Linear Low-Density Polyethylene LLDPE

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.  

LLDPE solid-state properties also reflect a combination of those of HDPE and LDPE. Its strength is higher than that of LDPE, approaching that of HDPE. However, it has the softer feel and lower stiffness of LDPE. 

As mentioned above, linear polyethylene can be produced as a homopolymer, resulting in high density polyethylene, HDPE, or as a copolymer having as comonomer alkenes such as butene, hexene, and octene. 

The presence of a comonomer in the polymerization process, when a stereo-specific catalyst is used, results in the production of a rather linear polymer with very short branch-like pendant groups. This polymer is called linear low density polyethylene (LLDPE) or ultra low density polyethylene (ULDPE), depending on the density achieved by the addition of the comonomer. The larger the amount of comonomer added, the lower is the density of the copolymer. For example, if hexene is used, the pendant groups are as follows  

Normally the amount of comonomer ranges from 1 to 10% on a molar basis. 

Typical uses for LLDPE include stretch/cling film, grocery sacks, and heavy duty shipping sacks. LDPE and LLDPE are often blended to optimize the benefit ob- 

It has been found that as the density is pushed below 0.91 g/cm by the incorporation of higher levels of comonomer, the level of hexane extractables increases to a level beyond that sanctioned by the EDA. These extractables also can oxidize, resulting in off odors and off flavors. 

The emission and consumption data shown in Table 3.13 represent the emission and consumption levels from eight plants that reported their data. The average age of these plants is 10 years and their average capacity in 1999 was 200 kt per year. 

LLDPE benchmark 1999 European average Average top 50 % Average 3 quartile Average 4 quartile 

Monomer consumption in kilograms per tonne of product (kg/t) 2. Direct energy in kWh per tonne of product (kWh/t). Direct energy is the energy consumption as delivered  

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Linear Low Density Polyethylene. Films from linear low density polyethylene (LLDPE) resias have 75% higher tensile strength, 50% higher elongation-to-break strength, and a slightly higher but broader heat-seal initiation temperature than do films from LDPE. Impact and puncture resistance are also improved over LDPE. Water-vapor and gas-permeation properties are similar to those of LDPE films. 

The majority of spunbonded fabrics are based on isotactic polypropylene and polyester (Table 1). Small quantities are made from nylon-6,6 and a growing percentage from high density polyethylene. Table 3 illustrates the basic characteristics of fibers made from different base polymers. Although some interest has been seen in the use of linear low density polyethylene (LLDPE) as a base polymer, largely because of potential increases in the softness of the final fabric (9), economic factors continue to favor polypropylene (see OlefinPOLYMERS, POLYPROPYLENE). 

Polybutenes enjoy extensive use as adhesives, caulks, sealants, and glaring compounds. They are used as plasticizers in mbber formulations with butyl mbber, SBR, and natural mbber. In linear low density polyethylene (LLDPE) blends they induce cling to stretch-wrap films. Polybutenes when modified at their unsaturated end groups with polar fiinctionahty are widely employed in lubricants as dispersants. Blends of polybutene with polyolefins produce semisoHd gels that can be used as potting and electrical cable filling materials. 

In order to improve the physical properties of HDPE and LDPE, copolymers of ethylene and small amounts of other monomers such as higher olefins, ethyl acrylate, maleic anhydride, vinyl acetate, or acryUc acid are added to the polyethylene. Eor example, linear low density polyethylene (LLDPE), although linear, has a significant number of branches introduced by using comonomers such as 1-butene or 1-octene. The linearity provides strength, whereas branching provides toughness. 

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. 

Resins and plastics such as low-density polyethylene (LDPE), high-density polyethylene (HOPE), linear low-density polyethylene (LLDPE), polypropylene, polystyrene, and polyvinyl chloride (PVC) ... 

Dimerization of ethylene to butene-1 has been developed recently by using a selective titanium-based catalyst. Butene-1 is finding new markets as a comonomer with ethylene in the manufacture of linear low-density polyethylene (LLDPE). 

