This information should only be used as a quick reference. Users should always refer to the processing data sheets provided by the material supplier. Differential shrinkages are not considered.
|Material||Shrinkage %||Post Shrinkage Dimension|
|Nylon 6 (30% GF)||0.4|
|Nylon 6/6 (33% GF)||0.5|
|PET (semi crystalline)||0.4|
|Polypropylene (30% talc filled)||1|
|Polypropylene (30% GF)||0.5|
|Polystyrene (30% GF)||0.1|
|SAN (30% GF)||0.1|
Plastic moulding shrinkage is the contraction of a plastic moulding as it cools after injection. Most shrinkage occurs in the mould during cooling, but some shrinkage occurs after ejection, as the part continues to cool. After that, the part may continue to shrink very slightly for several hours or even days until the temperature and moisture content stabilise.
All polymers have different shrink rates depending on many factors. These include amorphous or crystalline materials, cycle times, temperatures, mould design, part shape and wall thickness.
Our chart shows typical shrinkage ratios for the list of materials
Many pigments operate as nucleating additives, which may cause shrinkage to grow in some plastics. Similarly, the shrinkage of polymers containing fillers and fibres in composite materials may differ from those of virgin polymers, with potential for significantly different thermal expansion coefficients. The direction in which fibres align can also become a factor, as shrinking may occur less in one direction, than in the other.
There are several well-defined and standardised approaches to determine the shrinkage of plastic parts. The most internationally used and recognised approaches are:
This information should be used as an 'on the spot' reference only. Users should always follow the material suppliers processing data sheets. The data is provided “as is” and without any representation or warranty of any kind, including that it is fit for any purpose or of merchantable quality, or functions as intended or at all. Your use of this data is entirely at your own risk and PlastikCity accepts no liability of any kind.
At CJP we pride ourselves on our excellent customer service. All our staff are trained to a high standard and can offer you technical advice.
Nothing is too much trouble; no enquiry is too big or too small!
Our products by category
Use the below buttons to access product overviews, applications & downloads.