Natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) blends

The grafting of the methyl methacrylate (MMA) monomer onto natural rubber using potassium persulfate as an initiator was carried out by emulsion polymerization. The rubber macroradicals reacted with MMA to form graft copolymers. The morphology of grafted natural rubber (GNR) was determined by transmission electron microscopy and it was confirmed that the graft copolymerization was a surface‐controlled process. The effects of the initiator concentration, reaction temperature, monomer concentration, and reaction time on the monomer conversion and grafting efficiency were investigated. The grafting efficiency of the GNR was determined by a solvent‐extraction technique. The natural rubber‐g‐methyl methacrylate/poly(methyl methacrylate) (NR‐g‐MMA/PMMA) blends were prepared by a melt‐mixing system. The mechanical properties and the fracture behavior of GNR/PMMA blends were evaluated as a function of the graft copolymer composition and the blend ratio. The tensile strength, tear strength, and hardness increased with an increase in PMMA content. The tensile fracture surface examined by scanning electron microscopy disclosed that the graft copolymer acted as an interfacial agent and gave a good adhesion between the two phases of the compatibilized blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 428–439, 2001     

A comparative study on different rubbery modifiers: Effect on morphologies,mechanical, and thermal properties of PLA blends

To improve the impact toughness of poly(lactic acid) (PLA), four kinds of rubbery modifiers, including ground tyre rubber (GTR), styrene‐butadiene‐styrene block copolymer (SBS), ethylene‐α‐octene copolymer (EOC) and glycidyl methacrylate grafted EOC (mEOC), were introduced for fabricating the PLA blends. The morphological structures, mechanical properties, thermal stability and thermal decomposition kinetics of pristine PLA and the blends were investigated. Results showed that representative droplet‐matrix structures were observed in the PLA blends, of which the PLA/SBS blend presented the smallest domains while PLA/EOC case had the largest elastomeric particle size. Accordingly, the highest impact toughness and elongation at break were achieved by PLA/SBS blend, whereas the tensile strength and elastic modulus for the blends were all lower than that of pristine PLA. Though the incorporation of rubbery modifiers barely altered the peak temperature of melting, the degrees of crystallinity for blends were declined sharply. The results of thermo gravimetric analysis indicated thermal degradation process of PLA phase was accelerated by rubbery modifiers and evidenced by the relative higher mass conversion at peak temperature. The reaction order of PLA phase for blends calculated by Carrasco method exhibited similar values when compared with control sample. However, the values of activation energy were rather lower than that of pure PLA. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43340.     

聚乙烯接枝马来酸酐／聚氯乙烯共混体系的研究

研究聚乙烯与马来酸酐单体接枝反应，探讨反应条件对接枝率的影响，通过红外光谱对接枝率结构进行表征；研究接枝物及聚氯乙烯含量对共混体系拉伸强度的影响规律，用扫描电子显微镜观察共混物中的界面形态。结果表明，低密度聚乙烯接枝马来酸酐／聚氯乙烯共混体系的相容性和力学性能均有较大提高，接枝率为10％左右，PVC含量为40%时，共混物的拉伸强度可达13．80MPa。     

Improvement of mechanical properties for PP/PS blends by in situ compatibilization

The effect of the in situ compatibilization on the mechanical properties of PP/PS blends was investigated. The application of Friedel-Crafts alkylation reaction to the PP/PS-blend compatibilization was assessed. Styrene/AlCl₃ was used as catalyst system. The graft copolymer (PP-g-PS) formed at the interphase showed relatively high emulsifying strength. Scission reactions, occurring in parallel with grafting, were verified for PP and PS at high catalyst concentration, but no crosslinking reactions were detected. Tensile tests were performed on dog-bone specimens of the blends. Both elongation at break and toughness increased with catalyst concentration. At 0.7% AlCl₃, a maximum was reached, which amounted to five times the value of the property for the uncompatibilized blend. At higher catalyst concentrations these properties decreased along with the PP molecular weight due to chain-scission reactions. On the other hand, the tensile strength did not change with the catalyst concentration. The in situ compatibilized blends showed considerable improvement in mechanical properties, but were adversely affected by chain scissions at high catalyst contents.     

