Tech Talk Blog

We’ve received a request for a quick review of plasma, so I present Plasma 101…

Simply put, plasma is an ionized gas, a gas into which sufficient energy frees electrons from atoms. Plasma is the fourth state of matter.  With plasma, positive ions, negative ions, electrons and radicals coexist in a concert of reactions and collisions — as long as an electric potential exists.

Plasma systems control the treatment conditions by controlling the gas type, flow, pressure, and concentration.  Plasma also dictates the energy, frequency, wattage, and electrode configuration.

Vacuum plasma technique is one form of surface modification our team provides.  Plasma has the unique ability to treat a material three dimensionally to prime any surface for adhesion, painting, coating or printing.  And plasma is recognized as a “green” process that releases no hazardous byproducts.

As always, if you still need some clarification – don’t hesitate to Ask The Experts!

Accelerated aging is a testing method that enables us to estimate the potential lifespan or shelf life of a product when actual data is unavailable.  For instance, products may be subjected to unusually high levels of stress, or mechanical parts may be run at speeds far above normal.  In the case of polymers, they may be kept at elevated temperatures to study the subsequent chemical breakdown.

But what type of product bag should be used in an accelerated aging test?

There are three common options:

1)      Polyethylene — is inexpensive and readily available, but offers a low melting point.

2)      Polyester — offers a higher melting point and can withstand a rigorous aging study, but is more expensive and not widely available.

3)      Aluminum— can be a good option, but is not widely used.  Aluminum is inexpensive and able to reach a higher temperature.  However, aluminum bags are difficult to seal completely (much like foil).

Bag options must be closely considered to ensure a successful aging test. In accelerated aging for medical applications, for instance, we need to determine whether to keep all of the parts in one bag or in separate bags.  It’s best to duplicate the method most commonly used in the real-life environment.

Tell us about your experience with accelerated aging. Check out the Video Learning Center for more information, too!

We all know the importance of sterilization in medical applications and packaging, particularly as surgical procedures become more specialized. Proper sterilization of devices such as catheters, cell culture trays, stents, and implants is critical to ensuring a positive patient outcome.

We thought we’d offer a quick review of sterilization methods:

1)      Steam — This process dates back to the days of Louis Pasteur, who used heat to kill microbes — or “pasteurization” that is still used today to protect perishable products such as milk.

Steam is still a popular sterilization method prized for its simplicity and relatively short processing time.  However, it can cause decay to the polymer, and can destroy surface treatments through water exposure.

2)      Ethylene oxide (EOX)  — is an option for devices that are sensitive to heat and moisture.  EOX changes the surface of the polymer, but it will revert back.  It uses relatively low temperatures for sterilization, but requires a long aeration process after each cycle.

3)   Gamma rays – This is the method we most recommend.  It can be used on many products all at once – it even penetrates boxes.   We also like that it can be used on any plasma-treated surface and preserves the treatment molecules. With gamma, we can increase the dosage accordingly to modify bulk properties.  It is a unique process for cleaning and sterilization.

Which method of sterilization does your team frequently use?

Mid-winter is the thick of flu season, and in this age of H1N1, we are all aware that germs on the hands can spread bacteria that cause infection, disease and even food-borne illness.  In fact, the CDC reports that flu viruses can survive for several hours on hard surfaces we touch all the time, such as doorknobs and shopping carts.

But what if there were a permanent treatment for inanimate surfaces to help us avoid — and even eliminate — the spread of bacteria, pathogens, and viruses?  Our R&D team is at work on such a solution.

Although still in the testing stage, our propylene additive will have a permanent anti-bacterial and anti-fungal effect on hard surfaces.  The key to remaining germ-free?  A nano silver additive that keeps hard surfaces hygienic indefinitely.

Look for more information to follow.

Our team is designing a lens that must withstand military extremes such as salt spray, fog, humidity and temperature.  The coating must be abrasion-resistant and anti-reflective – what is the best treatment?

This is a great question — and a multi-step process. Assuming your lens is a polymer lens like polycarbonate or CR-39, currently there is no single surface treatment for both anti-abrasion and anti-reflective (AR) properties.  Instead, one would apply the anti-abrasion coating first, followed by the AR process, which is done in a vacuum for a uniform and consistent result.

Your abrasion-resistant coating options include:

A)    Polyurethane  – This usually is the most economical coating, which is applied by either sprayed or dip method. This is a popular treatment for end user ophthalmics, but also has the least durability and longevity.

B)    DLC (Diamond-like coating) – An extremely hard, durable coating, that is relatively expensive, but most effective for high-end users.  DLC ensures high-performance and impact-resistance as the resulting surface is very close to the hardness of diamond.

Our team can help you explore your best solution.

