Plastics are one of the three major synthetic materials. There are various types of plastics, including polyethylene, polypropylene, polyvinyl chloride, and resins. Different types of wastes have different degradation products. There are many ways to dispose of waste plastics [1â€“4], such as: landfilling, incineration, photodegradation, biodegradation, recycling, pyrolysis, gasoline recovery, styrene monomer recovery, adhesives, coatings, etc. Among the many waste plastics, some waste plastics such as polystyrene (PS) have not yet found a suitable recycling path.
Polystyrene foam (PSF) is widely used in mechanical equipment, instrumentation, household appliances, handicrafts, and other fragile and valuable products due to its light weight, rigidity, high electrical insulation, low moisture absorption, and low price. The shockproof packaging materials, such packaging are all one-time consumption, a great deal of discard. With the development of China's chemical industry and other related industries, the consumption of polystyrene has grown rapidly, especially in recent years. In 1990, the consumption of polystyrene in China was 179,900 tons, and it reached 1,507,300 tons in 1996, which was 8.38 times that in 1990. The average annual growth rate in the six years was as high as 23.84%. With the development of the electronic telecommunications industry, the amount of PSF discarded is increasing day by day. This white trash is lightweight, large in size, large in size, resistant to aging, corrosion-resistant, chemically stable, and not easily degraded and transformed in nature. For a long time, waste polystyrene foam has been treated as much as other plastics by burning and burying it. Exhaust gases from incineration can cause secondary pollution, and landfills can degrade soil quality. Therefore, it is extremely important to explore new methods and obtain considerable economic and social benefits. In recent years, people have explored many ways to use waste polystyrene to prepare coatings, but most of them are physical modifications. Because of the rigidity of polystyrene molecular chains, they are hard and brittle. Therefore, they are prepared by physical modification. Coatings often have the defects of poor coating flexibility and adhesion. Graft modification of polystyrene with modified resin gives the coating a good flexibility, adhesion, and mechanical properties. Now we introduce waste polystyrene as the base material and develop a kind of low cost and excellent performance adhesives and coatings.
1 Experimental section
The waste polystyrene foam is first classified and pre-selected, rinsed with water, dried or dried, and then crushed into small pieces. The clean waste polystyrene foam is added to the mixed solvent of xylene, ethyl acetate and butanol to dissolve. The stirrer is turned on, stirring is continued while adding, until it is completely dissolved, filtered, and then heated to about 70Â° C. Made of plastic mortar, plus emulsifier and modifier, stirring 1-2h, made varnish. Add fillers and pigments to the varnish, mix it evenly at high speed, and finally stop heating and stirring. Disperse and grind to a certain degree of fineness. Add anti-aging agent and filter to get finished product (see Figure 1).
2 Experimental Results and Discussion
2.1 Reagent Selection
2.1.1 Selection of Low-toxicity, Mixed Solvents
The use of waste polystyrene to develop multi-functional coatings, the choice of mixed solvents not only determines the cost of the coating, but also determines the level of its toxicity and performance. It is mainly the choice of solvent. The ideal solvent should have the following characteristics: (1) has a strong dissolving power; (2) is easy to mix with other solvents and has good dispersibility of the filler; (3) the solvent has the least toxicity to facilitate the construction; ( 4) It is cheap and easy to obtain and its volatilization rate is moderate. The strength of the dissolving force can be determined according to the difference between the dissolving parameters of the plastic and the solvent, that is, generally according to the similarity principle of the solubility parameter. The relationship between the miscibility of two substances and the difference of their dissolution parameters in thermodynamics shows that the smaller the difference, the stronger the dissolving power. There are exceptions. Solubility parameters of the solvent and the solute are similar but insoluble. This is due to the large difference in polarity between the solute and the solvent molecule. Under normal circumstances, the polar solute is dissolved in a polar solvent and non-polar. Solutes dissolve in non-polar solvents. Table 1 lists the solubility parameters of some solvents and polymers, and Table 2 lists the technical indicators of several solutions.
The strength of the dissolving power depends on the difficulty of the diffusion of the solvent determined by the affinity between the solvent molecules and the macromolecule polymer molecules into the intermolecular gaps of the macromolecular polymer, usually when the difference in the solubility parameter Î´ value is |Î´1-Î´2| <1 3, it can be estimated that it can be dissolved. From Table 1, it can be seen that although the Î´ value of benzene is similar to that of PS, benzene is not suitable because of its high toxicity and rapid volatilization. Select the mixed solvent by experimentally determining the dissolution time, drying time, gloss, smoothness, and other indicators. Therefore, we used xylene, ethyl acetate and butanol as the mixed solvent for preparing coatings and adhesives.
(to be continued)
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