Design and technological parameters of equipment influence on the lateral pressure coefficient and reduced friction coefficient of granular polyvinyl chloride

Introduction.The dependence of the lateral pressure coefficient and the reduced friction coefficient of granular polyvinyl chloride was determined for the production of packaging material from the design and technological parameters of the feeding process.Materials and methods.Experiments has been carried out on the stand which simulating the movement of polymer granules in the working channel of a single-screw extruder for such parameters: the polymer being researchedpolyvinyl chloride (PVC); the axial pressure -0.044-0.475MPa; the temperature of the steel limiting surface -20-80 °С; the speed of the steel limiting surface -0.176-0.471m/s; the height of the granular polymer layer -0.015-0.025m.Results and discussion.The value of the lateral pressure coefficient increases under the following conditions: temperature increase; reduction of axial pressure; speed reduction; the lateral pressure coefficient does not depend on the height of the granules layer.Provided simultaneous changes in temperature and pressure to a level of approximately 0.32 MPa increase in temperature leads to increased values of lateral pressure, after iton the contrary, to reduce.In case of speed change after point 0.15 MPa dependence also reversed.Most on the growth of the lateral pressure coefficient of the studied polymer affects the simultaneous action of the temperature and the speed of the steel limiting surface.The central role in changing the lateral pressure coefficient is having by speed, and in changing the friction coefficient have by temperature.In the case of simultaneous temperature rise with the speed and the layer of granules height there is a transition through the point at the level of approximately 0.32 MPa.To this point, an increase in temperature leads to an increasing in the corresponding values of the lateral pressure coefficient.After this point on the contraryto decreasing in the corresponding values of the lateral pressure coefficient.The same in case of speed change, after the point 0.15 MPa the dependence is reversed.In the case of simultaneous rise the speed and the temperature from 20 to 80 °C the larger values of speed correspond to the smaller values of lateral pressure coefficients.The increase in temperature leads to an increase in the lateral pressure coefficients from 0.33-0.34 to 0.42-0.46.In the case of simultaneous rise the speed and the pressure the lower pressure values do not affect the dependence of the values of the lateral pressure coefficient on the speed.An increase in pressure from 0.044 to 0.476 MPa leads to corresponding change to increasing dependence from 0.22-0.27 to 0.34-0.46.Subject to change in temperature, speed and granule layer height an increase in temperature leads to a corresponding increase values of the friction coefficient at the same pressure from 0.48-0.5 to 0.52-0.57as well as increasing speed.Conclusions.The obtained results make it possible to take into account the mutual influence of the friction and the lateral pressure coefficients of the granular polymers and the design and technological parameters of the extruder or screw feeder.