The effects of PC‐PMMA block copolymer on the compatibility and interfacial properties of PC/SAN blends

Block copolymers of polycarbonate (PC) and polymethylmethacrylate (PMMA), PCb‐PMMA, were examined as compatibilizers for blends of PC with styrene‐co‐acrylonitrile (SAN) copolymer. PC‐b‐PMMA was added to blends of PC with SAN containing various amounts of AN. The average diameter of the dispersed particles was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fiber retraction (IFR) test and an asymmetric double cantilever beam fracture test. The average particle size and interfacial tension of the PC/SAN blends reached a minimum value when the SAN copolymer contained about 24 wt% AN. A maximum in the adhesion energy was also observed at the same AN content. Interfacial tension and particle size were further reduced by adding PC‐b‐PMMA to the PC/SAN blends. Fracture toughness of the blends was also improved by enhancing the interfacial adhesion by the addition of PC‐b‐PMMA. The addition of PC‐b‐PMMA copolymer was more effective at improving the interfacial properties of PC/SAN blends than was varying the AN content of the SAN copolymers. The interfacial properties of the PC/SAN blends were optimized by adding a block copolymer and using an SAN copolymer that had minimum interaction energy with PC.     

Phase morphologies and mechanical properties of high‐impact polystyrene (HIPS) and polycarbonate blends compatibilized with polystyrene and polyarylate block copolymer

Phasemorphology and mechanical properties of blends of high‐impact polystyrene (HIPS) and polycarbonate (PC) blends compatibilized with a polystyrene (PS) and polyarylate (PAr) (PS–PAr) block copolymer were investigated. Over a broad range of composition from 50/50 through 30/70, HIPS/PC blends formed cocontinuous structures induced by the flow during the extrusion or injection‐molding processes. These cocontinuous phases had heterogeneity between the parallel and perpendicular directions to the flow. The micromorphology in the parallel direction to the flow consisted of stringlike phases, which were highly elongated along the flow. Their longitudinal size was long enough to be longer than 180 μm, while their lateral size was shorter than 5 μm, whereas that in the perpendicular direction to the flow showed a cocontinuous phase with regular spacing due to interconnection or blanching among the stringlike phases. The PS–PAr block copolymer was found to successfully compatibilize the HIPS/PC blends. The lateral size of the stringlike phases could be controlled both by the amount of the PS–PAr block copolymer added and by the shear rate during the extrusion or injection‐molding process without changing their longitudinal size. The HIPS/PC blend compatibilized with 3 wt % of the PS–PAr block copolymer under an average shear rate of 675 s^?1 showed a stringlike phase whose lateral size was reduced almost equal to the rubber particle size in HIPS. The tensile modulus and yield stress of the HIPS/PC blends could be explained by the addition rule of each component, while the elongation at break was almost equal to that of PC. These mechanical properties of the HIPS/PC blends can be explained by a parallel connection model independent of the HIPS and PC phases. On the other hand, the toughness factor of the HIPS/PC blends strongly depended on the lateral size of the stringlike phases and the rubber particle size in the HIPS. It was found that the size of the string phases and the rubber particle should be smaller than 1.0 μm to attain a reasonable energy absorbency by blending HIPS and PC. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2347–2360, 2001     

Linear viscoelastic and morphological description of multiphase systems affected by processing parameters

Influence of processing methods, in terms of comparing compression and injection moldings, on the rheological behavior of polycarbonate (PC)/acrylonitrile‐butadiene‐styrene (ABS) blends and PC/ABS/glass fibers composites is presented. Blend compositions and fiber content are considered as material variables. For blends, the effect of the processing route on the viscoelastic functions is evident only for low shearing frequencies. Injection molding created morphology with cocontinuous character, while compression molded blends have “relaxed” structure, where dispersed phase domains are several times larger than in injection molded ones. The glass fiber reinforcement led to the significant differences in viscoelastic properties of composites processed by injection and compression molding. Injected composites have both moduli always higher than compression molded. Also, fiber lengths are reduced more for compressing molding. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of blending sequence on the morphology and impact toughness of poly(ethylene terephthalate)/polycarbonate blends

