Polyethylene mixtures

Transparency. Alloys of PVC and VC/PE graft copolymer are more transparent than PVC-polyethylene mixtures having the same total polyethylene content. Graft copolymers based on high-density polyethylene give better transparency than do similar graft copolymers based on low-density polyethylene. Perfect transparency, however, cannot be obtained. 

In co-hydropyrolysis experiments without catalysts the degree of pine wood/ polyethylene mixture (1 1 weight ratio) conversion was 80% wt. and yield of the light liquid fraction - 23% wt. The addition of iron ore catalyst activated by mechanochemical treatment increased the degree of mixture conversion by 5-13%. This increase was mainly due to light liquid fraction formation. The variation of catalyst nature (pyrite, pyrrhotite, haematite) influences on the product composition. Pyirhotite catalyst yields the highest amount of the light fraction (about 40% wt.). 

The influence of the process temperature on catalytic hydropyrolysis of biomass/plastic mixture was studied in the range 360 - 460 C. Fig. 3 shows that the highest conversion (91% wt.) of the pine wood / polyethylene mixture (1 1 weight ratio) was observed at 390 C - 430 C in the presence of activated haematite catalyst. Higher tenqieratures promote increased yields of char and gaseous products. At lower temperatures a reduced yield of distillate fraction was observed. In comparison with pyrolysis in inert atmosphere the increased yields of light hydrocarbon fractions (by 1.6 - 1.8 times) and increased degree of mixture conversion (by 1,2 time) were observed for hydropyrolysis process. 

As was noted early, under the action of polyethylene the conversion of pine wood was increased by 1,4 times. After removing 11% wt, of lignin from pine wood by extraction with dimethyl sulfoxide this effect was less (1.2 times). In the runs with cellulose / polyethylene mixtures no positive influence of polyethylene on pine wood conversion was defected. The maximum increase of the conversion degree (1.5 times) was observed for coal / polyethylene mixture. 

Let us consider the application of transition state analysis to interpret the work of Ehrlich and coworkers on the reaction behavior of ethylene polymerization in supercritical ethylene (Ehrlich, 1971). Ehrlich presents experimental data on the polymerization of ethylene at 130°C and 1,500 bar. At these conditions supercritical ethylene can solubilize 5 wt% to 10 wt% high molecular weight polyethylene, which is produced during the reaction. Normally, the conversions are kept to —10% which means that the reacting supercritical ethylene-polyethylene mixture is near a mixture critical point. Ehrlich argues that the partial molar volume of M, which has volumetric... 

Polyethylene and polypropylene are especially interesting as additives for the activation of the cracking reaction of vacuum residue. The data obtained from thermo-gravimetric analysis of polyethylene and polypropylene show that vacuum residue has its maximum cracking velocity at the temperature 456°C, polypropylene at 450°C and polyethylene at 485°C. This means that the cracking of vacuum residue will only be activated if polypropylene is used. In the case of the thermal treatment of vacuum residue and polyethylene mixtures, the cracking of polyethylene will be activated by free radicals from the vacuum residue (see above). 

No such relationship was observed in the case of polyethylene mixtures with butyl rubber (Fig. 6). We came to the conclusion that the activity of polyacrylonitrile as a filler can be connected with EDA interactions between electrons of double bonds and -C E N groups. No such complex type has so far been detected in polymer mixtures. In the given instance an EDA complex could appear only at the interphase boundary and its concentration would be quite low. However, certain symptoms of its existence have been observed. PAN added in the amount of 30 phr raised the cis-1,4-poly-butadiene Tg towards higher temperature region by 4-15 K. This was observed by means of thermomechanical analysis under dynamic as well as under static conditions (Figs. 7 and 8). The presence of the immobilized layer of PB on the PAN domains was also established in studies carried out by the method of pulse NMR. In the mixtures of PB with PAN there appeared additional compliances of the relaxation time T2 "spin-spin" (Fig. 9), as well as relaxation time T "spin-network" (Fig. 10). This indicates that part of the elastomer has... 

ROU Rousseaux, P., Richon, D., and Renon, H., Ethylene-polyethylene mixtures, saturated liquid densities and bubble pressures up to 26.1 MPa and 493.1 K, J. Polym. Sci. Polym. Chem. Ed., 23, 1771 1985. 

SteinCT, R. and K. Hmle, Phase behavior of ethylene polyethylene mixtures under high-pressure. Chemie Ingenieur Technik, 1972. 44(17) p. 1010. 

The MFLG model describes the vapor/liquid critical point (v = 1), v/l equilibrium data and isotherms of pure components such as -pentane and other n-alkanes quite well (Fig. 7) while polymers also fall within the scope of the model. Since linear polyethylene and M-alkanes consist of identical repeat units it has been assumed that, in a first approximation, the parameters for n-alkane/polyethylene mixtures can be set equal to zero [55]. This assumption proved to be too simplistic since the locations predicted for spinodal curves were found to be only in qualitative agreement with the measured curves and locations of miscibility gaps. However, Fig. 8 illustrates that values for mixture parameters can be found that provide a fair description of the measured LCM behavior and its pressure dependence for the system n-alkane/linear polyethylene [56, 57]. The predictive power of the procedure is considerable, as is witnessed by Fig. 9 in which the location of cloud points in pressure-temperature-composition space for -octane/n-nonane/ linear PE mixtures is predicted remarkably well in terms of the nearby spinodals. 

