Physical aging and thermal aging resistance of polycarbonate/poly(styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene) blends

The effect of thermal annealing on the mechanical properties of polycarbonate (PC) was investigated by tensile testing, Izod impact testing, and differential scanning calorimetry (DSC). An endothermic peak appeared in the DSC curve by annealing at various temperatures below T_g. The peak area, as a measure of the degree of physical aging, increased with annealing time. The Izod impact strength decreased suddenly just before an endothermic peak became detectable. The results imply that at the very early stage of physical aging, a trigger for the ductile‐to‐brittle transition may be initiated. By blending hydrogenated styrene‐butadiene‐styrene block copolymer (SEBS), the embrittlement by annealing was prevented. That is, in the PC/SEBS blends, the physical aging of PC matrix proceeded in the same way as in neat PC; however, the Izod impact strength did not decrease. This thermal aging resistance seems to originate from the negative pressure effect of SEBS particles that provides dilational stress fields for PC matrix to enhance the local segment motions. POLYM. ENG. SCI., 52:1958–1963, 2012. © 2012 Society of Plastics Engineers     

Copolyterephthalates containing tetramethylcyclobutane with impact and ballistic properties greater than bisphenol A polycarbonate

For the past 40 years bisphenol A polycarbonate has been the industry standard for lightweight transparent armor protection. More recently, researchers at the Shell Chemical Company developed a co-polyester derived from 2,2,4,4-tetramethyl-1,3-cyclobutanediol (CBDO), 1,3-propanediol (PDO), and dimethyl terephthalate (DMT). By varying the percent incorporation of the monomers, the thermal/mechanical properties of this copolyterephthalate are tunable. Shell found that interesting impact properties arose from the material when 40 mol% CBDO was incorporated into the polymer. This material displayed a notched Izod value of 1070 J/m while maintaining T_g near 100 °C. The work discussed here focuses on the mechanical, impact, and ballistic characterizations of this material. Tensile, notched Izod, and .22 FSP V50 data are reported. This new material shows improvement over bisphenol A polycarbonate in both notched Izod as well as ballistic impact values.     

Structure and physical properties of reprocessed poly(ether imide)

The effects of reprocessing by injection molding on the structure and properties of poly(ether imide) (PEI) were studied. The chemical structure of PEI does not change after reprocessing. However, the weight-average molecular weight decreases after the first and the second injection cycles, after which it stays constant. Despite the harsh conditions used, the thermal resistence and the small strain mechanical properties were unaffected by the application of successive injection molding processes to the 100% regrind PEI specimens. The tensile ductility and energy at break showed a decrease parallel to that of the molecular weight. However, the Izod impact strength was constant, probably due to the differences in strain rate and mode of deformation between the tensile and impact tests. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1601–1607, 1997     

剑麻纤维/聚丙烯木塑复合材料的热氧老化性能研究

以剑麻纤维(SF)、聚丙烯(PP)为原料,经熔融共混、模压成型工艺制备木塑复合材料。探讨了SF/PP复合材料的力学性能、热性能随老化时间和SF含量的变化规律,借助扫描电镜对复合材料老化前后的冲击断面进行微观结构分析。结果表明:老化后复合材料的冲击强度、弯曲强度和弯曲模量随剑麻含量的增加而降低;同时,复合材料中PP相的结晶速率、结晶度也有所降低,但复合材料的热稳定性基本没有变化。     

UV老化对ZnO填充PA6/LGF复合材料性能的影响

用熔融共混法制备出长玻璃纤维(LGF)含量为30%的LGF增强尼龙6(PA6)/ZnO(PA6/LGF/ZnO)复合材料,并采用氙灯紫外(UV)老化法研究了ZnO含量为0%~8%及UV老化时间为0~800 h对复合材料力学性能和结晶性能的影响。结果表明,经UV辐照后,PA6/LGF/ZnO复合材料的拉伸强度升高,韧性下降,其中当ZnO添加量为6%时,复合材料在800 h老化后的拉伸强度和缺口冲击强度保留率较未添加ZnO的复合材料分别提高了5.39%和4.98%。SEM分析表明在UV老化过程中,LGF与PA6基体之间的界面并未受到明显破坏,老化主要集中发生在PA6基体上。随着老化时间的延长,PA6/LGF复合材料中的PA6出现UV交联而使其结晶度从26.19%降低至20.70%;对于ZnO含量为6%的PA6/LGF/ZnO复合材料,老化800 h后其结晶度仅从22.92%下降至21.34%,PA6/LGF/ZnO复合材料整体上的结晶性能趋于稳定。     

