PTFE, FEP, PFA Recycling
Browsing all articles in PTFE, FEP, PFA Recycling
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1. Introduction

The need of PTFE has increased over the years, which are used in industries such as automotive, medical, food packaging, household and personal care. They are generally opaque and have good heat resistant characteristics. PTFE can be recycled into many other products and used for rods, tubing and sheets. It can be sterilized by using autoclave, gas, dry heat and chemical disinfectant. The recycled PTFE is known technically as “Reprocessed” or “Repro” PTFE.

2. Recycling Process of PTFE

Recycling of PTFE became common in industries as there is no chemical reaction required. The PTFE scrap is grind into fine powder and then blend with pure PTFE that is used in compressions molding. To remove the inorganic compounds the scrap is first heated before grinding. Only the extruded forms can be recycled and separated from unwanted impurities and heated. Next it is put into a long strand, which is then cut down into small pallets and sent to industries that use as recycled material for their products.

Polytetrafluoroethylene’s (PTFE) ability to withstand extreme temperatures and harsh chemical environments makes it appealing for a number of applications but also makes it difficult to deal with in end-of-life, but not any more, according to 3M.

3M subsidiary Dyneon GmbH is currently constructing a PTFE recycling plant at an integrated production site located in southern Germany, with an annual capacity to recycle 500 metric tons of PTFE waste, converting it back to full-value raw materials.

Used in the chemical, automotive, semiconductor, and aerospace markets in a variety of applications, such as pumps, tapes, and automotive parts, PTFE presents a particular problem with regards to process waste.

An estimated 20,000 tonnes of waste are created annually during the processing of PTFE globally, according to 3M, and this waste material is currently either thermally degraded or land filled in special sites at a cost to the processor.

In 3M’s new process, PTFE waste materials will be heated in a reactor, split into their raw gaseous components, cleaned, and fed back into the production of new PTFE. At full capacity, 3M estimates that the process will save 10,000 tonnes of waste hydrochloric-acid, 7500 megawatt hours of energy, and subsequently 7500 tons of carbon dioxide emissions from being released annually into the atmosphere.

Global PTFE demand is forecast to be in excess of 240,000 tons, according to a Companies & Market report. PTFE has a 60% market share of the global fluoropolymer market-

3. Uses of Recycled PTFE

Most of the PTFE products are ground into powder which is used in inks, paints and cosmetics. Fiber filling for ski coats, fleece coat, polyester suits and more for cold areas is very prominent in developed countries. PTFE recycling reduces greenhouse gas emissions and save the environment. It’s even used for making plastic lumber, toys, park benches, car parts, drainage pipes and more. The recycled materials are graded as per plastic inputs by companies like ECO USA.

Process development of rubber compounds with PTFE micro powder in order to improve tribological properties (hot mold release agent ):

Based on PTFE chemistry, PTFE water-based release agent is designed to be ideal for molding of elastomers, including natural and synthetic rubber, EPDM, NBR, silicone, Viton and polychloroprene. The material is also suitable for most plastics and resins. The release agent activates at 212[degrees]F and is designed for application to molds which have been preheated to between 212[degrees]F and 550[degrees]F. There is no discernable transfer or migration from the mold coating to the molded part, according to the literature. A low coefficient of friction is said to provide outstanding lubricity. The product is non-flammable and is available in both aerosol and bulk liquid forms*).

4. Economic Conditions of PTFE Recycling

PTFE recycling appears to be economic, which saves about 7.4 cubic yards of landfill space. Its saves 12,000 BTU’s of heat energy by recycling one pound of plastic bottles. Oil consumption can also be reduced by recycling all the scrap plastics. The price of PTFE resins had reached some stability level globally.

Eco USA is a leading PTFE recycler who effectively removes PTFE scrap from your production line. The company is specialized in the development and production of high quality PTFE products. The company identifies three grades of PTFE scrap for specific uses.

Need of PTFE scraps has increased over the years, which are used in industries such as automotive, medical, food packaging, household and personal care. They are generally opaque and have good heat resistant characteristics. PTFE can be recycled into many other products and used for rods, tubing and sheets. It can be sterilized by using autoclave, gas, dry heat and chemical disinfectant. The recycled PTFE is known technically as “Reprocessed” or “Repro” PTFE.

5. Pricing of recycled PTFE

In recent times, the landscape of the PTFE industry has been significantly altered by the ascent of PTFE recycling. The combining of recycled PTFE (known technically as “Reprocessed” or “Repro” PTFE) with pure PTFE has become so widespread and unchecked that more often than not the material that customers are buying does not even remotely adhere to the quality standards required – due the abnormally high levels of repro being mixed in an attempt to keep costs low for the processor.

More alarming – processors and dealers alike are choosing not to offer the transparency to most clients on the proportion of recycled material being used (or that it is being used at all). This misleads the client into assuming he is receiving a material which is superior in performance – but which will most likely fail in any long run application. Additionally – processors who supply pure PTFE are forced to compete on price with a material that is not truly a substitute.

