Based on article appeared in November/December issue of European Rubber Journal magazine.
Less is more is seemingly the motto for the world of medical rubber appliances, as indicated by major materials and manufacturing companies, who are finding new ways of blending rubber into a cleaner and continuously more refined portfolio of products.
“We identified a strong trend towards combination products in the market. Customers are seeking components that incorporate more functions – often in small spaces,” said Heilmann.
In addition to small-sized silicone parts, Freudenberg Medical has recently developed options for surface modifications of silicone tubing and precision moulded parts.
These include drug eluting surface coatings for namely bariatric applications or port catheter systems.
“Silicone being a material which is very difficult to process makes this a significant challenge,” said Heilmann, who explained that some of the surface treatments include those for reducing friction and creating a barrier effect.
Commenting on the properties of silicone, Trelleborg’s LSR components director Ursula Nollenberger said silicone’s flexibility to be formed into “complex geometries over fast cycle times through injection moulding” made it a desirable material for medical applications.
“We see a clear trend toward ever smaller and complicated part geometries, and even more so toward integrated solutions,” she said, noting that many product developments are becoming two-component solutions.
These attributes, said Nollenberger, along with the closed-loop system of the LSR process are the main reasons silicone rubber is becoming more prevalent in sealing applications for the healthcare sector.
In life sciences, said Nollenberger, LSR growth is driven by an increasing trend toward self-treatment of chronic ailments such as autoimmune diseases, blood conditions and hormone deficiencies.
“This process requires developing ever smaller medical devices and components that function more reliably and in the absence of medical personnel,” she added.
In addition to market demands and patients’ expectations for smaller and more discreet devices, manufacturers also face a wealth of regulatory requirements relating to either their material or facilities.
“In general terms, we do see that products, materials and manufacturing practices are being scrutinised more stringently at all levels of the supply chain,” said Nollenberger who said Trelleborg welcomed the scrutiny.
FDA (Food and Drug Administration), USP (United States Pharmacopoeia) standards and ISO 10993 are among the material regulations to be met.
In addition, there are requirements relating to the finished products, such as surface cleanliness, off-gassing, leachable content – all besides the needed dimensional and functional requirements.
A key advantage of LSR injection moulding is the ability to mould several components into a single component.
“In life sciences applications this is particularly important to counter the prominent challenge of unwanted bacterial growth due to dead space in medical devices that cannot be reached by typical means of sterilisation,” said Nollenberger.
This includes complex two-component solutions that eliminate the potential for such problems.
LSR can be co-injected with a number of technical plastics into two-component solutions and into highly complex geometries, not possible with other elastomers.
At Munich-based Wacker, the demand for more refined products has led to the production of rollstock wafer-thin silicone films.
Wacker’s rollstock films, which consist of 100 percent silicone rubber in thicknesses down to 20 microns, can serve in a number of applications, including functional membranes, wound care products, and transducers based on dielectric elastomer technologies.
“The company offers two grades, Elastosil film for technical applications and Silpuran film designed for medical uses,” said Dr. Klaus Angermaier, responsible for the global product line and segment management of silicone elastomers at Wacker Silicones.
“The mechanical and elastic properties do not vary, no matter how often you exert a mechanical load,” explained Angermaier.
On account of their dielectric properties, silicone elastomers are categorised as electroactive polymers (EAP), which are capable of responding to electrical stimuli.
This means that silicone films are able to serve as actuators for converting electrical voltage into movement.
The reverse is possible, too: silicone films can also convert mechanical movement into electrical voltage, which makes them suitable for designing new kinds of EAP-based sensors.
As the films do not deteriorate over time, they are an option to dielectric films based on organic polymers.
“In laboratory trials,” said Angermaier, “silicone films have survived thousands of load cycles without the slightest fatigue. Their properties match key requirements for EAP based transducers, including actuators and even sensors, another commercial driver for this product.”
Silicone films, according to Wacker, are the key for developing extremely precise and efficient working sensors and actuators for sports wear, consumer electronics, medical, and healthcare applications.
“In so called smart wearables”, Angermaier added, “sensors based on silicone films are used to measure biometric data by tracing limb movements.”
One of the high-growth segments of the medical market is wound care, according to Chris Claussen of Momentive, which offers a special silicone gel for open and closed wound applications such as wound dressings, scar management, and tapes.
According to Claussen, Momentive senior global marketing leader, elastomers; the low viscosity, solvent-free, clear and colourless two-component silicone was developed in response to the budding advanced wound care market which is growing at approximately 3-4 percent CAGR.
“Manufacturers are looking to combine high skin adhesion and atraumatic properties with improved cost-effectiveness,” explained Claussen.
Innovations in adhesive technology, it seems, will continue to be a major trend as high strength and skin adhesion with painless skin removal and repositioning ability are becoming key features of wound-care products.
While acrylics have high permeability properties, explained Claussen, they can be painful to remove, are not typically repositionable and can damage skin upon removal.
However, the silicone gels provide the atraumatic properties with high skin tack, enabling coaters to produce wound care dressings in lower coat weights.