聚苯乙烯—聚乙烯的反应性共混研究

用ＩＲ，ＤＳＣ，ＤＭＡ等分析方法了研究恶唑啉官能化聚苯乙烯（ＲＰＳ）与马来酸酐接枝聚乙烯（ＭＰＥ）的共混反应，对反应性共混物及相应的非反应性共混物作了应力－应变试验，发现反应性共混提高了ＰＥ／ＰＳ共混物的力学性能，改变了ＭＰＥ的结晶情况。     

In situ reactive compatibilization in polymer blends: Effects of functional group concentrations

Polystyrene (PS) and polyethylene (PE), along with their reactive counterparts, i.e., polystyrene having oxazoline reactive groups (OPS) and polyethylene with carboxylic acid groups (CPE), were melt blended in a Rheomix mixer. These blends were prepared by mixing these polymers in various proportions under a variety of conditions. In an alternate procedure the OPS, CPE graft polymer (OPS-g-CPE) was prepared by melt blending these two polymers beforehand, and subsequently this grafted polymer was used as a compatibilizer for PS–PE blends. The effects of the addition of OPS and CPE, on the one hand, and OPS-g-CPE, on the other hand, on the compatibility of PS–PE blends were investigated. The morphology of these blends was examined with a scanning electron microscope (SEM) and related to their tensile properties. The PS–PE blends are found to have the typical coarse morphology of incompatible blends and poor tensile properties while their reactive counterparts, OPS-CPE blends, have fine grain microstructure and show improved tensile strength throughout the range and improved elongation in the PE-rich blends. Relatively low concentrations of the reactive pair, oxazoline and carboxylic acid, are shown to be necessary to produce improved compatibility. The preblended graft copolymer OPS-g-CPE imparts compatibility to PS–PE blends also but not as effectively. This suggests that the addition of OPS and CPE during melt mixing of PS and PE forms OPS-g-CPE polymer at the interface and that these ingredients act as “in situ reactive compatibilizers” which improve physical properties.     

Grafting styrene onto a polyethylene surface: A model study of an interfacial reaction

A model reactor system was assembled to study surface grafting reactions which would occur at the polymer interface in in-situ blend compatibilization using a vector fluid. The vector fluid's purpose is to convey a reactive ingredient to a blend interface and induce copolymer formation. Polyethylene (PE) was chosen as the polymer substrate, styrene monomer and/or dimethyl phthalate (DMP) as the vector fluid, and a peroxide initiator as the reactive ingredient. The free radical surface grafting reaction of styrene onto the PE surface was studied at melt processing temperature with a factorial experimental design involving the factors of time, temperature, initiator type and initiator concentration. It was found that styrene monomer was grafted at the PE substrate surface, forming a layer of PE-g-PS graft copolymer which was observed with attenuated total reflection Fourier transform infrared spectroscopy. The results indicated that the grafting reactions occurred not only at the immediate surface (2–3 μm), but also beneath the PE surface (∼ 200 μm) due to the swelling of the PE by the styrene monomer. The reaction below the immediate surface could be significantly reduced by the presence of DMP, a nonsolvent of PE; but the surface reaction was not affected. Explanations for the reaction behavior of the two different vector fluids are proposed based on the experimental results. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 427–440, 1998     

Preparation of polypropylene/acrylonitrile–styrene copolymer alloys by one‐step reactive blending

The compatibilization of polypropylene/acrylonitrile–styrene (PP/AS) blends through the addition of peroxide (DCP) was investigated in this study. The grafting reaction between PP and AS with the addition of peroxide occurred during the reactive‐blending process. The in situ‐formed grafting copolymers of PP‐g‐AS and AS‐g‐PP were then characterized by FTIR. The optimum concentration of the initiator, DCP, was 0.2 wt %, and the reaction temperature should be above 195°C. It was found that, when AS was the major component of the blends, the grafting of AS onto PP was the main process; conversely, when PP was the major component, PP was grafted onto AS. These results can be explained by the main‐chain scission of PP during the reactive‐blending process. With increase of the AS component, the total degree of grafting increased at first and then decreased after the composition of the blends reached 50/50. The maximum degree of grafting was found to be 6 wt % for the 50/50 PP/AS/DCP blend. PP was more degradable than was AS in the presence of peroxide at high temperatures. The MFR values of the PP/AS/DCP blends were slightly greater than were those of the simple PP/AS blends, which means that blending is an effective way to protect PP from degradation. SEM micrographs of the cross section of PP/AS/DCP showed a fine dispersion and a smaller domain size of the dispersed‐phase particles, implying that the in situ‐formed grafting copolymers act as a compatibilizer to reduce the interfacial tension between the PP and AS phases. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1284–1290, 2001     

