Polyester Varnish Research Articles

Molecular mechanics modelling of interfacial energy and flexibility on cellulose

Molecular mechanics modelling is used to calculate the energies of interaction, hence the molecular level energy of adhesion at the interface with crystalline cellulose I of three different photopolymerizable primers and of a polyester varnish at the interface with the primer/cellulose assembly. The energy of interactions for just one of the primers with the statistically most common conformation of amorphous cellulose has also been obtained for comparison. Experimental results of adhesion by a standard peel test and by thermomechanical analysis, in which the effect of viscoelastic energy dissipation by crack tip propagation has been respectively minimized or is not present, hence in which the energy of interfacial interaction is nothing else but the work of adhesion, correlated well with the energies of interaction calculated by molecular mechanics. An equation correlating the energy of interaction at each finish/cellulose interface with the deflection derived by thermomechanical analysis, and with the number of internal bond rotational degrees of freedom as well as the degree of networking of the finish, has been derived and is presented. A relationship between the intrinsic fracture energy Go and the molecular mechanics-derived energy of interaction at the interface equating this to the square of the work of adhesion is obtained and is presented.

Molecular Mechanics/Experimental Methods Applied to Varnish/Primer/Wood Interactions

Molecular mechanics modelling is used to calculate the energies of interaction, hence the molecular level energy of adhesion at the interface with crystalline cellulose I of three different photopolymerisable primers and of a polyester varnish at the interface with the primer/cellulose assembly. The energy of interaction for just one of the primers with the statistically most common conformation of amorphous cellulose has also been obtained for comparison. Experimental results of adhesion by a standard peel test and by thermomechanical analysis, in which the effect of energy dissipation by crack tip propagation has been respectively minimised or is not present, hence in which the energy of interfacial interaction S is nothing else than the work of adhesion, correlated well with the energies of interaction calculated by molecular mechanics. An equation correlating energy of interaction at each finish/cellulose interface with the deflection and flexibility derived by thermomechanical analysis, and with the number of bond rotational degrees of freedom as well as degree of networking of the finish has been derived and is presented. Discussion of the relationship of the effects found with the glass transition temperature of the finish is also presented.

New developments in solventless polyester varnishes

Salient features in the formulation of solventless varnishes are discussed. Results of a laboratory investigation of a number of experimental solventless products are presented. Selected physical properties of solventless and solvent-type varnishes are compared. Particular attention is given to overcoming the low build and embrittlement characteristics while maintaining the high bond strength and excellent insulating properties of solventless varnishes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Condensation polymerization of multifunctional monomers and properties of related polyester resins. I. Polyester varnishes

This article discusses optimum conditions for polycondensation of multifunctional monomers. Reaction variables such as monomer concentration, temperature, and time were studied to optimize reaction conditions. The influence of the nature and concentration of catalysts was also investigated. The optimum reaction conditions consisted of polymerization in an 82% w/w m-cresol solution at 160°C for 2 h, continuous reaction at 200°C for 1.5 h at 230°C for 3.5 h, followed by 40 min under reduced pressure and at 200°C. The catalyst was 1.4 × 10−3 mol % Zn(OAc)2 · 2H2O in dimethyl terephthalate. Polycondensation of ethylene glycol, 1,4-butanediol, pentaerythritol, and trifunctional monomers (glycerin or trimethanolpropane) with dimethyl terephthalate was carried out in m-cresol to produce polyester prepolymers. The synthesized prepolymers were mixed with commercial Desmodur CT-stable (a phenol-blocked polyisocyanate) to form one-component varnishes which were characterized by thermogravimetric analysis. Polyester modified with trimethanolpropane has higher thermal stability than the one modified with glycerin. After being coated onto treated copper wires, the magnetic wires were characterized according to the specification of Japanese Industrial Standards (JIS-C-2358) and were found to be acceptable.

Thermal Endurance of Polyester Enameled Wires Using Twisted Wire Specimens: Statistical Analysis of Final Test Results

Thermal endurance tests to AIEE Standard 57 [1] have been performed in six laboratories each using self-prepared varnished specimens made from a common sample of polyester enameled wire and polyester varnish. The results have been analyzed to test the hypothesis of the departure from linearity of the relationship between the logarithm of life and the inverse of the absolute temperature. A comparison is made between the experimental results at the lowest test temperature and the corresponding extrapolated values based on the experimental results at the higher temperatures. The variation between the results of different laboratories is considered. Comparison is made with previous work [2] undertaken in six laboratories on PVA enameled wire specimens, prepared and impregnated with an oil-modified phenolic varnish by a single laboratory, and with published AIEE results. Comparison is also made with the results of a previous interim statistical analysis, [3] applied to the test results at the three higher temperatures only. The main statistical analysis is performed both for the complete set of results, and for the median results only. The extrapolated thermal lives based on the two methods are shown, with one exception, to differ by less than 6 percent at 20°C below the lowest test temperature. The importance of the median method is that generally not all of the specimens are required to be tested to failure, with a consequent saving of a substantial amount of testing time, particularly at the lowest test temperature.

Thermal Endurance of Polyester Enameled Wires Using Twisted Wire Specimens. Statistical Analysis of Test Results

Thermal endurance tests to AIEE Standard 57 [1] have been performed in six laboratories each using self-prepared varnished specimens made from a common sample of polyester enameled wire and polyester varnish. The results have been analyzed to test the hypothesis of the departure from linearity of the relationship between the logarithm of life and the inverse of the absolute temperature. A comparison is made between the experimental results at the lowest test temperature and the corresponding extrapolated values based on the experimental results at the higher temperatures. The variation between the results of different laboratories is considered. Comparison is made with previous work [2] undertaken in six laboratories on PVA enameled wire specimens, prepared and impregnated with an oil-modified phenolic varnish by a single laboratory, and with published AIEE results. Comparison is also made with the results of a previous interim statistical analysis, [3] applied to the test results at the three higher temperatures only. The main statistical analysis is performed both for the complete set of results, and for the median results only. The extrapolated thermal lives based on the two methods are shown, with one exception, to differ by less than 6 percent at 20°C below the lowest test temperature. The importance of the median method is that generally not all of the specimens are required to be tested to failure, with a consequent saving of a substantial amount of testing time, particularly at the lowest test temperature.