Polyethylene product comparison

Product Comparison Table 11.5 shows typical values for polyethylene pocket materials of course, for the various producers [60-64] (Grace Gmbh (unpublished results)) they vary shghtly owing to differences in formulation and process. An exact comparison is also difficult, since not all producers stating tolerances respectively clarify their statistical base. 

Profile forming is the process by which the molten output from an extruder is shaped and cooled by an extrusion die to form a continuous product with a constant cross-sectional profile. In the case of polyethylene, products are predominantly tubular, with relatively thick walls in comparison to their diameter. 

Whilst it is inevitable that polypropylene will be compared more frequently with polyethylene than with any other polymer its use as an injection moulding material also necessitates comparison with polystyrene and related products, cellulose acetate and cellulose acetate-butyrate, each of which has a similar rigidity. When comparisons are made it is also necessary to distinguish between conventional homopolymers and the block copolymers. A somewhat crude comparison between these different polymers is attempted in Table 11.7 but further details should be sought out from the appropriate chapters dealing with the other materials. 

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. 

In the production mode the rotation rate of the P-CAC can be varied between 0°/h and 5000°/h. By comparison, the drivers used in the CAC units throughout the ORNL studies were only able to rotate the column between 2°/h and 1000°/h. The housing of the drive is made of stainless steel coated with polyethylene and protects the drive as well as the electronic parts against environmental influences. 

Phillips catalysts for linear polyethylene and polypropylene and the graft copolymerizations for impact polystyrene and ABS are even younger and have not yet spread into the less industrialized countries of world. The production of polyolefins, poly (vinyl chloride), and styrene resins on a worldwide basis as well as of all synthetic polymers is shown in Figure 3. A comparison of the U.S. production in Figure 1 and in Figure 3 demonstrates the effect of age and dissemination of technology. It shows that relatively more poly (vinyl chloride) but less polyolefins and styrene resins are produced worldwide than in this country. 

To get a better insight into the chlorination reaction, we wanted to avoid a heterogeneous process. Instead of polyethylene or polypropylene, we used polyisobutene, which is soluble in carbon tetrachloride, as are its chlorination products. In addition, we were interested in the structure and properties of the chlorinated products, especially in comparison with polyvinyl chloride (PVC) and vinyl chloride/isobutene (VC/IB) copolymers. 

Figure 3. Automated C-Terminal Sequencing of the Tripeptide, LAP (15 nmol), Covalently Attached to Carboxylic Acid Modified Polyethylene. Each thiohydantoin derivative is identified by comparison to the retention time of an authentic standard. Unlabeled peaks are background produced by reaction side products.

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. 

Pyrolysis of poly(ethylene-co-methacrylic acid) (10% wt. methacrylic acid), CAS 25053-53-6, also is dominated by the pyrolysis products of polyethylene. The pyrogram of this copolymer obtained at 600° C in He with separation of a Carbowax column is given in Figure 6.1.10, and for comparison, the pyrogram for polyethylene is shown in the same... 

When the monomer ratio in a copolymer increases, the contribution to the pyrolysate also increases. However, the yield of different pyrolysis products depends on the nature of the polymer. In addition to quantitative information, as shown in Chapter 4, structural information can be obtained from pyrolysate. One example in this direction is that of a poly(ethylene-co-methyl acrylate), CAS 25103-74-6, (with butylated hydroxyethyl-benzene inhibitor). A sample with 21.5% wt. methyl acrylate (MAc), with M = 79,000 and Mn = 15,000, pyrolyzed at 600° C in He with the separation on a Carbowax column generates the upper trace of the two pyrograms shown in Figure 6.1.11. The lower trace, displayed for comparison, is that of polyethylene. The peak identification for the pyrogram of poly(ethylene-co-methyl acrylate), with 21.5% wt. methyl acrylate, shown in Figure 6.1.11 was done using mass spectral library searches only, and Is given in Table 6.1.7. 

The solidification of the polymer melt in rotational molding is relatively slow, in comparison to other processes, and is estimated to be in the range of 10-30°C/min. Moreover, the melt solidification is gradual and nonuniform across the molded part thickness, leading to important variations in the morphological features, as illustrated in Fig. 9, and dictating the properties and overall performance of the final product. The effects are more dramatic for resins with slower crystallization rates, such as polypropylene, compared to that observed with polyethylene. 

During photo-oxidation, dicarboxylic acids were the class of products that clearly increased in the most severely degraded samples. As during thermooxidation, the most abundant of the dicarboxylic acids was butanedioic acid. Comparison between the number average molar mass and the relative amount of butanedioic acid, Fig. 6, showed a connection between the formation of butanedioic acid and the degree of degradation in the polyethylene matrix. However, the relative sum of all the carboxylic acids correlated even better with the number of chain scissions than the amoimt of only butanedioic acid. Fig. 7. 

A simple method to measure the membrane permeability to specific molecules has been presented by G. Battaglia and coworkers [141], The authors encapsulated highly hydrophilic 3,3, 3//-phosphinidynetris-benzenesulfonic acid (PH) into polyethylene oxidc)-co-poly(butylene oxide) (EB) vesicles and monitored its reaction with 5,5/-dithiobis-2-nitrobenzoic acid (DTNB) penetrating the membrane from the exterior. The reaction rate (amount of the formed product as a function of time after DTNB addition) measured with IJV/Vis was directly correlated to the permeability of the permeating molecule. A comparison of these results with the permeability of egg yolk phosphatidylcholine (PC) vesicles showed that EB membranes have a more selective permeability toward polar molecules than the phospholipids membranes. Also in this case the permeability appeared to depend on the membrane thickness as predicted by Fick s first law. 

NBS 1475 polyethylene was also subjected to thermal degradation for 24 hours at 500 K and then irradiated in vacuum also at 500 K to 3.0 Mrad. The quantitative results are given in Table IV and the 13c NMR spectrum which yielded these data is shown in Figure 11. As remarkably indicated in Figure 11, the formerly linear NBS 1475 is now extensively long chain branched. From a comparison of relative peak areas, the concentration of long chain branches is now approximately 44 per 10,000 carbon atoms. There are two more products formed under these conditions the concentration of saturated end groups is now 94 per... 

Routledge et al. [7] investigated the formation of dihydrobenzofuran 1 from an aryl halide precursor (Scheme 1). With polystyrene, more than 1 equivalent of AIBN was required, while the reaction was complete within 20 h using 6 mol% of AIBN on TentaGel resin (which has a polyethylene spacer between the polystyrene and the site of compound attachment). Addition of t-butanol helped prevent an alternative y -elimination pathway. An attempt to force the latter was made with thiyl linker 2, but only trace amounts of the )9-elimination product 3 were formed. Also investigated were the cyclizations of iodides 4, in which the cyclization of an alkyl radical to an acetylene is approximately 10 times slower than the aryl radical cyclization to a double bond. A direct comparison of the same reaction on solution phase was attempted, but yields could not be determined for the latter because of contamination by tin residues. This illustrates one advantage of solid-phase radical reactions mediated by tributyltin hydride, namely the ease of product purification. 

Comparison of the distribution of products from decomposition of polyethylene and polypropylene at 673 K co-milled with silica-alumina catalyst (13.2 wt% alumina) ... 

Table 6 Comparison of the decomposition products of polyethylene at 375 "C and W/F= 13 over HZSM-5 and HY catalysts in fixed bed tubular flow reactor ...

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