We would like to look at the issue of Reprocessed PTFE – both from the technical standpoint as well as a commercial standpoint. We believe the issue is critical to the understanding of the PTFE industry and as a technical tool for those looking to incorporate PTFE in their applications.

By 2010, the price for PTFE resins globally had reached some level of stability. Those in the industry will know that this was short-lived as one year on, we continue to work in oblivion to what price fluctuations may occur in the next week or month. However, it would be fair to say that even historically – the prices availed during the first half of 2010 may be the lowest that PTFE prices have ever sunk. Nonetheless, the competitiveness of pure PTFE processors was still not great.

In the few years leading up to 2010 (just before the current price escalation began) we began observing an obvious disconnect in India between the price of PTFE resins and the price of semi-finished articles (rods and sheets) being imported from China by traders.

The price for virgin PTFE resin was about 8-9 US$ per Kg (3.6-4.1 US$ per pound), whereas the price for Chinese semi finished articles was 10-11 US$ per Kg (4.5-5 US$ per pound).

Given that the processing cost for PTFE is about 4-5 US$ per Kg (1.8-2.3 US$ per pound) – it seemed there was no way that manufacturers in India could compete with traders on price. Obviously, clients were equally surprised, as they should have been; you would expect manufacturers to be far more competitive than dealers, but this was not the case.

It seemed impossible that the price could be so low, considering it would need to include the price of resin in China plus the cost of shipping, plus the customs duties on Indian imports, plus the trader’s overheads and finally the trader’s margin.

To study this pricing abnormality, a large enquiry to Chinese resin suppliers to gauge the local price in China and were offered a rate of 5.5 US$ per Kg (ex-works). If we used this as our base price (as we assume a large Chinese processor would avail such a price) and assumed the same costs of processing (not unlikely as India and China have similar wage structures and power costs), the cost structure for semi-finished PTFE could be built up as follows in the graph:

Article Sources:

Miller-Stephenson Chemical) from Rubber World,vol.1,1999
www.polyfluoroltd.com

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1. Introduction

Molecular formula: [CF2–CF2]n
CAS No. 9002-84-0

Pure PTFE in a very fine powdered form, this product is a superior substitute for talc and other lubricants commonly used on grand knuckles and keybeds. The knuckle is the single biggest source of friction in the grand action. Despite graphite or polymer coatings on the repetition lever, friction levels often remain high enough to adversely affect touch weight and cause squeaking. While dry lubricants such as talc or One-Puff will work to some degree, none are as effective or long-lasting as the correct grade of PTFE powder. The average particle optimum size is 3 microns.

PTFE powder is especially valuable when making touchweight measurements on grand actions, since it will typically reduce friction by about 2 grams compared to other lubricants, and virtually eliminates the static friction (reluctance of the action parts to start moving), so that you no longer have to tap the bench top to get the key moving when measuring downweight or upweight. Thus the job goes faster and your measurements are more consistent.

The virgin PTFE (polytetrafluoroethylene) powder is used for the applications to makerods, tubing etc. by paste extrusion. Its typical end products includes wire and cable insulating coating, linings, hoses, tubing, sleevings for use with heat, steam, hydraulic fluid, etc… Preferred for the extrusion processing with reduction ratios (i.e. RR) in the range 400 : 1 to 1500: 1. Typical products are extruded small tubing or rods, e.g. Ø 1.8 / 1.5 or Ø 0.9 / 0.5

2. Typical properties:

3. Safety precautions

• Toxic gases will be produced when the material is heated above 260 degree C. Ventilation system must be provided in sintering areas.
• Sintering temperature should be below 400 degree C to avoid decomposing.

4. Packaging, storage and transportation

• 20kg net packed in double PE plastic bags with a cardboard drum outside.
• Store in clean, cool (5-20 degree C) and dry place
• Open containers and use the material in clean environment only.

5. Powder types and chemical properties

POLYFLON PTFE F-104 produced by Daikin is used for the manufacture of unsintered tape, and tubes molded with a low reduction ratio; F-201 and F-203 are used for the manufacture of items molded with a high reduction ratio, such as insulated electric wires, spaghetti tubes, and small-diameter tubes. F-302 is a thick material with outstanding properties for secondary processing and thermal fusion of thick insulated electric wire, jacketing, medium to large diameter tubes and ingot tubes, etc.

POLYFLON PTFE can be used continuously at temperature up possesses excellent low temperature strength. With these superior thermal properties, products such as electric or electronic machinery components, pipe linings, insulated electric wires, etc., made with POLYFLON PTFE Fine Powder are widely used.

POLYFLON PTFE possesses the excellent property of almost absolute resistance to all commonly used chemicals. When used with some special chemicals under extremely severe conditions, such as fused alkali metals, changes may occur. With ordinary acids, alkalis, and oxidants at high temperatures POLYFLON PTFE remains completely stable. Even contact with organic compounds does not cause dissolution or swelling. The basic reason for POLYFLON PTFE‘s extensive use in the chemical industry for pipe linings, wire-braid hoses, gaskets, tubes and bellows is in its chemical inertness.

