Process and article produced by injection molding
The present disclosure relates to a process and article produced by injection molding. More particularly, a process and article produced by injection molding, that provides a part with one or more locations of a reduced density where such part competes in mechanical property characteristics with parts, such as vehicular components, otherwise produced from metallic materials.
1. A method of forming an injection molded part comprising:
providing an injection mold comprising a first mold half and a second mold half that provides a molding cavity between the first mold half and the second mold half, wherein the molding cavity includes one or more locations having an initial spacing;
injecting a polymer composition into the molding cavity, the polymer composition comprising: (a) a first polymer having a melt strength of greater than or equal to 20.0 cn and a melt extensibility of greater than or equal to 100 mm/sec; (b) a second thermoplastic polymer having a melt flow index of greater than or equal to 10.0 g/10.0 minutes; (c) reinforcing fiber; (d) a foaming agent;
increasing said molding cavity initial spacing at said one or more locations; and
forming the injection molded part in the molding cavity from the polymer composition wherein the injection molded part includes a cellular structure.
2. The method of claim 1 wherein said first polymer having a melt strength of greater than or equal to 20 cn and a melt extensibility of greater than or equal to 100 mm/sec is present in said polymer composition at a level of 10.0% (wt.) to 90.0% (wt.) and said second thermoplastic polymer is present in said polymer composition at a level of 90.0 wt. % to 10.0 wt. %.
3. The method of claim 1 wherein said initial spacing is in the range of 1.0 mm to 6.0 mm.
4. The method of claim 1 wherein said increase in said mold cavity initial spacing is in the range of 3.0 mm to 20.0 mm.
5. The method of claim 1 wherein said initial spacing is in the range of 1.0 mm to 6.0 mm and said increase in said mold cavity initial spacing is in the range of 3.0 mm to 20.0 mm.
6. The method of claim 1 wherein said first polymer having a melt strength of greater than or equal to 20.0 cn has a melt strength in the range of 20.0 cn to 200.0 cn.
7. The method of claim 1 wherein said first polymer having a melt extensibility of greater than or equal to 100 mm/sec has a melt extensibility in the range of 100 mm/sec to 300 mm/sec.
8. The method of claim 1 wherein said second thermoplastic polymer having a melt flow index of greater than or equal to 10.0 g/10.0 minutes has a melt flow index in the range of 10.0 g/10.0 minutes to 40.0 g/10.0 minutes.
9. The method of claim 1 wherein said reinforcing fiber is present at a level of 10.0% (wt.) to 40.0% (wt.).
10. The method of claim 1 wherein said foaming agent produces gas volumes of at least 20 cc/gram.
11. The method of claim 1 wherein said foaming agent produces gas volumes in the range of 20 cc/gram to 100 cc/gram.
12. The method of claim 1 wherein said injection molded part having cellular structure indicates 1.0-50.0 Joule total energy and 0.5 kN to 4.0 kN maximum load according to ISO-6603-2 (April 2019).