Important points for heat resistance stability of plastic pigments
1. The heat resistance stability index of pigments in plastic processing is related to the concentration of the pigments: Some pigments have different heat resistance stability at different concentrations, such as pigment violet 23 used for HDPE coloring, less than 0.025% The thermal property is only 200 ℃. If it is greater than 0.1%, it has 260 ℃.
2. The heat resistance index of pigments in plastic processing is related to the degradation of applied plastics: the heat resistance stability index of pigments in a certain application and a certain concentration does not equal to its index in other degradations. For example, Pigment Violet 23 can withstand 260 ℃ / 4 hours in polyester stock solution coloring, but Pigment Violet 23 cannot withstand 220 ℃ high temperature in polystyrene degradation.
3. It is worth noting that while considering the high temperature resistance of the pigment, it is also necessary to consider its heating time. For example, when EVA is highly foamed, it needs to be resistant to 160 ° C for 30 minutes. When nylon 6 and polyester are polymerized, the heating time is 260 ° C for 4 hours. Therefore, pigments can only be selected after careful testing under these conditions of use.
4. The heat resistance index of pigments in plastic processing is related to the concentration of titanium dioxide added.Generally speaking, the heat resistance index will decrease after the addition of titanium dioxide.
5. Another consideration is the thermal stability of the colored resin itself. When the resin is heated, it will change color due to the effect of thermal price reduction, such as yellowing. This will also affect the application of heat resistance indicators of pigments in plastics.
Plastic testing method for plastic pigments
1. Test equipment: single screw extruder L / D = 24 injection molding machine
2. Test raw materials: pigment and plastic degradation (HDPE, PP, PS, etc.)
3. Test concentration: corresponding to titanium dioxide 1%
Pigment concentration: 0.1%, 0.05%, 0.025%, 0.005%
4. Test: The quantitative pigment and plastic mixture can be extruded into uniformity multiple times in single screw extruder according to (3) concentration
Particles. In a certain constant time in the injection molding machine, at a temperature of 200 ℃, 220 ℃, 240 ℃, 260 ℃, 280 ℃, 300 ℃ interval, gradually produce samples and test.