Since the molecular structure of POLYFLON PTFE is non-polar, it is ideal for use as high-frequency insulating material not only because of its applicability over a wide temperature range, but also because of its low, uniform dielectric constant and dissipation factor over a wide frequency range.

POLYFLON PTFE Fine Powder is used for the manufacture of insulation covering for use in aircraft, electrical wiring, small coaxial cables, industrial control cables, spaghetti tubes and wrapping tapes.

Tubes made of POLYFLON PTFE Fine Powder are therefore used as transport tubes for liquid adhesives, cableway pipes, etc., for automobile and other mechanical , being extremely soft and malleable. The many product gradesDuPont™Zonyl fluoroadditives are designed to provide just the right combinations of powder characteristics to meet the needs of diverse products and processes.

Zonyl® fluoroadditive powders are popular because they can contribute some of their unique properties to the host material to which they are added. However, the suitability of an additive powder for mixing with and enhancing a given host is determined by many other factors.

Zonyl® MP1100 fluoroadditive is a white, free-flowing PTFE powder designed for use as an additive in other materials to impart low surface energy and other fluoropolymer attributes. In particular, it has been found well suited for use in inks and coatings where a narrow particle size distribution is desired. With plastics and elastomers, it provides improved lubricity and wear resistance. Added to lubricants, it can enhance performance under severe conditions. Zonyl® MP1100 can be used at temperatures from –190 to 250°C (–310 to 480°F).

Zonyl® MP1200 fluoroadditive is a white, free-flowing PTFE powder designed for use as an additive in other materials to impart low surface energy and other fluoropolymer attributes. In particular, it has been found well suited for use in inks and coatings where a narrow particle size distribution is desired. With plastics and elastomers, it provides improved lubricity and wear resistance. Added to lubricants, it can enhance performance under severe conditions. Zonyl® MP1200 can be used at temperatures from –190 to 250°C (–310 to 480°F).

Zonyl® MP1300 fluoroadditive is a free-flowing, white powder designed for use as an additive in other materials to impart low surface energy and other fluoropolymer attributes. Zonyl® MP1300 may improve the wear resistance of host materials such as thermoplastics or coating materials and enhance their nonstick, lubricity, and frictional characteristics. Added to lubricants, it can enhance performance under severe conditions. Zonyl® MP1300 can be used at temperatures from –190 to 250°C (–310 to 480°F).

Zonyl® MP1400 fluoroadditive is a free-flowing, white powder designed for use as an additive in other materials to impart low surface energy and other fluoropolymer attributes. Zonyl® MP1400 may improve the wear resistance of host materials such as thermoplastics or coating materials and enhance their nonstick, lubricity, and frictional characteristics. Added to lubricants, it can enhance performance under severe conditions. Zonyl® MP1400 can be used at temperatures from –190 to 250°C (–310 to 480°F).

Zonyl® MP1600N fluoroadditive is a free-flowing, white powder designed for use as an additive in other materials to impart low surface energy and other fluoropolymer attributes. Zonyl® MP1600N may improve the wear resistance of host materials such as thermoplastics or coating materials and enhance their nonstick, lubricity, and frictional characteristics. Added to lubricants, it can enhance performance under severe conditions. Zonyl® MP1600N can be used at temperatures from –190 to 250°C (–310 to 480°F).

Zonyl® TE-3887 PTFE fluoroadditive is a negatively charged, hydrophobic colloid containing approximately 60% (by total weight) of 0.05 to 0.5 µm polytetrafluoroethylene (PTFE) resin particles suspended in water. A milky white liquid, Zonyl® TE-3887 also contains approximately 6% (by weight of PTFE) of a nonionic wetting agent and stabilizer. Viscosity at room temperature approximately 20 cP. Nominal pH is 10.

PTFE white granular molding powders are ideal for molding many different end products and stock shapes. Excellent chemical resistance, electrical properties, high temperature performance, low temperature toughness, plus unique adhesion and flame resistance.

PTFE granular molding powders are processed by compressing them into a desired shape and heating them at temperatures above their melting point to consolidate the powder.

Resin Characteristics: High bulk density. These small particles result in the highest quality electrical and mechanical properties of all PTFE granular molding powders. Uses: Large cylinders for making tape or sheet by skiving; large shapes for machining or direct use.

Powder coating is an economical and environmentally friendly method of applying decorative and protective finishes to a wide variety of materials and products that are used by industry and consumers.
Some industries where powder coatings are used include General Industrial Products, Consumer Products, Appliances, Agriculture & Construction Equipment (ACE), Architectural, Automotive, and Pipe & Valve.
Powder coatings are available in virtually unlimited colors and include high or low gloss, matte, textured, vein, and wrinkle finishes. Coatings with FDA, NSF, and UL approvals are available. A complete line of RAL colors is available and custom colors can be formulated when needed.

