Density Polyethylene LDPE

As the number of branch points in PE chains increases, PE density decreases. The amount of unsaturations in PE also increases with the decrease in density. For example, an average number of methyl branches per 1000 carbons in LDPE increased from 21 at 0.922 g/cm to 43 at 0.916 g/cml An average number of vinylidene un-saturations/branches per 1000-Da (molecular weight) segments of LDPE increased from 16 at 0.922 g/cm to 35 at 0.912 g/cm [5]. Hence, sensitivity of PE to oxidation increases as its density decreases. LDPE is more vulnerable to oxidation compared to HDPE. On the contrary, LDPE is oxidized rather nniformly compared to HDPE, in which amorphous areas are oxidized faster than crystalline ones. 

LDPE typically has long side-chain branching off the main molecular chain and therefore is a more amorphons polymer. As a resnlt, it shows lower shrinkage compared to a more crystalline HDPE, in which many of the polymer molecules are packed closely together. 

Linear low-density PE (LLDPE) has a density similar to LDPE, but the linearity of HDPE. Branches of LLDPE are comparatively short. None of WPC manufacturers has reported that they make composite deck boards based on LLDPE, as well as on VLDPE (very low-density PE) and ULDPE (nltra low-density PE). The two latter polyethylenes have extremely high flexibility, which wonld make them inappropriate for composite deck boards or railing systems. 

LDPE can be easily scratched by a thnmbnail, HDPE can be scratched with dif-flcnlty, and polypropylene can hardly be scratched at all. This is also related to the respective WPC. Apparently, this is why nnbrnshed polypropylene-based WPC feels more like a plastic. This property is directly related to hardness, which is the resistance of a material to deformation, indentation, scratching, and to abrasion resistance. The latter is lower for LDPE compared to that of HDPE (10-15 mg/100 cycles and 2-5 mg/100 cycles, respectively) [6]. 

Maximum operating temperature of LDPE is considered to be 71°C (160°F), compared to 82°C (180°F) for HDPE. 

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Low-density polyethylene (LDPE) Poly(phenyl sulfone)... 

Plastic materials represent less than 10% by weight of all packagiag materials. They have a value of over 7 biUion including composite flexible packagiag about half is for film and half for botties, jars, cups, tubs, and trays. The principal materials used are high density polyethylene (HDPE) for botties, low density polyethylene for film, polypropylene (PP) for film, and polyester for both botties and films. Plastic resias are manufactured by petrochemical companies, eg. Union Carbide and Mobil Chemical for low density polyethylene (LDPE), Solvay for high density polyethylene, Himont for polypropylene, and Shell and Eastman for polyester. 

Fig. 14. Shear viscosity, Tj, and extensional viscosity, Tj as a function of deformation rate of a low density polyethylene (LDPE) at 150°C (111). To convert...

Fig. 21. Dynamic viscoelastic properties of a low density polyethylene (LDPE) at 150°C complex dynamic viscosity Tj, storage modulus G and loss modulus G" vs angular velocity, CO. To convert Pa-s to P, multiply by 10 to convert Pa to dyn/cm, multiply by 10.

Fig. 5. Effect of surfactant type on surface resistivity, (a) Concentration of surface-active compound in low density polyethylene (LDPE) requked to achieve 10 Q/sq surface resistivity and (b) effect on surface resistivity of an acrylic polymer. Concentration of surface-active compound is 0.3%.

High pressure (60—350 MPa) free-radical polymerization using oxygen, peroxide, or other strong oxidizers as initiators at temperatures of up to 350°C to produce low density polyethylene (LDPE), a highly branched polymer, with densities from 0.91 to 0.94 g/cm. ... 

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

Polyethylene is the simplest of so-called high polymers. The reaction for low density polyethylene (LDPE) follows the classical free radical polymerization steps of initiator decomposition, initiation, propagation, and termination. The reaction is... 

Low density polyethylene (LDPE). This is one of the most widely used plastics. It is characterised by a density in the range 918-935 kg/m and is very tough and flexible. Its major application is in packaging him although its outstanding dielectric properties means it is also widely used as an electrical insulator. Other applications include domestic ware, tubing, squeeze bottles and cold water tanks. 

High-pressure polymerization of ethylene was introduced in the 1930s. The discovery of a new titanium catalyst hy Karl Ziegler in 1953 revolutionized the production of linear unhranched polyethylene at lower pressures. The two most widely used grades of polyethylene are low-density polyethylene (LDPE) and high-density polyethylene (HDPE). Currently,... 

Low-density polyethylene (LDPE) is produced under high pressure in the presence of a free radical initiator. As with many free radical chain addition polymerizations, the polymer is highly branched. It has a lower crystallinity compared to HDPE due to its lower capability of packing. 

Note that, apart from the filler particle shape and size, the molecular mass of the base polymer may also have a marked effect on the viscosity of molten composites [182,183]. The higher the MM of the matrix the less apparent are the variations of relative viscosity with varying filler content. In Fig. 2, borrowed from [183], one can see that the effect of the matrix MM on the viscosity of filled systems decreases with the increasing filler activity. In the quoted reference it has also been shown that the lg r 0 — lg (MM)W relationships for filled and unfilled systems may intersect. The more branches the polymer has, the stronger is the filler effect on its viscosity. The data for filled high- (HDPE) and low-density polyethylene (LDPE) [164,182] may serve as an example the decrease of the molecular mass of LDPE causes a more rapid increase of the relative viscosity of filled systems than in case of HDPE. When the values (MM)W and (MM)W (MM) 1 are close, the increased degree of branching results in increase of the relative viscosity of filled system [184]. 

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). 

E-plastomers, particularly the high- and medium-density materials, have found extensive use in films [17]. They are valued for their excellent seal character which allows the formation of mechanically strong seals at relatively low temperatures compared to traditional low-density polyethylene (LDPE). In addition, these E-plastomers can be obtained in a range of crystallinities and softness. These higher-density materials are typically made in the blown-film process and are used for protective film covers and disposable bags. 

Low-density polyethylene (LDPE) film for food packaging, etc. High-density polyethylene (HDPE) blow molded into bottles and containers... 

Polyetiiylene (PE) is one of the lowest-cost polymers. There are various types of polyethylene denoted by their molecular weight. This ranges from low-density polyethylene (LDPE) through uTtrahigh-molecular-weight (UHMW) polyethylene. Physical properties, processability, and other characteristics of the polyethylene vary greatly with the molecular weight. 

Chimassorb 944 Determination in Polypropylene, High Density Polyethylene (HDPE) and Low Density Polyethylene (LDPE) by the Total Nitrogen Content Analytical Method, Code No. KC65/1, Ciba-Geigy, Basel (1980). 

Materials. Low density polyethylene (LDPE) was obtained from Dow Chemical Co., PE 510. High density polyethylene (HDPE) was obtained from Phillips Chemical, Marlex 6001. Polypropylene (PP) was obtained from Exxon Corp., Exxon PP 8216. Di-t.-butylperoxide, 99%, (DtBP) was obtained from Polysciences. Gaseous hexafluoroacetone vras obtained from Nippon Mektron Ltd., Japan. 

The plastic bottle and dispensing tip is made of low-density polyethylene (LDPE) resin, which provides the necessary flexibility and inertness. Because these components are in contact with the product during its shelf life, they must be carefully chosen and tested for their suitability for ophthalmic use. In addition to stability studies on the product in the container over a range of normal and accelerated temperatures, the plastic resins must pass the USP biological and chemical tests for... 

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