Abstract
Long-chain branching (LCB) with peroxydicarbonates (PODIC) is known as a suitable post-reactor process to introduce strain-hardening behaviour and an increase of melt strength to a linear polypropylene (PP). This opens up new possibilities for processing and therefore application. Especially in the case of adding value to PP post-consumer waste, LCB is a promising approach. LCB takes place by a combination of chain scission and recombination after radical activation of the PP macromolecule. However, chemical modification of post-consumer waste is challenging because of the inhomogeneous composition and the manifold number of PP grades. The influence of the molar mass of the linear PP precursor on this reaction was studied with different PP grades ranging from extrusion grade to injection moulding grade. To exclude side effects, all PP grades had similar polydispersity indices. A PP with higher molar mass undergoes significant chain scission during the LCB process compared to a PP with low molar mass for injection moulding. Therefore, the two grades differ significantly in their branching number, which influences their behaviour in elongational flow.
Highlights
Isotactic polypropylene (PP) is one of the most popular consumer plastics in the global polymer market
The oxidation induction time (OIT) of the polypropylene grades was determined to compare the oxidative behaviour of the materials
The crossover modulus of all samples decreases with Long-chain branching (LCB) and the crossover frequency shifts towards smaller values
Summary
Isotactic polypropylene (PP) is one of the most popular consumer plastics in the global polymer market. The impurities in PP post-consumer waste can be categorised into four groups: high molecular impurities like other plastics; low molecular impurities like different. Reactive monomers and/or peroxides are are used used to to generate generate interfacial interfacial crosslinks to improve the mechanical and/or peroxides mechanical properties of the polyolefin blends blends [15,16,17,18,19,20,21,22] The kinetics of such grafting reactions is of great interest and so they have been studied intensively. InIn case ofofPP, to the increased melt strength and special product applications, such as foaming and film blowing [39]. The increased melt strength and special product applications, such as foaming and film blowing.
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