A delay in gluing two substrates is a normal event which influences the shear strength of adhesive joints. During adhesive cross-linking process, the adhesive viscosity gradually increases and it's elastic portion (G'=storage modulus) appears. Therefore, it is expected that assembling two substrates at different delay time would provide different shear strength in adhesive joints.
What parameters from adhesive (e.g. G', G" and viscosity) significantly influence to reduce the shear strength of adhesive joint at different assembly time? How much power do these parameters have on shear strength reduction of adhesive joints at different assembly time?
When two adhesive substrates are brought in contact the molecules on the surfaces start entangling. The process of entangling is a rate process i.e. it will try to adhere slowly and the its strength will increase. The increase of shear strength of the joint will increase slowly first and then it will increase quite fast. The entanglement of surface molecules increases the interphase viscosity finally resulting in strong joint after maturity time
b r gupta
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