超支化聚酯对PET非等温结晶行为的影响

利用差示扫描量热法(DSC)研究了2种不同端基的超支化聚酯(HBP)对聚对苯二甲酸乙二醇酯(PET)非等温结晶行为的影响,用莫志深法对非等温结晶动力学进行了分析,通过偏光显微镜(POM)观察了各体系的结晶形态。结果表明:PET和PET/HBP的非等温结晶过程可用莫志深动力学方程来描述;HBP的加入并没有改变PET的结晶成核机理和生长方式;端羟基超支化聚酯(HBP-OH)的加入使得PET的结晶速率变慢,对晶体生长起到了抑制作用;端十六烷基超支化聚酯(HBP-C16)在PET中起到了很好的结晶促进剂作用,能够促进PET结晶。     

脂肪族超支化聚酯的端链结晶行为

以长链烷基酸为改性剂,对以三羟甲基丙烷为核、二羟甲基丙酸为支化单体合成的第三代端羟基超支化聚酯进行端基改性,采用羟值滴定和核磁共振氢谱(1H-NMR)表征超支化聚酯的改性程度,采用差示扫描量热分析(DSC)和广角X射线衍射(WAXD)研究了端烷烃链长度和端基改性程度对超支化聚酯相转变行为和结晶行为的影响。结果表明,超支化聚酯的结晶归因于长链端烷烃的有序排列,端烷烃链越长,端烷基超支化聚酯的冷结晶温度、热结晶温度和熔融温度均逐渐升高;端烷烃链越长或改性程度越高,衍射峰强度越大,晶粒尺寸变小。进一步用DSC研究了端十八烷基超支化聚酯的非等温结晶行为并用Ozawa法对其非等温结晶动力学进行了分析,发现其成核方式为异相成核,生长方式为针状晶体的一维生长。     

端基对脂肪族超支化聚酯性能的影响

用十八酸对端羟基脂肪族超支化聚酯进行改性,采用差示扫描量热分析(DSC)、热重分析(TG)、旋转流变仪研究了不同端基对超支化聚酯的玻璃化转变温度、热稳定性和流变性能的影响.结果表明,端基对超支化聚合物的玻璃化转变和结晶有显著影响,通过端基长链烷烃链段的有序排列可以显著提高超支化聚合物的结晶性能;端羟基超支化聚酯的热分解...     

端基对超支化聚合物改性UHMWPE性能的影响

以3种不同端基的超支化聚酯(HBP)分别对超高相对分子质量聚乙烯(UHMWPE)进行共混改性,研究了HBP的端基类型和用量对UHMWPE/HBP共混物力学性能和流变性能的影响。结果表明:随着端羟基超支化聚酯HBP-OH、端苯基超支化聚酯HBP-Bz及端十六烷基超支化聚酯HBP-C16加入量的增大,UHMWPE/HBP共混物的拉伸强度不断降低,断裂伸长率呈现先增大后减小的趋势。在UHMWPE中加入HBP-C16后,共混物的复数黏度呈现上升的趋势。HBP-OH和HBP-Bz的加入量增大能增强UHMWPE大分子链的活动能力,改善了UHMWPE的加工流动性能。     

端羟基超支化聚酯的稳定化改性及热分解行为

以长链烷基酸为改性剂,对以三羟甲基丙烷为核、二羟甲基丙酸为支化单体合成的端羟基超支化聚酯进行端基稳定化改性。采用羟值滴定和核磁共振氢谱(1H-NMR)表征超支化聚酯的改性程度;采用热重-微商热重分析(TG-DTG)研究了代数、端基类型以及改性程度对超支化聚酯热稳定性和热分解行为的影响。结果表明,将不稳定的端羟基转变为热稳定的端烷基后,超支化聚酯的热稳定性明显提高,且改性程度越高,或长烷烃链越短,聚合物的热稳定性越好。超支化聚酯的热分解主要包括两个失重阶段,分别对应于由大量端基所组成的"壳"的破坏以及由大量C-C单键所组成的骨架(即"核")解体。极性端羟基的含量越小或非极性端烷基的含量越大,第一失重峰越不明显。     

红外光谱法测定巯基丙酸-溶聚丁苯橡胶接枝量

利用红外光谱法建立了巯基丙酸接枝改性溶聚丁苯橡胶（SSBR）中巯基丙酸接枝量的快速测定方法。结果表明,以700 cm-1处吸收峰为内标峰、1 712 cm-1处吸收峰为定量特征峰时,吸光度比值与接枝量的线性曲线相关因数为0.984 5,方法的精密度较好。     

