LDPE Results

Additive-free grannlar LDPE was PETKiM Commercial Code Nnmber FI2, obtained from PETKlM Petrochemical in Aliaga, Turkey. The particles were separated by ISO 3310-1 standard sieves into three size ranges, namely 150-212 p,m, 75-150 tim, and less than 75 ttm diameter. After calibration for each of these ranges, the voltage of the DC motor driving the feeder was appropriately set to render an approximate feed rate of 2 g/min. 

The first set of experiments used LDPE particles in the 150-75 p,m size range and varied the reactor temperature between 750 and 875°C. As seen in Eigure 23.3, both 

The substantial increase (more than 50%) in the gas yield more than compensates for the slight drop (from 67.2 to 64.3%) in its ethylene monomer content. Thus operation at higher temperatures is desirable. This work is eminently superior in respect of ethylene 

The free-fall reactor operating under vacuum has the added advantage over both the sweeping fixed bed and fluidized-bed reactor types that it does not dilute the gaseous products with an inert. 

It is interesting to compare flash vacuum pyrolysis of LDPE and PS in a free-fall reactor. Temperature rise causes the solid residues to fall and the liquid and gas yields to increase. The LDPE figures exceed the corresponding PS values in the case of the solid residue and gas yield by about 50 and 10% respectively. In contrast, the liquid yield of LDPE is about one-fifth of PS. These findings are in harmony with the activation energies 270-331 kJ/mol for LDPE and 126-151 kJ/mol for PS [34]. 

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C-P4-C can undergo intra- and intermolecular photoreactions. Irradiation of <5 X 10 4 M C-P4-C in an organic solvent such as benzene results primarily in intramolecular syn head-to-tail cyclomer (Fig. 12). Upon irradiation of more concentrated solutions, a large amount of oligomeric material was formed. For example, at concentration of 1 X 10-3 M, -20% of oligomers were present in the product mixture. As observed in the case of the N-P -N, irradiation of 1 X 10 2 mol/g-film C-P4-C in LDPE resulted in conversion to intramolecular cyclomer. As in the case of irradiations in homogeneous solutions, only the syn head-to-tail... 

Scheme 1.41. Back-biting during high-pressure polymerization of ethylene to LDPE results in n-hutyl branch formation.

Replacing Z-N-LLDPE by m-LLDPE in blends with LDPE resulted in an improvement of film properties. This may originate from improved miscibility, which in turn depends on the MW of m-LLDPE, branch content (BC), and composition distribution (CD) (Hussein et al. 2003 Hussein and Williams 2004). In addition to the improved physicomechanical properties, the processability of m-LLDPE blends with LDPE is better than that of Z-N-LLDPE. LDPE/ m-LLDPE blends with the same MI as those with Z-N-LLDPE are inherently tougher thus, they may be thinner for the equivalent mechanical properties in... 

Introduction of WF in LDPE results in a slight increase in the viscosity of the melt. The addition of 10% NR is not conducive to change the value of the indicator, while 20% NR plasticizes polymer composite during the heating process, which improves its workability. When adding EPDM observed the opposite result, as in the processing of cross-linked EPDM [11], which leads to a sharp increase in the viscosity of the melt, as a consequence of the material does not flow. 

Kendall and Sherliker [61,62] have shown that milling carbon black into LDPE results in a dramatic decrease in the tear strength of the system despite the fact that the polymer molecules are bound to the filler in a layer 2-3 nm... 

The density of LDPE for film ranges from <0.92 to approximately 0.93 g/cm. The resin is melted in a heated extmder and converted to film by extmding through a circular die. The resulting tube is collapsed and sHt into film ranging in gauge from less than 0.25 mm to greater than 0.75 mm. Some... 

Hypercompressors. In an LDPE plant a primary compressor, usually of two stages, is used to raise the pressure of ethylene to about 25—30 MPa and a secondary compressor, often referred to as a hypetcomptessot, is used to increase it to 150—315 MPa (22,000—45,700 psi). The thermodynamic properties of ethylene ate such that the secondary compressor requires only two stages and this results in a large pressure difference between the second stage suction and discharge pressures. 

Ethyl aluminum dichloride (EADC) is used in the rnanufacmre of certain catalysts for making LDPE. Occasionally, the batch operation involving the catalyst production results in an off-spec lot. This off-spec lot is washed from the reactor (impregantor) with water and hexane, and must be sent to a waste disposal facility. The facility treats this waste in a hydrolysis reaction (i.e., with water and mild agitation). If the reaction is exothermic, what are the potential air pollution and fire problems associated with the waste treatment ... 

As nitrogen compounds are known to improve the LOI values of phosphorus FR positively, the effect of a few nitrogen compounds such as urea, melamine, HMTA, etc. were studied. Table 11 shows that nitrogen gives a synergistic effect with phosphorus in cellulose. Similar results have also been observed for LDPE. 

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]. 

MWBD RESULTS FOR COMMERCIAL HIGH PRESSURE LDPE... 

Applications Caceres et al. [114] compared various methods for extraction of Tinuvin 770 and Chimas-sorb 944 from HDPE pellets, namely room temperature diffusion in CHC13 (20 % extraction), ultrasonica-tion (20% extraction), Soxtec extraction with DCM (nonsolvent) (50 % extraction), dissolution (dichloroben-zene)/precipitation (2-propanol) (65-70% recovery) and boiling under reflux with toluene (solvent) at 160 °C (95 % extraction). By changing conditions (nature of solvent, T, t) similar comparisons do not have much added value. Table 3.6 compares the results of reflux extraction and MAE for additives in LDPE [115]. 

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