Very-low-density polyethylene VLDPE

At the end of the 1970s considerable interest developed in what became known as linear low density polyethylenes (LLDPE) which are intermediate in properties and structure to the high pressure and low pressure materials. While strictly speaking these are copolymers it is most convenient to consider them alongside the homopolymers. The LLDPE materials were rapidly accepted by industry particularly in the manufacture of film. The very low density polyethylenes (VLDPE) introduced by Union Carbide in 1985 were closely related. 

To demonstrate this technology, we targeted a copolymer with blocks of both high density polyethylene (HDPE, density 0.94 g cm 3) and very low density polyethylene (VLDPE, density -0.88 g cm 3). Process and product characterization details are given in Table 6. We chose the pyridylamide precatalyst 18 [41] for this study due to its high comonomer reactivity, high M°, and demonstrated CCTP ability. 

Plastomers is the name given to copolymers of ethylene that have a little crystallinity, but are largely amorphous. They are also called very low-density polyethylene (VLDPE). They are more elastic than LLDPE but less stiff. They are used as a sealing layer in film applications and controlled permeation packaging for vegetables and fruits. 

Application To produce linear polyethylene from very low density polyethylene (VLDPE) to linear low density polyethylene (LLDPE) to high density polyethylene (HDPE) and other specialty types using the Spherilene gas-phase technology and a single Ziegler-Natta titanium-based catalysts family. 

Also worthy of mention are the new very-low-density polyethylenes (VLDPEs), which are produced using metallocene-based catalysts [9]. These materials, which remain largely experimental at the moment, have a density of less than 0.9g/cm. ... 

Polyethylenes with larger amounts of comonomer and consequently density below the normal LLDPE range are called very low density polyethylene, VLDPE, or ultra low density polyethylene, ULDPE. While these can be produced using Ziegler-Natta catalysts, often they are made using metallocene catalysts, as described next. 

A new class of linear polyethylene copolymers with densities ranging between 0.890 and 0.915 g/cm, known as very low-density polyethylene (VLDPE), was introduced commercially in late 1984 by Union Carbide. These resins are produced by copolymerization of ethylene and alpha-olefins in the presence of a catalyst. 

Chemical properties Low density (LDPE) and very low density polyethylenes (VLDPE) have branched chains which do not pack together well, imparting low density. High density polyethylene (HOPE) has longer, less branched chains, imparting stiffness and strength. No solvents at ambient temperature due to PE s high crystallinity, but chlorinated liquids can swell the plastic. 

General Description Ultra low density polyethyl-enes (ULDPEs) and very low density polyethylenes (VLDPEs) are essentially synonymous designations for linear polyethylenes with densities down to 0.880 g/cu in. ULDPEs are finding applications as impact modifiers for other polyolefins. Dow Chemicals Attane ULDPE is an Ethylene/Octene copoly-... 

Very low-density polyethylene (VLDPE) polymers with densities ranging fiom 0.905 to 0.915 g/cm that contains a comonomer ... 

Very low density polyethylene (VLDPE)— Polymers with densities ranging from 0.905 to... 

Linear low-density polyethylene (LLDPE) is a variation of HDPE. It is synthesized similarly, but LLDPE has a much higher content of comonomer, such as hexene or octene. Incorporation of comonomer in the chain yields short chain branches of a specified length (Fig. 1.5). By controlling the amount of branch points through comonomer content, degree of crystallinity - hence density - can be controlled. Variants of LLDPE are known as very low-density polyethylene (VLDPE) and ultra low-density polyethylene (ULDPE). LLDPE density is generally in the range of 0.88 to 0.93 g/cm. ... 

Linear low-density polyethylene, LLDPE, was blended Stehling et al. (1995) with very low density polyethylene, VLDPE. The polymers prepared using metallocene catalyst had narrow molecular weight distribution, = 1-3. 

Ethylene-propylene copolymer (EPR, EPDM, or their mixture with Ln = 35-55 °C) was blended with ethylene copolymer (very low density polyethylene VLDPE with density 885 kg m and T = 65-90 °C), PP or PP block copolymers, and 0-7 phr talc. The blend showed excellent moldability, surface appearance, and hardness, as well as good impact resistance ... 

Very-low-density polyethylene (VLDPE) n. Any polymer of ethylene with some higher-olefin content, in the density range from 0.90 to 0.915g/cm, produced by the Union Carbide gas-phase process (Flex-omer ). The materials have low moduli, with properties between those of low-density polyethylene and ethylene-propylene rubbers. They are useful for stretchable films. 

Very-low-density polyethylene (VLDPE). This material was introduced in 1985 by Union Carbide, is very similar to LLDPE, and is principally used in film applications. VLDPE grades vary in density from 0.880 to 0.912 g/cm . Its properties are marked by high elongation, good environmental stress cracking resistance, excellent low-temperature properties, and it competes most frequently as an alternative to plasticised polyvinyl chloride (PVC) or ethylene-vinyl acetate (EVA). The inherent flexibility in the backbone of VLDPE circumvents plasticizer... 

MOLECULAR STRUCTURE, CRTSTALLIZATION AND MORPHOLOGY OF VERY LOW DENSITY POLYETHYLENE (VLDPE)... 

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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