Effects of hot water treatment of raw bark, coupling agent, and lubricants on properties of bark/HDPE composites

Hot water treated and untreated black spruce bark (BSB) and trembling aspen bark (TAB) fibers were combined with high density polyethylene (HDPE) to produce bark thermoplastic composites by extrusion. Bark fibers of three size categories (fine, medium, and coarse) were used at contents of 50% and 60% based on oven dry weight. The effects of hot water treatment of raw bark and the addition of coupling agent (MAPE) and lubricants (OP-100, talc) on the flexural and tensile properties of bark/HDPE composites were investigated. Results showed a significant impact of hot water treatment on tensile properties of composites made with BSB and on tensile and flexural strength of composites made with TAB. The addition of coupling agent and lubricants significantly improved the flexural and tensile strength properties of bark/HDPE composites but reduced toughness and strain.

► Bark from 2 species, was used to produce bark/HDPE composites.
► Hot water extraction of bark decreased composite properties.
► Bark/HDPE composites made from black spruce composites showed better mechanical properties than those made from trembling aspen.
► Lubricants and coupling agents improved the composite properties.