The research – Recycled polymer composites

The research has great relevance given that disposal of plastic waste by way of landfills induces environmental and space problems while incineration leads to air pollution and aggravation of global warming

By Bonnie James/Deputy News Editor/Gulf Times

In a development that could substantially improve the quality of recycled plastics, Qatar University’s Centre for Advanced Materials (CAM) has made progress in research to produce recycled polymer composites which are cheaper than pure synthetic fibre composites and have superior properties.

“Date palm wood flour and date palm leaf fibre, abundantly available as agro-waste material in Qatar, were added to produce recycled polymer composites which could be utilised for a wide range of applications in different fields,” post doctoral researcher Dr Noorunnisa Khanam Patan told Gulf Times.

Glass fibre and mica were also used as reinforcements with recycled polymers in the research programme being conducted under the supervision of associate professor and CAM director Dr Mariam al-Ali al-Ma’adeed.

“The objective is to use recycled polymers as a matrix to reduce environmental pollution, considering that Qatar produces a large quantity of polyethylene plastics and substantial amounts of plastic wastes are available as municipal solid wastes,” Dr Patan explained.

The research has great relevance given that disposal of plastic waste by way of landfills induces environmental and space problems while incineration leads to air pollution and aggravation of global warming.

“Over the past few decades, polymers, due to the ease of processing, better productivity and cost reduction have replaced many of the conventional materials such as metals, wood and ceramics in various applications,” she pointed out.

Polymer is a macromolecule, made up of many small molecules which have combined to form a single long or large molecule. The individual small molecules from which a polymer is formed are known as monomers and the process by which they are linked to form a big polymer molecule is called polymerisation.

There are natural and synthetic polymers. Natural polymers are those isolated from materials such as cotton, wool, leather, silk, and cellulose rayon. Synthetic polymers are synthesised from low molecular weight compounds and examples include polyethylene, polyvinyl chloride, and nylon.

Depending upon its ultimate form and use, a polymer can be classified as thermoplastic, thermosetting, plastic, elastomer, fibre and liquid resin. “The combination of conventional polymers with fibre or fillers is an important alternative to obtain new polymeric materials with designed properties to suit the high strength/high modulus requirements, and these are called polymer composites,” Dr Patan said.

A composite is a mechanically separable combination of two or more component materials, different at molecular level, but mixed purposefully to obtain a new material with optimal properties.

Polymer composites are widely used in varied fields, including automotive, sports goods, construction, aerospace, marine, electrical, biomedical applications, and chemical equipment.

There are two types of constituent material: matrix and reinforcement. Thermoplastic, thermosetting matrices are used as the matrix in polymer composites with natural and synthetic fibres as reinforcing materials.

The most common include polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene, and polyether ether ketone.
The most common natural fibres are sisal, jute, coir, and date palm fibre and synthetic fibres are glass, Kevlar and carbon.

“The objective of the current research at CAM is to produce recycled polymer composites that incorporate naturally available, environment-friendly plant-based fibre as an alternative reinforcement material, imparting high specific strength and stiffness,” Dr Patan said.

Though recycling helps conserve materials, it is known to change the mechanical, physical and chemical properties of the recycled plastics to some extent, thereby lowering their economic value. This could be overcome by adding suitable plant-based fibres.

“Deforestation and growing environmental concerns were the main driving forces for the launch of wood-plastic composites as a natural wood substitute over two decades ago,” the researcher recalled.

The research at CAM comprised four parts. In the first stage, glass fibre was added to date palm wood flour to improve its mechanical properties. In the second stage, recycled polymer composites were prepared by using date palm leaf fibre and in the third stage recycled polymer and mica were used. The fourth stage involved a study of the mechanical, thermal, and morphological properties of the composites.