Resin properties polyethylene

Cross fractionation shows considerable promise in terms of providing a relatively complete picture of the structural distributions present in polyethylene, particularly in LLDPE resins. However, there is much work to be done in learning how to use this type of data and to relate it to resin properties and synthesis conditions. Perhaps as techniques become more refined and easier to use to generate this type of information there will be further progress in the structure-property area. 

A new polymer modification process has been developed to reduce the cost of the engineering resin. The modification process is blended polymers. A blended polymer is a mixture of at least two polymers or a copolymer. There are three types of blended polymers miscible, immiscible, and compatible polymers. On occasion, blended polymers have properties that exceed those of either of the constituents. For instance, blends of polycarbonates (PC) resin and polyethylene terephthalate (PET) polyester were originally created to improve the chemical resistance of the PC. This is because PC actually had a fatigue resistance and low-temperature impact resistance that was superior to either of the individual polymers. 

General discussions of the effect of reinforcing agents on the thermal properties of polymers include glass fiber-reinforced polyethylene terephthalate [28], multiwalled carbon nanotube-reinforced liquid crystalline polymer [29], polysesquioxane [30, 31], polynrethane [31], epoxy resins [32], polyethylene [33], montmorillonite clay-reinforced polypropylene [34], polyethylene [35], polylactic acid [36, 37], calcium carbonate-filled low-density polyethylene [38], and barium sulfate-filled polyethylene [39]. 

ETFE polymers are melt processible. Commercial ETFE is a copolymer of ethylene and tetrafluoroethylene. They have lower chemical resistance and thermal stability than perfiuorinated polymers. ETFE exhibits excellent resistance to radiation and can stand up to 200 megarads of exposure to cobalt 60. It is a tough thermoplastic available in different viscosities, which can be processed by techniques applicable to polyethylene. ETFE resins are specified by ASTM Method D3159, which also provides procedures or references to other ASTM methods for the measurement of resin properties. Commercial FEP resins offered by major manufacturers have been listed in Tables 6.15 through 6.18. 

Uses Slip agent in polyethylene, polypropylene films dyestuff dispersant for printing inks, surface coatings blending agent for polyamide resins Properties Gardner color 2 max. particle size 100% < 40 mesh sieve m.p. 76-86 C iodine value 70-82 acid value 1.0 max Kemamide EBS [PMC Spec.)... 

Polyethylene. Polyethylene remains the largest volume film and sheet raw material. It is available in a wide range of types, with variations in copolymers, homopolymers, molecular weight, and other factors contributing to a long Hst of resins. Resins are designed specifically for end use, and in addition blends of the various types may be used by processors to optimize properties, processibiUty, and economics. Almost two-thirds of the volume of all polyethylene resins are used in film or sheet appHcations (see Olefin polymers). 

In the sheeting market, the low density polyethylenes are less important than the high density resins. The high density resins have excellent chemical resistance, stress-crack resistance, durabiUty, and low temperature properties which make them ideal for pond liners, waste treatment faciUties, and landfills. In thicker section, HMW-HDPE sheet makes good containers, trays, tmck-bed liners, disposable items, and concrete molds. The good durabiUty, abrasion resistance, and light weight are critical elements for its selection. 

Extmsion of polyethylene and some polypropylenes is usually through a circular die into a tubular form, which is cut and collapsed into flat film. Extmsion through a linear slot onto chilled rollers is called casting and is often used for polypropylene, polyester, and other resins. Cast, as well as some blown, films may be further heated and stretched in the machine or in transverse directions to orient the polymer within the film and improve physical properties such as tensile strength, stiffness, and low temperature resistance. 

Lamination Inks. This class of ink is a specialized group. In addition to conforming to the constraints described for flexo and gravure inks, these inks must not interfere with the bond formed when two or more films, eg, polypropylene and polyethylene, are joined with the use of an adhesive in order to obtain a stmcture that provides resistance properties not found in a single film. Laminations are commonly used for food applications such as candy and food wrappers. Resins used to make this type of ink caimot, therefore, exhibit any tendency to retain solvent vapor after the print has dried. Residual solvent would contaminate the packaged product making the product unsalable. 

Polyethylene. Traditional melt spun methods have not utilized polyethylene as the base polymer because the physical properties obtained have been lower compared to those obtained with polypropylene. Advances in polyethylene technology may result in the commercialization of new spunbonded stmctures having characteristics not attainable with polypropylene. Although fiber-grade polyethylene resin was announced in late 1986 (11,12), it has seen limited acceptance because of higher costs and continuing improvements in polypropylene resin technology (see Olefin POLYMERS, POLYETHYLENE). 

Polyoxyethylene Esters. This series of surfactants consists of polyoxyethylene (polyethylene glycol) esters of fatty acids and aUphatic carboxyhc acids related to abietic acid (see Resins, natural). They differ markedly from mono- and diglycerides in properties and uses. 

Linear polyethylene (high density) was introduced in the late 1950s, with the development of coordination catalysts. Chlorosulfonation of these base resins gave products that were superior to the eadier, low density types in both chemical resistance and mechanical properties and with distinct advantages in mbber processibiUty (6,7). 

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