Matrix morphology and the particle dispersion in HDPE nanocomposites with enhanced wear resistance

Jani Pelto,Kimmo Kaunisto,Helena Ronkainen,Mikko Karttunen,Jarkko Metsäjoki,Tuukka Verho,Jani Seitsonen

doi:10.1016/j.polymertesting.2019.105897

Jani Pelto, Kimmo Kaunisto + Show 5 more

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https://doi.org/10.1016/j.polymertesting.2019.105897

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Abstract

Abstract High density polyethylene nanocomposites were prepared by melt mixing of varying type of nanopowders in the presence of vinyltrimethoxysilane (VTMS) coupling agent. Three spherical/irregular-shaped nanopowders, fumed Al2O3, γ-Al2O3, cubic titanium nitride (TiN) (1.5 vol-%), and high aspect ratio graphene oxide platelets (GO) (0.5 vol-%) were investigated in a high molecular weight HDPE matrix. Significant differences in the dispersion quality between the nanopowders were found by TEM and AFM. Degree of crystallinity of the nanocomposites (DSC/XRD) was consistently lower than in the neat HDPE polymer. The particularly well dispersed fumed Al2O3, γ-Al2O3 and GO nanopowders induced significant modification on the micromechanical properties of the HDPE. For the first time, great enhancement in the sliding wear performance, and an improvement in the abrasive wear performance was found in the high molecular weight HDPE nanocomposites. DSC analyses showed elevations in the glass transition temperatures and the peak melting temperatures of the nanocomposites. XRD peak splitting in the HDPE + GO and the HDPE + γ-Al2O3 nanocomposites suggest the emergence of a concurrent orthorhombic HDPE phase. Formation of new phases was also supported by DSC analyses showing broad and multimodal melting peaks. Scherrer analyses of XRD data showed slightly increased HDPE crystalline thicknesses in the range of 15–20 nm in the nanocomposites, which was in line with the TEM and AFM observations. The great elevation in the melting temperatures of the HDPE nanocomposites with fumed Al2O3 and γ-Al2O3 could not be attributed to the polymer lamellar thickness, but rather to the altered properties of the solid amorphous phase stemming for the nanopowder additives.

Highlights

High density polyethylene (HDPE) is a commodity polymer equipped with many good engineering properties
The great elevation in the melting temperatures of the HDPE nanocomposites with fumed Al2O3 and γ-Al2O3 could not be attributed to the polymer lamellar thickness, but rather to the altered properties of the solid amorphous phase stemming for the nanopowder additives
We studied the dispersion and morphology of various melt compounded HDPE nanocomposites

Summary

Introduction

High density polyethylene (HDPE) is a commodity polymer equipped with many good engineering properties. Owing to the chemical inertness, self-lubrication, high mechanical ductility, and good wear performance of HDPE, it is widely used for plastic bottles, water piping, tanks and containers, for example. Under load conditions involving low surface pressures and dry or lubricated sliding contacts against metals, HDPE competes with the commonly used performance material ultrahigh molecular weight PE (UHMWPE). Retention of mechanical properties and wear resistance at elevated temperatures are generally manifested in HDPE. To boost these properties, the intrinsic performance of neat HDPE polymer can be further improved by introduction of additives, inorganic fillers, and by applying chemical crosslinking. The high loading of micron sized fillers (10–40 vol-%) required to achieve desired outcomes typically compromise the good intrinsic properties of HDPE

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