Wednesday, June 13, 2018

PTFE Guidewire Application Process Eliminates Delamination

Solution proven to have no PTFE delamination for 34,000,000+ guidewires.
The guidewire coating delamination problem reached catastrophic proportions late last year. In October, Medtronic—a major guidewire supplier—recalled over 84,000 units that had the potential for the PTFE coating to flake off. But Medtronic was not alone; other manufacturers have recalled guidewires, too.

These were FDA Class 1 recalls, meaning these guidewires and microguidewires represented serious health risks in which the applied coating—PTFE in this case—had the potential to delaminate or flake off. If this occurs before or during a medical procedure and even a microscopic flake enters the patient’s bloodstream, the results can be serious, including blood clots, stroke, heart attack, tissue necrosis, and even death. Between January 2014 and November 2015, the FDA received approximately 500 Medical Device Reports—including reports of nine deaths—attributed to PTFE coating delaminating from guidewires.
 
The medical ramifications to the patient and their family are undeniably devastating. For the guidewire manufacturer, the results can also be catastrophic. Based on other comparable recalls, the device manufacturer will take a substantial hit to their reputation and see their stock prices and market cap often falling 10 percent from a single incident.
 
Further, there is the matter of unresolved liability. Defending a lawsuit stemming from blood clots, stroke, or death resulting from a faulty guidewire would undoubtedly be a costly endeavor, and the damages available to the patients and their families can be significant. There is no set benchmark for the types of damages available in these cases, particularly when the damage done to a patient is open-ended and requires ongoing treatment or hospitalization, which may make early resolution more difficult. Litigants and the courts will invariably look to other defective medical products for guidance. “The lawsuits that stem from defective catheter guidewires may follow the pattern established for the IVC filters that were designed to block blood clots,” explained Rachel V. Rose, a trial lawyer in Houston who is experienced in medical litigation. “In the case of guidewires, look for ‘bellwether’ cases in different parts of the nation to set the standard for monetary awards.”
 
Background
Coating a guidewire with PTFE is necessary for its smooth operation in the peripheral, coronary, and neuro vasculature. The coating reduces friction and eliminates the potential for binding and kinking during a procedure and, from the physician’s standpoint, the motion of the guidewire needs to be smooth and unhesitating. The difference in the tactile feel of a guidewire without and with PTFE is dramatic.

The origin of the problem of PTFE flaking on guidewires appears to correspond with the Environmental Protection Agency’s mandate earlier in this decade to eliminate the surfactant—PFOA—from water-borne PTFE formulations because PFOA is a suspected carcinogen. For 50 years, pure PTFE, with the aid of PFOA, had been the gold standard coating for guidewires. It is believed that PFOA improved adhesion to smooth metal surfaces, including guidewires. Without it, the flaking problem struck with a vengeance, especially when guidewires were soaked before use in the ever-present saline used in medical procedures. Saline penetrates the porous coating and, if adhesion is marginal, causes it to bubble and delaminate. Reports from operating theaters indicated that guidewires coated with the new PFOA-free PTFE were visibly flaking after being placed in saline soaking tanks.
 
An initial “fix” for the delamination problem was to switch from pure PTFE to resin-bonded PTFE. These early formulations are based on particles of pure PTFE and other low-friction particles, suspended in a tough polymer resin. While adhesion was improved, friction became a problem. While the coefficient of friction of pure PTFE is as low as 0.02 (similar to ice), the original resin-bonded coatings often had between 1.5 to 4 times more friction. Over time, the friction of the resin-bonded coatings has been improved, but not to the level of pure PTFE. This means the smooth operating feel of the old coated guidewires was lost, and the tactile feedback sensed by a physician operator is heavier, hesitant, and jerky. Known as “stick-slip,” this phenomenon is the transition from static friction to dynamic friction. Some physicians reported that they could not differentiate between a vascular obstruction and a momentary resistance of the guidewire.
 
