Ever since plastics revolutionised product manufacturing in the late 19th century, these materials have grown to dominate modern consumerism. From the computer keyboard to outdoor furniture, plastics are one of the most versatile materials available to manufacturers. However, they may no longer be one of the cheapest materials available. Oil price hikes are seeing to that, and pushing science to search for new, low-cost, ‘greener’ options to fill the world’s need for versatile plastics.
Some product alternatives to plastic have already travelled the path to market, such as the edible chocolate trays made of corn starch developed by CSIRO and other Food and Packaging Cooperative Research Centre (CRC) partners and now manufactured by biodegradable packaging company Plantic. Overseas, similar biodegradable polymer materials are being used for plastic wrap and supermarket meat trays.
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The automotive industry also is taking advantage of both biodegradable and bioderived (made from organic rather than petrol-based compounds) plastics in the production of car components. These include the use of soybean foam for dashboards and door panels. Another emerging material is composite plastics – petrochemical-based plastics modified to alter the mechanical properties or function of traditional plastics.
These are early uses of the new polymer technologies being developed and the question for many manufacturers is, ‘Where is this technology headed?’
Plastic alternatives add versatility
Composite materials are materials created from more than one component, such as adding inorganic fillers or fibrous reinforcements to traditional plastics to improve strength, reduce cost or add properties, such as making materials resistant to fire. Composite plastics have a variety of applications in the automotive, aerospace and construction industries.
A diverse range of components – from bamboo fibres to talc and even chicken feathers – can be employed to make composite materials. One of the most commonly used biopolymers is polylactic acid (PLA ), which crops up in everything from packaging to biomedical applications such as biodegradable implants. PLA can be blended with starches, such as flour, to improve its toughness, stiffness and thickness. Bamboo is added to PLA to improve strength and flexibility.
Nano-modifed composites, or nanocomposites, have extremely small particles (of less than 100 nanometres) dispersed within the material. As well as improving mechanical performance, they can also change the functionality of materials, for example to create better barrier properties (against water or air), improve fire resistance, block heat, or induce electrical conductivity to shield sensitive electrical components from electromagnetic radiation or to dissipate electrical charge.
Nano-modifed coatings can also protect against heat and light. CSIRO has coated clear plastic bottles with a nanocomposite that protects against a range of UV light or other wavelengths to prevent ‘light strike’ affecting the flavour of the liquids inside.
Scientifically, the key challenge in creating new materials is controlling the chemical interaction between the additives and the plastic components, explains Dr Dong-Yang Wu, research group leader for polymeric materials at CSIRO Materials Science and Engineering. Often, the required parts are incompatible, “so you need to build a little bridge between the molecules”, Dr Wu says.
Dr Wu says the advantages of plastic alternatives are twofold. One is that they maximise the use of renewable r esources rather than petrochemicals, reducing reliance on finite fossil fuel resources. The other benefit is the reduced space taken up in landfill by biodegradable materials.
“At the end of the day, CSIRO is aiming to get biodegradable polymers to perform better than, or similar to, petrol-based products at a competitive cost,” Dr Wu says.
Savings also come from reducing the amount of petrochemical-derived plastics used, explains Dr Stuart Bateman, acting theme leader of CSIRO’s Sustainable Polymeric Materials program. “If you can improve the performance of petrochemical-derived plastics, such as their stiffness and toughness, you can reduce wall thickness, lowering the amount of plastic used in the manufacture of the product,” he says.
“There are also energy savings in terms of faster cycle times in the moulding process and transportation/installation costs.
Dr Wu says that it is important, from a market acceptance perspective, to incorporate more functions in biopolymers by using additives. For instance, aerospace company Boeing and CSIRO have co-developed materials to increase polymers’ fire resistance using nanotech composites.
“Conventional flame retardants can reduce mechanical performance and make the material more expensive,” Dr Bateman says. “We have shown that, on the other hand, nano-additive-based flame retardants can actually improve the mechanical properties of the material without adversely affecting cost.
Composite materials can cut down the use of fossil fuel in the manufacture of plastics, reducing energy consumption. If waste materials are used to create the material, it can potentially encourage recycling of byproducts and save on landfill space.
Biodegradable materials can be sourced from renewable resources and also cut down the amount of time that waste lies in landfill. However, with the world’s food sources stretched by growing population pressures, there has been debate about using food sources to make biodegradable plastic.
“We need to recognise this problem and search for components we can extract from waste products,” Dr Wu says. “To have a sustainable future in biodegradable polymers we need to source materials from waste products rather than food sources.
Scientists also need to examine and control the rate of degradation in biodegradable materials – you don’t want packaging breaking down before it hits the supermarket shelf, or bone glue breaking down before a joint is healed. But you do need to know that materials will degrade (break down into their component molecules) in the appropriate environment, whether that be the body or the rubbish heap.
“In order for companies to adopt biodegradable products, the materials have to meet certain international and Australian standards. CSIRO has the only facility in Australia to do this,” Dr Wu says. “We have just built a state-of-the-art facility to assess biodegradable products against Australian and international standards.
But despite new interest in this research, Dr Wu says commercial uptake is limited within Australia because of its small market base. “CSIRO is trying to take leadership rather than wait for international developments. We need to actively develop capability and technology,” she says.
Dr Bateman also notes that a major issue with uptake is the time and money involved in the conversion of a proven lab technology to a proven commercial technology. However, these sorts of costs may diminish if oil costs continue to increase.
“I think if the petrol price remains the way it is, then there will be a lot more investment in petrol alternatives,” Dr Wu says.
Global oil prices have risen steadily for the past 10 years and last year jumped from about $85 (US$80) to a peak of $118 (US$110) a barrel ( Texas crude oil). If, as some analysts believe, the oil age has begun an irreversible decline, this has a direct effect on petroleum-derived plastics industries.
Dr Stuart Bateman, acting theme leader of sustainable polymeric materials, part of CSIRO Materials Science and Engineering, explains that with prices tied to an increasingly volatile oil economy, the use of plastic alternatives – such as bioderived, biodegradable and composite plastics – is becoming a more cost-effective alternative.
“The market is becoming more receptive to the bioderived and biodegradable plastics as rising oil prices make petroleum-based plastics more expensive,” Dr Bateman says. “Manufacturing industries nowadays are not just looking to materials with a structural purpose, but also for functional properties, such as fire resistance, conductivity or protection from UV degradation.
Biodegradable plastics degrade in the natural environment – in an industrial compost test setting, 95 per cent of the materials decompose within six months.
Biodegradable polymers can be created directly from food crops, such as corn, but also from waste products, such as sugar cane mass and waste dairy products (bioderived plastics). Their use can be low-tech, such as chocolate trays, or high-tech, such as materials used to cement broken bones or promote tissue growth in the human body.
Some of the more immediate applications for biodegradable plastics are in food packaging, where they can be used to replace packaging for dry foods, such as cereals and biscuits, or for biodegradable plates, bowls or cups. The automotive industry is also interested in the use of bioderived and biodegradable materials to create biodegradable or recyclable vehicle components.
A story provided by CSIRO Solve - A CSIRO Review of scientific innovations for Australian industry. This article is under copyright; permission must be sought from CSIRO Solve to reproduce it.