Mechanical behavior of tetrafunctional/phenol novolac epoxy mixtures cured with a diamine

An amine‐cured epoxy system based on tetraglycidyldiaminodiphenylmethane and a novolac glycidyl ether resin was studied. Epoxies were prepared by varying the cure schedules and using the isothermal time–temperature–transformation diagram of the system. The materials were characterized using dynamic‐mechanical analysis (DMA), tensile stress–strain tests over a range of temperatures and testing speeds, impact, and hardness tests. Optical microscopy was used to study the fracture surfaces of the samples. Some interrelations between the behavior and the microstructure of the system are discussed. In addition, the effect of thermal aging on the mechanical properties has been studied. DMA analysis seemed to reveal a structure that tended to be less heterogeneous with increasing the crosslink density. The advance in the etherification reactions or the thermal aging has reduced the mechanical properties related with the consumption of energy to break. The optimal cure schedule according to the global properties has been established. The morphology of fractured surfaces by optical microscopy showed a clear correlation with the variation of the tensile properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2305–2313, 2000     

Comparison of microwave and thermal cure of epoxy–anhydride resins: Mechanical properties and dynamic characteristics

The objective of this work was to compare the mechanical properties of epoxy resins cured by thermal heating and microwave heating. Epoxy–anhydride (100:80) resins were cured in a domestic microwave oven and in a thermal oven. The hardening agents included methyl tetrahydrophthalic anhydride and methyl hexahydrophthalic anhydride. Three types of accelerators were employed. Thermal curing was performed at 150°C for 20 and 14 min for resins containing 1 and 4% accelerator, respectively. Microwave curing was carried out at a low power (207 or 276 W) for 10, 14, and 20 min. All cured resins were investigated with respect to their tensile properties, notched Izod impact resistance, and flexural properties (three‐point bending) according to ASTM standards. The tan δ and activation energy values were investigated with dynamic mechanical thermal analysis, and the extent of conversion was determined with differential scanning calorimetry. The differences in the mechanical properties of the thermally cured and microwave‐cured samples depended on the resin formulation and properties. Equivalent or better mechanical properties were obtained by microwave curing, in comparison with those obtained by thermal curing. Microwave curing also provided a shorter cure time and an equivalent degree of conversion. The glass‐transition temperatures (tan δ) of the thermally and microwave‐cured resins were comparable, and their activation energies were in the range of 327–521 kJ/mol. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1442–1461, 2005     

尼龙1212/EPDM-g-MAH共混体系的制备及性能研究

制备了尼龙（PA）1212／EPDM－g-MAH共混物，并对其力学性能、热性能及共混形态进行了研究，结果表明，增韧剂的加入使共混物的缺口冲击强度显著增大，当增韧剂含量为20％时，缺口冲击强度为74．98kJ/m^3，是纯PA1212的13．5倍；用二甲苯处理过的共混物试样断面很不平坦，有很多孔洞和类纤维体，说明弹性体粒子以球状分散于基体树脂中。     

二元胺型苯并噁嗪/双马来酰亚胺共混树脂及其玻璃布增强的层压板

苯并噁嗪(BZ)和双马来酰亚胺(BMI)按照不同的配比进行共混固化。用FTIR、DSC、凝胶化时间、DMA、TGA、万能电子拉力机分别研究了BZ/BMI共混体系的固化行为以及BZ/BMI固化树脂的热性能和剪切强度等。结果表明BZ和BMI除了发生均聚反应,还发生苯并噁嗪开环生成的酚羟基和双马来酰亚胺的双键生成醚键的反应。BZ和BMI共混后,固化温度比各自的固化温度都低。BMI的加入提高了共混树脂的热性能,BZ/BMI固化树脂的T_g达289℃,T_d5达387℃,T_d10达422℃,800℃的残炭率达55.3%。另外,BMI的加入提高了BZ/BMI固化树脂的剪切强度,当BMI的含量为60％时,BZ/BMI固化树脂的剪切强度为12.44 MPa。进一步,制备了玻璃布增强的BZ/BMI层压板,并对其力学性能和断面形貌进行了研究。结果表明,当BMI用量为40%时,BZ/BMI层压板的拉伸强度、弯曲强度、冲击强度分别达394 MPa、490 MPa、160 kJ·m^-2。     