There is another potential problem with resin-bonded PTFE: an unknown shelf life. If the substitute coating is not completely cured, it contains solvents that could adversely affect packaging, while the original water-based coatings had no such issue. Given all of this information, it appears that PTFE would be the ideal coating for guidewires as long as the delamination problem could be resolved once and for all.

Tags:teflon,ptfe teflon,gudiewire

Monday, June 11, 2018

The Impact of Fluoropolymers on the Medical Device Industry


The impressive growth of the medical device, biomedical and healthcare industries over the past 15 years continues unabated even as materials such as fluoropolymers are meeting the increasingly challenging demand for new products and procedures. In general, fluoropolymers are progressively replacing other plastics in medical applications owing to their ability to meet the physical and biocompatibility requirements of the next generation drugs and devices.  Fluoropolymers meet a unique set of performance criteria in such applications. These include biocompatibility, lubricity, sterilization, chemical inertness, a wide temperature use range, low binding to process equipment, high-purity with low extractables, dielectric properties, and USP Class VI certification.

The family of available fluoropolymers that meet the above needs include grades of PTFE, FEP, PFA and PVDF resin from various resin producers. PTFE(teflon) has a well-established implant history of soft tissue replacement due to its biocompatibility and inertness. Resin and downstream product manufacturers continue to respond to new performance requirements by making appropriate modifications to the chemistry of the resin and surface configuration of the products, respectively.

The biocompatibility of any polymer is a principal requirement in any medical device such as catheters, bio-containment vessels, syringes and sutures. PTFE, FEP and PVDF are well established biocompatible materials, and their lubricity and chemical resistance make them the material of choice for products such as multi lumen tubing and others that are used in minimally invasive procedures. Multi lumen fluoropolymer catheter tubing for example allows surgeons to perform multiple procedures using the same catheter.

Fluoropolymers, especially PTFE(teflon)and PVDF are widely used in microporous membranes. Membranes, containing billions of pores ranging in size from 0.01 to 10 microns act as filters for particles and bacteria in critical fluids. PTFE and PVDF are among the few polymers used for filter membranes. The surfaces of the polymers membranes can be modified to deliver specific filtration properties and can be hydrophobic (water repelling) and oleophobic (oil, solvent, low surface tension fluid repelling). PVDF membranes can be also be surface modified to be hydrophilic (water loving) for removal of viral particles in the manufacture of therapeutic proteins and monoclonal antibodies. PVDF blotting membranes are particularly well suited for low background immunoblotting (western blot analysis), as well as for amino acid analysis and protein sequencing.

Accessory equipment, such as pumps, tubing, fittings used in conjunction with medical devices must meet similar performance and specification parameters. Accessories in direct contact with fluids are constructed of fluoropolymers such as PTFE and PVDF. For example, metering pumps such as diaphragm pumps are required for precise and repeatable flow, sometimes for chemically aggressive fluids.  Both PTFE and PVDF tubing are used in the construction of these pumps for this reason.

PVDF, although having a lower use temperature limit than PTFE(teflon), has a relatively high tensile strength and excellent permeation resistance to many fluids. It has a lower density (1.78 g/cc) than other fluoropolymers (approximately 2.18 g/cc). Due to a lower melting temperature than other fluoropolymers, it is more easily processible into products such as pipes, tubes, injection molded parts and films. It offers excellent dimensional and UV stability and is therefore finding new uses in aerospace, sensors, biotechnology and robotics markets.

