12 January 2001
Abstract PolyŽether ketone ketone. ŽPEKK. composites were developed using glass fibers ŽGF. and mica as combining fillers. For the composites having 30 wt% of the total fillers, the highest tensile strength was observed at the filler containing ca. 50 wt% of mica. Partial replacement of GF with mica resulted in reduced coefficient of friction and wearing rate of the materials. The fractured surface of the composites did not have large voids and microcracks. q 2001 Elsevier Science B.V. All rights reserved. Keywords: PolyŽether ketone ketone.; Composites; Mechanical properties; Frictional behavior
1. Introduction Many commercial polymer materials are composites, since they provide reduced costs and improved thermal, mechanical and electrical properties that cannot be obtained from simple polymers. A great variety of the physical properties can be obtained through alternating compositions of the polymer composites w1x. PolyŽaryl ether ketones. ŽPAEK., as a type of high-performance polymers, have found many applications in aerospace, coating and insulating material fields w2–8x. Reinforcement of PAEK with carbon or glass fibers could result in significant ) Corresponding author. Present address: School of Chemistry and Biochemistry, Georgia Institute of Technology, 770 State St., Atlanta, GA 30332, USA. Tel.: q1-404-367-8645; fax: q1-404894-7452. E-mail address: [email protected] ŽD. Gan..
improvement of the physical, mechanical and frictional properties w6,9–11x. Mica, due to its excellent mechanical, electrical and thermal properties, has been widely used as reinforcing filler in polymeric matrices, such as polyolefins, polyesters, polyamides, epoxies and polyurethanes w12x. However, there are few reports on the PAEK composites filled with mica w13x. Previously, we investigated the PAEK composites filled with different contents of mica w14x. Increased rigidity of the materials was observed as a function of mica amounts, while the highest mechanical strength could be obtained at a particular content of mica. Here, we report the preparation of the PEKK composites with combining fillers of glass fibers and mica. The goals are to maintain the mechanical property and to reduce the cost of the composites, since micas are much cheaper than glass fibers. Therefore, the effects of filler ratios on the mechani-
00167-577Xr01r$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 7 - 5 7 7 X Ž 0 1 . 0 0 2 7 6 - 2
D. Gan et al.r Materials Letters 51 (2001) 120–124
cal and frictional properties of the materials were examined. 2. Experimental PolyŽether ketone ketone. ŽPEKK, Scheme 1., synthesized via polycondensation of diphenyl ether with terephthaloyl chloride ŽTPC.risophthaloyl chloride ŽIPC. Žmolar ratio: 0.7:0.3. in the presence of AlCl 3 and 1,2-dichloroethanerdimethylformamide ŽDMF. w15,16x, has a glass transition temperature ŽTg . at 1608C and a reduced viscosity Žhinh . of 0.95. The phlogopite-type mica used here has an average diameter larger than 50 mm. The glass fibers ŽGF. are chopped strands, which have the average length of 3–6 mm. Before using, both mica and GF were coated with a thin layer of sulfonated polyŽether ketone ketone. ŽS-PEKK. through immersion in 2 wt% S-PEKKrDMF solution, as described previously w14x. Mica and GF were first mechanically ground and mixed by a miller. PAEK and fillers, at appropriate ratio, were blended in a Brabender Plastic-corder Model PLE 330 at 3808C. A rotation speed of 70 rpm was maintained for 12 min to get finely dispersed composites, which were then compressed, at 1658C, in molds to get the specimen sheets. The specimens were heated on a steel stage at 3508C for a short time and dropped immediately into ice water to yield amorphous glassy samples, which was demonstrated by the disappearance of the crystallization peak during differential scanning calorimetry ŽDSC. measurements w17x. An instron machine, Model 5583 ŽInstron, Canton, MA, USA., having a video-monitored optical extensometer, was used to measure the mechanical properties. The specimen films, ca. 2-mm thick and cut into a dumbbell shape using a die, were tested at room temperature with a crosshead rate of 2 mmrmin, according to ASTM D-638. Tensile modulus was calculated from the initial slope of the stress–strain curve, while both the tensile strength and elongation were the values at the breaking point.
Scheme 1. Structure of polyŽether ketone ketone. ŽPEKK..
121
Sliding friction and wearing loss were determined using a China-made MZ 200 friction-and-wear tester under ambient environment at a sliding speed of 0.5 mrs. The specimens Žrectangular dimension: 30 = 7 = 9 mm. were held by a loading arm, which recorded the friction force Ž Ff .. Coefficient of friction Ž m . was calculated by m s FfrFn , where Fn is the normal loading force used in the test. The weight of the specimens before and after the test was determined and converted into volume using their density. Wearing rate ŽWs . was calculated by Ws s Ž V0 y V1 . r Ž Fn = L .
mm3r Ž N m .
where V0 is the volume of the sample before the test, V1 is the volume after the test, and L is the sliding distance. For the tensile tests and sliding friction measurements, the data shown here are the average values of six replicated tests. The cryogenically fractured surfaces of the specimens were examined by a JEOL 6300 scanning electron microscope ŽSEM.. Before the experiment, the surfaces were coated with a thin layer of gold.
