Electrically Conductive Carbon Black/Poly(Ethylene Terephthalate)/Polyethylene Microfibrillar Composite: The influence of CaCO3 Nanoparticles

The influence of a complex filler system on the electrical properties of a microfibrillar conductive polymer composite (MCPC) is discussed. By adding insulating filler, nano-CaCO₃, to carbon black (CB)-filled MCPC, the morphology of the poly(ethylene terephthalate) (PET) microfibrillar phase was tailored according to the ratio of CB/nano-CaCO₃, and so were the electrical properties of MCPC. It was found that nano-CaCO₃ did not influence electrical properties in a monotone way. With an increase in nano-CaCO₃ content, on one hand, the surface of the microfibrils became smoother, which jeopardized the conductivity of the MCPC. At the same time, the nano-CaCO₃ particles substituted for the CB particles on the surface of the microfibrils and further decreased conductivity. On the other hand, longer and better-defined microfibrils could form, which enhanced the conductive network and increased the conductivity of the MCPC. As a result, the percolation threshold changed little compared to the common CB-filled MCPC.     

Isothermal Crystallization Kinetics of Poly (Ethylene Terephthalate) – Cellulose Acetate Blends

Summary The isothermal crystallization exotherm was determined at three temperatures for two blends of bottle regrind Poly(ethylene terephthalate) (PET) with Cellulose Acetate (CA) as derived by an extrusion process, as well as for the pristine PET. It was observed that the addition of 10 weight-percent CA increased the crystallization rate of PET manifold, which resulted in improved moldability with faster cycle times. The crystallization was observed to be very fast with initiation times of the order of a few seconds, perhaps due to the impurities present in the bottle regrind PET and the synergistic effects of the CA particles. The fast rate of crystallization and high melting point of PET (250 C), and the degradation of CA at temperatures higher than 260 C made extrusion of PET – CA blends difficult. However, increasing the CA content in the blend to 30% decreased the rate of crystallization of PET resulting in an improved extrusion process, but slower cycle times.     

碳纳米管/聚乳酸复合材料非等温结晶动力学

研究了聚乳酸(PLA)与多壁碳纳米管(MWNTs)/PLA复合材料的非等温结晶动力学。利用硅烷偶联剂KH-550改性碳纳米管,并用溶液共混法制备MWNTs/PLA复合材料。利用DSC研究了材料的结晶过程,所得的降温曲线表明基体中的碳纳米管可以提高材料的结晶温度范围和结晶放热焓。采用Jeziorny法和Mo法研究了PLA与MWNTs/PLA复合材料的非等温结晶动力学,结果表明,适量的碳纳米管有效地起到了成核剂的作用,提高了材料的结晶速率。     

PBT聚酯非等温结晶动力学

用差示扫描量热分析(DSC)法研究聚对苯二甲酸丁二酯(PBT)的非等温结晶动力学,并分别用Ozawa、Jeziorny和综合因素法等三种方法来处理PBT的非等温结晶数据。结果表明,PBT非等温结晶过程与Ozawa动力学方程相吻合,而不符合用Jeziorny方法处理的Avrami动力学方程;综合考虑温度和结晶程度对聚合物结晶速度的影响,PBT非等温结晶过程符合结晶动力学方程:dG(t)/dt=e~(-E/R(T-T_R)+F(T_m-T+α))(1-G(t))~nG(t)~m。     

Non-isothermal Crystallization Behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) Blends

Summary Non-isothermal crystallization behavior of Poly(ethylene terephthalate)/Poly(trimethylene terephthalate) blends was investigated by XRD and DSC. By XRD spectra analysis, it could be concluded that PET and PTT crystals coexisted. They did not form the cocrystals due to different chemical structures. The Avrami equations modified by Jeziorny and Ziabicki’s kinetic crystallizability analysis were employed to describe the non-isothermal crystallization process of PET/PTT blends. The results suggested that the entanglement of the two polymer chains decrease the crystallizability of PET and PTT in blend. The crystallization activation energies of the blend evaluated by the Friedman method also indicated that the presence of two components in the blends hinders the crystallization process of both components.     

