Plasticizer effect on network structure and hydrolytic degradation

Abstract

a b s t r a c tThe hydrolytic degradation of fully cured polyester-urethane networks polymerized in the presence of several weight ratios of triacetin was monitored by the residual concentration in elastically active chains obtained from modulus and equilibrium solvent swelling measurements. The presence of triacetin does not change the water uptake but induces a lower rate of degradation. Comparisons were performed with networks in which triacetin was removed before ageing, and with networks in which polyester-urethane was first polymerized and then impregnated by triacetin. Data suggest that the presence of triacetin during polymerization induces the presence of elastically inactive chains such as dangling chains and loops, the hydrolysis of which does not change the elastic properties of the network. This explanation was checked from relaxation measurements by NMR and DMA, and by the analysis of the soluble fraction generated by hydrolysis.

Effect of surface treatment methods on the shear bond strength of auto-polymerized resin to thermoplastic denture base polymer

“…Molecular dissolution of polyamide requires a strong interaction between a solvent and the amide groups, which would lead to the disruption of the inter-amide hydrogen bonding. Concurrently, the methylene sequences loosen as a consequence of polymer swelling 192123. The hydrolytic breakdown of amide bonds in strong acids is problematic since it would lead to relative decrease in molecular weight of the polymer, severe destruction, and loss of surface integrity 2228.…”

“…Reduction of the pH in the polymer inhibits re-polymerization of cleaved amide bond and results in softening of the polymer. It seems that the plasticization of the polymer is accompanied by phase inflation, which facilitates the diffusion of monomer into denture base material, cross-linking with auto-polymerized resin, chain entanglements, and the formation of interpenetrating polymer network (IPN) 1920212225262833. IPN refers to a specific class of polymer mixtures consisting of two or more polymers in a network form when one of the polymers is synthesized or crosslinked in the presence of the others 34.…”

“…Although polyamide is a particularly chemical-resistant material, the presence of amide groups (-NHCO-) makes it prone to absorb water or other solvents and form hydrogen bonds 1920. It is well recognized that the plasticization of polyamide matrix occurs in the presence of small amounts of polar molecules capable of hydrogen bonding 2122. The softening enhances the chain mobility and disrupts the hydrogen bond network of polyamides 151923.…”

Coupling between hydrolysis and mechanical relaxation in an ester‐based polyurethane network

“…Depending on the chemical nature of the elastomer, oxidation or hydrolysis will predominate: for example, polydienes are sensitive to oxidation, [1][2][3] whereas polyester-based elastomers are sensitive to hydrolysis. 4,5 Although some studies explore the consequences of chemical degradation through chain scission on tensile behavior, [6][7][8] there is a marked lack of research on the influence of mechanical stress on chemical degradation and the consequences of chain scission on relaxation behavior.…”

Influence of Various Chemical Surface Treatments, Repair Materials, and Techniques on Transverse Strength of Thermoplastic Nylon Denture Base

“…However, the presence of amide groups (-NHCO-) in a solvent makes polyamide prone to absorb water or other solvents and to form hydrogen bonds [ 20 ]. Traces of polar molecules in solvents cause plasticization of the polyamide matrix [ 21 ]. The plasticization of polyamides disrupts the network of hydrogen bonds which enhances the chain mobility [ 20 ].…”