EuroWire September 2020

Technology News

The rod PDH dry coating and wire lubrication system is improving the current state of rod preparation and wire drawing, enabling process users achieve cost savings in production of drawn wire, including spring wire, PC strand wire, plating wire, cold-heading wire and CO 2 welding wire. The PDH system enhances wire drawing performance by eliminating issues related to friction heat, benefiting from the fully controlled and sensitive five-way interaction between the five most important lubrication parameters, including lubricant pressure being steplessly adjustable up to 350 bar (5,000 psi), lubricant viscosity, thermal stability, lubricant melting temperature and lubricant full film thickness. All of these variables are continuously and automatically controlled, all communicating together, creating a high- performance residual dry coat that reduces die wear to an unmeasurable level (around 0.2 micron per tonne of drawn wire), so burnt lubricant issues and rapid die wear are eliminated. The PDH rod dry coating creates a full-film anti-friction conversion coating, performed at zero energy consumption, with zero consumables or maintenance cost, that is claimed to perform comparably to, or better than, zinc phosphate or other in-line wet pre-coating chemicals. This generates cost saving in the production of quality wire. Rod PDH dry coating

Applications include all carbon wires up to 0.98% carbon, mechanically descaled or acid cleaned, coated or uncoated, drawn at high speed. Decalub www.decalub.com ▲ ▲ Wire rod coating and lubrication by PDH system

Extrusion screw and barrel package withstands fluoropolymer corrosion

Other design specifications for screws to process these fluoropolymers involve the length of the feed and transition sections of the screw and the compression ratio. “While there is growing demand for fluoropolymers in wire and cable because of their extreme heat and chemical resistance, these materials do require plasticating systems that resist corrosion,” said Walter Smith, senior extrusion application engineer. “In consultation with customers in the wire and cable industry, we have designed package systems for FEP and PVDF that meet this requirement, as well as addressing the special processing characteristics of each engineers, manufactures and markets products and systems for the precision dispensing of adhesives, coatings, sealants, biomaterials, polymers, plastics and other materials, fluid management, test and inspection, UV curing and plasma surface treatment. The company serves a wide variety of consumer non-durable, durable and technology end markets, including packaging, non-wovens, electronics, medical, appliances, energy, transportation, construction, and general product assembly and finishing. Nordson Polymer Processing Systems provides engineered components to melt, homogenise, filter, meter and give shape to plastic and fluid coating materials. Nordson Corp www.nordson.com polymer.” Nordson Corporation

Custom-designed Xaloy® screw and barrel packages from Nordson Corporation can withstand the corrosive effects of fluoropolymers in the extrusion of insulation for wire and cable, while meeting the processing requirements of materials as different as fluorinated ethylene-propylene (FEP) and polyvinylidene fluoride (PVDF). Fluoropolymers are among the most corrosive materials for processing in standard extrusion systems. The screw and barrel packages now offered by Nordson include highly corrosion-resistant materials for all components, along with custom-designed screws to meet the differing processing temperatures of FEP and PVDF, and the special mixing requirements of the individual customer. The corrosion-resistant materials speci- fied for FEP screws include Inconel® nickel-chromium alloys for the base metal and Colmonoy® nickel-based alloys for the hard-surfacing that is welded onto the wear surfaces, or lands, of the screw flights. For PVDF

screws, the recommended base metal is chrome-plated 4140 HT alloy steel or stainless steel. The barrel that Nordson recommends for use with both screws is lined with Xaloy X-800, a highly corrosion- and abrasion-resistant nickel-based alloy with tungsten carbide; for discharge flanges and feed ports, the material is Inconel. An important difference between the two fluoropolymers is melt temperature: 230 to 290°C for PVDF, versus 360 to 380°C for FEP. This is a determinant of screw design for applications requiring mixing of the polymer with additives, modifiers and colourants. For FEP, Nordson recommends a screw with the Xaloy Stratablend II mixer, which provides both distributive and dispersive mixing with relatively low shear. This is also recommended for mixing PVDF, but in addition Nordson specifies the Xaloy Efficient™ barrier screw. The barrier screw design separates the already-melting resin from solid material that has yet to melt, preventing over-shearing of the melted PVDF and keeping the melt temperature of the overall extrudate low.

▼ ▼ Xaloy Efficient screw with Stratablend II

▼ ▼ Xaloy Stratablend II extrusion screw

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September 2020