EFFECTS OF PROCESS CONDITIONS ON POLYMER NETWORK FORMATION: APPLICATION IN PARTICLE COATING AND MODELING USING MOLECULAR DYNAMICS

Abstract

Cross-linked polymers are of great importance to industrial practice and theoretical studies. The unique network structures of these materials have endowed them with many superior properties. In this thesis, we study cross-linked polymers from both of experimental and theoretical sides, with an emphasis on the formation process and properties of the prepared networks. Two specific problems are investigated: development of polymer coatings over solid particles with in situ curing, and molecular dynamics (MD) study of network formation kinetics and structure-property relationship. In the study of polymer coating, a hot-melt coating process for solid particles is developed. Phenolic resin is used to coat the substrates and subsequently cured in situ. Among various processing parameters, temperature is found to play an especially important role in the coating performance. Higher temperature leads to stronger coating layers with better barrier properties, whereas lower temperature is preferable for better surface morphology. These two trends can be partially reconciled with ramping temperature profiles; however, the improvement is eventually limited by the rate of heat transfer. In MD study, the effects of precursor topology on the formation, structure and mechanical properties of polymer networks are studied. Cross-linked polymer networks are synthesized from three sets of precursors with varying chain length. Little difference is observed between these networks in typical properties including radial distribution function, overall statistics of network connectivity, and glass transition behaviors. The elastic modulus of the network is found to correlate strongly with the number of elastic strands in the network, except at the highly-cross-linked limit where substantial discrepancy is observed between networks from different precursors. Although these final networks contain a similar level of structural defects, the choice of precursor has a significant effect on the spatial distribution of the defects, which explains the precursor dependence of their mechanical property observed in the tensile test.