Effects of Thermal Cure Protocols On Gelation Behavior and Cure-Induced Shrinkage of Benzoxazine Networks

Document Type

Conference Proceeding

Publication Date

1-1-2020

School

Polymer Science and Engineering

Abstract

Volumetric shrinkage of glassy amorphous polymer matrix networks during cure leads to internal strain in carbon fiber composite parts which resultantly translate to warpage in the final parts. Polybenzoxazine thermomechanical properties such as high glass transition temperatures, superior UV resistance, low coefficient of thermal expansion (CTE), and low shrinkage upon cure compared to more traditional aerospace thermosetting polymers. Recent advancements in continuous prepolymer reactor science provide new opportunities to prepare benzoxazine monomers with high degree of purity without the necessity of performing tedious work-up protocols. However, the polymerization conditions of this promising class of thermosets are still poorly understood with regard to cure-induced shrinkage. This research seeks to establish the relationship between cure shrinkage and cure protocol of polybenzoxazine networks. Herein, three different isothermal curing procedures were selected to achieve different degrees of conversion for the same network. The impact of the curing protocols on the frequency-independent gelation times of polybenzoxazines is determined. Futhermore, the effect of the three different cure protocols have on the chemical shrinkage is investigated through a novel technique which allows to track in real time the volumetric change of the polymer network. This research will ultimately contribute towards the understanding of the relationship between network formation of thermoset materials and the creation of internal strain in the manufacturing process of composite materials.

Publication Title

Composites and Advanced Materials Expo, CAMX 2020

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