Effect of Entanglement Density on Mechanical Properties and

Aug 2, 2013 - Effect of Entanglement Density on Mechanical Properties and Deformation Behavior of Rubber-Modified PVC/α-MSAN Blends. Lixin Song†‡...
0 downloads 0 Views 2MB Size
Download PDF
Article pubs.acs.org/IECR

Effect of Entanglement Density on Mechanical Properties and Deformation Behavior of Rubber-Modified PVC/α-MSAN Blends Lixin Song,†,‡ Liang Ren,§ Mingyao Zhang,§ Sulin Sun,§ Guanghui Gao,§ Yu Gui,§ Lixia Zhang,§ and Huixuan Zhang*,†,§ †

Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China Graduate University of Chinese Academy of Sciences, Beijing 100049, China § Engineering Research Centre of Synthetic Resin and Special Fiber, Ministry of Education, and School of Chemical Engineering, Changchun University of Technology, Changchun 130012, China ‡

ABSTRACT: Miscible blends of poly(vinyl chloride) (PVC)/poly(α-methylstyrene-acrylonitrile) (α-MSAN) were toughened by polybutadiene-g-poly(styrene-co-acrylonitrile)(PB-g-SAN). The PB-g-SAN content was fixed at 20%, and the ratio of PVC to α-MSAN ranged from 100/0 to 0/100 in the matrix. The dependence of mechanical properties and deformation mechanisms on the entanglement density of rubber-modified PVC/α-MSAN blends was investigated. It was found that the entanglement density of PVC/α-MSAN blends increased with increasing of PVC content. When the entanglement density of the matrix was low, crazing was the main deformation mechanism. For the matrix with high entanglement density, crazing, cavitation, and shear yielding took place simultaneously. On further increasing the entanglement density, only cavitation and shear yielding of the matrix were observed. Therefore, a transition from crazing to shear deformation was observed with the increase of entanglement density in the matrix, leading to higher toughness.

■

INTRODUCTION Toughness is an important property for rubber-modified plastics when they are used as structural materials. To date, enhancing the toughness of high-performance materials has attracted great interest. Therefore, great efforts have been made toward developing effective toughening methods for amorphous polymers. The most effective solution so far is to blend brittle polymers with rubber particles.1 It can introduce extensive plastic deformation into the fracture process of the material, thereby increasing the toughness of polymers effectively. Numerous rubber-modified polymer blends and composite systems have been developed to improve the toughness.2−11 Three kinds of toughening mechanisms, crazing, interfacial cavitation between the rubber particles and the matrix or the internal cavitation within the rubber particles, and shear yielding, have been found in rubber-toughened polymeric materials. In a given condition, the impact energy may be dissipated by crazing, shear yielding, or both.2,12 Kramer and Henkee suggested that the fundamental processes of craze growth were molecular disentanglement of the network and chain scission.13−15 They also explained the competition between crazing and shear deformation. The highly entangled polymers tended to shear, while relatively less entangled polymers underwent crazing. Wu pointed out that a polymer having low entanglement density tended to craze rather than yield. On the other hand, a polymer having high entanglement density tended to yield rather than craze.16 Many researchers focused on the transition of deformation mechanisms in polymers. Kramer et al. studied the crazing and shear deformation in cross-linked polystyrene.15,17,18 They found that there was a change in deformation mode from crazing to shear that took place with an increase of the network © 2013 American Chemical Society

