EN 16845-1-2017 pdf download.Photocatalysis – Anti-soiling chemical activity using adsorbed organics under solid/solid conditions – Part 1:Dyes on porous surfaces.
8.1.2 initial set up and calibration
Initially is necessary to setup and calibrate the spraying system to obtain a regular dye spot and to evaluate the dye deposition rate. This consists in the procedure (see 8.2) for the optimization of the experimental setup. It is performed once for the initial setup of the system.
The test procedure consists of two different steps:
a) calibration of the change in the spectral features of the surface (see 8.1.3) of the test sample as a function of the amount of the spread dye. This calibration shall be performed for every test sample (see 8.3).
b) evaluation of the change in the reflectance spectra of the test sample covered be the dye after different times under ultraviolet light (see 8.1.3), This evaluation shall be performed for every test sample (see 8.3.2).
8.1.3 Measurement of the Reflectance Spectra of the Surface
The diffuse reflectance spectra of the sample surfaces shall be measured in the (400-750) nm range excluding the specular component. The reflectance spectra are measured by using a diffuse reflectance standard such as BaSO4 as a reference of 100 % reflectance material. The spectra of each sample shall be the average of at least three spectra acquired in three different places of the sample near the centre of the colour spot on the test piece. The spectra of the sample surface shall be collected before the spraying (pristine surface), along the dye covering on the test sample (calibration function development, see 8.3), after the spraying (time zero condition) and after different irradiation times (itime condition).
8.2 Optimization of the Experimental Setup
8.2.1 General
The calibration of the test apparatus shall be performed once and controlled every 200 samples have been tested. Once optimized the experimental setup is fixed.
8.2.2 Optimization of the Spraying Distance and Flow
It consists in spraying a volume of a chosen dye solution (e.g. methylene blue) under the adopted conditions (tank pressure, gun model) on a white, flat and absorbing substrate (e.g. laboratory filter paper).
The spraying distance and orientation between the gun and the sample shall be changed in a way to obtain a circular spot with a normal (Gaussian) distribution of the amount of dye centred in the spot of the dye on the surface. The spots obtained at different spraying distances, different spraying times and different spraying flows are compared. The optimal spraying distance, flow and optimal spraying time shall be set when a good chromatic contrast between the bare substrate and the spread surface is obtained, and normal distribution of the colour intensity at the surface is obtained. An example is reported in A.2 where the optimum distance is at 25 cm from the gun outlet and a spraying time of 12 s.
8.2.3 Measurement of the Spraying Flow Rate
It consists in measuring for the experimental setup adopted under 8.2.2 the mass of water and acetone sprayed at different spraying times by using an analytical balance with sensitivity s 0,001 g. Three different measurements shall be made:
a) using water from Tank A (see Figure 1), the water is recovered in a vial positioned near as possible to the outlet of the gun to recover all the flow from the gun;
b) using water from Tank A (see Figure 1), the water is recovered in a bottle located in place of the sample at the spraying distance adopted under 8.2.2. The bottle shall have a neck of proper diameter to collect the whole net spray reaching the sample. The bottle neck diameter shall be larger than the spot diameter previously determined (see 8.2.2). A typical value is 1,70 times the full width at half maximum (FWIIM) of the spot colour (±2a) (see 8.2.4). The internal walls of the bottle are covered by laboratory filter paper, and its bottom filled with facial tissue paper, in such a way to completely absorb the water spray entering through the bottle neck.
c) using acetone from Tank B (see Figure 1), the acetone is recovered in a vial positioned near as possible to the outlet of the gun to recover all the flow from the gun. The measurement of the acetone recovered at the spraying distance is discouraged because the easy volatilization.
The net content of the bottle or the vials in each of the above steps a)-c) is measured gravimetrically by an analytical balance. The amount sprayed is measured at least at four different spraying times each lasting one to six seconds.EN 16845-1-2017 pdf download.