Capstock layer

Extrudable thermoplastic with capstock layer. [Data from Jeng, j p, us Patent... 

Building material and method of its manufacture is included in invention. Product includes an extrudable thermoplastic (e.g., PVC of the above formulation) or thermosetting substrate having a fluorocarbon-based capstock layer... 

Vinyl siding is manufactured by co-extrusion. The lower layer (substrate) is typically PVC, while the top layer (capstock) is the weatherable surface of the siding. Two common capstocks are PVC and AS As and similar polymers. 

Except in cases where the outer layer is acrylic, for example, Acryhgard (Rohm Haas) or PVDF (Kynar ), vinyl siding is extmded in dual layers, mainly an inner layer, substrate, and the outer weatherable layer, capstock. (The terms come firom siding jargon that predates the appearance of PVC.) The bulk of the product is, of course, substrate, which uses reverse ester tin stabilizers ... 

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