The Effect of Dialkyl Peroxide Crosslinking on the Properties of LLDPE and UHMWPE.

Pollyana S M Cardoso,Joyce B Azevedo,Josiane D V Barbosa,Benjamin S Lazarus,Fabio C Garcia Filho,Marcelo M Ueki

doi:10.3390/polym13183062

Abstract

Peroxide has been considered a chemical agent that can be used to tune the properties of polymeric materials. This research evaluated the influence of different concentrations of dialkyl peroxides on the mechanical, thermal, and morphological properties of linear low-density polyethylene (LLDPE) and ultra-high molecular weight polyethylene (UHMWPE). The neat polymer, as well as those with the addition of 1% and 2% by mass of dialkyl peroxides, were subjected to compression molding and immersion in water for 1 h, under controlled temperatures of 90 °C. The values of the gel content found in the samples indicated that the addition of peroxide to the LLDPE and to the UHMWPE promoted the formation of a reticulated network. The structure obtained by the crosslinking led to less reorganization of the chains during the crystallization process, resulting in the formation of imperfect crystals and, consequently, in the reduction in melting temperatures, crystallization and enthalpy. The mechanical properties were altered with the presence of the crosslinker. The polymers presented had predominant characteristics of a ductile material, with the occurrence of crazing with an increased peroxide content.

Highlights

Crosslinking of polyethylene is considered one of the main approaches to enhance properties and meet application requirements that are not met by pure polyethylene [1,2].Crosslinking occurs when the polymer adjacent chains become linked covalently
The linear low-density polyethylene (LLDPE) had a deformed particle appearance, which is different from the ultra-high molecular weight polyethylene (UHMWPE)
The UHMWPE morphology consisted of particle aggregates with microcrazes that can be connected by fibrils

Summary

Introduction

Crosslinking occurs when the polymer adjacent chains become linked covalently. This bond can be formed directly through carbon–carbon bonds, or indirectly through a bridgeforming group, which creates crosslinks between the chains [3]. These crosslinks form from the combination of macroradicals generated by the abstraction of hydrogen from the polymer chain, resulting from the action of free radicals originating from the thermochemical decomposition of the product peroxides or from the irradiation of polyethylene [3,4]. Chemical crosslinking is performed by adding an external agent such as azo, silane or peroxide. Several studies have reported the efficiency of peroxide as a crosslinking agent [5,6,7]

Methods

Results

Conclusion