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Semi-Conductive Polyethylenes for Rotational Molding

Rotec’s new ICORENEä semi-conductive polyethylene advances materials technology by offering designers and rotational molders a method for producing static-free parts for hazardous and other sensitive environments. Traditional methods for achieving low levels of anti-static performance have been unsatisfactory. Either high levels of carbon black have been incorporated via dry blending or melt compounding, or anti-static additives have been utilized. Both methods are inadequate because:

1. High levels of carbon black severely reduce the properties of the base resin into which they are incorporated.
2. High levels of carbon black severely affect the processability of the resin, resulting in poor melt flow characteristics and poor mold fill.
3. Anti-static additives perform for a limited period; their effect usually disappears after 6 months when the additive has completely ‘bled through’ the polymer.

Rotec has developed ICORENEä semi-conductive polymers to provide a conductive black compound that can eliminate these problems. With ICORENEä , the processability and base resin properties are largely preserved, thus providing molded parts with good mechanical properties, and the semi-conductivity continues for the life of the part.

Conductivity tests were performed by an independent laboratory to evaluate the anti-static qualities of ICORENEä drums and lids. The test results showed that, in terms of conductivity, the samples were considered equivalent to the same items constructed in metal but had a lower electrostatic hazard potential, as they did not generate a spark.

Several rotomolders have successfully used ICORENEä semi-conductive polymers to reduce static in sensitive environments. Gregstrom Corporation of Woburn, Massachusetts, for example, utilizes ICORENEä polymer in a rotationally molded air nozzle. By using ICORENEä , Gregstrom can counter the risk of generating sparks as a result of the high volume of air used in cleaning large tanks that can contain potentially explosive or otherwise dangerous fumes.

Prime Time Products, a Brawley, California rotomolder, molded motor housings from ICORENEä semi-conductive resin. Prime Time Products worked closely with Ramfan Corporation, which developed a line of specialty navy pumps and blowers. These small, portable blower housings, traditionally made of sheetmetal, can be found where confined spaces must be entered and ventilation is required. In many instances these areas may contain potentially hazardous or even explosive mixtures, which must be vented prior to entry. Ramfan took advantage of the conductive properties of ICORENEä by developing a blower housing that maintains the conductive nature of the sheetmetal predecessor while providing the well-known ruggedness and durability of polyethylene casting. In this application the conductive qualities of the material safely conduct any build-up of static charge through the housing to the electrical grounding system, helping ensure that a static discharge does not occur and inadvertently ignite the gases being extracted through the blower.

In addition to these proven uses, the anti-static properties of ICORENEä present many new opportunities for high value, rotationally-molded products. Potential applications include electronic handling and packaging, electronic and motor housings, specialty filters, photosensitive areas, mining, flammable liquids and solvents, and materials handling containers for numerous types of static sensitive environments.

For further information, contact Charlie Busceme at Wedco, Inc.

Phone: 409-752-5330, Fax: 409-752-3391, e-mail: [email protected]

Einar Voldner at Synergy Polymers Inc.

Phone: 905-876-1477, Fax: 905-876-0852, e-mail: [email protected]

Rotational Molding “Shuttle” is Launched

A laboratory-size rotational molder has been designed for research, materials development, color matching, and teaching the roto process.  Dubbed the “Shuttle”, the smallest machine measures 3 1/2 ft deep, 7 ft long, and 5 ft high.  Two larger standard lab. machines are available.

The compact Shuttle reportedly duplicates the molding conditions of a large production rotational molding machine.  The shuttle-style machine features a gas fired oven with high-velocity recirculated air.  Its cooling chamber uses cooling air and water spray to duplicate the cooling cycle of a production machine.

Standard Shuttle features include reverse rotation, variable speed, and inert gas injection.  It also has a control panel with a touch-sensitive display screen.  An RS232 port, allowing downloading of all the processing parameters, is standard.

The standard SHUTTLE is designed for a maximum mold size of 12x12x12 inches, with a Rotolog or drop box attached.  Custom machines of any size are available.

For more information, please contact Bruce Muller, Plastics Consulting, Inc., 682 SW Falcon Street, Palm City, FL 34990, USA.  Ph: (561)781-6699, Fax: (561)781-6667, E-mail: [email protected]