The non-volatile matter content of the paint refers to the amount of non-volatile matter contained in the paint, which is generally expressed . Non-volatile matter is one of the important quality control items in coating production. Through the determination of non-volatile matter, the amount of film-forming substances in the paint can be quantitatively determined to ensure the quality of the paint and the stability of the batch. The main measurement methods are gravimetric method and volumetric method, and the gravimetric method is mainly introduced below.
1. Scope and description
The non-volatile content is also called solid content. The test principle of this method is to place a small amount of sample in a pre-dried and accurately weighed container, so that the sample evenly spreads on the bottom of the container, and is dried at a specified temperature. After drying, constant weight and weighing.
2. Instruments and Materials
(1) Glass petri dish, flat-bottomed disc made of tinplate or aluminum, about 75mm in diameter.
(2) The diameter of the glass watch glass is 80 lOOmm.
(3) Put color-changing silica gel or anhydrous calcium chloride in the glass desiccator.
(4) The sense of balance is 0.001g.
(5) Blast constant temperature oven.
(6) The thin glass rod is about 100mm long.
3. Measurement method
(1) Petri dish method is suitable for general coatings.
Bake the dry and clean glass petri dish, tinplate or aluminum pan and glass rod in an oven at (105±2)°C (or other agreed temperature) for 30 minutes. Take it out and put it in a desiccator, and cool to room temperature.
Weigh the disk with the glass rod to an accuracy of 1 mg, then weigh (2±0.2) g of the product under test in the disk with the same accuracy (perchlorethylene paint sample 2 1.5g, acrylic paint and solids containing low Sampling 4 to 5g of 15% paint, or other amounts deemed appropriate by both parties). Make sure the sample is spread evenly across the pan. If the product contains a highly volatile solvent, use the subtraction method to weigh the sample from the bottle with a stopper to the pan, and then heat it slowly on a hot Water Bath until most of the solvent evaporates.
Put the tray containing the glass rod and the sample into an oven preheated to (105±2)°C (or other agreed temperature) and keep for 3h (or other agreed time). After a short period of heating, take out the disc from the oven, stir the sample with a glass rod to break the crust on the surface, and then put the rod and disc back into the oven.
After the specified heating time (or until the sample has constant weight), move the disc and rod into the desiccator, cool to room temperature and weigh , with an accuracy of 1mg. The test measures two samples in parallel.
(2) Surface dish method This method is suitable for high-viscosity coatings such as putty, emulsion and nitro cable varnish that cannot be determined by the Petri dish method.
The volumetric method is suitable for determining the volume of dry coating that can be obtained after a certain volume of liquid coating formed into a film is cured (or dried) under specified conditions—the method of non-volatile volume. The test principle of this method is to firstly measure the weight and volume of the unpainted disc, and then measure the weight and volume of the painted disc after drying at a certain temperature and time. Calculate the volume of the dry film on the disc and the volume of liquid paint that forms the dry film. The ratio of these two volumes is the non-volatile capacity of the coating. The results measured by this method can be used to calculate the area that can be coated when paints, varnishes and related products are applied at a certain dry film thickness.
