Experiments and Modelling of Calender Processing for Shear Thinning Thermoplastics between Counter Rotating Rolls with Differential Velocities

Abstract

This paper is concerned with a floor application calendering processing using both a PVC and a Polyolefin formulation within a two roll calender. The rheology of both formulations was measured using the Rheoplast, a specific capillary rheometer. Experiments with various velocity differentials were performed and the roll separating force and the sheet exit temperature were measured for each case. An isothermal model based on the lubrication approximations hypothesis together with a power-law behavior for the molten polymer has been developed. Due to the difference between the rotation velocities of the two cylinders, the problem is no longer symmetric and the integration of the generalized Reynolds equation requires taking into account various velocity profiles. The resulting pressure profile enables computation of the roll separating force. The agreement between the model and experiments performed with the PVC formulation at various velocity differentials is fair; however for the Polyolefin formulation there is a significant difference which means that the model for this new formulation needs to be improved.

Impact of Triple Roll Milling Processing Parameters on Fluidic/Rheological and Electrical Properties of Aqueous Graphene Ink

“…[8] The viscosity and shear rate have a strong relationship with the shear stress provided by the rollers to the ink constituents. Shear rate and shear force exerted in the nip gap were calculated as per the literature [12,15] and are shown below…”

“…The viscosity and shear rate have a strong relationship with the shear stress provided by the rollers to the ink constituents. Shear rate and shear force exerted in the nip gap were calculated as per the literature and are shown belowwhere γ is the shear rate, V 1 and V 2 are the linear velocities of the rollers, and g is the separation between the rollers having nearly linear velocities.…”

“…Depending upon the linear velocity difference of the rollers and nip gap, the shear rate and shear force experienced by the ink constituents can be calculated. [12,15] Each material has unique bond strength and an energy threshold level to break down in smaller particles; along with this, the breaking pattern and saturation level of breakage are distinct in each case. [16] Graphene is a strong candidate for the formulation of functional ink in the area of flexible printed devices due to its ultrahigh conductivity and flexibility in comparison with other functional materials.…”

“…The relative speed of the rollers and gap in between can be changed as per requirement. Depending upon the linear velocity difference of the rollers and nip gap, the shear rate and shear force experienced by the ink constituents can be calculated …”

In Situ Exfoliation of Graphene in Epoxy Resins: A Facile Strategy to Efficient and Large Scale Graphene Nanocomposites

“…In Figure 2a, the estimated shear rates achieved in the two TRM Protocols are presented. Shear rates and shear stresses are calculated by modeling the TRM process in analogy to a recent work of Magnier et al, 36 who developed a model to describe the calendering process (in particular the rolls separating force) of power-law non-Newtonian fluids between counter rotating rolls at different velocities. The isothermal model was based on the lubrication approximation, as in classical calendering models.…”