聚酯中亚甲基含量对其热性能影响研究

以聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丙二醇酯(PTT)、聚对苯二甲酸丁二醇酯(PBT)为研究对象,采用差示扫描量热仪考察了其亚甲基含量对聚酯的玻璃化转变、熔融结晶行为、冷结晶行为等热性能的影响,通过Avrami方程、Arrhenius方程计算了3种聚酯的结晶物理常数;采用热失重分析仪分析了PET,PTT,PBT的热稳定性。结果表明:PET的玻璃化转变温度为77.24℃,而PTT,PBT未见明显的玻璃化转变;随着亚甲基含量增加,聚酯的熔点下降,冷结晶峰温度上升,其中PTT在67.8,192.0℃处存在两个冷结晶峰;3种聚酯的熔融结晶行为均符合Avrami方程;随着亚甲基含量增加,聚酯的熔融结晶热焓、Avrami指数依次增大,半结晶时间依次减小,校正后的非等温结晶动力学常数变化不大;3种聚酯的冷结晶程度均弱于熔融结晶,PET,PTT,PBT的冷结晶程度分别约为熔融结晶的70%,10%,7%,冷结晶速度依次变快;随着聚酯中的亚甲基含量增加,聚酯的热稳定性变差;3种聚酯的热降解过程可分为3个阶段,PTT,PBT初始分解温度低于PET,第一、第二降解活化能高于PET,但第三降解活化能低...     

含氟超支化聚酯的合成及其性能研究

利用十三氟辛酸对超支化聚酯进行端基改性,得到了含氟超支化聚酯。采用傅里叶变换红外光谱仪、差示扫描量热分析仪等对聚合物进行了表征和分析。结果表明:十三氟酸成功接枝到超支化聚酯上,含氟超支化聚酯的玻璃化转变温度为-20.5℃,含氟超支化聚酯溶液在固含量高达70%时仍具有较低的黏度,该聚合物成膜性好,涂膜的附着力为1级,柔韧性为1 mm,铅笔硬度2 H,抗冲击强度4.9 J/cm2,与水的接触角为105°,具有良好的表面疏水性。     

红外光谱法测定巯基丙酸-溶聚丁苯橡胶接枝量

利用红外光谱法建立了巯基丙酸接枝改性溶聚丁苯橡胶(SSBR)中巯基丙酸接枝量的快速测定方法。结果表明,以700 cm~(-1)处吸收峰为内标峰、1 712 cm~(-1)处吸收峰为定量特征峰时,吸光度比值与接枝量的线性曲线相关因数为0.984 5,方法的精密度较好。     

端环氧基超支化聚酯的合成及应用

本文以季戊四醇为心核结构、2,2-二羟甲基丁酸为重复单元、对苯甲磺酸为催化剂,合成了端羟基超支化聚酯;然后,采用环氧氯丙烷对超支化聚酯的端羟基进行环氧官能化,合成端环氧基超支化聚酯,采用GPC、13CNMR及1H-NMR图谱对结构进行表征。采用端环氧基超支化聚酯做增韧剂,研究其对双酚A环氧树脂力学性能的影响,探讨了端环氧基超支化聚酯对环氧树脂固化体系力学性能及韧性的影响。     

聚丙烯与超支化聚酯共混物的非等温动力学(英文)

Polypropylene (PP) with different contents of the second generation hyperbranched polyester (HBP) is prepared by melt blending method. The non-isothermal crystallization kinetics of PP and PP/HBP blends is investigated under differential scanning calorimetry (DSC). The Mo equation is used to analyze the DSC data. The results show that the Mo theory is suitable for crystal ization kinetics of the blends. Fast cooling rate is not good for crys-tallizing and nucleating. The values of half crystal ization time (t1/2), crystal ization enthalpy (ΔHc) and temper-ature range (ΔT) of PP/HBP blends decrease when HBP is added. The required cooling rate of PP is higher than that of PP/HBP blends in order to reach the same relative crystal inity. Crystallization rate increases with the ad-dition of HBP. The crystallization rate reaches a maximum when the content of HBP is 5%. In addition, the activa-tion energies of PP and PP/HBP blends are calculated by Kissinger equation, revealing that the content of HBP has a little effect on the crystallization activation energy.     

