Crosslinking density is the number of network junctions per unit volume of a polymer, or equivalently the molar concentration of elastically effective chains [1]. It is obtained from the equilibrium swelling ratio through the Flory-Rehner relation or from the rubbery plateau modulus through rubber-elasticity theory, and both routes assume affine deformation of the network [1]. The value sets the distance between junctions relative to the contour length of the chain, and with it the modulus, the solvent uptake and the resistance to creep [2]. Junctions formed by covalent bonds, by ionic aggregates or by physical entanglements count differently, so the quantity is defined against the junction type it counts [2]. Probe diffusion through the network slows as the density rises, because the mesh size limits transport [3].
- crosslink density
- flory-rehner equation
- rubber elasticity
- mesh size
- swelling ratio
References
- Walta, S.; Di Lorenzo, F.; Ma, K.; Wiesner, U.; Richtering, W.; Seiffert, S.; Diffusion of rigid nanoparticles in crowded polymer-network hydrogels: dominance of segmental density over crosslinking density. Colloid and Polymer Science 2017, 295, 1371-1381, 10.1007/s00396-017-4069-x.
- Baruel, A.F.; Petroni, S.L.G.; de Mello, S.A.C.; Dutra, J.C.N.; Cassu, S.N.; Processability and Crosslink Density: Role of Peptizers in Natural Rubber and Chlorobutyl Rubber. Journal of Applied Polymer Science 2026, 143, e70703, 10.1002/app.70703.
- Bornstein, D.; Pazur, R.; The sulfur reversion process in natural rubber in terms of crosslink density and crosslink density distribution. Polymer Testing 2020, 88, 106524, 10.1016/j.polymertesting.2020.106524.