The morphology of PET/PC/E‐GMA‐MA blends made by different mixing sequences was studied by transmission electron microscopy (TEM). The results suggest that migration of the E‐GMA‐MA copolymer from the PET phase to the PC phase occurred during the mixing of the (PET/E‐GMA‐MA) pre‐blend with the PC at 10% copolymer content. As a result of the migration, the E‐GMA‐MA particles are located in the PC phase rather than in the PET phase. This finding is not in agreement with the prediction made previously by others based on the possible reaction between the epoxy group of GMA and carboxyl group of PET. Core‐shell (PC/E‐GMA‐MA) particles formed in situ during blending and the size of the core‐shell particles was controlled by the blending sequence used. Mechanical properties of the ternary blends were tested at various temperatures. Although the blending sequence does not have a noticeable effect on the yield strength and modulus of the blends, it has a strong influence on the morphology formed, which determines the impact toughness. For blends made under optimum processing conditions, the brittle‐ductile transition occurred at a lower temperature and lower elastomer content. A study of the toughening mechanism suggested that the major toughening events were cavitation plus matrix shear yielding. It is postulated that the very high impact toughness found with the (PC/E‐GMA‐MA)/PET blend (at 10% E‐GMA‐MA) originated from the bimodal particle size distribution of the core‐shell particles formed in situ.     

Changes in the interfacial properties of PC/SAN blends with compatibilizer

Block copolymers of polycarbonate‐b‐poly(methyl methacrylate) (PC‐b‐PMMA) and tetramethyl poly(carbonate)‐b‐poly(methyl methacrylate) (TMPC‐b‐PMMA) were examined as compatibilizers for blends of polycarbonate (PC) with styrene‐co‐acrylonitrile (SAN) copolymer. To explore the effects of block copolymers on the compatibility of PC/SAN blends, the average diameter of the dispersed particles in the blend was measured with an image analyzer, and the interfacial properties of the blends were analyzed with an imbedded fiber retraction (IFR) technique and an asymmetric double cantilever beam fracture test. The average diameter of dispersed particles and interfacial tension of the PC/SAN blends were reduced by adding compatibilizer to the PC/SAN blends. Fracture toughness of the blends was also improved by enhancing interfacial adhesion with compatibilizer. TMPC‐b‐PMMA copolymer was more effective than PC‐b‐PMMA copolymer as a compatibilizer for the PC/SAN blends. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2649–2656, 2003     

A new composition–processing–property relationship for studying the tensile modulus‐phase plastic blends

Based on thermodynamic principles, a composition–processing–property relationship for predicting the modulus properties of multiphase plastic blends has been developed. This relationship describes the relative modulus of the blend in terms of the volume fraction and the index for the degree of mixing of an inclusion‐polymer in the matrix‐polymer. The relative modulus is defined as the ratio between the modulus of the blend and that of the matrix polymer. These blends include a nylon 6,6/polymethyl methacrylate(PMMA) system mixed using an injection molding process arid a nylon 6/ethylene‐vinyl acetate copolymer system mixed using a corotational extrusion process. Based on the values determined for the mixing index of the nylon 6,6/PMMA blends, a relationship between the mixing index and the fill time used in the injection molding has been developed. The results also imply that the degree of mixing of the blend mixed using a correlation extrusion process is better than that of the blend processed using an injection molding process. Using the above results, we now can scientifically develop new plastic blends and design optimum processing conditions for various automotive applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Rheological properties of poly(methyl methacrylate)/rigid ladderlike polyphenylsilsesquioxane blends

