Effect of long‐chain branching molar fraction on scratch behavior of polypropylene

Abstract

Polymers containing a certain amount of long‐chain‐branching (LCB) structure are expected to possess improved mechanical properties over those of the linear structure counterpart. However, fundamental knowledge on the structure–property relationship in LCB containing polypropylene (PP) is still illusive. In the present study, a set of model PP systems containing an increasing molar fraction of LCB (5–19 mol%) were prepared by reactive extrusion to determine how LCB content may influence the scratch behavior of PP. It is shown that with only 5 mol% of LCB content in PP can improve resistance against scratch‐induced fish‐scale formation by over 25%. The improvement of scratch resistance is attributed to the increases in entanglement density in LCB‐containing PPs, which is evidenced by their creep‐recovery behavior. The present study demonstrates that the incorporation of LCB in PP leads to higher viscoelastic recovery and increased tensile strength, which account for the observed improvement in scratch performance. The usefulness of LCB in polymers for improving scratch performance is discussed.

Self-healing polymers for surface scratch regeneration

“…In this study, the compressive yield stress was found to increase as the molecular weight between the crosslinks ( M c ) decreased, which greatly improved the scratch resistance of polymers by delaying the onset of crack formation. Similar intermolecular interactions were also studied 97 by observing the structural effect of long chain branching of polypropylene (PP) polymer. The branching induced superior mechanical properties, however, there was a minor improvement in the scratch resistance of PP.…”