Polystyrene cellulose fiber composites: effect of the processing conditions on mechanical and dynamic mechanical properties

Matheus Poletto

doi:10.1590/s1517-707620160003.0053

Abstract

The usage of natural fibers on the composites development has grown rapidly in the recent years due to the fibers plentiful availability, renewable source, low density and biodegradability. However, there are some drawbacks, for instance, the fiber dispersion on a polyolefin matrix. In this work, the influence of processing speed on the mechanical and dynamic mechanical properties of polystyrene (PS) filled with cellulose fiber composites was investigated. The composites were processed on a twin-screw co-rotating extruder, using screw speeds of 200 rpm, 400 rpm and 600 rpm. The dynamic mechanical properties and the mechanical properties were investigated as a function of fiber content. The composites processed on a screw speed of 400 rpm had presented an increase on flexural and impact strength, compared to the composites processed at 200 rpm. The flexural and storage modulus had increased when increasing the fiber content, as well as increasing the processing speed. The greater fiber dispersion obtained at a screw speed of 400 rpm hinders the agglomeration arrangement and distributes the fibers more equally on the matrix. The increase on processing speed probably generates a fiber size reduction, increasing the fiber superficial area and generating a greater contact with the matrix as well. Therefore, the efforts transference of matrix to fibers is improved, originating an increase on the evaluated properties.

Highlights

IntroductionNatural fibers (e.g. cellulose, sisal, wood fibers, pine, bamboo, jute, palm, henequen and others) have gained rapid growth in the recent years due to a number of advantages they offer over conventional reinforcing materials (e.g. glass and carbon fibers), such as, abundance, renewability, low density, high specific strength and stiffness, almost no health hazards, and relatively low cost. [1-3]Many studies have been done on thermoplastics-based and natural fiber composites, which have successfully proven their applicability to various fields of technical application [2-4]
Natural fibers have gained rapid growth in the recent years due to a number of advantages they offer over conventional reinforcing materials, such as, abundance, renewability, low density, high specific strength and stiffness, almost no health hazards, and relatively low cost. [1-3]Many studies have been done on thermoplastics-based and natural fiber composites, which have successfully proven their applicability to various fields of technical application [2-4]
This study aims to evaluate the effect of screw speed used during the extrusion process on the mechanical and dynamic mechanical properties of PS/cellulose fiber composites

Summary

Introduction

Natural fibers (e.g. cellulose, sisal, wood fibers, pine, bamboo, jute, palm, henequen and others) have gained rapid growth in the recent years due to a number of advantages they offer over conventional reinforcing materials (e.g. glass and carbon fibers), such as, abundance, renewability, low density, high specific strength and stiffness, almost no health hazards, and relatively low cost. [1-3]Many studies have been done on thermoplastics-based and natural fiber composites, which have successfully proven their applicability to various fields of technical application [2-4]. Natural fibers (e.g. cellulose, sisal, wood fibers, pine, bamboo, jute, palm, henequen and others) have gained rapid growth in the recent years due to a number of advantages they offer over conventional reinforcing materials (e.g. glass and carbon fibers), such as, abundance, renewability, low density, high specific strength and stiffness, almost no health hazards, and relatively low cost. One difficulty that have prevented a more extended utilization of natural fibers, and it is a challenge for cellulose fiber reinforced thermoplastic composites, is a lack of good interfacial bonding between the hydrophilic nature of fibers to a hydrophobic matrix [5-7]. Zhang et al investigated the effect of screw configuration, screw speed and different material compositions in order to achieve a uniformity improvement of wood/HDPE composites [8]. The results showed that the screw speed should be controlled to achieve efficient mixing without thermal degradation [8]

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