Weld lines and mechanical properties of injection molded polyethylene/polystyrene/copolymer blends

In this article, we investigate the effect of weld lines on the tensile mechanical properties of unmodified and copolymer modified high density polyethylene (HDPE) and polystyrene (PS) blends. The homopolymers were melt blended in the proportion of 20 wt% HDPE and 80 wt% PS using a twin screw extruder at a temperature of 200°C. The results show that the mechanical properties are generally lower when weld lines are present. The decrease of the mechanical properties is much more pronounced for the blends. The addition of small amounts of a commercial styrene/butadiene copolymer significantly improves the strength and the elongation at break of this blend. An optimum copolymer concentration was observed at 3 wt%. This value coincides with the interphase saturation concentration of the copolymer obtained from the analysis of the DMTA (dynamic mechanical and thermal) properties of the blends. The copolymer was also found to induce important changes in the morphology of the blend. The interdiffusion of the polymer fronts in the weld region was also improved by the presence of the copolymer. It is believed that these two aspects contribute to the enhanced properties obtained with copolymer modified blends in presence of weld lines. An important effect of the injection temperature on the tensile strength and the elongation at break of welded samples with copolymer modified blends was observed. The effect of mold temperature on these properties was less important mainly at low injection temperatures. Only a slight effect of these two parameters was observed for the tensile modulus in the range of mold and injection temperatures considered in this study.     

异氰酸酯对聚乳酸/热塑性聚氨酯共混物性能的影响

以4,4^′-二苯基甲烷二异氰酸酯（MDI）为反应增容剂，采用熔融共混法制备了不同MDI含量的聚乳酸/热塑性聚氨酯（PLA/TPU）共混物，采用傅里叶变换红外光谱仪（FTIR）、万能试验机、冲击试验机、扫描电子显微镜（SEM）、差示扫描量热仪（DSC）和旋转流变仪对共混物力学性能、微观形态、热性能和流变性能进行了研究。结果表明：MDI可以有效改善共混物的力学性能，当MDI质量分数为1%时，共混物力学性能最佳，缺口冲击强度为40.0kJ/m²，断裂伸长率为214.1%，与未加MDI的共混物相比，分别增加了4.3倍和5.8倍，拉伸强度稍有下降（47.6MPa）；SEM表明，MDI的加入提高了共混物的相容性，加入MDI后，共混物的断面由海-岛结构变为核-壳包覆结构，相界面作用力增强；DSC测试表明，共混物的玻璃化转变温度、冷结晶温度和熔融温度随着MDI含量的增加而升高；流变测试表明，MDI质量分数的增加，共混物呈现更显著的剪切变稀行为，推测共混反应机理为：MDI质量分数的增加，体系内依次发生PLA的扩链、支化和TPU的交联。     

The effect of MBS on the heat resistant,mechanical properties,thermal behavior and rheological properties of PLA/EVOH blend

This work focuses on improve the mechanical properties of poly(lactic acid)/poly(ethylene-co-vinyl alcohol) (PLA/EVOH) blend and simultaneously remained a high Vicat softening temperature (VST) using appropriate contents of methyl methacrylate–butadiene–styrene copolymer (MBS) via simple melt blending. The effects of MBS on the heat resistant, mechanical properties, thermal properties and rheological behavior were examined in detail with various techniques. The VST of neat PLA significantly increased to 159 °C from 66.8 °C after blending with 50 wt% EVOH. However, the VST was gradually decreased with increasing MBS content but were still much higher than that of neat PLA. On the basis of the tensile and impact tests results, PLA/EVOH/MBS blends showed a considerably higher elongation at break and impact strength. For all PLA/EVOH/MBS blends, the thermal stability was increased compared than that of PLA/EVOH blend without MBS. With increasing MBS content, the complex viscosity and storage modulus of PLA/EVOH blend increased, especially at low frequencies, indicating that MBS enhanced the chain entanglement in the PLA/EVOH matrix. In addition, the results Han curves and Cole–Cole plots indicated that the relaxation time was increased when MBS was added.     

