| 摘要 |
A polypropylene strap for use in packaging articles. The polypropylene strap has a high tensile strength, a low elongation, a high rigidity, a high abrasion resistance, and flexible surfaces, and it is not easily split in the longitudinal direction. This strap has superficial layers stretched at a low draw rate of 1.2-3, and an inner portion stretched at a high draw rate of 10-18. The total thickness of the superficial layers is 5-50% of the total thickness of the strap. The strap is manufactured by stretching a belt-like material, which has been extruded from a die, in the lengthwise direction thereof at a volume ratio of 4-9, heating the surfaces of the resulting belt-like material to put the molecular chains in the superficial layers only thereof in a non-oriented state, and then stretching the belt-like material as a whole at a draw ratio of 1.2-3. |
