High density polyethylene material

Density is a consequence of structure and allows low, medium and high density polyethylene material to be distinguished. 

Fig. 4.185 Time to fracture as a function of applied load for high-density polyethylene materials having different molecular weight in 5 % solution of nekantil at 50 °C using the constant tensile stress method [07Ram].

It is important to observe that the experimental framework used in this work was designed to allow a comparative study of the mechanical strength properties of non-irradiated and irradiated samples of a specific high-density polyethylene material. Thus, the validity of the data and conclusions obtained is limited by the assumptions and material used. In order to produce more general data, it is desirable to make use of other complementary tests to better characterize the changes in the microstructure of the material due to the application of gamma radiation. 

Boldizar, A., Jansson, A. et al. Simulated recycling of post-consumer high density polyethylene material. Polymer Degradation and Stability, 68 (2000), p. 317-319... 

Ultra high molecular weight polyethylene (UHMWPE) is high-density polyethylene material. Chemically, high-density polyethylene (HOPE) and (UHMWPE) are identical both are straight chain linear polymers. The molecular weight of conventional HOPE is rarely above 50,000 g/mol, whereas ASTM definitions require molecular weight of UHMWPE above... 

United States The Ziegler route to polyethylene is even more important because it occurs at modest temperatures and pressures and gives high density polyethylene which has properties superior to the low density material formed by the free radical polymerization described m Section 6 21... 

Table 6 shows the sales estimates for principal film and sheet products for the year 1990 (14). Low density polyethylene films dominate the market in volume, followed by polystyrene and the vinyls. High density polyethylene, poly(ethylene terephthalate), and polypropylene are close in market share and complete the primary products. A number of specialty resins are used to produce 25,000—100,000 t of film or sheet, and then there are a large number of high priced, high performance materials that serve niche markets. The original clear film product, ceUophane, has faUen to about 25,000 t in the United States, with only one domestic producer. Table 7 Hsts some of the principal film and sheet material manufacturers in the United States.

Structural Components. In most appHcations stmctural foam parts are used as direct replacements for wood, metals, or soHd plastics and find wide acceptance in appHances, automobUes, furniture, materials-handling equipment, and in constmction. Use in the huil ding and constmction industry account for more than one-half of the total volume of stmctural foam appHcations. High impact polystyrene is the most widely used stmctural foam, foUowed by polypropylene, high density polyethylene, and poly(vinyl chloride). The constmction industry offers the greatest growth potential for ceUular plastics. 

Plastic materials represent less than 10% by weight of all packagiag materials. They have a value of over 7 biUion including composite flexible packagiag about half is for film and half for botties, jars, cups, tubs, and trays. The principal materials used are high density polyethylene (HDPE) for botties, low density polyethylene for film, polypropylene (PP) for film, and polyester for both botties and films. Plastic resias are manufactured by petrochemical companies, eg. Union Carbide and Mobil Chemical for low density polyethylene (LDPE), Solvay for high density polyethylene, Himont for polypropylene, and Shell and Eastman for polyester. 

Nor is it tme that poly(ethylene terephthalate) (PET) and high density polyethylene (HDPE) packaging are hsted as 1 and 2 in the Society of the Plastics Industry (SPI) recycling coding system because they are the most recyclable. The numbers assigned to each plastic in the SPI coding system are purely arbitrary and do not redect the material s recyclabihty. 

High density polyethylene is widely used for pipes and drains, especially in large-diameter cormgated forms. The cormgations provide stronger walls at less thickness, which reduces the materials cost of the pipe. 

Chloroformates are shipped in nonretumable 208-L (55-gal) polyethylene dmms with carbon steel overpacks or high density polyethylene dmms. Eor bulk shipments, insulated stainless-steel tank containers and tmcks provide secure protection. Tank tmck and rail car quantities are shipped using equipment dedicated for these types of products. Materials such as isopropyl chloroformate, benzyl chloroformate, and j -butyl chloroformate that require refrigeration are precooled when shipped in bulk containers. Bulk shipments that are precooled must proceed to the destination without layover. Dmm shipments of IPCE, BCE, and SBCE must be shipped in refrigerated containers. Many of the chloroformates are only shipped in tmck load shipments. The U.S. Department of Transportation (DOT) Hazardous Materials Regulations control the shipments of chloroformates, as described in Table 3. 

The Phillips-type catalyst can be used in solution polymerization, slurry polymerization, and gas-phase polymerization to produce both high density polyethylene homopolymers and copolymers with olefins such as 1-butene and 1-hexene. The less crystalline copolymers satisfy needs for materials with more suitable properties for certain uses that require greater toughness and flexibiUty, especially at low temperatures. 

In the mid-1950s a number of new thermoplastics with some very valuable properties beeame available. High-density polyethylenes produced by the Phillips process and the Ziegler process were marketed and these were shortly followed by the discovery and rapid exploitation of polypropylene. These polyolefins soon became large tonnage thermoplastics. Somewhat more specialised materials were the acetal resins, first introduced by Du Pont, and the polycarbonates, developed simultaneously but independently in the United States and Germany. Further developments in high-impact polystyrenes led to the development of ABS polymers. 

Following the considerable commercial success of Ziegler-Natta polymerisation systems which made possible high density polyethylene, polypropylene, ethylene-propylene rubbers and a number of speciality materials, a considerable... 

Tension Above materials plus High-density polyethylene Polypropylene Acetal polymers Aliphatic polyamides (nylons) PPO Poly(ethylene terephthalate) Polysulphones... 

Mention may also be made of an application in which careful control of polymer morphology has led to the production of novel materials. By treatment of solutions of high-density polyethylene, products are obtained with a celluloselike morphology and which are known as, fibrides or synthetic wood pulp. They are used for finishing paper and special boards to impart such features as sealability and improved wet strength. They are also reported to be used for such diverse applications as tile adhesives, thixotropic agents, battery separators and teabags ... 

A somewhat different approach to the production of thermoplastic polyolefin rubbers has been adopted by Allied Chemical with their ET polymers. With these materials butyl rubber is grafted on to polyethylene chains using a phenolic material such as brominated hydroxymethyl phenol. The initial grades of these polymers, which were introduced commercially towards the end of the 1970s, had polyethylene butyl rubber ratios of 50 50 and 75 25. Both low-density and high-density polyethylene-based varieties were produced. 

Leaving aside rayon and artificial silks generally, the first really effective polymeric textile fibre was nylon, discovered by the chemist Wallace Hume Carothers (1896-1937) in the Du Pont research laboratories in America in 1935, and first put into production in 1940, just in time to make parachutes for the wartime forces. This was the first of several major commodity polymer fibres and, together with high-density polyethylene introduced about the same time and Terylene , polyethylene tereph-thalate, introduced in 1941 (the American version is Dacron), transformed the place of polymers in the materials pantheon. 

High Density Polyethylene (HDPE). This material has a density in the range 935-965 kg/m and is more crystalline than LDPE. It is also slightly more... 

Polyethylene films as packaging material "plastic" squeeze bottles are molded from high-density polyethylene. 

Terpene monomers are another class of interesting natural monomers because they give, on polymerization, hydrocarbon therplastic resins that exhibit a high degree of tackiness useful in pressure sensitive tapes [25]. They are also used for sizing paper and textile materials. Terpene-phenol resins are effective heat stabilizers for high-density polyethylene. 

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