strand density. Donald examined the craze-to-shear transition in monodisperse polystyrene as a function of temperature and reported that PS exhibited a transition from crazing to shear deformation as the temperature of deformation was increased.19 Weidish et al. studied the deformation of PS-PBMA star block polymer.20 They found that a transition from crazing to shear deformation was initiated by a change from diblock to star block architecture. Gensler et al. investigated the fracture behavior of an isotactic polypropylene.21 They pointed out that the homopolymer displayed a brittle−ductile transition as the test speed was increased, which was associated with a transition from crazing to shear deformation. Lee et al. studied the thin film deformation behavior of PET homopolymer.22 They pointed out that a transition from crazing to localized shear deformation occurred as the content of cyclohexylene linkage increased. PVC is subjected to some limitations in certain applications due to its low notched impact strength and heat distortion temperature (HDT). To solve these problems at the same time, both α-MSAN copolymer and toughening modifier (PB-gSAN) were introduced in our work to produce a ternary blends which was combined with high toughness and high HDT. αMSAN has a higher glass-transition temperature compared with that of pure PVC,23−25 indicating that addition of α-MSAN could improve the HDT of PVC but the embrittle rigid PVC. PB-g-SAN added into PVC/α-MSAN binary blends could increase the toughness. Received: Revised: Accepted: Published: 12567

March 21, 2013 July 16, 2013 August 2, 2013 August 2, 2013 dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

Entanglement Density. The storage shear modulus of neat PVC/α-MSAN blends was determined in the melt as a function of the angular frequency (10−1−102 rad/s) for at least six different temperatures over a range of 70 °C using AR 2000EX Rheometer. A plate−plate geometry was used (diameter 25 mm) at a maximum strain of 2%. The thickness of the samples was 1 mm. According to the classical concept of rubber elasticity theory, the molecular weight between entanglement nodes, Me, could be calculated37,38

For PVC/α-MSAN blends, the miscibility, thermal properties, and mechanical properties have been investigated by many researchers.26−32 However, to our knowledge, few studies have been reported previously on the deformation behavior of rubber-modified PVC/α-MSAN blends.33,34 Hence, there is a need for a systematic study on the deformation mechanisms of the blend. The goal of the present paper is to design rubbermodified PVC/α-MSAN blends with desired properties for various applications based on the understanding of the deformation mechanisms. The influence of entanglement density on the mechanical properties and deformation behavior of rubber-modified PVC/ α-MSAN blends was studied in detail. It is generally accepted that PVC and α-MSAN are miscible over the entire composition range, and they exhibit a single Tg value.23,24 αMSAN possesses a low entanglement density, PVC possesses a high entanglement density,35 and the entanglement density can be varied by adjusting the relative volume fractions of both constituents.36 In this paper, the mechanical properties of the blends, both impact strength and tensile strength, were investigated. The microscopic morphology was observed by SEM and TEM to elucidate the deformation mechanisms.

Me = ρRT /G N0

where ρ is the density, R is the gas constant, and T is the reference temperature. Shifting of the G′ versus w curves to reference temperature, approximately 40 °C above the glass-transition temperature, resulted in a master curve. The rubber plateau modulus GN0 is equal to the storage modulus G′ at the frequency where tan δ is at its minimum in the plateau zone of the master curve.39,40 Then the entanglement density (νe) can be calculated as follows41

■

νe = ρNA /Me

EXPERIMENTAL SECTION Materials. PVC resin (SG-5, K = 66) and PB-g-SAN (the size of the rubbery particles was 300 nm, weight ratio of polybutadiene to acrylonitrile−styrene copolymer (PB/SAN) was 60/40, and weight ratio of styrene to acrylonitrile (St/AN) was 75/25) were obtained from Jilin Petrochemical Co., China. The α-MSAN with 30 wt % acrylonitrile was obtained from General Electric Co. The lead sulfate and calcium stearate were supplied by Wenzhou Plastic Assistant Factory, China. Blend Preparation. Blends with different weight ratios were prepared in a two-roll mill (Shanghai Rubber Machinery Works, China) at 180 °C for 5 min together with 2 wt % lead sulfate and 1 wt % calcium stearate as stabilizer and lubricant, respectively. Prepared blends were compression molded into sheets of 1 and 4 mm thickness at 180 °C in a flat-plate vulcanization machine (Qingdao Huabo Machinery S&T Co., Ltd., China). Compressed sheets, with 1 mm thickness, were cut into dumbbell-shaped test pieces with a die for tensile testing. Rectangular samples with 4 mm thickness were shaped with a universal clipper for impact tests. Compositions of rubber-modified PVC/α-MSAN blends are summarized in Table 1.