Mechanical properties and failure mode of thermoplastic elastomers from natural rubber/poly(methyl methacrylate)/natural rubber-g-poly(methyl methacrylate) blends

The mechanical properties and fracture behavior of natural rubber/poly-(methyl methacrylate) blends were investigated as a function of composition, graft copolymer concentration, and mixing conditions. The mechanical properties and failure behavior vary with the blend ratio, graft copolymer concentration, and mixing conditions. Various two-phase models were used to fit the experimental mechanical properties. Mechanical properties such as stress–strain behavior, tensile strength, tensile modulus, tear strength, and Izod impact strength were evaluated as a function of compatibilizer concentration. The domain size of the dispersed phase decreases with graft copolymer concentration followed by a leveling off at higher concentration. The mechanical properties attain a maximum value at the leveling point, which is an indication of interfacial saturation and the attainment of maximum interfacial adhesion between the homopolymers. Tensile and tear fracture surfaces were examined by scanning electron microscopy. The detachment of the dispersed domains from the matrix is an indication of no adhesion between the two phases in the case of uncompatibilized blends. Microfibrils between the matrix and the dispersed phase indicate a sign of interfacial adhesion between the phases in the case of compatibilized blends. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1245–1255, 1997     

Effect of blending conditions on mechanical,thermal, and rheological properties of plasticized poly(lactic acid)/maleated thermoplastic starch blends

This research work has concerned a study on relationship between structure and properties of maleated thermoplastic starch (MTPS)/plasticized poly(lactic acid) (PLA) blend. The aim of this work is to investigate the effects of blending time, temperature, and blend ratio on mechanical, rheological, and thermal properties of the blend. The MTPS was prepared by mixing the cassava starch with glycerol and maleic anhydride (MA). Chemical structure of the modified starch was characterized by using a FTIR technique, whereas the degree of substitution was determined by using a titration technique. After that, the MTPS prepared by 2.5 pph of MA was further used for blending with triacetin‐plasticized PLA under various conditions. Mechanical, thermal, and rheological properties of the blends were evaluated by using a tensile test, dynamic mechanical thermal analysis, and melt flow index (MFI) test, respectively. It was found that tensile strength and modulus of the MTPS/PLA blend increased with the starch content, blending temperature, and time, at the expense of their toughness and elongation values. The MFI values also increased with the above factors, suggesting some chain scission of the polymers during blending. SEM images of the various blends, however, revealed that the blend became more homogeneous if the temperature was increased. The above effect was discussed in the light of trans‐esterification. Last, it was found that mechanical properties of the PLA/MTPS blend were more superior to those of the normal PLA/TPS blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

EPDM/聚烯烃共混型热塑性弹性体的研究

制备ＥＰＤＭ／聚烯烃简单共混型热塑性弹性体。研究了聚合物种类、橡塑比、二元和三元共混对共混物力学性能的影响。结果表明，部分结晶性ＥＰＤＭ共混物的力学性能比无定形ＥＰＤＭ共混物好，部分结晶性ＥＰＤＭ与ＬＤＰＥ（低密度聚乙烯）共混物的拉伸强度大于两者的加和值，而其它二元共混物的拉伸强度均低于两共混单元的加和值；用ＬＤＰＥ部分替代ＰＰ，或用氯磺化聚乙烯（ＣＳＭ）部分替代结晶性ＥＰＤＭ进行三元共混，能改善部分结晶性ＥＰＤＭ／ＰＰ共混物的某些性能。     

The toughness and morphology of (chlorinated poly[vinyl chloride])/(methyl methacrylate‐butadiene‐styrene) blends

