Biodegradable composites based on lignocellulosic fibers—An overview

The rising concern towards environmental issues and, on the other hand, the need for more versatile polymer-based materials has led to increasing interest about polymer composites filled with natural-organic fillers, i.e. fillers coming from renewable sources and biodegradable. The composites, usually referred to as “green”, can find several industrial applications. On the other hand, some problems exist, such as worse processability and reduction of the ductility. The use of adhesion promoters, additives or chemical modification of the filler can help in overcoming many of these limitations. These composites can be further environment-friendly when the polymer matrix is biodegradable and comes from renewable sources as well. This short review briefly illustrates the main paths and results of research (both academic and industrial) on this topical subject, providing a quick overview (with no pretence of exhaustiveness over such a vast topic), as well as appropriate references for further in-depth studies.

Green composites: A brief review

Mechanical properties of sisal/oil palm hybrid fiber reinforced natural rubber composites

This paper investigated the stability, mechanical properties, and the microstructure of wood–plastic composites, which were made using either recycled or virgin high-density polyethylene (HDPE) with wood flour ( Pinus radiata ) as filler. The post-consumer HDPE was collected from plastics recycling plant and sawdust was obtained from a local sawmill. Composite panels were made from recycled HDPE through hot-press moulding exhibited excellent dimensional stability as compared to that made from virgin HDPE. The tensile and flexural properties of the composites based on recycled HDPE were equivalent to those based on virgin HDPE. Adding maleated polypropylene (MAPP) by 3–5 wt% in the composite formulation significantly improved both the stability and mechanical properties. Microstructure analysis of the fractured surfaces of MAPP modified composites confirmed improved interfacial bonding. Dimensional stability and strength properties of the composites can be improved by increasing the polymer content or by addition of coupling agent. This project has shown that the composites treated with coupling agents will be desirable as building materials due to their improved stability and strength properties.

Dimensional stability and mechanical behaviour of wood–plastic composites based on recycled and virgin high-density polyethylene (HDPE)

Problems concerning the processing of thermoplastics reinforced with wood fillers are discussed. The high level of moisture absorption by the filler, its poor wettability, as well as the insufficient adhesion between untreated filler and the polymer matrix are reasons for the low tensile strength and high moisture sorption of composites. These shortcomings of composites can be prevented by the modification of the interface. The fiber-matrix compatibility and the composites properties can be improved by using some physical (e.g., steam explosion, corona, cold plasma) and chemical (cross-linking and acetylation of cellulose, grafting, use of coupling agents) methods. Modified wood-polymer interaction mechanisms are complex and specific for each definite system and processing conditions. Cellulose cross-linking and acetylation reduce hygroscopicity and swelling of wood and wood composites. Grafting of styrene to wood is effective for wood-polystyrene systems. The best coupling agent for wood-thermop...

Thermoplastics Reinforced with Wood Fillers: A Literature Review

The development of composites consisting of wood fibers and recycled plastics offers not only an opportunity to utilize an abundant natural resource but also a means to alleviate the serious plastics disposal problem. In this work, aspen fibers are incorporated into recycled high density polyethylene with a co-rotating inter-meshing twin-screw extruder to study processing-property relationships. Tensile, impact, and flexural strengths are measured as functions of fiber concentration. The effects of fiber pretreatment, screw configuration, and compounding temperature on the properties of composites are discussed.

Composites from compounding wood fibers with recycled high density polyethylene

Flow properties of two classes of egg powder were studied. Whole egg with corn syrup and salt (CEP) exhibited better flow properties than whole egg powder (WEP). Free-flowing characteristics of both powders decreased with increased temperature. Moisture content was found to have significant affect on the flowability of CEP, but not WEP, at level as low as in the (B.E.T.) monolayer region [Brunauer et al. (1938), JACS 60: 309]. Lipid, on the other hand, was shown to be the dominant factor in preventing easy flow of WEP. This was related to the presence of surface lipid that contributed to the cohesiveness between particles.

Effect of Composition on the Flow Properties of Egg Powders

Compounding wood fibers and recycled high density polyethylene using a twin-screw extruder

Frozen food packaging

Plastics in the waste stream have increased steadily, from about one-half million tons in 1960 to 9.6 million tons in 1984 in the United States; if this trend continues, the amount of plastic wastes in the year 2000 will be 15.5 million tons. The problems associated with the growing proportion of plastic packaging materials in community domestic refuse have generated public concerns. Furthermore, an increasing number of laws are being proposed to address the solid waste — many targeted at plastic packaging.



This was the background for the conference‚Recycled Plastics: Developments and Applications’which provided a broad perspective of the field. Emphasis was placed on current and potential uses for recycled plastics.



The conference was held on September 15, 1987 at the School of Packaging, Michigan State University. More than a score of speakers examined the latest developments and discussed recycling methodologies, marketing approaches, social and environmental implications. This brief report attempts to summarize the main points made.

Christopher C. Lai

Papers

Composites from compounding wood fibers with recycled high density polyethylene

Effect of Composition on the Flow Properties of Egg Powders

Compounding wood fibers and recycled high density polyethylene using a twin-screw extruder

Frozen food packaging

Developments and applications of recycled plastics