blend blend blend blend blend

1 2 3 4 5

PB-g-SAN content (wt %)

PVC/α-MSAN content (wt %)

composition of PVC/ α-MSAN

20 20 20 20 20

80 80 80 80 80

0/100 25/75 50/50 75/25 100/0

(2)

where NA is Avogadro’s number. Values of νe for the various PVC/α-MSAN compositions are calculated by combining eqs 1 and 2. Mechanical Properties. According to ASTM D256, notched impact strength was determined with a XJU-22 impact tester at the maximum speed of 3.5 m/s with specimen dimension 63.5 × 12.7 × 4 mm. Tensile properties were measured according to ASTM D638 using a Instron-1121 Electrical Testing Machine at a cross-head speed of 50 mm/ min. The test was performed at room temperature, and the average values of at least five tests were reported. Scanning Electron Microscopy (SEM) Analysis. The fracture surface and stress-whitening zone of the blends in the Izod impact tests were observed using a JSM-6510 SEM instrument. Specimens were prepared by cryogenically splitting the impact tested samples; the cryogenic fracture surface was perpendicular to the impact fracture surface and passed through the stress-whitening zone. Transmission Electron Microscopy (TEM) Analysis. Microstructure morphologies of the blends were observed using a JEM-1011 TEM instrument. Specimens were cut to 60 nm thickness using a microtome at −100 °C and stained for 8 h by exposing the ultrathin sections in the vapor of 1% OsO4 solution before observation.

Table 1. Compositions of Rubber-Modified PVC/α-MSAN Blends sample

(1)

■

RESULTS AND DISCUSSION Entanglement Density of PVC/α-MSAN Blends. DMA curves of PVC/α-MSAN blends are shown in Figure 1. Only a single Tg was observed for all blends. The result was in clear agreement with early reports,23,24 indicating that PVC and αMSAN were miscible in all ranges of compositions. The rheological properties of PVC/α-MSAN blends were recorded with AR 2000EX Rheometer. Master curves of the blends are shown in Figure 2. The temperatures to which the master curves were shifted 175, 165, 155, 145, and 125 °C (Tg +40 °C) for the different PVC compositions of PVC/α-MSAN blends. It was clearly found in Figure 2 that an increase of PVC content in the PVC/α-MSAN blends resulted in a shift of the G′ curve to higher values.

Glass-Transition Temperature. Dynamic mechanical analysis was performed by the Perkin-Elmer DMA-S II at a frequency of 10 Hz in extension mode. Dimensions of the specimens for testing were 30 × 10 × 1 mm. Scans were carried out from 50 to 200 °C at a heating rate of 3 °C/min. 12568

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

Figure 3, the entanglement density of PVC/α-MSAN blends increases linearly with the increase of PVC content. Modifier Particles Dispersion. The phase morphology of rubber-modified PVC/α-MSAN blends is observed in Figure 4.

Figure 1. Dynamic mechanical date for neat PVC/α-MSAN blends with varied composition.

Figure 2. Master curves of G′ for the PVC/α-MSAN blends as a function of the weight fraction of PVC. Figure 4. Dispersion of PB-g-SAN in PVC/α-MSAN matrix with different ratios of PVC to α-MSAN: (a) 0/100, (b) 25/75, (c) 50/50, (d) 75/25, (e) 100/0.

In Figure 3 the value of the entanglement density is plotted versus the PVC/α-MSAN composition. As can be inferred from

The dispersion of rubber particles in the matrix was not significantly influenced by the change of PVC/α-MSAN ratio. There was no sign of severe agglomeration in a wide range of PVC levels. It has been reported by Kim et al. that SAN was miscible with PVC in the 12−26 wt % AN and immiscible outside this range.42 In our experiment, the SAN shell in PB-gSAN with 25 wt % AN was miscible with PVC and a strong interfacial adhesion between the shell and the PVC/α-MSAN matrix could be obtained. Thus, it can be easily understood that the rubber particles are relatively evenly distributed into the PVC/α-MSAN matrix. Mechanical Properties. Impact strength testing is one of the most widely used methods for investigating polymer toughness as it gives information about the high-speed failure of materials. Figure 5 shows the notched Izod impact strength of the blends as a function of PVC content in the matrix for rubber-modified PVC/α-MSAN blends. With the increase of PVC content, the entanglement density increased, resulting in an obvious increase of the impact strength of the blends. The pure α-MSAN exhibited poor toughness with an impact

