Polyethylene processing aids

Polyethylene 617A Allied Chemical Low molecular wt. polyethylene Processing aid... 

Plasticizers and Processing Aids. Petroleum-based oils are commonly used as plasticizers. Compound viscosity is reduced, and mixing, processing, and low temperature properties are improved. Air permeabihty is increased by adding extender oils. Plasticizers are selected for their compatibihty and low temperature properties. Butyl mbber has a solubihty parameter of ca 15.3 (f /cm ) [7.5 (cal/cm ) ], similar to paraffinic and naphthenic oils. Polybutenes, paraffin waxes, and low mol wt polyethylene can also be used as plasticizers (qv). Alkyl adipates and sebacates reduce the glass-transition temperature and improve low temperature properties. Process aids, eg, mineral mbber and Stmktol 40 ms, improve filler dispersion and cured adhesion to high unsaturated mbber substrates. 

Calendering operations are done routinely, and warm roUs (40—90°C) are recommended for optimum sheet smoothness. A process aid, such as low molecular weight polyethylene wax, is often used. Sheet thicknesses of 0.5—1.3 mm (20—50 mils) can normally be produced. 

In addition to acting as impact modifiers a number of polymeric additives may be considered as processing aids. These have similar chemical constitutions to the impact modifiers and include ABS, MBS, chlorinated polyethylene, acrylate-methacrylate copolymers and EVA-PVC grafts. Such materials are more compatible with the PVC and are primarily included to ensure more uniform flow and hence improve surface finish. They may also increase gelation rates. In the case of the compatible MBS polymers they have the special function already mentioned of balancing the refractive indices of the continuous and disperse phases of impact-modified compound. 

Hong, Y., Coombs, S. J., Cooper-White, J. J., Mackay, M. E., Hawker, C. J., Malmstrom, E., and Rehnberg, N. 2000. Film blowing of linear low density polyethylene blended with a novel hyperbranched polymer processing aid. Polymer, 41, 7705-7713. 

Chlorinated polyethylene was evaluated as a compatibiliser forpoly(vinyl chloride) composites containing 25% or 40% wood flour. The compositions also contained lubricants, a stabiliser and a processing aid. Following blending, the composites were characterised by rheology studies and measurements of melt strength. The addition of chlorinated polyethylene significantly enhanced the processability of... 

Processing aids are usually based on high molecular weight acrylic copolymers (for PVC). They modify the rheology and processing characteristics of the melt. Lubricants are processing aids that function to ease the process and are of two types either internal lubricants (that influence the viscosity, such as calcium stearates) or external lubricants (such as oxidised polyethylene wax). Lead-stabilised PVC lubricants are a part of the stabiliser system. They are important in PVC foam formulations. 

As stated previously, styrene-diene triblock copolymers are the most important category of thermoplastic elastomers. Unlike most other TPEs, they can be blended with large quantities of additives without a drastic effect on properties. In almost all applications, the actual triblock copolymer content is less than 50%. Oils are used as a processing aid and do not result in a significant loss of properties if the polystyrene domains are not plasticized. For this reason, naphthalenic oils are preferred. The use of inert fillers such as clays or chalks reduces the cost of the final material. Unlike conventional rubbers, inert fillers do not have a substantial effect on the mechanical properties of TPEs. Thermoplastics such as polyethylene or polypropylene are also used to improve the solvent resistance and can increase the upper service temperature. Polystyrene homopolymer is used as a processing aid, which also increases the hard phase weight fraction and causes the material to stiffen. 

Chem. Descrip. Polyethylene homopolymer CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses Gellant for oils, emollient, moisture retention aid, heat stabilizer in personal care prods. film-former oil or fragrance encapsulator nonirritating abrasive additive for plastics, rubber, adhesives, coatings, inks, paper, polishes, textiles processing aid Features Increases permanency... 

Chem. Descrip. Highly branched, med. m.w. polyethylene wax CAS 9002-88-4 EINECS/ELINCS 200-815-3 Uses Wax used in hot-melt adhesives and coatings for papers and pkg. materials paraffin modifiers in slush and cast molding, candles, inte processing aid for rubber compounding dispersant for color cones. food pkg. adhesives, coatings, paper, cellophane, rubber defoamer in food-contact coatings, paper/paperboard Features Nonemulsifiable low density... 

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