Discrete ManufacturingFree referencePDF, Excel, Word exportPlastics and Injection Molding

Thermoplastic Resin Processing Temperature and Shrinkage Reference

Choosing starting settings for a new resin means knowing its typical melt temperature, mold temperature, drying requirement and shrinkage. This table puts those ranges for common thermoplastics in one searchable place so you can plan a trial or sanity check a setup.

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Resin	Abbreviation	Typical melt temp (F)	Typical mold temp (F)	Typical shrinkage (%)	Drying before molding	Structure
Polypropylene	PP	390-500	70-140	1.0-2.5	Not normally required	Semi-crystalline
High-density polyethylene	HDPE	400-500	60-140	1.5-4.0	Not normally required	Semi-crystalline
Low-density polyethylene	LDPE	330-450	70-110	1.5-5.0	Not normally required	Semi-crystalline
General purpose polystyrene	GPPS	360-480	50-120	0.4-0.7	Not normally required	Amorphous
High-impact polystyrene	HIPS	375-500	50-130	0.4-0.8	Not normally required	Amorphous
Acrylonitrile butadiene styrene	ABS	410-520	100-180	0.4-0.7	About 180 F for 2-4 h	Amorphous
Styrene acrylonitrile	SAN	400-500	100-180	0.3-0.7	About 180 F for 2-3 h	Amorphous
Polycarbonate	PC	520-620	160-220	0.5-0.7	About 250 F for 3-4 h	Amorphous
Polycarbonate / ABS blend	PC/ABS	450-550	120-180	0.5-0.7	About 200-230 F for 3-4 h	Amorphous
Polymethyl methacrylate (acrylic)	PMMA	400-500	120-180	0.2-0.8	About 170-185 F for 3-4 h	Amorphous
Nylon 6	PA6	480-540	150-200	0.7-1.5	About 175 F for 4-6 h (dry as molded)	Semi-crystalline
Nylon 66	PA66	520-570	150-200	0.8-1.5	About 175 F for 4-6 h (dry as molded)	Semi-crystalline
Polybutylene terephthalate	PBT	450-500	120-180	1.2-2.0	About 250 F for 3-4 h	Semi-crystalline
Polyethylene terephthalate	PET	500-550	Varies by grade and goal	1.2-2.0	About 250-300 F for 4-6 h	Semi-crystalline
Acetal copolymer	POM	360-440	120-200	1.8-2.2	Usually not required, check supplier	Semi-crystalline
Thermoplastic polyurethane	TPU	380-430	70-120	0.5-1.5	About 180-200 F for 2-3 h	Elastomer
Modified polyphenylene ether	PPE/PPO	480-600	150-210	0.5-0.7	About 200-220 F for 2-4 h	Amorphous
Polyphenylene sulfide	PPS	580-650	275-325	0.2-1.0	About 300 F for 3 h	Semi-crystalline
Polyether ether ketone	PEEK	700-750	340-400	1.0-1.3	About 300 F for 3 h	Semi-crystalline
Rigid polyvinyl chloride	PVC	340-400	70-120	0.2-0.6	Not normally required, avoid long residence	Amorphous

Values are typical ranges for unfilled general grades and are for planning only. Glass or mineral filled grades shrink less, and fiber orientation makes shrinkage different along and across flow. Always use the resin supplier's datasheet for the exact grade, and validate with a measured sample from your tool.

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How to use these ranges

Find your resin by name or abbreviation and use the ranges as a starting window, not a recipe. Start in the middle of the melt range, set the mold temperature near the recommended value, and adjust from there during the trial. Check the drying column before the material goes near the press, since wet nylon, PC or PET produces splay and loses strength. The datasheet for your specific grade always has the final say, especially for flame retardant, glass filled or high flow grades.

Start mid-range and adjust in small steps
Dry hygroscopic resins before molding, using a desiccant dryer with a dew point check
Record the actual settings in your process sheet for repeat runs

Understanding shrinkage

Shrinkage is the difference between the cavity dimension and the cooled part, expressed as a percent. Semi-crystalline resins such as PP, HDPE, POM and PA shrink more than amorphous resins such as ABS, PC and PS because crystals pack more densely as they form. Shrinkage also rises with thicker walls, higher mold temperature and lower pack pressure, and varies with direction when fibers or flow orientation are present. Mold designers use the shrinkage value to size the cavity: cavity size is roughly part size divided by (1 minus shrinkage).

Amorphous versus semi-crystalline

Amorphous resins soften gradually and are generally dimensionally stable with lower shrinkage. Semi-crystalline resins melt sharply, need enough heat to form crystals, and tend to be tougher and more chemically resistant but more prone to warpage. The distinction also affects mold temperature: higher mold temperature raises crystallinity, improves surface and stability, but lengthens cooling. Use the Structure column to remind yourself which behavior to expect.

Common mistakes

Typical errors include using one shrinkage value for every direction and wall thickness, skipping drying because the bag looks sealed, and running the barrel at the top of the range with a long residence time. Degraded resin shows up as splay, black specks or brittle parts. Match shot size to barrel capacity so material does not sit too long, and purge when you change resins with incompatible temperature ranges.

Frequently Asked Questions

Are these values exact for my resin grade?

No. They are typical ranges for general unfilled grades. Filled, flame retardant and high-flow grades differ. Use the supplier datasheet for the exact melt temperature, mold temperature, drying and shrinkage of your grade.

Why do semi-crystalline resins shrink more?

As they cool, molecules arrange into crystals that pack more densely than the amorphous melt, which reduces volume. Amorphous resins lack this ordered structure, so they shrink less and are generally more stable.

Do I need to dry polypropylene?

Normally no. PP absorbs very little moisture. Hygroscopic resins like nylon, PC, PET, PBT and ABS do need drying. If the supplier states a moisture limit, measure it rather than guessing.

How do I calculate cavity size from shrinkage?

A common approximation is cavity dimension equals part dimension divided by (1 minus shrinkage as a fraction). For a 100 mm part with 1.5 percent shrinkage, the cavity is about 101.52 mm. Validate with a measured trial because real shrinkage depends on process.

If you track resin lots, dryer settings and process parameters in your ERP or MES, Netray can help you connect them to scrap and quality results on-premises.

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