PTFE, FEP, PFA Recycling

1. Introduction.

Production of medical parts is set to grow rapidly worldwide, with specialized plastics gaining much of the growth, according to all the latest forecasts. Plastics come into the picture both as materials from which products are made and as packaging materials. Under both headings, formulations must be more closely controlled than in many other applications, usually to meet approval of the health authorities; the most influential of which are the US Food and Drug Administration (FDA) and the German Bundes Gesundheitsamt (BGa).On both counts, disposability is, of course, an essential element in the growing use of plastics, and, amid the growing concern about conservation of resources and disposal of waste, plastic medical devices and medical packaging present an interesting paradox. On the plus side, however, is the fact that much of this waste collects at hospitals, making it easier to devise effective solutions for recycling/ energy recovery, but these will also have their implications for the selection of individual plastics. In medical packaging, the key areas for development are tamperproof/ tamper -evident designs, calling for great ingenuity on the part of the package designer, remembering that a significant and growing user of packages is elderly people

There is an increasing market for blow moulded containers containing an ultraviolet opaque layer. For medical products, a typical polyethylene hip joint replacement is reckoned to have a working life of ten years and polyester composites are also being designed for this use.

The bio-medical field uses fluoropolymers in devices such as catheters and other parts with which to perform diagnostic and therapeutic procedures. Fluoropolymers’ superior barrier properties are exploited in pharmaceutical packaging where their high resistance to moisture protects pharmaceutical products.

Polytetrafluoroethylene (PTFE) based fabrics, such as Gore-Tex, enjoy increasing application in repairing wounds and arteries, where the structure forms a carrier for growth of tissue. A forecast from Frost and Sullivan finds that plastics are the largest sector of the European market for pharmaceutical and medical packaging. Plastics are forecast to grow from $344 million to $449 million, while glass will suffer a fall in sales. The most dramatic growth rate, however, will be recorded by labels. Frost and Sullivan stresses that environmental factors, such as legislation favouring reuse or recycling of packaging materials (now proposed on a European level) will naturally influence medical packaging. The UK holds a strong position with sales of disposable packaging materials growing continuously. The British Plastics Federation estimates that there are only about 600 processors in Europe which are qualified to manufacture medical plastics. Other industry experts suggest that there could be a demand for 1500 additional clean room manufacturing units in Europe (including expected demand from other industries such as electronics and optics). This will call not only for high-specification materials and products, but for some radical re-design of much of the existing processing equipment, to meet ever rising clean room standards. With these requirements in mind, all-electric injection moulding machines have been introduced by Cincinnati, Klckner and Battenfeld – but these do not themselves make a clean room. All the other manufacturing systems, particularly robotic handling and automated quality control and testing must also be designed for clean room operation – even down to closed-loop cooling systems.

2. Applications of PTFE , FPA and FEP in medical parts

a) A new British company, P2i, has patented its plasma process technology for PTFE layers applications. The technology, which has already been used for electronic devices, footwear, circuit boards, filter media and hearing aids, renders items waterproof by depositing a nano-sized layer of a liquid-repellent polymer on the surface of a plastic item. The coating, which is applied in a vacuum and is 40–80 nanometres thick (10,000 times thinner than a human hair), reduces the surface energy to one third that of PTFE without affecting the item’s look or feel, As a result, when in contact with the polymer layer, liquids form beads and simply roll off the item leaving it completely dry.

Texolon brand high purity PTFE is a product line particularly important in applications where material cleanliness is essential. The high purity PTFE material is molded, packaged, and labeled in a strictly controlled environment, ensuring the highest purity for demanding applications. High purity PTFE is preferred over standard PTFE in medical equipment components such as bellows, diaphragms, valves, fittings, and a host of other parts due to its exceptionally clean, contaminate-free characteristics. This material provides the purity, wear resistance, and corrosion resistance demanded in imaging, laboratory, therapy, surgical, and other critical medical applications.

b) Dry lubricant coatings in medical mechanical assemblies

Design and manufacturing engineers frequently develop medical devices that are considered complex mechanical assemblies, such as surgical staplers or other devices with multiple functions and lots of moving parts.

These designs frequently present functionality challenges that are the result of stacked tolerances, or the permissible limits of variation in a physical dimension that are specified by the design engineer to allow reasonable leeway for imperfections and inherent variability, without compromising performance of the finished assembly or process.

In the case of complex mechanical assemblies, these tolerances can “stack up” against each other and cause the device to take more effort to actuate, resulting in devices that do not operate as they were designed.

One simple solution for preventing the “stack up” of tolerances is the use of dry lubricants as a surface treatment. Dry lubricants that use PTFE technology thinly coat the surface of a finished device or mechanical assembly, reducing the extra friction caused by stacked tolerances and ensuring optimal device functionality and performance.

