Influences of the Pre-curing Processes of Two-component Flanging Adhesives on the Deformations of Automobile Hoods
To precisely enhance the manufacturing accuracy of vehicle bodies,the deformation control ability of the Lord acrylic and 3M epoxy resin two-component adhesive on the adhesive joints of automobile hoods in high temperature under different pre-curing process conditions was investigated.The deformations in various regions of automobile hoods and the curing temperatures of adhesives were measured using dedicated inspection fixture for front hoods and differential scanning calorimetry(DSC).Subsequently,the influences of pre-curing processes on the baking deformation of bonded joints were analyzed.The results show that the chain initiation stage of the free radical polymerization reaction is crucial to the speed of room temperature pre-curing for the acrylic two-component adhesive.This free radical polymerization initiation reaction is swift,attaining a shear strength of 3.67 MPa after 1 h of room-temperature pre-curing,fulfilling the deformation control specifications.The rate determining step in the curing reaction of the epoxy two-component adhesive occurs during the esterification phase that follows the ring-opening reaction.This step is influenced by the carboxylic acid structure,leading to a relatively protracted esterification reaction process.To achieve a shear strength of 0.87 MPa,the pre-curing is necessary for 4 h without external heating,along with a poor deformation control.Research indicates that the acrylic two-component adhesive performs better in the deformation control,its superior room-temperature pre-curing capability positions it as an ideal choice for effectively managing the high-temperature baking deformations in the adhesive joints of automotive hoods.
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