Reduced density hollow glass microsphere polymer composite

A melt processing method of manufacturing a hollow glass microsphere and polymer composite from a mixture, said method comprising:

• (a) pre-treating a hollow glass microsphere with an effective composite forming amount of an interfacial modifier coating;
• wherein the interfacial modifier is free of a coupling agent;
• and wherein the hollow glass microsphere has a particle size of at least about 5 microns;
• (b) combining a thermoplastic polymer phase with about 30 to 95 volume % of the pre-treated interfacial modifier coated hollow glass microsphere, in an amount that can substantially occupy excluded volume of a hollow glass microsphere particle distribution in the composite;
• and
• (c) melt process compounding the mixture to form the composite comprising the pre-treated hollow glass microspheres within the thermoplastic polymer phase;
• wherein the hollow glass microsphere exhibits a circularity greater than 13 and an aspect ratio less than 1:3;
• and wherein the interfacial modifier coating allows for greater freedom of movement between the pre-treated hollow glass microsphere within the polymer phase compared to the same composite without the interfacial modifier coating on the hollow glass microsphere, when measured under the same conditions.