Development of Waste Polystyrene Foam Plastic Recycled Adhesive

3.1.5 Effect of Selection and Dosage of Epoxy Resin on Properties of PS Modified Adhesive

Epoxy resin is often referred to as "all-purpose adhesive" and has good adhesion properties to various metals and most non-metallic materials. It is widely used in aircraft, missiles, automobiles, construction, electronic appliances and wood processing and other industrial sectors. Moreover, the epoxy resin adhesive has the advantages of good process performance, high bonding strength, low shrinkage, excellent resistance to dielectric properties, and good electrical insulation properties. Among the PS adhesive modifiers, there are phenolic resins, rosin resins, phthalic acid esters, etc. No one has yet tried epoxy resins to modify PS. Due to the presence of polar groups in the epoxy resin, it should have a good modification effect on PS. Therefore, I tried to modify PS with epoxy resin. However, the effect of modifying the PS with epoxy alone is not good, the adhesive layer is easy to be peeled off, the adhesive strength is not too large, and the adhesive layer is relatively brittle, which may be due to the fact that both have relatively large rigidity. I added a third modifier in the two, and the success was achieved by using isocyanate. The amount of epoxy resin also has an effect on the properties of the glue. The amount is too small and the strength is not high. However, when the amount is slightly larger, the shear strength is decreased. This may be due to the fact that the PS modified adhesive is a solvent-based adhesive and the epoxy resin cures. After that, some of the solvent still remains in the adhesive layer, which affects the performance of the adhesive. This effect is more pronounced with the increase of the amount of epoxy resin added. Moreover, the cost of adding too much is also very high. The relationship between the amount of epoxy resin and adhesive properties is shown in Table 3

3.1.6 Effect of Reaction Temperature on Shear Strength of PS Modified Adhesive

First, the decomposition of the initiator requires energy, and secondly, the cross-linking reaction of PS also requires energy. Therefore, the warming reaction is more thorough and rapid than the normal temperature reaction, and can increase the strength of the glue, taking into account the lower boiling point of the solvent ethyl acetate. When the temperature exceeds 70°C, a reflow device is required, which will inevitably increase the difficulty of the process. At the same time, at a higher temperature, the reaction is intense and the chance of cross-linking increases, thereby weakening the copolymerization reaction with PS. The effect is not good. Therefore, 70°C was selected as the reaction temperature. When the reaction between toluene diisocyanate and PS is almost complete, the reaction of the remaining epoxy resin does not require too high a temperature, and at the same time, in order to prevent the temperature from being high, the degree of cross-linking increases, and therefore, the reaction is continued at 50° C. However, it cannot be reduced too low. Otherwise, the reaction between TDI and epoxy resin does not proceed smoothly, and the purpose of epoxy resin modification PS cannot be achieved.

3.1.7 Effect of Staged Reaction and Reaction Time on the Strength of PS Modified Glue

Toluene diisocyanate and epoxy resin are used as modifiers to improve the bonding properties of PS, while toluene diisocyanate not only modifies PS but also modifies epoxy resin. The modification of the base material PS is not good enough to achieve the purpose of modification. Therefore, a stepwise feed reaction is used. First, TDI is used to modify the PS. Then, a small amount of TDI is added. Together with the unreacted TDI, the added epoxy resin is modified to make the PS molecular chain and epoxy resin. Molecular chains produce cross-links.

From Fig. 3, the shear strength increases with the increase of reaction time, and after 2.5 h, the shear strength tends to be stable, which indicates that after 2.5 h, the modification reaction is basically depleted with the initiator. carry out.

3.1.8 Effect of Filler on Performance of PS Modified Glue

In order to reduce the volume shrinkage of the adhesive when it cures and to fill the surface of the adhered substrate that is not smooth, and to reduce the cost of the glue solution, some additives may be added to the formulation, and active calcium carbonate, talcum powder, and titanium dioxide may be added. Good, the effect of adding the amount of added material on the performance of the glue is shown in Table 4.

Table 4 filler (activated calcium carbonate) on the strength of the adhesive strength, but will also improve the adhesive properties of the glue, the adhesive can be added about 5% of the filler can be filled too much, the glue viscosity is too large, the actual application The solvent is not easy to evaporate, and the wettability on the surface of the adhesive is poor, which affects the adhesive effect.

3.1.9 Application of PS Modified Solvent Glue

The prepared adhesive can be selectively added with a curing agent according to different purposes during use, and the type and amount of the curing agent can change the curing time of the adhesive. But try not to choose curing agents that cure at high temperatures and cure at room temperature too fast. When gluing, try to coat it thin and wait for the solvent to evaporate before re-bonding. This adhesive can be used as non-structural adhesive bonding metal, used for bonding glass, ceramic products with high strength, can also be used for wood and daily necessities such as plastic bonding.

(to be continued)