3. Results and discussion To optimize the appropriate ratio of fillers, the mechanical properties of the composites filled with a single filler of GF were first investigated. With the increase of GF content in the materials, tensile modulus increased, ultimate elongation decreased, while tensile strength exhibited a maximum value at a weight ratio of ; 30% GF used ŽTable 1.. This could be attributed to the counterbalance of increased surface fracture energy and increased sizes of voids or GF aggregates as GF contents in the polymer composites increased w1,18x. Since dispersed GF in the composites made the crack propagation path longer, absorbed a portion of the energy and enhanced the plastic deformation, the surface fracture energy of the materials increased and the strength of the composites should increase as well, as a function of GF contents w18x. However, with the increase of the GF contents, the size of the voids due to the detachment of PEKK from GF gradually increased, and might initiate, the main crack w18x. In addition, the inevitably increased agglomeration of dispersed filler particles resulted in decreased me-
D. Gan et al.r Materials Letters 51 (2001) 120–124
122
Table 1 Tensile properties of PEKK and its compositesa Composition Žweight. PEKKrGF
Modulus ŽGPa. b
PEKKrGFrmica
Value
S.D.
70:25:5 70:20:10 70:15:15 70:10:20 70:5:25 70:0:30
4.20 5.64 8.45 12.57 13.53 13.94 14.08 14.85 16.08 16.89 17.25 18.14
0.81 0.32 0.15 0.84 0.95 0.97 1.23 0.23 0.27 0.32 0.21 0.74
100:0 95:5 90:10 80:20 70:30 60:40
Strength ŽMPa. c e
Value
S.D.
102.0 130.2 175.4 200.3 215.1 195.6 220.9 230.2 235.5 222.1 210.3 180.4
3.9 0.8 1.3 2.2 1.1 1.9 2.3 1.1 2.0 1.5 1.9 3.0
Elongation Ž%. d e
Value
S.D.e
62.1 51.0 40.1 18.3 7.5 3.2 6.0 6.7 7.1 5.2 4.8 4.0
2.5 1.2 0.8 1.1 0.7 1.2 0.5 0.4 0.5 0.2 0.3 0.6
a
Average value of six replicated measurements. Tensile modulus. c Tensile strength. d Ultimate elongation. e Standard deviation. b
chanical strength because of the low strength of the agglomerates themselves w1x. Since the composites containing 30 wt% of GF exhibited the highest tensile strength in our examination, the total filler content in the composites afterwards was kept constant at 30 wt%, and mica was used to gradually replace GF ŽTable 1.. The tensile modulus of the composites increased with the increasing replacement of GF by mica that has a higher modulus than GF. Interestingly, the highest tensile strength and ultimate elongation were obtained at a point where 50 wt% of GF were replaced by mica. Many factors, such as the properties and distribution of fillers, the morphology of the system and the nature of the interface between phases, affect the properties of polymer composites. In general, the composites containing two or more fillers, due to the existence of large voids and inhomogeneous distribution of fillers in the system, exhibit reduced mechanical properties in comparison with those containing single-component fillers w18x. The improved mechanical properties, in our case, may be explained by the fact that GF and mica tended to move and orient in different ways in the process of melt blend, while the fine-grained particles were capable of locating among the large particles, and even facilitating, the melt flow. The same phenomenon was found in polypropylene composites w19x.
Frictional properties of these materials were measured using a friction-and-wear tester. A normal loading force of 100 N was used in the measurements, since there would be no significant difference in the frictional properties if the normal loading force smaller than 60 N was used in the tests. The frictional properties of the materials as a function of GFrmica are shown in Fig. 1. Addition of GF to the polymer led to the increase of frictional coefficient and wearing rate, while replacement of GF with mica
Fig. 1. Frictional properties of PEKK and its composites measured under a normal loading force of 100 N.
