Completar frases Origin of plasticsVersión en línea The basics of the production of plastic granules to be used for making plastic objects. por Manuel Jesús García Rodríguez 1 monomers PP PE natural polymerisation petroleum colour join properties refineries Depending on their origin , plastics can be classified in plastics and synthetic plastics . a ) Natural plastics are obtained directly from raw vegetable materials - for example , cellulose or latex , or from animal proteins . An example of a natural plastic is rubber . b ) Synthetic plastics are made from compounds extracted from . The majority of plastics belong to this group . Synthetic plastics are obtained in two stages : 1 ) First , petroleum is transformed in into different substances with molecules called . Examples of monomers are the ethylene ( etileno ) or the propylene ( propileno ) . 2 ) Then , these monomers go through a chemical reaction called , where the monomers with each other until a huge molecule ( macromolecule ) is created . This macromolecule is called polymer or plastic . Examples of polymers are the polyethylene ( polietileno , ) or the polypropylene ( polipropileno , ) During the polymerisation reaction , we can add some additives to obtain plastics with better , and we can also add pigments to give them .
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