The effects of the molecular weight of polymer powders, the ethyl alcohol content of the liquids, the type of plasticizer and the polymer powder/liquid ratio on viscoelastic properties during gelation of tissue conditioners were studied with an oscillating rheometer. The results showed that: (i) The gelation time decreased exponentially with increases in molecular weight of the polymer powder and with powder/liquid ratio. There were linear relationships between the log of gelation time, and both the molecular weight of the polymer powder and the powder/liquid ratio. (ii) In general, gelation time decreased exponentially with increases in ethyl alcohol content. However, the relationship between the log of the gelation time and ethyl alcohol content fitted a second-order polynomial. (iii) The type of plasticizer affected gelation time. The order of gelation times was: benzyl benzoate < dibutyl phthalate < butyl phthalyl butyl glycolate. The initial flow of tissue conditioners could be controlled over a wide range by varying the molecular weight of the polymer powders, the ethyl alcohol content, the powder/liquid ratio and the type of plasticizer.
In order to measure the viscoelastic properties of tissue conditioners, a series of stress relaxation tests was carried out using poly ethyl methacrylate polymer powders and liquids composed of butyl phthalyl butyl glycolate/ethyl alcohol mixtures, respectively. The analysis method using the Maxwell model analogy is discussed. The results may be summarized as follows. (i) In this study it was feasible to make the stress relaxation curves for 30 min analogous to the Maxwell model, using a model with a maximum of 5 elements. (ii) The elastic modulus Ei, the coefficient of viscosity eta i, and relaxation time tau i, for each element, and the instantaneous modulus E0, tended to increase with time. These values in the element of the longest relaxation time were most marked in the increase among those in all the elements. Furthermore, in every element the rate of increase of eta i was greater than that of Ei. The method described is considered to be one of the most useful techniques available for the study of the viscoelastic properties of tissue conditioners.
An improved method of extraction of residual monomer from acrylic resin has been described for determination of the concentration of residual monomer by gas chromatography. Four kinds of organic solvent selected according to their physicochemical properties (methanol, N,N-dimethylformamide, ethyl acetate and methyl ethyl ketone) were tested for their capacity to extract residual monomer at varying temperatures and time periods. Extraction with methyl ethyl ketone at 4 degrees C was found to be the most effective. The method is simpler and more effective than others reported so far, and therefore seems to be suitable for clinical laboratory use.
The effect of both the ethyl alcohol content of liquids and the type of plasticizer on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The liquids containing the larger percentages of ethyl alcohol produced the larger flow after gelation. Furthermore, the ethyl alcohol content had a significant influence on changes in viscoelastic properties with the passage of time. Flow properties were found to reduce rapidly with time of storage with an increase in the ethyl alcohol content. The use of benzyl benzoate produced the larger flow after gelation than dibutyl phthalate, which in turn produced the larger flow than butyl phthalyl butyl glycolate. The type of plasticizer, however, was found to have no influence on changes in viscoelastic properties with the passage of time.
The effect of the molecular weight of polymer powders and the polymer powder/liquid ratio on the viscoelastic properties after gelation of tissue conditioners was studied by means of a stress relaxation test. The results are summarized as follows. The lower-molecular-weight polymer powders produced the larger flow after gelation especially at long times. The use of a lower powder/liquid ratio produced a greater flow after gelation at both short times and long times. The difference in the molecular weight of polymer powders and the powder/liquid ratio was found to have no influence on changes in viscoelastic properties with the passage of time. It would be possible to control the viscoelastic properties of tissue conditioners suitable for each clinical purpose by making variations in composition and structure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.