(3) Surface Conditions of the Adhered Object

• Surface Roughness: If the surface of the adhered object is too rough, it will be difficult for the adhesive to form a uniform adhesive layer when filling the surface grooves. The adhesive has a relatively large flow resistance on a rough surface, and it is likely to form different thicknesses at the protrusions and depressions. After curing, the surface will appear uneven. For example, the microscopic unevenness of an unpolished metal surface will affect the coating effect of the adhesive.
• Surface Cleanliness: If there are impurities such as oil, dust, and moisture on the surface of the adhered object, it will affect the wetting and adhesion between the adhesive and the surface, causing the adhesive to be unable to spread normally in local areas. This will result in inconsistent adhesive layer thickness or debonding, thus causing an uneven surface. For example, in the bonding of electronic components, if there are impurities such as release agents remaining on the surface of the components, it will seriously affect the curing effect of the silicone adhesive.

(4) Curing Condition Factors

• Uneven Temperature: During the curing process, if the ambient temperature is uneven, the curing speeds of different parts of the adhesive layer will be inconsistent. The high - temperature area cures quickly and shrinks rapidly, while the low - temperature area cures slowly and shrinks relatively less. This uneven shrinkage will cause stress on the surface of the adhesive layer, thus leading to an uneven surface. For example, during the local heating and curing process of large - scale equipment, the temperature difference between the parts close to the heat source and those far from the heat source is relatively large, and this situation is likely to occur.
• Too - fast Curing Speed: An overly fast curing speed will cause the molecules inside the adhesive not to have enough time to fully arrange and diffuse before rapidly forming a cross - linked structure. This may cause internal stress in the adhesive layer. Under the action of this stress, the surface of the adhesive layer will deform, resulting in an uneven surface. Especially for some fast - curing silicone adhesives, the control of the curing speed is more stringent.
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