Analysis of the Cause and Influence of DPUR Test Methods on DPUR Test Results of Varnish
The current test method for the DPUR of varnish involves two standards:HG/T 5065-2016 and GB/T 9780-2013.There are two main problems that often cause disputes over the test results.The first one is that because of the hydrophobic characteristics of the hydrophobic varnish,the"uniformity"of brushing process of the DPUR test in HG/T 5065-2016 is separated from the brushing result,and the difference in understanding of the expression"uniform brushing"in GB/T 9780-2013 cited in HG/T 5065-2016 has led to two brushing methods.This test operation that the brushing process must be uniform and the results do not have to be uniform is called"natural brushing method";the test operation that ensures the process and result of brushing method are uniform is called"deliberate brushing method".Through the experimental design,the three key points in the DPUR test of the hydrophobic varnish were investigated and analyzed:the brushing time,the loss of the experiment solution and the weight gain of the test panels.It was found that the"deliberate brushing method"is actually contrary to the relevant regulations in GB/T 9780-2013,and the"natural brushing method"is the suitable test operation thatmeets the requirements of the standard.The DPUR results of the hydrophobic varnish can be correctly evaluated in accordance with the HG/T 5065-2016 standard by the"natural brushing method".The second problem is that according to HG/T 5065-2016 standard,white coatings are introduced in the DPUR test of varnish.However,there are no specific regulations for these white coatings.Through the experimental design,the three key points of the white coatings used in the DPUR test of the varnish were investigated:the brightness of the white coatings,the application method and the curing time of the white coatings.It is found that the application method has no effect on the DPUR results of varnish;the DPUR results of varnish will degrade until the curing time of white coatings is enough;the brightness of the white coatings has no significant effect on the DPUR results of non-hydrophobic varnish,but it has an obvious impact on the DPUR results of hydrophobic varnish.It is recommended that in the subsequent revision of HG/T 5065,further regulations should be made on white coatings to avoid disputes over DPUR test results of varnish caused by differences in white coatings.
万方数据
维普
