2.2.2.2 Effect of Rosin on Shear Strength
Rosin contains a strong polar -OH group, under the action of the initiator, the graft reaction to produce polystyrene graft copolymer, together with the phenolic resin to form an interpenetrating network, greatly increasing the viscosity of the adhesive Sex, get high adhesive adhesive. As the amount of rosin increases, the viscosity-increasing effect becomes more and more significant, so the shear strength also increases. However, if the amount of rosin is too much and the active groups are introduced too much, they will affect each other, weakening the interaction with polystyrene, and decreasing the viscosity-increasing effect, and the shear strength will decrease.
2.2.2.3 Effect of EVA Resin on Shear Strength
The EVA copolymer has a large cohesive force and a small melt surface tension, and has a thermal adhesive force for almost all substances, and is excellent in thermal stability, weather resistance, chemical resistance, and electrical insulation. The hot melt adhesive modified with EVA has excellent adhesiveness, melt fluidity and cold resistance. Therefore, with the increase of the amount of EVA, the flexibility of the adhesive is continuously improved, the adhesive force is increased, and the shear strength is also increased.
4 Conclusion
(1) The thermoplastic phenolic resin and rosin can increase the viscosity of the adhesive and effectively improve the adhesive strength of the hot melt adhesive, wherein the rosin has a significant effect of increasing the viscosity.
(2) EVA can increase the flexibility and melt fluidity of the adhesive. It has a significant effect on the fluidity of the adhesive.
(3) According to the curve obtained from the experimental data, the best formula of adhesive can be found. Its composition is: PS3 parts, 3 parts of phenolic resin, 3 parts of rosin, 3 parts of EVA, 1 part of paraffin, 1 part of plasticizer (dioctyl phthalate), 1 part of initiator (cumyl peroxide), One part (mass part) of the antioxidant (2,6-di-tert-butyl-p-cresol) gave a hot melt adhesive with a flowability of 2.3 cm/min and a maximum shear strength of 8.5 MPa.
Source: 21st Century Fine Chemicals Network
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