Clear PP bottle from Injection Stretch Blow Moulding (ISBM) process could be a new business opportunity

Indian Plastics Institute conducted a seminar on the 12th of December 2001 at Mumbai to discuss and assess the business opportunity for Injection Stretch blow moulding of PP.

PP, the largest commodity thermoplastics has an insignificant presence in bottle/container applications so far. HDPE commands the lion share of the plastics bottle business. It, however, cannot be used in clear bottles due to its opacity. PET is the choice for clear containers. PET, however, has some limitations in areas where bottles are required to be sterilized at higher temperatures like 121°C or where products are required to be filled in bottles at higher temperatures. PP, due to its higher temperature resistance can certainly be used for such applications. Infact, PP clear containers have been used for pharmaceutical products on account of sterilization requirements or for jams/jellies that are required to be hotfilled. This has been possible because of developments in the ISBM process, as well as in the grades of PP with inherent good clarity (clarified PP random copolymers). ISBM has also been developed for PET. PP due to its semi-crystallinity has a sharp reduction of tensile properties at higher temperatures. To achieve uniform blowing, very closer temperature window (of about 50°C) near its crystallization temperature is required in case of PP. PP also requires thicker preforms because it requires higher orientation than PET. The higher demand of heat along with poorer thermal conductivity necessitates excellent heating arrangements in the process. Aoki and Nissie, both japanese equipment suppliers, have now developed special single stage ISBM for PP. Husky and Sidel have developed two stage ISBM for PP bottles.

To achieve clarity in bottles random PP copolymer with the latest generation clarifier is required. The material also requires good flow characteristics. The single stage ISBM process requires MFI of atleast 10 (preferably between 12-20) while the two stage ISBM process needs grades with even better flow characteristics (preferably between 25-30)

With the easy availability of machinery and material, clear PP containers containly could be a good business opportunity.