These differences mean that the materials react differently with agents from the environment. Therefore, manufacturer must be in a position to appreciating these differences to avoid the production of plastic materials and products with premature failures commonly referred to as nasty and cheap.
The plastic containers adopt the pseudo-elastic design methodology, which involves substitution of appropriate Poisson’s ratio and values of Modulus (that depend on temperature and appropriate time). The substitution involves using elastic standardised strain solutions, which depends on the geometry of the part and the load configuration. The method is appropriate for experimenting and investigating the design failures for polypropylene tanks. Some of the successful approach involve analysing the stress to the 4th order of the linear differentiation (Lewis and Weidmann, 1999a; Lewis and Weidmann, 1999b). The equation takes into consideration the transition between the vertical and the horizontal dimensions as well as the thickness. The manifestations of these transitions are accounted when the wall of the tank increases through radial expansion. The phenomenon can be described as stress concentration.
The method involve assessing the strength parameters based on general values like stability (buckling, kinking), deformation (excessive bends), and strain or stress. Most failed tanks will fail at the welded construction at the joint level. Therefore, the best approach is to adopt a limiting stress criteria, which will aim to provide conservative alternatives to the problem (Lewis and Weidmann, 1999a; Lewis and Weidmann, 1999b).
The design of the tank is very important. The hydrostatic pressure increases linearly and proportionally with the tank’s height. This means that the most appropriate strategy of resisting the pressure is by increasing the tank thickness. The same principle is applicable when constructing the walls