The effect of microstructure, filler load and surface adhesion of marine bio-fillers, in the performance of Hybrid Wood-Polypropylene Particulate Bio-composite

In the past few decades, the world has experienced a rapid process of urbanization as a result of fast population growth, where the supply system has predominantly depended on energy-intensive industrialization. The process of rapid urbanization has increased pressure on existing natural resources and leading to a complex socio-environmental scenario with unprecedented attributes. These combined effects of speed rate, energy consumption, greenhouse emissions, and waste generation have led to long-term consequences causing great concern. These include fragmentation of the ecosystem, land degradation, desertification, and biodiversity loss.

In this context, the theory of industrial ecology has been developed to address these important social, environmental, economic, and technological challenges through an Integrated Waste Management Strategy, which encompasses transferring waste into resources or inputs to new processes. The fundamental relevance of this concept is centrally placed in the optimized use of raw materials and minimizing extractive pressure on virgin materials, by lengthening their service life via a longer value chain. This cascading use of capital enhances an efficient response to environmental challenges, while transitioning towards more resilient urban settlements.

Claudia Echeverria, Farshid Pahlevani, Vaibhav Gaikwad, and Veena Sahajwalla from the Centre for Sustainable Materials, Research and Technology at the University of New South Wales in Australia (SMaRT@UNSW), proposed an Industrial technology integrated solution between the waste management sector and the wood-based panel manufacturing industry. Their aim was to advance Wood-Plastic Composite materials by transferring waste into useful resources, for the development of low-carbon and high-value environmentally sensitive end-product for applications in the building industry. Their research work is published in Journal of Cleaner Production.

The research team sourced four waste materials from the Sydney Metropolitan Area. They examined local marine litter such as Bivalve mollusc shells and Kelp Brown Algae as combined reinforcements in the function of secondary bio-fillers, approaching the optimization of the bio-composite performance with natural non-toxic materials. They prepared a series of 20 samples with the filler-matrix 60/40wt%. They also included secondary bio-fillers to the blend in the ratio 10-20wt%. The authors finally manufactured prototype panels through the traditional hot-compression method. The researchers investigated the fracture surface of the bio-composite panels and the filler-matrix interface. They also reported the mechanical behavior and moisture absorbency of the proposed bio-composite as a function of filler load, particles size, and the effect of coupling agent.

The authors observed from the experimental results that the particulate bio-composite panel achieved an overall performance consistent with the International Standard ISO 16893:2006. The marine bio-fillers were responsible for the improved mechanical characteristics of the prototype panels when they were included individually at 10wt%. The inclusion of the Maleic Anhydride Polypropylene coupling agent at 3% also enhanced the filler-matrix adhesion, which consequently improved the mechanical performance to 200%.

Identical values of Modulus of rupture for uncoupled and coupled samples were realized when the particle size was reduced from the 20 mesh to the 40 mesh. This last prototype could be improved by adding a Maleic Anhydride Polypropylene coupling agent to the blend in order to come up with high mechanical performance applications. For this reason, the recovery of Bivalve mollusc shells and macro-algae wastes as secondary bio-filler materials presented a low-cost low carbon environmentally sensitive alternative for the development of Wood-Plastic Particulate Bio-composites for applications in high-moisture environment.