Optimization of synthesis parameters of PUF/ENB microcapsules for self-healing applications using factorial design methodology

This study introduces a systematic experimental approach aimed at enhancing the production process of poly(urea-formaldehyde) (PUF) microcapsules filled with 5-ethylidene-2-norbonene (ENB) using in situ emulsion polymerization. Essential parameters were identified through a prior Plackett Burman (PB) design, leading to the implementation of a (24-1) fractional factorial design. The key parameters selected encompassed stirring speed, poly(ethylene-alt-maleic anhydride) (EMA) emulsifier content, pH of the reaction, and the quantity of 1-octanol. Optimal conditions for polymeric microcapsule synthesis were determined using a statistical analysis of the complete factorial design, facilitating the development of representative mathematical models for the process. A comprehensive evaluation of response variables including microcapsule diameter, yield, encapsulated content, stability, and thermal degradation was conducted. Utilizing response surface analysis (RSM), it was determined that the PUF/ENB(2C) condition (stirring at 700 rpm, a reaction pH of 3.0, and EMA content of 0.425 g) resides within the optimized synthesis region, producing microcapsules exhibiting favorable morphological characteristics, yield of 52% and encapsulated content of 80%.