Tags:teflon, Fluoropolymers,medical device

Monday, June 4, 2018

TEFLON, AN INVENTION THAT STICKS

1938: Fiddling around in the lab one day, Roy Plunkett accidentally discovers polytetrafluoroethylene, soon to be known as Teflon, a slippery substance that will have practical applications in everything from nonstick cookware to a presidential nickname.
Plunkett, a chemist at DuPont's Jackson research lab in New Jersey, made his discovery in the time-honored scientific way: as the result of a mistake, and with an assistant's help.
Plunkett and his assistant, Jack Rebok, were testing the chemical reactions of tetrafluoroethylene, a gas used in refrigeration. The gas was contained in some pressurized canisters, one of which failed to discharge properly when its valve was opened.
Rebok picked up the canister, only to find that it was heavier than an empty canister would be. He suggested cutting it open to see what had happened and, despite the risk of blowing the lab to kingdom come, Plunkett agreed.
Of course, it was heavy: The gas hadn't accidentally escaped. It had solidified into a smooth, slippery white powder as the result of its molecules bonding, a process known as polymerization.
This new polymer was different from similar solids like graphite: It was lubricated better and extremely heat-resistant, due to the presence of dense fluorine atoms that shielded the compound's string of carbon atoms.
Setting other work aside, Plunkett began testing the possibilities of polytetrafluoroethylene, eventually figuring out how to reproduce the polymerization process that had occurred accidentally the first time.
DuPont patented the polymer in 1941, registering it under the trade name Teflon in 1944. The first products — most having military and industrial applications — came to market after World War II. It wouldn't be until the early 1960s that Teflon became a household word when it was used to produce the most effective, heat-resistant cookware yet seen.
The word gained a certain pop-culture notoriety in the 1980s when the media began referring to Ronald Reagan as the Teflon president, a reference to his infuriating ability to avoid being tarnished by the various scandals plaguing his administration.
Teflon cookware, however, remained as steadfast and reliable as ever.
Teflon is found virtually everywhere today, coating metals and fabrics, from the aerospace industry to clothing to pharmaceuticals.
For his discovery, Plunkett, who retired from DuPont in 1975, was enshrined in the National Inventors Hall of Fame.
Source: About.com, Wikipedia
Teflon-coated cooking tools like this muffin tin and baking tray have eased setup and cleanup in millions of kitchens.

Tags:teflon,ptfe teflon,ptfe

Friday, June 1, 2018

8 Applications of PTFE Tubing


1. Aircraft Industries PTFE tubings are the non-flammable fluoropolymers that have lower friction coefficient which make them able to work properly under extreme temperature and pressure that's why these tubings are being used in the aircraft industries to wrap the wiring and cables.

2. Automotive Industries In the automobile engine, for fuel evaporation and fuel rails a high quality tubing is used which is made of Teflon PTFE which has low gas permeability.

3. Electrical Industries In electrical industries, to cover the electric wires and cables a high quality Teflon PTFE tubing is used that can bear the high temperature and protect the wire from any cuts. Also, these tubings are avalable in multi-colors that helps to identify the wires during the connection at homes or offices.

4. Medical Apparatus and Devices Fluoropolymers are used in medical industries to manufacture various instruments and devices like drainage tubings, ventilators, earpieces, aprones, gloves and other artificial tissues. Along with these, many functional devices which doctors use in biochemical analysis of human body are also made of the Teflon ptfe.

5. Food Industries In food industries for food processing special rollers are used. To expand the lifeline of these rollers wrap of Teflon FEP roll covers are done which are also non-sticky in nature that helps to maintain the quality of the product.

6. Textile Industries The transfer of chemicals in the pipes used in the textile industries cause corrosion. So, to avoid this problem Teflon TPFE tubings are used and also on the textile rollers the coating of PTFE done.

7. 3D Printing Industries In 3D printing, the filament should be transferred to the printing nozzle which have to perform under high temperature range. Since, the PTFE tubing has high temperature coefficient along with non-sticky nature which helps to easily slip the material from the nozzle so that it is most preferable polymer in the 3D printing industries.

8. Chemical Industries Non-alkali nature of the Teflon PTFE make it able to use in the chemical industries where transfer of the highly sensitive fluids is a common thing.
Tags:teflon ptfe,Teflon,ptfe tubing

Thursday, May 31, 2018

Teflon and Perfluorooctanoic Acid (PFOA)

