High-density plastics

Fig. 2ab. Photomicrographs of foam cell stmcture (a) extmded polystyrene foam, reflected light, 26 x (b) polyurethane foam, transmitted light, 26 x (c) polyurethane foam, reflected light, 12 x (d) high density plastic foam, transmitted light, 50x (22).

The removal of a high density plastic such as PVC from HIPS, ABS), and poly(ethylene) can be readily achieved using a hydrocyclone. Also, a partial separation of HIPS from ABS is possible (123). 

CO sensor allows detection of CO in the presence of hydrocarbons and other adsorbable contaminants. The membrane Is usually chosen for Its ability to protect the sensing electrode. However, If It has low permeability to air, the sensor will have a slower response time. The electrolyte and counter electrode have also been reported as Influencing selectivity and device performance In the determination of hydrazines (5) and NO2 (9), respectively. Finally, materials of construction are typically Teflon and high-density plastics like polypropylene because such materials must be compatible with reactive gases and corrosive electrolytes. 

Fillers, stabilisers and colorants can be inorganic or organic, and are added as part of identification, stability and durability, they must be non-leaching and meet health requirements. Some plastics products are required to keep moisture and air out of sensitive products and these are usually high-density plastics with low permeation properties. Some products require plastics with high permeability to allow air (oxygen) as part of product stability, e.g. anaerobic adhesives. Healthcare products require that some containers do not allow air or moisture to permeate the surfaces (bacteria or other micro-organisms) and in some extreme cases may require that the inside be coated with an inner layer of approved lacquer or other very low permeable material. 

Ziegler-Natta catalyst See catalyst, Ziegler-Natta. Ziegler process A process for the low-pressure linear polymerization of ethylene and stereospecific polymerization of polypropylene. The product is a high-density plastic or elastomer. It is named for Karl Ziegler, the German scientist who was corecipient (with Giullo Natta, Italy) of the Noble Prize in 1963. See catalyst polymerization polymerization history. 

New and unique methods have also been developed to produce a superior plug, machined with an outer seamless shell of high-density plastic foam, which is strong but light for easy handling, and evenly absorbs heat generated in the mold-making process. 

Low-density plastics are more resistant than high-density plastics. 

High Density Plastics Ltd Commercial Street Todmorden Yorks Todmorden 2457... 

A vibrating screen may be firmly mounted on a vibration system below the screen, or it may be suspended by cables from the overhead vibration mechanism. These two are shown in Figure 3.12. Modem constmction methods tend to use stainless steel screen elanents and high-density plastic constmction materials for the remainder, to give a reduction in mass, so enabling lower power motors to drive the system, making the operation much more energy efficient. 

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