不同代数端羟基超支化聚酯及其二元共混物的流变行为

系统研究了消除热历史后的G1~G5端羟基超支化聚酯熔体及组分质量比为1∶1的二元共混物的流变行为。结果表明,无论是稳态剪切测试还是振荡测试,消除热历史后的G2~G5端羟基超支化聚酯熔体均表现为牛顿流体的流变行为。G3~G5端羟基超支化聚酯的流变行为均遵循Cox-Merz方程。G2端羟基超支化聚酯在振荡测试的高频区出现了剪切增稠现象。对于组分质量比为1∶1的低代/高代端羟基超支化聚酯二元共混物,无论是稳态剪切还是振荡剪切,只要一种组分是牛顿流体,那么二元共混体系也是牛顿流体。高代数组分决定了二元共混物的流变特性,而低代数组分主要影响二元共混物的黏度。     

超支化聚酯共混聚合物等温结晶动力学研究

采用三羟甲基丙烷、2,2-二羟甲基丙酸、对甲苯磺酸反应制备第2～5代超支化聚酯(HBP),将其按质量分数10%分别与聚丙烯(PP)和聚甲醛(POM)共混,用差示扫描量热法(DSC)研究了共混物的等温结晶动力学。结果表明,用Avrami方程描述PP/HBP和POM/HBP的结晶动力学较理想。在PP中,HBP主要起成核作用;在POM中,HBP主要起稀释作用;第2代HBP成核作用最弱,稀释作用最强,第5代HBP稀释作用最小。     

Rheological properties of hyperbranched polymer/poly(ethylene terephthalate) reactive blends

The rheological properties in solution, in shear and in uniaxial elongation of poly(ethylene terephthalate) (PET) reacted together with hyperbranched polymers (HBPs) were investigated. Two different PET grades, of low and high molecular weights, were compounded with sub‐ to over‐stoichiometric concentrations of HBPs of second and fourth pseudo‐generation, and subsequently subjected to a solid‐state polycondensation (SSP). The formation of microgels, which occurs at high HBP concentration, gave rise to a large increase in melt elasticity and a related decrease in melt strength. At low HBP concentrations, the complex viscosity of the unreacted HBP/PET was considerably reduced, thus demonstrating a lubrication effect of the HBP molecules. During SSP, the intrinsic and shear viscosities exhibited a gradual increase, which was similar for both PET and HBP/PET blends, and was correlated to an increase in molecular weight, through linear‐chain extension and branching reactions. The elongational viscosity of the reactive blends was also increased as a function of reaction time, and this increase was much larger in the case of the HBP/PET blends. A 400% increase in melt strength of the PET was obtained by combining SSP and trace amounts of an HBP of second generation, without any decrease in drawability.     

Nonisothermal crystallization kinetics of AB2 hyperbranched polymer‐filled polypropylene

In this article, nonisothermal crystallization kinetics of polypropylene (PP) and AB₂ hyperbranched polymer (HBP)‐filled PP have been investigated by differential scanning calorimetry. The Avrami analysis modified by Mandelkern and a method combined with Avrami and Ozawa equations were employed to describe successfully the nonisothermal crystallization kinetics of samples. The conclusion showed that HBP can prompt crystallization effectively. Furthermore, in blends of different HBP contents, the value of t_1/2 became smaller with increasing HBP content; however, the crystallization rate of the blend decreased slightly when content of HBP is 5%. An increase in the Avrami exponent showed that addition of HBP influenced the mechanism of nucleation and the growth of PP crystallites. The possible explanation could be attributed to the fractal structure of HBP. The polarized micrographs showed that HBP acts as a heterogeneous nucleation agent, and the nucleation efficiency has increased remarkably in HBP/PP blends. POLYM. ENG. SCI., 53:2535–2540, 2013. © 2013 Society of Plastics Engineers     

Isothermal crystallization kinetics of AB<Subscript>3</Subscript> hyperbranched polymer (HBP)/polypropylene (PP) blends

In this paper, the isothermal crystallization kinetics of pure isotactic polypropylene (iPP) and iPP with 5% AB₃ hyperbranched polymer (HBP) added had been investigated by differential scanning calorimetry (DSC). During isothermal crystallization, the crystallization rate of the blends was higher than those of iPP remarkably. Moreover, the value of t _½ became smaller with increasing the HBP molecular weight in blends, however, the crystallization rate of the blend decreased when the higher molecular weight HBP (\( \bar{M}_{n} \) = 12,500) was added. The crystallization rate of the blends was more sensitive to temperature than that of iPP. An increase in the Avrami exponent may be attributed to the fractal structure of hyperbranched polymer.     