A series of methyl methacrylate‐butadiene‐styrene (MBS) graft copolymers were synthesized via seeded emulsion polymerization techniques by grafting styrene and methyl methacrylate on poly(butadiene‐co‐styrene) (SBR) particles. The chlorinated poly(vinyl chloride) (CPVC)/MBS blends were obtained by melting MBS graft copolymers with CPVC resin, and the effect of the core/shell ratio of MBS graft copolymer and SBR content of CPVC/MBS blends on the mechanical properties and morphology of CPVC/MBS blends was studied. The results showed that, with the increase in the core/shell ratio, the impact strength of the blend increased and then decreased. It was found that, when the core/shell ratio was 50/50, the impact strength was about 155 J/m, and the tensile strength evidently increased. The toughness of the CPVC/MBS blend was closely related to the SBR content of the blend, and with the increasing of SBR content of blend, the impact strength of the blend increased. The morphology of CPVC/MBS blends was observed via scanning electron microscopy. Scanning electron microscopy indicated that the toughness of CPVC/MBS blend was consistence with the dispersion of MBS graft copolymers in the CPVC matrix. J. VINYL ADDIT. TECHNOL., 22:501–505, 2016. © 2015 Society of Plastics Engineers     

Miscibility and thermal and mechanical properties of melt‐mixed poly(lactic acid)/poly(trimethylene terephthalate)/(methyl methacrylate)‐butadiene‐styrene copolymer blends

This study examined the miscibility and mechanical properties of melt‐mixed poly(lactic acid) (PLA), poly (trimethylene terephthalate) (PTT), and PLA/PTT blend with 5–10 phr of methyl methacrylate‐butadiene‐styrene copolymer (MBS). The isothermal crystallization kinetics of the PTT blends were analyzed by using the Avrami equation. The Differential Scanning Calorimetry (DSC) and scanning electron microscope results indicated that the miscibility of the PLA/PTT blends was improved by adding 5–10 phr of MBS. Although PLA, with the addition of 10 phr of MBS, had lower tensile strength at yield and higher breaking elongation and impact strength than pure PLA, no improvement in these mechanical properties could be observed in PLA/PTT blends. This result is explained by assuming that the crystallization of PTT at the interface favors the disentanglement of MBS from the PTT domain. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

接枝率对PVC/PA6-g-SMA共混物结构与性能的影响

采用熔融共混方法制备了聚氯乙烯（PVC）与不同接枝率苯乙烯-马来酸酐共聚物(SMA）接枝改性聚酰胺6（PA6-g-SMA）的共混物,研究了PA6-g-SMA接枝率对PVC/PA6-g-SMA共混物力学性能及凝聚态结构的影响。结果表明,接枝率越高,PA6-g-SMA与PVC的相容性越好,在PVC基体中能以更小的相畴均匀分散,对PVC的增韧增强作用越明显;当PA6-g-SMA的接枝率为5.12 %,添加量为15 ％（质量分数,下同）时,共混物的冲击强度为64.7 kJ/m2,拉伸强度为55 MPa。     

POE接枝衣康酸增容PA6/POE共混物性能及形态研究

以衣康酸（ITA）为接枝单体,采用双螺杆挤出机和熔融接枝技术制备了一系列乙烯-辛烯共聚物接枝物（POE-g-ITA）,通过红外光谱对接枝物的结构进行了表征,研究了引发剂和单体用量对POE-g-ITA接枝率和熔体流动速率的影响,当POE/ITA/过氧化二异丙苯（DCP）=94/6/0.36时,接枝率达到1.36 %;通过双螺杆挤出机将相容剂POE-g-ITA引入到聚酰胺6/乙烯-辛烯共聚物（PA6/POE）共混物中,研究了共混物的力学性能和形态结构。结果表明,加入5份（质量份数,下同）POE-g-ITA后,PA 6/POE共混物的冲击强度提高到纯PA 6的12.78倍,PA6与POE两相界面变得模糊,分散相尺寸明显减小,界面相互作用明显增强,相容性得到显著提高。     

