Commercial polyethylene comparison

COMPARISON OF FOUR COMMERCIAL LINEAR AQUEOUS SIZE EXCLUSION COLUMNS AND FOUR SETS OF COMMERCIAL POLYETHYLENE OXIDE (PEO) STANDARDS FOR AQUEOUS SIZE EXCLUSION CHROMATOGRAPHY OF POLYVINYLPYRROLIDONE AND PEO... 

Figure 3.15 Comparison of the molecular weight distribution for HDPE prepared from the Bis(triphenylsilyl) chromate catalyst and the Phillips catalyst labeled as the commercial polyethylene curve. Reprinted from [17] with permission from John WUey and Sons.

Although commercial assays for direct serum analysis of rTj are available, kit procedures are not as convenient as are those for other thyroid hormones and no rTs method has been adapted to an automated platform because this measurement has no recognized diagnostic value. In comparison with the reference method described by Chopra,the typical kit procedure is relatively fast it requires a 3-hour incubation at room temperature, followed by polyethylene glycol precipitation and centrifugation. The entire procedure requires less than 6 hours to perform. 

The most important commercial blends of BPA-PC are poly(acrylonitrile-butadiene-styrene) (PC/ABS) and polybutylene terephthalate (PC/PBT) or polyethylene terephthalate (PET). Commercial grades of PC/ABS include CYCOLOY (GE), Bayblend (Bayer), and PULSE (Dow). PC/ABS blends exhibit improved flow and processability and enhanced low-temperature impact strength in comparison to PC (Fig. 3). These blends are widely used in applications requiring enhanced impact resistance, such as interior automotive parts and computer and electronics applications such as computer housings and cell phones. Non-halogenated flame-retardant PC/ABS blends are widely available. Poly(acrylic-styrene-acrylonitrile) (PC/ ASA) blends (GELOY , GE Luran , BASF) provide improved weatherability for outdoor applications such as exterior automotive parts, but exhibit reduced impact performance at low temperatures in comparison to PC/ABS. PC/PBT or PET blends (XENOY , GE Makroblend , Bayer) provide enhanced chemical resistance and weatherability for applications such as lawn and garden equipment and automotive bumpers and fasdas. 

In the solution process, a hydrocarbon solvent at a temperature of 125-250 °C dissolves the polymer as it forms [2,13,19,710-716]. This was the earliest commercial process developed for linear polyethylene. To prevent the solution from becoming too viscous, the polymer concentration is usually low in comparison with those of other processes, and the polymer MW must usually be kept low. In the recovery of the polymer, the solvent must be vaporized, leaving a polymer melt or sometimes a pulp, which is then pelletized in a further solvent removal step. 

Capillary rheometer extrusion tests were performed by monitoring the applied pressure and the extrudate appearance as a function of the deformation (shear) rate, for blends of the arborescent copolymers at 0.5% w/w with a commercial linear low density polyethylene (LLDPE) resin. In all cases, the backpressure was reduced for the blends as compared to virgin LLDPE however, the performance of the arborescent additives was inferior to a commercial additive used for comparison. 

From a mechanical point of view, high density polyethylene (HDPE)/isotactic polypropylene (iPP) blend have generally been considered as very unsatisfactory materials In particular, they show very poor ultimate mechanical properties at room temperature in comparison with those of the blend constituents. This fact precludes their use for most commercial purposes. In previous papers we found that it is possible to improve the mechanical tensile performance of these blends by appropriately varying the testing conditions such as the temperature and the drawing rate. 

We continued with the investigations on the commercial grade polyethylene Lupolen 4261 A, which turned out to be the lowest loss material measured so far. This material contains uncommonly small concentrations of chemical admixtures and antioxidants of only 1.4 percent. The chemical features of these admixtures are not known in fact, the general uncompleteness of the polymer s specifications make a direct comparison of the vast literature on isolation data very unsatisfying. Therefore, modificaiiions of the same material seem to be the only way to locate the structural units responsible for the respective loss profile. 

Many research groups have applied this synergistic combination of GPC separation and IR detection for various samples in many application areas details can be found in Refs. [6b, 6c]. Willis and Wheeler demonstrated the determination of the vinyl acetate distribution in ethylene/vinyl acetate copolymers, the analysis of branching in high-density polyethylene, and the analysis of the chemical composition of a jet oil lubricant. Provder et al. showed that all of the additives in powder coatings could be positively identified by SEC-FTIR through comparison with known spectra. Even biocides in commercial household paints could be analyzed. 

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