Canning and Fish Packaging Technology

Unit 9 - Plastics for Packaging

9.3.1.Polyvinyl chloride (PVC)
It is hard, fairly brittle material but its properties can be modified by the addition of plasticizers – chemicals which when mixed with the polymer, soften it and render it plastic or flexible. Care is necessary that plasticizes used are compatible with food use and the maximum residual monomer limit is 1 mg/kg due to its carcinogenic nature.
As expected from its polar structure, it has higher water vapour permeability than polyolefins but this is still low enough for many applications. It has high clarity and excellent oil resistance, softens below 100oC (when there (10-20pem)). Highly plasticized PVC is used as a cling film for over wrapping super market trays of fresh produce such as red meat, poultry fresh fruits and vegetable and cheese. As a rigid thermo-formed foil it is used to separate and restrain the movements of biscuits, cakes and trifle portions. PVC bottles are widely used for fruit squash cooing oil, mineral water and sometimes for carbonated drinks (the smaller bottles) PVC is also used for cap sealing on jars and bottles.