Processing, polymer polyolefins

Plastomers represent a major advancement for polyolefins. Their success allows polyolefins to have a continuum of products from amorphous EPR to thermoplastic PE and iPP. This development coincides with the advent of single-site catalysts these are necessary for copolymers of components of widely different reactivity such as ethylene and octene. Their rapid introduction into the mainstream polymer use indicates that this spectrum of properties and the inherent economy, stability and processibility of polyolefins are finding new applications to enter. 

Recall that in the process of low-pressure moulding, thermoplastic polymers (polyolefins, polyamides, or their compositions) are loaded into a cylinder of the adiabatic extruder, plasticized and injected into a mould at low pressure. The formed article is cooled in the mould and removed due to shrinkage phenomena. 

Oxidative degradation of polyethylene (PE) and polypropylene (PP) can occur at all stages of their lifecycle (polymerisation, storage, processing, fabrication and in-service). The auto-oxidation process of polyolefins is best described by the classical free-radical-initiated chain reaction outlined in Scheme 1 [1]. Impurities initially present in the polymers during polymerisation or melt processing, exert profound effects on the behaviour of the final polymer article in service. 

Although solution blending has only been used at the lab scale at this time, compared with the in situ process, it may be more industrially friendly, particularly for the primary polymer producers who have operations, which can easily recover and recycle the solvent. High dilution is required and this may have an effect on the production of the PNs and the process is quite dependent on the individual polymer. Some polymers have many solvents from which to choose while others do not. A typical example is polystyrene, which can dissolve in a variety of solvents, so it is easy to find a solvent that is compatible with both the clay and the polymer. Polyolefins, on the other hand, require high boiling solvents and the high temperature may exert an effect of thermal degradation on the modifier. 

Scientific and technological progress, like other areas of human endeavor advances by a cyclical process of gradual evolution interspersed -with occasions of scientific revolution (Mark 1987). For example, let s consider Figure 10-1, which illustrates the development of polymer science through the commercialization of one family of polymers, polyolefins (Sinclair 2001). One could construct a similar plot for other families of polymers. Revolutionary episodes... 

Hinsken, H. Moss, S. Pauquet, J.-R. Zweifel, H. Degradation of polyolefins during melt processing. Polym. Deg. Stab. 1991, 34, 279-293. 

Secondary aromatic amines are effective antioxidants in the protection of saturated hydrocarbon polymers (polyolefins) against autooxidation. Their role in the stabilization of unsaturated hydrocarbon polymers (rubbers) is more complex depending on their structure, they impart protection against autooxidation, metal catalyzed oxidation, flex-cracking, and ozonation. The understanding of antioxidant, antiflex-cracking and antiozonant processes together with involved mechanistic relations are of both scientific and economic interest. 

Neuhaus S, Padeste C, Spencer ND. Functionalization of fluropolymers and polyolefins via grafting of polyelectrolyte brushes from atmospheric-pressure plasma-activated surfaces. Plasma Process Polym 2011 8(6) 512—22. 

J.J. Robin, C. Boyer, B. Boutevin, C. Loubat, S)mthesis and properties of polyolefin graft copolymers by a grafting onto reactive process. Polymer 49, 4519-4528 (2008)... 

Novak, V. Poliak, I. Chodak, Study of surface properties of polyolefins modified by corona discharge plasma. Plasma Process. Polym. 3, 355-364 (2006)... 

Zaharescu, T., Chipara, M., Postolache, M., Radiation processing of polyolefin blends. II. Mechanical properties of EPDM-PP blends. Polymer Degradation and... 

R. L. Magovern, Current polyolefin manufacturing processes, Polym. Plastics Technol. Eng. 

The processability of polyolefins can be improved by the irradiation in the presence of crosslinker, for example TAIC [53]. Many other polymers can form elficiently increased amounts of insoluble fraction in the presence of various functional crosslinkers ethylene-vinyl alcohol copolymer with TAIC, DEGDA, NPGDA and TMPTA [54] at maximum 65 % gel fraction at 200 kGy,... 

Liquid etchants can be used for chenucal modification or dissolving surface contamination. Etchants effectively treat irregularly shaped objects that are difficult to treat by other adhesion-promoting processes such as corona or flame treatment. A number of etching solutions and procedures have been developed for specific polymeric surfaces. The choice of the liquid etchant depends on the polymers. Polyolefins are usually treated by oxidizing acids such as chromic, sulfuric, nitric, or mixtures of these. Fluorocarbons are usually treated by sodium-napthalene etching solution. 

Blends of primary anti-oxidants and a high-temperature hydrolytically stable organophosphite secondary anti-oxidant have been developed for high-temperature processing of polyolefins, polyamides, and polycarbonates in colour-critical applications. Irganox LM blends of primary anti-oxidants and a new phosphite processing stabilizer offer melting at 90°C and can be applied to polymer reactor products, especially polyolefins, linear polyesters, polycarbonates, polyamides, HIPS, ABS, SAN, and elastomers. 

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