Study of PBAT films for soil covering (mulching): photodegradation, biodegradation and ecotoxicological impacts

Author(s)

Patrícia Moraes Sinohara Souza

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2019-07-23

Examining board members

Ana Rita Morales; Silvia Pierre Irazusta; Matheus Mantuanelli Roberto; Guilhermino José Macêdo Fechine; Elisabete Maria Saraiva Sanchez

• Advisor: Maria Aparecida Marin Morales; Ana Rita Morales

Abstract

Poly (butylene adipate-co-terephthalate)-PBAT is one of the main polymeric materials proposed for application as a biodegradable mulch film. However, its high susceptibility to photodegradation by exposure to solar radiation compromises its efficiency. In the present study, PBAT films with carbon black absorber additive in combination with different stabilizers to ultraviolet radiation were evaluated for their efficiency for polymer stabilization. In this study, by using experimental designs, it was possible to determine two formulations that were considered the most efficient. One of them was prepared with carbon black and hindered amine light stabilizer (HALS) and the other prepared with carbon black and phenolic stabilizer vitamin E. This selection was based on analysis of mechanical properties, light transmission, molar mass distribution and gel content, before and after accelerated aging. The combination of carbon black and HALS was more efficient to minimize the PBAT chain scission, which can be attributed to the stabilizer mode of action. The selected samples and pure PBAT, after aging, were characterized in relation to disintegration and biodegradation in soil, aiming to evaluate the influence of the different levels of photodegradation suffered by samples on these processes. It was observed that formulations with lower molar mass and lower gel content presented higher disintegration and biodegradation rates. On the other hand, during the respirometric test, the differences in the mineralization degree among the samples became subtler. This behavior suggests an increasing in fraction of aromatic units for the samples polymeric structure. Considering incorporation in soil as the main purpose for destination of biodegradable mulch films, ecotoxicological tests with aqueous extract of soil and PBAT films were conducted after two monitoring periods - before and after photodegradation and biodegradation. Considering the bioassay with the organism Lactuca sativa, it was found absence of phytotoxic effects. The bioassay using the organism Allium cepa revealed absence of cytotoxicity, genotoxicity and mutagenicity. Finally, absence of genotoxic effects was also verified by the bioassay using a human cell culture HepG2/C3A. The results obtained in the present study confirm potential of the studied PBAT formulations with additives for mulch film application (AU)

• FAPESP's process: 16/10777-0 - Study of PBAT mulch films: photodegradation, biodegradation and its cytotoxic, genotoxic and mutagenic effects in Allium cepa and human hepatoma HepG2 cells
• Grantee: Patrícia Moraes Sinohara Souza
• Support Opportunities: Scholarships in Brazil - Doctorate