Detailed Description Of Plastic Pigments
Plastic pigments, industrial articles, refer only to plastics given a variety of colors to make a specific color of plastic products. Plastic pigments should have good color properties, heat resistance and dispersibility. In order to increase the commodity value of plastic products, from the simple pursuit of beauty to the development of the stability, high performance and safety of colored products put forward higher requirements, so plastic colorants should also have a good response in the use of plastic products. Properties such as weatherability, migration resistance, non-toxic and chemical resistance.
Plastic pigments , industrial goods, refers only to plastics given a variety of colors to make a specific color of plastic products. Plastic pigments should have good color properties, heat resistance and dispersibility. In order to increase the commodity value of plastic products, from the simple pursuit of beauty to the development of the stability, high performance and safety of colored products put forward higher requirements, so plastic colorants should also have a good response in the use of plastic products. Properties such as weatherability, migration resistance, non-toxic and chemical resistance.
The basic function of plastic pigment is to give all kinds of colors to plastics. Plastic colorants should be able to withstand various processing conditions in the plastic processing molding process to produce a specific color of plastic products. In today's fierce market competition, product appearance has become an important factor to attract people's attention to the desire to buy, so colorants should have good color performance, heat resistance and easy dispersion. Therefore, plastic colorants should also have good application properties under the use of plastic products, such as weather resistance, migration resistance, non-toxicity, chemical resistance and so on.
1. Coloring power:
1 the importance of coloring power in plastic coloring.
Tinting strength of a pigment refers to the amount required for a certain quantity of colored products, expressed as a percentage of the coloring power of a standard sample. Expression of pigment coloring power: standard depth, 1/3 standard depth, 1/25 standard depth.
2 Determination of tinting strength of pigments in plastics (DIN 53775-8)
(1) Testing equipment two-roll plastic machine roll: 25 RPM / min, speed ratio 1:1.2 roll surface chrome plate press can heat and cool stainless steel mirror panel two pieces, inner frame: square frame, sheet thickness 0.5 mm
(2) test formula: composed of PVC resin, plasticizer, stabilizer and titanium pigment.
(3) control roller surface temperature to 160+5 C degree, PVC slice thickness 0.4mm
Refining time: 7~8MIN tablet pressing at temperature 165~170 press time: after 1 minutes, keep pressure fast and cold.
(4) color measurement standard color value Y calculate K/S value and AVR
Pigment dyeing force test can compare the difference between the two standard samples. When the two have the same dyeing force, the ratio of the difference can be used to determine the dyeing force of the sample.
How to correctly apply the pigment dyeing force index (1) 1/3 standard depth: the pigment dyeing force is not only related to its own chemical structure, but also related to the dispersion of the pigment. The better the dispersity of pigment, the higher the coloring power. Pigment coloring power and color matching are of great importance. For example, the need to match dark colors should choose high coloring power varieties (organic pigments), when the need to match light colors should choose low coloring power varieties (inorganic pigments). When a certain pigment is lacking or expensive in color matching, other pigments of the same color can be used instead, but the two pigments have different coloring power and the amount needed to match the same color when they are replaced.
Two, heat stability:
1 The importance of heat resistance stability in plastics coloring for various types of plastic resins, according to their equipment, process conditions, product requirements, the processing temperature ranges from 120 C to 350 C/5 minutes, such as soft and hard PVC in general at 170 - 200 C, low density and high density polyethylene, polystyrene in 200 - 280 C, polypropylene, polyene The thermal stability of amine, ABS and polycarbonate pigments at 250-330 C means that the pigments have no obvious changes in color, dyeing power and properties at a certain processing temperature and within a certain period of time. The change of pigment in plastic is caused by the following factors
(1) pigments are decomposed by thermal structure, such as azo pigments discoloring due to thermal azo groups.
(2) interaction between additives in pigments and plastic resins.
(3) the pigment is heated and dissolved in the resin.
(4) when the pigment is heated, its physical properties and particle size change. Pigments with excellent heat resistance and stability can prevent pigments from discoloring due to decomposition or crystal change at heating temperature. Heat resistance and stability is an important performance index of pigments used in plastic coloring.
2 Testing methods for thermal stability of pigments for plastics (DIN53772): The testing methods for thermal stability of pigments used in plastics are as follows:
(1) test equipment: single screw extruder L/D= 24 injection molding machine
(2) test materials: pigment and plastic solution (HDPE, PP, PS, etc.)
(3) test concentration: titanium dioxide 1%
Pigment concentrations were 0.1%, 0.05%, 0.025% 0.005%.
(4) Testing: Quantitative pigments and plastic mixtures can be extruded several times in a single screw extruder at (3) concentration to form uniformity.
Particles. In the injection molding machine, according to a certain constant time, with, 200 C, 220 C, 240 C, 260 C, 280 C, 300 C interval temperature, gradually make the sample and test.
(5) Assessment: After the color plate is cooled for 16 hours, the color plate is tested? E=3 is the heat-resistant stability of the concentration. 3 How to correctly apply the heat-resistant stability index of the pigment for plastic coloring because most of the plastic processing technology is thermoforming process, the temperature is above 200 degrees Celsius, and the heat-resistant stability index of the pigment in plastic processing should also be paid attention to. The following points:
(1) The thermal stability index of pigments in plastic processing is related to the use concentration of pigments: some pigments have different thermal stability at different concentrations, such as Pigment Violet 23 used for HDPE coloring, less than 0.025% thermal stability only 200.
(2) The index of heat resistance of pigment in plastic processing is related to the application of plastic degrading: the index of heat stability of pigment in a certain application degrading and a certain concentration is not equal to the index in other degrading, for example, the Pigment Violet 23 in polyester dyeing solution can withstand 260 C/4 hours, but the Pigment Violet 23 in polystyrene solution It is resistant to high temperature at 220 C.
(3) it is worth noting that when considering the high temperature resistance of pigments, the heating time should be taken into account. For example, in high foaming EVA, it needs to be resistant to 160 30 minutes, nylon 6 and polyester polymerization, the heating time is 260 4 hours. Therefore, pigments need careful test before they can be used.
(4) The heat resistance index of pigment in plastic processing is related to the concentration of titanium dioxide. Generally speaking, the heat resistance index will decrease after adding titanium dioxide.
(5) Another consideration is the thermal stability of the colored resin itself. When the resin is heated, it will become discolored, such as yellowing, due to the effect of thermal reduction. This will also affect the heat resistance of pigments in plastics.