Boscoletto AB, Franco R, Scapin M, Tavan M. An investigation on rheological and impact behaviour of high density and ultra high molecular weight polyethylene mixtures. Eur Polym J 1997 33(1) 97-105. 

PE/asphalt blends, particularly those prepared from soft asphalts. However, it is known that asphalt-polyethylene mixtures have a tendency toward gross phase separation, i.e., gross incompatibility, when standing at elevated temperature for long periods 19]. Therefore modification of PE is needed to enhance its compatibility with asphalt. 

Fig. X-13. Advancing contact angles for methylene iodide-decalin mixtures on polyethylene. (From Ref. 172.)...

A polymer is a macromolecule that is constructed by chemically linking together a sequent of molecular fragments. In simple synthetic polymers such as polyethylene or polystyrer all of the molecular fragments comprise the same basic unit (or monomer). Other poly me contain mixtures of monomers. Proteins, for example, are polypeptide chains in which eac unit is one of the twenty amino acids. Cross-linking between different chains gives rise to j-further variations in the constitution and structure of a polymer. All of these features me affect the overall properties of the molecule, sometimes in a dramatic way. Moreover, or... 

Although Pd is cheaper than Rh and Pt, it is still expensive. In Pd(0)- or Pd(ll)-catalyzed reactions, particularly in commercial processes, repeated use of Pd catalysts is required. When the products are low-boiling, they can be separated from the catalyst by distillation. The Wacker process for the production of acetaldehyde is an example. For less volatile products, there are several approaches to the economical uses of Pd catalysts. As one method, an alkyldi-phenylphosphine 9, in which the alkyl group is a polyethylene chain, is prepared as shown. The Pd complex of this phosphine has low solubility in some organic solvents such as toluene at room temperature, and is soluble at higher temperature[28]. Pd(0)-catalyzed reactions such as an allylation reaction of nucleophiles using this complex as a catalyst proceed smoothly at higher temperatures. After the reaction, the Pd complex precipitates and is recovered when the reaction mixture is cooled. 

Ziegler found that adding certain metals or their compounds to the reaction mixture led to the formation of ethylene oligomers with 6-18 carbons but others promoted the for matron of very long carbon chains giving polyethylene Both were major discoveries The 6-18 carbon ethylene oligomers constitute a class of industrial organic chemicals known as linear a olefins that are produced at a rate of 3 X 10 pounds/year m the... 

Laboratory tests indicated that gamma radiation treatment and cross-linking using triaHylcyanurate or acetylene produced a flexible recycled plastic from mixtures of polyethylene, polypropylene, general-purpose polystyrene, and high impact grade PS (62). 

One of the early popular low power research and training reactors was the AGN-201, suppHed by Aerojet General Nuclear. This is a homogeneous sohd fuel reactor, consisting of a mixture of polyethylene and uranium at 20% enrichment in The core 235U... 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

A classification by chemical type is given ia Table 1. It does not attempt to be either rigorous or complete. Clearly, some materials could appear ia more than one of these classifications, eg, polyethylene waxes [9002-88 ] can be classified ia both synthetic waxes and polyolefins, and fiuorosihcones ia sihcones and fiuoropolymers. The broad classes of release materials available are given ia the chemical class column, the principal types ia the chemical subdivision column, and one or two important selections ia the specific examples column. Many commercial products are difficult to place ia any classification scheme. Some are of proprietary composition and many are mixtures. For example, metallic soaps are often used ia combination with hydrocarbon waxes to produce finely dispersed suspensions. Many products also contain formulating aids such as solvents, emulsifiers, and biocides. 

Isomer mixtures are generally obtained. Chlorosulfonation is used to produce chlorosulfonated polyethylene, a curable thermoplastic. Preformed sulfuryl chloride may also be used. 

In the belt process, the mixture is cast onto the belt or conveyor (high temperature polyethylene (264)) where gelling occurs (261,265). The gel is removed from the surface before syneresis, cut into smaller particles, and passed to a holding or washing tank (Fig. 14). The Hquid is removed from the precipitate using common chemical deHquefying methods, and the resulting particles ate dried in a continuous dryer. 

Some by-product polyethylene waxes have been recently introduced. The feedstock for these materials are mixtures of low molecular weight polyethylene fractions and solvent, generaHy hexane, produced in making polyethylene plastic resin. The solvent is stripped from the mixture, and the residual material offered as polyethylene wax. The products generaHy have a wider molecular weight distribution than the polyethylene waxes synthesised directly, and are offered to markets able to tolerate that characteristic. Some of the by-product polyethylene waxes are distHled under vacuum to obtain a narrower molecular weight distribution. 

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