PDA

View Full Version : How long does material stay dry?


Cliff
10th May 2016, 06:33 PM
What is the typical time for material to remain "dry"? I know there are many variables, including material compound, ambient temperature and humidity, but are there are rules of thumb for the common materials like ABS and PC?

I'm in SoCal, but not near the beach, so we get the full range of extremes--humidity in the morning can be 99% (June gloom) or 2% in fire season. Obviously, early morning are the most humid, but based on an average 40%, is there a rule of thumb, or should I dry material every single day?

Also, is there a way to store small quantities (like 10lbs) of dried resin to keep it dry longer? Will large ziplocs help, or will the moisture travel through the bags?

Thanks,

Cliff
brentb
11th May 2016, 01:37 PM
Each resin has unique absorption rates and %. Bags will help. Critical jobs should have moisture analyzed.


KOM

brent
JayDub
11th May 2016, 04:34 PM
Depending on the resin and your situation:

Some resins will tolerate prolonged storage in the drier at operating temperature.
Some resins will tolerate prolonged storage in the drier at a reduced temperature.
Commercially available vacuum chamber
Home-made dry box with an inert atmosphere (dry nitrogen)

I have used moisture-proof (Mylar?) bags, sealed with a bag-sealer, but for prolonged storage we kept those under vacuum anyway.
Jendalf
16th May 2016, 06:52 AM
Hi,
As colleagues said: depends on the material characteristics. You can rely here on the producers recomandations.

Question "How long does material stay dry?" isnīt completely good bc this depends on You :)

Ususally use for basics 85°C 4 hours - if You calculate constant flow out of dryer. This conditions are enough to reduce the physicaly bonded water out of granulate.
Cons are that If you donīt have the output You can during longer period cause the thermodegradation of some materials.

This fits ok for working storage = The material for direct production.

For longer storage - just avoid the material to be poluted by external influence of weather. For production You have to pre-dry almost in every cases.

j.