The humidity is a drag

Sitting on the deck, the view of the lake is great, but the feeling is uncomfortable, why? The dew point is 74! Humidity has me sweating while just sitting still.

That feeling also brings me to think of………. the production floor.

Am I crazy? No, not if you understand what humidity does to an injection molding provider.

There are two major classifications of polymers/plastics resins, hygroscopic and non-hygroscopic.

Hygroscopic resins have a strong affinity to attract moisture and absorb it when exposed to ambient air. Hygroscopic polymers include nylon, ABS, acrylic, PET, PBT, polyurethane, polycarbonate, and others, (the main resins and engineered resins used for structural/component manufacturing).

Non-hygroscopic (hydrophobic) resins used to make plastic products do not have such an attraction to moisture. Non-hygroscopic polymers include PVC, polypropylene, polystyrene, polyethylene, and more, (the main resins used in packaging applications).

Why do molders care if the resin absorbs moisture? Too much moisture present when plastic resin is molded will cause product defects. Common defects caused when the resin has been under-dried include sink marks or voids, cloudiness, splay, streaks, air bubbles on the product’s surface, and unplanned shrinkage.

Resin manufacturers and compounders recommend the drying time and temperature for drying their resin. It is based on a resin’s assumed initial moisture content level and detailed in the provided technical data. That DOES NOT consider places like Minnesota, where humidity is low in the winter, and through the roof in some periods over the summer.

So, the amount of time it should take to dry resin is determined considering the actual wetness of the resin vs a standard time in the data sheet.

In the past, a molder would use those data sheet numbers, and adjust based upon experience. We would rely on the PM of the dryer and look for any evidence of over or under drying while processing the resin into components.

In today’s world, an analyzer will provide you the information necessary to know dryness levels before you start processing. PlastiCert uses an analyzer, your molder should too.

                               

Does your molder mold primarily the structural base and compounded resins, or are they more into the packaging resins?

Does your molder reside in a humidity susceptible region?

Do they have a controlled environment for STORAGE and processing?

Do they utilize an analyzer to know where they are BEFORE they start processing?

If you are uncomfortable with the answer to any of these questions, give us a call. We have been on top of humidity for many years,

Except for the deck with the view, there, we have to endure humidity just like everyone else.