PTFE, FEP, PFA Recycling
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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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