What are Teflon and PFOA? Where are they found?
Teflon® is a brand name for a man-made chemical known as polytetrafluoroethylene (PTFE). It has been in commercial use since the 1940s. It has a wide variety of uses because it is extremely stable (it doesn’t react with other chemicals) and can provide an almost frictionless surface. Most people are familiar with it as a non-stick coating surface for pans and other cookware. It is also used in many other products, such as fabric protectors.
Perfluorooctanoic acid (PFOA), also known as C8, is another man-made chemical. It is used in the process of making Teflon and similar chemicals (known as fluorotelomers), although it is burned off during the process and is not present in significant amounts in the final products.
PFOA has the potential to be a health concern because it can stay in the environment and in the human body for long periods of time. Studies have found that it is present worldwide at very low levels in just about everyone’s blood. Higher blood levels have been found in community residents where local water supplies have been contaminated by PFOA. People exposed to PFOA in the workplace can have levels many times higher.
PFOA and some similar compounds can be found at low levels in some foods, drinking water, and in household dust. Although PFOA levels in drinking water are usually low, they can be higher in certain areas, such as near chemical plants that use PFOA.
People can also be exposed to PFOA from ski wax or from fabrics and carpeting that have been treated to be stain resistant. Non-stick cookware is not a significant source of PFOA exposure.
Do Teflon and PFOA cause cancer?
Teflon
Teflon itself is not suspected of causing cancer.
PFOA
Many studies in recent years have looked at the possibility of PFOA causing cancer. Researchers use 2 main types of studies to try to figure out if such a substance might cause cancer.
Studies in the lab
In studies done in the lab, animals are exposed to a substance (often in very large doses) to see if it causes tumors or other health problems. Researchers might also expose human cells in a lab dish to the substance to see if it causes the types of changes that are seen in cancer cells.
Studies in lab animals have found exposure to PFOA increases the risk of certain tumors of the liver, testicles, mammary glands (breasts), and pancreas in these animals. In general, well-conducted studies in animals do a good job of predicting which exposures cause cancer in people. But it isn’t clear if the way this chemical affects cancer risk in animals would be the same in humans.
Studies in humans
Some types of studies look at cancer rates in different groups of people. These studies might compare the cancer rate in a group exposed to a substance to the cancer rate in a group not exposed to it, or compare it to the cancer rate in the general population. But sometimes it can be hard to know what the results of these types of studies mean, because many other factors might affect the results.
Studies have looked at people exposed to PFOA from living near or working in chemical plants. Some of these studies have suggested an increased risk of testicular cancer with increased PFOA exposure. Studies have also suggested possible links to kidney cancer and thyroid cancer, but the increases in risk have been small and could have been due to chance.
Other studies have suggested possible links to other cancers, including prostatebladder, and ovarian cancer. But not all studies have found such links, and more research is needed to clarify these findings.
What expert agencies say
Several national and international agencies study different substances in the environment to determine if they can cause cancer. (A substance that causes cancer or helps cancer grow is called a carcinogen.) The American Cancer Society looks to these organizations to evaluate the risks based on evidence from laboratory, animal, and human research studies.
The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO). One of its goals is to identify causes of cancer. IARC has classified PFOA as “possibly carcinogenic to humans” (Group 2B), based on limited evidence in humans that it can cause testicular and kidney cancer, and limited evidence in lab animals.
(For more information on the classification system IARC uses, see Known and Probable Human Carcinogens.)
The US Environmental Protection Agency (EPA) maintains the Integrated Risk Information System (IRIS), an electronic database that contains information on human health effects from exposure to various substances in the environment. The EPA has not officially classified PFOA as to its carcinogenicity.
In a draft (not final) report, the EPA’s Scientific Advisory Board examined the evidence on PFOA, mainly from studies in lab animals, and stated that there is “suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential.” The board agreed that new evidence would be considered as it becomes available.
Other agencies have not yet formally evaluated whether PFOA can cause cancer.
What is being done about PFOA?
The long-term effects of PFOA and similar chemicals are largely unknown, but there has been enough concern to prompt an attempt to phase out industrial emissions of them. Only a handful of companies have used these chemicals in manufacturing in recent years.
While the possible long-term health effects of PFOA are not known, the issue is currently under study by the EPA and other agencies. In addition, in 2006, the EPA and the 8 manufacturers who used PFOA at the time agreed to a “stewardship program.” The goals were for the companies to reduce factory emissions and product content levels of PFOA by 95% by the year 2010, and to eliminate PFOA from emissions and product contents by the end of 2015. The companies have submitted annual reports on their progress to the EPA, and the latest reports indicated a large reduction in use of these chemicals. The decreasing demand for PFOA has also led to many companies phasing out production.
The EPA does not regulate the levels of PFOA or related chemicals (such as perfluorooctane sulfonate, or PFOS) in drinking water at this time. However, in 2009, the EPA released provisional health advisories (PHAs) for PFOA and PFOS in drinking water. These advisories recommend that actions should be taken to reduce exposure when contaminants go above a certain level in the drinking water – 0.4 µg/L (micrograms per liter) for PFOA and 0.2 µg/L for PFOS. These advisories are not legally enforceable federal standards and are subject to change as new information becomes available.
Should I take measures to protect myself, such as not using my Teflon-coated pans?
Other than the possible risk of flu-like symptoms from breathing in fumes from an overheated Teflon-coated pan, there are no known risks to humans from using Teflon-coated cookware. While PFOA is used in making Teflon, it is not present (or is present in extremely small amounts) in Teflon-coated products.
Because the routes by which people may be exposed to PFOA are not known, it is unclear what steps people might take to reduce their exposure. According to the US Centers for Disease Control and Prevention (CDC), people whose regular source of drinking water is found to have higher than normal levels of PFOA or similar chemicals might consider using bottled water or installing activated carbon water filters.
For people who are concerned they might have been exposed to high levels of PFOA, blood levels can be measured, but this is not a routine test that can be done in a doctor’s office. Even if the test is done, it’s not clear what the results might mean in terms of possible health effects.
Tags:teflon,teflon ptfe,PFOA

