Photodegradable Films Derived From Polyethylene

This patent describes a process to obtain Low Density Polyethylene (LDPE) film derivatives via the sorption of acrylic and vinyl acetate monomers by the polyethylene matrix, followed by the photo-polymerization of the soaked material. The method provided thin films, in which a vinyl acetate or acrylic polymer is blended in the polyethylene matrix in very small quantities (in concentrations from 1 to 2 %), with no material deposited on the surface. These films showed through transmittance and reflectance (attenuated total reflectance, ATR) infrared spectra and visible-UV spectrophotometry that: 1) the greater photo-degradability [PX means PAA for poly(acrylic acid), PEA for poly(ethyl acrylate), PMA for poly(methyl acrylate), PMNA for poly(methyl metacrylate), and PVA for poly(vinyl acetate)] compared to pure LDPE; 2) the beginning of the photo-degradation being registered in the bulk of the films and not on their surface; and 3) a significative mass loss during the photo-degradation. Regarding the mechanical properties according to ASTM D 882 standard, the LDPE/PAA films gave stress at failure and elongation at break values similar to pure LDPE, while the ones obtained by LDPE/PX (X=EA, MA, MMA and VA) were smaller values (from 25 to 30% smaller). Photo-degraded samples of LDPE/PX (X=EA, MA, MMA and VA) gave stress at failure and elongation at break ca. 50% smaller values than the ones obtained by photo-degraded pure LDPE films. At the half lifetime of pure LDPE under UV radiation, the LDPE/PX film samples (X=AA, EA, MA, MMA and VA) were already brittle. The results show that the introduction of the second component in the studied matrix mace it possible to obtain photo-degradable polymer films derived from pure polyethylene, which can help to solve problems like, for instance, plastic residues in interaction with the environment.WO2006010233 (A1)C08F255/02C08F255/02WO2004BR00137C08F255/02C08F255/02GB876535 (A)US3137674 (A)US3226454 (A)EP0477736 (A1)EP0527688 (A1