间苯二甲酸改性PET的结晶行为研究

应用 DSC研究了间苯二甲酸 (IPA)改性 PET的结晶行为。结果表明 :由于第三单体破坏了 PET大分子结构的规整性 ,导致改性聚酯熔点下降 ,冷结晶温度上升 ,热结晶温度下降 ;与常规 PET相比 ,较慢的冷却速度就可使熔融状态的改性 PET保持无定形状态。     

弹性体增韧PET/GF复合体系性能的研究

为提高聚对苯二甲酸乙二醇酯(PET)/玻璃纤维(GF)复合材料的韧性,分别采用乙烯-正丁基丙烯酸酯-甲基丙烯酸缩水甘油酯共聚物(PTW)、马来酸酐接枝POE(493D)及甲基丙烯酸甲酯-丙烯酸酯核壳共聚物(Exl3300)对其进行改性,并研究了PET/GF/弹性体三元体系的力学性能、热性能和动态流变行为.结果表明同493D和Exl3300相比,PTW对PET/GF复合材料的增韧效果更佳.当弹性体质量含量为12%时,PET/GF/PTW复合材料冲击强度有了很大的提高,同时材料的力学性能和热性能得到了很好的保持.动态流变的数据表明,PTW、493D和Ex13300都显著提高了PET/GF复合材料的动态黏度.     

UHMWPP／UHMWPE合金纤维非等温结晶动力学研究

运用DSC手段研究了UHMWPP／UHMWPE合金纤维的等温结晶行为，对所得的实验数据用修正Avrami方程的Jeziorny法进行处理，发现随冷却速率的提高，半结晶的时间t1/2缩短，表明冷却速率加快时，结晶速率也随之加快，纯UHMWPP主要是以三维球晶的方式进行结晶生长，UHMWPE的加入起到核剂的作用，随着成核剂含量的增加，UHMWPP的结晶维数将降低.     

Chemical Degradation of Poly(Ethylene Terephthalate)

The possibility of converting polyethylene terephthalate (PET) waste into terephthalic acid as a primary material by using different techniques through trans-esterification, with an alcohol and through hydrolysis in basic medium, has been investigated. In addition, utilization of activating agents such as inorganic salts and phase transfer catalysts has been investigated.Mineral water and beverage bottles were collected, cleaned and crushed into flakes suitable for the intended experiments. Also, the main products of chemical conversion of such wastes were isolated and confirmed by authentication with standard terephthalic acid through Thin Layer Chromatography (TLC) technique. The reaction yield % was determined to optimize the corresponding experimental conditions and the obtained results have been presented and discussed.     

PP-g-VAc非等温结晶动力学的研究

用DSC对两种不同接枝率的聚丙烯接枝醋酸乙烯酯共聚物(PP g VAc)进行了非等温结晶动力学的研究,采用Reziorny修正的Avrami方程和莫志深提出的R t法对非等温结晶动力学进行了分析。研究结果表明:这两种方法能够很好地对PP g VAc的非等温结晶过程进行描述,VAc接枝链由于破坏了分子链的规整性并产生部分交联,导致结晶速率和结晶能力降低:结晶时间(t1/2)增大、结晶速率常数(Zc)降低,接枝共聚物的结晶焓降低,聚丙烯结晶成核和生长的方式没有改变,高接枝率下PP(GP=14 8%)的结晶温度上升,结晶参数F(T)随接枝率而增大。     

聚丙烯固相接枝甲基丙烯酸乙酯的非等温结晶行为

利用差示扫描量热法(DSC)研究了聚丙烯(PP)及聚丙烯固相接枝甲基丙烯酸乙酯(PP-g-EMA)在不同冷却速率下的非等温结晶行为,并用Jeiorny法、MO法和Kissinger法处理了数据。结果表明:固相接枝EMA对PP的结晶起到异相成核的作用,提高了PP的结晶温度和结晶度;MO法比较适用于研究本体系的非等温结晶动力学,EMA 的引入提高了PP的结晶速率,改变了成核机理和晶体生长方式;用Kissinger法计算结晶活化能时发现EMA的接枝提高了PP的结晶活化能,表明接枝EMA阻碍了PP分子链在结晶时的运动。     

辛烯共聚聚乙烯树脂非等温结晶动力学

利用差示扫描量热仪研究了共聚单体含量和支链分布对辛烯共聚聚乙烯树脂非等温结晶动力学的影响。结果表明,共聚单体含量越多,支链分布越均匀,半结晶时间越长,结晶增长速率常数（Zc）越小,冷却速率越大;结晶生长维数随着降温速率的增加在2~3之间变化;随着结晶度的增加,Avrami指数（n）与Ozawa指数（m）的比值（a）变化较小。     

尼龙11/HGB复合材料的非等温结晶动力学

采用熔融共混法制备了尼龙(PA)11/空心玻璃微珠(HGB)(PA11/HGB)复合材料,应用差示扫描量热(DSC)仪研究了不同HGB用量下的PA11/HGB复合材料的非等温结晶过程,采用Jeziorny法和Mo法研究了复合材料的非等温结晶动力学,采用X射线衍射(XRD)仪研究了复合材料的晶型变化情况。DSC结果表明,随着降温速率的增加,复合材料的结晶温度总体上降低,结晶温度区间变宽;HGB在PA11基体中起到了异相成核作用。Jeziorny法不适用于PA11/HGB复合材料的非等温结晶动力学研究,而Mo法较为适合,其研究结果表明适量的HGB具有加速PA11基体结晶的作用,但当HGB用量达到8份后,这种作用趋于稳定。XRD结果表明,HGB可诱导PA11基体生成新的β晶。     

