聚乳酸/羟丙基淀粉复合降解型材料的制备和表征

羟丙基改性淀粉作为填充剂,在偶联剂作用下与聚乳酸共混、挤出制备聚乳酸/羟丙基淀粉复合降解型材料。随着羟丙基改性淀粉含量的增加,共混材料的硬度略有增加、拉伸强度和断裂伸长率都先减小后增大,材料的吸水率和降解速率增加,且改性淀粉取代度的增加有利于提高材料的韧性。     

Study on polypropylene/natural rubber blend with polystyrene‐modified natural rubber as compatibilizer

Polystyrene‐modified natural rubber (SNR) was prepared in the laboratory and subsequently used as compatibilizer in polypropylene/natural rubber (PP/NR) blends. The effect of SNR (at 5%, 10%, 15% and 20% by volume) in PP/NR (70/30) blend was studied by maintaining the rubber volume while PP volume was replaced by SNR accordingly. The sequence of mixing was found to affect the blend morphology and tensile properties. The effect of curatives on the tensile properties of the blends was also investigated. The addition of curatives into the rubbers in PP/NR/SNR improved the tensile properties significantly compared with the PP/NR reference blend. For a semi‐efficient curative system, SNR loading at 10% gave the best overall tensile properties, while for an efficient curative system, 5% SNR loading resulted in improvements in tensile strength and stiffness of over 20% and 40%, respectively, compared with the reference. © 2002 Society of Chemical Industry     

Toughening polylactide with epoxidized styrene–butadiene impact resin: Mechanical,morphological, and rheological characterization

Styrene–butadiene impact resin (SBC) was chosen as the toughening agent to improve the tensile toughness of polylactide (PLA). Epoxidized SBC (ESBC) with different epoxidation degree were prepared by epoxidation using in situ peroxoformic acid method and a series of PLA/SBC(ESBC) blends were prepared by melt blending. The elongation at break of the PLA/ESBC blends was greatly improved, which was reflected in the slight decrease in the tensile strength and tensile modulus. Moreover, the tensile strength and tensile modulus were not significantly affected by the epoxidation degree of ESBC. For example, the incorporation of ESBC28.8% (30 wt %) to PLA caused an obvious increment of elongation at break from 3.5% of pure PLA to 305.0%, while the tensile modulus and tensile strength decreased to 80 and 78% of pure PLA, respectively. Scanning electron microscopy observations of cryo‐fractured surface morphology and particle size analysis demonstrated that the compatibility of the PLA/ESBC blends was improved significantly compared to PLA/SBC blend. PLA/ESBC(70/30) blends exhibited shear‐thinning behavior over the range of the studied shear rate. With an increase in shear rate, the non‐Newtonian index of the blends decreased gradually. Furthermore, the flow behavior of PLA/ESBC(70/30) blends was more sensitive to the shear rate than pure PLA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46058.     

成核剂和结晶促进剂对PET/PTT共混聚酯结晶性能的影响

分别采用双螺杆挤出法和转矩流变仪密炼法制备了PET/PTT共混聚酯,通过拉伸试验、冲击试验和DSC分析,研究了PET/PTT共混聚酯共混配比与力学性能的关系以及不同成核剂和不同结晶促进剂对PET/PTT共混聚酯结晶性能的影响。结果表明,当PET/PTT共混配比为75/25(质量比)时,PET/PTT共混聚酯能同时提高刚性和韧性,纳米SiO2成核剂可明显提高PET/PTT共混聚酯的结晶能力,聚醚1000结晶促进剂可显著提高PET/PTT/纳米SiO2共混聚酯的结晶速率。     

Nanocomposites of PLA/PP blends based on sepiolite

In the present study, the effectiveness of four polymers grafted with maleic anhydride used as compatibilizers in blends with poly(lactic acid) and its composites with sepiolite as matrices was evaluated in terms of transmission and scanning electron microscopy, oscillatory shear flow and tensile properties. Two polypropylenes were used as dispersed phases in the blends prepared in a corotating twin-screw extruder. Results showed that the compatibilized blends prepared without clay have higher susceptibility to isothermal degradation and higher tensile toughness than those prepared with sepiolite. The blend with the grafted metallocene polyethylene as compatibilizer exhibited the highest tensile toughness. The composites based on polyblends with polypropylene displayed lower tensile strength and Young’s modulus values, increased values of elongation at break, tensile toughness, complex viscosity, and storage modulus compared to those of the nanocomposite of PLA. These results are related to the clay dispersion, to the type of morphology of the different blends, to the grafting degree of the compatibilizers, and to the migration of the sepiolite toward the PP interface.     