A series of poly(methyl methacrylate) (PMMA) blends with rigid ladderlike polyphenylsilsesquioxane (PPSQ) were prepared at weight ratios of 100/0, 95/5, 90/10, 85/15, and 80/20 by solution casting and then hot‐pressing. Their rheological properties have been studied under both dynamic shear and uniaxial elongation conditions. Their rheological properties depend on the compositions. The storage modulus, G′, loss modulus, G″, and dynamic shear viscosity, η*, of the PMMA/PPSQ 95/5 blend were slightly lower than those of pure PMMA. However, the values of G′, G″, and η* for the other PMMA/PPSQ blends are higher than those of PMMA. The G′ values increase with an increase in PPSQ content from 5% through 15% PPSQ at low frequencies and then drop as the PPSQ content increases to 20%. Uniaxial elongational viscosity (η_E) data demonstrate that PMMA/PPSQ blends exhibit slightly weaker (5% PPSQ) and much weaker (10% PPSQ) strain‐hardening than PMMA. In contrast, the PMMA/PPSQ 85/15 blend shows strain‐softening. Neither strain‐hardening nor strain‐softening was observed in the 80/20 blend. The special rheological properties for the 95/5 blend is probably due to a decrease in PMMA entanglements brought by the specific PMMA–PPSQ interactions. Rheological properties of PMMA/PPSQ blends with higher PPSQ content (≥10%) are mainly affected by formation of hard PPSQ particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 352–359, 2007     

In situ composites from blends of polycarbonate and a thermotropic liquid‐crystalline polymer: The influence of the processing temperature on the rheology,morphology, and mechanical properties of injection‐molded microcomposites

This work was aimed at understanding how the injection‐molding temperature affected the final mechanical properties of in situ composite materials based on polycarbonate (PC) reinforced with a liquid‐crystalline polymer (LCP). To that end, the LCP was a copolyester, called Vectra A950 (VA), made of 73 mol % 4‐hydroxybenzoic acid and 27 mol % 6‐hydroxy‐2 naphthoic acid. The injection‐molded PC/VA composites were produced with loadings of 5, 10, and 20 wt % VA at three different processing barrel temperatures (280, 290, and 300°C). When the composite was processed at barrel temperatures of 280 and 290°C, VA provided reinforcement to PC. The resulting injection‐molded structure had a distinct skin–core morphology with unoriented VA in the core. At these barrel temperatures, the viscosity of VA was lower than that of PC. However, when they were processed at 300°C, the VA domains were dispersed mainly in spherical droplets in the PC/VA composites and thus were unable to reinforce the material. The rheological measurements showed that now the viscosity of VA was higher than that of PC at 300°C. This structure development during the injection molding of these composites was manifested in the mechanical properties. The tensile modulus and tensile strength of the PC/VA composites were dependent on the processing temperature and on the VA concentrations. The modulus was maximum in the PC/VA blend with 20 wt % VA processed at 290°C. The Izod impact strength of the composites tended to markedly decrease with increasing VA content. The magnitude of the loss modulus decreased with increasing VA content at a given processing temperature. This was attributed to the anisotropic reinforcement of VA. Similarly, as the VA content increased, the modulus and thus the reinforcing effect were improved comparatively with the processing temperature increasing from 280 to 290°C; this, however, dropped in the case of composites processed at 300°C, at which the modulus anisotropy was reduced. Dynamic oscillatory shear measurements revealed that the viscoelastic properties, that is, the shear storage modulus and shear loss modulus, improved with decreasing processing temperatures and increasing VA contents in the composites. Also, the viscoelastic melt behavior (shear storage modulus and shear loss modulus) indicated that the addition of VA changed the distribution of the longer relaxation times of PC in the PC/VA composites. Thus, the injection‐molding processing temperature played a vital role in optimizing the morphology‐dependent mechanical properties of the polymer/LCP composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Effect of high molecular weight acrylic copolymers on the viscoelastic properties of engineering resins

