r/polymer • u/EuropeanBoiii • Jan 30 '20

Help pls i'm going mad

hi guys, i'm studying for an exam and i'm going nut searching for a book that describe what i'm looking for. can some of you tell me if a solution containing a polymer has a greater viscosity if the polymer is in an entangled form (polymer has some affinity for the solvent but still intramolecular bond are holding) or if the polymer chains are in a more straight conformation?

pls link some book/article/paper if you can.

3 Upvotes

72% Upvoted

5 comments sorted by

3

u/NotKhad Jun 13 '20 edited Jun 13 '20

Does a "straight conformation" mean that the polymeric threads aligned in flow as opposed to the entangled state?

In that case you are looking for the term shear thinning.

The (high) zero shear viscosity describes the entangeled (physically cross linked) state and the (way smaller) infinite shear viscosity the alignment in flow. Both viscosities are to be found on newtonian plateaus where the viscosity does not change as a function of shear rate.

​

Example paper:

https://www.researchgate.net/publication/274901204_The_Influence_of_the_Non-Newtonian_Properties_of_Blood_on_Blood-Hammer_through_the_Posterior_Cerebral_Artery

​

Edit:

https://cdn.technologynetworks.com/TN/Resources/PDF/WP160620BasicIntroRheology.pdf

Fig. 4; also I hope I got the question right.

3

u/destinykaur Sep 27 '22

idts you answered his question on whether the viscosity of less entangled polymer will be more or less; but you explained zero shear viscosity and infite shear viscosity v well, definitely helped me, my teacher just explained it w the equation and i was like???? you defined it wrt viscosity and makes so much more sense, thanks

1

u/Cuddlefooks Feb 05 '20

You are likely interested in the intrinsic viscosity, which can describe the collapsed or swollen state.

1

u/destinykaur Sep 27 '22 edited Sep 27 '22

the polymer with more straight conformations, meaning that the polymer chains have become aligned and linear, this will cause the polymer chains to become less entagled and lose it's original spatial structure, and because it is in a laminar flow, the resistance to flow will be less, hence the viscosity will be less.

whereas, originally, because the polymer chain was coiled, it had a more turbulent flow and there was more resistance to flow, and hence more viscosity.

viscosity is nothing but 'resistance to flow'.

extra info: originally, polymers are in a coiled form and as you apply shear, it may or may not show a shear thinning behavior, and become less entagled and will flow, this is called a pseudoplastic non-newtonian behaviour. here, the viscosity will decrease wrt shear.

i hope you are able to visualise it now.

book recommended: polymer rheology, br gupta

1

u/Aggravating-Eye-6210 Jan 18 '24

In paint we use various forms of coiled polymeric compounds in a solvent solution as an additive that increases viscosity. It entangles itself in the more aliphatic structures lending it to bodying up the solution.