Banca de QUALIFICAÇÃO: TIAGO LOPES DE ARAUJO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : TIAGO LOPES DE ARAUJO
DATE: 28/08/2024
LOCAL: Instituto de Pesquisa em Petróleo e Energia (i-LITPEG)
TITLE:

Study of gamma irradiation effects on poly(ε-caprolactone)/poly(butylene adipate-coterephthalate) blends

KEY WORDS:

poly(ε-caprolactone); poly(butylene adipate-co-terephthalate); polymeric blend; gamma irradiation.

PAGES: 92
BIG AREA: Outra
AREA: Multidisciplinar
SUMMARY:

The objective of this work was to investigate the effects of absorbed doses of 12, 35 and 50 kGy, at room temperature and in presence of atmospheric oxygen, on polymeric films of poly(εcaprolactona) (PCL) and poly(butylene adipate-co-terephthalate) (PBAT) blends prepared using solution casting technique, and to study whether PBAT is capable of providing radiolytic stabilization to PCL. The effects of irradiation were evaluated through: viscosimetry of dilute solutions, mid-infrared spectroscopy, ultraviolet-visible spectroscopy, differential scanning calorimetry (DSC), thermogravimetry (TG), mechanical tensile test, water vapor permeability test and opacity test. The viscosimetric tests demonstrated that there was a decrease in the average viscosimetric molar mass of systems with the increase in the absorbed dose, indicating that polymer chains predominantly underwent scission processes. The exception was the system containing 15 % (m/m) of PBAT, which predominantly suffered cross-linking of polymer chains when the dose was 50 kGy. However, calculations of G values and protection factors showed that levels of 10 and 15 % (m/m) of PBAT protected the chains of PCL. Principal component analysis of the pre-processed mid-infrared spectra helped identify differences between the spectra of the PCL and PBAT films and between the spectra of non-irradiated and irradiated samples, regardless of the absorbed dose, showing that the loss of hydrogen from methylene groups initiates the degradation mechanism after irradiation. In turn, ultraviolet-visible spectroscopy also helped to understand the degradation process after irradiation in presence of atmospheric oxygen. It can be observed that there were no significant changes in the thermal parameters investigated, either due to the presence of PBAT in the blends or even due to the effect of gamma irradiation. DSC’s assays also indicated a low degree of crystallinity of the samples (12 %) and melting (119 °C) and crystallization from the melt (60 °C) peak temperatures above those reported in the literature. These results may come from the material’s processing. TG’s assays showed that the thermal degradation of all systems occurred in a single stage without significant variation in starting and ending temperatures of this event, regardless of PBAT content in blends or absorbed dose. Mechanical tensile assays showed that, in general, the increase in absorbed dose promoted a decrease in samples’ tension at maximum strength, while the increase in PBAT content, for the same absorbed dose, contributed to maintaining the values of this property. On the other hand, the dose increase was acquired at 11 times the systems’ elastic modulus. And, finally, both the water vapor permeability and the opacity of the films did not undergo statistically significant variations regardless of the PBAT content in the blends or the absorbed dose.

COMMITTEE MEMBERS:
Presidente - 1356402 - CAROLINA LIPPARELLI MORELLI
Externo ao Programa - 1179034 - ELMO SILVANO DE ARAUJO - nullExterno ao Programa - 1056845 - FELIPE PEDRO DA COSTA GOMES - null