Banca de DEFESA: MARIA PAULA DE CARVALHO FREIRE
Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.STUDENT : MARIA PAULA DE CARVALHO FREIRE
DATE: 29/09/2023
TIME: 14:00
LOCAL: meet.google.com/xre-vseu-uxh
TITLE:
Optimization of poly(urea-formaldehyde) (PUF) polymeric microcapsules filled with 5-ethylidene-2-norbonene synthesis for self-healing using factorial design methodology
KEY WORDS:
Self-healing; in situ polymerization; polymeric microcapsules; factorial design; poly(urea-formaldehyde).
PAGES: 118
BIG AREA: Engenharias
AREA: Engenharia de Materiais e Metalúrgica
SUBÁREA: Materiais Não-Metálicos
SPECIALTY: Polímeros, Aplicações
SUMMARY:
In the recent decades, research on materials with self-healing capacity has progressively expanded, and self-healing systems with polymeric microcapsules are included in the solutions proposed to repair the damage due to the appearance of cracks that structurally compromise the lifetime of the material during use, enabling cost reduction. In this work, poly(urea-formaldehyde) (PUF) microcapsules filled with 5-ethylidene-2-norbonene (ENB) were prepared by in situ emulsion polymerization. A previous analysis of developed works using a Plackett-Burman (PB) design with seven factors helped in the selection of variables to be used in a fractional factorial design 24-1 and, based on this, it was possible to select the significant variables as 90% confidence to perform a complete factorial design with three factors, aiming the optimization of the synthesis process. The chosen parameters for the fractional design include: the agitation speed, the poly(ethylene-alt-maleic) (EMA) content that acts as an emulsifier, the drops of 1-octanol (stabilizes the emulsion inhibiting the formation of bubbles) and the pH of the reaction. The responses evaluated were the medium diameter of the microcapsules, yield, encapsulate content, thermal stability, and the degradation temperature. From the parameters analyzed, the EMA content, the pH of the reaction and the agitation speed must be used in the complete design due to their significant effects on the response variables analyzed, using a confidence level of 90%. In a previous analysis to the complete design, considering the analyzed response variables, microcapsules with satisfactory properties for applications in self-healing were obtained in the condition in which the agitation speed and the EMA content were at higher levels, and the pH was at the lower level, corresponding to the synthesis of PUF/ENB 4 of the fractional design. After realising the full factorial design, no valid mathematical models were found for the yield and encapsulated content response variables at a 90% confidence level. However, a valid mathematical model was obtained for the medium diameter response variable. Microcapsules with satisfactory morphological conditions such as the low residue of U/F on the surface and symmetry were obtained in the conditions in which agitation and pH were at the upper and lower levels, respectively. To define the optimum condition for producing microcapsules, the medium diameter response variable was considered based on the mathematical model obtained, and a combined analysis was perfomed based on yield and encapsulate content. Therefore, using the response surface methodology (RSM) in conjunction with the thermal stability analysis, it was concluded that the synthesis condition (puf/enb 2) showed microcapsules with adequate morphological properties, including a regular shell surface, low residue of U/F, a narrow medium diameter distribution, in addition to a satisfactory yield and encapsulate content.
COMMITTEE MEMBERS:
Presidente - 1755267 - MARIA CAROLINA BURGOS COSTA DO NASCIMENTO
Interno - 1202134 - JOSE DANIEL DINIZ MELO
Externa à Instituição - MARIA INGRID ROCHA BARBOSA SCHIAVON - UNICAMP