D. Gan et al.r Materials Letters 51 (2001) 120–124
resulted in reduced coefficient of friction and wearing rate. The frictional behavior of polymer composites is determined by both components, rigid particles and deformable polymers, which are interactive during the frictional process. The coefficient of friction and wearing rate are directly proportional to the real contact area, which decreases with the increasing modulus of the materials in a given system w20x. Therefore, both GF and mica are efficient components to reduce the coefficient of friction and wearing rate of polymer composites, given the increased modulus of the polymer composites, as observed by the tensile tests. However, as fillers are added to polymer, the friction-induced thermal and mechanical effects inevitably increase, which results in enhanced softening and plastic deformation of polymer as well as detachment of the filler from polymer matrix, leading to the increase of frictional coefficient and wearing rate of the materials w20x. The final frictional behavior of the resulted materials depends on the balance of these two phenomena, which become very complicated in the ternary-composite system. We assumed that the friction-induced thermal and mechanical effects were dominated in the frictional process of PEKKrGF composites. These effects diminished in the PEKKrGFrmica system as a result of reduced detachment of fillers from polymer, since addition of mica into the materials led to improved distribution of the fillers due to the small particles’ capability of locating around big particles, as observed by the tensile tests. SEM was used to examine the morphologies of these materials ŽFig. 2.. As expected, pure PEKK had a relatively smooth morphology on the fractured surface ŽFig. 2Ža... Upon addition of GFrmica to PEKK, the morphologies of the fractured composites changed dramatically, and a very rough surface was observed ŽFig. 2Žb... It was hard to discern the planar-shaped micas from the polymer matrix, but GF could be clearly seen from the image. A thin layer of polymer, indicating strong interfacial adhesion between fillers and PEKK, covered the pulledout GF. It was interesting to note that the GF oriented in one direction, which could be the flow direction during injection. The fractured surface did not show large voids or microcracks, confirming the assumption of the tensile tests and frictional behavior that the fine-grained particles were located among
123
Fig. 2. SEM of cryogenically fractured surface for Ža. PEKK and Žb. PEKKrGFrmica composites Žweight ratios 70:15:15..
big particles. This was the reason why partial replacement of GF with mica as fillers resulted in enhanced mechanical strength and reduced coefficient of friction and wearing loss.
4. Summary In summary, PEKK composites filled with combining fillers of GF and mica were studied for the purpose of possibly reducing costs and maintaining mechanical properties of the materials. Keeping the total fillers constant at 30 wt%, partial replacement of GF with mica, at an appropriate ratio, improved the mechanical properties of the composites. The composition of the fillers also affected the frictional behavior of the composites. SEM confirmed the assumption that the finely ground particles were able to locate around big particles, leading to improved
124
D. Gan et al.r Materials Letters 51 (2001) 120–124
mechanical properties of the PEKKrGFrmica ternary composites.
References w1x L.E. Nielsen, Mechanical Properties of Polymers and Composites, vol. 1, Marcel Dekker, New York, 1974. w2x O.B. Searle, R.H. Pfeiffer, Polym. Eng. Sci. 25 Ž1985. 474. w3x M. Cakmak, Plast. Eng. ŽN. Y.. 41 Ž1997. 931. w4x P. Davies, C.J.G. Plummer, Adv. Thermoplast. Compos. 1 Ž1993. 141. w5x D.P. Jones, D.C. Leach, D.R. Moore, Polymer 26 Ž1985. 1385. w6x H.X. Nguyen, H. Ishida, Polym. Compos. 8 Ž1987. 57. w7x S. Nilsson, NTIS Report ŽFFA-TN-1988-37, ETN-89-94545. Ž1988., 55 pp. w8x J.B. Rose, Polym. Prepr. 27 Ž1986. 480.
w9x J.C. Seferis, Polym. Compos. 7 Ž1986. 158. w10x S. Khan, J.F. Pratte, I.Y. Chang, W.H. Krueger, Int. SAMPE Symp. Exhib. 35 Ž1990. 1579. w11x K. Friedrich, J. Karger-Kocsis, Z. Lu, Wear 148 Ž1991. 235. w12x M. Fenton, G. Hawley, Polym. Compos. 3 Ž1982. 218. w13x O.R. Hughes ŽHoechst Celanese, USA., WO9641836 Ž1996., 27 pp. w14x D. Gan, S. Lu, C. Song, Z. Wang, Mater. Lett. 48 Ž2001. 299. w15x M.-Z. Cai, C.-S. Song, D.-J. Gan, S.-R. Sheng, L.-Y. Zhou, Gaofenzi Cailiao Kexue Yu Gongcheng 16 Ž2000. 36. w16x C. Song, M. Cai, L. Zhou, Gaofenzi Xuebao 11 Ž1995. 99. w17x Z. Qiu, Z. Mo, Y. Yu, H. Zhang, S. Sheng, C. Song, J. Appl. Polym. Sci. 77 Ž2000. 2865. w18x A.A. Berlin, S.A. Volfson, N.S. Enikolopian, S.S. Negmatov, Principles of Polymer Composites, Springer, Berlin, 1986. w19x P.A. Jarvela, P.K. Jarvela, J. Mater. Sci. 31 Ž1996. 3853. w20x F.P. Bowden, D. Tabor, Friction and Lubrication of Solid: Part 2, Clarendon, Oxford, 1964.