环氧树脂对PP/EPDM-g-MAH力学性能与形态结构的影响

将未固化的环氧树脂与不同比例的PP/EPDM-g-MAH共混挤出,得到复合材料。通过力学性能测试、动态力学性能分析(DMA)、差示扫描量热法(DSC)以及扫描电镜(SEM),研究了环氧树脂对共混物力学性能与形态结构的影响。结果表明:当PP/EPDM-g-MAH为80/20时,环氧树脂的加入能极大地提高共混物的缺口冲击强度,加入3%的环氧树脂,PP/EPDM-g-MAH(80/20)共混体系的缺口冲击强度从17.5 kJ/m2提高到62.47kJ/m2;在全体系中,环氧树脂的加入对拉伸性能影响较小,使EPDM-g-MAH分散相尺寸变小,在基体中分布更均匀。     

ABS/HIPS相容性的研究

采用苯乙烯-马来酸酐共聚物(SMA)作为丙烯腈-丁二烯-苯乙烯共聚物/高抗冲聚苯乙烯(ABS/HIPS)的相容剂,研究了SMA对ABS/HIPS共混体系力学性能的影响,并用扫描电子显微镜对共混物的亚微观形态结构进行了分析。结果表明,SMA的加入起到了很好的增容作用。随着HIPS/SMA用量的增加,共混物的冲击性能先增大后减小,当HIPS/SMA=8.5/1.5(质量比),且HIPS/SMA质量分数为10%时,共混物的缺口冲击强度达到97.1J/m,同时拉伸强度和弯曲强度最大。     

分子量分布对低密度聚乙烯光氧老化特性的影响

采用衰减全反射红外光谱技术（ATR-FTIR）、热重分析法（TG）、凝胶渗透色谱（GPC）、扫描电子显微镜（SEM）和力学试验比较研究了不同分子量分布指数低密度聚乙烯（LDPE）的光氧老化特性,分析了分子量分布对LDPE化学结构、热稳定性、平均分子量、表面微观形貌和力学性能的影响规律。结果表明分子量分布越宽,LDPE不饱和度增长越剧烈,支化作用增长越显著;分子量分布越窄,羰基指数增长越快;分子量分布对于分子结构的断链行为并无影响。分子量分布指数越大,LDPE起始热分解温度和失重5%对应温度下降更快,热稳定性更容易变差,平均分子量下降更多,表面微观形貌老化现象越严重;弯曲强度和冲击强度受影响更显著,指数为6.0的LDPE老化24 d冲击强度就已丧失。分析认为,分子量越大、分布越窄表明分子链越长、短分子链越少,与氧接触而产生自由基的概率也越小,因此聚乙烯分子量分布越宽,材料越容易老化。     

连续CF增强PEEK复合材料层压板的制备工艺

采用熔融浸渍法制备了连续碳纤维(CF)增强聚醚醚酮(PEEK)复合材料预浸带,并层压成型制备复合材料层压板。研究了成型温度、成型压力、成型时间、纤维含量等因素对复合材料层压板力学性能的影响。结果表明,在成型温度为370℃、成型压力为12 MPa、成型时间为70 min、纤维含量为61%的工艺条件下,连续CF增强PEEK复合材料层压板的力学性能达到最优值,弯曲强度和弯曲弹性模量分别达到(1 750.76±49.13)MPa和(107.54±6.35)GPa,层间剪切强度达到(100.04±6.88)MPa,缺口冲击强度为(84.44±1.54)k J/m2。随着冷却速率的增大,复合材料层压板的弯曲性能和层间剪切强度下降,而缺口冲击强度提高。SEM分析表明,复合材料层压板的界面粘结良好。     

PHBV/PBAT混物形态与性能研究

通过熔融共混的方法制备了完全生物降解的羟基丁酸-羟基戊酸共聚物/丁二醇-己二酸-对苯二甲酸共聚物共混材料(PHBV/PBAT),研究了 PHBV/PBAT 共混物的相形态、力学性能和热性能。结果表明,PBAT 为50%(质量含量,下同)时,共混物断裂伸长率为55%,缺口冲击强度为542 J/m,分别为改性前 PHBV 的19倍和22.6倍,显著提高了 PHBV 的韧性。SEM 照片显示,30%的 PBAT 以分散相存在 PHBV 基体中;当 PBAT 超过50%后,PBAT 可能形成连续相,在受到外力过程中发生大形变从而吸收较多的能量。DSC 研究表明,PBAT 的加入抑制了PHBV 的结晶过程,使 PHBV 结晶温度降低20～40℃。     