For instance Plas-Tech applies powder finishes from the following suppliers:

• DuPont Coating Solutions
• Tiger Drylac
• Sherwin-Williams
• Rohm and Haas
• Cardinal Industrial Finishes
• Arkema
• Peridium by DiamondVogel
• Plascoat
• Protech Powders
• Solvay Solexis

6. Benefits of Powder Coatings

• Attractive, durable, high-quality finish
• Cost effective compared to liquid coatings
• Environmentally friendly- virtually pollution free, NO VOC’s
• Consistent coating thickness; both thin and thick films
• Corrosion resistance
• Virtually any color or gloss
• Matte finishes and wrinkle coats can hide surface defects or imperfections such as spot welds, nicks & scratches

7. Types of Powder Coatings

• Polyester
• TGIC Polyester
• Epoxy
• Hybrid (Epoxy/Polyester)
• Urethanes
• PVDF (Polyvinylidene Fluoride)
• Nylon II (Polyamides)
• Polyolefins (polyethylene & polypropylene resins)
• Halar (ECTFE)
• Fluoropolymers (PFA, FEP, & ETFE)

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PTFE Micro-Powder Recycling

1.Introduction

PTFE can be reprocessed in a fashion similar to other thermoplastics. Due to its high melt viscosity, it is difficult to remelt it and mix with virgin material, particularly if it contains mineral fillers. Currently, most PTFE scrap ( mainly residues from machining operations ) is processed by radiation, being exposed to high doses up to 400 kGy in order to reduce drastically the molecular weight and to obtain micropowders. High-molecular weight PTFE can also be converted into micropowders by thermal or shear degradation.

2. Micropowder production process

As one of the world’s leading producer of PTFE micropowders, we’ve created a standard for PTFE micropowder products leading the industry in recycling PTFE and developing new applications by designing PTFE micropowders that deliver optimal performance for specific target applications.

Our core business is the manufacture of prime PTFE micropwders and offers the industry’s broadest number of products. Their engineered solutions fit customers’ unique applications by controlling:

• PTFE type
• Particle size
• Dispersibility
• Molecular weight
• End groups

FLT( Fluoro-T) is a clean, recycled PTFE powder that offers a more attractive alternative to costly virgin PTFE. Not only is Fluoro-T a better value, but as confirmed in recent independent testing, Fluoro-T 2.0 offers superior coefficient of friction and wear resistance in both nylon and acetal (POM).

Dyneon™ PTFE Micropowders produced by 3M are white, fine- particle powders of low molecular weight polytetrafluoroethylene (PTFE). Micropowders are used as additives in a variety of applications to improve the non-stick and antifriction properties of the matrix materials.

PTFE Micropowders can be used as additives in many applications and at concentrations typically from 5 to 20%. Homogeneous incorporation is the single most important process and application consideration. Due to poor flow properties of the micropowder it is recommended that the micropowder and matrix material both be at a temperature below 30°C (86°F). However, in the case of thermoplastic blends, the micropowder may be incorporated into the melt.

Dyneon PTFE Micropowder J14 can be dispersed using a variety of mixing equipment. Depending upon the application, high speed mixers and tumble blenders have been successful for dry blends, while propeller mixers work well for wet mixtures such as solvents and oils. Glass bead mills should be used for relatively high viscosity mixtures and roll mills for very high viscosity applications, such as lubricating greases and oils.

Typical Properties Property Test Method of the micropowder:

Average Particle Size Laser Diffraction 6 μm
Hegman Particle Size Grind Gauge 2 μm
Minimum Bulk Density ASTM D4895 250 g/l

3. Properties

Typical Applications of PTFE micropowder
• Inks
• Lubricants
• Paints
• Coatings
• Waxes
• Greases
• Storage

PTFE micro powder is applied widely in coatings, inks, plastics, elastomers, oils and greases. It’s made from polytetrafluoethyelene resin (PTFE, CAS No. 9002-84-0) that has been micronized to a particle size range between 20-50 microns. This micro-powder can enhance abrasion resistance, reduce coefficient of friction and mechanical wear, reduce surface contamination and modify appearance.

It improves wear resistance and reduces friction of plastic products and improves tear and abrasion resistance of elastomers. Inks can be formulated for better image protection and higher productivity. PTFE micro-powder can be used in a paste or a spray and even as an all purpose solid dry lubricant. The powder can be dispersed in water and organic solvents.

Additive to lubricants & greases

1. Used as an ingredient, to formulate lubricating systems respectively used under lower load at lower rpm, under medium load at medium rpm, and under heavy load at high rpm.

Recommended usage: 0.5~7.0 % (by wt.)

2. Being added into lubricating oils and greases to improve the lubricating performance under high pressure, and as well to increase the viscosity of the base oils.

Recommended usage: 0.5~40.0 % (by wt.)

