Polymer compositions, articles made from such compositions and methods for molding such compositions

A method for making a polymer composition, the method comprising the steps of:

• (a) providing a first thermoplastic polymer;
• (b) providing a masterbatch composition, the masterbatch composition comprising:
• (i) a second thermoplastic polymer, (ii) a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof;
• and (iii) a fluoropolymer;
• and
• (c) mixing the first thermoplastic polymer and the masterbatch composition to produce a polymer composition, wherein the polymer composition has (i) an apparent melt viscosity of about 200 Pa·s or less at an apparent shear rate of 1,000 s−1 and a temperature of 190° C., and (ii) an apparent melt viscosity of 2,550 Pa·s or less at an apparent shear rate of 20 s−1 and a temperature of 190° C.

A method for molding a polymer composition, the method comprising the steps of:

• (a) providing an apparatus comprising a die and a mold cavity, the mold cavity having an interior surface defining a shape for a molded article;
• (b) providing a polymer composition comprising (i) a thermoplastic polymer;
• (ii) a polymer additive selected from the group consisting of nucleating agents, clarifying agents, and combinations thereof;
• and (iii) a fluoropolymer, wherein the polymer composition has (i) an apparent melt viscosity of about 200 Pa·s or less at an apparent shear rate of 1,000 s−1 and a temperature of 190° C., and (ii) an apparent melt viscosity of 2,550 Pa·s or less at an apparent shear rate of 20 s−1 and a temperature of 190° C.;
• (c) heating the polymer composition to a temperature sufficient to melt the polymer composition so that it may be extruded through the die;
• (d) extruding the molten polymer composition through the die to form a parison;
• (e) capturing the parison in the mold cavity;
• (f) blowing a pressurized fluid into the parison under sufficient pressure to inflate the parison so that it conforms to the interior surface of the mold cavity and produces a molded article;
• (g) allowing the molded article to cool to a temperature at which the polymer composition at least partially solidifies so that the molded article retains its shape;
• and
• (h) removing the molded article from the mold cavity.