Polymers are everywhere. Some see this as a great achievement in industrialization and cheap consumer goods. Take a look at any landfill, however, and it can quickly change your perspective. Although a good portion of polymers can be recycled these
Polymers are everywhere. Some see this as a great achievement in industrialization and cheap consumer goods. Take a look at any landfill, however, and it can quickly change your perspective. Although a good portion of polymers can be recycled these days, there is still an alarming amount of garbage that takes thousands of years to biodegrade. Biodegradable polymers do exist, but they are both expensive and suffer from poor mechanical properties, making their uses few and far between. Researcher in Taiwan have developed a novel solution to both problems, all while eliminating waste of a totally different kind.
Poly(lactic acid), or PLA, is a biodegradable polymer that has received significant attention because of its ability to decompose in the relatively short timeframe of six months to two years. But PLA is significantly more expensive than a traditional polymer derived from oil, and is also very brittle. To overcome these problems, scientists turned to garbage. Agricultural garbage, specifically.
Water Bamboo is a major crop in Taiwan, and the husks represent a large portion of the agricultural waste. By grinding the husks into a powder and adding it to the PLA, the cost of the resulting material is lowered because it uses less of the expensive polymer, and the mechanical properties are modified by the water bamboo husk particles.
It was discovered that the particles disrupted the polymer's crystallinity, which has the effect of lowering its melting point and its glass transition temperature—the point where the polymer is neither solid nor liquid. The resulting husk/PLA material was significantly tougher than pure PLA, and the authors suggested the changes in these two properties were responsible. Flammability tests also showed that the husk particles formed more char on the surface, which inhibits the release of gasses used in the combustion process and insulates the polymer from heat, thus improving its flammability resistance.
Researchers aimed to create industrial packaging that could simply be left to decompose, eliminating landfill waste, and the costs associated with hauling it away and disposing of it. With the cost of PLA still relatively high, there is still work to be done to lower the new material's cost to a point that widespread use is feasible. Still, this is the kind of creativity in utilizing natural resources that will drive us towards the next generation of green materials.
Polymer Science and Engineering, 2008. DOI: 10.1002/pen