Seyyede Mehrane Hosseini Veleshkolaei - Research & Development Department, Tabarestan Plastic Co., sari, Iran,
Barmak Ghanbarpour Jouybari - Production Department, Tabarestan Plastic Co.,Sari, Iran,
Seyyed Sadegh Sahraei Jamallodinkolaei - Technical Department, Tabarestan Plastic Co. Sari, Iran,

Hollow plastic parts can be made by a large number of manufacturing method, but rotational molding offers the ability to create one-piece, stress-free parts with attractiveeconomics and is specially suited for making article with complicated geometrics and excellent detail reproduction. Inthis process the product is formed inside a closed mold or cavity, while the mold is rotated biaxially. The fundamental nature of rotational molding is such that low-pressure process,relatively high temperature and long cycle time. however, a drawback of this process has always been the surface pinholes which occure in the products due to air trapping between mold surface and polymer in sintering step and don◌ t exist requirement driving force for removal of air bubble