Figure 3. Entanglement density (νe) versus PVC content in PVC/αMSAN blends. 12569

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

Figure 7. Tensile stress−strain curves for rubber-modified PVC/αMSAN blends with different ratios of PVC to α-MSAN.

Figure 5. Impact strength of rubber-modified PVC/α-MSAN blends with different ratios of PVC to α-MSAN.

density of matrix in the rubber-modified PVC/α-MSAN blends. Similar results have been reported in previous literature.48−50 Wu investigated the relationship between the chain structure, phase morphology, and toughness in thermoplastic polymers and polymer/rubber blends.16 He pointed out that the toughing extent of rubber-modified matrix with the same rubber amount depended on the intrinsic brittleness and ductility of the matrix, as controlled by the entanglement density of matrix. The higher entanglement density induces the tougher polymer. In our work, therefore, when more PVC was introduced to the rubber-modified PVC/α-MSAN blends, the entanglement density of matrix increased, resulting in the toughness of blends improving significantly. Deformation Mechanism. In toughened thermoplastics, the toughening mechanism is characterized by the fracture surface and stress-whitening zone of the blend according to the impact conditions. SEM micrographs of the impact-fractured surface of rubbermodified PVC/α-MSAN blends are shown in Figure 8. Clear differences of deformation were observed. As seen in Figure 8a, the facture surface of the pure α-MSAN system was flat and clear cut, implying the brittle fracture under impact load. With incorporation of 25 wt % PVC (see Figure 8b), a rough and coarse surface with some domain distortions was observed, which revealed an improvement in toughness. With the increase of PVC content (see Figure 8c), the surface was highly deformed and some fibrils and cavities were observed in the matrix, indicating that a higher toughness was obtained. With a further increase of PVC content (see Figure 8d and 8e), massive cavities with plastic flow occurred on the fracture surface, which could give rise to excellent improvement in toughness. All results of morphology correlated well with the impact strengths of rubber-modified PVC/α-MSAN blends. In order to determine the relationship between the morphology of the surface and the internal yielding zone, the stress-whitening zone was observed using SEM and TEM. Figure 9 shows SEM figures on the cryo-fractured surface of rubber-modified PVC/α-MSAN blends. In the α-MSAN-rich system (see Figure 9a), some cavities were observed but most of them were close to the initial rubber particle in size. It was considered as the trails of rubber particles that were pulled out from the matrix. With the increase of PVC content in the matrix (see Figure 9b), more cavities occurred in the rubber particles. The size of the cavities in the region was larger than

strength of 29 J/m. However, the impact strength was boosted to 981 J/m with addition of 75 wt % PVC. It meant that the increase of entanglement density could evidently improve the toughness of rubber-modified PVC/α-MSAN blends. The phenomenon of stress whitening is well known to occur in rubber-modified thermoplastics when specimens are deformed during high stresses. Whitening is the result of void formation (particle−matrix interface detachment) and/or deformation.1,43−46 The extent of stress whitening in impact specimens with different matrix composition is shown in Figure 6. It was evident that at the low entanglement density stress

Figure 6. Stress-whitened zones of impact sample of rubber-modified PVC/α-MSAN blends with different ratios of PVC to α-MSAN: (a) 0/ 100, (b) 25/75, (c) 50/50, (d) 75/25, (e) 100/0.

