Additives external lubricants

Anionic Antistats Anionic antistats for PVC include sodium salts of alkyl sulfonates and phosphates. These additives are, in addition, external lubricants. In some cases, their inclusion may boost stabdizer activity (as with lubricants in general). Generally, their use poses less of a hazard to heat stabUity than amine salts of strong acids. At more than trace levels, adjustments to the overall stabilizer and lubricant package are usually needed. Usage with barium or lead must also be checked, as noted above, for unexpected effects. 

Poly(ethylene terephthalate). PET is a crystalline material and hence difficult to plasticize. Additionally, since PET is used as a high strength film and textile fiber, plasticization is not usually required although esters showing plasticizing properties with PVC may be used in small amounts as processing aids and external lubricants. Plasticizers have also been used to aid the injection mol ding of PET, but only at low concentrations. 

Substituted Amide Waxes. The product of fatty acid amidation has unique waxlike properties (13). Probably the most widely produced material is N,1S7-distearylethylenediarnine [110-30-5] which has a melting point of ca 140°C, an acid number of ca 7, and a low melt viscosity. Because of its unusuaHy high melting point and unique functionaHty, it is used in additive quantities to raise the apparent melting point of themoplastic resins and asphalts, as an internal—external lubricant in the compounding of a variety of thermoplastic resins, and as a processing aid for elastomers. 

Laboratory tests and experience during use have demonstrated that the nylons have extremely good abrasion resistance. This may be further improved by addition of external lubricants and by processing under conditions which develop a highly crystalline hard surface e.g. by use of hot injection moulds and by annealing in a non-oxidising fluid at an elevated temperature (150-200°C for nylon 66). 

Alkanesulfonates act as an external lubricant in PVC, polystyrene, and engineering thermoplastics. They have a good release effect and assist flow. Addition is in the concentration range between 0.1 and 2.0 parts per 100 parts resin (phr). Because of their low volatility, alkanesulfonates are also used as a processing aid for high-melting engineering thermoplastics. 

Saturated hydrocarbons (waxes), fatty acids, metal soaps, fatty acid amides and esters (primarily Cig-Cis) act as internal lubricants, fluoro elastomers as external lubricants. Many other polymer additives, e.g. antistatic agents, antifogs, antioxidants, UV stabilisers, etc., act as lubricants in the barrel of the extruder once they are in the liquid form. 

Otsuka, M., Sato, M., and Matsuda, Y. (2001), Comparative evaluation of tableting compression behaviors by methods of internal and external lubricant addition Inhibition of enzymatic activity of trypsin preparation by using external lubricant addition during the tableting compression process, AAPS PharmSci, 3(3), article 20. 

Typical strongly external lubricants are paraffin wax, polyethylene wax, oxidised polyethylene wax and stearic acid. Typical strongly internal lubricants are glycerol esters and fatty acids. Calcium stearate functions somewhere between internal and external, depending on addition level. It also acts as an acid scavenger. 

In flexible PVC film, waxes and low molecular weight polyethylene are often used as external lubricants, and fatty acids, esters, and metallic soaps are often used as internal lubricants. As the names suggest, external additives, including lubricants, are applied to the surface of the film or other plastic article, while internal lubricants are blended Into the polymer before it is formed. 

Stickiness is the ability of a rubber compound to stick to a nonrubber surface such as a metal or textile fabric surface. Excessive stickiness to metal can result in poor release from mills and problems in process equipment. On the other hand, the destruction of compound stickiness can cause slippage of the compound against metal surfaces in extruders or the rotors of an internal mixer. Various compounding additives, such as mill release agent.s or external lubricants, are used to control the level of stickiness. Note, compound stickiness and tackiness are not the same property. 

In plasticized PVC it is common practice to incorporate a lubricant whose main function is to prevent sticking of the compound to processing equipment [14]. The material used should have limited compatibility such that it will sweat out during processing to form a film between the bulk f the compound and the metal surfaces of the processing equipment. The additives used for such a purpose are known as external lubricants. 

Nylons have extremely good abrasion resistance. This property can be further enhanced by addition of external lubricants and by providing a highly crystalline hard surface to the bearings. The surface... 

Whereas oil-air lubrication basically allows no heat to be dissipated from the bearing via the lubrication medium or the air stream, oil jet lubrication utilizes the volumetric flow of the lubricant to cool the bearing. This method produces considerably more lubricant friction than is the case with other lubrication variants. Neverteheless, combined with sufficient cooling it also yields the highest d factors, that is, up to 4 10 mm/min (Brandlein 1995). As it is the case for all other lubrication methods with external lubricant supply, a disadvantage is the expenditure required for additional components such as pumps, seals, and oil lines. 

Melt fracture where the critical shear stress of polymer (about 0.1 to 0.4 MPa) exceeded in the die excessive shear stress at the wall >0.1 MPa] exit speed at the die is too fast/melt too cold/throughput excessive/die land too short/die opening too small/entrance to die not sufficiently streamlined/screw speed too high/molar mass and melt viscosity too high/cross section area in exit flow channel too small/ external lubricant additive missing. 

Forming an optimal molding may require the addition of an external or internal lubricant to the formulation. Lubricants arc added in only small amounts, up to 1 wt %. External lubricants are insoluble in the phenohe matrix resin and are often non- polar materials such as parafiins and waxes. External lubricants act as mold release agents. In contrast, internal lubricants improve melt homogeneity, lower viscosity, and lower injection pressure. Therefore, internal lubricants such as fatty alcohols, fatty acid salts, acid esters, and acid amides must be fully soluble in the phenohe prepolymer [1]. 

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