PET聚酯化学解聚进展

废ＰＥＴ聚酯化学解聚是实现其循环利用的重要途径,本文介绍了目前国内外主要的解聚方法及研究进展状况,指出我国应大力加强该领域的研究。     

Spherulitic Morphology and Crystallization Kinetics of Poly(vinylidene fluoride)/Poly(vinyl acetate) Blends

Spherulitic morphology and crystallization kinetics of the blends of poly(vinylidene fluoride) (PVDF) and poly(vinyl acetate) (PVAc) prepared by solution casting films have been investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The results suggested that PVAc was mainly segregated into the interlamellar and/or interfibrillar regions due to the volume-filling spherulitic morphology observed. As for the results of crystallization kinetics, it was found that both the PVDF spherulitic growth rate (G ^PVDF) and the overall crystallization rate constant (k _n ) were depressed with either the addition of PVAc component or the increase of crystallization temperature (T _c). The kinetics retardation was attributed to the decrease in PVDF molecular mobility and dilution of PVDF concentration due to the addition of PVAc, which has a higher glass transition temperature (T _g).     

Surface Modification and Vapor-Induced Response of Poly(Vinylidene Fluoride)/Carbon Black Composite Conductive Thin Films

A novel polymer sensing film was prepared by filling carbon blacks (CBs) into alkali-treated poly(vinylidene fluoride) (PVDF) matrices under ultrasonication. The microstructure, thermoproperties and crystalline behavior were investigated by FTIR, WAXD and DSC. The percolation behavior and vapor-induced response were examined, and the relationship between structure and response was elucidated. The results indicated that the reaction occurred in non-crystal regions, and had no effect on the crystal region and the main chains. The introduction of some functional groups and the aggregate behavior change in the non-crystal regions altered the interaction between polymer and solvent molecules, and further affected vapor response.     

Highly Exfoliated Poly(Ethylene Terephthalate)/Clay Nanocomposites via Melt Compounding: Effects of Silane Grafting

The ammonium intercalated montmorillonite (A-MMT), especially acid treated montmorillonite (H-S-A-MMT), which experienced silane grafting treatment, exhibited highly exfoliation state in poly(ethylene terephthalate) (PET) matrix. It can be explained that the shear stress was transferred effectively from molten polymer to clay layers during melting processing due to the enhanced polymer-clay interaction by the grafted silane, leading to the slippage and peeling of clay sheets. Furthermore, the equilibrium melting point reduction of highly exfoliated nanocomposite calculated by the Hoffman-Weeks formula exhibited great miscibility between clay and polymer, which was proved by the Nishi-Wang equation.     

聚对苯二甲酸丁二醇酯/多壁碳纳米管复合材料的流变及结晶行为

采用熔融共混的方法制备了对聚对苯二甲酸丁二醇酯(PBT)/多壁碳纳米管(MWNT)复合材料,研究了复合体系的流变及结晶行为.结果表明MWNT具有显著的增强作用,使得复合体系低频区的模量出现类固态黏弹响应,这源于MWNT逾渗网络结构的形成.MWNT的加入并未改变PBT的α晶型结构,但其异相成核作用却能有效地促进复合体系PBT基体的结晶.     

ABS高胶粉对ABS/PET/SMA合金的增韧研究

采用ABS高胶粉(ABSHR)对丙烯腈-丁二烯-苯乙烯共聚物(ABS)/聚对苯二甲酸乙二醇酯(PET)/苯乙烯-g-马来酸酐(SMA)合金进行增韧改性;探讨了ABSHR对合金体系的力学性能、耐热性和流变性能的影响;同时采用扫描电镜(SEM)对其断面形态进行表征。研究结果表明:ABSHR可以显著提高ABS/PET/SMA合金的冲击强度和断裂伸长率。当ABSHR加入量为20份时,冲击强度从7.7kJ/m2提高到17.6kJ/m2,断裂伸长率从24.6%提高到60.2%;而体系的拉伸强度和弯曲强度有不同程度的降低;维卡软化温度随着ABSHR的增加而逐渐降低;ABSHR增韧体系的剪切黏度和假塑性均得到提高。未增韧的合金断面较平整;而增韧的合金断面产生大量橡胶撕裂带,并伴有应力发白现象。