Mechanical Properties of Low-Density Polyethylene

Hausnerova et al. [33] studied the rheological properties of carbon fiber-filled low-density polyethylene. These woikers investigated rheological properties of carbon-filled low-density polyethylene melts undergoing parallel superposed steady and oscillatory shear flows. It was also found that the critical angular frequency where the phase angle becomes 90° and storage modulus decreases sharply to zero. This was mainly dependent on the fiber volume fraction. 

---

Reddy, C. S. and Das, C. K. 2006. Thermal and dynamic mechanical properties of low density polyethylene-silica nanocomposites Effect of zinc-ion coating on nanosilica. Polymers and Polymer Composites 14 281-290. 

Paraffin wax has been found to have an influence on the thermal and mechanical properties of low-density polyethylene (LDPE) [39,40]. It crosslinks to improve the mechanical properties of LDPE, short sisal fibres composites [42,43] and PVC. There is complete miscibility of the wax in LDPE at wax concentrations up to 10%, but only partial miscibility at higher wax concentrations. On blending an oxidised paraffin wax with LDPE, small wax concentrations improved the physical properties of the blends [40]. 

Dadfar SMA, Alemzadeh I, Dadfar SMR, Vosoughi M. Studies on the oxygen barrier and mechanical properties of low density polyethylene/organoclay nanocomposite films in the presence of ethylene vinyl acetate copolymer as a new type of compatibihzer. Mater Des 2011 32 1806-1813. 

Dilara, A.P., Briassoulis, D. Standard testing methods fiff mechanical properties of low density polyethylene (LDPE) film used as greenhouse covering materials a critical evaluation. Polym. Degtad. Stab. 17, 549-585 (1998)... 

Xiao et al. [59] carried out a detailed study of the mechanical and rheological properties of low-density polyethylene reinforced by the incorporation of multiwalled carbon nanotubes. It was found that the Young s modulus and tensile strength of the composites can increase by 89% and 56%, respectively, when the nanotube loading reaches 10 wt%. The curving and coiling of multiwalled carbon nanotubes play an important role in the enhancement of the composite modulus. It was also found that the materials experience a fluid-solid transition at the composition of 4.8 wt%, beyond which a continuous multiwalled carbon nanotube network forms throughout the matrix and in turn promotes the reinforconent of the multiwalled carbon nanotubes. 

Dynamic mechanical analysis has also been used to determine the mechanical and thermal properties of low-density polyethylene and ethylene-propylene-diene terpolymer containing jute filler, which had improved flexural and impact properties compared to those of the base polymer [198]. Jeong and coworkers [196] and others [195] investigated the dynamic mechanical properties of a series of polyhexamethyl-ene lerephthalale, poly(l,4-cyclohexylenedimethylene terephthalate), and random copolymers thereof in the amorphous state as a function of temperature and frequency. The effect of copolymer composition on dynamic mechanical properties was examined and the dynamic mechanical properties interpreted in terms of the cooperativity of segmental motions. 

Cao J, Gao X, Shen K (2012) Morphologies and mechanical properties of high-density polyethylene induced by the addition of small amounts of both low- and high-molecular-weight polyolefin under shear stress applied by dynamic packing injection molding. J Macromol Sci Part B 51 2519-2526... 

Fig. 3.18. Effect of UV irradiation on the mechanical and physical properties of low density polyethylene [1920]. (Reproduced with permission from [1920] published by John Wiley Sons, Inc., 1976.)...

Poly(f -caprolactone) (PCL), the most representative member of this polyester family, is obtained by the ring-opening polymerization of e-caprolactone. It is a low-7 (60°C), low-Tg (—60°C) semicrystalline polyester that presents mechanical properties resembling those of low-density polyethylene (Table 2.10). 

Jana RN, Bhunia HP, Nando GB (1997) An investigation into the mechanical properties and curing kinetics of blends of low-density polyethylene and poly(dimethyl-siloxane) rubber. Thermochim Acta 302( 1-2) 1—9... 

PolyBCMO is a light-coloured thermoplastic with a crystalline melting point of 181 °C. Its mechanical properties are close to those of Nylon 6 (impact strength is poorer) as well as to those of low density polyethylene. 

A maleated ester of low density polyethylene, prepared by the reaction of LDPE and dibutyl maleate in solution, was blended with TPS by reactive extrusion. Mechanical properties of the blends were similar to those of the LDPE due to the compatibilization of these dissimilar components [75]. 

Post-irradiation oxidative effects lead to a considerable deterioration of the mechanical properties of polypropylene and of its blends with a low content of polyethylene. The elongation at the breaking point of the polymer falls sharply even at doses of lower than 100 kGy which are used for example during the sterilization of medical instruments. In blends consisting of more than 30% w. of low density polyethylene, the influence of post-irradiation oxidative effects is markedly diminished [151]. 

The range over which the state of orientation can be changed in the film blowing operation and the resulting effects on mechanical properties have been demonstrated by Bates.He investigated the effect of both transverse and longitudinal orientation on the impact strength of low density polyethylene. 

Sirin, K. Balcan, M.(2010). Mechanical properties and thermal analysis of low-density polyethylene + polypropylene blends with dialkyl peroxide. Polymer Advanced Technology, vol.21, pp.250-255, ISSN 1099-1581. 

Zhang, M. Q., Rong, M. Z., Zhang, H. B., and Friedrich, K. 2003. Mechanical properties of low nano-silica filled high density polyethylene composites. 

In the absence of light, most polymers are stable for very long periods at ambient temperatures. However, above room temperature many polymers start to degrade in an air atmosphere even without the influence of light. For example, a number of polymers show a deterioration of mechanical properties after heating for some days at about 100 °C and even at lower temperatures (e.g., polyethylene, polypropylene, poly(oxy methylene), and poly(ethylene sulfide)). Measurements have shown that the oxidation at 140 °C of low-density polyethylene increases exponentially after an induction period of 2 h. It was concluded that thermal oxidation, like photooxidation, is caused by autoxidation, the difference merely being that the radical formation from the hydroperoxide is now activated by heat. The primary reaction can be a direct reaction with oxygen (Van Krevelen and Nijenhuis 2009) ... 

This results in deterioration of the mechanical and electrical properties of the polymer resistance to photooxidation by ultraviolet light varies. The following groups of plastics show decreasing light stability in the order of low-density polyethylene > high-density polyethylene > polypropylene > polystyrene. 

The results obtained in the field of thermoplastic starch in combination with polymers or copolymers of vinyl alcohol with aliphatic polyesters and copolyesters in terms of biodegradation kinetics, mechanical properties and reduced sensitivity to humidity make these materials ready for a real industrial development starting from film and foam applications. The present global market is around 12000 tons/year. Main producers are Novamont with Mater-Bi trade-mark, ENPAC and National Starch. The tensile properties of films made of two Novamont s Mater-Bi grades are reported in Table 3, in comparison to these of low density polyethylene (LDPE). Figs. 6-7 show applications of Mater-Bi starch-based materials now on the market. 

---