Polyethylene HDPE, LDPE, LLDPE

Dow ABS Nylon 6/6 Polycarbonate Polyethylene, HDPE, LDPE, LLDPE, ULDPE Polypropylene HPPP, CPPP Polystyrene HIPS, GPPS, Recycled, Advanced Styrenic Resin SAN Polyurethane Elastomers Polyolefin Plastomer PC/ABS Crystalline Polymer ABS/TPU... 

Figure 3.13 shows the shift factors aT determined from time-temperature superposition as a function of temperature for melts of two semi-crystalline thermoplastics as well as the Arrhenius plot. For the two polyethylenes (HDPE, LDPE), the progression of log ax can be described with the Arrhenius equation. The activation energies can be determined from the slope as Ea(LDPE) 60 kj/mol and Ea(HDPE) 28 kj/mol. Along with polyethylenes (HDPE, LDPE, LLDPE), other significant semi-crystalline polymers are polypropylene (PP), polytetrafluoroethylene (PTFE) and polyamide (PA). 

Recyclates from similar plastic materials, e.g., packaging plastics that might comprise different polyolefins, such as polyethylenes (HDPE, LDPE, LLDPE), polypropylene (PP) and/or copolymers, PS, PET and PET -copolymers, different polyamides (PA), rigid and plasticized PVC, etc. 

Polyethylene, as LDPE, LLDPE or a mixture or blend involving combinations of LDPE, MDPE, HDPE, EVA, etc., finds a wide usage in bags, sacks, sachets, overwraps, shrink wraps, stretch wraps, etc. Most deep freeze packs, for example, use LDPE or an LDPE mixture which is produced from a reel on a form fill seal type machine. However, as many of these packs are up to 100% printed, even ink of 2-5 Pm could be considered as a separate layer which modifies some of the physical and chemical properties. As all polyolefins need a surface (oxidative) treatment to ensure a good print key, this or any other surface treatment process may further modify the film properties. 

Polyolefins are manufactured and used in much greater quantity than any other class of plastics. The principal polyolefins are polyethylenes of various densities (LDPE, LLDPE, HDPE) and polypropylene (PP) (see Olefin polymers). 

LDPE = low density polyethylene LLDPE = linear low density polyethylene HDPE = high density polyethylene PP = polypropylene PVC = polyvinyl chloride PS = polystyrene ABS = polyacrylonitrile-butadiene-styrene. 

By the mid-1990s capacity for polyethylene production was about 50 000 000 t.p.a, much greater than for any other type of plastics material. Of this capacity about 40% was for HDPE, 36% for LDPE and about 24% for LLDPE. Since then considerable extra capacity has been or is in the course of being built but at the time of writing financial and economic problems around the world make an accurate assessment of effective capacity both difficult and academic. It is, however, appeirent that the capacity data above is not reflected in consumption of the three main types of material where usage of LLDPE is now of the same order as the other two materials. Some 75% of the HDPE and LLDPE produced is used for film applications and about 60% of HDPE for injection and blow moulding. 

Ziegler-Natta polymerization leads to linear unbranched polyethylene, the so-called high density polyethylene (HDPE), which is denser, tougher and more crystalline. By copolymerization with other alkenes it is possible to obtain linear low density polyethylene (LEDPE) with better mechanical properties than LDPE. Blends of LLDPE and LDPE are used to combine the good final mechanical properties of LLDPE and the strength of LDPE in the molten state. 

A significant fraction, more than 25%, of the low-density polyethylene (LDPE) (Sec. 3-14a) produced by radical polymerization consists of various copolymers of ethylene. LDPE has come under increasing economic pressure in recent years because of a combination of factors [Doak, 1986]. High-density polyethylene (HDPE) has displaced LDPE in applications such as blow-molded bottles and thin films where the increased strength of HDPE is preferred over the clarity of LDPE. Linear low-density polyethylene (LLDPE) (Sec. 8-1 lc) competes effectively with LDPE in terms of both cost and properties. New producers of ethylene have entered the LDPE market because of a lack of alternatives for their feedstocks. Many LDPE producers use copolymerization as a strategy to obtain products more resistant to displacement by HDPE and LLDPE. 

Coordination copolymerization of ethylene with small amounts of an a-olefin such as 1-butene, 1-hexene, or 1-octene results in the equivalent of the branched, low-density polyethylene produced by radical polymerization. The polyethylene, referred to as linear low-density polyethylene (LLDPE), has controlled amounts of ethyl, n-butyl, and n-hexyl branches, respectively. Copolymerization with propene, 4-methyl-1-pentene, and cycloalk-enes is also practiced. There was little effort to commercialize linear low-density polyethylene (LLDPE) until 1978, when gas-phase technology made the economics of the process very competitive with the high-pressure radical polymerization process [James, 1986]. The expansion of this technology was rapid. The utility of the LLDPE process Emits the need to build new high-pressure plants. New capacity for LDPE has usually involved new plants for the low-pressure gas-phase process, which allows the production of HDPE and LLDPE as well as polypropene. The production of LLDPE in the United States in 2001 was about 8 billion pounds, the same as the production of LDPE. Overall, HDPE and LLDPE, produced by coordination polymerization, comprise two-thirds of all polyethylenes. 