Monday, May 28, 2018

For Dummies 5 Questions and Answers about Polymer Bellows

One of the primary uses of bellows is to absorb dimensional changes due to thermal effects, which is very useful when used high temperature flows such as steam.  Bellows also serve to dampen vibration in the system caused by rotating components, protect sensitive and brittle processing equipment, and to absorb shock loadings.
Why is PTFE a popular choice for bellows?
PTFE (also known by its trade name Teflon) is a popular choice for the bellows material.  It is ideal for use in highly corrosive environmentssuch as those involving strong oxidizing and reducing accents, salts, high concentrations of acid, and chemically active organic compounds.  It has an extremely long flex life (how many flexing cycles it can handle before it fails), and a very low spring rate (amount of force needed to flex the bellows) – which means that it can reliably handle the challenge of fluctuating and vibrational loadings.
What types of movements can bellows be used to absorb?
There are three types of movement that bellow expansion joints can absorb:  axial deflection, lateral deflection, and angular deflection.  Axial deflection includes compression and extension affects along the longitudinal axis of the bellows.  Lateral deflection occurs when the end joints of the bellows displace relative to each other. Also known as parallel misalignment, this type of deflection can also be absorbed by a bellows expansion joint. Angular deflection can be described as a rotational displacement, or twisting displacement.
How does the number of convolutions affect bellow performance?
Recall that a convolution is the smallest flexible unit in a bellows.  The general heuristic for bellow convolutions is this:  fewer convolutions will give you better pressure and temperature ratings, BUT the amount of movement it can handle is more limited than bellows with more convolutions.  More convolutions, on the other hand, can absorb more movement but at a cost in pressure/temperature ratings.
Are there other polymers used for bellows?
Yes, another polymer option for bellows is UHMW PE, ultra-high molecular weight polyethylene.  While not as chemically resistant as PTFE, it currently has the highest impact strength of any polymer on the market today.  If the bellows are used in connection with abrasive materials, UHMW PE would be a valid alternative to PTFE because it has better abrasion resistance.
PFA, or Perfluoroalkoxy or Teflon PFA, is similar to PTFE(teflon) in many ways and is someone chosen in place of PTFE because it offers higher strength at extreme temperatures, even in the presence of extremely aggressive chemicals.
TFM, or PTFE-TFM, is a second-generation PTFE that has better fatigue properties than PTFE and offers better stress recovery.  It is well adapted for situations that involve high temperatures and vacuum pressures.
Bellows Conclusion
Bellows serve a variety of purposes – form absorbing displacement and shock to preventing sensitive equipment of a brittle nature.  They can absorb axial, lateral, and angular displacements.   The number of convolutions in a bellow is related to both its strength and pressure rating as well as the maximum amount of displacement it can absorb.  Finally,  polymers such as PTFE(teflon), UHMW PE, PFA, and TFM are popular choices for bellows materials, although PTFE seems to remain the first choice for many engineers.
Tags:teflon ptfe,teflon,bellows