whitening hardly occurred, while at high entanglement density stress whitening obviously generated. The extent of stress whitening increased with the entanglement density in the matrix of the blends. All results were in clear agreement with the impact strength of the blends. It is known that toughness enhancement of brittle amorphous polymers can be obtained via microstructural adjustments, resulting effectively in removal of intrinsic strain softening via a decrease in yield stress.47 The stress−strain curves of rubber-modified PVC/α-MSAN blends are given in Figure 7. It was found that the increase of the PVC content in PVC/α-MSAN resulted in an obvious decrease of tensile strength and a continuous increase of elongation at break, which indicated that strain softening was suppressed due to the increase of PVC content and the toughness of the blends was improved. All these attribute to the change of the entanglement 12570

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

Figure 9. SEM photographs of stress-whitening zone in rubbermodified PVC/α-MSAN blends under impact test with different ratios of PVC to α-MSAN: (a) 25/75, (b) 50/50, (c) 75/25, (d) 0/100.

entanglement density. With the increase of entanglement density (α-MSAN-rich system), as shown in Figure 10b, some voids formation by cavitation or debonding were seen and some particles elongated, indicating that the shear deformation occurred in the matrix. Usually, it was believed that both internal cavitation of the rubber particles and debonding at the particle/matrix interface relieve the triaxial tension and thereby promote shear yielding of the matrix, leading to ductile behavior.52−54 Besides, a few crazes could be observed in the blends. It suggested that at higher entanglement density both crazes and shear yielding coexisted. With further increasing of entanglement density (intermediate composition and PVC-rich system), as shown in Figure 10c−e, there was no evidence of crazing; the matrix deformed only by shear deformation. Massive rubber particles cavitated or debonded at the particle/ matrix interface, and all particles were elongated by the shear of the matrix. It has been considered that the change of deformation mechanism in the rubber-modified PVC/αMSAN blends was governed by the entanglement density of the matrix. Combining the results from SEM and TEM, the transition of the deformation mechanism took place with the increase of entanglement density in rubber-modified PVC/α-MSAN blends, which was transferred from crazing to shear yielding.

Figure 8. SEM photographs of fracture surface of rubber-modified PVC/α-MSAN blends under impact test with different ratios of PVC to α-MSAN: (a) 0/100, (b) 25/75, (c) 50/50, (d) 75/25, (e) 100/0.

that of the undeformed rubber particles. With further addition of PVC (see Figure 9c and 9d), massive cavities were observed in the matrix. Most of the cavities in the stress-whitening zone were several times larger than the original rubber particle, and several rubber particles can be observed in one hole. Therefore, it was a reasonable assumption that the coalescence of neighboring cavities initiated by individual particles must have occurred, and the cavities became elongated, which indicated that shear deformation took place. Pearson et al. suggested that cavitation could occur inside the rubber particles or at the interface between the rubber particles and the polymer matrix, which played an important role for the toughness improvement of rubber-dispersed polymers.51 The internal morphology of the stress-whitening zone in the impact specimen of rubber-modified PVC/α-MSAN blends was studied by TEM (shown in Figure 10). At lower entanglement density (for example, pure α-MSAN), as shown in Figure 10a, the black crazes were shown clearly against the white background of the undeformed matrix. It was shown that the crazes were initiated from the rubber particles, and the propagation direction of crazes was orthogonal to the deformation direction. In addition, the crazes also could be terminated by the rubber particles. There was no sign of elongation of the rubber particles. It suggested that the main deformation mechanism was crazing when the matrix has low

■

CONCLUSIONS Rubber-modified PVC/α-MSAN blends with different compositions were prepared by melt blending. The entanglement density of the matrix varied linearly between the values of pure α-MSAN and pure PVC. The dependence of deformation mechanisms and mechanical properties on the entanglement density of rubber-modified PVC/α-MSAN blends was investigated. It was found that when the entanglement density of the matrix was low, the blend showed a brittle fracture and crazing was the main deformation mechanism. When the entanglement density was high, the blend fractured in a ductile manner and 12571

