Fluids Offer Rotomolder, Blowmolder Process Advantages
September 1, 2006
A company rotomolding soft plastic automotive dashboards needed the ability to cycle the process from forming temperature down to ambient in a controlled fashion, to maintain finished-product quality. Such an act of slush molding might customarily take place in an oven chamber, heated by gas or electricity, and cooled by rapid removal of the entire rotational apparatus from the chamber, combined with some sort of forced-air blasting.
Recently, a new process was engineered to use indirect heat to accomplish the temperature-driven quick forming and controlled curing. A single thermal fluid capable of both heating and cooling, manufactured by Paratherm Corp., West Conshohocken, Pa., is circulated to the mold through high-performance universal joints while the whole apparatus spins in two axes. Paratherm MR mid-range heat transfer fluid is rated for service from 30 to 550°F (-1 to 288°C).
A different processor needed a fluid with similar capabilities. This blowmolder of plastic bottles needed to offer their customers the highest level of confidence in the safety and non-toxic integrity of the end-product -- containers offered for beverage and food ingredient service. The fluid needed to be registered as food-grade with the appropriate agencies to give food ingredient and beverage packagers assurance that all process components and auxiliaries that might contact the polyethylene end product would be as benign as possible. Technically, the operator needed a fluid with the ability to heat and maintain the molds to an application temperature around 300°F (149°C) in some short runs. Yet, in other short runs with resins having lower meltpoints, the mold temperature would need to be maintained at much lower temperatures than could normally be handled with water-capable equipment. This processor required a single fluid and setup for both temperature profiles, and he found it in Paratherm MG. The food grade (NSF certified) heat transfer fluid is for single-fluid heating and cooling from 30 to 500°F (-1 to 260°C).