Processing guides: SABIC® PP and SABIC® PPCompound injection molding
SABIC® PP and SABIC® PPCompound materials can be processed using a wide range of processing parameters, see summary of processing conditions below and explained overleaf:
Safety
Information on the safety aspects of all SABIC® PP, SABIC® PPcompound and SABIC® PP CS grades is provided in the relevant Material Safety Data Sheets.
Pre-drying
Material is delivered in silos, octabins or bags. Regarding SABIC®PP: When stored in a cold place, allow material to slowly reach room temperature before opening the package. When condensation is visible or can be expected, drying is recommended (2 hours at T= 80 - 100 °C). For aesthetical parts pre-drying is recommended. Regarding SABIC® PPcompounds: Although not always necessary, predrying (2 to 4 hours at 80 to 100ºC) is recommended.
Equipment
SABIC® PP, SABIC® PPcompound and SABIC® PP CS grades can be processed on all modern injection molding machines with screw plasticizing. Both core progressive and three-zone screws can be used. L/D ratios of >20 and compression ratios of 1:2.0 to 1:2.8 are recommended.
Melt temperature - cylinder settings
Increasing barrel temperature profiles are most commonly used. In case of high-throughput screws or large shot volumes, a flat or even reversed temperature profile may also be used. Melt temperatures can range from 210 to 270 degrees, depending on MFI of the material, flow lengths and part thickness. For applications where odour is important, low melt temperatures are preferable.
To improve the transport of the granules the temperature of the cooled zone should not be too high; preferred temperature in the feed block 30 - 60°C.
Mold temperature
Although a broad window is possible, low tool temperatures of 15 to 20ºC in general yield faster cycle times. For surface aspect, texture clarity or mould filling purposes it might be necessary to go to higher temperatures of 50 to 60ºC. Average temperatures of around 30ºC are widely used in the industry.
Pressures
With well designed injection systems the effective injection-pressure is generally no more than 1.200 Bar. In this case the mold-pressure is about 250 to 600 Bar. The holding-pressure should generally be set to between 40 and 70 % of the maximum injection-pressure. The effective back-pressure should be between 100 and 150 bar.
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