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

(4) Gebizlioglu, O. S.; Beckham, H. W.; Argon, A. S.; Cohen, R. E.; Brown, H. R. A new mechanism of toughening glassy polymers.1.Experimental procedures. Macromolecules 1990, 23, 3968. (5) Kim, H.; Keskkula, H.; Paul, D. R. The role of inherent ductility in rubber toughening of brittle polymers. Polymer 1991, 32, 2372. (6) Huang, J. J.; Keskkula, H.; Paul, D. R. Rubber toughening of an amorphous polyamide by functionalized SEBS copolymers: morphology and Izod impact behavior. Polymer 2004, 45, 4203. (7) Sun, S. L.; Xu, X. Y.; Yang, H. D.; Zhang, H. X. Toughening of poly(butylene terephthalate) with epoxy-functionalized acrylonitrilebutadiene-styrene. Polymer 2005, 46, 7632. (8) Bucknall, C. B.; Paul, D. R. Notched impact behavior of polymer blends: Part 1: New model for particle size dependence. Polymer 2009, 50, 5539. (9) Liu, Z. G.; Deng, Y. J.; Han, Y.; Chen, M.; Sun, S. L.; Cao, C. L.; Zhou, C.; Zhang, H. X. Toughening of polyamide-6 with a maleic anhydride functionalized acrylonitrile-styrene-butyl acrylate copolymer. Ind. Eng. Chem. Res. 2012, 51, 9235. (10) Bucknall, C. B.; Paul, D. R. Notched impact behavior of polymer blends: Part 2: Dependence of critical particle size on rubber particle volume fraction. Polymer 2013, 54, 320. (11) Deng, Y. J.; Gao, G. H.; Liu, Z. G.; Cao, C. L.; Zhang, H. X. Cotoughened Polystyrene by Sub-micron Sized Core-shell Rubber Particles and Micron Sized Salami Rubber Particles. Ind. Eng. Chem. Res. 2013, 52, 5079. (12) Wu, S. Phase structure and adhesion in polymer blends: A criterion for rubber toughening. J. Polym. Sci., Part B: Polym. Phys. 1983, 21, 699. (13) Kramer, E. J. Craze fibril formation and breakdown. Polym. Eng. Sci. 1984, 24, 761. (14) Henkee, C. S.; Kramer, E. J. Loss of entanglement density during crazing. J. Mater. Sci. 1986, 21, 1398. (15) Henkee, C. S.; Kramer, E. J. Crazing and shear deformation in crosslinked polystyrene. J. Polym. Sci., Part B: Polym. Phys. 1996, 34, 2825. (16) Wu, S. Chain structure, phase morphology, and toughness relationships in polymers and blends. Polym. Eng. Sci. 1990, 30, 753. (17) Berger, L. L.; Kramer, E. J. The effect of temperature on the transition from crazing to shear deformation in crosslinked polystyrene. J. Mater. Sci. 1988, 23, 3536. (18) Miller, P.; Kramer, E. J. Environmental shear deformation zones and crazes in crosslinked polystyrene and poly(para-methylstyrene). J. Mater. Sci. 1990, 25, 1751. (19) Donald, A. M. The effect of temperature on crazing mechanisms in polystyrene. J. Mater. Sci. 1985, 20, 2630. (20) Weidisch, R.; Laatsch, J.; Michler, G. H.; Arnold, M.; Schade, B.; Fischer, H. Transition from crazing to shear deformation in star block copolymers. Macromolecules 2002, 35, 6585. (21) Gensler, R.; Plummer, C. J. G.; Grein, C.; Kausch, H. H. Influence of the loading rate on the fracture resistance of isotactic polypropylene and impact modified isotactic polypropylene. Polymer 2000, 41, 3809. (22) Lee, S. S.; Yee, A. F. Temperature-dependent transition of deformation mode in poly(1, 4-cyclohexylenedimethylene terephthalate)/poly(ethylene terephthalate) copolymers. Macromolecules 2003, 36, 6791. (23) Moon, H. S.; Choi, W. M.; Kim, M. H.; Park, O. O. Miscibility and rheological properties of poly(vinyl chloride)/styrene-acrylonitrile blends prepared by melt extrusion. J. Appl. Polym. Sci. 2007, 104, 95. (24) Moon, H. S.; Kim, M. H.; Park, O. O. Mechanical and thermal properties of poly(vinyl chloride)/α-methyl-styrene-acrylonitrile blends prepared by melt extrusion. J. Appl. Polym. Sci. 2009, 111, 237. (25) Zhang, Z.; Chen, S. J.; Zhang, J. A Study on Properties of poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile) Binary Blends. J. Macromol. Sci. B 2012, 51, 22. (26) Gan, P. P.; Paul, D. R.; Padwa, A. R. Phase behaviour of blends of homopolymers with α-methylstyrene/acrylonitrile copolymers. Polymer 1994, 35, 1487.

