Vitamin E Stabilized Polyethylenes

In the case of unstabilized PE, concentration in POOH or carbonyl reach a pseudo-plateau after ca 1000 h at which [POOH] is on the order of 10 -10 mol 1 [11]. This relatively high value can be explained. The concentration in created by a 100 kGy irradiation is given by  

Chain scissions are responsible of the partial destruction of crosslink network, and subsequent loss of wear resistance. 

For example, a crosslinking density ca 0.175 mol is obtained for an absorbed 100 kGy dose in the absence of vitamin E. If vitamin E is added prior to irradiation, crosslinked density decreases and plateaus at 

It can be recalled that the irradiation induced crossHnk density is 

In other words, stabilizing UHMAAfPE prior to irradiation is expected to have an adverse effect with the irradiation effect [99]. Vitamin E will be consumed relatively fast during irradiation so that the thermal stability in the post irradiation phase will be low (and even comparable than for unstabilized PE [96]). On the contrary, some promising results on wear 

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The third chapter mainly concentrates on stabilization of irradiated polyethylene by the introduction of antioxidants (vitamin E). The discussion of this chapter has two parts. The first part delineates the main types of antioxidants, stabilization by Vitamin E, structure and biological function of vitamin E, mechanism of stabilization of vitamin E, methods of incorporation of vitamin E, vitamin E stabilized polyethylenes the second part discusses the analysis of the content of vitamin E, using such instruments as FTIR, UV, HPLC and thermal methods. 

Thermally treated materials showed TG patterns similar to those observed for neat and irradiated polyethylene (Figure 2.6). However, the vitamin E-stabilized irradiated UHMWPE exhibited a distinct feature at the beginning of the experiment (Figure 2.7). 

H. Haider, J.N. Weisenburger, S.M. Kurtz, C.M. Rimnac, J. Freedman, D.W. Schroeder, K.L. Garvin. Does Vitamin E-Stabilized Ultrahigh-Molecular-Weight Polyethylene Address Concerns of Cross-Linked Polyethylene in Total Knee Arthroplasty The Journal of Arthroplasty 27(3), 461-469, March (2012). 

The food packaging industry started to commercially develop vitamin E as an antioxidant for polyolefins between the late 1980s and early 1990s [11-14]. During that period, vitamin E was commercialized by Hoffman-LaRoche under the name of Ronotec 2001. It was specifically designed for stabilizing polypropylene, which is much more prone to oxidation than polyethylene [12, 14]. fitamin E was mainly employed as a stabilizer for processing and then added at very low concentrations (lOOppm). 

Stabilization of Irradiated Polyethylene by Introduction of Antioxidants (Vitamin E)... 

L. Costa, I. Carpentieri, P. Bracco. Post electron-beam irradiation oxidation of orthopaedic Ultra-High Molecular Weight Polyethylene (UHMWPE) sta-bihzed with vitamin E. Polymer Degradation and Stability 94(9), 1542-1547, September (2009). 

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