The three isomers constituting n-hutenes are 1-hutene, cis-2-hutene, and trans-2-hutene. This gas mixture is usually obtained from the olefinic C4 fraction of catalytic cracking and steam cracking processes after separation of isobutene (Chapter 2). The mixture of isomers may be used directly for reactions that are common for the three isomers and produce the same intermediates and hence the same products. Alternatively, the mixture may be separated into two streams, one constituted of 1-butene and the other of cis-and trans-2-butene mixture. Each stream produces specific chemicals. Approximately 70% of 1-butene is used as a comonomer with ethylene to produce linear low-density polyethylene (LLDPE). Another use of 1-butene is for the synthesis of butylene oxide. The rest is used with the 2-butenes to produce other chemicals. n-Butene could also be isomerized to isobutene. ... 

Linear low-density polyethylene (LLDPE) is produced in the gas phase under low pressure. Catalysts used are either Ziegler type or new generation metallocenes. The Union Carbide process used to produce HDPE could be used to produce the two polymer grades. Terminal olefins (C4-C6) are the usual comonomers to effect branching. 

When water (a Newtonian liquid) is in an open-ended pipe, pressure can be applied to move it. Doubling the water pressure doubles the flow rate of the water. Water does not have a shear-thinning action. However, in a similar situation but using a plastic melt (a non-Newtonian liquid), if the pressure is doubled the melt flow may increase from 2 to 15 times, depending on the plastic used. As an example, linear low-density polyethylene (LLDPE), with a low shear-thinning action, experiences a low rate increase, which explains why it can cause more processing problems than other PEs. The higher-flow melts include polyvinyl chloride (PVC) and polystyrene (PS). 

LLDPE. See linear low density polyethylene (LLDPE) load-bearing products 139 ... 

The presence of long chain branches in low density polyethylene (LDPE) accounts for the difference in properties e.g. higher melt strength, greater toughness for the same average molecular weight) between LDPE and linear low density polyethylene (LLDPE, made by coordination polymerization). 

The metal catalyzed production of polyolefins such as high density polyethylene (HDPE), linear low density polyethylene (LLDPE) and polypropylene (PP) has grown into an enormous industry. Heterogeneous transition metal catalysts are used for the vast majority of PE and all of the PP production. These catalysts fall generally within two broad classes. Most commercial PP is isotactic and is produced with a catalyst based on a combination of titanium chloride and alkylaluminum chlorides. HDPE and LLDPE are produced with either a titanium catalyst or one based on chromium supported on silica. Most commercial titanium-based PE catalysts are supported on MgCl2. 

Sclair A process for polymerizing ethylene. Depending on the co-monomer used, the product can be linear low-density polyethylene (LLDPE) or high-density polyethylene (HDPE). Developed by DuPont in 1960 and widely licensed. Engineered by Uhde under the name Sclairtech. Nova Chemicals (Alberta) acquired the technology in 1994. 

Similarly large anisotropies were later reported for highly emissive blends of alkoxy-substituted bis(phenylethynyl)benzene derivatives and polyolefins such as linear low-density polyethylene (LLDPE) and isotactic polypropylene (z-PP) [8,9]. The latter systems reach high levels of anisotropy at very low draw ratios, which is advantageous from a processing point of view. 

Linear combination of atomic orbitals (LCAO) method, 16 736 Linear condensation, in silanol polycondensation, 22 557-558 Linear congruential generator (LCG), 26 1002-1003 Linear copolymers, 7 610t Linear density, 19 742 of fibers, 11 166, 182 Linear dielectrics, 11 91 Linear elastic fracture mechanics (LEFM), 1 509-510 16 184 20 350 Linear ethoxylates, 23 537 Linear ethylene copolymers, 20 179-180 Linear-flow reactor (LFR) polymerization process, 23 394, 395, 396 Linear free energy relationship (LFER) methods, 16 753, 754 Linear higher a-olefins, 20 429 Linear internal olefins (LIOs), 17 724 Linear ion traps, 15 662 Linear kinetics, 9 612 Linear low density polyethylene (LLDPE), 10 596 17 724-725 20 179-211 24 267, 268. See also LLDPE entries a-olefin content in, 20 185-186 analytical and test methods for,... 

The most recent arrival was Linear Low Density Polyethylene (LLDPE) in 1977. LLDPE combined some of the best features of both LPDE and HDPE by using a comonomer, butene-1, hexene-1, or octene-1. 

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