Polyethylene thermal properties

Table 10.2 Effect of molecular weight and density (branching) on some mechanical and thermal properties of polyethylene...

A further approach is used by Bayer with their polyesteramide BAK resins. A film grade, with mechanical and thermal properties similar to those of polyethylene is marketed as BAK 1095. Based on caprolactam, adipic acid and butane diol it may be considered as a nylon 6-co-polyester. An injection moulding grade, BAK 2195, with a higher melting point and faster crystallisation is referred to as a nylon 66-co-polyester and thus presumably based on hexamethylene diamine, adipic acid and butane diol. 

Polymerization reactions. Polymerization of ethylene to polyethylene has been conducted at pilot-plant scales reaching a target of 1500 tons per year. Some reactions, including polymerization and copolymerization of polymers for grafting on textile fibers, have been successfully performed. Similarly, cross-linking of polyethylene to improve thermal properties has also been achieved. 

Each set of experiments was carried out under the same reaction condition except using different comonomers, i.e. p-methylstyrene, o-methylstyrene, m-methylstyrene and styrene, respectively. The compositions of copolymers were determined by H NMR spectra, and the thermal properties (melting point and crystallinity) were obtained by DSC measurements. Overall, all comonomers show no retardation to the catalyst activity. In fact, the significantly higher catalyst activities were observed in all copolymerization reactions (runs 2-5), comparing with that of ethylene homopolymerization (run 1). Within each set (runs 2-5 and 6-9) of comparative experiments, p-methylstyrene consistently shows better incorporation than the rest of comonomers, i.e. o-methylstyrene, m-methylstyrene and styrene. Both catalysts with constrained mono- and di-cyclopentadienyl ligands are very effective to incorporate p-methylstyrene into polyethylene backbone. In runs 2 and 6, more than 80 % of p-methylstyrene were converted to copolymer within one hour under constant (- 45 psi) ethylene pressure. On the other hand, only less than half of styrenes (runs 5 and 9) were incorporated into ethylene copolymers under the same reaction conditions. The significantly... 

Polyethylene is known as one of the typical polymers which crosslink under the influence of ionizing radiation. The radiation-induced crosslinking (the formation of C-C covalent bonds between polymer chains) of polyethylene has long attracted the interest of a large number of research workers, because this polymer has the most simple chemical structure for the fundamental study of radiation effects on polymers, and also because the irradiation with ionizing radiation is a practically important means of modifying the mechanical and thermal properties of polyethylene. 

Keywords polyethylene, modification, thermal properties, diffusion, structure - property relation. 

Recently, much attention has been devoted to modeling polyolefins and copolymers of ethylene and polar monomers. Eor example, polymers with regularly spaced methyl groups on a polyethylene backbone have been synthesized and display very interesting and surprising thermal properties and microstructure [12]. This represents a rational synthesis of branched polyethylene that cannot be achieved by any other means at this time (Scheme 6.12). 

Another benefit of copolyermization of ethylene is incorporation of appropriate polar groups such as carboxylic acid groups or salt groups in the ionomers. Du Pont is still the only producer of the Surlyn-type of polyethylene ionomers. However, several companies produce copolymers of ethylene with acrylic acid (EAA). Such copolymers offer improved thermal properties with retention of clarity, improved heat-seal strength, and impact strength, as well as improved adhesion to a variety of substances, such as aluminum foil, glass fibers, and mineral fibers. 

The sulfonation of polyethylene films to produce negatively charged membranes was described above24. While adequate for many uses, these aliphatic polysulfonates lack long-term stability under adverse conditions. To improve performance, attention was directed in recent years to sulfonation of so-called engineering thermoplastics , a class of film-forming polyaromatics with improved mechanical and thermal properties. 

Polymers are broadly classified as synthetic and natural polymers. Synthetic polymers have become significant since the 1940s and continue to replace glass, wood, constructional materials and metals in many industrial, domestic and environmental applications [2-5]. Synthetic polymers are made from hydrocarbons derived from petroleum. Some of these polymers, such as nylon, polyethylene, polyurethane and so on, are an indispensable part of our daily lives. Due to their stability and durability they offer good mechanical and thermal properties [6], making them suitable for a variety of applications, e.g., in automobiles, cosmetics, medicines, biosensors,... 

When studying UHMWPE blended with low-density polyethylene (LDPE) and linear low-density polyethylene (LLDPE), it was found, using analysis of the log-additive rule, Cole-Cole plots, Han curves, and Van Gurp s plot, that the LDPE/UHMWPE blends were miscible in the melt [8]. However, the thermal properties and morphology of the blends were not consistent with the rheological properties. The latter showed liquid-solid phase separation as a result of the different rates of crystallization of LDPE and UHMWPE. However, the rheological properties and electron microscopy images of LLDPE/UHMWPE blends showed... 

G. Madhu, H. Bhunia, P.K. Bajpai, Blends of high density polyethylene and poly(L-lactic acid) mechanical and thermal properties. Polym. Eng. Sci. (2013). doi 10.1002/pen.23764... 

G. Singh, H. Bhunia, A. Rajor, V. Choudhary, Thermal properties and degradation characteristics of polylactide, linear low density polyethylene, and their blends. Polym. Bull. 66, 939-953 (2011)... 

K.A. Tawab, S.M. Ibrahim, M.M. Magida, The effect of gamma irradiation on mechanical, and thermal properties of recycling polyethylene terephthalate and low density polyethylene (R-PET/LDPE) blend compatibilized by ethylene vinyl acetate (EVA). J. Radioanal. Nucl. Chem. 295, 1313-1319 (2013)... 

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