High-density polyethene

Even more important is the stereoregular catalytic polymerization of ethene and other alkenes to give high-density polyethene ( polythene ) and other plastics. A typical Ziegler-Natta catalyst can be made by mixing TiCU and Al2Eti in heptane partial reduction to Ti " and alkyl transfer occur, and a brown suspension forms which rapidly absorbs and polymerizes ethene even at room temperature and atmospheric pressure. Typical industrial conditions are 50- 150°C and 10 atm. Polyethene... 

Reimann, C., U. Siewers, H. Skarphagen, and D. Banks. 1999. Does bottle type and acid-washing influence trace element analyses by ICP-MS on water samples A test covering 62 elements and four bottle types High density polyethene (HDPE), polypropene (PP), fluorinated ethene propene copolymer (FEP) and perfluoroalkoxy polymer (PFA). Sci. Total Environ. 239 111-130. 

Villberg, K., Veijanen, A., Gustafsson, I., and Wickstrom, K. (1997). Analysis of odour and taste problems in high-density polyethene. ]. Chromatogr. 791, 213-219. 

By far the most important industrial coordination polymerization processes are Ziegler-Natta polymerizations of 1-olefins [107-110], most notably the production of high-density polyethene [111] and stereo-specific olefin polymers and copolymers [108], However, these processes employ solid catalysts, and the complex kinetics on their surfaces have no place in a book on homogeneous reactions. 

The earliest Ziegler-Natta catalysts were insoluble bimetallic complexes of titanium and aluminum. Other combinations of transition and Group I-III metals have been used. Most of the current processes for production of high-density polyethene in the United States employ chromium complexes bound to silica supports. Soluble Ziegler-Natta catalysts have been prepared, but have so far not found their way into industrial processes. With respect to stereo-specificity they cannot match their solid counterparts. 

For urine use high density polyethene containers thoroughly cleaned with Suprapur quality nitric acid and bidistilled water 1 + 10. The container must be tested to deliver less than 10% extraneous amounts of cadmium. Test may be performed with a 1% v/v solution of nitric acid (e.g. Suprapur quality) in bidistilled water. Do not use glassware. 

Phillips process A method for the manufacture of high-density polyethene using a catalyst of chromium(III) oxide on a promoter of silica and alumina. The reaction conditions are 150°C and 30 atm pressure. See also Ziegler process. 

Phillips procass A process for making high-density polyethene by polymerizing ethene at high pressure (30 atmospheres) and 150°C. The catalyst is chromium (111) oxide supported on silica and alumina. 

German chemist Karl Ziegler (1896-1973) discovers catalyst for making high-density polyethene. 

Albertsson AC. The shape of the biodegradation curve for low and high density polyethenes in prolonged series of experiments. Eur Polym J 1980 16 623-630. 

For blood cleaned plastic collection tubes with stoppers and for urine high-density polyethene containers thoroughly cleaned with Suprapur (Merck, Germany) quality nitric acid and bidistilled water 1 + 10 must be used. The whole set (tube and stopper, or container) must be tested to deliver less than 10% extraneous amounts of cadmium. Colored stoppers and plastics with a Cd softener should not be used. Before starting the study six test tubes per tube production lot and during the study frequently blank tubes, e.g., for 1% of the total number of samples to study, must be tested. The test may be performed with a 1% v/v solution of nitric acid (e.g., Suprapur quality) in bidistilled water. Preferably vacuum collection tubes must be used. No special type of needle is requested. Needles of stainless steel are adequate. Other needles, e.g., siliconized or... 

While aluminium alkyls on their own convert ethene into oligomers (p. 80), in the presence of traces of nickel termination occurs after only one step, so that the dimer, butene, is produced. This observation ted Ziegler to study the effect of compounds of other transition metals as cocatalysts. With titanium or zirconium compounds in particular, rapid polymerization of ethene occurs at 50°C/10 atm leading to a crystalline, high density polyethene (HOPE) which consists of long... 

Table 12,3. Consumption of low density polyethene (LDPE), high density polyethene (HOPE) and polypropene (PP) in 1985.

The widely investigated Phillips catalyst, which is alkyl free, can be prepared by impregnating a silica-alumina (87 13 composition [101-103] or a silica support with an aqueous solution of Cr03). High surface supports with about 400 to 600 g/m are used [104]. After the water is removed, the powdery catalyst is fluidized and activated by a stream of dry air at temperatures of 400 to 800 °C to remove the bound water. The impregnated catalysts contain 1 to 5wt% chromium oxides. When this catalyst is heated in the presence of carbon monoxide, a more active catalyst is obtained [105]. The Phillips catalyst specifically catalyzes the polymerization of ethene to high-density polyethene. To obtain poly ethene of lower crystallinity, copolymers with known amounts of an a-olefin, usually several percent of 1-butene ean be synthesized. The polymerization can be carried out by a solution, slurry, or gas-phase (vapor phase) process. 

The main three polyethene classes are low-density polyethene (LDPE), high-density polyethene (HDPE), and linear low-density polyethene (LLDPE) (Scheme 6.20.1). Table 6.20.1 gives an overview of these classes and indicates the differences in density, production processes, and chemical structure. 

PE type Low-density polyethene Linear low-density polyethene (LLDPE) High density polyethene... 

Technical ethylene polymerization leads to three major classes of PE materials low-density polyethene (LDPE), linear low-density polyethene (LLDPE), and high-density polyethene (HOPE). The three classes of PE material differ in the degree and type of branching in the polymer. These differences lead to different physicochemical properties of the polymer, resulting in different application areas of the PE material. 

The ability of supercritical carbon dioxide to penetrate polymer films prompted studies in the activation of high-density polyethene film [16]. UV irradiation of [cp Ir (CO)2] gave changes in the infrared spectrum consistent with formation of [cp Ir (CO) (H) (polymer)], which were retained after subsequent supercritical fluid extraction with carbon dioxide, indicating that the reaction product was chemically bound to the polymer film. 

A HOPE High-density polyethene Milk detergent bottles, plastic bags. 

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