One logical solution to addressing tolerance issues would be to ensure higher levels of precision in the design phase by designing everything with tighter tolerances. However, in most cases this is not a viable option. Higher precision generally means a higher cost due to more frequent inspections and maintenance of the machines and tooling during the manufacturing process that are required to main – tain those high levels of precision.

So the challenge is to find a low-cost, efficient means to address tolerance issues. The use of a dry lubricant as a surface treatment often fits the bill. Dry lubricants have excellent materials compatibility and have the ability to conform to almost any surface geometry. Perhaps one of the greatest benefits of these surface treatments is that they are easy to apply in – house and incorporate into the assembly process, which further adds to their cost-effectiveness.

Especially important in the case of medical devices and manufactured parts, PTFE coatings do not migrate, meaning they will not transfer to packaging or otherwise untreated surfaces. This is in contrast to oil-based silicone coatings that readily transfer to packaging or adjacent surfaces. This transfer can compromise the later application of surface treatments such as markings or medication, or cause staining or other cosmetic issues which are unacceptable in the medical industry, where cleanliness is an essential requirement.

Additionally, PTFE surface treatments have been shown to reduce the force needed to actuate a device by as much as 30 percent in some instances.

Not all lubricants are created equal, and not one lubricant will be right for every situation. There are considerations to be taken into account when determining a coating process that is right for a specific device or manufactured part.

Design and manufacturing engineers don’t have to worry though, as they don’t have to choose their coating system or process alone. In addition to providing the product, some coatings providers also act as consultants to ensure engineers are using the right type of lubricant and then optimizing the manufacturing process to accommodate the application.

For example, if the device will be invasive, most likely a silicone-based coating will be used, as medical grade silicone has excellent lubricous properties and is widely accepted as safe for contact with human tissue. A PTFE coating will be used more often on mechanical assemblies that function outside of the body.

Knowing the number of cycles the part or device is intended to go through indicates if a more permanent coating is necessary.

The lubricant should be applied in a way that makes the most sense based on the geometry of the part, and the manufacturing volumes. Dry lubricants are easy to apply even in high-volume production environments and can be done in many different ways. When coating small parts, coils of wire and other items of varied shapes, dipping is a common method of application. Wiping or brushing is more common with parts that have continuous surfaces, such as rods, tubing or sheets.

All of these factors combine to help determine if the coating process can be done in-house. For example, the process of applying most types of PTFE dry lubricants and some silicone-based lubricants is so simple that it can be done in-house. However, more durable lubricants or those with specialized properties require more advanced application methods and may need to be applied by an experienced vendor off the manufacturing premises using highly specialized methods.

An example of this is specialized lubricants that add hydrophilic properties to treated surfaces. These lubricants create a lubricious surface that is dry in the packaging, but uses body fluids to enhance surface lubrication when the device is in-use. These coatings are more sophisticated than other types of lubricants and require special chemistries and application methods. Also, some types of PTFE-based surface lubricants need to be applied under precisely controlled thermal and atmospheric conditions to impart a more durable coating and a longer service life.

Other considerations include cost, safety, materials compatibility, floor space availability and environmental concerns. The coatings provider should be able to advise on all of these factors and counsel on general best practices.

Dry lubricants provide a cost-effective and efficient solution to address stacked tolerances. Partnering with the right coatings supplier can help to ensure that the design and manufacture of the device is done in a way that optimizes functionality and ultimately saves time and money.

c) Precision Coating, one of the largest plastics coating applicators in the world, opened a new, 7,500-sq-ft, dedicated medical device coatings facility in Boston. It is the result of a $1 -million investment by the company to provide added capacity for medical device companies with high commercial volumes.

Precision Coating serves global health care and medical device companies around the world, coating medical devices such as guide wires, core wires, hypotubes and forming mandrels. In addition to its proprietary, innovative, low friction polytetrafluoroethylene, the company also offers other PTFE systems, including zero-pertluorooctanoic acid and chromic-acid-free coatings.
The company has a flexible prototype location in Dedham, Mass.

d) Injection molder Performance Plastics Ltd. of Cincinnati has invested about $500,000 since the start of the year on three new Roboshot-brand electric molding machines from Milacron LLC.
The machines were needed because of additional work that performance has gained in making small medical parts based on fluoropolymer resins like PTFE,PFA and FEP.

A focus on medical molding has led to that sector now accounting for 25-30 percent of Performance’s annual sales. In 2005, that total was only 5-7 percent. The firm may add another molding machine by the end of the year.

Performance Plastics Ltd. now operates 22 molding machines and has room for as many as 30 more at its 40,000 square-foot facility. The 30-year-old firm has about 50 employees and has annual sales of $7 million.

Article Sources:

High Performance Plastics,January 1, 1994
Medical Design Technology,January 1, 2008
Products Finishing,November 1, 2011 | Tourigny, Jay

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