Prediction of angular and mass distribution in meltblown polymer lay-down

Predictions of the properties of meltblown polymer nonwovens require knowledge of the angular fiber distribution in lay-down, as well as the deposited mass distribution. In the present work these two important characteristics are predicted using our previously developed model describing multiple three-dimensional viscoelastic polymer jets in meltblowing and their deposition onto a moving screen normal to the blowing direction. The results are important for predictions of strength of meltblown nonwovens.     

Polymer melting temperatures and crystallinity at different pressure applied

The present work aims at the experimental investigation of the effect of an increased thermal bonding pressure on the melting point (the so-called Clapeyron effect) of three polymers employed in nonwovens. Namely, this work quantifies the dependence of melting temperature on pressure in these polymers. The following three polymers were used in the present experiments: polybutylene terephthalate (PBT), polyethylene terephthalate (PET), and polypropylene (PP) (all three already received in the form of nonwovens). A simple novel method of measurements of melting points of such polymers under different pressures was proposed and developed. The results revealed: (i) the melting point of PBT nonwovens increased by about 12°C when the applied pressure was increased up to 277.79 atm; (ii) the melting point of the PET nonwovens increased by about 7°C when the applied pressure increased up to 104.86 atm; (iii) the melting point of PP nonwovens increased by about 6°C when the applied pressure was increased up to 104.86 atm. The melting temperature measurements by the present method were also validated through differential scanning calorimetry measurements with the above-mentioned three polymers without applied pressure.     

Experimental Investigation of Particle Removal from Surfaces by Pulsed Air Jets

This work presents an experimental study of particle removal from surfaces by means of a pulsed air jet directed toward the particle-laden surface. During the experiments, solid particles were dispersed over the surface, forming a layer of particles that did not touch each other. Under these conditions, resuspension of an individual particle was independent of the number of particles and their location. We attempt to explain the observed phenomena by analogy to heat transfer enhancement by pulsed jets. It is expected that since pulsed jets are effective in surface cooling, their application to improved surface cleaning should be promising. For a pulsed jet, we investigated the effect of pulse frequency on particle removal. It was found that particle removal efficiency could be significantly affected by the frequency of the jet. In particular, for a fixed jet velocity, the efficiency increases with frequency, reaches a maximum, and then decreases.