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Resin Drying Time and Temperature Reference

Wet resin is a leading cause of splay, voids, brittle parts and unstable viscosity in molding. This table gives typical drying temperatures, times and moisture limits for the resins molders run most, so a setter can check the dryer settings quickly.

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Resin	Abbreviation	Typical drying temperature (deg C)	Typical drying time (hours)	Typical max moisture before molding	Note
Acrylonitrile butadiene styrene	ABS	80 to 85	2 to 4	about 0.1 percent	Moisture causes splay and silver streaks
Styrene acrylonitrile	SAN	80	2 to 3	about 0.1 percent	Slightly hygroscopic
Polycarbonate	PC	120	3 to 4	about 0.02 percent	Wet PC hydrolyzes and loses impact strength
PC/ABS blend	PC/ABS	90 to 100	3 to 4	about 0.04 percent	Follow the supplier grade sheet
Polymethyl methacrylate (acrylic)	PMMA	80	3 to 4	about 0.04 percent	Bubbles and haze when wet
Polyamide 6	PA6	80	4 to 6	about 0.2 percent	Dry in a desiccant dryer; absorbs moisture from air
Polyamide 66	PA66	80	4 to 6	about 0.2 percent	Glass-filled grades dry the same way
Polyamide 12	PA12	80	3 to 4	about 0.1 percent	Lower moisture uptake than PA6 and PA66
Polybutylene terephthalate	PBT	120	3 to 4	about 0.02 percent	Hydrolysis sensitive
Polyethylene terephthalate	PET	150 to 160	4 to 6	about 0.005 percent	Needs low dew point and tight moisture control
Glycol modified PET	PETG	65	4	about 0.04 percent	Dries at lower temperature to avoid pellet sticking
Modified polyphenylene ether	mPPE	100	2 to 3	about 0.05 percent	Check grade data
Polysulfone	PSU	135	3 to 4	about 0.05 percent	High temperature dryer required
Polyetherimide	PEI	150	4	about 0.02 percent	High temperature dryer required
Polyphenylene sulfide	PPS	130 to 150	3	about 0.02 percent	Pre-drying recommended on filled grades
Polyether ether ketone	PEEK	150	3	about 0.02 percent	Use dryer rated for the temperature
Liquid crystal polymer	LCP	150	4	about 0.01 percent	Follow supplier data closely
Thermoplastic polyurethane	TPU	80 to 90	2 to 3	about 0.02 percent	Very moisture sensitive; use desiccant dryer
Polylactic acid	PLA	60	4	about 0.025 percent	Dry well below glass transition to avoid sticking
Cellulose acetate butyrate	CAB	70 to 80	2 to 3	about 0.1 percent	Hygroscopic cellulosics
Polyoxymethylene (acetal)	POM	80 to 100	2	about 0.1 percent	Often run undried; dry if stored in humid areas
Polypropylene	PP	Not normally required	n/a	negligible	Dry only if surface moisture from condensation
High density polyethylene	HDPE	Not normally required	n/a	negligible	Keep material out of cold-to-warm condensation
Polystyrene (general purpose)	GPPS	Not normally required	n/a	negligible	Dry only if wet from condensation

These are typical industry ranges for planning. Always follow the resin supplier's data sheet for the exact grade, especially for filled, flame-retardant or colored compounds. Use a desiccant dryer with a dew point near minus 40 deg C for hygroscopic resins and count drying time from the moment the material reaches the set temperature.

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How to use the table

Search by resin name or abbreviation, then compare the dryer settings with the ones on the hopper dryer. Values are typical figures, and a filled, colored or flame-retardant grade can differ, so confirm with the grade data sheet before changing a validated process. You can export the table to Excel for a laminated cheat sheet at the press, or to add to your standard work instructions.

Why some resins need drying

Hygroscopic resins such as nylons, polycarbonate, PET, PBT, TPU and many blends take up water from the air. At melt temperature that water reacts with the polymer, a process called hydrolysis in polyesters, polycarbonate and polyamides, and cuts molecular weight, so the part loses strength even if it looks fine. Surface moisture also vaporizes and causes splay and bubbles. Non-polar polyolefins and polystyrene absorb almost nothing, so they are usually only dried if condensation forms on cold pellets.

Dryer setup and checks

Time is counted once the resin has reached drying temperature, so a cold hopper load needs extra time. Match hopper capacity to throughput so material is not under- or over-dried; most dryer sizing guides use roughly a pound of material per hour times the drying hours for the hopper size. Check the dew point of the return air, filter and desiccant condition, hoses and sealing. A moisture analyzer on the dried pellets gives a direct check of the moisture content before molding.

Check dew point near minus 40 deg C for hygroscopic resins.
Do not open the hopper lid for long periods.
Insulate hoses and keep them short.
Do not mix different resins in one dryer.

Common mistakes

Over-drying certain materials can cause oxidation or yellowing, and drying PET or PETG above the right temperature makes pellets stick together. Using the same program for every grade, drying regrind with the wrong settings, and leaving dried material exposed on the floor all bring moisture back. Remember that glass-filled grades are dried like the base resin, and that colorant or additive masterbatch with a hygroscopic carrier needs drying too.

Frequently Asked Questions

How long should nylon be dried before injection molding?

Typically around 80 deg C for 4 to 6 hours in a desiccant dryer, to bring moisture below about 0.2 percent. Check the grade sheet because glass-filled and specialty grades vary.

Do I need to dry polycarbonate?

Yes. Polycarbonate is moisture sensitive and typically needs about 3 to 4 hours at around 120 deg C, with a target moisture below roughly 0.02 percent, to avoid hydrolysis and splay.

Can I skip drying for polypropylene?

Usually yes, because PP absorbs very little moisture. Dry or warm it only if pellets show condensation after being brought from a cold area into a warm one.

What dew point should the dryer have?

A desiccant dryer used for hygroscopic engineering resins is normally run with return-air dew point near minus 40 deg C or lower. PET often requires lower.

If you want moisture and drying parameters to appear on production orders from your ERP or MES, we can help configure that.

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