Additive to thermoplastics, thermoset plastics, and elastomers

Being added in PC, POM, PA, PPS, ABS, PS, HIPS, PP, thermoset plastics and elastomers ( EPR, silicone rubber, SBR etc.), it can obviously reduce the attrition to the sliding parts, and the friction coefficient of the base substance.

Recommended usage: 5~25.0 % (by wt.)

Additive to printer’s inks

It’s an ideal additive and modifier to various kinds of printer’s inks that achieves anti-sticking, less abrasion, improved definition and luster of the prints, durability against fading, good water-proof and moth-eaten proof, etc.. Its application in hectograph / gravure inks improves slippery performance, surface smoothness, luster and abrasion resistance that facilitates high-speed printing.

Recommended usage: 0.1 ~ 3.0 % (by wt.)

Additive of paints

It can be mixed with paints used in spray coating of industrial equipment, household goods, or used in anti-corrosion paints, special waterproof paints, and coating of wound metal strips providing benefits of anti-stickiness, flexibility, heat conductivity, durability and toner resistance etc.

Additive of anti-sticky and wear-resisting varnish

To improve the varnish’s properties of anti-sticky, lubricating, anti-corrosion, moisture-proof and wear resistance, also reduce its friction coefficient.

As an solid lubricant

1. Being added into rubbers and plastics, it can not only avoid sticky-sliding during processing, but also give the base materials with excellent properties of PTFE. It’s also a quite effective mould-release agent for rubbers and plastics when the powder being mixed in at 0.25% by wt.
2. Used as a lubricant for gearing system in the circumstances that requires oil-free lubrication, such as high-speed engines, gearing system, and kneading machine, etc.
3. Added in oils, lubricating oils and rubber sealant to significantly improve their load-bearing capability, vacuum resistance, low temperature resistance and wear resistance.

Anti-sticky and wear-resistant spray

A spray could be made by mixing it with methane and butane to make the sprayed base substances with improved adhesion resistance and wear resistance.

Additive to dry battery

Used in dry battery to substitute PTFE dispersion. It can elongate the life of the battery, simplify the production technic and lowdown the cost.

4. Recycling

The use of reprocessed ( reground) PTFE resin has limitations, because it exhibits markedly lower tensile strength and elongation values in respect to virgin PTFE. Preprocessed material creeps up to 25% more than virgin resin and contains twice the void content. Because of the porosity and larger number of voids, its dielectric strength is lower than that of the virgin PTFE. Thus, the use of reground(reprocessed) material is limited to such applications where cost is an important consideration and where lower performance is sufficient for the application.

Eco USA has various options for recycling PTFE micropowder. These options depend upon the nature and amount of the scrap destined for recycle.

Eco USA collects the scrap for recycling and then processes it into a form suitable for re-use.

In recycling process the consistency is ensured by the process design as follows:

• Stringent qualification of all PTFE sources
• Grading, sorting and cleaning to ensure product quality
• Patented irradiation techniques deliver outstanding product consistency
• Proprietary micronization techniques have been developed specifically for PTFE micropowders

Article Sources:

Technology of Fluoropolymers, Second Edition

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PFA Recycling | Recycle PFA

1. Introduction

PFA is a perfluoroalkoxy copolymer resin available in pellet or powder. PFA combines the processing ease of conventional thermoplastic resins with the excellent properties of PTFE (polytetrafluoroethylene).

It differs from the PTFE resins in that it is melt-processable using conventional injection molding and screw extrusion techniques. PFA was invented by DuPont. Other brandnames for granules are Neoflon PFA from Daikin or Hyflon PFA from Solvay Solexis.
Products manufactured from PFA can offer continuous service temperatures up to 260°C (500°F). What’s more, PFA provides superior creep resistance at high temperatures, excellent low-temperature toughness, and exceptional flame resistance.

PFA melts at 280°C minimum and is melt processable. Some grades are chemically stabilised. It is available in the form of translucent pellets, powder, and as an aqueous dispersion.
The PFA fluoropolymer resins are processed by conventional melt-extrusion techniques and by injection, compression, rotational, transfer, and blow-molding processes. The high melt strength and heat stability of these resins permit the use of relatively large die openings and high-temperature draw-down techniques, which increase processing rates. Reciprocating screw injection molding machines are recommended. Corrosion-resistant metals should be used in contact with the molten resin. Long extruder barrels, relative to diameter, are used to provide residence time for heating the resin to 316° to 427°C (600° to 800°F).

2. Chemistry

PFA fluorocarbon resin is a copolymer of tetrafluoroethylene and a perfluorinated vinyl ether having the formula [(CF(ORf)-CF2)m(CF2 -CF2 )n ]x, where ORf represents a side chain perfluoralkoxy group

3. Properties

The following characteristics contribute to the unique properties of PFA fluorocarbon resins:

• Nonpolarity: The carbon backbone of the linear polymer is completely sheathed by the electron cloud of fluorine atoms, much like a wire core is protected by insulation coating. This ensheathment, and the angles at which the carbon-fluorine bonds are disposed, causes the centers of electronegativity and electropositivity to be perfectly balanced across the polymer chain cross section. As a result, no net charge difference prevails. This nonpolarity of the polymer is partly responsible for its lack of chemical reactivity.

