High density polyethylene, HDPE extrusion

Alpha Packaging manufactures botdes and jars made from polyethylene terephthalate (PET) and high-density polyethylene (HDPE) for the pharmaceutical, nutritional and personal care markets. Technologies used include injection blow moulding, injection stretch blow moulding, and extrusion blow moulding. Alpha manufactures stock and custom containers in a variety of styles and colours. 

High Density Polyethylene (HDPE). The preferred method of evaluating HDPE was found to be the time to cross link at 220 0 using the Brabender apparatus, as is made evident by the rapid increase in torque. Determining melt viscosity by multiple extrusion showed only small differences compared to the base polymer. 

Materials. High density polyethylene (HDPE) having different molecular weights, and specific gravity of 0.951 (Marlex 5202, HXM 50100, made by Phillips 66 Co), were used for extrusion applications. Polyamides used were a semicrystalline copolyamide of adipic acid, hexamethylene diamine and caprolactam, and a copolyamide containing isophthalic acid as well. An anhydride modified polyethylene (3-5) as an interlaminar adhesive/compatibilizer was also used. The combinations are generally included in "Selar" barrier materials supplied by E. I. du Pont de Nemours Co. 

Li et al. reported that immiscible high-density polyethylene (HDPE)/ poly(ethylene terephthalate) (PET) blends, prepared by means of melt extrusion with ethylene-butyl acrylate-glycidyl methacrylate (EBAGMA) terpoly-mer as a reactive compatibilizer, can exhibit shape memory effects [32]. They observed that the compatibilized blends showed improved shape memory effects along with better mechanical properties as compared to the simple binary blends. In the blend, HDPE acts as a reversible phase, and the response temperature in the shape recovery process is determined by of HDPE. The shape-recovery ratio of the 90/10/5 HDPE/PET/EBAGMA blend reached nearly 100%. Similar behavior was observed for immiscible HDPE/ nylon 6 blends [33]. The addition of maleated polyethylene-octene copolymer (POE-g-MAH) increases compatibility and phase-interfacial adhesion between HDPE and nylon 6, and shape memory property was improved. The shape recovery rate of HDPE/nylon 6/POE-g-MAH (80/20/10) blend is 96.5% when the stretch ratio is 75%. 

This coextrusion techniqne has been applied to the fabrication of breathable films, using polyethylene oxide and polyolefin fiUed with CaC03. As the layer thickness decreased, the water vapor transmission rate changed dramatically due to changes from a continuous to discontinuous layer structure. Microlayer extrusion of a number of polymers has been accomphshed, including combinations of high-density polyethylene (HDPE) and linear low-density polyethylene (LLDPE), ethylene-styrene copolymers and low-den-... 

Recently, Liu et al. [34] prepared banana fibre (BaF)-filled composites based on high-density polyethylene (HDPE)/polyaminde-6 (PA 6) blends via a two-step extrusion method. Maleic anhydride grafted styrene/ethylene-butylene/styrene triblock polymer (SEBS-g-MA) and maleic anhydride grafted polyethylene (PE-g-MA) were used to enhance impact performance and interfacial bonding between BaF and the resins. Mechanical, crystaUization/melting, thermal stability, water absorption and... 

Lei and Wu [40] prepared wood plastic composites based on in-sifw-formed polyethylene terephthalate (PET) sub-micro-fibril (less than 500 nm in diameter) reinforced high-density polyethylene (HDPE) matrices through strand die extrusion and hot strand stretching. The PET fibrils obviously increased mechanical properties of the... 

Ethylene polymerization catalysts based on chromium as the active center are primarily used in the low-pressure manufacture of high density polyethylene (HDPE) with a relatively broad molecular weight distribution. This type of polyethylene is primarily used for blow-molding applications for bottles and large containers and for extrusion applications for pipe and HDPE film for merchandise bags. 

Some highly entangled hnear polymers, including high-density polyethylene (HDPE), hnear low-density polyethylene (LLDPE), 1,4-polybutadiene (PBDE), and polydimethylsiloxane (PDMS), exhibit an extrusion instabihty known as sharkskin, in which a small-amplitude, high-frequency disturbance appears on the extru-date surface at a wah shear stress that is typically on the order of the hnear viscoelastic plateau modulus (0.1 - 0.2 MPa for most polymers). Figure 12.10 shows... 

Shen and co-workers [29] used a twin-screw extrnder to devnlcanise waste tyre rubber and then blended the resnlting DR into high-density polyethylene (HDPE) to produce thermoplastic elastomers (TPE). They found that the high shear conditions during the extrusion process induced chain scission and oxidative degradation of the GTR. The reduction in crosslink density was apparent in a decrease in the gel content of the rubber/HDPE blends and an increase in the melt flow of the materials. 

HDPE exists as both a homopolymer and a copolymer with higher ethylene olefins. The latter offers properties which lie between low and high density, with typical densities of 0.945-0.950. Copolymers have found wide usage for extrusion blow, injection blow and injection moulding. They are, however, generally classified under HDPE. Virtually all high density polyethylenes contain an antioxidant. 

Extrusion blow molding process (a) single-screw extruder, (b) die with a gas supplier, and (c) mold. The blow molding condition of high-density polyethylene (HOPE) was set as typically used in industry. The maximum extrusion temperature of a single-screw extruder was set at 220°C for HDPE and 250°C for HDPE/polyethylene terephthalate (PET) blend. 

Blown bottles (500 ml detergent bottle) by extrusion blow molding (a) high-density polyethylene (HOPE) and (b) HDPE/polyethylene terephthalate (PET) blend. 

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