Development of Waste Polystyrene Foam Recycled-modified PS Adhesive(2)

2.2 Effect of Different Solvents on Adhesive Properties

PS is a non-polar substance and its adhesion on the surface of the polar material is weak. To make it a better binder, it must be modified. The introduction of polar groups by the addition of modifiers improves their adhesion and must be modified and copolymerized in polar solvents for this purpose. Table 2 shows the main physicochemical parameters of the three organic solvents and the solvency of PS. As can be seen from Table 2, polarity: ethyl acetate> toluene> p-xylene, dissolving power: toluene> ethyl acetate> p-xylene. Considering the toxicity and volatility of the solvent, the PS was modified by choosing a solvent mixture of ethyl acetate and toluene with better dissolution performance.

2.3 Effect of Different Modifiers on Adhesion Properties

Since PS is a non-polar substance, to make it a multi-effect adhesive, polar substances must be added for modification. Obviously, the performance of the modified PS adhesive obtained by adding different modifiers for modification is also different. The results are shown in Table 3.

As can be seen from Table 3, Adhesive III obtained by modifying PS plastic with rosin-modified phenolic resin and petroleum resin has the best adhesion to wood, and has the best hardness and toughness. The reason is that the rosin-modified phenolic resin has strongly polar -OH and -CH2OH groups, so that the adhesive and the adherend mutually form a strong intermolecular force and chemical bond, so that the adhesive is cured on the surface after the adhesive Chemical or physical action produces an organic long-chain molecular layer that has a strong adhesion to adherends. At the same time, the petroleum resin contains -C=C- and its chain segments contain styrene, methyl styrene, fluorene and other groups, which crosslink with rosin modified phenolic resin to form an interpenetrating network, so that the performance of PS adhesive It has been greatly improved.

Adhesives made using pure petroleum resin as a modifier do not have the same adhesive effect on wood as Adhesive III. This is due to the fact that only the -C=C- and styrene, methyl styrene, and fluorene groups [2] are present in petroleum resins, and that there are no strongly polar -OH, -CH2OH, etc. groups, and adhesives and adherends cannot be used. Cross-linked to form a long-chain molecular layer. Adhesives obtained by simply using rosin modified phenolic resin as the modifier II have good adhesive effect to the wood board, but the adhesive layer is soft and each performance is inferior to the adhesive III. Under the same reaction conditions, adhesives V made of PS modified with SBS resin and rosin-modified phenolic resin and adhesive IV modified with MA and rosin modified phenolic resin are all present. Softer, poor adhesion, and long drying time are disadvantageous to the application. Therefore, the rosin-modified phenolic resin and petroleum resin were selected to modify the PS adhesive.

2.4 Effect of Modifier Dosage on Adhesion Properties

The amount of waste PS added has a great influence on the bonding strength. Since it is a non-polar substance, adding too much amount reduces the adhesion to the polar adherend and affects the effect of other additives, resulting in a decrease in the adhesive strength. Therefore, it is necessary to add an amount of modifier appropriate to the amount of PS to increase its polarity, but it cannot be added too much, otherwise it will not be conducive to the dispersion of the adhesive and affect the adhesion effect. A large number of experiments have proved that in the 30% PS glue, when the rosin-modified phenolic resin is added in an amount of 1.5 to 4.0% (PS glue meter), and the amount of petroleum resin added is 1.7 to 3.3%, the obtained product is bonded. Better performance.

2.5 Effect of Additives on Adhesive Properties

Adding fillers to the adhesive can increase the strength of the bonded joints, increase the surface hardness, reduce the coefficient of linear expansion, reduce the cure shrinkage, increase the viscosity, increase the impact toughness, increase the wear resistance, increase the maximum use temperature, and improve the resistance of the adhesive. Media properties, water resistance and aging resistance. It also reduces the cost of adhesives. In addition, the plasticizer DBP is added to improve the plasticity of the curing system, improve the elasticity and improve the cold resistance, and increase the fluidity of the resin, which is beneficial to the wetting, diffusion and adsorption, thereby improving the adhesive strength of the adhesive.

2.6 Effect of BPO on Adhesion Properties

The reaction conditions and the amount of each substance are the same as those of Adhesive III, but the adhesion performance of the adhesive prepared without addition of BPO is far inferior to that of Adhesive III. The reason for this is that the radicals produced by the thermal decomposition of BPO capture the alpha hydrogen in the polystyrene, and thus produce free radicals of the polymer, forming a recombined C-C bond, thereby improving its adhesive properties.

2.7 Effect of Reaction Temperature and Reaction Time on Adhesion Properties

Experiments have shown that adhesives prepared by reaction at room temperature are poor in adhesive property and the adhesive layer is brittle because BPO does not decompose at normal temperature, that is, no free radicals are generated, and other modifiers may not react with PS and its viscosity is not Obviously improved. If the reaction temperature is too high, the resulting adhesive has poor adhesion and a dark color. As the temperature is high, the degradation reaction of polystyrene is intensified, and the resulting dried adhesive of the adhesive is easily softened and does not cooperate with the adhesive. Experiments show that when the reaction temperature is 70 °C, the product performance is better. In addition, during the experimental process, the adhesive strength of the adhesive increases with the reaction time. When the reaction time is greater than 3 hours, the adhesive strength of the adhesive does not increase significantly, indicating that BPO is basically exhausted after 3 hours, and the reaction is almost complete. So the appropriate reaction time is 3h.

3 Conclusion

The best process conditions of this product are: 100% of 30%PS glue solution, 0.5-1.0g of rosin modified phenolic resin, 0.5-1.2g of petroleum resin, BPO0.2g, DBP2.0g, reaction temperature of 70°C, reaction time of 3 hours . It is mainly used for the bonding of wood, paper, fiber and other products.

Source: 21st Century Fine Chemicals Network