In this work, the viscoelastic properties of acrylic‐based copolymer blends with poly(methyl methacrylate) (PMMA) and polycarbonate were investigated in the molten and solid states. High molecular weight copolymers of methyl methacrylate with butyl acrylate (MMA‐co‐BA) having varying molecular weight and composition were used to enhance the rheological properties in shear and extension. Blends containing up to 15 wt% of copolymer were prepared at 200°C and 150 rpm by using a DSM micro‐compounder. The samples were characterized by size exclusion chromatography (SEC), dynamic mechanical analysis (DMA), and rheology. The rheological properties were determined by using small amplitude oscillatory measurements (SAOM) in shear and a Rheotens? device for melt strength determination. For PMMA, the effects of high molecular weight PMMA copolymer on the matrix were related to the molecular weight, the tacticity of the copolymer, and the individual components. The rheological properties in shear showed enhanced storage and loss moduli at low frequency, while no change was observed at high frequency. In addition, extensional viscosity measurements made by using the filament stretching technique showed a significant increase in melt strength compared to that of the base PMMA with the blend containing the highest molecular weight copolymer showing the maximum force and a reduced drawdown ratio. For polycarbonate, its blends with acrylic copolymer were found to be immiscible. Similar enhancement in the moduli at low frequencies was observed, but a significant increase in the viscosity was obtained as well, resulting from the response of the two‐phase system. This change in the rheological properties was further increased at 15 wt% loading. Owing to the formation of a phase‐separated morphology, the melt strength was found to increase only slightly. J. VINYL. ADDIT. TECHNOL., 12:143–150, 2006. © 2006 Society of Plastics Engineers     

Fluid–structure interaction analysis on the film wrinkling problem of a film insert molded part

Back‐injection of polymeric liquid to preformed films, also known as film insert molding (FIM), provides the surface quality of polymeric parts. The back‐injection material is responsible for mechanical and thermal properties of the part, especially such as stiffness and thermal expansion. In the back‐injection molding it is important to ensure that the inserted films are not wrinkled by the injection of molten polymers. In this study, FIM was carried out with utilizing polycarbonate/acrylonitrile butadiene styrene (PC/ABS) alloy and polymethyl methacrylate/acrylonitrile butadiene styrene (PMMA/ABS) film. The wrinkling of films was observed by the atomic force microscope (AFM). Numerical simulations were performed to understand the mechanism of the film wrinkling and optimize the processing conditions of FIM for high precision parts by using commercial packages including Hypermesh?, Moldflow?, and COMSOL?. A critical shear rate for the film wrinkling of a center garnish part was determined based on the deformation energy of plate. It was found that the critical shear rate calculated numerically was in good agreement with that of the film insert molded parts. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Effect of dynamic cross‐linking on melt rheological properties of polypropylene/ethylene‐propylene‐diene rubber blends

Study of melts rheological properties of unvulcanized and dynamically vulcanized polypropylene (PP)/ethylene‐propylene‐diene rubber (EPDM) blends, at blending ratios 10–40 wt %, EPDM, are reported. Blends were prepared by melt mixing in an internal mixer at 190°C and rheological parameters have been evaluated at 220°C by single screw capillary rheometer. Vulcanization was performed with dimethylol phenolic resin. The effects of (i) blend composition; (ii) shear rate or shear stress on melt viscosity; (iii) shear sensitivity and flow characteristics at processing shear; (iv) melt elasticity of the extrudate; and (v) dynamic cross‐linking effect on the processing characteristics of the blends were studied. The melt viscosity increases with increasing EPDM concentration and decreased with increasing intensity of the shear mixing for all compositions. In comparison to the unvulcanized blends, dynamically vulcanized blends display highly pseudoplastic behavior provides unique processing characteristics that enable to perform well in both injection molding and extusion. The high viscosity at low shear rate provides the integrity of the extrudate during extrusion, and the low viscosity at high shear rate enables low injection pressure and less injection time. The low die‐swell characteristics of vulcanizate blends also give high precision for dimensional control during extrusion. The property differences for vulcanizate blends have also been explained in the light of differences in the morphology developed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1488–1505, 2000     

