The weathering fastness properties of organic pigments in rizid P. V. C. are important because of the demands of usage for rigid P. V. C.. These properties have been the subject of considerable studies, but most of the work, reported in the literature, lacks unity in their evaluation methods. Authors contemplated to examine the weathering fastness mainly about, so-called, high-grade organic pigments to compare the properties with inorganic pigments. The pigments tested include 29 organic and 11 inorganic pigments. The test pieces, coloured with pigments, were exposed 30° facing south in Takarazuka City, under which condition the test pieces yielded maximum amount of radiation throughout a year. Exposed test pieces, both opaque and transparent shade, were compared with unexposed control pieces, and extent of the colour change was estimated by reference to the grey-Scale for assessing colour change. The test pieces of opaque shade were measured on a Colour Master (V-type). From these data, the results were expressed in NBS unit. This paper reports, the results of exposure test for six months. It is true that six months of out-door exposure is insufficient for the test of materials to be used out-door, but, in our experience, fair parts of colour change of a year occur during three months in summer. Then, authors believe that these data are useful for the selection of pigments used in P. V. C. (1) Perylene reds, quinacridone reds, quinacridone violet, phthalocyanine blue, phthalocyanine green, phthalocyanine black, indanthrone, and carbazole dioxazine violet showed excellent fastness enough comparable to the high-grade inorganic pigments. (2) Uuexpectedly, the fastness of some condensation azo pigments, flavanthrone, anthrayrimidine yellow, and brominated anthanthrone, were not so fast as they are in the paint systems. (3) From the results it can be said that, with regard to the most of pigments were examined, the 500-700 hours' exposure of the 6 kW xenon weather-o-meter (SW-SV-S-S type Shimazu Seisakusho Ltd.) is generally equal to the three months' exposure of out-door test in summer time. As the exception from above mentioned, some azo pigments such as nickel azo yellow are comparatively fast in weather-o-meter test, but they showed remarkable colour change in out-door exposure test.
The curing process of unsaturated polyesters has been investigated chemically or electrically, whilst the changes of physical properties with time during the cure have not been dealt with because of experimental difficulty. Previously, authors reported that it is possible to obtain the complex moduli of attached paint films using a vibrometric technique, and this technique may be considered to be applicable for the aim described above. In this study, the differences in the rate of polymerization and physical properties were determined viscoelastically with polyester films which had been formed under different dnying conditions. The experimental method employed was the same reported in the previous paper, but unsaturated polyesters were coated on to the one side of substrate steel panels. The polyester resin used was prepared from phthalic anhydride, maleic anhydride, diethylene glycol and propylene glycol, the molar ratio of which was 5 : 2 : 2 : 5, and 70 parts of the resin prepared were dissolved in 30 parts of styrene monomer. Methylethylketon peroxide solution (60% dimethylphthalate soln.) and cobalt naphthenate solution (1.2% metal cntent) were used as a radical initiator and an accelerator respectively. The drying schedule employed in this experiment is shown in Table 1. Table 1 Drying schedule of unsaturated polyester coatings Component ratio Sample Drying temp.°C polyester soln.initiator soln.accelerator soln. A 100 1 1 20, 30, 40 B 100 2 2 20, 30, 40 C 100 5 5 20, 30, 40 Imediately after coating, the panels to be tested were mounted on the vibrometric apparatus as illustrated previously, and the progress of polymerization of the coated polyesters was followed by the measurements of natural resonance frequency and band width under forced oscillation. From the result of experiments, it is obtained that the dynamic modulus (E) increases with time, while the loss modulus (É) decrease after reaching its maximum value. The temperature (TÉ) for which loss modulus takes a maximum value has been considered to relate with the glass transition temperature, which rises with the development of crosslinkage in polymer. Since the time (tÉ) required for the arrival of the maximum É may be assumed to be inversely proportional to polymerization rate, we can evaluate the rate of dry by means of the determination of tÉ. In this experiment, the rate of polymerization indicated by the reciprocal of tÉ seemed to be nearly proportional to the amount of the initiator incorporated, though a little discrepancy had been recognized. For the heat treated films at 120°C for 4 hours, in spite of the decrease of E with increasing initiator, the rise of TÉ has been observed. This, the reason for which has not been explained, is assumed to indicate the change of chemical compositions caused by the variation of drying schedule.