Banca de DEFESA: Michaella Socorro Bruce Fialho

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : Michaella Socorro Bruce Fialho
DATE: 05/02/2024
TIME: 14:00
LOCAL: Microsoft TEAMS
TITLE:

BIODEGRADABLE HEMICELULOSE/POLY(LACTIC ACID) FILMS: A SUSTAINABLE ALTERNATIVE FOR PACKAGING

KEY WORDS:

Biodegradable films, polylactic acid, hemicellulose, thermal and mechanical properties, packaging.

PAGES: 112
BIG AREA: Engenharias
AREA: Engenharia Mecânica
SUMMARY:

Biodegradable polymers such as hemicellulose and PLA have potential in the packaging industry. Hemicellulose faces challenges of low mechanical strength, while PLA stands out for its ease of processing. Therefore, this study sought to combine these materials by developing polymer blends, aiming for their application in packaging. Hemicellulose was obtained from jute fiber through an alkaline treatment process with KOH. The hemicellulose/PLA blends were produced at concentrations of 5, 15 and 25% (m/m) hemicellulose, 5% glycerol (m/m) and 10 and 20% citric acid (m/m). The latter added in relation to the total blend mass. The films were characterized by FTIR, TGA, DSC, SEM, contact angle, mechanical properties and DMA. Furthermore, the behavior of the films when exposed to water and sanitizing products was evaluated, considering water absorption rates, changes in morphology, thermal and dynamic-mechanical properties after an immersion period of 240 hours. The period of degradation during burial in the soil for 10, 50 and 90 days was evaluated in terms of mass loss rates, morphology and thermal and dynamic-mechanical properties. The morphology of the pure blends was partially homogeneous, while after immersion and burial in the soil it was possible to identify the degradation of hemicellulose in the PLA matrix. The mass loss rate of the blends after 90 days was approximately 35%, while the weight loss of pure PLA was only 7%. FTIR spectra indicated possible esterification reactions between the hydroxyl groups of hemicellulose and the carboxyl groups of citric acid. The thermal stability of the pure blends and when exposed to water, soap and the period of burial in the soil was lower compared to the pure polymers. There was a ~40% decrease in the Tg of the PLA film (67.1 °C) after immersion in water (37.1 °C), diluted soap (44.8 °C) and concentrate (42.4 °C ). This decrease can be attributed to the plasticizing effect of water on PLA. After the immersion and biodegradation period, it was observed that the Tg and Tf of the blends were not affected. However, there was a significant increase in the crystallinity of the blends, which reached a maximum value of approximately 23% after 90 days of burial in the soil. The absorption rate of water and soap in the blends and the contact angle values increased according to the concentration of hemicellulose in the blend, which makes the films hydrophilic in nature. The tensile properties show that the blends exhibit improved tensile strength compared to pure PLA and hemicellulose film. The elongation at break of the blends was substantially lower than that of pure PLA. The hemicellulose content decreased the elasticity and storage modulus of the films. The dynamic-mechanical properties of the films after the period of immersion in water and sanitizing products vary with increasing temperature, being more sensitive in blends with lower citric acid content. And they decreased drastically depending on the time they were buried in the ground. These results indicate significant effects on the final properties of blend films compared to PLA and pure hemicellulose films, which may make them promising for packaging applications.

COMMITTEE MEMBERS:
Externa à Instituição - DANIELLA REGINA MULINARI - UERJ
Externo à Instituição - MICHEL BRIENZO - UNESP
Interno - 2998060 - ALYSSON MARTINS ALMEIDA SILVA
Externa à Instituição - ROSINEIDE MIRANDA LEAO - UNIP
Presidente - 1720225 - SANDRA MARIA DA LUZ