Polyolefins polyethylene construction

Lower-density E-plastomers have found alternate use in cast film processes to make elastic film laminates with good breathability which contain laminates of liquid impermeable extensible polymeric films with extensible-thermoplastic-polymer-fiber nonwovens and nonwoven webs of polyethylene-elastomer fibers as the intermediate layers. The development relates to a breathable film including an E-plastomer and filler that contributes to pore formation after fabrication and distension of the film. The method and extent of distension is designed to produce a breathable film by stretching the film to form micropores by separation of the film of the E-plastomer from the particulate solids. This film is useful for manufacture of absorbent personal-care articles, such as disposable diapers and sanitary napkins and medical garments. In detail, these constructions comprise a liquid impermeable extensible film comprising polyolefins. The outer layer contains extensible-thermoplastic-polymer-fiber nonwovens, and an elastic intermediate layer contains nonwoven webs of fiber E-plastomers. The intermediate layer is bonded to the film layer and the outer... 

Helmet shells requiring protection from moderate intensity, single-impact scenarios are commonly constructed with polyolefin materials such as polyethylene (PE) and polypropylene (PP). Sport helmets with PE and PP outer shells include recreational levels of cricket, ice hockey, equestrian, alpine sports, and action adventure sports. In comparison with PC and ABS shells, the diminished magnitude and frequency of expected impact events for polyolefin shells precludes the use of many additives on a cost-per-helmet basis. Caswell et al. (2007) offer a more thorough review of relative performance selection criteria for helmet shell materials. 

Silicone, polyethylene (PE), and polyolefin have all been used as a flexible hinge to replace a joint of the hand damaged through injury or arthritis. The most widely accepted implant for this application was designed by Swanson in the 1960s and continues to be used today (Linscheid, 2000). Constructed of Silastic, a form of silicone rubber, it achieves fixation through the planned formation of a fibrous capsule around the implant. Such capsular formation is a standard response to implanted structures in the body, but in many cases it has been determined to be contraindicated for optimal... 

Polyethylene (PE) and polypropylene (PP) exemplify a class of materials called polyolefins. Composites based on these resins are relatively new by the standards of those early materials of construction. Recent efforts to use these types of materials combine inherent cost-effectiveness with a wide spectrum of end-use applications as film, fiber, and moldings. The impetus for this remarkable development is attributed to the ease of polyolefin manufacture with effective production and purification of the monomers from a variety of sources, ongoing improvements of the catalyst, and large well-controlled polymerization units. Consequently, a strong market demand for good performance and cost-effective materials have spurred a multibillion dollar industry. 

It is clear that a non-metallic construction would be favoured. A number of non-metallic contenders existed. GRP was not favoured originally because problems had arisen at an earlier installation in which it was used (but see paragraph 24.3.3 below). Similarly extruded PVC pipe was quickly eliminated. Polypropylene lined GRP was rejected because of uncertainty at the time about its manufacture and performance. This left the polyolefins as the strongest contender, and high-density polyethylene (HOPE) and polypropylene (PP) were compared. HOPE was eventually favoured for the following reasons... 

Hostalen A slurry process for making high-density polyethylene using a Ziegler catalyst. Two reactors are used, in series or in parallel, which permits the produetion of a variety of molecular weight distributions. Developed and licensed by Basell Polyolefins. In 2005, 33 plants were operating or under construction. Hostalen is also a trade name for the polymer produets. See also next entry. 

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