High-density linear polyethylene

Figure 11 Mid-infrared transmission spectra recorded from a linear (high-density) polyethylene before, during and after oxidation at 145°C (a) OH stretching region, (b) carbonyl stretching region. Reproduced from Luongo [23]. Copyright 1960 John Wiley Sons, Inc.

The two polymer substrates investigated as part of the study of DBDPO mixtures were polypropylene (PP) and linear high density polyethylene (HDPE). while both PP and HDPE decompose by similar random chain scission, radical mechanisms, chain transfer occurs much more teadily during the pyrolysis of PP because of the presence of the tertiary hydrogens. In addition, only primary chain end radicals are formed when the HDPE chain cleaves homolytically. Therefore, a comparison of the PP/DBDPO and the HDPE/DBDPO mixtures volatile product distributions was undertaken. 

FIGURE 2.1 Simulated structure of linear high-density polyethylene (HDPE) contrasted with the structural formula of linear or normal decane. 

CPE Conventional (Low Density) Polyethylene LPE Linear (High Density) Polyethylene PP Polypropylene PMP Polymethylpentene... 

M. H. Wagner, P. Ehrecke, P. Hachmann, and J. Meissner, A Constitutive Analysis of Uniaxial, Equibiaxial and Planar Extension of a Commercial Linear High-density Polyethylene Melt, J. Rheol., 42, 621-638 (1998). 

The formation of linear isotactic or syndiotactic polymers can be achieved by metal-catalysed polymerisation. This employs Ziegler-Natta catalysts, made from triethylaluminium (Et3Al) and titanium tetrachloride (TiCl4), which react with alkenes by a complex mechanism. The polymerisation of ethylene (CH2=CH2) leads to the formation of (linear) high-density polyethylene, which is of greater strength than the (branched) low-density polyethylene produced on radical polymerisation. 

J.P. Hogan, Olefin polymers—linear (high-density) polyethylene, in M. Grayson, D. Eckroth (Eds.), Kirk-Othmer Encyclopedia of Chemical Technology, vol. 16, third ed., Wiley, New York, 1981, pp. 421M33. 

Low density polyethylene is branched, and it is more easily processed than the linear high density polyethylene. This is caused by the special kind of branching short branches regularly spaced along the chain backbone act as an internal plasticizer. 

Discovery of Linear (High-Density) Polyethylene Use of Comonomers Linear Low-Density Polyethylene Stereospecific Polymerization Discovery of Polypropylene Manufacturing Processes High-Pressure LDPE Low-Pressure, Linear HOPE LLDPE... 

LLDPE is generally intermediate in properties between conventional low-density polyethylene (LDPE) made by high-pressure processes and linear, high-density polyethylene (HOPE) of the Ziegler or Phillips type. A qualitative comparison of the more significant physical properties is given in Table II (some quantitative data are given in Table IV),... 

In the early 1950 s, Ziegler found that in the presence of ZrCl + AIR3 ethylene can be polymerized at low temperature and pressure into linear, high density polyethylene (HOPE). The catalysts developed by Ziegler, and later by Natta become known as Ziegler-Natta, or Z-N catalysts. These can be defined as polymerization initiators created from a catalyst (1) and co-catalyst... 

The active species for the PBI complexes is not as well characterized as in the nickel and palladium systems. It is assumed to be a cationic alkyl complex formed by reaction of the dihalo precatalyst with a cocatalyst such as methylaluminoxane (MAO). The resulting active species polymerizes ethylene at unusually high rates to form linear high-density polyethylene. Even at ethylene pressures as low as 1 atm, the polymerization is extremely exothermic and the crystalline polymer product rapidly precipitates from solution. Computational chemistry is proving to be of utility in understanding the mechanistic aspects of this chemistry. - Lower barriers to insertion, relative to the nickel a-diimine complexes, support the higher activity. 

Polyethylene, linear high-density Polyethylene, linear low-density Polyethylene, low-density Polyethylene, metallocene linear low-density Poly(ethylene-2,6-naphthalate)... 

In the resin manufacturing process, and due to the difficulties in obtaining fast MMD data, homopolymer resins are craitrolled by a parameter related to the average molar mass (M), the melt index, and on occasions by additional rheology measurements that reflect the broadness of the distribution however, when full characterization of a linear high-density polyethylene (HOPE) homopolymer product is required, the whole MMD must be measured. 

Polyethylene. A thermoplastic produced by polymerization of ethylene. Polyethylene has the greatest bulk of all plastics in terms of both production and consumption. Several industrial processes are used for the polymerization of ethylene. Characteristics of polyethylenes produced in different ways are similar but not quite identical. All of them are microcrystalline translucent (seemingly transparent in thin layers) thermoplastics with a lower density than that of water, low permittivity and dielectric loss, and high resistance to acids and alkali. The different types of polyethylenes are principally classified by density. Low-density polyethylene (LDPE) has a rather branched carbon chain with repeated — CHg—CHg— monomeric units and a density of 0.918 to 0.935 g/cm, while the almost linear high-density polyethylene (HOPE) has... 

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