Figure 10. TEM photographs of stress-whitening zone in rubbermodified PVC/α-MSAN blends under impact test with different ratios of PVC to α-MSAN: (a) 0/100, (b) 25/75, (c) 50/50, (d) 75/25, (e) 100/0.

the main deformation mechanisms were cavitation and shear yielding of the matrix. During this process, there existed a transition in the deformation behavior from crazing to shear yielding with an increase of entanglement density of the matrix.

■

AUTHOR INFORMATION

Corresponding Author

*Tel: +86-43185716465. Fax: +86-43185716465. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

■ ■

ACKNOWLEDGMENTS We thank the Natural Science Foundation of China (No. 51073027). REFERENCES

(1) Bucknall, C. B. Toughened Plastics; Applied Science Publishers: London, 1977. (2) Donald, A. M.; Kramer, E. J. Plastic deformation mechanisms in poly(acrylonitrile-butadiene styrene) [ABS]. J. Mater. Sci. 1982, 17, 1765. (3) Fowler, M. E.; Keskkula, H.; Paul, D. R. Synergistic toughening in rubber modified blends. Polymer 1987, 28, 1703. 12572

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573

Industrial & Engineering Chemistry Research

Article

(27) Kim, J. H.; Barlow, J. W.; Paul, D. R. Phase behavior of blends of poly(vinyl chloride) with an α-methyl styrene/acrylonitrile copolymer. Polym. Eng. Sci. 1989, 29, 581. (28) Kim, C. H.; Park, J. K.; Hwang, T. S. Effect of intramolecular interactions on the miscibility windows of PVC blends with modified SAN copolymers. Polym. Eng. Sci. 1996, 36, 535. (29) Zhang, L. X.; Sun, S. L.; Li, X. W.; Zhang, M. Y.; Zhang, H. X. Effect of α-MSt content in α-MSAN copolymer on the miscibility of PVC/α-MSAN blends. Polym. Bull. 2008, 61, 99. (30) Zhang, L. X.; Sun, S. L.; Ren, L.; Zhang, F. F.; Zhang, M. Y.; Zhang, H. X. Effect of the composition of α-MSAN copolymer on the miscibility of PVC/α-MSAN blends. J. Appl. Polym. Sci. 2008, 108, 3016. (31) Zhang, Z.; Chen, S. J.; Zhang, J.; Li, B.; Jin, X. P. Influence of chlorinated polyethylene on poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile) blends: Mechanical properties, morphology and thermal properties. Polym. Test. 2010, 29, 995. (32) Zhang, Z.; Chen, S. J.; Zhang, J. Synergistic toughening effect of chlorinated polyethylene and ethylene-vinyl acetate copolymer on the poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile) blends via compatibilization. Polym. Test. 2011, 30, 534. (33) Zhang, Z.; Li, B.; Chen, S. J.; Zhang, J.; Jin, X. P. Poly(vinyl chloride)/poly(α-methylstyrene-acrylonitrile)/acrylic resin ternary blends with enhanced toughness and heat resistance. Polym. Adv. Technol. 2012, 23, 336. (34) Zhang, Z.; Chen, S. J.; Zhang, J. Blends of poly(vinyl chloride) with α-methylstyrene-acrylonitrile-butadiene-styrene copolymer: Thermal properties, mechanical properties, and morphology. J. Vinyl Addit. Technol. 