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How to improve the high temperature resistance and aging resistance of composite materials is a very concerned problem for many composite practitioners. According to the different application scope and coloring objects of pigment paste, it is required to have enough light resistance, weather resistance, solvent resistance, migration resistance, as well as satisfactory heat resistance. After a certain period of time, the surface of the material does not have obvious color phase, color light and color force changes, especially in thermosetting composite materials, plastics, rubber, silica gel composite color paste, which should have excellent thermal stability, for example, the color paste used for rubber coloring should have certain thermal stability under the reaction temperature of the vulcanization process; for thermosetting composite materials (saturated polyester Modified epoxy resin, linear phenolic epoxy resin, halogenated epoxy resin, high temperature curing unsaturated polyester resin, vinyl resin, polyamine resin, etc.) do not change the color light under the processing temperature, and have no impact on other physical properties of the finished product. As a food packaging material, it does not decompose in the process of high temperature disinfection.

Due to the different molding temperature of different types of resin, for example, the molding temperature of saturated polyester modified epoxy resin is more than 180 ° 15 minutes, the molding temperature of some linear phenolic epoxy resin is 240 ° C, the molding temperature of unsaturated polyester resin crosslinked by high-temperature curing agent is generally between 160-200 ° 20-45 minutes, and the molding temperature of polyamine resin is mostly more than 240 ° C. Many polyurethane composite materials with closed curing agent have molding temperature even above 280 ℃, polytetrafluoroethylene processing temperature is also above 280 ℃, peek and high temperature POM molding are all above 350 ℃.

The main factors that affect the final color effect of composite materials are as follows:

1. Including the thermal stability of molding resin itself, for example, some resins will change color when heated, such as o-benzene type unsaturated polyester resin, prone to yellowing under high temperature environment, polyether modified epoxy resin, more than 240 degrees will be dispersed and powdered, most acrylic resins are prone to yellowing at high temperature.

2. The by-products, such as hydrogen chloride, in the reaction process of cross-linking auxiliaries will cause the color change of the color paste which is not acid resistant, such as sky blue, group blue, phenol resin, and the reductive by-products produced by the processing of polyamide resin, which will cause the pigment molecules in the color paste to undergo the oxidation of the cycloprotogen reaction of the cryptochromes, resulting in the color light change.

3. The functional auxiliaries are not temperature resistant and decompose during the forming process.

4. Among them, the main influencing factors are the change of the structure of the pigment itself used in the color paste, such as bright red, 2bp of Ciba chemical, f5rk of Klein chemical in Switzerland, which will increase the blue light when heated, and when it absorbs water, it will turn into yellow light red again, while a-crystal phthalocyanine blue will change from red light blue to green blue b-cupc when heated above 220 ℃.

Therefore, it is the key to change the molecular structure of pigment contained in the color paste, improve the temperature resistance of the composite during the molding process and the long-term temperature stability of the finished product in the later use process.

Through cooperation with dye R & D and production enterprises, we have accumulated technical application experience to improve the color effect and high temperature resistance of composite materials.

1、 Change the molecular structure of pigment in the color paste, and increase the relative molecular weight of pigment, such as some conventional pigments, bright red and rose red. The relative molecular weight of 2030 red and sun resistant yellow 94 used has increased from 400-600 to 1000-1500, which not only makes the color more bright, but also improves the light resistance (outdoor sun resistance) and migration resistance. With the increase of molecular weight, the base melting point is significantly improved, from 250 degrees melting point (the finished product starts to change color at 180 degrees) to 315 degrees melting point (the product starts to change color at 240 degrees). At present, Thyssen company is cooperating with the dye enterprise to develop the macromolecular pigment products, with the relative molecular weight of about 2000-4000, with stronger solvent resistance, better migration resistance and color fastness Qualitative overflight.

2、 The introduction of halogenated atoms into the molecules can improve the thermal stability by changing the polarity of the color paste. This scheme has been widely used in the colouring of polyester and polypropylene fibers.

3、 There is a condensed structure in the molecule

4、 The introduction of polar substituent groups, such as cyano and chloro, methoxy, o-chloroacetyl, acetanilide coupling compounds, forms hydrogen bonds in the molecules, increases the coplanarity of pigment molecules in the color paste, and reduces the electronic density of - n = N-group.

5、 In order to improve the overall high temperature resistance, anti dissociation and solve the precipitation problem, the macromolecular dispersant was used instead of the small molecular wetting agent.