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New polyurethane pultrusion technology offers improved processing, physical and thermal properties that make it ideally suited for residential and commercial window applications.The polyurethane resins contain bio-based feedstocks and are styrene-free, offering benefits to both producers and consumers.The profiles require a surface coating to provide UV resistance and have been challenging to paint without some surface treatment.We describe recent work done to develop highly weatherable 2-k urethane topcoat formulations based on hydroxy functional PVDF-acrylic hybrid emulsion polymers crosslinked with water dispersible polyisocyanates.These coatings have such excellent adhesion to pultruded substrates that a primer coat is not needed.Besides adhesion, the formulations were also developed to provide early hardness and solvent resistance, as well as mechanical and chemical resistance properties required for window profiles(e.g.AAMA 625).Their excellent decorative property retention was achieved through design of the polymer components.