Best of plastics: Medical
Monday, October 10, 2016
Note: This is the third of a five-part "best of" series covering trends, material/process advances and applications in electrical and electronics, barrier packaging, medical, bioplastics and 3-D printing.
The medical device industry is making important contributions to advances in healthcare, and this sector is characterized by a high level of innovation and intense competition. One of the interesting aspects of research and development within the medical devices field is the coupling of diverse biomedical and engineering disciplines.
The medical devices industry involves the input of companies within the plastics and other advanced materials fields, as well as microelectronics, software, telecommunications and biopharmaceutical, as outlined by the Advanced Medical Technology Association (AdvaMed).
International markets for the medical device industry.
The global medical device industry market is large, complex and fragmented. Estimates of the value of the global market depend on the interpretation of the term "medical device" as it can be applied to a wide range of products.
It has been suggested that the global market is comprised of about 8,500 types of medical devices, ranging from simple bandages and spectacles, through life-maintaining implantable devices, equipment to screen and diagnose disease and health conditions, to the most sophisticated diagnostic imaging and minimally invasive surgery equipment.
Although estimates of the global market value — generally considered to be in the $140-150 billion range — differ, it is agreed that the largest market is that of the United States, followed by Europe and Japan.
Innovative medical technologies offer an important solution for nations that face growing healthcare needs and constraints on resources, including the demands of aging populations. Advanced medical technology can not only save and improve patients' lives, but also lower healthcare costs, improve the efficiency of the healthcare delivery system, and improve productivity by allowing people to return to work sooner.
To deliver this value to patients, the medical technology industry invests heavily in research and development (R&D), and the U.S. industry is a global leader in medical technology R&D. The level of R&D spending in the medical device and diagnostics industry, as a percentage of its sales, more than doubled during the 1990s.
In absolute terms, R&D spending has increased 20 percent on a cumulative annual basis since 1990. This level of spending is on par with spending by the pharmaceutical industry and more than three times the overall U.S. average.
The medical technology industry is fueled by intense competition and the innovative energy of small companies. These firms drive rapid innovation cycles among products, which in many cases lead to new product iterations every 18 months. For example, let's take a look at innovative commercialized medical plastics materials, processes and applications.
Let's start with polybutylene terephthalate (PBT) resin material tailored for medical device dimensional accuracy. BASF's Ultradur B4520 PRO is a fully commercialized PBT for injection-molded applications in medical technology. Its high dimensional stability and optimized shrinkage behavior meet the stricter reproducible dimensional accuracy requirements for medical device components.
Other property features are as follows:
- Sterilized with ionizing gamma radiation or ethylene oxide
- Can easily be printed on
- Broad chemical resistance to polar and nonpolar solvents
- Low water/moisture absorption
- Ideal sliding, due to high friction and wear resistance (depending on the sliding partner)
- Excellent heat aging behavior
- Good moldability with fast cycles
Functional and mechanical components for insulin pen.
Possible medical applications include:
- Functional and mechanical components with high dimensional precision and stability for use in drug delivery systems such as insulin pens, inhalers or metering devices
- Device components such as manifolds, screws, sleeves, valves, plungers, lancets or caps
- Chassis and housings
- Filter systems
- Drug containers
- Pharmaceutical closures
- Technical disposable applications
Next on the processing development front, medical-grade fibers and yarns used for implantable medical devices are produced through three primary techniques based on the extrusion of a polymer melt or solution, and are as follows:
- Melt spinning: melted polymer extruded through spinneret
- Dry spinning: polymer is dissolved in volatile organic solvent prior to fiber spinning
- Wet spinning: uses nonvolatile solvent and coagulation bath
Islands-in-sea multicomponent fibers.
Adhesives Research Inc. has recently unveiled ARmicron-engineered medical fiber technology made possible through a unique HDME melt spin process. Melt spinning without the use of solvents is the preferred technique for medical fiber production today.
The process allows monofilament, multifilament and fine-denier fibers to be manufactured from a range of biocompatible, nonresorbable or bioresorbable polymers with tailored physical properties.
