Amorphous vs. Crystalline Polymer 

Polymer crystal are larger than wavelength of visible light so they reflects light and makes semi-crystalline and crystalline polymers opaque.

@@PolymerWorld I think bc Molecular Arrangement In amorphous polymers, the molecular chains are randomly oriented and lack long-range order. This random arrangement allows light to pass through without significant scattering, resulting in transparency. In contrast, semi-crystalline and crystalline polymers have more ordered molecular arrangements due to partial or complete crystallization, which can cause light to scatter, reducing transparency.

@@khangletrong2426 yes. you are correct.

You can consult Polymer Science and Technology by Robert O. Ebewele. It doesn't cover complete GATE syllabus but covers many of the GATE topics.

Low viscosity polymers show high flow rate and in general amorphous polymers have low viscosity.

When we talk about viscosity we need to know if we are talking about solid or melt or solution viscosity because different factors like crystallinity, molecular weight or molecular interaction can influence viscosity. If we are talking about solid viscosity then crystalline will have higher viscosity but for other two it will depend upon molecular weight.

@@PolymerWorld Sir, Actually I was asking about plastic melts. Because the flow rate of plastic material is very important during the injection mold process and is depends on viscosity (higher the viscosity is low flow rate and low viscosity has high flow rate) . So my question is how can we know who has high Flow rate amorphous plastic melts or crystalline plastic melts.inshort how can catgorised the plastic melt according to their Flow rates. Because During runner design in injection mold flow rate is very important thing.

As mentioned previously, melt viscosity will depends on the chemical nature and molecular weight rather than crystallinity since there is no crystal in the melt form. Among several ways to optimize the injection molding process, one can be to measure the melt viscosity of the polymers using rheometer or atleast measure their MFI to know the relative viscosity of the material. Another way can be to change the injection pressure and barrel temperature depending upon the flashing of the mold. It is difficult to optimize or decide the injection molding parameters just by comparing their crystallinity or viscosity.

@@PolymerWorld Thanks for your guidance sir.👍👍

Elastic or plastic nature will depends on the level of strain. A amorphous polymer also shows elastic and plastic deformation so it is not only the crystalline or amorphous part that shows elastic or plastic deformation. Please watch our video on polymer viscoelasticity to learn more.

Epoxy resin is a thermoset polymer. All thermosetting polymers are amorphous in nature.

@@PolymerWorld my concern is i have a knife with micarta handle which I may have sprayed wd40 on. Did some research and wd40 dissolves plastics that are amorphous, i also researched that epoxy resin is chemical resistant. Will my micarta be damaged by wd40?

Epoxy products are mostly highly crosslinked so they show very good chemical resistant. As WD40 mostly consist of alkanes which are not strong chemicals, your knife handle most probably just got little cleaned and nothing else.

@@PolymerWorld thanks for that