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     

回归分析法研究补强剂对NBR/EVM并用胶性能的影响

采用回归分析法研究了FEF和ZDMA用量对NBR/EVM并用胶性能的影响。结果表明,在试验范围内,随着FEF或ZDMA用量的增加,硫化胶的硬度、拉伸强度、撕裂强度、100%定伸应力、压缩永久变形逐渐增大,而拉断伸长率逐渐减小,耐油性能得到改善;由等高线曲线可以清楚地看出两者用量对性能影响的规律,并可以预测胶料的各项物性与配合剂用量之间的关系。     

PP/LLDPE共混体系的研究

研究了聚丙烯(PP)／线性低密度聚乙烯(LLDPE)共混体系的形态结构与宏观性能之间的关系。对共混用的PP和LLDPE品种以及共混的工艺路线进行了选择；采用扫描电子显微镜(SEM)和偏光显微镜(PLY)观察了PP／LLDPE微观形态结构，并测试了力学性能和热性能。结果表明：屈服强度、拉伸模量、维卡软化点降低；当LLDPE用量增大时，随着LLDPE用量增加，材料的冲击强度增加，而拉伸共混体系形成互穿网络结构，具有良好的综合性能。     

Effect of high aspect ratio flaky aluminum on mechanical properties of epoxy-based particulate composites

Epoxy-based polymer composites are used in the aerospace industry due to high strength, less shrinkage, and ready availability. However, they are brittle and this limitation is usually addressed by using additives. Soft additives typically increase the toughness at the cost of stiffness and are usually not preferred for high strength applications. On the contrary, rigid additives such as carbon nanotubes (CNTs) and nanoclay increase the stiffness and tensile strength, but at the expense of strain at failure, indicating embrittlement. Also, these additives are expensive and this adds up to the overall product cost, limiting its application. Thus, this study aims to introduce a new low-cost, high aspect ratio additive that toughens epoxy without compromising on its strength. Tensile test and impact test were conducted to procure mechanical properties for the composite, along with fractography using electron microscopy. These tests revealed that this new additive increased the tensile strength, impact strength, and strain at failure by 56%, 60%, and 200% for a very low weight fraction of 0.5% of the additive.     

Influence of microstructure and flexibility of maleated styrene-b-(ethylene-co-butylene)-b-styrene rubber on the mechanical properties of polyamide 12

The present investigation deals with the mechanical and morphological properties of binary polyamide 12/maleic anhydride-grafted styrene-b-(ethylene-co-butylene)-b-styrene rubber (PA12/SEBS-g-MA) blends at varying dispersed phase (SEBS-g-MA) concentrations. Tensile behavior, impact strength and crystallinity of these blend systems were evaluated. Influence of microstructure, dispersed phase particle size, and ligament thickness on the impact toughness of the blend was studied. DSC data indicated an increase in crystallinity of PA12 in the blends. Tensile modulus and strength decreased while impact strength and elongation-at-break increased with the elastomer concentration. The enhanced properties were supported by interphase adhesion between the grafted maleic groups of rubber with polar moiety of polyamide 12. Analysis of the tensile data employing simple theoretical models showed the variation of stress concentration effect with blend composition.     

聚酰胺弹性体增韧聚乳酸改性研究

选用聚酰胺弹性体(聚酰胺和聚氧乙烯的共聚物,PAE)与聚乳酸(PLA)熔融共混进行增韧改性。结果表明,当PAE弹性体含量在20%～30%(质量分数,下同)之间时,共混体系发生脆韧转变,最大冲击强度达到67.6J/m,但拉伸强度和模量大幅度下降;PAE弹性体含量为5%～10%时共混体系的拉伸强度保持率最高,而且断裂伸长率提高近40倍,综合性能较好;虽然扫描电子显微镜照片显示共混体系为两相分离,但是差示扫描量热分析数据均表明,随着PAE弹性体含量的增加,共混体系的玻璃化转变温度和熔点发生相应变化,证明该共混体系为半溶混性,即两相间存在一定的相互作用;热失重分析数据显示,PAE弹性体在一定程度上提高了PLA的热降解温度。     

High‐density polyethylene/ultrahigh‐molecular‐weight polyethylene blend. I. The processing,thermal, and mechanical properties

