Loss modulus, plastics viscosity

Figure 5.41. Increase in storage modulus (which parallels the rise in viscosity) from the onset of reaction for a supported sample (resin coated onto an inert substrate) of an epoxy resin. Curve (a) is the isothermal storage modulus-cure time plot curve (b) shows loss modulus. The storage modulus rises in two steps, the first due to gelation and the second to vitrification, and then levels off at a high value characteristic of the glassy state. The loss modulus peak indicates the time to vitrify. High performance epoxy, cure at 155 °C (from Lee and Goldfarb, 1981a, b with permission of the Society of Plastics Engineers).

With dynamic testing, the processed plastic s elastic modulus (relating to energy storage) and loss modulus (relative measure of a damping ability) are determined. Steady testing provides information about creep and recovery, viscosity, rate dependence, etc. 

Kaolin deposits are cored and analyzed before mining to determine quality. Mined clays are then either wet or dry processed by air floatation or water fractionation. Surface-modified clays can be made by treating standard, delaminated, and calcinated grades with surface modifiers. The treatment can be performed by either the supplier or the end user. These surface modifiers include silane, titanate, polyester, and metal hydroxide. The objective of these surface treatments is to increase filler loadings and/or improve physical properties such as melt viscosity, thermal stability, and modulus without loss of physical characteristics. Electrical applications represent the largest use of surface-modified kaolin in plastics. 

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