South Africa’s lack of polyethylene engineering plastics suppliers prompted German plastics engineering manufacturer Wefapress to establish a Port Elizabeth-based facility.
In South Africa, the company distributes polyethylene engineering plastics to markets that mainly convert the sheets into finished products and parts.
“We, therefore, refer to our sheets as semifinished products, because the product rarely gets used as is,” says Wefapress South Africa resident agent Olaf Wildemann.
He states that, once a product has been converted into the finished item, it is either used locally or exported to other African countries and used mainly in the mining, bottling and beverage industries.
“The company has been active in South Africa since 2001 and feels it has a social responsibility to give back to the community. Wefapress is involved in numerous charity projects in Port Elizabeth, ranging from donations to the Algoa Bay Rotary Club to a church in one of the local townships,” Wildemann notes.
The company is involved in many industries locally, including cryogenic applications as low as -265 °C and bulk materials handling and dewatering elements in the pulp and paper industry, as well as supplying manufacturers of guides for chains and belts in high-speed-conveying applications and shielding elements in nuclear applications.
“We provide plastics for the engineering of products for the food and beverage and pharmaceutical industries and are also involved in medical-grade orthopedic implants for the pharmaceutical industry,” he says.
Wildemann states that ultrahigh-molecular-weight polyethylene (UHMW-PE) raw material is a powder ranging in particle sizes of 100 µm to 200 µm and is used by the company to manufacture plastics.
“The powdery raw material can be converted in its original state through compression molding, ram extrusion or direct compression molding into shapes such as sheets, boards, rods and profiles,” he states.
The key properties of the powder include high wear resistance, sliding properties and high-impact strength, as well as being chemicals and corrosion resistant.
“Some properties, such as dimensional stability or the homogeneity of physical and mechanical properties, are also associated with conversion methods,” he says.
Wildemann adds that compression molding of UHMW-PE sheets is generally possible between thicknesses of 10 mm and 220 mm, while skiving allows a thinner sheet product.
“The largest presses in the market produce sheets that are 10 200 mm x 1 250 mm, as well as sheets up to 210 mm in thickness; however, limited UHMW-PE resin grades are available.
“The majority of material being used in the industry can be classified into two major groups, which are determined according to molecular weight – either five-million g/mol or nine-million g/mol – according to the Margolis equation used to determine the molecular weight of UHMW-PE,” Wildemann notes.
He adds that major resin producers and chemicals companies predominantly supply these two groups of resin types to converters to produce sheets and profiles, while some speciality UHMW-PE resin types can be considered as a third group.
“As resin producers have evidently been focusing on high-volume output, UHMW-PE converters have long since taken over the job of pulling and pushing for innovation. UHMW-PE can be easily blended with various additives and compounds to improve properties and produce custom-made materials to suit special requirements in applications,” Wildemann says.
He explains that the advantage of UHMW-PE is that this can be done even on lower- volume scales in a cost-effective manner.
“The compression-molding process allows for minimum-order quantities, as low as one sheet of 2 020 mm x 1 010 mm, to be custom-made, instead of tons of material produced in one extrusion run. This creates a vast array of opportunities for improvements and for material to be easily produced for tests and field trials,” concludes Wildemann.