Molecularly orientating plastics material

摘要

It is known to form an integral plastics material mesh structure by punching a square or rectangular pattern of holes in a starting material sheet, and then stretching. Particularly when the material is stretched biaxially, irregularities occur across the structure. In order to avoid such irregularities, the strand-forming zones 3,7 are formed with depressions 13,14 with the sheet at ambient temperature, prior to stretching. This is found to greatly improve the regularity, as well as increasing through-put speeds and decreasing power requirements, particularly with polypropylene.