Product Characteristics Of Plastic Colors
1. Coloring power:
1. Importance of colouring power in plastic colouring
Tinting strength of pigments refers to the amount required for a certain quantity of colored products, which is expressed by the percentage of coloring power of standard samples. Coloring power of pigments: standard depth, 1/3 standard depth, 1/25 standard depth.
2. Determination of Pigment Colouring Power in Plastics (DIN 53775-8)
(1) Testing equipment 2-roll plasticizer roll: 25 rpm, speed ratio 1:1.2 roll surface chromium plating plate press can heat and cool two stainless steel mirror panels, inner frame: square frame, 0.5 mm thick sheet.
(2) Testing formula: composed of polyvinyl chloride resin, plasticizer, stabilizer and titanium dioxide pigment
(3) Control the surface temperature of the roller to 160+5 C degree and the thickness of the PVC sheet to 0.4 mm.
Molding time: 7-8 MIN tablet pressing time at 165-170 temperature: 1 minute after holding pressure and rapid cooling
(4) Calculating K/S value and AVR of standard color value Y in color measurement
Pigment dyeing power test can compare the difference of the two dyeing power with its standard sample. When adjusting to the same dyeing power of the two, the dyeing power of the sample can be determined by the ratio of the difference.
3. How to correctly apply pigmentation index (1) 1/3 standard depth: pigmentation is not only related to its chemical structure, but also to the dispersibility of pigments. The better the dispersibility of the pigments, the higher the dyeing power. Pigment dyeing power and color matching are of great significance. For example, when it is necessary to mix dark tones, the varieties with high dyeing power (organic pigments) should be chosen, and the varieties with low dyeing power (inorganic pigments) should be chosen when light tones are needed. When one of the pigments is scarce or the price is expensive, other pigments of the same color can be used to replace them. However, different coloring power of the two pigments requires different amount of color when they are used to match the same tone.
2. Thermal stability:
1. The importance of heat-resistant stability in plastic colouring. For different types of plastic resins, according to their equipment, process conditions and product requirements, the processing temperature varies from 120 ~350 C/5 minutes. For example, soft and hard polyvinyl chloride is generally 170-200 C, low density and high density polyethylene, polystyrene is 200-280 C, while polypropylene, polyolefin, ABS and polycarbonate are resistant to pigments at 250-330 C. Thermal stability refers to the fact that the pigments do not undergo obvious changes in color, dyeing power and properties at a certain processing temperature and a certain period of time. The changes in the heat of pigments in plastics consist of the following factors
(1) Pigments are decomposed by the heating structure, such as azo pigments discolored by the breaking of the heating azo group.
(2) Chemical interaction between additives in pigments and plastics resins
(3) Pigments are dissolved in resins by heat
(4) The physical properties and particle size of the pigments change after heating. The excellent variety of heat-resistant stability of pigments can prevent pigments from discoloring due to decomposition or crystal change at heating temperature. Heat-resistant stability is an important application performance index of pigments for plastic coloring.
2 Test Method for Thermal Stability of Pigments for Plastics (DIN53772): Test Method for Thermal Stability of Pigments Used in Plastics is as follows:
(1) Testing equipment: single screw extruder L/D= 24 injection moulding machine
(2) Test raw materials: decomposition of pigments and plastics (HDPE, PP, PS, etc.)
(3) Test concentration: 1% of titanium dioxide
Pigment concentration was 0.1%, 0.05%, 0.025% and 0.005% respectively.
(4) Testing: Quantitative pigments and plastics mixture can be extruded into uniformity multiple times in single screw extruder according to (3) concentration.
Particles. Templates are gradually manufactured and tested in injection moulding machines at constant intervals of 200, 220, 240, 260, 280 and 300 degrees Celsius.
(5) Assessment: After 16 hours of cooling, test the color plate? E = 3 is the thermal stability of the concentration. 3 How to correctly apply the thermal stability index of pigments in plastic coloring process, because most of the plastic processing process is thermal forming process, temperature is above 200 C. The application of thermal stability index of pigments in plastic processing should also pay attention to the following points:
(1) The thermal stability index of pigments in plastic processing is related to the concentration of pigments used: some pigments have different thermal stability at different concentrations, such as the pigments Violet 23 used in HDPE coloring, the thermal stability of pigments below 0.025% is only 200 (.1%) and 260 (.1%).
(2) The heat resistance index of pigments in plastic processing is related to the application of plastic decomposition: the heat stability index of pigments in a certain application solution and at a certain concentration is not equal to that of other solutions. For example, the dye Violet 23 can resist 260 C/4 hours in the dyeing of polyester raw liquor, but the dye violet 23 can not resist 220 C high temperature in the polystyrene decomposition.
(3) It is noteworthy that while considering the high temperature resistance of the pigments, the heating time of the pigments should also be taken into account. For example, when EVA foams at high temperature for 30 minutes, and when nylon 6 and polyester are polymerized, the heating time is 260 C for 4 hours. Therefore, pigments should be carefully tested before they can be selected under these conditions.
(4) The heat resistance index of pigments 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 coloured resin itself. When the resin is heated, the colour changes, such as yellowing, due to the effect of thermal depreciation. It also affects the heat resistance of pigments used in plastics.