writer：C. Luo*, B. Zhang*, W. Zhang, C. Yuan, M. Dunn, Q. Ge, K. Yu
keywords：Reprocessable thermoset， 3D printing， Bond exchange reaction， Dual-stage polymerization， Chemomechanics modeling
source：期刊
specific source：Journal of the Mechanics and Physics of Solids
Issue time：2019年
The recently developed dual-stage 3D printing reprocessable thermosets (3DPRTs) utilize acrylate functional groups to enable the ultra-violet based 3D printing (Stage I), and em- ploy bond exchange reaction (BERs) to tailor the network structure for mechanical prop- erties enhancement and impart the reshapeability, reparability, and recyclability into tra- ditionally unprocessable thermosets (Stage II). 3DPRT provides a practical solution to ad- dress environmental challenges associated with the rapid increase in the consumption of 3D printing materials. However, due to the nascent state of development, fundamental un- derstanding of the chemomechanics during the processing of 3DPRTs is still lacking. In this paper, we present detailed experimental and theoretical studies to understand the effect of thermal treatment condition at Stage II on the evolution of network structure and thermomechanical properties of 3DPRTs. A chemomechanics theory is defined to link the molecular-level BER kinetics to the macroscale thermomechanical properties of 3DPRTs during the thermal treatment. A thermo viscoelastic multi-branched constitutive model is then established to capture the elastic and glass transition behaviors during the Stage II processing. The developed theory is able to capture the experimental observations on the mechanical properties enhancement and provide theoretical guidance for the network de- sign and the selection of thermal treatment conditions to tailor the final mechanical prop- erties of 3DPRTs.