Nine major precautions for polyurethane potting glue

Polyurethane potting glueWidely usedElectronic components, air filters, automobiles, etc.Field, cured polyurethane potting glueWater-resistant, cold-resistant, high-temperature resistant, can be used for effective filling and sealing. The author is nextI will tell you the following nine major precautions for polyurethane adhesives.

1, polyurethane glue–Appearance treatment

One ​​of the conditions for excellent adhesion is the need to treat the substrateSurface.

Adhered objectSurfaceThere are often weak interface layers such as grease and dust. On the weak interface layerGlue filling will cause The bonding strength is not high, so pair and adhesivegluingSubstrateSurfaceProcessed, surfaceTreatment is important to improve the bonding strengthImportant One ​​of the steps.

2, polyurethane glue–Cleaning and degreasing

The appearance of some metal plastic substrates is often easily contaminated by sweat, oil, dust, etc. In addition, the appearance of plastics also Release agent, so such plastics only form a weak bonding interface with the adhesive layer.

YesPolyurethane potting glue Generally speaking, grease with a metal or plastic appearance has poor compatibility with polyurethane, and the existing moisture will interact with one of the NCO in the adhesive. The group reaction produces air bubbles, which reduces the contact area between the glue and the substrate, andom:7px;margin-left:0;margin-top:auto;margin-bottom:auto;text-indent:37px”>The heating process should gradually increase in temperature. For solvent-based polyurethane adhesives, attention should be paid to the volatilization speed of the solvent. During the drying process, most of the solvent has evaporated, and the remaining solvent slowly diffuses outward through the adhesive layer. If it is heated Soon, the solvent will evaporate and bubble in the softened adhesive layer, forming bubbles at the joint. Most of the uncured adhesive in a viscous state will be squeezed out of the joint due to stretching, and the formation of voids will affect the bonding Strength. For two-component solvent-free adhesives and one-component moisture-curing adhesives, heating should not be too fast, otherwise –NCOGroup and Contact SubstrateSurfaceMoisture in the airoccurrencereaction, producedCarbon dioxide<font face The gas has no time to diffuse, and the viscosity of the adhesive layer increases rapidly, leaving bubbles in the adhesive layer.

One-component moisture-curing polyurethane potting glue is mainly cured by moisture in the air, so it should maintain a certain air humidity and cure slowly at room temperatureis appropriate . If the air is dry, you can sprayApply a small amount of water to promote curing. If the glue is sandwiched between dry and hard adherends, the glue layer will be thicker, and the moisture at the interface and outside will not easily penetrate into the glue, resulting in incomplete curing. In this case, a small amount of water can be added to the glue.