Coating percent solids assay

The total solid content of the coating, also known as the solid content of the coating, refers to the content of non-volatile components in the coating components. The higher the solid content, the higher the film thickness during coating, which can save a lot of diluent and the number of coating coats, thereby saving the coating expenses and shortening the construction time, which has great economic benefits.

The method for determining the solid content of common solvent-based coatings is the national standard GB1725-89 (79). The required materials are petri dishes, watch glasses, infrared lamps or ovens for drying and balances. The method of determination is as follows: after weighing the paint, put it in an oven at a certain temperature to keep it warm, and weigh it after drying. The ratio of the mass of the residue to the mass of the sample is the solid content, expressed as a percentage, and the following points should be noted:

(1) The flat-bottomed utensils used for weighing must first have a constant weight, without solvents and moisture.

(2) The coating is uniformly leveled and distributed on the bottom of the container, not too much or too little, generally weighs about 2g, and samples with low viscosity about 4g.

(3) The temperature of the infrared lamp is high, the heating rate is fast, the measurement process is short, but the temperature is difficult to control; in the oven method, a lower temperature than that of the infrared lamp can be used, and the specific temperature selection is shown in the table below. It is advisable to use the oven method for easily decomposed products.

(4) After drying at the specified temperature, take it out and cool it at room temperature, dry it hard, and weigh it once; put it in the oven again for half an hour, and when you weigh it again, there is basically no change in the quality before and after (the quality difference is not greater than 0.0lg) ), that is, constant weight.

(5) The temperature distribution in the oven is uniform, and a large number of parallel experiments can be carried out at the same time. If conditions permit, the oven is generally used for heating. In order to improve the accuracy of the oven method, crystallized hydroquinone can be added to the sample to prevent Skinning on the surface of the sample and oxidation of the paint base.

(6) Calculation method: solid content (x) is calculated according to the following formula

The test results take the average value of two parallel experiments, and the relative error of the two parallel experiments is not more than 3%.

In order to reduce the pollution of solvents to the human body and the environment, new coatings with high solid content (>85%) and solvent-free (>95%) are being vigorously developed at home and abroad, which have great application prospects.