Examples of biocompatible polymers used in HDME medical fibers.
These custom design capabilities enable development of multicomponent fibers with highly resolved internal domains or external submicron surface architectural definitions. This allows new design possibilities for wound healing, implantable devices and medical textiles, as well as new design and functional flexibility to applications in controlled drug delivery and may be beneficial for directional cellular in-growth for tissue engineering.
Continuing forward application-wise, a battery-powered molded pump implant based on PEEK Vestakeep (a polyether ether ketone supplied by Evonik) helps patients suffering from excessive fluid in their abdomen.
The ALFAPump System developed by Sequana Medical Switzerland consists of a subcutaneously implanted battery-powered pump and catheter system. One catheter connects the abdomen to the pump, and a second connects the pump to the bladder to automatically and continually collect ascites (abdominal fluid) and move them to the bladder for elimination through normal urination.
Medical-grade PEEK is specifically suited to long-term use in the human body. PEEK is particularly characterized by its biocompatibility and biostability. In contrast to metal, the PEEK ion content is virtually zero, preventing reactions with the body.
The PEEK implant is also considerably lighter than a comparable metal implant. It can also be made transparent to X-rays and can be formed by injection molding into complex shapes as required. The ALFAPump System, which earlier received CE approval, is currently has been introduced into leading hepatology centers across Europe. Other producers of medical-grade PEEK include Victrex and Solvay Specialty Polymers.
Currently in medical applications, Tritan copolyester for blood therapy surgical and blood management devices have been successfully commercialized by Eastman Chemical Company. The copolyester can be used in many blood therapy devices, including surgical devices such as oxygenators, hematological reservoirs, hematological filters, cardioplegia filters and bubble trap devices.
Additionally, it has proved suitable and made commercial inroads into such blood management devices as blood separation cassettes, blood microfilters or centrifugal devices. The material is BPA-free and also has:
- Good clarity — allowing easier detection of air bubbles, blood clotting and leakage.
- Chemical resistance — remains aesthetic and functional after exposure to blood, lipids and aggressive disinfectants. This also means improved environmental stress crack (ESC) resistance during solvent bonding that uses cyclohexanone or other solvents.
- Color stability
- Good processability
- Toughness — this performance feature of Tritan copolyester compares favorably with Polycarbonate (PC) and offers significantly better impact strength than other common thermoplastics.
- Eliminates annealing required for PC — has a lower inherent residual stress compared to PC.
- Retains glasslike transparency after gamma or electron beam radiation and sterilization with ethylene oxide gas — Tritan has maintained its strong reputation as a virtual material drop in for PC.
Blood therapy management device (left), and Tritan copolyester vs. polycarbonate gamma sterilization comparison (right).
Finally in medical plastics packaging, Klöckner Pentaplast's triplex configured PVC/PVdC/PVC film, Pentapharm alfoil E S03, employs Solvay's Super B PVdC, high-crystallinity PVdC dispersion with better barrier properties and heat resistance than standard PVdC. The transparent film, an extension of the leading film producer's PVdC coated polymer film product line is flexible enough to support bending without cracking and has barrier properties comparable to high barrier grades of Aclar.
These new films are the only high-moisture/oxygen barrier PVdC-coated films that have a three-layer symmetrical structure designed for higher performance on packaging lines. The films thermoform in the same temperature range as PVC mono film, and the PVC skins provide a low coefficient-of-friction to prevent blocking on preheat plates and supply more consistent material flow during the thermoforming process. These films seal well with all standard vinyl compatible lidstock and comply with U.S. Food and Drug Administration pharmaceutical packaging requirements.
The Pentapharm alfoil E S03 is an economical barrier alternative to Aclar lower barrier grade films and provides a good cost/barrier ratio relative to standard PVdC films. For instance, a 120-gram-weight Pentapharm alfoil E S03 film has twice the oxygen barrier characteristics of a 90-gram weight film using standard PVdC.
Pentapharm high barrier films.
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