gels

Question 1

gels

Answer 1

semi-rigid systems where the gelling agents forms a 3-d network interpenterated by the dispersing vehicle. Movement of the vehicle is restricted by the network. increasing viscosity and becoming semi-solid. transparent or translucent
formed by flocculation of lyophobic solids or concentrated solution of lyophilic colloids

Question 2

what is the basing format

Answer 2

aqueous but can be hydrocarbon based also xerogels are bases which water has been removed from

Question 3

syneresis

Answer 3

squeezing out of vehicle on storage caused by the contraction of elastic gel network

Question 4

sweling

Answer 4

absorption of liquid by gel with an increase in v

Question 5

imbibition

Answer 5

absorptions of liquid without noticeable increase in volume

Question 6

advantages of gels

Answer 6

Ramaleh

Question 7

disadvantages

Answer 7

specific method, incompatibilities and preservation and sterilisation required for hydrogel

Question 8

what are the classification of gels based on structure

Answer 8

two phase; gel mase contains a network of small discrete network of particles flocculation
single phase; macromolecules uniformly distributed
throughout a liquid. Long flexible molecular chains that are entangled and bound together by primary or secondary valence forces. No apparent boundaries exist between the two

Question 9

what are classification of gels based on contineous phase

Answer 9

hydrogel; aquous phase with natural or synthetic polymer

organeogels; hydrocarbon, veg or animal oil as base

Question 10

what are classification of gels based on reversibility

Answer 10

1- irreversible gel. 3D network of covalent bonds that swell up in presence of water but not dissolve
2- reversible gel; bond weaker VDw