• Low interchain forces: The bond forces between two adjacent polymer chains are significantly lower than the forces within one chain. PFA PTFE linear polymer chains are otherwise restrained. However, in PFA FEP and PFA, interpolymer chain entanglement of the pendant structure precludes the shifting of polymer chains to relieve the implied load. The “creep” normally associated with PFA PTFE is mostly avoided with PFA FEP and even more so with PFA.

• High C-F and C-C bond strengths are among the strongest in single bond organic chemistry. The polymer must absorb considerable energy to disrupt these bonds. Chemical reactions represent a kinetic and thermodynamic resolution of bond-making and bond-breaking in favor of the most stable system. These bond strengths are hard to overcome.

• Crystallinity: The high degree of crystallinity in these semicrystalline polymers results in high melting points, mechanical properties, and an integral barrier to migrating, small, nonpolar molecules. Under certain conditions, these molecules penetrate the plastics.

• High degree of polymerization: The unbranched nature of the polymers and their low interpolymer chain attraction requires very long chain lengths in PFA PTFE and entanglement in PFA FEP and PFA to provide load-bearing mechanical properties. The chain length also has an impact on the flow and crystallinity of the polymers. These unique properties lead to the following benefits:

• High melting points (327°C [621°F] for PFA PTFE; and 305°C [582°F] for PFA). The melting point of PFA PTFE is one of the highest in organic polymer chemistry. Other materials can attain higher temperatures, but they degrade rather than melt. In PFA, a higher degree of polymerization, enhanced entanglement of the pendant structure and lower comonomer content combine to provide a melting point closer to that of PFA PTFE.

• High thermal stability: Due to the strength of the carbon-fluorine and carbon-carbon single bonds, appreciable thermal energy must be absorbed by the polymers before thermal degradation. The rate of decomposition of a part of PFA depends on the particular resin, temperature, and heat exposure time; and to a lesser extent, pressure and nature of the environment. At maximum continuous service temperatures, thermal degradation of the resins is minimal.. At high processing temperatures, adequate ventilation is recommended.

• High upper service temperature (260°C [500°F] for PFA PTFE and 260°C [500°F] for PFA). The polymers’ high melting points and morphological features allow components made from the resin to be used continuously at the stated temperatures. Above this temperature, the component’s physical properties may begin to decrease. The polymer itself, however, will be unaffected if the temperature is insufficient for thermal degradation.

• Insolubility: There is no known solvent for PFA fluorocarbon resins under ordinary conditions.

• Inertness to chemical attack: The intrapolymer-chain bond strengths preclude reaction with most chemicals. Under relatively unusual circumstances the polymer can be made to react. Examples of unusual reagents include:
– Sodium, in a suitable media, etches the fluorocarbon polymer.
– Finely divided metals often interact with the polymer.
– Interhalogen compounds often induce halogen interchange with the fluorine.
– Ionized oxygen in oxygen plasma is often sufficiently energetic to react with the polymer chain.
– Electron bombardment at the megarad level can sever the polymer chain.

• Low coefficient of friction: The low coefficient of friction of PFA results from low interfacial forces between its surface and another material and the comparatively low force to deform.

• Low dielectric constant and dissipation factor: PFA provides low, if not the lowest, values for these parameters. These low values arise from the polymer’s nonpolarity as well as the tight electron hold in the ultrapolymer bonds.

• Low water absorptivity: For PFA to absorb water, the surface must remain wet for a long enough time for water to become physico-chemically associated with the polymer chains, and then it must become included in the polymer bulk structure. Water is a very high energy material and PFA has a very low surface energy. Therefore, these events are energetically incompatible and only occur under special circumstances and to a small extent.

• Excellent weatherability: Weather includes light of various wavelengths (IR, visible, UV), water (liquid or gas), other gases, and normal temperatures and pressure. The physical and chemical makeup of PFA makes it inert to these influences.

• Flame resistant: PFA will burn when exposed to flame, but will not continue to burn when the flame is removed.

• Excellent toughness: Some mechanical properties of PFA resins are shown in Table 1. Toughness characteristics are high and differ somewhat between resin types.

4. Recycling

4.1. PFA Scraps Recycling

Eco USA has various options for recycling PFA polymer. These options depend upon the nature and amount of the scrap destined for recycle. There are three options for recycling this fluoropolymer: reprocessing, recovery or disposal.
Eco USA collects the scrap for recycling and then processes it into a form suitable for re-use. The PFA scraps can be reprocessed as thermoplastics provided following analyses are performed:

– Checking melt index
– Contamination quantified
– Thermal stability verified
– DSC analysis and other testing

Thermoplastics are easily recyclable, compared to thermosets, because the polymer chain does not degrade when melted down. This is because the weaker interactions between polymer chains break down at much lower temperatures than the chemical bonds between monomers. This allows thermoplastics to be recycled indefinitely until the polymers are broken down to the point that the material loses structural integrity.

