Plastics and their resins come in many varieties. Each has its own properties and uses. For instance, High Density Polyethylene (HDPE) is a durable, non-leaching plastic that can endure common temperatures. It’s perfect for milk jugs and things of that nature. Polyvinyl Chloride (PVC) is strong but often contains phthalates which can have a negative impact on life forms, making it great for outdoor furniture but less useful for holding leftovers.
All plastics, however, are developed from resins which—after being melted down—bond together into any number of shapes. Unfortunately for the engineers who take care of this process, it isn’t as easy as just dumping in the little pieces and waiting until fully-formed plastics come out. It is important that the resins be dry (That’s where we come in). There are 4 factors which play a part in the drying of resins.
Are your pellets absorbent?
Although there are many types of plastics, there is an easy way to separate them into two groups. Every plastic falls into one of the following categories: hygroscopic or non-hygroscopic. In simple terms, hygroscopic plastics absorb moisture because water molecules can penetrate it. The polymer chains that form the plastic allow for the moisture to slip inside, and so it does. Water molecules will not enter the chains of non-hygroscopic plastics.
Just because non-hygroscopic plastics do not absorb water does not mean that they do not require drying. Surface moisture may still rest on the outside. Naturally, a pellet with water inside of it will be a more difficult piece to dry, but it can be done.
As far as plastic pellets are concerned, heat is the biggest force behind getting them to let go of the moisture. A hair dryer works in this way. High temperatures cause water molecules to get “excited” and move around. This movement causes the molecules to move further apart and as they do so, the moisture rises to the surface of the pellet.
The temperature of a liquid directly affects its state. When a gas cools, it condenses and becomes liquid. The point at which this occurs is called the dew point. After the pellets are heated, they are cooled to the dew point.
Measuring the dew point allows the user of the dryer to potentially save on energy costs and ensures that the pellets are getting cooled to appropriate temperatures.
The biggest difference between wetting and drying something is probably the time factor. Wetting happens instantly, but drying takes a while. Your pellets aren’t going to become dry immediately. Depending on the level of moisture and types of plastics, it could take hours for your load to dry out.
PolyClean’s drying systems work quickly. In fact, they can dry up to one ton of pellets per hour, if conditions are right!
Just as it’s bad for business, stagnancy is bad for drying plastics. There must be air movement occurring, or else the heated water vapor and cool, condensed water will stay put. Constant air flow guarantees that the water molecules get swept out of holding tank. The result is dry pellets.
We are the mobile, plastic drying experts. We understand what steps to take to dry your specific resins well. If you find yourself in need of onsite plastic solutions, click here to request a quote.