Methods for forming blended films including renewable carbohydrate-based polymeric materials with high blow up ratios and/or narrow die gaps for increased strength

A method for providing increased strength to a blown plastic film, the method comprising:

• blowing a plastic film with a film blowing apparatus, the film being blown from a blend including a first polymeric material and a renewable starch-based polymeric material, wherein the renewable starch-based polymeric material is (i) substantially amorphous, having a crystallinity of no more than 20%, (ii) has a Young's modulus of at least 1.0 GPa, and/or (iii) has a glass transition temperature of 70° C. to 100° C.;
• wherein:
• (A) the film blowing apparatus operates at a high blow-up ratio of at least 2.0 when blowing the plastic film, wherein the high blow-up ratio at least assists in providing the blown plastic film with increased strength;
• and/or
• (B) a die gap of the film blowing apparatus is selected so as to be a narrow die gap of no more than 500 microns, wherein the narrow die gap at least assists in providing the blown plastic film with increased strength;
• wherein the renewable starch-based polymeric material has a density greater than 1.25 g/cm3.