Blends of poly (lactic acid) and biodegradation in soil

Abstract

Biodegradable polymers and blends have been intensively studied by the scientific community nowadays due to the increasing quantity of non-biodegradable synthetic plastic garbage. Poly(L-lactic acid) (PLLA) is a biodegradable polymer produced from renewable resources that is extensively used in biomedical and pharmaceutical applications, and an example would be for controlled drug delivery purposes. Hydrolysis of PLLA in the human body occurs due to the ester groups in the chain. Besides biodegradability, PLLA is an important polymer because to technological and mechanical properties and biocompatibility. Physical and mechanical properties of polymers are supposed to be modified when they are physically mixed with others (blending proccess) and, in case of thin films, there is influence of morfology and thickness, yet. Developing blends suitable to the microbian attack is highly important to reduce the great quantity of disposable plastic residues in environment. PLLA blended with biodegradable polymers have been used as medical material, due to its biodegradability and biocompatibility. Poly(vinyl alcohol) (PVA), poly(ε-caprolactone) (PCL), poly(hydroxybutyrate) (PHB), poly(ethylene oxide) (PEO), poly(D-lactic acid) are some of that polymers. On the other hand, in some cases, biodegradability is unsuitable, like in eletronic products and cars accessories, where good mechanical properties are required. In short, PLLA must be stable while in use and readily degradable after thrown away. Therefore, its biodegradability control is an extremely important subject. Poly(vinyl chloride) (PVC) is an amorphous non-biodegradable synthetic polymer that has been blended to a large range of polymers in order to improve mechanical properties and increase its applications in trade and industry. Despite of its instability in presence of light, its residues persists in the environment.PCL is a biodegradable semi-crystalline synthetic polymer widely used in medical purposes: tissue fixation, wound closure; in agriculture: mulch films and in packaging. PCL is compatible to be blended to several polymers, including PVC and PLLA. The purpose of this study is to investigate the PLLA/PVC and PLLA/PCL blends biodegradtion in soil columns, using infra-red spectra (FTIR), UV-VIS and contact angle.