Fracture energy–fracture stress relationship for weak polymer–polymer interfaces

Autoadhesion of Glassy Polymers

“…5 as a solid line, one may estimate the activation energy of autoadhesion (E a a ) using the following relationship: . [7] Taking into consideration that, at t < t rept , s $ X $ D 1/4 , [21] one obtains the same, and, second, that the physical state of the interior bulk regions does not influence the scenario of the development of the molecular events at the interface, until it is in the viscoelastic state. Besides, the values of E d a indicated above are close to the values of E a of the process of alpharelaxation in the near-surface layer (E aÀsurf a ) of PS of 210 to 320 kJ/mol.…”

On the formation of topological entanglements during the contact of glassy polymers

“…First, the kinetics of the development of interface strength (σ) with healing time (t) had the form σ∼ t 1/4 [1-3, 5, 9] that is typical at T> T bulk g [13][14][15][16] when the chain diffusion across polymer-polymer interfaces does certainly occur. Second, logσ and logE (E is the modulus of elasticity of adhesive joint) have been found to scale with 1/ T [6,11,12], which is characteristic of various Arrhenius-like processes of the diffusion nature. Third, the fracture energy (G) developed at the partially healed polystyrene (PS)-PS interfaces [4,6] is significantly larger than the thermodynamic work of autoadhesion (W a 02g, where g is the free surface energy) [14,17] that should be accomplished in order to overcome weak intermolecular van der Waals forces of physical attraction between the molecular groups located on the two contacting PS surfaces, in the absence of interdiffusion across the contact zone.…”

“…In the recent years [1][2][3][4][5][6][7][8][9][10][11][12], the temperature intervals wherein the autoadhesion (bonding of one and the same material) and adhesion (bonding of different materials) between the two contacting samples of glassy polymers occur owing to the interdiffusion of chain segments across the contact zone have been revealed. The validity of this mechanism of interface healing is based on the following observations at healing temperatures (T) below the glass transition temperature of the bulk ( T bulk g ).…”

Surface dynamics of poly(methyl methacrylate) films affected by the concentration of casting solutions

“…Generally speaking, the chains near a thin lm surface have lower entanglement density and greater mobility relative to those in the bulk. 32 Using more direct methods to characterize surface dynamics in polymers, Boiko et al 10,12,[47][48][49][50][51] found that the temperature dependence of surface relaxation rates above the apparent T g,s corresponds to Arrhenius behavior, suggesting that surface mobility can be ascribed to the segmental length scale. The elementary unit involved in segmental motion has been postulated to be the Kuhn segment, 47 typically several nanometers in length and comprising about 8À10 monomers.…”