Various blend ratios of high‐density polyethylene (HDPE) and ultrahigh‐molecular‐weight polyethylene (UHMWPE) were prepared with the objective of determining their suitability as biomaterials. Although the presence of HDPE in the blends enabled melt processing, the presence of UHMWPE helped to improve the toughness of the resulting blends. The processability of the blends was investigated with the Brabender torque, which was used as an indication of the optimum blend conditions. The blends were characterized with differential scanning calorimetry. The mechanical tests performed on the blends included tensile, flexural, and impact tests. A 50:50 (w/w) blend yielded optimum properties in terms of the processability and mechanical properties. The tensile property of the 50:50 blend was intermediate between those of HDPE and UHMWPE, but the strain at break increased 200% in comparison with that of both neat resins. The energy at break of the 50:50 blend revealed an improvement in the toughness. The fracture mechanism was also investigated with scanning electron microscopy. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 413–425, 2005     

In vitro degradation of poly(l-lactide)/poly(ε-caprolactone) blend reinforced with MWCNTs

The physical and mechanical properties of poly(l-lactide)/poly(??-caprolactone) (PLLA/PCL) blends reinforced with multiwalled carbon nanotubes (MWCNTs) before and after in vitro degradation were investigated. Because of brittleness, PLLA needs to be plasticized by PCL as a soft polymer. The MWCNTs are used to balance the stiffness and the flexibility of PLLA/PCL blends. The results showed that with incremental increase in concentration of MWCNTs in composites, the agglomerate points of MWCNTs were increased. The physical and mechanical properties of prepared PLLA/PCL blends and MWCNT/PLLA/PCL nanocomposites were characterized. The X-ray diffraction analysis of the prepared blends and composites showed that MWCNTs, as heterogeneous nucleation points, increased the lamella size and therefore the crystallinity of PLLA/PCL. The mechanical strength of blends was decreased with incremental increase in PCL weight ratio. The mechanical behavior of composites showed large strain after yielding and high elastic strain characteristics. The tensile tests results showed that the tensile modulus and tensile strength are significantly increased with increasing the concentration of MWCNTs in composites, while, the elongation-at-break was decreased. The in vitro degradation rate of polymer blends in phosphate buffer solution (PBS) increased with higher weight ratio of PCL in the blend. The in vitro degradation rate of nanocomposites in PBS increased about 65% when the concentration of MWCNTs increased up to 3% (by weight). The results showed that the degradation kinetics of nanocomposites for scaffolds can be engineered by varying the contents of MWCNTs.     

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     

甲基含氢硅油表面改性无卤膨胀阻燃剂研究

甲基含氢硅油与无卤膨胀型阻燃剂混合处理后,对聚丙烯材料进行阻燃改性,通过测试材料的拉伸强度,悬臂梁缺口冲击强度,氧指数,燃烧级数,热重分析和疏水保持率,并且利用方差分析和多重比较方法处理测试数据,研究甲基含氢硅油的加入对阻燃剂及阻燃改性材料性能的影响。结果表明:甲基含氢硅油的加入可以增加材料的韧性,降低材料的拉伸强度,显著提高处理后阻燃剂的疏水性。     

Effects of thermoplastic poly(ether-ester) elastomer and bentonite nanoclay on properties of poly(lactic acid)

This work presented the influence of thermoplastic poly(ether-ester) elastomer (TPEE) and bentonite (BTN) on improving the mechanical and thermal properties of poly(lactic acid) (PLA). PLA was initially melt mixed with TPEE at six different loadings (5–30 wt%) on a twin screw extruder and then injection molded. The mechanical tests revealed an increasing impact strength and elongation at break with increasing TPEE loading, but a diminishing Young's modulus and tensile strength with respect to pure PLA. The blend at 30 wt% TPEE provided the optimum improvement in toughness, exhibiting an increase in the impact strength and elongation at break by 3.21- and 10.62-fold over those of the pure PLA, respectively. Scanning electron microscopy analysis illustrated a ductile fractured surface of the blends with the small dispersed TPEE domains in PLA matrix, indicating their immiscibility. The 70/30 (wt/wt) PLA/TPEE blend was subsequently filled with three loadings of BTN (1, 3, and 5 parts by weight per hundred of blend resin [phr]), where the impact strength, Young's modulus, tensile strength and thermal stability of all the blends were improved, while the elongation at break was deteriorated. Among the three nanocomposites, that with 1 phr BTN formed exfoliated structure and so exhibited the highest impact strength, elongation at break, and tensile strength compared to the other intercalated nanocomposites. Moreover, the addition of BTN was found to increase the thermal stability of the neat PLA/TPEE blend due to the barrier properties and high thermal stability of BTN.     