What is the best process for removing silicone oil from a catheter made of Pebax® tubing prior to a bonding operation?  Would you use plasma or corona?

Your question is one that we are seeing more frequently. And the short answer is that it all depends on the amount of oil.

If you can see a significant oil collection, then you need to wash the tubing in an ultrasonic bath with an emulsifier. Then, you may simply wipe the tubing with an alcohol wipe to remove any excess. It really depends on the level of contamination. Generally speaking, I’ve found that catheters have a superficial level of oil.

If the amount of oil is superficial, plasma can carry away the excess oil via a specific oxygen treatment. We do not advise corona treatment for this application, since it can make the silicone hydrophilic and give a false impression of being clean. Plasma is a more elegant solution and will “superclean” the surface to promote better adhesion.  Learn how we recently solved this challenge.

With the recent spike in air travel over the holidays, I was reminded of some of the aerospace materials that our team often treats, particularly foam. Foam is a common insulation material aboard aircraft, used to fill open crevices between the passenger compartment and the outer shell.  It serves a number of functions such as regulating temperature, reducing engine noise, and protecting the mechanical systems from moisture and temperature variations that may lead to corrosion.

Currently, micro-light fiberglass is used for aircraft insulation, but it has the tendency to absorb moisture, which can add substantial — and unwanted — weight to the craft.  A typical flight may consist of up to 1,500 lbs of water weight.

Our team is working on an alternative to fiberglass insulation . The following materials are foam products that offer good acoustic, insulative, and weight properties, but have a tendency to absorb moisture like the fiberglass. We treat these foam products to inhibit these properties:

1)      AC 530 — a polyimide material, is lightweight, fire resistant and offers thermal and noise insulation.  It is a flexible material, but holds its shape and conforms to structural inlay. But, this foam is prone to moisture absorption.

2)      Melamine foam — is also lightweight, fire resistant, and offers thermal and noise insulation. This foam is flexible and holds its shape and conforms to structural inlay. But, this foam will naturally absorb moisture particularly well.

Our hydrophobic process offers the distinct advantage of penetrating the entire surface of the material, unlike some processes that may sit only on the surface. Our process enhances the properties to form a better water-resistant property that inhibits the absorption of moisture maintaining the dry weight of the aircraft.

As always – if you are still burning with questions, Ask The Experts!

A recent development at TriStar – Surface Modification Division is a liquid surface treatment to induce a hydrophobic property. Most foam materials are very hydroscopic and absorbent. When our hydrophobic liquid surface treatment is applied to most foam materials, the foam becomes extremely hydrophobic. Below is an image of our treatment on medical grade polyurethane foam.

Though our tests indicate this treatment does not work well on natural materials like wood and cotton, but this treatment performs great on synthetic fibers and fabrics.

If you would like more information on this product, please continue to our website at www.tstar.com.

Recent headlines tell us that everything from our kitchen cutting boards, Tupperware and soda fountain delivery tubing are infected with everything from fecal matter to salmonella. There are solutions available thanks to new polymer technology using antimicrobial additives and surface treatments. Many polymers are now available with silver ions which help to effectively inhibit the potential growth of bacteria, yeast and fungi on the polymer surface. By using unique zeolite carriers with silver ions, a counter force to the sodium ions present in moisture  interrupt respiration, reproduction and metabolism of destructive microbes. TriStar offers several polymer solutions now in molding and extrusion resins to dramatically reduce the potential of microbial growth in your products. Browse through our Video Learning Center for even more information.

The growth of plastics in medical devices is growing exponentially around the world.  Plastics are regulated like any other materials that may come in contact with human tissue or fluids and that usually falls under testing procedures issued under USP or ISO10993. There are three time scales for biocompatible devices. “Limited” would be less than 24 hour exposure, “Prolonged” is 24 hours to 30 days and “Permanent” is 30 days and longer. Device’s are categorized as Surface Devices which would be items such as electrodes for monitoring, contact lenses, catheters, endotracheal tubes, sigmoidoscopes and similar devices. Second would be Externally Communicating Devices such as  laprascopes, blood administration devices, pacemakers, oxygenators and the like. Finally are Implant Devices such as orthopedic pins or plates, heart valves, grafts, stents and similar devices.

Testing of these devices includes mechanical, thermal, chemical tests as well as systemic injection, intracutaneous and implantation. All of these must be done before a plastic component can be approved. Typical materials for biocompatible applications include medical grades of PVC and Polyethylene, PEEK, Polycarbonate, Ultem PEI, Polysulfone, Polypropylene and Polyurethane. For more specific information on Biocompatible materials as well as special plasma preparation treatments of all of these materials, contact TriStar Plastics at www.tstar.com and visit our Video Learning Center and our Materials Database.