Hygroscopic Material

[MIOMY]

Howdy Folks, just wondering if anyone has done moisture analysis comparing hygroscopic resin from " vacuum sealed bags" versus desicant dryer ? I myself am not convinced that processing from a bag is a good practice.

Thank you for any input

Ron

[brentb]

Done that and found the resin within the resin maker's specs, but put it in the dryer anyway. Didn't want to give the impression that it was an acceptable practice not to dry the resin. I therefore agree with you.
Are those bags truly vacuum sealed or a multi- layered foil? Are they evacuated with nitrogen?

In the "old days" nylon was in large cans, and you opened a can as needed and didn't dry. That was in the days of booster timers and relay logic though. Molding was an art rather than a science.
KOM

brent

PS: I am going to go read some bags!

[pjhall]

Dry it! Cut the bag open and put the material into a moisture analyzer if you have one and you will find that it is not dry. put it in your hopper and it will soon just absorb ambient moisture. "Hydroscopic" btw. This is especially true with thermoplastic polyurethanes such as Isoplast from Dow. Even out of the vacuum sealed bag they need 6-12 hrs drying depending on the brand of dryer.

[Suhas]

Those are interesting comments. I wonder if we could get a material supplier to answer here. I always thought it was OK since I am sure they go through great lengths to vacuum pack the material.
Ron, do you have a moisture analyzer? May be you can do the test and post the results here. Open the bag, right away do a moisture test. Then dry it and do another moisture test.
Here is a caution for Nylon: Nylon needs to have moisture in it during processing. Moisture is a viscosity regulator. Typical content needs to be between 0.15 - 0.20 %.
Regards,
Suhas

[MIOMY]

Thank you for the responses fellas ! The bags are vacuum sealed I would say Brent, when pulled off the skid the bag stays rigid like it was bagged too hot and solidified. I don't deal in the paper shuffling but will do some inquiring. It is my boss who has no problem going with the belief its ok, and maybe because we don't have enough dryers ... " they are being ordered" I am with you pjhall, better safe than sorry is my way of thinking. As a matter of fact Suhas we do, it sits in the QC office collecting dust ... it is nylon I am referring to, so I will see if the analyzer is operational and I will post my findings, and yes not common knowledge that it is possible to "overdry" certain resins or when living in the climate of canada that nylon stored in outdoor silos must be brought indoors and brought to indoor ambient temp (minimum 2 days) before being put into dryer ... saturates your dessicants.

" If it can happen ... it will "

Ron

[rickbatey]

Dry it! Cut the bag open and put the material into a moisture analyzer if you have one and you will find that it is not dry. put it in your hopper and it will soon just absorb ambient moisture. "Hydroscopic" btw. This is especially true with thermoplastic polyurethanes such as Isoplast from Dow. Even out of the vacuum sealed bag they need 6-12 hrs drying depending on the brand of dryer.
PJ- the correct term is hygroscopic. Hydroscope is used for viewing objects underwater.
Sorry the OCD just kicked in.
I've run nylon without drying when it was vacuum sealed, the press would use the bag in an hour or so, and we had no desiccant driers.
Rick.

[MIOMY]

And the correct spelling is desiccant ... ! Thank you Rick, my OCD wasn't working yesterday : )

Ron

[brentb]

Then there are hydrophilic resins

KOM
brent

[pjhall]

PJ- the correct term is hygroscopic. Hydroscope is used for viewing objects underwater.
Sorry the OCD just kicked in.
I've run nylon without drying when it was vacuum sealed, the press would use the bag in an hour or so, and we had no desiccant driers.
Rick.

Yep my bad.

[MIOMY]

Bear with me fellas' ... I will get to this when time permits ... so much to do in so little time ... new job ... WAAAAY out of control lol ... job security : )

Ron

[Ashley]

Make sure the analyzer is a moisture analyzer and not a loss on weight analyzer as you will get a more valid result. Vapor Pro is a pretty good one and I think the best is a Karl Fischer (sp*).

Nylon is a broad term. there are several nylons and 4/6 needs to be .02%(I think) or less for processing. make sure you get the data sheet for the material you are running. not just a generic nylon number.

I would put it in a dryer. (my opinion)