Acrylic Impact Modifier

About This Product

Acrylic impact modifiers share the core-shell architecture of MBS but replace the polybutadiene core with a crosslinked acrylate rubber, typically poly(butyl acrylate), retained inside a methacrylate shell. The reason for that substitution is weathering. Polybutadiene contains carbon-carbon double bonds in its backbone, and those are the sites where ultraviolet and oxygen attack, so an MBS-modified article loses impact strength outdoors over time. A saturated acrylate rubber has no such sites, so an acrylic-modified compound keeps its impact resistance through years of exposure. The cost is optical: acrylic modifiers do not index-match PVC as closely, so they are used in opaque rather than clear articles. This is why window profile, siding and fencing are almost universally acrylic-modified while clear packaging is MBS-modified. The principal grade is a white free-flowing powder supplied 25 kg per drum, 0.9 MT per pallet, 9 MT per 20-foot container, offering long-term weather resistance, retained and low-temperature impact resistance and ease of processing in rigid vinyl. KM-355P (also designated KM-1) and KM-606P are available grades in 20 kg bags for outdoor rigid PVC products and PVC injection moulding.