On June 28th, NSF Has processed the application for Registration of PFPE OIL TOPDA B-800 & B-1800 to the NSF International Registration Guidelines for Proprietary Substances and Nonfood Compounds (2021), which are available upon request by contacting NonFood@nsf.org. The NSF Nonfood Compounds Registration Program is a continuation of the USDA product apprroval and listing program, which is based on meeting regulatory requirements including FDA 21 CFR for appropriate use, ingredient and labeling review. 

This product is acceptable as a lubricant with incidental food contact (H1) for use in and around food processing areas. Such compounds may be used on food processing equipment as a protective anti-rust film, as a release agent on gaskets or seals of tank closures, and as a lubricant for machine parts and equipment in locations in which there is a potential exposure of the lubricated part to food. The amount used should be the minimum required to accomplish the desired technical effect on the equipment. If used as an anti-rust film, the compound must be removed from the equipment surface by washing or wiping, as required to leave the surface effectively free of any substance which could be transferred to food being processed. 

Perfluoropolyether(PFPE) was first studied in 1960s. It is a kind of special perfluoropolymer compound with average molecular weight ranging from 500 to 16000. There are only three elements in the molecule: C, F and O, the existing C-O and C-F bonds are highly stable. It has the features of excellent thermal resistance, oxidation resistance, radiation resistance, corrosion resistance and non-flammability, etc. It has been used as a very reliable lubricant in military, aerospace and nuclear industries for decades. Now perfluoropolyether(PFPE) is widely used in chemical industry, electronics, electrical appliances, machinery, nuclear industry, aerospace field.

According to the different monomers and polymerization methods, PFPE with different molecular structures of K, Y, Z and D types can be obtained.

The K-type structure is CF₃CF₂CF₂O [CF(CF₃)CF₂O]_nCF(CF₃)COF. It is a series of branched polymer formed by the polymerization of hexafluoropropylene oxide (HFPO) under the catalysis of CsF.

The Y-type structure is CF₃O (C₃F₆O)_m(CF₂O)_nCF₃. It is a polymer formed by photooxidation of hexafluoropropylene (HFP) under ultraviolet light. Its molecular weight is generally between 1000 and 10000.

The Z-type structure is CF₃(C₂F₄O)_m(CF₂O)_nCF₃. It is a linear polymer formed by photooxidation of tetrafluoroethylene (TFE) under ultraviolet light. Its molecular weight is generally between 1000 and 100000.

The D-type structure is C₃F₇O(CF₂CF₂CF₂O)_mC₂F₅. It is a polymer obtained by direct fluorination of the polymer product of tetrafluorooxyheterocyclic butane.

At present, there are two main synthesis methods of perfluoropolyether: photocatalytic polymerization and anionic catalytic polymerization.

1) Photocatalytic Polymerization

 It uses tetrafluoroethylene or hexafluoropropylene as raw materials, reacts with oxygen under ultraviolet irradiation at low temperature, and obtains polyethers with slightly different structures through oxidative polymerization. Taking tetrafluoroethylene as an example, besides acyl fluoride terminal group, there are unstable peroxide groups in the main chain of the crude product, which need to be eliminated by heating or illumination, and then stabilized by elemental fluorine. This method was commercialized in the 1960s. Its molecular structure is Y-type and Z-type.

2) Anionic Catalytic Polymerization

It uses Perfluoropropylene oxide(HFPO) as raw material, fluoride ion as catalyst in non-proton solvent, Perfluoropropylene oxide oligomer containing acyl fluoride terminal group can be obtained, and perfluoropolyether can be obtained by stabilization of its active acyl fluoride terminal group. This method was first commercialized in the 1970s. The main commodities are Krypton produced by DuPont Company in the United States and Demnum produced by Dajin Company in Japan (Dajin Company’s perfluoropolyether technology has been licensed by 12 national patents), and the molecular structure is K-type and D-type. 

In recent years, the global engineering plastics industry has developed rapidly, and is expected to grow to US$113.7 billion by 2020. By then, the global demand for engineering plastics will reach 29.1 million tons annually. Developing regions such as Asia, South America and the Middle East will be the main driving force for the growth of Engineering plastics. Over the past 10 years, the annual output value of engineering plastics in China has increased by more than 20%. At present, the annual production capacity of engineering plastics in China has reached 600,000 tons, and the annual output of modified engineering plastics has exceeded 2 million tons. Some products processing technology has entered the international advanced ranks.

