In: Mechanical Engineering
why the strength of the polymer will increase if the CRYSTALLINITY level of the structure also rises
Ans --
Polymers are not fully amorphous nor fully crystalline. They are in between these two extremities.
As crystallinity level of the polymer increases, its strength increases.,
As we know, crystallinity of any material indicates the degree of long-range order in structure of material. This is because the crystallinity reduces the degree of freedom for the molecular chains to move & the intermolecular bonding becomes more significant.
Thus polymers having high degree of crystallinity are rigid with high melting points.
For increase in crystallinity, its strength increases as the polymer chains are more regularly aligned .
Attached graph shows effect of crystallinity on strength.
The greater the crystallinity, the greater the strength as compared to the totally amorphous structure of a given average molecular weight.