Polyethylene waxes applications

Rigid Applications. The use of the lead stabilizers is very limited in the United States but, they are stiU used in several rigid PVC appHcations in Europe and Asia. The highest use of lead stabilizers in rigid PVC is for pipe and conduit appHcations. Tribasic lead sulfate is the primary heat stabilizer with lead stearates included to provide lubrication. The lead products are typically fully formulated, usually including lubricants and pigments for pipe extmsion appHcations. These lead one-packs, when used at about 1.8—2.5 phr, provide all of the stabilizer and lubrication needed to process the polymer. A lead one-pack contains tribasic lead sulfate, dibasic lead stearate calcium stearate, polyethylene wax, paraffin wax, ester wax, and pigments. 

In general, resins are compatible with a large number of materials (oils, plasticizers, polyethylene waxes, rubbers). Compatibility depends on resin type, molecular weight and its distribution, resin structure and configuration, and finally on application requirements. 

This is one of the most important natural fibers. It is produced in India, Bangladesh, Thailand, Vietnam, and other countries. It contains 56-64 wt% cellulose, 29-25% hemicellulose, 11-14% lignin, and a small proportion of fats, pectin, ash, and waxes. Application of jute fiber in RPs with matrices of TS resins such as unsaturated polyester or vinyl ester resins has been widely studied. To date the poor adhesion to hydrophobic TPs, such as polyethylene and polypropylene, has to date limited application in TPs. 

Waxes are often used as multifunctional lubricants. These are generally paraffin hydrocarbon wax (melting point 65-75°C) and polyethylene wax (melting point 100-130°C). Being nonpolar, they are very incompatible with PVC, so they are used as external lubricants. Paraffin lubricants are typically used in rigid PVC pipe and profile extrusion applications at additive levels of 0.5-1.5 phr. Partially oxidized polyethylene wax works well as an external lubricant for PVC by delaying fusion... 

Polyethylene waxes have been added to paints and varnishes as far back as 1950 to improve their mar and abrasion resistance. Figure 10.4 shows performance polyethylene wax in alkyd-based traffic paint. Less than 2% polyethylene wax improves resistance by a factor of five. Polyethylene waxes used in these older applications had molecular weights tfom 2,000 to 5,000 daltons. Later information shows that molecular weights of polyethylene-based additives used now are in a similar range (1,500 to 5,000 daltons). Up to 5 wt% solids are used now to improve mar and abrasion resistance of coatings. The additives act by... 

Polyethylene waxes have several useful characteristics in their application to paints, such as low toxicity, antiblocking properties combined with slip properties, and improved mar and scratch resistance (see Figure 10.4). ° ... 

Triacetin resistance is especially critical when filter tips are made in one location, stored, and then shipped to another location. For these operations, polyethylene-based adhesives are used because of their low polarity and therefore excellent resistance to triacetin. Where filter plugs are attached at the same location shortly after production, EVA-based adhesives are suitable and preferred. Both types of adhesives use low odor, clean tackifiers such as hydrogenated hydrocarbons or pure monomer resins (typically a-methylstyrene based). Rosin, rosin esters, and phenol-containing tackifiers are not acceptable. EVA-based adhesives use a higher level of wax (about 1 /3 of the formula) than polyethylene-based adhesives (5-20% wax) due to the lower crystallinity and slower set of EVA vs. PE. Application viscosities are 2000-5000 cP. 

While chains having molecular weights of a few thousands only form brittle waxes, polyethylenes having molar masses of above hundred thousand show much better mechanical properties. They can be processed into films, pipes, and other performance products. When molar mass is further increased up to several millions, even higher impact strengths and abrasion resistances are achieved which enable these materials to be used in heavy-duty applications like skating floors and artificial hips. 

Zisman discovered that there is a critical surface tension characteristic of low-energy solids, such as plastics and waxes. Liquids ihat have a lower surface tension than the solid will spread on that solid, while liquids with a higher surface tension will not spread. Examples of critical surface tension values for plastic solids in dynes per cm are "Teflon/ 18 polyethylene, 31 polyethylene terephthalate, 43 and nylon, 42-46. As one indication of the way this information can be used in practical applications, one can consider the bonding of nylon to polyethylene. If nylon were applied as a melt to polyethylene, it would not wet the lower-energy polyethylene surface and adhesion would be poor. However, molten polyethylene would spread readily over solid nylon to provide a strong bond. 

Hydrocarbon waxes produced in a fixed-bed reactor, which has operated since 1955, have found a variety of uses. Also, byproducts from the Sasol Lurgi coal gasifiers are recovered for chemical and solvent applications. These products include phenol, cresols, toluene, xylenes, ammonia, and sulfur. An addition to the spectrum of chemical products from Sasol is polypropylene. Also, ethane is being cracked to supplement ethylene production for sale to polyethylene producers. Additional work is in progress to evaluate the recovery of organic acids from aqueous waste streams. 

Polymer encapsulation is an ex situ S/S technique involving the application of thermoplastic resins such as bitumen, polyethylene and other polyelfins, paraffins, waxes, and sulfur-based cements, as opposed to cements and pozzolans. Polymer encapsulation has been used primarily to immobilize low-level radioactive wastes and those waste types that are difficult to immobilize in cement, such as Cl- and SO4-based salts. Bitumen (asphalt) is the least expensive and (hence) used most often. Thermoplastic encapsulation heats and mixes the contaminated soil with the resin at 130 to 230°C in an extrusion machine. Organic pollutants and water boil off during the extrusion and are collected for treatment or disposal. The final product, a stiff yet plastic resin, is then discharged into a drum or other container and land-filled (U.S. EPA, 1997). 

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