Sliding properties

Micropowders are added to a wide variety of material used in industry, where they provide nonstick and sliding properties. They are incorporated into the product by blending and grinding. To disperse weU, the powder must have good flow properties. Conditions that make the powder sticky should be avoided. 

Micropowders, PTFE homopolymers with molecular weight significantly lower than normal PTFE, are commonly used as additives in a large number of applications where they provide nonstick and sliding properties. They are added to plastics, inks lubricants, and lacquers.14... 

Table 7.7. Another method of producing PTFE micropowders is by controlled polymerization of TFE to a lower molecular weight [105]. Fluoroadditives are used as additives for plastics, elastomers, coatings, printing inks, paints, lacquers and lubricants, where they provide nonstick and/or sliding properties [106]. Benehts provided by PTFE micropowders are summarized in Table 7.8 [107].

Sewing thread lubricants based on silicone have been tried and proven in final finishing of sewing thread to Improve the sliding properties and to Improve their resistance to heat. The sewability is improved, the number of thread breaks reduced and the lustre of the sewing improved. 

Chemical conversion coating Surface for painting, corrosion resistance, sliding property... 

Polymers can be used in the sliding parts of joints. Poly(tetrafluoroethy-lene) (PTFE) was proposed, thanks to its excellent sliding properties. However, PTFE does not resist friction under compression and is rapidly crushed, leading to loosening of the prosthesis. Ultra-high-density polyethylene is used in the hip when the head of the femoral part is made of stainless steel, and in the joint of the tibia in the knee prosthesis. 

For materials used in the propulsion elements, control units, or landing gear, good electrical and thermal properties are essential. Controlled fire behavior, low fume toxicity, good sliding properties, and high chemical resistance are also requiranents. 

Moisture, weathering resistant resins (vanishes) Chemical-resistant resins (lining materials, etc.) Abrasion-resistant resins (coating materials) Insulating resins (sealing compounds) Fire-resistant resins (vanishes) Pressure-sensitive adhesive resins Spherical powders (improvers to blocking and sliding properties for films)... 

The bronzes have a much lower thermal conductivity in comparison to the most commonly used copper alloys (CuCoNiBe/CuBe/CuNiSiCr) however, they also have excellent sliding properties, which make them an excellent material both for guide elements as well as for forming mold inserts. Low alloyed copper alloys are always the first choice when it comes to using a material with a high thermal conductivity and good mechanical properties. 

Mainly the improvement of the sliding properties of moving mold elements should be mentioned as areas of application of the above illustrated surface and coating technologies (Figure 5.35). PVD coatings based on carbon, tungsten, or molybdenum, chemical nickel-polytetrafluoroethylene (FIFE) layers, or so-called beam treatments... 

ECTFE with good sliding properties. This section is followed by a lantern ring that is used for purging and therefore, in a way, for lubrication and cooling of the piston. Next to this is placed a series of low-compression seals. The piston is hardened and characteristically lean for the accomplished pressure level in order to keep the driving forces low. 

The actual sliding layer consists of a conq)Ound of two materials exhibiting physical and mechanical properties which strongly differ firom each other. The con ressive strength of the conpound bearing material is ensured by the thin porous sintered bronze layer, whereas the good sliding properties result from the PTFE/soKd lubricant mixture. To en-... 

Oyama H and Nakaishi E (2003) Thermoplastic elastomer compositions, moldings and automobile interior parts therefrom with high wear resistance and good sliding property, Jpn Kokai Tokkyo Koho JP 2003,277,519, to Sumitomo Chem Co, Ltd. Ikeda Y, Kodama K, Kajiwara K and Kohjiya S (1995) Chemical modification of butyl rubber. II. Structure and properties of poly(ethyleneoxide)-grafted butyl rubber, J Polym Sci Part B Polym Phys Ed 33 387-394. 

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