Thermoplastics have a limit recyclable lifespan due to degradation of the polymers and contamination during the recycling process. Contaminants can be inert materials, which act as fillers, or they can be other plastics, which alters the physical properties of the resulting material.

4.2. Recovery and Disposal of Fluoropolymer Waste (i.e. PFA)

Recovery

Fluoropolymers are usually employed in small components in specific complex applications such as electronic equipment, transport (cars, trains and airplanes) or as very thin layer coatings on fabrics and metals. Where sufficient quantities of fluoropolymers can be recovered and may be sufficient to warrant recycling then they should be shipped to specialist recyclers.

A very substantial market exists for recovered fluoropolymers as low friction additives to other materials. For example PTFE and/or PFA are typically ground into fine powders and used in such products as inks and paints. In this scenario Eco USA is finding the new user for a still usable product.

Disposal

Fluoropolymer waste should be incinerated in authorized incinerators. Preferably, non-recyclable fluoropolymers should be sent to incinerators with energy recovery. Disposal in authorized landfills is also acceptable.

Decomposition products:

According to the fire conditions toxic gasses develop, predominantly carbon dioxide, carbon monoxide, hydrofluoric acid, tetrafluoroethylene, hexafluoropropylene, perfluorisobutylene, carbonyl fluoride and other low-molecular fluorohydrocarbons.

Article Sources:
1) Fluoropolymers,Vol.2, 1999
2) Du Pont notes about fluoropolymers

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1. Introduction
FEP offers excellent chemical inertness, heat and weather resistance, exceptional electrical properties, toughness and durability

2. Chemistry:

FEP is a copolymer of tetrafluoro-ethylene and hexafluoropropylene with the following structure:

2.1. Commercial trade names:

FEP by Du Pont, Dyneon™ by 3M and Neoflon by Daikin

2.2. Advantages:

Very high impact strength. Excellent high frequency electrical properties. Melt processable. Good weathering resistance.

2.3. Disadvantages:

Very expensive, with the lowest strength and stiffness of all the fluoro plastics. Low HDT at 50°C (120°F) accompanied by poor wear resistance.

3. Properties:

The following characteristics contribute to the unique properties of FEP fluorocarbon resins:

• Nonpolarity: The carbon backbone of the linear polymer is completely sheathed by the electron cloud of fluorine atoms, much like a wire core is protected by insulation coating. This ensheathment, and the angles at which the carbon-fluorine bonds are disposed, causes the centers of electronegativity and electropositivity to be perfectly balanced across the polymer chain cross section. As a result, no net charge difference prevails. This nonpolarity of the polymer is partly responsible for its lack of chemical reactivity.

• Low interchain forces: The bond forces between two adjacent polymer chains are significantly lower than the forces within one chain. The “creep” normally associated with PFA PTFE, due to the interpolymer chain entanglement of the pendant structure, is mostly avoided with PFA FEP..

• High C-F and C-C bond strengths are among the strongest in single bond organic chemistry. The polymer must absorb considerable energy to disrupt these bonds. Chemical reactions represent a kinetic and thermodynamic resolution of bond-making and bond-breaking in favor of the most stable system. These bond strengths are hard to overcome.

• Crystallinity: The high degree of crystallinity in these semicrystalline polymers like FEP results in high melting points, mechanical properties, and an integral barrier to migrating, small, nonpolar molecules. Under certain conditions, these molecules penetrate the plastics.

• High degree of polymerization: The unbranched nature of the polymers and their low interpolymer chain attraction requires very long chain lengths to provide load-bearing mechanical properties. The chain length also has an impact on flow and crystallinity of the polymers. These unique properties lead to the following benefits:

• High melting points (327°C [621°F] for PFA PTFE and 260°C [500°F] for PFA FEP). The melting point of PFA PTFE is one of the highest in organic polymer chemistry. Other materials can attain higher temperatures, but they degrade rather than melt. Compared to PFA PTFE, the lower melting temperature of PFA FEP results from lower crystallinity.

• High thermal stability: Due to the strength of the carbon-fluorine and carbon-carbon single bonds, appreciable thermal energy must be absorbed by the polymers before thermal degradation. The rate of decomposition depends on the particular resin, temperature, and heat exposure time; and to a lesser extent, pressure and nature of the environment. At maximum continuous service temperatures, thermal degradation of the resins is minimal. For example, at 400°C, PFA FEP is measured at 4/100,000 of 1 percent, and PFA PTFE at 1/100,000 of 1 percent. At high processing temperatures, adequate ventilation is recommended.

• High upper service temperature ( 204°C [400°F] for PFA FEP) -The polymers’ high melting points and morphological features allow components made from the resin to be used continuously at the stated temperatures. Above this temperature, the component’s physical properties may begin to decrease. The polymer itself, however, will be unaffected if the temperature is insufficient for thermal degradation.

