Gloger, Dietrich published the artcileLong-Chain Branched Polypropylene: Effects of Chain Architecture, Melt Structure, Shear Modification, and Solution Treatment on Melt Relaxation Dynamics, Application In Synthesis of 31570-04-4, the publication is Macromolecules (Washington, DC, United States) (2022), 55(7), 2588-2608, database is CAplus.
Polymers with large mol. structures like long-chain branched polypropylene, LCB PP, are prone to a disentanglement phenomenon known as shear-modification. Extrusion decreases melt viscosity and elasticity, restored by prolonged melt heating (annealing) or a solution treatment. Here, for LCB PPs and blends with linear isotactic polypropylene, L PP, we study chain architecture, branch content, linear viscoelasticity, the changes caused by shear-modification and recovery thereof in solution Our LCB PPs are crosslinking products of a linear precursor. Architecture and molar mass distribution of the LCB PPs followed random branching according to percolation theory, with deviations explained by a non-negligible fraction of linear chains. A solvent-insoluble fraction, gel, was indicative of large percolation clusters. Shear modification of our LCB PPs was not fully reversible, due to breakage of chains in the high molar mass tail or of even larger structures (percolation clusters) not detected by gel permeation chromatog. We also propose shear modification of LCB PP deforms (1) chain conformations, (2) perturbs the long-range melt order created by the crosslinking reaction and (3) affects mixing quality between linear and branched chains. In solution, we propose recovery mechanisms are chain swelling into spherical conformations and a redistribution of linear and branched chains. Our work shows that the understanding shear modification of branched polymers requires knowledge of content and architecture of all chain species, their mol. mixing quality and consequently their mutually dependent relaxation mechanisms.
Macromolecules (Washington, DC, United States) published new progress about 31570-04-4. 31570-04-4 belongs to esters-buliding-blocks, auxiliary class Mono-phosphine Ligands, name is Tris(2,4-di-tert-butylphenyl) phosphite, and the molecular formula is C42H63O3P, Application In Synthesis of 31570-04-4.
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