Banca de QUALIFICAÇÃO: ANA CLÁUDIA MEDEIROS DE CARVALHO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA CLÁUDIA MEDEIROS DE CARVALHO
DATA : 04/08/2017
HORA: 09:00
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

SYNTHESIS OF POLY(UREA-FORMALDEHYDE) MICROCAPSULES FILLED WITH DICYCLOPENTADIENE TO USE IN SELF-HEALING SYSTEMS

PALAVRAS-CHAVES:

Self-healing, microcapsules’ synthesis, polymeric composite, poly(urea-formaldehyde), dicyclopentadiene.

PÁGINAS: 104
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
ESPECIALIDADE: Polímeros, Aplicações
RESUMO:

Self-healing materials are a class of smart materials with an inherent ability to repair damage, thus recovering their functionality. Urea-formaldehyde microcapsules have been studied to provide self-healing functionality to polymers and polymeric matrix composites. These microcapsules must be strong enough to remain intact during processing of the host polymer, and yet break when the polymer is damaged. A well-known self-healing system comprises an epoxy matrix with urea-based microcapsules containing dicyclopentadiene (DCPD). Upon release, DCPD can undergo ring-opening metathesis polymerization (ROMP) when in contact with a pre-embedded dispersed Grubbs’ catalyst. As the healing agent encounters the embedded catalyst, a polymerization reaction is initiated and proceeds until all released healing agent is consumed. The resulting polymer (poly(DCPD) serves as a bonding agent that bridges the crack, regaining much of the initial material properties. In this work, urea-formaldehyde microcapsules were synthesized by in situ polymerization in an oil-in-water emulsion. In preliminary studies, four vegetable oils (soybean, linseed, olive and coconut oil) were used in substitution of DCPD due to its acute toxicity and strong smell. The main idea was to study microcapsules synthesis using a non-toxic core material, which would later be substituted by DCPD, when microcapsule synthesis and polymer processing parameters were consolidated. The microcapsules synthesized were characterized by Fourier Infrared Spectroscopy (FTIR) and Scanning Electronic Microscopy (SEM). The preliminary results showed that it was possible to produced microcapsules made of poly(urea-formaldehyde) filled with all vegetable oils used. Most capsules synthesized presented diameter around 50 µm, a suitable size for application in epoxy matrix or epoxy coating. Microcapsules filled with soybean oil were choose to be part of an activated coating with self-healing ability. The preliminary results showed that the metallic substrates presented higher corrosion resistance when the activated coating was used. Microcapsules filled with endo-DCPD were also synthesized and presented the same characteristics as the ones filled with vegetable oils. This capsules were introduced in epoxy matrix samples for the self-healing effect tests along with Grubbs catalyst and a low cost liquid catalyst (stannous octoate). However, due to agglomeration and poor dispersion of the microcapsules within the epoxy matrix, the self-healing effect could not be verified. Besides, it was observed that a post-cure of the samples was necessary before the realization of the self-healing tests.

MEMBROS DA BANCA:
Externo à Instituição - AMELIA SEVERINO FERREIRA E SANTOS - UFPB
Externo ao Programa - 2042234 - ANA PAULA CYSNE BARBOSA
Externo ao Programa - 1064594 - EVANS PAIVA DA COSTA FERREIRA
Interno - 1202134 - JOSE DANIEL DINIZ MELO
Presidente - 1755267 - MARIA CAROLINA BURGOS COSTA DO NASCIMENTO