Mechanical properties and morphological changes of poly(lactic acid)/polycarbonate/poly(butylene adipate‐co‐terephthalate) blend through reactive processing

The mechanical properties and morphological changes of poly(lactic acid) (PLA), polycarbonate (PC), and poly(butylene adipate‐co‐terephthalate) (PBAT) polymer blends were investigated. Several types of blend samples were prepared by reactive processing (RP) with a twin‐screw extruder using dicumyl peroxide (DCP) as a radical initiator. Dynamic mechanical analyses (DMA) of binary polymer blends of PC/PBAT indicated that each component was miscible over a wide range of PC/PBAT mixing ratios. DMA of PLA/PBAT/PC ternary blends revealed that PBAT is miscible with PC even in the case of ternary blend system and the miscibility of PLA and PBAT can also be modified through RP. As a result, the tensile strain and impact strength of the ternary blends was increased considerably through RP, especially for PLA/PBAT/PC = 42/18/40 (wt/wt/wt) with DCP (0.3 phr). Scanning electron microscopy (SEM) analysis of the PLA/PBAT/PC blends revealed many small spherical island phases with a domain size of approximately 0.05–1 μm for RP, whereas it was approximately 10 μm without RP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Solvent cast blends of PMMA microspheres in bisphenol-A-polycarbonate

Abstract

Transparent films of bisphenol-A-polycarbonate (PC), poly (methyl methacrylate) (PMMA) microspheres and their blends at various compositions were prepared by solution casting using methylene chloride (MC) as a solvent. The structural, morphological and thermal properties were investigated by Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry and thermogravimetric analysis. It was obvious that all the characteristic absorption bands could be found in the IR spectra of PC/PMMA blends, but different in the strength. From the SEM images, a co-continue morphology was observed in the PC/PMMA blends when the PMMA content was above 80wt%, indicating the existence of special interaction between PC and PMMA microspheres. Differential scanning calorimetry results showed a single glass transition temperature (T_g) only for 10%PC/90%PMMA blends because of the better dissolution of PC in PMMA than PMMA in PC. Thermogravimetric analysis thermograms showed that the thermal stability of PC/PMMA blends increased with increasing PC content, which was due to the better thermal stability of PC.     

Increasing recyclability of PC,ABS and PMMA: Morphology and fracture behavior of binary and ternary blends

Binary and ternary blends of PC, ABS, and PMMA were studied. The blends were produced from original and recycled materials by melt mixing in a wide range of compositions. Instrumented Charpy impact testing, tensile testing, rheology investigations, and electron microscopy were carried out to determine the relationship between the deformation and fracture behavior, blend composition, morphology, and processing parameters. Resistance against unstable crack propagation was evaluated using the concepts of J‐integral and crack‐tip‐opening displacement (CTOD). The transition from ductile elastic‐plastic to brittle‐linear elastic fracture behavior was observed in the case of PC/ABS/PMMA blend at 10% of PMMA. Reprocessing had only a slight influence on the deformation and fracture behavior of the recycled blends. The blends produced from recycled materials proved to be competitive with the original pure materials. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Weld‐line characteristics of polycarbonate/acrylonitrile–butadiene–styrene blends. I. Effect of the processing temperature

The effects of the processing temperature on the morphology and mechanical properties at the weld line of 60/40 (w/w) polycarbonate (PC)/acrylonitrile–butadiene–styrene (ABS) copolymer blends were investigated. The influences of the incorporation of poly(methyl methacrylate) (PMMA) as a compatibilizer and an increase in the viscosity of the dispersed ABS domain phase were also studied. The ABS domain was well dispersed in the region below the V notch, and a coarse morphology in the core region was observed. When tensile stress was applied perpendicularly to the weld line, the fracture propagated along the weak region behind the weld part; there, the domain phase coalescence was significant because of the poor compatibility between PC and styrene–acrylonitrile (SAN). Phase coalescence became severe, and so the mechanical strength of the welded specimen decreased with an increasing injection‐molding temperature. The domain morphology became stable and the mechanical strength increased as the viscosity of the domain phase increased or some SAN was replaced with PMMA. That the morphology was well distributed behind the weld line and the mechanical properties of PC/ABS/PMMA blends were improved was attributed to the compatibilizing effect of PMMA. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 689–699, 2005     

