Biodegradation of Isotactic Polypropylene (iPP)/Poly(lactic acid) (PLA) and iPP/PLA/Nano Calcium Carbonates Using Phanerochaete chrysosporium

Phanerochaete chrysosporium species was used to study the degradation of polymeric composites of (a) isotactic polypropylene (iPP) and (PLA) (iPP/PLA), and (b) iPP/PLA filled with calcium carbonate nanoparticles (nCaCO(3)). PLA was synthesized using l-lactic acid under the controlled ultrasound cavitation technique, dried and used for composite preparation. Meanwhile, the synthesis and subsequent surface modification of nCaCO(3) was done using the ultrasound cavitation technique. Owing to ultrasound cavitation, a reaction mixture is dispersed uniformly but at the same time strong electrostatic force of attraction is developed over the surface of nCaCO(3) particles, which forms the agglomeration of particles. The deagglomeration as well as charge nullification was achieved using surface modification of CaCO3 nanoparticles with triethoxy vinyl silane (TEVS) under controlled stirring. The sheets of iPP/PLA and iPP/PLA/nCaCO(3) were prepared at normal condition and subjected to a degradation study in minimal medium using P. chrysosporium microorganism up to 28 days. The growth of microorganism and fractures inside the polymer matrix before and after degradation was observed using a scanning electron microscope. Changes in extracellular protein content, biomass production, and percent degradation with respect to time of incubated samples have also been studied. It was found that the iPP/PLA/nCaCO(3) (5 phr) and iPP/PLA (at 30% PLA) composites show an increment in degradation. The presence of nCaCO(3) leads to faster degradation of iPP/PLA/nCaCO(3) nanocomposites, which decreases the mechanical property by 30% of PLA and 5 wt% of nCaCO(3) content.