Polyolefin wood fiber composite

A weatherable, mechanically stable thin walled complex hollow profile comprising, mechanically stable and thermally stable polymer/fiber composite comprising:

• (a) greater than about 25 wt % of a polyoefin composition having a melt index of about 1.2 or about 2 gm/10 min, a melting point of about 145° C. to 158° C.;
• (b) greater than about 50 up to 75 wt % of a wood fiber, the fiber having a moisture content of less than 5000 parts of water per million parts of the fiber, a particle size of about 100 to about 2000 μm and an aspect ratio of about 1:2 to about 1:5;
• and
• (c) about 20 to 35 wt % of a polymer/fiber compatibilizer;
• wherein the profile comprises an extruded complex hollow member having a defined support direction the tensile modulus of the composite is greater than about 8·105 psi the HDT of the profile in the defined support direction is greater than about 75° C. at 264 psi (ASTM D 696), the compressive strength of the profile in the defined support direction is greater than about 1200 psi.

A weatherable, mechanically stable thin walled complex hollow profile comprising, mechanically stable and thermally stable polymer/fiber composite comprising:

• (a) about 25 to 40 wt % of a polypropylene polymer composition having a melt index of about 1.2 or about 2 gm/10 min, a melting point of about 148 to 158° C., a molecular weight (Mw) of about 20,000 to 80,000 and an ethylene content of about 0.1 to about 10 wt %;
• (b) about 65 to 75 wt % of a wood fiber, the fiber having a moisture content of less than about 4000 parts of water per million parts of fiber, a particle size of about 150 to about 800 μm and an aspect ratio of about 1:2 to about 1:5;
• and
• (c) about 0.1 to about 5 wt % of a polymer fiber compatibilizer comprising a polypropylene polymer having a molecular weight of about 5000 to about 50,000 having grafted thereto maleic anhydride in an amount of about 15 to about 50 moles of maleic anhydride per mole of polymer composition;
• wherein the profile comprises an extruded complex hollow member having a defined support direction the tensile modulus of the composite is greater than about 8·105 psi, the HDT of the profile in the defined support direction is greater than about 135° C. at 264 psi.