Spread coating compound

Spread-coating compound. [Data from Mark RFD. Technical data sheet Crompton. 

PVC spread-coating pastes are normally manufactured in high-speed planetary mixers that can be evacuated. It is best to add the plasticizer first, stir in the pigments or pigment pastes and only then to add the solid components in portions. In pigmenting plasticized PVC compounds, on the other hand, it is necessary to mix... 

PVC resin applicability is defined mainly by particle size and molecular weight. Small-particle PVC made by emulsion or dispersion polymerization is typically compounded into a liquid or paste formulation and spread coated, sprayed, or molded by a number of techniques. Large-particle PVC made by suspension or mass polymerization is typically extruded, calendered, or injection molded. 

Briefly, you mix the adsorbant with water, spread the mix on the microscope slide in a thin layer, and let it dry, then activate the coating by heating the coated slide on a hot plate. Then you spot or place your unknown compound on the plate, let an eluent run through the adsorbant (development), and finally examine the plate (visualization). 

There are preprepared plates having an active coating on a thin plastic sheet, also with or without the fluorescent indicator. You can cut these to any size (they are about 8 in. by 8 in.) with a pair of scissors. Don t touch the active surface with your fingers — handle them only by the edge. The layers on the plate are much thinner than those you would make by spreading adsorbent on a microscope slide, so you have to use smaller amounts of your compounds so you don t overload the adsorbent. 

If considerable lapping is required, spread a thin coat of medium-coarse lapping compound on the block. After lapping with the medium-coarse compound, lap again with a medium-grade compound. Unless much lapping is called for, the first step can be omitted. 

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