Polylactides: Properties and prospects of an environmentally benign plastic from renewable resources

Pressing environmental and economic concerns dictate the need to develop ne w synthetic macromolecules based on renewable resources. The vast majority of existing materials are based on non-renewable fossil resources that will eventually be extinguished. Manufacturing synthetic polymers and disposal by incineration produces CO2 and contributes to global warming. For these r easons, poly(lactic acid) (PLA) polymers are of increasing commercial inter est because they are derived from a renewable resources, sequester signific ant quantities of carbon dioxide relative to petrochemical based materials, conserve energy, and easily degrade. The mechanical properties of PLA are compared to other commodity plastics and it is shown that PLA closely resem bles polystyrene. The effects of blending linear and branched chain archite ctures are discussed and it is shown that this provides a convenient method for controlling the elasticity and viscosity of the composite material wit hout affecting mechanical or permeation properties. The melt rheology of hi gh L content linear PLAs shows two unique features; they may be drawn to la rge Hencky strains without breaking and they exhibit considerable strain ha rdening. As a result, PLA is easily processed into fiber form. Due to the e xcellent combination of mechanical, rheological, and environmental properti es, the prospects for widespread commercialization of PLA are excellent.