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) copolymer on the properties of polylactide/poly(methyl methacrylate) blend

The effect of the addition of poly(styrene‐co‐glycidyl methacrylate) P(S‐co‐GMA) copolymer on the properties of melt blended polylactide/poly(methyl methacrylate) (PLA/PMMA) 80/20 (wt %) composition was studied. In the literature high ductility levels were achieved by melt blending PLA with different additives. However, the gained ductility was counter balanced with drastic drops in strength and modulus values. The novelty of this work was the preparation of PLA‐based blends with polylactide content higher than 75 wt % which showed an impact resistance value improvement of about 60% compared with the neat PLA and maintained similar tensile strength and modulus values as well as glass transition temperature to neat PLA. The addition of only 3 pph of copolymer to PLA/PMMA blend improved the impact resistance almost 100%. The chemical reaction between PLA/PMMA blend and P(S‐co‐GMA) copolymer were analyzed by FTIR, rotational rheometry, and GPC/SEC. Phase structure and morphology were studied by Differential Scanning Calorimetry and Scanning Electronic Microscopy. Tensile and impact properties as well as thermal stability were also studied. Results showed that as the amount of copolymer in the blend was increased then higher was average molecular weight and polydispersity index. After the addition of P(S‐co‐GMA) copolymer to the PLA/PMMA blend the impact resistance, elongation at break and thermal stability were improved while tensile strength and elastic modulus remained almost unaltered. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43935.     

丙烯酸酯接枝改性天然橡胶增韧聚乳酸

通过在天然橡胶(NR)分子链上接枝甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA),制备了三种丙烯酸酯接枝改性NR:NR-g-PMMA,NR-g-PBA和NR-g-(PMMA,PBA)。采用核磁共振氢谱对三种接枝物进行了化学结构鉴定。将接枝改性后的NR和未改性的NR与PLA采用哈克密炼机熔融共混,分别制备了PLA/NR,PLA/NR-gPMMA,PLA/NR-g-PBA和PLA/NR-g-(PMMA,PBA)共混物,研究了接枝改性NR和未改性NR含量对共混物力学性能和热性能的影响。各共混物的拉伸弹性模量和拉伸强度均随接枝改性NR和未改性NR含量的增加而降低,断裂伸长率和缺口冲击强度随接枝改性NR和未改性NR含量的增加而提高。其中,PLA/NR-g-PBA共混物的断裂伸长率和缺口冲击强度比其它共混物提高的幅度大,当NR-g-PBA的质量分数为5%时,PLA/NR-g-PBA共混物的断裂伸长率达到78%,缺口冲击强度为5.2 k J/m2,而纯PLA的断裂伸长率仅为7.7%,缺口冲击强度为2.5 k J/m2,说明NR接枝分子柔顺性较高的BA更有利于促进其与PLA共混物的韧性提高。热分析结果表明,PLA/NR-gPBA共混物的热稳定性相比于纯PLA也有所提高。     

Preparation and characterization of polylactide/thermoplastic konjac glucomannan blends

In this article, a new degradable thermoplastic konjac glucomannan (TKGM) was synthesized by graft copolymerization of vinyl acetate and methyl acrylate onto konjac glucomannan (KGM). Melt blending of polylactide (PLA) and TKGM has been performed in an effort to improve the processing and comprehensive mechanical properties of PLA and TKGM without compromising its degradability and biocompatibility. The miscibility, processing rheology, phase morphology, thermal properties, interaction, crystallization and mechanical properties of PLA/TKGM blends were investigated in detail. The thermal processing property of PLA/TKGM blend (60/40) was quite close to low density polyethylene (LDPE). As observed from the tan δ curves in dynamic mechanical analysis, all of the blends exhibit a single glass transition over the entire composition range, indicating that the blends were thermodynamically miscible. The TKGM exhibited a relatively broad endothermic peak at around 120 °C, which was lower than that of KGM. And an obvious glass-transition behavior was obtained around 26.6 °C. Furthermore, the PLA/TKGM blend (60/40) had a very high elongation at break of 234.8%, while the tensile strength remained as high as 36.5 MPa. And the PLA/TKGM blend (20/80) resulted in an even greater ductility with an elongation at break of 520.5% as compared with 14.1% for pure PLA. A substantial increase in the non-notched impact strength was also observed with the PLA/TKGM blend (20/80) demonstrating two times the impact strength of pure PLA.     