Study of phenyl‐terminated hyperbranched polyester as a special β‐nucleating agent on the toughness of isotactic polypropylene

The effect of phenyl‐terminated hyperbranched polyester (HBP‐Bz) with different generation (the first generation and the fourth generation) as a special β‐nucleating agent on the toughness of isotactic polypropylene (iPP) was investigated by dynamic rheological measurements, scanning electron microscopy, differential scanning calorimetry, wide‐angle X‐ray diffraction, polarized optical microscopy, and mechanical properties measurements. The results show that the β nucleating activity of HBP‐Bz significantly depends on its concentration and molecular structure. The relative content of β‐crystal form (K_β) increases with the increasing HBP‐Bz percentage reaches a maximum and then decreases as HBP‐Bz percentage further increases. The K_β values of iPP/HBP‐G1‐1% and iPP/HBP‐G4‐1% blends are 26.52% and 20.80%, respectively. When compared with HBP‐G4, HBP‐G1 has incompact molecular structure, facilitating the π–π interaction between phenyl‐terminated groups and the helix chains of iPP crystallize on it, and therefore relatively good dispersibility, high β nucleating activity and excellent toughening effect are obtained. The impact strength of iPP was dramatically improved, especially with addition of 1 wt% HBP‐G1. POLYM. ENG. SCI., 59:E133–E143, 2019. © 2018 Society of Plastics Engineers     

Blends of thermoplastic polyesters with amorphous polyamide. I. Thermal and crystallization behavior

The thermal and crystallization behavior of blends of three thermoplastic polyesters with different degrees of crystallizability, with an amorphous aromatic polyamide is reported. The thermoplastic polyesters used in the investigation were poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET) and a co-polyester of 1,4 cyclohexane-dimethanol, ethylene glydol and terephthalic acid (PETG). The blends exhibited a single glass transition temperature indicating mlseibility in the amorphous phase. The results of thermal analysis indicated that the crystallization of all the three polyesters is facilitated in the molten phase as a result of blending. The blending significantly Increased the degree of crystallinity of PET, but there was no change in the crystallinity of PBT. It is thus observed that the extent of change in both the crystallization rate and the degree of crystallinity of polyesters depend on the inherent crystallizability of the individual polyester.     

An in-depth study on crystallization kinetics of PET/PLA blends

The crystallization behavior and mechanical properties of PET/PLA blends with various amounts of PLA were investigated using a wide angle X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and tensile analyses. The crystallization rate and relative crystallinity of the PET/PLA blends were studied by theoretical models of Kissinger, Avrami, Ziabicki and Ozawa. The WAXD analysis showed that the PLA phase was wholly amorphous in all blends after cooling from the melt to ambient temperature. Crystallization behavior assessments on PET/PLA blends suggest that PLA acts as a nucleating agent for PET phase leading to an increase in the initial and peak crystallization temperatures. Kissinger’s model showed a rise in activation energy up to 72% for the PET/PLA blends containing 30 wt% PLA. Ziabicki’s model gave a minimum value for kinetic parameter in PET/PLA (70/30 w/w) due to the nucleating action of PLA. On the other hand, PLA acted as a retarder for chain segments of PET tending to diffuse through the surface of growing crystals. Therefore, at an optimal composition of PET/PLA, crystallization occurs appropriately. However, an increase in PET content leads to fall in ductility, tensile strength, modulus, elongation-at-break, and fracture toughness of PET/PLA blends.     

Miscibility and crystallization behaviour of biodegradable blends of two aliphatic polyesters. Poly(3-hydroxybutyrate-co-hydroxyvalerate) and poly(butylene succinate) blends

Blends of poly(3-hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(butylene succinate) (PBSU), both biodegradable semicrystalline polyesters, were prepared with the ratio of PHBV/PBSU ranging from 80/20 to 20/80 by co-dissolving the two polyesters in chloroform and casting the mixture. Differential scanning calorimetry (DSC) and optical microscopy (OM) were used to study the miscibility and crystallization behaviour of PHBV/PBSU blends. Experimental results indicate that PHBV is immiscible with PBSU as shown by the almost unchanged glass transition temperature and the biphasic melt. Crystallization of PHBV/PBSU blends was studied by DSC using two-step crystallization and analyzed by the Avrami equation. The crystallization rate of PHBV decreases with the increase of PBSU in the blends while the crystallization mechanism does not change. In the case of the isothermal crystallization of PBSU, the crystallization mechanism does not change. The crystallization rate of PBSU in the blends is lower than that of neat PBSU; however, the change in the crystallization rate of PBSU was not so big in the blends. The different content of the PHBV in the blends does not make a significant difference in the crystallization rate of PBSU.