The role of polycarbonate molecular weight in the poly(L‐lactide) blends compatibilized with poly(butylene succinate‐co‐L‐lactate)

Poly(butylene succinate‐co‐L ‐lactate) (PBSL)–compatibilized poly(L ‐lactide) (PLLA) polymer blends with two commercial grades of polycarbonate (PC) were investigated. The capillary tests showed that the steady shear viscosity of high molecular weight PC (PC‐L) was 10 times higher than that of low molecular weight PC (PC‐AD) throughout the shear rate range under investigation. Morphologic examination revealed that the shape of the dispersed PC‐L phase in the as‐extruded blends was largely spherical, but the PC‐AD phase was more like a rod and elongated further during injection molding. Notched Izod impact strength (IS) of the unmodified PLLA/PC‐L blend was higher than that of PC‐AD blend. The IS of modified ternary blends increased with PBSL content because of enhanced phase interaction indicated from thermal and morphologic analysis. The PBSL modification also enhanced IS more significantly in PLLA/PC‐L than in PLLA/PC‐AD blends. On the contrary, the heat deflection temperature (HDT) of PLLA/PC‐L binary system was much lower than that of PLLA/PC‐AD. HDT of PBSL‐modified PLLA/PC‐AD blends dropped with increasing PBSL content, which is a ductile polymer. Thermal and dynamic mechanical analysis of the ternary blends showed that individual components were immiscible with distinct T_gs for PC and PLLA and distinct T_ms for PBSL and PLLA. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Effects of extensional flow on properties of polyamide‐66/poly(2,6‐dimethyl‐1,4‐phenylene oxide) blends: A study of morphology,mechanical properties,and rheology

In this study, polyamide‐66/poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PA66/PPO) blends with high viscosity ratio were processed by a self‐designed triangle‐arrayed triple‐screw extruder (TTSE, which simulates extensional flow) and a commercial twin‐screw extruder (TSE), respectively. Furthermore, in order to improve the mechanical properties of the immiscible PA66/PPO blends, PPO‐grafted maleic anhydride (PPO‐g‐MA) and styrene–ethylene–butylene–styrene (SEBS) block copolymer were used. The mechanical properties, phase morphology, and rheological properties of both binary PA66/PPO blends and toughened PA66/PPO/PPO‐g‐MA blends were comprehensively investigated to compare the above mentioned two processing method. Samples processed with TTSE exhibited better mechanical properties than the TSE‐processed blends. The morphologies of the blends were examined by scanning electron microscopy, exhibiting smaller particles sizes and narrower particle size distributions, which were attributed to the significant effects of extensional flow in TTSE. The toughening mechanism of compatibilized blends was investigated through morphology analysis, dynamic mechanical, and rhelogical analysis. Thus, TTSE with an extensional effect was proved to be efficient in the blending of high viscosity ratio polymers. POLYM. ENG. SCI., 57:1090–1098, 2017. © 2016 Society of Plastics Engineers     

