Window frames for buildings are frequently made from PVC profiles by extrusion. Available in a wide range of colours, they are resistant to UV rays and severe weather conditions and are virtually maintenance free. They are also easy to fit and maintain and provide excellent heat insulation. The PVC resins used also have intrinsically high thermal stability, minimal sensitivity to moisture, flame retardant and are very easy to gel and process. An additional advantage for the use of such PVC in this application is its good mechanical properties (impact properties, which can be improved by using impact modifiers and/or PVC resins from the emulsion process).