Question

Can someone answer the the following question on thermodynamics of polymer blends. If you could do an online search that would be very helpful. Studying for a test, thanks!

Application of Polymer Blends 4. g materials are polymer blends For example, the cases of some of your laptops (probably some old laptops) are using polystyrene/polybutadiene blend. Do some search online and explain why engineers would like to blend polybutadiene into polystyrene. 2) Please search online and list at least one more polymer blend and state why the blend can have better property than single polymer in the blend.

Answer 1

1. So lets start with what a blend actually is. A Blend is nothing but a mixture of two of two different polymers. Its better said than done, because most of the time upon mixing up of two different polymers we are bound to a Phase separated mixture. Here, a phase separated mixture implies that, the two phases of the mixture are visibly separated. Similar is the case with Polystyrene and Polybutadiene blend.These two polymers are immiscible, totally. When we mix polystyrene with a small amount of Polybutadiene, the two polymers won't blend and form a homogeneous material. Instead, the Polybutadiene will separate from the polystyrene into tiny spherical blobs. The most important reason for why we blend polybutadiene into polystyrene is that,this immiscible blend has more ability to bend instead of breaking than regular polystyrene. That is, it's tougher and more ductile. Immiscible blends of polystyrene and polybutadiene are sold commercially under the name high-impact polystyrene, or HIPS for short. And that name points to another improve property for this type of blend: impact resistance or strength.

2. Another example of polymer blend apart from the above one is the immiscible blend of  poly(ethylene terephthalate) and poly(vinyl alcohol). We call them PET and PVA, respectively, for short.Now comes the important question that,why do blends have improved properties?? So basically what happens is that when we blend one polymer with a weak property with another polymer stronger in that property,then the resultant polymer blend formed is bound to have an intermediary value of the same property.Therefore, with respect to the weaker polymer, its physical property has improved.Similar is the case with all other blends. The general situation is that, one of the polymer of the blend would be good in a property and the other polymer must weaker in the same property,therefore as a net result there would be an improvement in that property.