Compatibility and thermal properties of poly(acrylonitrile–butadiene–styrene) copolymer blends with poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The mechanical and heat‐resistant properties of acrylonitrile–butadiene–styrene (ABS) binary and ternary blends were investigated. The relationship of compatibility and properties was discussed. The results show that poly(methyl methacrylate) (PMMA) and styrene–maleic anhydride (SMA) can improve the thermal properties of conventional ABS. The Izod impact property of ABS/PMMA blends increases significantly with the addition of PMMA, whereas that of ABS/SMA blends decreases significantly with the addition of SMA. Blends mixed with high‐viscosity PMMA are characterized by higher heat‐distortion temperature (HDT), and their heat resistance is similar to that of blends mixed with SMA. For high‐viscosity PMMA, from 10 to 20%, it is clear that blends appear at the brittle–ductile transition, which is related to the compatibility of the two phases. TEM micrographs show low‐content and high‐viscosity PMMA in large, abnormally shaped forms in the matrix. Compatibility between PMMA and ABS is dependent on both the amount and the viscosity of PMMA. When the amount of high‐viscosity PMMA varied from 10 to 20 wt %, the morphology of the ABS binary blends varied from poor to satisfactory compatibility. As the viscosity of PMMA decreases, the critical amount of PMMA needed for the compatibility of the two phases also decreases. SMA, as a compatibilizer, improved the interfacial adhesiveness of ABS and PMMA, which results in PMMA having good dispersion in the matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2652–2660, 2002     

Role of in-situ polymethyl-methacrylate in addition type silicone rubber with specific reference to adhesion and damping properties

Herein, a strategy of embedding in-situ polymethyl-methacrylate (PMMA) domains in polydimethylsiloxane (PDMS) networks is proposed to enhance adhesive and damping properties of addition type silicone rubber (SR). PMMA domains improve the modulus of SR (at room temperature), which is stronger correlated to its adhesive performance, according to the Griffith criterion. Besides, the damping performance at high temperature is provided by the glass transition of thermoplastic PMMA. The PMMA/SR blends are obtained by the crosslink of PMMA and vinyl-terminated polydimethylsiloxane (vi-PDMS) liquid blends with polymethylhydrosiloxane, and the PMMA/vi-PDMS liquid blends are prepared by in-situ radical polymerization of methyl-methacrylate (MMA) in vi-PDMS with toluene as compatibilizer. Effects of disperse speed, compatibilizer content, and PMMA proportion on the morphologies and properties of PMMA/SR blends are studied. Small PMMA domains (around 800 nm) in PMMA/vi-PDMS blends with narrow size distribution and well dispersion are formed at appropriate disperse speed (100–300 rpm) and abundant compatibilizer content (~100 wt% refers to vi-PDMS). The blends with 20 wt% PMMA possess tensile strength over 8 MPa and lap shear strength over 5 MPa to stainless steel. And the blends with 50 wt% PMMA show good damping properties with tan δ over 0.15 at temperature range from −50 to 150°C. T_g-PMMA moves slightly to lower temperature with less PMMA embedded, but T_g-PDMS remained stable relatively.     

Study on ester–amide exchange reactions between Nylon 1010 and Ethylene‐vinyl acetate rubber

Reactive processing is a useful method to improve the compatibility of immiscible polymer blends. Nylon 1010/Ethylene‐vinyl acetate rubber (EVM) blends were prepared via melt blending at 240°C and tetrabutyl titanate (Ti(OBu)₄) was used as a catalyst. Ester–amide exchange reactions were proven to take place between Nylon and EVM during the shear processing. Melt flow index, Fourier transform infrared spectroscopy, and proton nuclear magnetic resonance spectra were used to study the reactions. It was demonstrated that tuning the shear rate could control the properties and reaction extent of Nylon 1010/EVM/Ti(OBu)₄ blends. The results revealed that the reactions were promoted by high shear rate. Tensile strength of the blends increased from 4.5 to 11.4 MPa when the shear rate increased from 20 to 80 rpm. Meanwhile, scanning electron microscopy was adopted to study the morphology of the reactive blends. It was found that the morphology of the blends was changed from sea‐island structures to co‐continuous structures while increasing the shear rate from 20 to 100 rpm. Dynamic mechanical analysis confirmed that high‐shear processing was found to promote the compatibility of the blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40064.