Films linear polyethylenes

The first samples examined were prepared by the method developed by Smith et al. [70, 71] and by Matsuo [72]. Sample films of a thickness of ca. 100 pm were obtained by drying a gel which was obtained by quenching a 0.4 g/dl decalin solution of linear polyethylene with a molecular weight of 3 x 106 from 140 °C in ice-water. The samples thus obtained could be drawn to a very high extent because of very few intermolecular chain entanglements. However, since they could not be drawn highly in one step, they were drawn 10 times at the first step in a silicon oil bath at 145 °C at a rate of 1.6 times/min and then at the second step they were drawn so that the final draw ratio was 50,100, and 150 times. 

Fig. 12.25 The Universal testing platform fitted on a rotational Rheometrics RDA II rheometer host station. The two counterrotating cylinders where the film is mounted cause the application of the extensional strain. [Reprinted by permission from E. G. Muliawan, S. G. Hatzikiriakos, and M. Sentmanat, Melt Fracture of Linear Polyethylene, Int. Polym. Process., 20, 60 (2005).]...

Polyethylene terephthalate cannot be solvent-cemented or heat-welded. Adhesives are the prime way of joining PET to itself and to other substrates. Only solvent cleaning of PET surfaces is recommended as a surface treatment. The linear film of polyethylene terephthalate (Mylar) provides a surface that can be pretreated by alkaline etching or plasma for maximum adhesion, but often a special treatment such as this is not necessary. An adhesive for linear polyester has been developed from a partially amidized acid from a secondary amine, reacted at less than stoichiometric with a DGEB A epoxy resin, and cured with a dihydrazide.72... 

A preferentially and a sheaf-like aggregation with random in-plane orientation are observed for the thinner films (thicknesses of 0.1, 0.2 and 0.4 pm in panels a-c). By contrast thick films (0.6 pm and thicker, panel d) show a morphology that resembles the well known (bulk) spherulitic form with a banded structure, characteristic of linear polyethylene crystallized from the melt at moderately high undercooling. 

The generally accepted mechanism for the formation of short branching in polyethylene involves a backbiting intramolecular transfer reaction in which a radical at the end of the polymer chain abstracts a hydrogen atom from a methylene unit in the same chain (Fig. 6.9). This is a very important process in the free-radical, high-pressure polymerization of this monomer. Branched polyethylene from this process has lower crystallinity than linear polyethylene produced by a low-pressure process and as a consequence it tends to be less rigid and tougher and form clearer films than the latter. 

Attane. [Dw Plastics] Ultra low density linear polyethylene for film extrusion. 

Fig. 2.20 Examples of electron micrographs of polymers, (a) A defocussed bright-field image of a thin film of isotactic polystyrene annealed and crystallised at about 170 °C (b) An image of a fracture surface replica from a sample of linear polyethylene crystallised from the melt at 4.95 kbar. ((a) Adapted by permission of Masaki Tsuji and (b) adapted from Principles of Polymer Morphology by D. C. Bassett. Cambridge University Press 1981.)...

Linear Low Density Polyethylene Linear polyethylenes with density 0.91-0.94 g/cm. Has better tensile, tear, and impact strength, and crack-resistance properties, but poorer haze and gloss than branched low-density polyethylene. Processed by extrusion at increased pressure and higher melt temperatures compared to branched low-density polyefliylene, and by molding. Used to manu-faeture film, sheet, pipe, electrical insulation, liners, bags, and food wraps. Also called LLDPE. 

A tubular film of linear polyethylene was extruded with straight sides (achieved by applying internal air pressure). The volume flow rate was 7 X 10 s and the haul-off tension was found to be... 

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-... 

Any linear polyethylene with density less than 0.90 g/cm, and possibly as low as 0.86 g/cm. ULDPE films have better optical properties and better resistance to puncture, impact, and tearing than conventional hnear low-density PEs. 

Armistead JP, Hoffman JD (2002) Direct evidence of regimes I, II, and III in linear polyethylene fractions as revealed by spherulite growth rates. Macromolecules 35(10) 3895-3913 Armstrong SR, Offord GT, Paul DR, Freeman BD, Hiltner A, Baer E (2014) Co-extruded polymeric films for gas separation membranes. J Appl Polym Sci 131(2) 39765 Azzurri F, Alfonso GC (2008) Insights into formation and relaxation of shear-induced nucleation precursors in isotactic polystyrene. Macromolecules 41(4) 1377-1383 Baekeland LH (1909) Method of making insoluble products of phenol and formaldehyde. US Patent 942,699... 

The Shirakawa PA films are shiny, flexible, polycrystalline, and completely insoluble in any solvent. Tb determine the molecular weight of the polymer, a sample of doped Shirakawa PA was hydrogenated to polyethylene at 175-260° C for 20 h under a high hydrogen pressme of 30 atm [10-12]. The resulting hydrogenated sample was totally soluble in tetralin. Since linear polyethylene is completely soluble in hot tetralin, it was assumed that Shirakawa s Ti(OBu)4/AIEt3 synthesis produced PA with no... 

Linear low-density polyethylene (LLDPE) is a copolymer of ethylene and a-olefins (generally 1-butene, 1-hexene, or 1-octene) with densities in the range 0.915-0.94 g cm . Products with even lower densities, down to 0.88 g cm, are sometimes called very low-density polyethylene (VLDPE) but are chemically identical to LLDPE. Copolymerization of ethylene with increasing amounts of a-olefins disrupts the order of the linear polyethylene chains by introducing short-chain branches. As a consequence, the density, crystallinity, and rigidity of LLDPE are lower than for HD PE. Linear low-density polyethylene is used predominantly in films, and shares the market with LDPE. 

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