Welding dynamics in an atomistic model of an amorphous polymer blend with polymer–polymer interface

Dmitry G Luchinsky,Kenta Chaki,Taku Ozawa,Peter V E Mcclintock,Tracie J Prater,Vasyl Hafiychuk,Halyna Hafiychuk,Hiroya Nitta,Kevin R Wheeler

doi:10.1002/pol.20190253

Dmitry G Luchinsky, Kenta Chaki + Show 7 more

Open Access

https://doi.org/10.1002/pol.20190253

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Abstract

AbstractWe consider an atomistic model of thermal welding at the polymer‐polymer interface of a polyetherimide/polycarbonate blend, motivated by applications to 3D manufacturing in space. We follow diffusion of semiflexible chains at the interface and analyze strengthening of the samples as a function of the welding time tw by simulating the strain–stress and shear viscosity curves. The time scales for initial wetting, and for fast and slow diffusion, are revealed. It is shown that each component of the polymer blend has its own characteristic time of slow diffusion at the interface. Analysis of strain–stress demonstrates saturation of the Young's modulus at tw = 240 ns, while the tensile strength continues to increase. The shear viscosity is found to have a very weak dependence on the welding time for tw > 60 ns. It is shown that both strain–stress and shear viscosity curves agree with experimental data.

Highlights

Understanding the properties of polymer-polymer interfaces represents a long-standing problem that is of both fundamental and technological importance[1,2,3]
We further demonstrate that the dependence of the shear viscosity η on the shear rate in our model is linear on a log-log scale, corresponding to the expected shear-thinning behavior of the PEI/PC blends
Welding takes place at the interface flat separated faces with initial gap shown in Fig. 1. and in what follows we focus on the analysis of this interface

Summary

Introduction

Understanding the properties of polymer-polymer interfaces represents a long-standing problem that is of both fundamental and technological importance[1,2,3]. Thermal cycling was performed for an additional 1 μs to analyze the thermomechanical properties of welded samples, which were shown to be in agreement with experimental data, as will be discussed in detail elsewhere[39]. The “Results” section discusses the interfacial diffusion of polymer chains, uni-axial sample deformation and the dependence of the shear viscosity on temperature and shear rate.

Results

Conclusion