Recycling of commingled plastics by cellulosic reinforcement

In this article, a model study was conducted on the effect of combining cellulose on the properties of virgin and/or recycled commingled plastics with a simulated waste‐plastics fraction composed of high‐density polyethylene (HDPE), polypropylene (PP), polystyrene (PS), and poly(vinyl chloride) (PVC) (PE/PP/PS/PVC = 7/1/1/1 by weight ratio). The compatibilizing effect of maleic anhydride‐grafted styrene–ethylene/butylene–styrene block copolymer (SEBS‐g‐MAH) for the cellulose‐reinforced commingled blends was also investigated. Commingled blends were prepared in a table kneader internal mixer. Mechanical properties were measured by using a universal testing machine. Thermal stability was measured by a thermogravimetric analyzer. It was found that the addition of more than 12.5% cellulose into the commingled blends was effective to enhance the mechanical properties of the virgin and recycled blends. The thermal stability as well as the mechanical properties of the commingled blends were much improved by the reactive blending of cellulose with the commingled blends by peroxide and maleic anhydride. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1531–1538, 1999     

Polyolefin/polystyrene in situ compatibilization using Friedel–Crafts alkylation

Polyolefin/polystyrene (PS) blends are difficult to compatibilize using in situ reactive compatibilization techniques, because neither of these polymers has any functional groups that one can use in the formation of a copolymer from these polymer components. In this study, the Friedel–Crafts alkylation was realized in a polyethylene/PS (PE/PS) melt blend, which resulted in improved compatibility between PE and PS. A number of Lewis acid compounds were tested as catalysts, among which the AlCl₃ was the most efficient. It was found in this study that the presence of a cocatalyst, such as a cationically polymerizable monomer or a halogenated alkane, significantly enhances the formation of PE-g-PS copolymer. The effects of blending parameters, such as temperature and blending time, on the in situ copolymer formation were investigated. The mechanical properties of compatibilized PE/PS blends were improved considerably. Such an in situ compatibilization technique has potential in the recycling of mixed polymer wastes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1385–1393, 1997     

Mechanical behavior of injection-molded polystyrene/polyethylene blends: Fracture toughness vs. fatigue crack propagation

Blends of polystyrene and polyethylene (PS/PE), including belnds in which a styrene/ethylene-butylene/styrene (SEBS) terpolymer was employed as a compatibilizer, were studied. Their rheology showed that the effect of the addition of SEBS to PS/PE blends was strongly affected by the blend composition and the shear rates involved in the blending and post-forming processes. The addition of PE to PS led to a reduction of fracture toughness compared with that of PS. This effect was attributed to the fine minor phase morphology of the blends obtained after extrusion blending and injection molding. The fatigue crack propagation (FCP) results showed that the fatigue crack growth rates were significantly reduced at low and moderate range of stress intensity factor (ΔK) by the presence of PE. Performance was enhanced when SEBS was present. The results also showed that both the fracture toughness and the FCP behavior of the blends were strongly dependent on the loading direction, the minor phase morphology, the composition of the blend, and, to a lesser degree, the presence of a compatibilizer. This study demonstrates that the fracture toughness and the FCP performance of such polymer blends can vary inversely.     

Crystalline crosslinked microparticles from immiscible blends of polyethylene and polystyrene

Crystalline crosslinked polyethylene microparticles with size distribution averages ranging from 0.374 to 0.944 μm were prepared from immiscible PS and PE blends in the melt phase for microgel applications. The particles were crosslinked either concurrently while blending using dicumyl peroxide or post blending via electron-beam irradiation. The effects of varying the processing temperature, blend duration, and block copolymer compatibilizer content on the particle morphology were studied and it was found that only a decrease in processing temperatures (increase in continuous-to-dispersed phase viscosity ratio) resulted in finer particles for the range of variables tested. The chemical composition of the isolated particles was determined using infrared and nuclear magnetic resonance spectroscopy while the particle morphology was investigated using electron microscopy image analysis in conjunction with thermogravimetric analysis. It was determined that particles produced with and without the block copolymer contained a small amount of PS even after meticulous extraction with a PS solvent (THF). However, the exact location of PS on the PE particles remains obscure.     

