The hardening of modified polyacid composite resins (compomers) and glass-ionomers have been studied using infrared spectroscopy. The acid-base reaction in Ketac-fil, a glass ionomer, was followed by the ratio between the COOH band located around 1715 cm-1 and that corresponding to COO- located around 1570 cm-1. The combination of infrared analysis and band narrowing treatments enable us to propose in the glass-ionomer two maturation steps. First, a very rapid equilibrium acid-base related, and second the cross-linking of polycarboxylate with the metal ions present in the cement. In compomers, a new reaction has been described involving polymerization induced by free radicals besides the two steps associated with the acid-base reaction. Using infrared spectroscopy and band narrowing techniques, it is shown that water is essential to complete the hardening process but no acid-base reaction is produced since the COO- band does not appear. The reaction associated with free radicals could be described as a polymerization of methacrylate monomers together with an aqueous dilution of the filling particles releasing different metal cations that would chelate with the polymer molecules to form a macromolecular structure.
The capabilities of high-porous sintercorundum wheels are shown at the spark-out stage using the non-parametric statistics method, which has advantages compared to parametric evaluations when the conditions of homoscedastic and normalcy distribution are violated. Univariate distributions of frequencies by medians have shown that sparking-out of the high-speed plate provides the most significant decrease of median flatness deviation (up to 1.25-1.3 times), with the spark-out pass j = 6 for the R9М4К8 plate, and j = 8 for the R12F3К10М3 plate. For the R12F3К10М3 plate, the parameter R max is decreased by one categorical magnitude (CM) according to GOST 2789-73, and the parameter R a is decreased within the CM range. For the R9М4К8 plate, the heights R a and R max are characterized by the values 0.05 and 0.32 mcm respectively, and lie in the range of CM. The specified number of spark-out passes is also taken into consideration when the accuracy of the process is assessed.
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