How to Identify Sealant Quality

How to Identify Sealant Quality
In-Depth Verification: Test Core Properties Through Simple Procedures (Applicable Before Use/During Application)
This stage further verifies key sealant indicators such as adhesion, elasticity, and cure speed. Basic tools (such as a blade, fingers, and a timer) are required:
1. Test “Initial Adhesion”: Prevent Later Debonding
The core function of a sealant is to bond and seal. Poor initial adhesion can directly lead to debonding.

Instructions:
Take two substrates consistent with the intended application (such as glass, aluminum alloy, or concrete; clean the surfaces of oil and dust beforehand). Apply a 1-2mm thick layer of sealant evenly to each surface. After attaching, secure with clamps (applying moderate pressure to avoid excessive squeeze). Allow to set for 24 hours (refer to the “touch-dry time” specified in the product instructions. Neutral sealants typically dry in 2-4 hours and fully cure in 7 days). Judgment Criteria:
After 24 hours, remove the clamps and gently pull the substrate by hand. If there is no peeling at the interface between the adhesive and the substrate (i.e., the adhesive breaks within itself, rather than detaching from the substrate surface), the adhesion is acceptable. If the adhesive directly detaches from the substrate (“interface debonding”), the product is inferior.
2. Test “Cure Speed ​​and Uniformity”: Determine Formulation Stability
Abnormal cure speed (too fast/too slow) or uneven cure is often caused by excessive volatiles in the 107 adhesive or an imbalance in the curing agent ratio, which can affect the long-term performance of the sealant.

Instructions:
Extrude a 10cm long piece of adhesive onto a smooth glass surface (ambient temperature 23±2°C, humidity 50±5%, simulating a standard curing environment). Record the “touch-free time” (the time it takes for the adhesive surface to show no stickiness when lightly touched with a finger) and the “complete cure time” (the time it takes for the adhesive to be cut open with a blade and no stickiness inside). Judgment Criteria:
Conforms to product specifications (e.g., neutral weathering adhesive requires a surface dry time of ≤4 hours and a full cure time of ≤7 days), and there are no “partially uncured” or “skinning on the surface and sticky inside” signs on the adhesive surface (the latter indicates incomplete stripping of the 107 adhesive, resulting in excessive residual volatiles).
3. Testing “Elasticity and Tensile Properties”: Evaluating the Quality of 107 Adhesive
Elasticity is key to a sealant’s ability to cope with thermal expansion and contraction of the substrate, and its quality is directly dependent on the molecular chain structure of the 107 adhesive (high-quality 107 adhesive has regular molecular chains and exhibits better elasticity after curing).

Instructions:
After the adhesive has fully cured (7 days), cut a 1cm x 1cm x 5cm strip of adhesive (or test the cured adhesive directly on the substrate). Slowly stretch the strip by hand to 1.5-2 times its original length, hold for 5 seconds, and then release. Judgment Criteria:
High-quality adhesive strips should “quickly rebound to their original length” and exhibit no noticeable permanent deformation (e.g., failure to recover after stretching or breakage). If the strip breaks easily when stretched, rebounds slowly, or becomes hard and brittle after curing, this indicates poor quality 107 adhesive (possibly due to the use of hydrolyzed materials in place of DMC, resulting in incomplete molecular chains).
4. Smell: Determine if it’s “acidic adhesive masquerading as neutral adhesive”
Silicone sealants are classified as either “acidic” or “neutral.” Acidic adhesives contain acetic acid and release a pungent odor (like vinegar) during curing, which is corrosive to metal and stone. Neutral adhesives (e.g., ketoxime and alcohol types) have a faint or no odor and are more widely applicable. Some inferior products may use acidic adhesives to impersonate neutral adhesives. Smell can be used to quickly identify the adhesive:

How to: Smell the adhesive directly after opening (keep a distance to avoid inhalation). Judging Criteria:
If there is a strong, pungent vinegar smell and the product is labeled “neutral glue,” it is immediately considered inferior (acidic glue is only suitable for non-corrosive substrates such as glass and has far inferior weather resistance to neutral glue). Neutral glue should have no noticeable odor or only a slight alcohol-like odor (non-irritating).