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首页> 外文期刊>Journal of Applied Polymer Science >Molecular, Rheological, and Thermal Study of Long-Chain Branched Polypropylene Obtained by Esterification of Anhydride Grafted Polypropylene
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Molecular, Rheological, and Thermal Study of Long-Chain Branched Polypropylene Obtained by Esterification of Anhydride Grafted Polypropylene

机译：酸酐接枝聚丙烯酯化获得长链支化聚丙烯的分子，流变学和热学研究

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摘要

Long-chain branched polypropylene was prepared using reaction in the molten state in the presence of glycerol and a linear polypropylene functionalized with maleic anhydride (PPg). The concentration of glycerol in the melt was varied in the range from 0.1 to 5 wt % to obtain different levels of branching. FTIR spectroscopy results indicate that the OH groups of glycerol react with the anhydrides on the PPg chains giving place to ester groups. The presence of long-chain branches in the molecular structure of PPg was confirmed using multiple-detection size-exclusion chromatography and rheology. These techniques demonstrate that the level of branching increases with glycerol concentration and that the modification of PPg produces materials with a bimodal distribution of polymer species. Moreover, some of the highly modified materials display gel-like behavior. The materials also display thermo-rheological complexity and enhanced activation energy at low frequencies. The crystallization study shows that both the anhydride groups in PPg and the LCBs have opposite nucleating effects. PPg presents the largest activation energy of crystallization and its value decreases with the concentration of glycerol for a given level of crystallization.
机译：长链支化聚丙烯是在甘油和被马来酸酐（PPg）官能化的线性聚丙烯存在下，在熔融状态下反应制得的。熔体中甘油的浓度在0.1至5重量％的范围内变化以获得不同水平的支化。 FTIR光谱结果表明，甘油的OH基与PPg链上的酸酐反应，形成酯基。使用多次检测尺寸排阻色谱和流变学证实了PPg分子结构中长链分支的存在。这些技术证明，支化程度随甘油浓度的增加而增加，而PPg的改性会产生具有双峰分布的聚合物种类的材料。而且，一些高度改性的材料表现出凝胶状的行为。该材料还显示出热流变复杂性，并在低频下增强了活化能。结晶研究表明，PPg和LCB中的酸酐基团具有相反的成核作用。在给定的结晶水平下，PPg表现出最大的结晶活化能，并且其值随甘油浓度而降低。

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