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Linear, Branched And Cross-linked Structures In Polymers


As we explained in polymer production processes, polymers has long chained molecular structures. And properties of polymers generally depends on these molecular structures. In here, we explained the molecular structure types of polymers such as; Lineari branched and cross-linked structures.

What Are The Molecular Structures Of Polymers?

Molecular structures in polymer.

Polymers have different structures and because of this, has different properties. These molecular structures are; Linear, branched and cross-linked structures.

  • Linear structure in polymer molecules: In general, linear molecular structures occur in thermoplastics. In this molecular structure, molecules are occured in linear alignments, and there are nearly no cross-linking or branched structure.
  • Branched structure in polymer molecules: Bracnhed structures in polymer molecules occur with replacement of ‘H’ atoms with ‘C’ atoms in linear molecules, and because of this replacement with ‘C’, this ‘C’ makes additional and same chemical reactions with other ‘C’ atoms. Because of this phenomenon in polymer molecules, branched structures occur. Polyethylene is the example of this branched structure.
  • Cross-linked structure in polymer molecules: This structure is the main type of structure that affects the polymer properties. Cross-linking occurs in polymer structures with the same logic with branched structure that explained above. When the branches that created by ‘C’ atoms are linked with each other, as shown in illustration, cross-linked structure occurs.

Thermosets show different levels of cross-linking structures and this affects the properties of thermosets. With the application of heat and light, cross-linking structures increases in thermoset molecular structure. Cross-linked structure makes polymer harder and brittle. Also, when the cross-linking is occured in a polymer, there is no turn back for that material. Because, polymers lose their melting ability with crosss-linking structure. When you heat up cross-linked thermoset, it will not melt, just burns. Curing is the application of heat and light to create much more cross-linked molecular structure in thermosets to be much more harder and stronger. This molecular structure that has very dense cross-linking called as ‘network structure’.

Also elastomers have cross-linked structures, but in a very low level compared with thermosets. Because this low level of cross-linked structure, elastomers has very high ductility and resilience.

These informations can be very good summary to understand molecular structures of polymers. Do not forget to leave your comments and questions about molecular structures of polymers below. Your feedback is very imporant for us.

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