Banca de DEFESA: ANA CLÁUDIA MEDEIROS DE CARVALHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE : ANA CLÁUDIA MEDEIROS DE CARVALHO
DATA : 15/12/2017
HORA: 08:30
LOCAL: Auditório do CCET
TÍTULO:

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

PALAVRAS-CHAVES:

Self-healing, microcapsules’ synthesis, experimental design, poly(urea-formaldehyde).

PÁGINAS: 138
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, synthesis parameters of poly(urea-formaldehyde) microcapsules were evaluated and an experimental design 22 with three central points was assembled, with the objective of analyze the influence of agitation rate and pH in the size of microcapsules and thickness of capsules shell. The influence of agitation rate on microcapsules size and pH on shell thickness could be proven. From the experimental design results, microcapsules with different core materials such as, vegetable oil (soybean, olive, linseed and coconut), endo-dicyclopentadie and 5-etilidene 2-norbonene (ENB) were synthesized presenting same morphological characteristics and size. Capsules were characterized by Fourier infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Microcapsules filled with soybean, linseed oil and endo-DCPD were used in epoxy system with self-healing ability aiming delay corrosion in metallic substrate. Samples with capsules filled with soybean and linseed oils presented excellent anticorrosive results, with emphasis on the system containing capsules filled with soybean oil, which is an economical alternative to the other tested materials. Microcapsules filled with endo-DCPD were used in indentation tests to verify the self-healing effect, however, it was not possible to attest it, since the indentation did not generate a crack in the samples. Therewith, the behavior of the microcapsules obtained under the adjusted conditions of the experimental design was analyzed in epoxy samples by means of tests where cracks were produced using a blade, capsule rupture was verified as consequence of crack propagation. Capsules which presented adequate diameter and shell thicknesses for their use in the proposed self-healing system, were produced. However, due to the agglomeration and poor dispersion of the microcapsules in the epoxy matrix, in addition to the low amount of catalyst presented, the self-healing effect could not be proven in polymeric or polymeric composites samples.

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