Rheology, morphology and tensile properties of reactive compatibilized polyethylene/polystyrene blends via Friedel–Crafts alkylation reaction

Attempts were made to study the effect of reactive compatibilization via Friedel?CCrafts alkylation reaction, using AlCl₃ as a catalyst, on rheology, morphology, and mechanical properties of polyethylene/polystyrene (PE/PS) blends. The results of linear viscoelastic measurements in conjunction with the results of the mixing torque variation indicated that PS showed much more degradation than that of PE in the presence of AlCl₃. It was also found that while for PE-rich blends, the viscosity, and storage modulus increased by reactive compatibilization, they decreased for PS-rich blends. The variation of viscosity and storage modulus for 50/50 blend was found to be dependent on frequency ranges showing the competitive effects of PE?Cg?CPS copolymer formation and PS degradation. The results of morphological studies showed that reactive compatibilization decreased the particle size and particle-size distribution broadness because of in situ graft copolymer formation. Reactive compatibilization enhanced the tensile strength and elongation at break for PE-rich blends. It was demonstrated that there is a close interrelationship between rheology, morphology, and mechanical properties of reactive compatiblized PE/PS blends. It was also demonstrated that rheological behaviors have a reliable sensitivity to follow the structural and morphological changes during compatibilization process, so that, those information can be used to predict the morphology as well as mechanical properties of the blends.     

Properties and morphology of polystyrene and linear low density polyethylene polyblend and polyalloy

A co-rotating twin screw extruder was employed in melt mixing and reactive extrusion of polystyrene/linear low density polyethylene (PS/PE) blends. Blends of PS/PE in the ratio of 9: 1 were prepared under different conditions of shear mixing and with different concentrations of dicurnlyl peroxide (DP) and triallyl isocyanurate (TALC) coupling agent. The Charpy impact strength of unnotched samples of melt blends was found to be lower than that of the polystyrene and was not affected much by the different conditions of melt mixing at different rates of extrusion, screw speeds, and screw configurations. In the case of reaction-extruded blends, the impact strength initially deteriorated with small addition of TAIC/DP, but improved with further increase in the level of TAIC/DP, exceeding that of polystyrene at an optimum concentration. With even further increase in TAIC/DP concentration, the impact strength again decreased. This was attributed to the different extents of coupling reactions of PE-TAIC-PE, PE-TAIC-PS, and PS-TAIC-PS with different levels of TAIC/DP. The interfacial adhesion of the incompatible PS-PE was postulated to be improved by the graft copolymers formed during reactive extrusion. This observation was supported by melt rheology, thermal characterization, molecular weight, and fracture surface morphology studies.     

Processing and morphology of polystyrene/ethylene-propylene rubber reactive and nonreactive blends

The difference between reactive and nonreactive polymer blends in terms of processing and morphology has been investigated. The glassy phases for the blends are an oxazoline functional polystyrene (PS-Ox) and a similar non-functional polystyrene (PS). The rubbery phases are an ethylene-propylene rubber (EP) and a similar ethylene-propylene rubber (EP-MA) with 07% grafted maleic anhydride. In the case of PS-Ox/EP-MA blends, the oxazoline group may react with the grafted rubber functionality at the interface between the two immiscible components during blending to form a compatibilizing agent in-situ. The nonreactive blends systems of PS-Ox/EP and PS/EP-MA were used for comparison to the reactive system. The blend components are rheologically matched to simplify the interpretation of the process and morphological data. The blends were prepared in a batch mixer with roller blades. The torque required for mixing was measured during the blending process. The torque traces for the reactive blends exhibited a peak in torque, attributed to the chemical reaction at the interface. The weight fraction of gel in the blends was used to measure the extent of reaction. It correlates well with the mixing torques and rheological properties. The nonreactive PS-Ox/EP and PS/EP-MA blends show poor interfacial adhesion between the two phases. In contrast, the reactive PS-Ox/EP-MA blends show excellent during annealing is also much greater for the reactive blends. Varying the functionality concentration in the PS phase shows that the dispersed phase rubber particle size is reduced by increasing the concentration of oxazoline in the matrix. Blends with no or small amounts of functionality in the PS phase exhibit yield behavior in tension. However, a level of concentration of reactive functionality may be reached where the material becomes brittle.     

