Polyethylene-Influence Aging

Valles-Lluch, A. Contat-Rodrigo, L. Ribes-Greus, A. Differential scanning calorimetry studies on high- and low-density annealed and irradiated polyethylenes influence of aging. J. Appl. Polym. Sci. 2003, 89, 3260-3271. 

Guenachi, K., Hamou, A., Hassini, N., Saiter, J.-M., Marais, S., Bucher, E. Influence of sandwind on the durabihty of polyethylene greenhouse aged under sub-saharian climatic conditions. Mater. Res. Innov. 6, 174—178 (2002)... 

Lu S., E.J. Buchanan, and J.R Orr. 2002. Analysis of variables influencing the accelerated ageing behaviour of ultra-high molecular weight polyethylene (UHMWPE). 

Shaov, A.Kh., Sarieva, Z.I., Gurdaliev, Kh. Kh. The Research of the Character of the Influence of Phosphinates and Phosphinoxyde on Mechanical Properties of Polyethylene High Density. - Nova Sci. Publ. - Aging of polymers, polymer blends and polymer composites. - New York. - 2002.-Vol. 2.-P. 167-170. 

Fig. 64. Influence of light stabilizers on the variation of the relative lengthening of high-pressure polyethylene film during the process of atmospheric aging. 1) Un-stabilized polyethylene 2) with an addition of 2-hydroxy-4-octyl-oxybenzophenone 3) carbon black + diphenyl-p-phenylenediamine 4) derivative of 4-thiazolidone.

UV radiation and other climatic factors cause a change in the appearance of polyethylene terephthalate. Figure 5.90. Moisture has significant influence here. With increasing aging, the material embrittles, and mechanical properties change. Figure 5.91. 

Influence of relative humidity on photochemical aging of polyethylene film after 72 hours irradiation time ( 11 MJ/m UV radiation) at 40 °C [87]... 

Many other parameters influence performance of slip additives in polyethylene Figure 10.21 shows that when the winding tension of film increases, the coefficient of friction also increases.Aging temperature increases the degradation rate and volatile losses, and thus decreases the amount of active slip agent. 

Lu S, Orr JF, Buchanan FJ. The influence of inert packaging on the shelf ageing of gamma-irradiation sterilised ultra-high molecular weight polyethylene. Biomaterials 2003 January 24(l) 139-45. 

The influence of the sample shape, structure and molecular weight of the stabilizer on its volatility has received much attention. The rate of evaporation of stabilizer from rubber and polyethylene, for example, was found to be inversely proportional to the thickness of the sample and directly proportional to its surface area. Furthermore, an increase in molecular weight results in an increase in intermolecular dispersion forces which brings about a decrease in volatility of the stabilizer in polymers. Below are two examples which illustrate the effect of some of these factors on volatility of antioxidants from polymers during thermal ageing experiments. 

For a given polymer type, e.g. polyethylene, TGA can show how thermal history (e.g. heat ageing) can affect the oxidative stability of the material, as well as the effect of additives such as antioxidants (both types and levels), and the influence that manufacturing impurities such as residual metal catalysts can have. High-temperature studies carried out at temperatures such as 600°C can show how fillers and pigments can affect stability [25, 26]. 

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