动态流变学论文：动态流变学高密度聚乙烯超高分子量聚乙烯

动态流变学论文：动态流变学高密度聚乙烯超高分子量聚乙烯
【中文摘要】聚合物动态流变学是研究聚合物结构与流变行为关系的有效方法,特别是对聚合物多相体系,其形态结构的演化过程可
以通过动态流变学方法有效地考察。

近年来,对聚烯烃(主要指聚乙烯)共混体系动态流变学,多集中在共混体系的热流变行为与相行为的关系研究上,对于加工过程中,体系相形态的转变及其与流变学行为关
系缺少必要的研究。

本文拟以高密度聚乙烯/超高分子量聚乙烯(HDPE/UHMWPE)共混体系为模型,重点讨论动力学因素,包括加工温度、剪切速率、填料含量等,对体系动态流变学行为的影响,并在此基础上对体系形态结构的演化作出推断。

研究表明,在UHMWPE含量为10wt%的情况下,HDPE/UHMWPE体系,加工温度和剪切速率的改变使得体系动态流变学行为发生明显的变化,且剪切速率引起的变化更为显著。

主要表现在:随着剪切速率的提高,体系应变扫描线性黏弹性区间缩小,储能模量提高。

动态频率扫描中,低频区的储能模量和损耗模量均明显提高,高频区则相互重叠在一起,二者交点也向低频方向偏移;低频区间的tanδ逐渐向1靠近,表明体系储能模量与损耗模量在提高的过程中,储能模量的提高程度比损耗模量大;低频区复数黏度逐
渐提高,表明体系分子流动性变差。

此外,等温时间扫描结果表明,体系结晶诱导时间缩短,结晶过程加快,结晶最终模量发生改变。

以上结果表明体系的弹性和黏性逐渐增强,但弹性增加的程度更大,体系流
变行从liquid-like向solid-like行为转变。

对于HDPE/UHMWPE体系,UHMWPE含量为4wt%时,加工参数的改变对体系动态流变学行为没有明显影响。

但碳酸钙(CaCO3)的加入却引起体系动态流变学行为显著的改变,表现为:频率扫描过程储能模量和损耗模量随着剪切速率
的增大在低频区逐渐提高,体系动态流变学行从liquid-like向
solid-like行为转变,等温结晶过程加快,应力松弛时间缩短。

这类特殊的流变行为与UHMWPE颗粒在加工过程中形态的转变有密切关系。

【英文摘要】Polymer dynamics rheology is an effective method to study the relation of the evolution of its morphology and the rheological behavior, especially for multi-phase polymer system.In recent years, many study focused on the dynamic rheological properties of polyolefins (mainly polyethylene) blends. Mostly concentrated in the relation of thermal rheological behavior of blends and the phase behavior. It was lack necessary research to the relation of the evolution of its morphology and the rheological behavior in the processing.In this article, high-density
polyethylene/ultrahigh molecular weight polyethylene (HDPE/UHMWPE), high density polyethylene/ultrahigh molecular weight polyethylene/calcium carbonate (HDPE/UHMWPE/CaCO3) blends was intended to take as a model. The influence of the
processing parameters, including the processing temperature, screw shear rate, filler content, on the dynamic rheological behavior of the blends has been investigated. On this basis, the evolution of morphological structure on the system has been extrapolated.Study showed that for HDPE/UHMWPE blends
(90/10wt%), the change of processing temperature or screw shear rate maked the dynamic rheological behavior of this system obviously transform.The results showed that the dispersion of UHMWPE improved with the increase of screw speed. The composite melts behaved various dynamic rheological behaviors. The storage moduli (G’), loss moduli (G”), zero shear viscosity (η0) of the HDPE/UHMWPE composite melts increased obviously at low frequency region, while the transition point of the viscoelasticity moved to low frequence region. Due to the dispersion improvement of UHMWPE, the initial crystallization temperature of HDPE/UHMWPE composites shifted to high temperature and the isothermal crystallization process was accelerated. The morphology of nascent UHMWPE powder was examined by scanning electronic microscopy (SEM). A morphology model has been proposed for these composites. The secondary UHMWPE particles could be gradually destroyed by the screw shear and resulted in better degrees of UHMWPE dispersion in
these composites.However for the HDPE/UHMWPE (96/4wt%) blends, the changes of processing parameters had no significant effective on dynamic rheological properties of this blends. The addition of calcium carbonate has caused significant changes of dynamic rheological behavior. The results showed that CaCO3 can not change the rheological behavior of HDPE. While HDPE/UHMWPE/CaCO3 composites had various rheological behavior with different processing. At low frequency region the dependence of storage modulus on frequency for the blends tended to be weakened with the increase of the screw speed of torque rheometer. And the storage moduli (G’), loss moduli (G”), zero shear viscosity (η0) of the blend melts increased obviously, while the tangent (δ) decreases. This corresponded to changes from more liquid-like behaviors for
HDPE/UHMWPE/CaCO3 composites to solid-like behaviors. These phenomena reflected macromolecular chains entanglement enhancement. The change of the structure of the blend melt further identified that the macromolecular chains interacted much more . The interaction affected the mobility of macromolecular chains. So the the stress relaxation time increased and the isothermal crystallization process was accelerated. The viscoelastic transition of melt was related
to the interaction of UHMWPE and CaCO3 rigid particle. With the content increasing of Calcium carbonate, the dynamic rheological properties significant changed, which may be related to the forming of the network between calcium carbonate filler and ultra-high molecular weight polyethylene.
【关键词】动态流变学高密度聚乙烯超高分子量聚乙烯
【英文关键词】dynamic rheology HDPE UHMWPE
【目录】高密度聚乙烯/超高分子量聚乙烯共混体系动态流变学行为研究摘要4-5Abstract5-6第1章绪论9-22 1.1 流变学概述9-10 1.2 聚合物熔体流动模式及其数学处理方法
10-13 1.2.1 简单剪切流动10-11 1.2.2 小振幅振动剪切流动11-12 1.2.3 瞬态剪切流动12 1.2.4 拉伸流动12-13 1.3 动态流变学测试方法13-15 1.3.1 测量工具13-14 1.3.2 测试模式14-15 1.4 聚合物多相体系线性黏弹性15-17 1.4.1 线性黏弹性理论15-16 1.4.2 乳液模型16-17 1.5 聚乙烯多相体系动态流变学研究进展17-21 1.6 本论文研究主要内容21-22第2章 HDPE/UHMWPE 体系动态流变学行为研究22-41 2.1 引言
22 2.2 实验部分22-23 2.2.1 实验原料及设备22 2.2.2
试样制备22-23 2.2.3 性能测试23 2.3 结果与讨论
23-39 2.3.1 应变扫描23-25 2.3.2 频率扫描25-33 2.3.3 应力松弛33-34 2.3.4 时间扫描34-38 2.3.5 形态结构演化分
析38-39 2.4 本章小结39-41第3章 HDPE/UHMWPE/CaC0_3体
系动态流变学行为研究41-53 3.1 前言41 3.2 实验部分
41-42 3.2.1 实验原料及设备41 3.2.2 试样制备
41-42 3.2.3 性能测试42 3.3 结果与讨论42-51 3.3.1 频
率扫描42-47 3.3.2 应力松弛47-48 3.3.3 时间扫描
48-50 3.3.4 形态结构演化分析50-51 3.4 本章小结
51-53第4章全文总结53-54参考文献54-58致谢
58-59攻读硕士期间发表的论文59
【采买全文】1.3.9.9.38.8.4.8 1.3.8.1.13.7.2.1 同时提供论文写作一对一辅导和论文发表服务.保过包发.
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