Influence of elastic-viscoplastic behaviour on the filling efficiency of amorphous thermoplastic polymer during the micro hot embossing process

Abstract

An unsolved issue in simulating the hot embossing of polymers is modelling the unfilled structured mould. This is because the constitutive law of such polymers has not been adequately determined, especially at the microscale or smaller. The present study investigated the influence of the elastic-viscoplastic behaviour on the filling efficiency of an amorphous polymer during the micro hot embossing process. Constitutive equations based on the two-layer viscoplastic model were used to simulate the hot embossing process. The micro-cavity of the mould was completely filled by the polymer, and the elastic, viscous, and plastic behaviours were considered simultaneously in the simulation. Compression tests were performed to identify the model parameter values for poly-methyl methacrylate. A numerical simulation was performed to analyse the contributions of the polymer's elastic, viscous, and plastic behaviours. The unfilled area in the micro-cavity was evaluated after a displacement of 0.2 mm was applied to the mould. This was used as an indicator to compare the mould filling efficiency with those of the elastoplastic and elastic-viscoplastic constitutive models. The analysis led to the selection of an optimal elastic-viscoplastic model to completely fill the micro-cavity, which was consistent with the experimental results.

Microfabrication of Thermoplastic Polypropylene Surface Structures via Thermal Imprinting for Controlling the Adhesion of Easy Peel Package

“…The protruding microstructures on the PP surface improved with an increasing melt flow index when the temperature was below 175 °C. PP with a high MFI had a high effective filling ratio of micropattern arrays due to the low viscosity that flowed easily. , The MFI represents polymer melt flow properties at a specific temperature and pressure. , …”

“…PP with a high MFI had a high effective filling ratio of micropattern arrays due to the low viscosity that flowed easily. 49 , 50 The MFI represents polymer melt flow properties at a specific temperature and pressure. 51 , 52 …”

“…PP with a high MFI had a high effective filling ratio of micropattern arrays due to the low viscosity that flowed easily. 49,50 The MFI represents polymer melt flow properties at a specific temperature and pressure. 51,52 To illustrate the changes in flow behavior driven by polymer viscosity in the hot embossing method, PP was imprinted at two MFI values.…”

Multi-Scale Numerical Approach to the Polymer Filling Process in the Weld Line Region

“…In our previous work [22], the double-equation eXtended Pom-Pom (DXPP) stress equation was adopted to describe the molecular orientation in the flow of polymer melt. It is known that some researches based on the molecule's scale are widely used in various areas [23][24][25][26][27]. Cocker et al [24] tracked a single molecule's trajectory on a molecule's scale by femtosecond orbital imaging.…”

Effect of temperature on the SU‐8 photoresist filling behavior during thermal nanoimprinting

“…Cheng et al [ 26 ] analyzed the viscoplastic behavior of PMMA during thermal imprinting process under various temperature conditions slightly above the glass transition temperature ( T g ). Rabhi et al [ 27 ] performed a numerical simulation to analyze the contributions of the polymer elastic, viscous, and plastic behaviors of PMMA, and investigated the influence of the elastic‐viscoplastic behavior on the filling efficiency of PMMA during the thermal imprinting process. Chang et al [ 28 ] studied the influence of thermal imprinting process parameters on the polycarbonate (PC), and found that with increase in temperature, the imprinted height increases since at high temperature the viscosity of PC is reduced which ensures proper filling of the cavity.…”