Articles including high melt flow index resins
Certain embodiments described herein are directed to composite materials comprising one or more high melt flow index resins. In some examples, the composites can be used to provide automotive parts such as, for example, vehicle interior parts and vehicle exterior parts. In some configurations, the composite comprises a fiber reinforced polymer core comprising reinforcing fibers and a resin comprising a high melt flow index of greater than 325 g/10 min. as measured by ASTM D1238, condition L.
1. A method comprising:
adding reinforcing fibers and a polyolefin polymer resin to an agitated liquid-containing foam to form a dispersed mixture of the polyolefin polymer resin and reinforcing fibers, wherein the polyolefin polymer resin comprises a melt flow index greater than 100 g/10 min. as measured by ASTM D1238, condition L and wherein the polyolefin polymer resin is present in the dispersed mixture from 20% to 70% by weight and the reinforcing fibers are present from 30% to 70% by weight in the dispersed mixture, wherein the reinforcing fibers comprise a diameter from 5 microns to 22 microns and length from 5 mm to 75 mm;
depositing the dispersed mixture of reinforcing fibers and polyolefin polymer resin onto a forming support element comprising a mesh;
evacuating the liquid from the mesh to form a web;
heating the web above the softening temperature of the polyolefin polymer resin; and
compressing the web using a first set of heated nip rollers to a predetermined thickness to form a composite material to provide an open cell structure within the composite material, wherein about 40% to about 100% of the open cell structures are open and allow the flow of air and gases through the composite material;
passing the compressed web through a second set of heated nip rollers, wherein a temperature provided by the second set of heated nip rollers is lower than a temperature provided by the first set of heated nip rollers;
adding a first surface layer to a first surface of the composite material, wherein the first surface layer comprises one or more of a fabric, a film and a scrim that is continuous from one side of the compressed web to the other side of the compressed web;
adding a second surface layer to a second surface of the composite material; and
passing the composite material with the added first surface layer and the added second surface layer through a pair of nip rollers to provide a composite article, wherein the composite article comprises 5% to 95% voids distributed uniformly through the thickness of the web of the composite article.
2. The method of claim 1 , further comprising selecting the polyolefin polymer resin to comprise polypropylene comprising a melt flow index greater than 325 g/10 min. and less than 750 g/10 min. as measured by ASTM D1238, condition L.
3. The method of claim 1 , further comprising selecting the polyolefin polymer resin to comprise polypropylene comprising a melt flow index greater than or equal to 750 g/10 min. and less than 1000 g/10 min. as measured by ASTM D1238, condition L.
4. The method of claim 1 , further comprising selecting the polyolefin polymer resin to comprise polypropylene a melt flow index greater than 1000 g/10 min. and less than 1250 g/10 min. as measured by ASTM D1238, condition L.
5. The method of claim 1 , further comprising selecting the polyolefin polymer resin to comprise polypropylene comprising a melt flow index of at least 325 g/10 min. as measured by ASTM D1238, condition L, selecting the reinforcing fibers to comprise glass fibers, and molding the composite material to provide an automotive interior headliner.
6. The method of claim 1 , further comprising selecting the polyolefin polymer resin to comprise polypropylene comprising a melt flow index of at least 325 g/10 min. as measured by ASTM D1238, condition L, selecting the reinforcing fibers to comprise glass fibers, and molding the composite material to provide an automotive underbody shield.
7. The method of claim 1 , further comprising lofting the composite article using heat to provide a composite article with an increased thickness.
8. The method of claim 1 , further comprising selecting the thermoplastic polymer resin of the composite article to be polypropylene with a melt flow index of at least 325 g/10 min. as tested by ASTM D1238 condition L, selecting the reinforcing fibers to be glass fibers, and wherein the polymer resin is present from 30-70 weight percent based on the weight of the composite material.
9. The method of claim 1 , further comprising molding the composite article using heat to loft the composite article and provide a molded part.
10. The method of claim 9 , further comprising configuring the molded part as an automotive interior headliner.
11. The method of claim 9 , further comprising configuring the molded part as an automotive underbody shield.