Polypropylene fatigue

The first work reported in this area was an investigation of isotactic polypropylene which was fatigued at a rate of 10 hz with an elongation of one to five percent. The spectra showed no shifts in frequency but reversible intensity changes were observed. The data were interpreted in terms of the presence of a smectic-like structure as a result of the cyclic stress 304i 305>. 

Crazing inhibition by crosslinking explains the better fatigue resistance of thermosets compared with thermoplastics (this is not valid for semicrystalline thermoplastics such as polypropylene or poly (ether ether ketone). 

M.N. Bureau, J. Denault, Fatigue resistance of continuous glass fiber/polypropylene composites consolidation dependence, Composites Science and Technology 64 (2004), pp. 1785-1794. 

Van Den Oever, M Peijs, T. (1998). Continuous-Glass-Fibre-Reinforced Polypropylene Composites II. Influence of Maleic-Anhydride Modified Polypropylene on Fatigue Behaviour. Composites Part A Applied Science and Manufacturing, Vol.29, No.3, pp. 227-239 ISSN 1359-835X... 

Fig. 4.82 Fatigue cycles to failure versus stress in compression - tension mode (Jctai for unreinforced and reinforced polypropylene specimen taken in different removal directions [98Mai].

Fig. 4.113 Fatigue strength in alternating and swell mode of reinforced and filled polypropylene [98Mai].

This effect is explained by Inbrication action between elements of the polymer superstructure. The plasticizing effect was evident with abont 0.1% plasticizer in systems containing cellulose esters, and in mixtures of polypropylene and siloxane." " The most useful result of this effect is a decrease in viscosity,"" an increase in fatigue resistance," an improvement in impact strength," and in the adhesion of films." ... 

Commercial polypropylene is isotactic since atactic polypropylene has poor mechanical properties and isotactic is difficult to synthesize. Polypropylene has similar structure and properties as HOPE, except that it has superior flex-fatigue properties and a higher melting point. Polypropylene is commonly used for nondegradable sutures. Like PE, polypropylene can be melt processed. ... 

J Karger-Kocsis. Microstructural aspects of the fatigue crack growth in polypropylene and its chopped glass fiber reinforced composites. J Polymer Eng 10 97-121, 1991. 

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