[987054win]

What is the difference between amorphous and crystalline polymer physical properties.  This website http://pslc.ws/macrog/crystal.htm tells that the crystallinity makes polymer brittle but amorphous makes polymer tough and they said that fiber have high crystallinity. How can fiber have high crystallinity if the website said that high crystallinity makes it brittle, plss help Thks in advance   

[Corribus]

Brittle---Tough does not correspond to everyday notions of Weak---Strong. "Brittle" means there is no plastic deformation before fracture, whereas "Tough" means the material will stretch rather than break. Basically brittle means the material doesn't stretch considerably when you apply a tensile force. It simply breaks once its maximum force load has been reached. Depending on the application, a brittle but strong material may be desirable over a tough but weak one. For instance, a brittle material will maintain its shape as long as you don't apply too much force to it - if you applied the same force to a tough material, it may not break, but it'd be deformed irreversibly and therefore be useless.  Fabrics, made of fibers, would be an example of the latter - if textiles stretched out of shape with small amount of force applied, clothing would need to be replaced all the time! Rather, textiles and other materials made of fibers (like cables) are strong but brittle - they can take a lot of force without plastic deformation, but exceed their capacity to absorb energy, and they simply tear/break/snap.