2013, 19, 1. (35) Wu, S. Predicting chain conformation and entanglement of polymer from chemical structure. Polym. Eng. Sci. 1992, 32, 823. (36) Prest, W. M.; Porter, R. S. Rheological properties of poly(2, 6dimethylphenylene oxide)-polystyrene blends. J. Polym. Sci. (A-2) 1972, 10, 1639. (37) Ferry, J. D. Viscoelastic Properties of Polymers; Wiley: New York, 1980. (38) Graessley, W. W. The entanglement concept in polymer rheology. Adv. Polym. Sci. 1974, 16, 1. (39) Wu, S. Entanglement between dissimilar chains in compatible polymer blends: poly(methyl methacrylate) and poly(vinylidene fluoride). J. Polym. Sci., Part B: Polym. Phys. 1987, 25, 557. (40) Wu, S. Entanglement, friction, and free volume between dissimilar chains in compatible polymer blends. J. Polym. Sci., Part B: Polym. Phys. 1987, 25, 2511. (41) Kramer, E. J.; Berger, L. L. Fundamental processes of craze growth and fracture. Adv. Polym. Sci. 1990, 91/92, 1. (42) Kim, J. H.; Barlow, J. W.; Paul, D. R. Miscibility of poly(vinyl chloride) with styrene/acrylonitrile copolymers. J. Polym. Sci., Part B: Polym. Phys. 1989, 27, 2211. (43) Breuer, H.; Haaf, F.; Stabenow, J. Stress whitening and yielding mechanism of rubber-modified PVC. J. Macromol. Sci. Phys. 1977, B14, 387. (44) Garg, A. C.; Mai, Y. W. Failure mechanisms in toughened epoxy resins-a review. Compos. Sci. Technol. 1988, 31, 179. (45) Kinloch, A. C.; Young, R. J. Fracture Behaviour of Polymers; Elsevier: London, 1985. (46) Parker, D. S.; Sue, H. J.; Huang, J.; Yee, A. F. Toughening mechanisms in core-shell rubber modified polycarbonate. Polymer 1990, 31, 2267. (47) Jansen, B. J. P.; Rastogi, S.; Meijer, H. E. H.; Lemstra, P. J. Rubber-modified glassy amorphous polymers prepared via chemically induced phase separation. 1. Morphology development and mechanical properties. Macromolecules 2001, 34, 3998. (48) Smit, R. J. M.; Brekelmans, W. A. M.; Meijer, H. E. H. Predictive modelling of the properties and toughness of polymeric materials Part I Why is polystyrene brittle and polycarbonate tough? J. Mater. Sci. 2000, 35, 2855. (49) Smit, R. J. M.; Brekelmans, W. A. M.; Meijer, H. E. H. Predictive modelling of the properties and toughness of polymeric materials Part

II Effect of microstructural properties on the macroscopic response of rubber-modified polymers. J. Mater. Sci. 2000, 35, 2869. (50) Smit, R. J. M.; Brekelmans, W. A. M.; Meijer, H. E. H. Predictive modelling of the properties and toughness of polymeric materials part III simultaneous prediction of micro-and macrostructural deformation of rubber-modified polymers. J. Mater. Sci. 2000, 35, 2881. (51) Pearson, R. A.; Yee, A. F. Toughening mechanisms in elastomermodified epoxies. J. Mater. Sci. 1986, 21, 2475. (52) Dompas, D.; Groeninckx, G.; Isogawa, M.; Hasegawa, T.; Kadokura, M. Cavitation versus debonding during deformation of rubber-modified poly(vinyl chloride). Polymer 1995, 36, 437. (53) Lazzeri, A.; Bucknall, C. B. Dilatational bands in rubbertoughened polymers. J. Mater. Sci. 1993, 28, 6799. (54) Kinolch, A. J. Rubber-toughened Plastics; American Chemical Society: Washington, DC, 1989.

12573

dx.doi.org/10.1021/ie4009088 | Ind. Eng. Chem. Res. 2013, 52, 12567−12573