Polyolefin crosslinking

Rodriguez-Perez, M. A. Crosslinked Polyolefin Foams Production, Structure, Properties, and Applications. Vol. 184, pp. 97-126. 

In the manufacturing of crosslinked polyolefin foam, the foam expansion and cell stabilization highly dependent on the degree of crosslinking. It has been reported that at higher crosslinking level the foam produce have higher density [1, 2]. 

A review is presented of the nitrogen autoclave process for the manufacture of crosslinked polyolefin foams. Process and product developments over the last few years are summarised and future possibilities are described. Process developments include use of higher temperatures and pressures to produce foams having densities as low as 10 kg/cub.m. Product developments include foams based on HDPE/LDPE blends, propylene copolymers and metallocene-catalysed ethylene copolymers. The structure and properties of these foams are compared with those of foams produced by alternative processes. 5 refs. 

Mainz, Germany, 4th-5th Nov. 1997, p.277-89. 6124 NEW MODIFIED AZODICARBONIC ACID DIAMIDE FOR CROSSLINKED POLYOLEFIN FOAMS... 

New theories and findings on the formation of ionic species and radicals, which become trapped in the polymers, are discussed in the first two chapters, written by the two European authorities, Chapiro and Charlesby. The kinetics of crosslinking polyethylene is the subject of the American authority, Dole. A higher yield of crosslinking polyolefins was observed in the presence of nitrous oxide by the Japanese scientist, Okada. 

Higher temperature requirements for automotive applications shifting from PVC to crosslinked polyolefin... 

Grafting reaction Reaction of a monomer and a polymer to form a grafted polymer or copolymer Grafting vinyl silanes onto polyolefins for crosslinked polyolefins acrylic acids onto polyolefins for hydrophilicity maleic anhydride onto polyolefins for compatabilization... 

Further developments are still being made in membrane materials and membrane modules. There are reports, in particular, of hydrophobic membranes made of polyolefins, crosslinked polyolefins, polyamides, polyaramids, poly(vinylidene fluoride), PTFE, polyimides, and suchlike. 

Apizero. [API Applicazion Plastiche Industrial ] Crosslinkable polyolefins. 

The attachment of trialkoxysilane functionality to polyolefins (HDPE, LDPE, PP) though grafting of vinylsilanes e.g. 40, 41) or silane functional acrylates e.g. 42) has been widely studied. The principal application of these materials is the preparation of moisture curable crosslinked polyolefins that arc widely used in the cable industry. Silane treatment has also been used for surface modification of polyolefins " and silane grafted polyolefins might also serve as precursors to graft copolymers. 

The entire class of olefin polymers tends to have a linear structure. Some branching is possible, but highly branched polymers are not usually formed. Crosslinkages between chains may also be formed, but such materials are a small part of the total production. Crosslinked polyolefins, especially polyethylene, have been developed to improve on the standard polymer s tendency to creep or cold flow under the influence of temperature, load, and time. However, these polymers are usually thermoplastics. The general linear structure also indicates suitability for fiber and film applications, which are common. 

Crosslinking is a widely used method for modification of pol5nner properties. The process consists in a formation of a tii-dimensional network structure, a gel, causing substantial changes in the material properties. Vulcanized rubbers and thermosetting resins can be mentioned as the most common examples of crosslinked systems. However, crosslinked polyolefins are of significant interest as well. 

Chodak, I. (1995) Properties of crosslinked polyolefin-based materials. Prog. Polymer Sci., 20, 1165-1199. 

The family of elastomers known as thermoplastic elastomers (TPEs) are based on crosslinked polyolefin alloys and are compounded with common... 

Typ Azodicarbonamide. For tha extrusion foam process of crosslinked polyolefins. 

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