When utilising polyethylene to design and manufacture containers, the following factors need to be taken into account:

• container shape and design
• pressure or mechanical stress development during storage
• changes in the plastic resin with time
• leaching of additives from the polymer
• exposure of the container to UV radiation in addition to the chemical environment
• compounding chemical effects on polyethylene from contents
• physical changes in the polymer during processing, eg, degradation
• storage and environmental temperatures
• type of manufacturing process utilised
• effects of any additional additives incorporated prior to processing, g. pigments, which may be subdivided into:
  • plasticisation or swelling
  • oxidation (chemisorption of oxygen into the polymer chain)
  • transmission through the plastic wall
  • stress-cracking (defined by ASTM D883 as an internal or external crack in a plastic caused by tensile stresses less than its short-time mechanical

The requirements below highlight details of the RotoTank™ water and liquid storage tanks that require special attention during the manufacturing process:

• the quality of all incoming raw materials are controlled, recorded and maintained to demonstrate achievement of the required quality and effective operation of RotoTank™’s quality management system
• adequate records are be kept of routine inspections and tests carried out to ascertain that the quality of all manufactured components are as