PS/SBR-g-PS共混物的力学性能和形态结构

采用种子乳液聚合技术在丁苯胶乳上接枝聚合苯乙烯 ,合成了一系列丁苯橡胶接枝聚苯乙烯共聚物 (SBR-g-PS)。将其与聚苯乙烯 (PS)树脂共混后 ,考察了 SBR-g-PS的组成 (SBR/ PS)对共混物的力学性能和形态结构的影响。结果发现 ,当 SBR/ PS为 6 7/ 33-5 0 / 5 0时 ,PS/ SBR-g-PS共混物表现出良好的综合力学性能 ,在 SBR-g-PS中随着接枝 PS的增多 ,像胶粒子在基体中的分散状况获得改善 ,在大橡胶颗粒中含有大量的 PS次级粒子。在外负载的作用下 ,共混物中的大橡胶颗粒引发了大量的银纹 ,吸收了断裂应变能 ,从而提高了材料的冲击韧性。     

Polyethylene-polystyrene grafting reaction: effects of polyethylene molecular weight

Blending of different thermoplastic polymers usually results in segregated and low value materials for almost any mixing condition. Nevertheless, a synergetic combination of properties can be obtained by an adequate compatibilization via reactive blending. In this work a Friedel-Crafts alkylation reaction is used to graft polyethylene chains onto polystyrene. The relation between the initial PE molecular weight (MW) and the structure of the compatibilizer copolymer is studied by a combination of size exclusion chromatography and Fourier transform infrared spectroscopy. The amount of copolymer formed is estimated from the amount of polystyrene reacted. The relative lengths of the grafted polyethylene chains are assessed. It is found that lower MW PE produces, upon reaction, a greater amount of short chain length grafted PE onto PS than higher MW PE. The results are in agreement with theories relating the component MW to the reaction localization at the interface.The low cost Friedel-Crafts alkylation results in a convenient reaction for the in situ compatibilization of PE/PS blends. It produces enough graft copolymer to compatibilize the phases without causing PS crosslinking and PE chain scission.     

Chemical modification of polymer blends by reactive processing: In situ reactions of interlinking agents in PS/EPDM blends

Polystyrene (PS) and the ethylene–propylene–ethylidene norbornene terpolymer (EPDM) were melt-processed in the presence of multifunctional interlinking agents, divinylbenzene (DVB) and trimethylolpropane triacrylate (TRIS), in an internal mixer to promote functionalization of the polymers and target in situ formation of the interpolymer product via coreaction of the functionalities. This approach leads to effective in situ compatibilization of the otherwise incompatible polymer components of the blends. The weight ratio of PS/EPDM and the concentration of the interlinking agents were kept constant at 70/30 and 5%, respectively. The effect of varying the concentration of the free-radical initiator (a peroxide) and the method of its addition during melt processing on the overall reaction outcome was also examined. Changes in torque during the melt-processing operation was monitored. Sequential extraction of the polymer blends was used to separate and characterize the insoluble fraction (interpolymer). Changes in the thermal behavior (shifts in glass transition temperatures) of both the polymer blends and their insoluble fractions was investigated together with an examination of the morphology and mechanical properties of the reactively processed blends. It was found that the use of mixed reactive interlinking agents in a one-step reactive blending process and the enhancement of PS reactivity via preinitiation before addition of the reactive agents led to an increase in the extent of the coupling reaction between the functionalized PS and EPDM. This results in the formation of an “across-phase” interpolymer with an optimum composition that is responsible for the significant changes observed in the morphology and associated improvements in the mechanical properties of the blend samples. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1933–1951, 1998     

聚碳酸酯—聚苯乙烯的反应性挤出共混研究(Ⅰ)

研究了噁唑啉官能化聚苯乙烯(RPS)与聚碳酸酯(PC)的共混反应,对反应性共混物及相应的非反应性共混物作了应力-应变试验及动态力学分析(DMA),并测定其接枝率及密度,发现反应性挤出共混提高了PS/PC共混物的力学性能。     

Polystyrene and polyester polyurethane elastomer blends compatibilized by SMA

Blends of polystyrene (PS) with polyester polyurethane elastomer (PU‐es) were compatibilized by addition of poly(styrene‐co‐maleic anhydride) (SMA) containing 7 wt % of maleic anhydride. Binary nonreactive (PS/PU‐es) blends, binary reactive (SMA/PU‐es) blends, and ternary reactive blends (PS/SMA/PU‐es) were prepared with 10 and 20 wt % of PU‐es. The maleic anhydride content in the ternary reactive blends was varied through addition of different SMA amounts from 0.5 to 5 wt %. Polyurethane in the blends was crosslinked by using dicumyl peroxide or sulfur to improve its mechanical properties. The experimental processing conditions, such as temperature and rotor speed in an internal mixer, were analyzed before blend preparation by processing the individual polymers, PS and SMA, and the PS/PU‐es nonreactive blend (90/10), to prevent the degradation of the polymer during melt mixing and to assure macroscopic homogeneity. The torque behavior during the mixture indicated a grafting copolymerization, which was responsible for the significant drop of the PU‐es domain size in the glassy matrix, as observed by scanning electronic microscopy (SEM). The miscibility of the glassy matrix, which was shown to be dependent on the composition and the phase behavior of ternary blends, became very complex as the SMA concentration increased, as concluded from dynamical–mechanical analysis. Blends containing 20 wt % of PU‐es presented an increase up to a factor of 2 in the deflection at break in relation to PS. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2297–2304, 2004     

