On-Line Monitoring of PVC Foam Density Using Ultrasound Waves and Artificial Neural Networks

An artificial neural network (ANN) model was developed to monitor the density of rigid foam PVC on-line during the extrusion process using an ultrasound sensor mounted on the extruder die. Acoustic properties of the polymer melt, measured by multiple ultrasound echoes propagating through the polymer melt, were used to train a multilayer perceptron (MLP) artificial neural network to estimate the density of the extruded foam. The foam density was varied by varying the processing conditions, i.e. heating zones and screw speed, during the extrusion process. A high correlation was found to exist between the acoustic properties of the polymer melt and the foam density using a three-layer multilayer perceptron artificial neural network.

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