Why does the adhesive fail sometimes?
1.Choose the inappropriate adhesive
①The customers just stress shear strength ignoring impact resistance, anti-fatigue and durability. For example, the impact resistance of epoxy adhesive is stronger than epoxy nylon adhesive with good shear strength. However, it can not resist hydrothermal aging property.
③Use 502 adhesive in the sticky environment or other occasions experiencing vibration and shock.
③Use the unsaturated polyester adhesive to bond metals, resulting that the adhesive layer cracks because of shrinkage.
④Use the white latex to bond metals.
⑤The adhesive has poor flexibility and great rigidity. Moreover, the stress focus on one part.
⑥Use the thermoplastic adhesives which is easy to creep.
⑦The polymer molecular weight of adhesive is too low with low intensity.
⑧Use the common epoxy adhesive in the case of alternative temperature.
⑨Plasticizer segregation changes the interfacial properties leading to adhesive failure.
⑩The consistency of adhesive components is poor
⑾The granularity of filler is too large or lacking of drying process.
⑿The viscosity of adhesive is too high and hard to infiltrate with interface failure.
⒀The rate of expansion and shrinkage are too large.
⒁The proportion of poly-component adhesive and the mix ratio are uneven.
⒂The adhesive can not cure completely because of lacking hardener.
⒃Use the out-dated adhesives or ignore the impact of working substance, such as chemistry
2.Choose(or design) inappropriate adhesive joint
①Use the adhesive joint without remedial measures.
②The adhesive joints is too long.
③Ignore the differences between expansion coefficient of different materials.
④The rigidity of substrate is not enough.
⑤The adhesive layer receives the inappropriate tensile force.
⑥Ignore the strength of adhesive joint.
⑦The adhesive layer receives peel force without banding edge and corners on the top.
⑧Use overlapping skill to treat laminating materials.
⑨Use mitre joint on the load-carryingparts.
3.Inappropriate bonding process
①Ignore the surface treatment with interface failure
②The adhesive layer is too thick.
③The hanging time of solvent adhesive is too short after gluing. And the adhesive layer contains solvent after adhesion.
④The adhesive layer loses tack because of short open-time
⑤The exposure time of amine epoxy adhesive is too long before bonding.
⑥The adhesive layers have residual air after adhesion.
⑦The adhesive is hard to infiltrate in low temperature when glued.
⑧The adhesive has malposition under the half curing situation.
⑨There are flaws and cracks around the bonding sections.
⑩Use the adhesive in the humid environment.
(11)Bond the 502 adhesive before hanging.
(12)The thermal curing adhesive may fail with fast heating speed and premature heating.
(13)The pressure is not enough and appropriate in curing time.
(14)The inner stress does not eliminate, when the adhesive cools quickly after thermal curing.
(15)The adhesives do not cure completely. Or the curing time is not enough in low curing temperature.
(16)The residue is not cleaned on the substrates.