Reactive extrusion of polystyrene/polyethylene blends

The feasibility of inducing beneficial changes to polystyrene/polyethylene (PS/PE) blends via reactive extrusion processes is considered. Experiments have been conducted on 50:50 wt.% PS/PE blends that were treated with different levels of dicumyl peroxide and triallyl isocyanurate coupling agent. Both a low molecular weight and a high molecular weight blend series have been investigated. A “more reactive” polystyrene was synthesized by incorporation of a minor amount of ortho-vinylbenzaldehyde. Blends containing this modified polystyrene were subjected to identical processing' conditions on a counter-rotating twin screw extruder. Examination of the tensile properties of the extrusion products suggested that a judicious level of peroxide and coupling agent additives would be beneficial to the ultimate physical properties. The quantity of styrenic phase becoming chemically grafted to the polyethylene matrix was influenced most strongly by the level of the chosen coupling agent. As determined by scanning electron microscopy, the phase morphologies of the tensile test fracture surfaces were strongly dependent upon the reaction extrusion process; those extruded blends that had been exposed to the additive pre-treatment displayed substantially finer microstructure. The enthalpy of fusion of the polyethylene melting endotherm was likewise influenced by both the presence or absence of the additives as well as the molecular weight nature of the blend series.     

Mechanical properties and creep resistance in polystyrene/polyethylene blends

Recycled plastics, predominantly high‐density polyethylene (PE), are being processed in the shape of dimension lumber and marketed as “plastic lumber.” One drawback to these products is their low creep resistance or high creep speed. The objective of this study was to examine the feasibility of reducing the creep speed of PE‐based products by blending the PE with a lower‐creep plastic, in this case polystyrene (PS). Various blends of PE and PS were prepared in either a laboratory extruder or a bowl mixer and then compression‐molded. The mechanical properties, creep behavior, morphology, and thermal properties of extruded and compression‐molded samples were determined. The modulus of elasticity of the extruded blends could be estimated by a weighted average of PS and PE, even in the absence of a compatibilizer. Processing strongly affected the morphology and mechanical properties of the blends. For 50% PS : 50% PE blends, the stress–strain curves of the extruded samples showed PE‐like behavior, whereas those from compression‐molded samples were brittle, PS‐like curves. Flexural strength was 50% higher in the extruded samples than in those from compression molding. The creep experiments were performed in three‐point bending. Creep speed was lower in 50% PS : 50% PE and 75% PS : 25% PE blends than in pure PS. Creep speed of 75% PS : 25% PE was lowest of all the extruded blends. PE formed the continuous phase even when the PS content was as high as 50 wt %. For a 75% PS : 25% PE blend, cocontinuous phases were observed in the machine direction. A ribbonlike PS‐dispersed phase was observed in the 25% PS : 75% PE and 50% PS : 50% PE samples. Blending low‐creep‐speed PS with high‐creep‐speed PE appeared to successfully improve the performance of the final composite. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1100–1108, 2000     

国内外PS/PE共混改性研究新进展

综述了国内外采用接枝共聚物,嵌段共聚物以及反应性共混提高PS／PE相容性的研究方法。并提出应继续开发PS／PO合金的途径,并将其转化为工业产品。     

In situ compatibilization of polystyrene/polyolefin elastomer blends by the Friedel–Crafts alkylation reaction

Blends of polystyrene (PS) with polyolefin elastomer (POE) were prepared by a reactive extrusion method. In order to increase the compatibility of the two blending components, a Lewis acid catalyst, aluminium chloride (AlCl₃), was adopted to initiate the Friedel–Crafts alkylation reaction. Fourier‐transform infrared (FTIR) spectra of the PS/POE/AlCl₃ blends extracted with butanone verified the graft structure between the PS and POE. Because the in situ generated PS‐graft‐POE copolymers acted as compatibilizers, the mechanical properties of PS/POE blends were greatly improved. For example, after compatibilization, the Charpy impact strength of an 80/20 (wt%) PS/POE blend was increased from 6.29 to 8.50 kJ m^?2. Scanning electron microscopy (SEM) showed that the size of the droplets decreased from 9–10 µm to less than 2 µm with the addition of AlCl₃. Gel permeation chromatography (GPC) showed competition between the grafting reaction and the degradation of blending components in the presence of AlCl₃. Copyright © 2005 Society of Chemical Industry