Relationship of fracture behavior and morphology in polyolefin blends

High-density polyethylene (HDPE) and isotactic polypropylene (PP) were mixed either with a stabilizer or with a stabilizer and a compatibilizer in different mixing ratios. The structure and properties of these blends were analyzed by methods such as torsion pendulum measurements, mechanical short time experiments, electron microscopy, and fracture mechanical toughness tests. The results display a strongly increased impact strength in the HDPE/PP blend with compatibilizer within a specific mixing region. The deformation behavior and the mechanism leading to the increased impact strength of the blends were investigated in tensile tests by acoustic emission analysis and scanning electron microscopy: Increased fibrilation and strong strain was registered in the blend with compatibilizer. The impact strength was modeled, using experimentally measured properties such as energy release rate, matrix and inclusion volumes, the impact strength of each component. The inclusion volume that causes plastic deformation was chosen as an additional parameter. The calculated results are in good agreement with the experimental ones.     

Morphology and properties of the biosourced poly(lactic acid)/poly(ethylene oxide‐b‐amide‐12) blends

Biosourced poly(lactic acid) (PLA) blends with different content of poly(ethylene oxide‐b‐amide‐12) (PEBA) were prepared by melt compounding. The miscibility, phase structure, crystallization behavior, mechanical properties, and toughening mechanism were investigated. The blend was an immiscible system with the PEBA domains evenly dispersed in the PLA matrix. The PEBA component suppressed the nonisothermal melt crystallization of PLA. With the addition of PEBA, marked improvement in toughness of PLA was achieved. The maximum for elongation at break and impact strength of the blend reached the level of 346% and 60.5 kJ/m², respectively. The phase morphology evolution in the PLA/PEBA blends after tensile and impact tests was investigated, and the corresponding toughening mechanism was discussed. It was found that the PLA matrix demonstrates obvious shear yielding in the blend during the tensile and impact tests, which induced energy dissipation and therefore lead to improvement in toughness of the PLA/PEBA blends. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

Ternary polymer composites: PA6,6/maleated SEBS/glass beads

Polyamide 6,6 (PA6,6)/maleated styrene–hydrogenated butadiene–styrene (SEBS) blends filled with up to 20% spherical glass beads (GBs) were prepared by extrusion and subsequent injection molding. Tensile and impact tests were used to examine the effect of GB additions on the mechanical behavior of PA6,6/SEBS–g–MA 80/20 blend. Tensile measurements showed that the GB additions improve the stiffness of the PA6,6/SEBS–g–MA 80/20 blend but had little effect on its tensile ductility. The impact test revealed that the impact strength of PA6,6/SEBS–g–MA 80/20 blend tends to decrease with increasing GB content. Therefore, the GB additions were beneficial to maintain a stiffness-to-toughness balance of the PA6,6/SEBS–g–MA 80/20 blend. Finally, the correlation between the experimental tensile stiffness and strength with various theoretical models is discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3231–3237, 2001     

Morphologies and mechanical properties of polylactide/thermoplastic polyurethane elastomer blends

To explore a potential method for improving the toughness of a polylactide (PLA), we used a thermoplastic polyurethane (TPU) elastomer with a high strength and toughness and biocompatibility to prepare PLA/TPU blends suitable for a wide range of applications of PLA as general‐purpose plastics. The structure and properties of the PLA/TPU blends were studied in terms of the mechanical and morphological properties. The results indicate that an obvious yield and neck formation was observed for the PLA/TPU blends; this indicated the transition of PLA from brittle fracture to ductile fracture. The elongation at break and notched impact strength for the PLA/20 wt %TPU blend reached 350% and 25 KJ/m², respectively, without an obvious drop in the tensile strength. The blends were partially miscible systems because of the hydrogen bonding between the molecules of PLA and TPU. Spherical particles of TPU dispersed homogeneously in the PLA matrix, and the fracture surface presented much roughness. With increasing TPU content, the blends exhibited increasing tough failure. The J‐integral value of the PLA/TPU blend was much higher than that of the neat PLA; this indicated that the toughened blends had increasing crack initiation resistance and crack propagation resistance. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011