聚酰胺类热塑性弹性体含量对PLLA/三元聚酰胺共混物形态和性能的影响

以聚酰胺类热塑性弹性体（TPAE）为增容剂增容左旋聚乳酸（PLLA）与三元聚酰胺共混物,采用扫描电子显微镜（SEM）、差热扫描量热仪（DSC）、X射线衍射仪（XRD）等研究了TPAE含量对PLLA/三元聚酰胺（70/30,质量比,下同）共混物的形态、力学性能和热性能的影响。力学性能研究结果表明,添加TPAE后,PLLA/三元聚酰胺共混物的拉伸强度、断裂伸长率、缺口冲击强度显著提高,TPAE含量为5份时,共混物的断裂伸长率为370 %,缺口冲击强度为90 J/m,拉伸强度为39 MPa;SEM分析表明,添加TPAE后,共混物中三元聚酰胺相的粒径显著变小;DSC与XRD分析结果表明,TPAE含量对PLLA/三元聚酰胺共混物的熔融行为和结晶行为无明显影响,而共混物拉伸后,其结晶度显著提高。     

阻燃型玻纤增强PA10T复合材料的热氧老化性能

采用溴化环氧树脂对聚对苯二甲酰葵二胺(PA10T)进行改性,并通过熔融共混法制备阻燃型玻璃纤维(GF)增强PA10T复合材料,采用人工加速热氧老化手段,研究了热氧老化对其力学性能的影响,并用扫描电子显微镜(SEM)对复合材料的冲击断面形貌进行观察。结果表明,随热氧老化时间增加,复合材料的拉伸强度、弯曲强度和缺口冲击强度均下降明显,分子链松弛过程减弱;老化10 d后,复合材料的弯曲弹性模量仅略有下降而储能模量达到最大值,表明在热氧老化初期PA10T分子链之间发生了微交联,但随老化时间继续增加,两者均下降明显。SEM结果表明GF与树脂基体之间界面粘接作用的强弱是影响材料热氧老化性能变化的主要因素。     

PC/PBT合金增韧改性的研究

研究了“核-壳”结构的丙烯酸酯类(ACR)抗冲改性剂对PC／PBT(80／20)合金力学性能和耐热性的影响；并用扫描电子显微镜对共混物的微观形态结构进行了分析。结果表明：随ACR抗冲改性剂的增加，共混物的冲击强度先增后降，当ACR的用量为15份时，出现最大值；同时共混物的拉伸强度和维卡软化温度都降低。     

高温老化对碳纤维增强双马来酰亚胺树脂基复合材料力学性能的影响研究

本文对国产碳纤维增强双马来酰亚胺树脂复合材料进行了高温老化力学性能测试和分析,通过扫描电子显微镜分析了高温老化对碳纤维／双马复合材料力学性能的影响。结果表明,老化1000h的力学性能未出现明显下降趋势,纤维与树脂基体粘接牢固,界面完好,该复合材料的高温老化性能优异。     

硅微粉改性PI/PPS/GF复合材料的制备及性能

采用双螺杆挤出机挤出工艺,制备了硅微粉改性聚酰亚胺(PI)/聚苯硫醚(PPS)/玻璃纤维(GF)复合材料。研究了PPS用量和硅微粉用量对PI/PPS/GF复合材料力学性能、动态力学性能、线膨胀系数和热性能的影响。复合材料拉伸强度、弯曲强度、悬臂梁无缺口冲击强度和初始储能模量随PPS用量增加而逐渐降低,线膨胀系数和熔体质量流动速率随之增加;材料力学性能随硅微粉用量增加先增加后减小,线膨胀系数和熔体质量流动速率随之增加而明显降低。差示扫描量热仪(DSC)数据分析表明,PPS材料的加入使复合材料在230~240℃出现了结晶峰,硅微粉使初始结晶温度变高;复合材料的热稳定性能随着熔融硅微粉用量增加而增加。     

PA66/RTMB/GF复合材料的结构与力学性能研究

采用玻璃纤维(GF)、反应性增韧母料(RTMB)与PA66热机械反应性共混制备出了PA66/RTMB/GF复合材料.用IR、SEM、力学性能测定等方法研究了PA66/RTMB/GF复合材料的化学结构、断面形态及力学性能.结果表明:PA66/RTMB/GF中RTMB、GF和PA66间形成了化学键连接,GF和PA66间呈柔性界面结合;PA66/RTMB/GF质量比为60/10/30的复合材料的拉伸屈服应力、弯曲弹性模量、悬臂梁缺口冲击强度分别提高到原料PA66的1.73倍、2.72倍、3.86倍.