Sunday, May 27, 2018

Ball Valve Seals - 6 Key Materials You Should Know About

Ball Valve Seals Material Choice
The choice of a seal material for a ball valve is vital to its successful operation.  In this post, we are going to look at some of the major characteristics of six commonly used options for polymer seals in ball valves.
Here are some additional post on Polymer Seats and Sealing Solutions:
  • Ball Valve Seats - 9 Significant Purchasing Options
  • Advanced EMC Technologies High Performance Sealing Solutions Guide
  • PTFE Rotary Lip Seals - 6 Feature Competitors Don’t Want You to Know!  
Key Material #1: Virgin PTFE 
Virgin PTFE (trade name Teflon) is ideal as a ball valve seal material for pressures less than 5 ksi and temperatures between -20 F and 400 F; however, its temperature performance does depend on pressure.  Speaking of pressure, PTFE does not decompress well after being pressurized.  Note that teflon does not perform well when subjected to temperature fluctuations greater than 167 F. One of its greatest strengths is chemical resistance, being close to insoluble; another strength is extremely low friction.  It is also fire resistant.
Key Material #2: Glass Reinforced PTFE 
Reinforced PTFE as used in ball valve seals is typically 15% glass fiber, increasing the temperature and pressure rating available with virgin PTFE.  Like unreinforced teflon, glass reinforced PTFE still has very good chemical resistance with the exception of hot caustics and hydroflourics.  It, too, is fire resistant and has low friction, though not as low as virgin PTFE. 
Key Material #3: Stainless Steel Reinforced PTFE
There is an alternate form of reinforced PTFE that is sometimes used in ball valve seals:  stainless steel reinforced PTFE.  This composite seal material is made of 50% teflon and 50% powdered 316 stainless steel.  Its temperature range is -20 F to 550 F (a bit higher than virgin PTFE) and it has higher pressure capabilities than either virgin or glass fiber reinforced PTFE.  It, too, is fire resistant, however its coefficient of friction is higher than PTFE. 
Key Material #4: PEEK
PEEK is an option when the requirements lay outside the temperature range of PTFE.  PEEK works well in environments with temperatures between -70 F to 600 F, and is unaffected by continuous exposure to steam and hot water.  It is tougher than teflon, but also harder.  Its major drawback, besides its rigidity, is its brittle behavior at lower temperatures. 
Key Material #5: UMHW Polyethylene
UHMW Polyethylene seems to be choice for more specialized applications, including those where there will be low to medium radiation exposure.  Its pressure rating is 1.5 ksi and its temperature range is -70 F to 200 F 1500 psi -57C to 93C. UHMW Polyethylene also has very good abrasion resistance. 
Key Material #6: Chlorinated Polyether
Chlorinated polyether is sometimes used as a ball valve seal material, functioning at temperatures up to 257 F.  It functions well in the presence of acids and solvents if softening can be tolerated, and is resistant to more than 300 chemicals.  It does not creep, and does not tend to absorb water.
Seals Continually Evolving:
Seal materials is a continually evolving field, but these six materials seem to be the leading contenders for thermoplastic ball valve seal choices.  Their major characteristics seem to the pressure and temperature performance, low friction, chemical resistance.
Tags:teflon ptfe,uhmw,ball valve seals