Hybrid silane-crosslinking polymers: a potential alternative to polyurethane wood adhesives? A preliminary investigation by TMA
In the last years, the research on wood adhesives has focused on matching technical performance with low health and environmental impacts. This study presents the first development of a new adhesive technology based on hybrid silane-crosslinking polymers that can combine both silicone’s and polyurethane’s adhesive properties. The advantage of hybrid silane-crosslinking polymers is the absence of potential harmful chemicals, such as isocyanates and solvents. Two hybrid formulations were characterized by thermo-mechanical analysis (TMA) and glued wood product elasticity is discussed in this brief original.
On the correlation of some theoretical and experimental parameters in polycondensation cross-linked networks
The use of the equation f = km/αE, correlating number of degrees of freedom m of polymer segments between cross-linking nodes in polycondensation networks to the energy of interaction polymer segment/polymer segment, both within the same polymer and at different polymers interfaces, through measures of deflection in bending by dynamic thermomechanical analysis, yields a number of consequences of interest in the field of polycondensation-hardened networks and of their process of hardening. From this equation, regression equations correlating only two parameters are obtained, which render easier the determination of the parameters that are more difficult or lengthy to obtain by experimental means. The process of networking, hence of the reaction of polycondensation between the gel point and complete hardening of the network, can be followed by the determination of the average number of degrees of freedom m of the polymer segments between cross-linking nodes obtained through these equations. Even the equation of Carrothers can be adapted through the use of the average number of degrees of freedom of polymer segments between cross-linking nodes to describe the course of the polycondensation after the gel point and up to complete stable networking. The dependence from the temperature of m can be connected to both the rate constant of advancement of the network and to the correlation of the value of m of the system to its glass transition temperature. Peculiarities in gel point forecasting by Flory's and Carrothers' theories, which depend on the well-known existence of reactions of cyclization during polycondensation and by a thermodynamic temperature dependence not previously recognized, indicate that the gel point predicted by each theory fails to consider the existence of one and one only of these effects for each theory. On this theoretical basis, the combination of the two theories into a single, simple equation, which can still be used with ease at the applied level, leads to much better precision of forecasting of the gel point than any of the two theories from which the equation is derived and than any of the more complex theories in this field. © 1996 John Wiley & Sons, Inc. J Appl Polym Sci 63: 603–617, 1997
Researches on Structural Factor Involvement in Oral Tribology
This study is focused on two ceramic materials, D.SING (Ivoclar) and VM13 (emphasis the VITA TN), frequently used in restorative dentistry practice and it comes to complete a full set of results obtained by the authors over several years of research on oral tribology with main influence on oral health. In this way there are involved more specific structural aspects of dental restorative ceramic materials quality as is shown in [1].