Polytetrafluoroethylene (PTFE) is a a kind of fluorinated materials with excellent comprehensive properties. Engineering plastics modified by PTFE are mainly used in high-end applications. With the continuous improvement of social demand, the market potential of these products is huge.

Polytetrafluoroethylene (PTFE) is a fluorinated polymer material invented by Dr. Plunkett in the 1930s. Because of its excellent comprehensive properties, PTFE has the reputation of “King of Plastics”. The excellent performance of PTFE comes from its unique molecular structure. The structure formula of PTFE is [CF₂CF₂] _n. Hydrogen connected with carbon atom is replaced by fluorine atom. Under the protection of fluorine atom, PTFE has excellent properties of temperature resistance, radiation resistance, aging resistance, insulation, flame retardancy, adhesion resistance, self-lubrication and so on. It has been widely used in many fields.

Blending modification of engineering plastics by using the excellent properties of PTFE can complement each other’s advantages, further improve the properties of engineering plastics and expand their application fields. The modification of engineering plastics by PTFE blend modifier mainly concentrates on two aspects: anti-wear lubrication and anti-dropping flame retardant.

The chemical compositions of anti-wear lubricants and anti-dripping agents are both polytetrafluoroethylene. The difference is that the molecular weight of anti-wear lubricants is about 300,000, and that of anti-dripping agents is about 4-5 million. The addition of low molecular weight PTFE to plastics, rubber, coatings and other fields can significantly reduce the friction coefficient of the material surface, improve the wear resistance of the material itself, and play the role of internal lubrication and demoulding. Polytetrafluoroethylene (PTFE) with large molecular weight is fibrotic under the action of shear force of screw to form a network structure and play a role in anti-dripping.

1. Anti-wear lubricant 

Most engineering plastics have high surface friction coefficient and need external lubricants in sliding friction situations, which limits the application of engineering plastics in situations where external lubricants are not allowed to be used. Polytetrafluoroethylene (PTFE) has very low surface energy and excellent self-lubricating properties. By blending PTFE with engineering plastics, oil-free lubricating composites with low surface friction coefficient can be prepared.

Polytetrafluoroethylene (PTFE) superfine powder with molecular weight of 30,000-200,000 and average particle size of less than 30 microns is used as friction reducing lubricant for engineering plastics modification, also known as PTFE micro powder. The properties of PTFE powder, such as wide working temperature range, weather resistance, chemical stability, self-lubrication and non-stickiness, are exactly the same as those of high molecular weight PTFE resin. While maintaining the original properties, PTFE powder has the advantages of good dispersibility and easy mixing with other materials evently. It is an excellent modifier.

2. Anti-dripping agent

There are three main types of anti dripping agents: Pure powder type, emulsion type and coated type.

1). Pure powder type

Pure powdered anti-dropping agent is pure PTFE particles. The dispersion and fluidity of PTFE can be improved by sintering the surface of the particles. When the anti-dropping agent is premixed with plastics, it has better dispersing function and avoids early fibrosis.

The advantage of pure powder anti-dropping agent is that the content of PTFE is 100%, and it can be added in a large amount without any other impurities.

2). Emulsion type

The emulsion type anti dripping agent is made of polytetrafluoroethylene dispersed in water under the action of dispersant and made into a polytetrafluoroethylene dispersion emulsion. Because the emulsion contains a lot of water, it has higher requirements for the equipment and technology when used.

3). Coated Type 

Coated anti-dripping agent is a kind of polymer coated on the surface of PTFE particles, which makes it have better dispersion in the process of mixing plastic resin. The outer coated polymer is generally polyacrylonitrile, polystyrene and polymethyl methacrylate.

Compared with the pure powder and emulsion type anti dripping agents, the coated anti dropping agent has the advantages of good dispersibility, easy to use, no agglomeration at room temperature, easy to store, no crystal spots on the product surface, and high surface finish. However, the polymer coated on the outer layer of the final product belongs to impurities, which will have a certain impact on the performance of the product. In addition, the maximum dosage of coated anti dripping agent can only be 0.5%.