Polyethylene purified

Figure 2.3 Thermogravimetric analysis curves for polyethylenes in air (O) unpurified polyethylene, ( ) purified polyethylene.

Water. Distilled water must be (a) redistilled in an all-Pyrex glass apparatus or (b) purified by passage through a column of cation exchange resin in the sodium form. For storage, polyethylene bottles are most satisfactory, particularly for very dilute (0.00 lAf) EDTA solutions. 

Reagents such as water, ammonia, hydrochloric acid, nitric acid, perchloric acid, and sulfuric acid can be purified via distillation (preferably under reduced pressure and particularly with perchloric acid) using an allglass still. Isothermal distillation is convenient for ammonia a beaker containing concentrated ammonia is placed alongside a beaker of distilled water for several days in an empty desiccator so that some of the ammonia distils over into the water. The redistilled ammonia should be kept in polyethylene or parafrin-waxed bottles. Hydrochloric acid can be purified in the same way. To ensure the absence of metal contaminants from some salts (e.g. ammonium acetate), it may be more expedient to synthesise the salts using distilled components rather than to attempt to purify the salts themselves. 

Ceruloplasmin (from human blood plasma) [9031-37-2] Mr 134,000. This principle Cu transporter (90-90% of circulating Cu) is purified by precipitation with polyethylene glycol 4000, balchwise adsorption and elution from QAE-Sephadex, and gradient elution from DEAE-Sepharose CL-6B. Ceruloplasmin... 

In 1971, Hiatt et al. found that polyethylene oxide (PEO) of molecular weight about 100000 prevented the adsorption of rabies virus to porous glass with an average pore diameter of 1250 A. The support was modified by passage of one void volume of 0.4% solution of the polymer in water, followed by 5 or more volumes of distilled water or buffered salt solution. The virus was effectively purified from the admixtures of brain tissue fluid by means of size-exclusion chromatography on the modified glass column [28]. 

Terephthalic acid (p-TA or TA), a raw material for polyethylene terephthalate (PET) production, is one of the most important chemicals in petrochemical industry. Crude terephthalic acid (CTA), commonly produced by homogeneous liquid phase p-xylene oxidation, contains impurities such as 4-carboxybenzaldehyde (4-CBA, 2000-5000 ppm) and several colored polyaromatics that should be removed to obtain purified terephthalic acid (PTA). PTA is manufactured by hydropurification of CTA over carbon supported palladium catalyst (Pd/C) in current industry [1]. 

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

Selexsorb A five-stage process for purifying ethylene before converting it to polyethylene. Developed by the Industrial Chemicals Division of the Aluminum Company of America. More than 50 installations were operating in 1996. The name is now used for a family of selective adsorbents based on alumina produced by Alcoa. The range includes Selexsorb CD, CDO, CDX, COS, SPC1, HC1. 

Fig. 17 a Classical self-nucleation behavior for polyethylene (PE) within E18EP57EO25133 triblock copolymer [101]. b Self-nucleation behavior for PEO within purified E24EP57EO1964 triblock copolymer [29], c Self-nucleation behavior for PE within S35E15C50219 triblock copolymer [29,98]. (a, c from [98,101] with permission, b Reprinted with permission from [29], Copyright 2002 American Chemical Society)... 

While the extracts of SPMDs are generally less difficult to purify than are extracts of tissue or sediment, certain interferences can be problematic for some types of analyses. The most important of these potential interferences are codialyzed polyethylene oligomers (i.e., the so-called polyethylene waxes), oleic acid, and methyl oleate. The latter two interferences are residual from the synthesis of the triolein. Also, oxidation products of triolein may be present in dialysates of SPMDs that have been exposed (especially in the presence of light) to air for periods exceeding 30 d. For a standard 1-mL triolein SPMD, the mass of all these interferences in dialysates is generally <30 mg or about 6 mg g of SPMD (Huckins et al., 1996). Another potential interference is elemental sulfur, which is often present in sediment pore water and is concentrated by SPMDs. However, both polyethylene waxes and elemental sulfur are readily removed using the previously described SEC procedure. 

D. Axelson The low density (branched) polyethylenes were free radical initiated the linear polymers were derived from commercial sources and purified and characterized as described (Macromolecules 10, 550(1977)). 

A VaporSep system was installed at a polyethylene plant to recover 290 lb of ethylene per hour (Ib/hr) from a gas stream consisting of 18% hydrogen, 22% nitrogen, 30% methane, and 30% ethylene. The capital costs for the system were 200,000. Based on an ethylene value of 300 per ton, the plant would save 370,000 per year using the VaporSep system to purify and recycle the ethylene (D205549, p. 5). 

S Gas-Phase Polymerization. Not all polymerization reactions are carried out in the liquid phase. Polyethylene, for example, can be polymerized not only in solution as discussed in Section 3.3.2.2, but also through gas-phase polymerization (see Figure 3.28). Significant economic advantage is gained by eliminating costly solvent and catalyst recovery equipment. A fluidized bed reactor is used, into which purified... 

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