• Insolubility: There is no known solvent for FEP fluorocarbon resins under ordinary conditions.

• Inertness to chemical attack: The intrapolymer-chain bond strengths preclude reaction with most chemicals. Under relatively unusual circumstances the polymer can be made to react. Examples of unusual reagents include:
– Sodium, in a suitable media, etches the fluorocarbon polymer.
– Finely divided metals often interact with the polymer.
– Interhalogen compounds often induce halogen interchange with the fluorine.
– Ionized oxygen in oxygen plasma is often sufficiently energetic to react with the polymer chain.
– Electron bombardment at the megarad level can sever the polymer chain.

• Low coefficient of friction: The low coefficient of friction of FEP results from low interfacial forces between its surface and another material and the comparatively low force to deform.

• Low dielectric constant and dissipation factor: FEP provides low, if not the lowest, values for these parameters. These low values arise from the polymer’s nonpolarity as well as the tight electron hold in the ultrapolymer bonds.

• Low water absorptivity: For FEP to absorb water, the surface must remain wet for a long enough time for water to become physico-chemically associated with the polymer chains, and then it must become included in the polymer bulk structure. Water is a very high energy material and FEP has a very low surface energy. Therefore, these events are energetically incompatible and only occur under special circumstances and to a small extent.

FEP Typical Properties
Property Value
Density (g/cm3) 2.1
Surface Hardness RR45
Tensile Strength (MPa) 14
Flexural Modulus (GPa) 0.6
Notched Izod (kJ/m) 1.06+
Linear Expansion (/°C x 10-5) 5
Elongation at Break (%) 150
Strain at Yield (%) 6
Max. Operating Temp. (°C) 150
Water Absorption (%) 0.01
Oxygen Index (%) 95
Flammability UL94 V0
Volume Resistivity (log ohm.cm) 18
Dielectric Strength (MV/m) 50
Dissipation Factor 1kHz 0.0002
Dielectric Constant 1kHz 2.1
HDT @ 0.45 MPa (°C) 70
HDT @ 1.80 MPa (°C) 50
Material. Drying hrs @ (°C) NA
Melting Temp. Range (°C) 340 – 360
Mould Shrinkage (%) 2.5
Mould Temp. Range (°C) 50 – 200

Applications

Coatings, protective linings, chemical apparatus, wire coverings, glazing film for solar panels.

4. Recycling

Eco USA has various options for recycling FEP polymer scraps.These options depend upon the nature and amount of the scrap destined for recycle. There are two options for recycling the fluoropolymer: re-use or disposal in authorized incinerators.

Various fluorine-containing polymers, especially fluorinated ethylene propylene (FEP), are increasingly common in data wiring insulation because of their exceptional dielectric properties, superb flame resistance, heat resistance, chemical inertness, durability, and flexibility.

For plenum-rated data cable, FEP-insulated wire is often the only option allowed by code, due to fire-safety concerns. Such wire is often wrapped in a PVC jacket, though newer, more stringent “limited combustible” ratings require FEP jacketing. In addition to these performance benefits of FEP, the polymer can be recycled easily, according to DuPont.

Thermoplastics are easily recyclable, compared to thermosets, because the polymer chain does not degrade when melted down. This is because the weaker interactions between polymer chains break down at much lower temperatures than the chemical bonds between monomers. This allows thermoplastics to be recycled indefinitely until the polymers are broken down to the point that the material loses structural integrity.

Thermoplastics have a limit recyclable lifespan due to degradation of the polymers and contamination during the recycling process. Contaminants can be inert materials, which act as fillers, or they can be other plastics, which alters the physical properties of the resulting material.

Eco USA collects the scrap and then processes it into a form suitable for re-use.

4.1. Recovery

A very substantial market exists for recovered fluoropolymers as low friction additives to other materials. For example PTFE FPA or PFA FEP are typically ground into fine powders and used in such products as inks and paints.

4.2. Disposal

Fluoropolymer waste should be incinerated in authorised incinerators. Preferably, non-recyclable fluoropolymers should be sent to incinerators with energy recovery. Disposal in authorised landfills is also acceptable.

Decomposition products:

According to the fire conditions toxic gasses develop, predominantly carbon dioxide, carbon monoxide, hydrofluoric acid, tetrafluoroethylene, hexafluoropropylene, perfluorisobutylene, carbonyl fluoride and other low-molecular fluorohydrocarbons.

Some significant environmental and health concerns have arisen about the whole class of fluoropolymer materials. FEP does not burn easily, but it can emit toxic gases when it gets very hot, even without actual combustion. The primary gas emitted is hydrogen fluoride, which is more dangerous than the hydrogen chloride given off by PVC. Other toxic chemicals can be given off by FEP during fires; these poorly understood thermal degradation products have been referred to collectively as “the supertoxin”.

Article Sources:

1) Fluoropolymers, Vol.2, 1999
2) Du Pont notes on fluoropolymers

0

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
www.plasticsnews.com/pmd2012

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