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LSR – the rising star in medical applications
Issue date:01/12/2017
China Plastic & Rubber Journal (CPRJ) - Dec 2017 Issue
Source:China Plastic & Rubber Journal
By Staff Reporters

Liquid silicone rubber (LSR) is a risingstar in the medical industry, despite the fact that it is costlier than theother grades of LSRs. New materials and processing technology have emerged topush the boundary further.


Self-adhesive LSR SILPURAN 6760/50 was specifically developed for medical technology and pharmaceutical applications.
Self-adhesive LSR SILPURAN 6760/50 was specifically developed for medical technology and pharmaceutical applications.

The global LSR market is projected to reach US$3.82 billion by 2026, growing at a compound annual growth rate (CAGR) of 8.3% from 2016 to 2026, and medical grade LSR is the fastest growing segment, according to the latest MarketsandMarkets research.

Market growing at 8.3% CAGR until 2026


LSR is used to manufacture various medical devices, accessories, and fittings, as they are temperature-resistant and easy to sterilize. A growing aging population is leading to the high growth in demand for LSR products in the healthcare industry.

The key players in this market are focusing on organic growth strategies to gain a greater market share. For instance, France’s Bluestar Silicones has teamed up with Graham Engineering Corporation, an extrusion equipment supplier in the US, to advance the development and testing of medical grade LSR tubing.

Graham Engineering has lent its equipment, including an American Kuhne 1.5” ULTRA RS silicone lab extruder, to Bluestar Silicone’s technical center in York, South Carolina, the US.

American Kuhne silicone extruders are the most advanced on the market today. In concert with our silicone materials expertise, we expect the collaboration to further optimize our heat-cured rubber product processing performance, as well as to provide additional levels of technical service and training for our medical and pharmaceutical tubing customers,” said Bob Waitt, Marketing Manager for Bluestar Silicones’s US medical market.

New material emerges

At the recently concluded COMPAMED 2017, Wacker Chemie has launched a new self-adhesive LSR that has a low coefficient of friction (CoF), a property that enables SILPURAN 6760/50 to be used in novel applications.

SILPURAN 6760/50 is an addition-curing LSR. It has two components and, once mixed, cures to form a transparent, mechanically robust elastomer with a 50 Shore A hardness. After post-curing, the vulcanizate has a CoF which is between 50-70% lower than that of standard LSRs of comparable hardness.

It is specifically designed for the production of parts comprising hard/soft combinations such as those used in the pharmaceutical and medical sectors. They are often made from a hard thermoplastic, which determines the shape, encased in a soft plastic layer.

The low CoF also facilitates the fitting of silicone components into medical devices.

Designed for injection molding, SILPURAN 6760/50 adheres readily to selected polyesters such as polybutylene terephthalate (PBT) without the use of adhesion promoter.

Smart processing ensures consistently high quality

Apart from advancement in materials, processing technology for LSR has also improved considerably. The consistency of the process is very important, since LSR is expensive and any fluctuation during the injection molding process would be costly.
KraussMaffei's PX 50-180 SilcoSet with encapsulated ejector is cleanroom compliant.
KraussMaffei’s new APC plus function takes on this important task, compensating for the batch fluctuations commonly encountered when processing LSR. It was demonstrated on a PX 50-180 SiloSet injection molding machine for the manufacture of LSR nasal ventilation units for babies.

LSR processing is especially demanding. The consistency varies from water to honey, and demands absolute platen parallelism to ensure that the mold closes extremely tightly and an injection molding process that is matured to the finest detail,” said Jörg Wittgrebe, Vice President Sales at KraussMaffei in China.

As the process progresses, APC plus monitors the viscosity of the material and corrects the filling volume even in the shot. The process as a whole is made even more precise; the part weight remains constant. APC plus is even able to compensate for any potential preliminary cross-linking of the silicone.

Integrated production cell driving unit costs down

LSR applications are also rapidly expanding in Southeast Asia in the past few years, especially in Thailand. Among other products, baby pacifiers and other baby care items are produced in very large volumes. There is the demand for economic solutions as requirements for the quality of the parts increase, according to Engel.

As quality requirements become more stringent, the focus is shifting more and more towards integrated processes. For example, multi-component processes based on thermoplastic-silicone bonds are a new topic for many processors here in the region,” said Aram Tongurai, Managing Director of the subsidiary Engel Machinery (Thailand).

Multi-component technology now opens up new market opportunities for companies. In the medical field, the new challenges include joint implants, respiratory masks and components for measuring instruments.

Highly integrated, compact production cells minimize the system footprint and increase area productivity. These aspects pay off especially in cleanroom environment.

When all cell components and materials are optimally matched from the very beginning, we can make full use of all the quality and efficiency potential,” explained Leopold Praher, Sales Manager for elastomer applications at Engel. “In many cases, integrated solutions achieve much lower unit costs since several work steps can be often eliminated.”

The tie-bar-less clamping units on the injection molding machines of the ENGEL victory and e-victory series are suited for automated multi-component processes involving liquid silicone.
Among other products, baby pacifiers are produced in very large volumes in Southeast Asia.
Since the complete area of the mold fixing platens can be used, large multi-component molds can be mounted on comparatively small machines and this reduces both investment and operating costs. The robot also has direct access to the cavities from the side without having to bypass interfering edges.

Engel’s patented force divider enables the moving mold mounting platen to follow the mold exactly while clamping force is building up, and ensures that the clamping force is evenly distributed across the platen face. Both the outer and inner cavities are therefore kept closed with exactly the same force, ensuring consistent compression of the mold and high product quality.

Last autumn, Engel reorganized the sizes of the hydraulic injection units and further optimized the performance specifications such as injection pressure, injection speed, and plasticizing capacity. This next-generation injection unit was unveiled at Fakuma 2017 together with an ENGEL victory 860/160 injection molding machine.

Together with the iQ weight control software, which Engel is now offering also for injection molding machines with hydraulic injection units, cavities are filled reliably even when there are fluctuations in the raw material.

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