Structural, morphological and mechanical characteristics of polyethylene, poly(lactic acid) and poly(ethylene-co-glycidyl methacrylate) blends

In this work, uncompatibilized and compatibilized blends of low density polyethylene (LDPE) and poly(lactic acid) (PLA) were subjected to several investigations: Fourier transform infrared (FTIR) spectroscopy, morphological analysis and mechanical testing (tensile, impact, microhardness). The copolymer (ethylene-co-glycidyl methacrylate) (EGMA) was used as compatibilizer. The percentages of PLA in LDPE/PLA samples ranged from 0 to 100 wt% while the EGMA was added to the blend 60/40 (LDPE/PLA) at concentrations of 2, 5, 7, 10, 15 and 20 parts per hundred (phr). FTIR analysis showed the absence of any interaction between LDPE and PLA, but after addition of compatibilizer, reactions between epoxy groups of EGMA and carboxylic or hydroxyl groups of PLA were confirmed. Tensile and impact tests revealed a loss of ductility of LDPE with the incorporation of PLA, except for the composition 80/20 (LDPE/PLA). However, the addition of 15 phr of EGMA led to the maximum increase in the elongation-at-break (about three times the value of uncompatibilized blend) and in the impact strength, but a marginal improvement was observed for tensile strength. SEM micrographs confirmed that the enhancement of mechanical properties is due to the improvement of the interfacial adhesion between different phases owing to the presence of EGMA. The microhardness values of the different blends (uncompatibilized or compatibilized) were in good agreement with the macroscopic mechanical properties (tensile and impact strengths).     

The Compatibilization of EPDM/SBR Blends by EPDM-Graft-Styrene Copolymer

Abstract

Ethylene propylene diene rubber (EPDM) and styrene butadiene rubber (SBR) blends were compatibilized by a graft copolymer EPDM-graft-styrene. This compatibilizer was prepared by gamma radiation induced grafting of EPDM with styrene monomer. The compatibilized blends were evaluated by scanning electron microscope and dielectric properties. The obtained results reveal that the addition of a small percentage of graft copolymer to EPDM/SBR blends improves the physico-mechanical properties of the blend vulcanizates, and this can be related to the enhancement of the blend compatibility.     

The effect of poly(butylene succinate) content on the structure and thermal and mechanical properties of its blends with polylactide

Poly(butylene succinate) (PBS) and polylactide (PLA) were blended in a co‐rotating twin‐screw extruder with various contents of PBS from 0 to 100 wt%. The effect of PBS content on the thermal and mechanical properties of PBS/PLA blends was investigated by using DSC, softening point measurements, a Charpy impact test and tensile testing. The Fourier transform infrared spectra showed that the polymers are immiscible, but the addition of PBS could modify the PLA structure in PBS/PLA blends by changing the content of amorphous and crystalline phases. In addition, the cold crystallization temperature of PLA in blends decreases in comparison with pure PLA, which shows that PBS could have a plasticizing effect on PLA. This is confirmed by the results of DSC analysis. The mechanical properties of the blends depend on the percentage of PBS addition. Typically, the mechanical properties of PBS/PLA blends are intermediate between the properties of the polyesters from which they are obtained. However, in some cases unexpected changes in mechanical properties of the blends were observed. For example, the elongation at break for a PBS/PLA blend containing 10 wt% PLA is higher than for pure PBS. © 2019 Society of Chemical Industry