Ethylene Polymers. Depending on the polymerization conditions, three major types of polyethylene are manufactured low-density polyethylene (LDPE) by free-radical polymerization, linear low-density polyethylene (LLDPE) by copolymerization of ethylene with terminal olefins, and high-density polyethylene (HDPE) by coordination polymerization. The processes yield polymers with different characteristics (molecular weight, molecular weight distribution, melt index, strength, crystallinity, density, processability). 

ABA ABS ABS-PC ABS-PVC ACM ACS AES AMMA AN APET APP ASA BR BS CA CAB CAP CN CP CPE CPET CPP CPVC CR CTA DAM DAP DMT ECTFE EEA EMA EMAA EMAC EMPP EnBA EP EPM ESI EVA(C) EVOH FEP HDI HDPE HIPS HMDI IPI LDPE LLDPE MBS Acrylonitrile-butadiene-acrylate Acrylonitrile-butadiene-styrene copolymer Acrylonitrile-butadiene-styrene-polycarbonate alloy Acrylonitrile-butadiene-styrene-poly(vinyl chloride) alloy Acrylic acid ester rubber Acrylonitrile-chlorinated pe-styrene Acrylonitrile-ethylene-propylene-styrene Acrylonitrile-methyl methacrylate Acrylonitrile Amorphous polyethylene terephthalate Atactic polypropylene Acrylic-styrene-acrylonitrile Butadiene rubber Butadiene styrene rubber Cellulose acetate Cellulose acetate-butyrate Cellulose acetate-propionate Cellulose nitrate Cellulose propionate Chlorinated polyethylene Crystalline polyethylene terephthalate Cast polypropylene Chlorinated polyvinyl chloride Chloroprene rubber Cellulose triacetate Diallyl maleate Diallyl phthalate Terephthalic acid, dimethyl ester Ethylene-chlorotrifluoroethylene copolymer Ethylene-ethyl acrylate Ethylene-methyl acrylate Ethylene methacrylic acid Ethylene-methyl acrylate copolymer Elastomer modified polypropylene Ethylene normal butyl acrylate Epoxy resin, also ethylene-propylene Ethylene-propylene rubber Ethylene-styrene copolymers Polyethylene-vinyl acetate Polyethylene-vinyl alcohol copolymers Fluorinated ethylene-propylene copolymers Hexamethylene diisocyanate High-density polyethylene High-impact polystyrene Diisocyanato dicyclohexylmethane Isophorone diisocyanate Low-density polyethylene Linear low-density polyethylene Methacrylate-butadiene-styrene... 

Polyethylene (PE) is the largest synthetic commodity polymer in terms of annual production and is widely used throughout the world in a variety of applications. Based on the density, PE is classified as LDPE at 0.910-0.930g/cm3, high-density polyethylene (HDPE) at 0.931-0.970g/cm3, and linear low-density polyethylene (LLDPE) based on the polymer chain microstructure. At present, processes that produce PE use the following raw materials ... 

Figure 2.3 Schematic molecular structures of low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE)...

Table I shows the production of different kinds of polyolefins [high-density polyethylene (HDPE), low-density polyethylene (LDPE), isotactic polypropylene (PP), and linear low-density polyethylene (LLDPE)] (6). Apart from LDPE (discovered by workers at ICI), which has a highly branched structure and is produced in free radical reactions at ethylene pressures of 1000-3000 bar (1 bar = 105 Pa), the other polyolefins are synthesized at far lower pressures and in the presence of catalysts (7).

Polyethylene LDPE Polyethylene HDPE/LLDPE Polypropylene ... 

Abbreviations y x AFM AIBN BuMA Ca DCP DMA DMS DSC EGDMA EMA EPDM FT-IR HDPE HTV IPN LDPE LLDPE MA MAA MDI MMA PA PAC PB PBT PBuMA PDMS PDMS-NH2 interfacial tension viscosity ratio atomic force microscopy 2,2 -azobis(isobutyronitrile) butyl methacrylate capillary number dicumyl peroxide dynamic mechanical analysis dynamic mechanical spectroscopy differential scanning calorimetry ethylene glycol dimethacrylate ethyl methacrylate ethylene-propylene-diene rubber Fourier transform-infra-red high density polyethylene high temperature vulcanization interpenetrating polymer network low density polyethylene linear low density polyethylene maleic anhydride methacrylic acid 4,4 -diphenylmethanediisocyanate methyl methacrylate poly( amide) poly( acrylate) poly(butadiene) poly(butylene terephtalate) poly(butyl methacrylate) poly(dimethylsiloxane) amino-terminated poly(dimethylsiloxane)... 

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