Non-structural bonding refers to the use of adhesives in applications where the primary purpose is not to bear significant loads or provide rigidity to a structure.
## Understanding Non-Structural Adhesives
According to Sirsikar, non-structural adhesives are specifically defined by their performance characteristics. They typically **provide low shear strength, ranging from 0.5 to 5 MPa**, and exhibit **high elongation**. This combination means they can withstand significant deformation or stretching before failing, but they offer limited resistance to forces that try to slide or shear the bonded surfaces apart.
Due to these properties, non-structural adhesives **are generally not appropriate for heavy structural settings**. Their primary role is often for sealing, cushioning, or holding components in place where strength is a secondary concern.
## Characteristics and Applications
The key characteristics distinguishing non-structural bonding include:
* **Low Strength:** Particularly low shear strength compared to structural adhesives.
* **High Flexibility:** High elongation allows for movement and vibration absorption.
* **Limited Load-Bearing Capacity:** Not designed to carry significant structural loads.
Common examples of non-structural adhesives include **rubber- and silicone-based adhesives**, as mentioned in the provided reference.
Here are some typical applications where non-structural bonding is utilized:
* Sealing joints and gaps (e.g., around windows or in bathrooms)
* Attaching lightweight decorative panels
* Gasketing to prevent leaks
* Mounting mirrors or small fixtures (depending on the specific adhesive and load)
* Applying labels or flexible trims
* Providing cushioning or vibration damping
Unlike structural adhesives used in critical load-bearing joints in aircraft or buildings, non-structural adhesives serve functional purposes like sealing, aesthetics, or light assembly where the bond failure would not compromise the overall integrity or safety of the main structure.
## Non-Structural vs. Structural Bonding
It's helpful to contrast non-structural bonding with its counterpart, structural bonding.
| Feature | Non-Structural Bonding | Structural Bonding |
| :--------------- | :---------------------------------- | :--------------------------------- |
| **Shear Strength** | Low (0.5 - 5 MPa) | High (often > 10 MPa) |
| **Elongation** | High | Generally Lower |
| **Load Capacity**| Very Limited | Significant, Load-Bearing |
| **Typical Adhesives**| Rubber, Silicone, Hot Melts, PVAs | Epoxies, Polyurethanes, Acrylics |
| **Primary Role** | Sealing, Filling, Positioning, Cushioning | Creating strong, rigid joints |
This table highlights the fundamental difference: non-structural bonding prioritizes flexibility and sealing over strength, making it unsuitable for applications requiring the bond to contribute significantly to the load-bearing capacity of the assembly.
