I asked a polymer engineer about PLA biodegradability and he answered that it not 100% degradable. Where as, many suppliers and researchers confirmed that this thermoplastic is 100 % biodegradable.. Kindly clear this doubt....
Biodegradability depends on the chemical composition and structure of the material. Even though the materials are made from renewable resources but using huge amount cross-linkers or comonomers, initiator-fragments, additives etc. may formed highly dense-network structure and not remaining any active hydroxy moieties in the final structure for the effective actions of microorganism (bacteria, fungi....) resulting poor biodegradability.
The main problem for PLA is its Tg (about 58°C). So PLA is rather biocompostable and not biodegradable. The PLA biodegradability strongly depends on the decomposition medium temperature.
PLA will not biodegrade in the natural environment because of the point made by Md.Abdur Rahman. They may require man-made conditions found in industrial composting processes. Hence they may not be 100% degradable.
The terminology of the biodegradability and compostability is kind of confusing the people. For example, biodegradable polymers can't be considered as compostable but compostable polymer can be considered as biodegradable material. So, we need to be clear what terminology we are using.
Regarding the PLA biodegradability, PLA is not 100% biodegradable but it is compostable under controlled compositing conditions such as temperature, pH, humidity, aerobic, nonaerobic, and quality of the compost (ash content, C/N ratio, amount of microorganism, etc). Therefore, PLA can degrade (90%) under compositing conditions within 180 days as per ASTM D6400, ISO 17088 and EN 13432 standards.
Cheers
Raj
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