Recycling by product massive number of types of plastic, they each carry a resin identification code, and must be sorted before they can be recycled. This can be costly; while metals can be sorted using electromagnets, no such 'easy sorting' capability exists for plastics. In addition to this, while labels do not need to be removed from bottles for recycling, lids are often made from a different kind of non-recyclable plastic. To help in identifying the materials in various plastic items, resin identification code numbers 1-6 have been assigned to six common kinds of recyclable plastic resins, with the number 7 indicating any
Petroleum resin Petroleum resin Hydrocarbon resin is a C5/C9 aromatic hydrocarbon used in industrial applications. It has a tackifying effect and is suitable for use in paint, printing ink, adhesives, rubber and other areas where tackiness is required. It is a kind of thermal plasticizing hydrocarbon resin produced by C5, C9 fraction, by-products of petroleum cracking, through pretreatment, polymerization and distillation. It is not a high polymer but a low polymer with the molecular weight between 300-3000. Featured by acid value, easy mutual solubilities, resistant to water, resistant to ethanol and chemicals. It has the chemical stabilizing property to acid and alkaline,