Patent ID: 7273894

Claim:
A composition, comprising: (i) a polymer matrix comprising one or more polymers selected from the group consisting of: polyesters, polylactic acid, polyketones, polyamides, polysulfones, fluoropolymers, polyacetals, polyimides, polycarbonates, and copolymers thereof; wherein said polymer matrix has a glass transition temperature (Tg) of at least 50° C.; (ii) a voiding agent dispersed within said polymer matrix, comprising at least one first, non-crosslinked, polymer and at least one second, non-crosslinked, polymer wherein said first polymer has a Tg or a melting point temperature (Tm) greater than the Tg of said polymer matrix, a tensile modulus of at least 1 CPa, and a surface tension that differs from the surface tension of said polymer matrix by an absolute value of 5 dynes/cm or less; and said second polymer has a surface tension that differs from the surface tension of said polymer matrix by an absolute value of at least 5 dynes/cm and a melt viscosity wherein the ratio of said melt viscosity of said second polymer to the melt viscosity of said polymer matrix is about 0.1 to about 1.8.