LSR is star of the show

Nuremberg, Germany —​ As an elastomer sector with relatively high growth, LSR understandably had a significant presence with processing, machinery and materials producers among the 297 exhibitors at the July DKT Deutsche Kautschuk Tagung (German Rubber Conference) in Nuremberg.

Lossburg, Germany-based injection molding machinery producer Arburg GmbH + Co KG ran a live demonstration involving two-component molding of a 30 percent glass-fiber-reinforced polybutylene terephthalate primary and a Shore 70A hardness LSR secondary component. The component was for an automotive air conditioning vent.

Eight such parts were molded witha 40-second cycle time on an 800-metric- ton clamping force Allrounder 470A-1000 machine fitted with an 8+8-cavity rotating index plate mold. A size 70 injection unit premolded the 0.38-gram GF30-PBT primary component prior to index plate rotation to allow a secondary external piston type injection unit part mounted on the mold to overmold the LSR secondary component.

Arburg LSR technical specialist Thomas Siegel said cartridge dosing of premixed LSR was used "as this permits even the smallest shot weights to be precisely achieved."

Neustadt-Fernthal, Germany-based Dr. Boy GmbH & Co. KG used its 10-tonne clamping force XS injection molding machines equipped with a new high-precision, 8-mm-diameter screw and piston action LSR plasticizing unit to produce small 0.06 cm3 sealing rings in a mold from Nassau, Germany-based Emde Industrie-Technik GmbH, which equipped the mold with a backflow valve and microvalve gate nozzle.

Emde fitted the mold cavities with transparent windows, which enabled cross-linking of the LSR to be initiated and completed in the mold at low temperature by UV light radiation.

Boy application technology manager Michael Kleinebrahm said the fast in-mold curing with UV not only facilitates applications with long flow channels and thin-wall moldings, but also opens opportunities to use temperature-sensitive additives in LSR formulations.

The UNIpace polymer application center at Kassel University focused its DKT 2018 booth on molding physically foamed Silastic LTC 9400-50 from Dow Silicones grade of LSR into ear plugs in a mold developed by UNIpace mounted on an injection molding machine from Babyplast Christmann Kunststofftechnik GmbH.

The process involves mixing LSR with Expancel expandable thermoplastic microspheres from Akzo Nobel Pulp & Performance Chemicals AB in Stockviksverken, Sweden. The spheres then expand in the mold as the LSR cures at high temperature, the resulting foam structure cutting weight by 50 percent over compact LSR.

Akzo Nobel refers to Expancel as a blowing agent and filler in one that can expand up to 60 times, pointing out that the spheres consist of a hydrocarbon gas encapsulated by thermoplastic that softens under heat, allowing the gas to expand. Under heat, for example, a 4 µm microsphere with a 2-µm-thick shell expands to a 40 µm sphere with the shell thickness reduced to 0.1 µm, density dropping from 1,200 g/m3 to 30 kg/m3.

Öftering, Austria-based LSR mold maker, dosing equipment producer and processor Elmet GmbH had its new TOP 5000P dosing equipment running on the stand of Schwertberg based Engel Austria GmbH. Elmet said it was proud that the unit at DKT 2018 used a OPC-UA Open Platform interface for real-time communication between Engel's injection machine and the LSR dosing system, claiming to be the first dosing equipment producer to provide this facility.

Elmet also supplied the four-cavity mold used for the demonstration on the Engel booth, molding LSR seals for respiratory masks in a Dow Silicones LSR material on a 100-tonne clamping force all-electric drive e-Mac 170/100 injection molding machine with an in lsrtegrated Engel Viper 12 linear robot. All peripheral LSR processes were integrated within the e-Mac's CC300 control unit, allowing the complete process to be set and controlled from its operating panel.

Use of the iQ weight control within Engel's Inject 4.0 intelligent assistance systems ensured precise flash- and reject-free molding with fast cycle time and low energy consumption, irrespective of varying ambient conditions and raw material fluctuation, by monitoring and controlling process conditions such as the switchover point and the holding pressure profile for each shot.

Mold maker FranciaCorta Stampi in Corte Franca, Italy, presented its capabilities on its DKT 2018 booth. The company not only produces molds for flash-free production, but also provides corresponding cold runner temperature control systems and complete LSR turnkey molding solutions for technical parts, such as membranes.

Although mainly a silicone profile extrusion company with solid silicone rubber compounding activity, M+S Silicon GmbH & Co. KG is also a molder of injection molded parts at its M+S-Kayser GmbH subsidiary in Nachrodt, Germany.

The company uses tools with up to 64 cavities, some of them produced in-house. The decision whether to mold solid or liquid silicone rubber at M+S depends on the quantities, as the company maintains higher tool costs with LSR — its core molding business — only justifies it with quantities as from 50,000 parts and thinner, less complex ones.

M+S ran a live injection molding demonstration at its DKT 2018 booth, in which it combined molding of solid silicone rubber and LSR on one injection molding machine, claiming to be one of the first companies to apply this form of two-component molding, aside from its established business in LSR/thermoplastic two-shot processing, as well as LSR overmolding of metal or glass after their pretreatment for adhesion optimization.

With headquarters in Eberstalzell and its customer and technology center in Schörfling am Attersee in Austria, Nexus Automation GmbH presented its Servomix servo-drive LSR mixing/dosing units with their Splitnex technology maintenance-free pumps that are claimed to ensure air-free dosing throughout dosing. Overall material loss amounts to less than 0.7 percent and the Servomix E200 Advanced unit can dose from less than 0.1g amounts up to 20 l/min.

As a first-time DKT exhibitor, Kottingbrunn, Austria-based injection molding machinery producer Wittmann Battenfeld GmbH (WiBa) used an all-electric drive EcoPower 160/130 molding machine equipped with the company's Unilog B8 control system and linked to a Nexus Servomix LSR mixing and dosing unit to produce LSR jigsaw puzzle pieces in a Momentive Performance materials grade of LSR.

Nexus supplied the 16-cavity mold with its Timeshot cold runner valve gate control system and worked with WiBa on the part handling system, which involved a WiBa W832 linear takeout robot for packing in a tubular bag machine and laying down of the bags on a conveyor belt.