TITLE Development of Transparent and Flexible PLA Film with High Function
(Joint Program to Promote Technological Development with the Private Sectors)



Biodegradable plastics have attracted the attention of the world in regard to their minor environmental stress caused when they are discarded in landfills or left in the nature world.

PLA (poly(lactic acid)) is made from carbohydrate that is synthesized through photosynthesis of plants. So, it is smallest in the amount of increasing CO2 in many kinds of biodegradable plastics. Further, environmental CO2 increase during the production process and disposal process of PLA is calculated at 40-80% of that of petrochemical plastics. Further more, in mass production, the cost of PLA is estimated to be similar to that of petrochemical plastics.

Since PLA is regid and brittle, despite its high transparency, PLA is not supposed to be applicable to the general packaging film.In this development, our goal is to develop versatile biodegradable packaging film, maintaining the transparency of PLA and adding the flexibility.

In 2001, we studied techniques to improve heat-registance and physical stability in time-course, and we developed semi-transparent flexible PLA which was blended with high molecular/low molecular plasticizer. In 2002, we focused on improvement of transparency, and we researched these techniques above minutely.

In order to improve transparency, it was effective to blend PLA with lactic acid copolymer. In order to improve heat-registance and physical stability, it was effective to adapt plasticizer which has high solbulity with PLA, to control crystallization, and to react plasticizer on PLA by organic peroxide. Further, we studied techniques to decrease gas permeability.

With these techniques above, we developed the PLA film which has physical propertys equal to LDPE film.

Regarding the gas permeability, we could not establish enough improvement, and we continue the investigation thereof.