Grafting of polystyrene branches to polyethylene and polypropylene

Abstract

Polyethylene (PE) and polypropylene (PP) were reacted with benzoyl peroxide (BPO) and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) to prepare PE-TEMPO and PP-TEMPO macroinitiators, respectively. Molecular weight of PP decreased, whereas that of PE increased during the reaction with the BPO/TEMPO system. Polystyrene (PS) branches were grafted to PE and PP backbone chains as a result of bulk polymerization of styrene with the PE-TEMPO and PP-TEMPO macroinitiators. A significant amount of PS homopolymer was produced as a byproduct. Weight of the resulting PE-g-PS and PP-g-PS increased with the polymerization time up to 20 h and then leveled off. Melting point of PE and PP domains in PE-g-PS and PP-g-PS, respectively, lowered as the content of PS in the copolymers increased. However, glass transition of the copolymers was almost identical with that of PS homopolymer, indicating that the constituents in the copolymers were all phase-separated from each other. In scanning electron microscopy of the incompatible PE/PS, PP/PS, and PE/ PP/PS compounded with PE-g-PS and PP-g-PS, any clear indication of enhanced adhesion between the phases was not observed. However, phase domains in the blends were, nevertheless, reduced significantly to raise mechanical properties such as maximum stress and elongation at break by 20 -75%.

Post‐polymerization modification by nitroxide radical coupling

“…Both the polymers were functionalized by NRC reaction using TEMPO and benzoyl peroxide thus obtaining the macroinitiators PE‐ g ‐TEMPO and PP‐ g ‐TEMPO, respectively. These last were successively treated at 120 °C with styrene to graft PS chains, but a significant amount of free PS due to thermal self‐initiation polymerization of styrene was also attained . In addition, the increase of the molecular weight with polymerization time was not linear confirming that control of the growing PS chains was not complete.…”

Preparation and applicability of functionalized polyethylene with an ethylene/1,7‐octadiene copolymer

“…This results in modified polymers showing enhanced environmental stress cracking resistance, thermooxidative stability, good bonding to metals, and ion‐exchange capacity. The literature suggests that there is great interest in finding suitable ways to combine these polymers into useful materials 4–11…”

Polymer Hybrids Based on Polyolefins – Syntheses, Structures, and Properties

“…PE-g-PS and PP-g-PS were synthesized from PE-TEMPO and PP-TEMPO, respectively, which were prepared from PE and PP reacting with benzoyl peroxide and TEMPO [102].…”