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Water solumble polymer makes its debut

August 23, 2008

2 Min Read
Water solumble polymer makes its debut

Biodegradable polymers on the market today are often made available in film or thermoforming grades for packaging purposes. Ask for an injection molding grade, however, and you?ll typically hear the response, ?We?re working on it.? One manufacturer, Environmental Polymers Group, has set itself apart with a water-soluble and injection moldable polymer called depart. Based on polyvinyl alcohol, the material can be processed on conventional injection molding machinery.

Beyond its ability to dissolve in warm water, this resin melts at higher temperatures than many IM plastics. Melting temperatures for the various formulations being developed for injection molding vary between 185 and 210C. This combination of properties makes the material suitable for lost core molding.

Sources at Environmental Polymers say depart has the potential to provide a core within a mold that can withstand the heat of the incoming resin melt, yet be washed away from the center of the part simply by squirting in a jet of warm water.

Application trials are currently taking place at one major injection molding company to refine the technique. It will likely be used for complex internal structures, such as air intake manifolds, many of which are currently made in two halves and joined together. Being able to manufacture these components as single parts would increase quality, enable greater design complexity, and reduce costs.

Depart pellets are manufactured exclusively by Environmental Polymers at the company?s newly built factory in Irlam, England using a patented extrusion process that overcomes stability problems of previous attempts to make polyvinyl alcohol pellets.

One of the key differences between depart and earlier biodegradable plastics is user-controlled solubility in water. Depending on the grade used, materials can be designed to dissolve at preset temperature ranges centering on, for example, about 20C (70F), 55C (130F), or 80C (175F). After 2 to 20 minutes of immersion at the designated temperature, the depart polymer dissolves in water, leaving a harmless, nontoxic, aqueous solution of polyvinyl alcohol with a small amount of glycerol. Once this comes into contact with microorganisms such as those found in water treatment plants, biodegradation to carbon dioxide and water takes place within about 30 days.

Strength is another key difference between this material and other biodegradables. One grade that becomes fully soluble at 60C has a tensile strength of around 50 to 60 MPa, about three times that of LDPE. Variations of depart have tensile strengths of up to 90 MPa. Initial research has also shown that depart has a very strong resistance to hydrocarbons and other oils and gases.

Environmental Polymers Group, Newark, DE
(302) 366-8764

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