Creep is the slow, permanent deformation of a material under a constant mechanical load or stress over an extended period. For repair putties—which are polymeric compounds—creep is a critical failure mode, especially in joints bearing a continuous load (e.g., structural members, pressurized lines, or support components). Over time, a repair that initially held perfectly may slowly bulge, thin out, or shift, leading to a loss of sealing or structural integrity.

Here are genuine solutions focused on reducing the putty’s susceptibility to creep and managing the stresses it encounters.

1. Eliminate or Bypass Continuous Load (Structural Solutions)

The most effective way to prevent creep is to ensure the putty is not the primary load-bearing element in the joint or repair.

• External Mechanical Reinforcement: If the repair is under constant tensile or shear load, the stress must be transferred to the metal substrate.
  • Clamping or Stitching: For cracks, introduce mechanical reinforcement like bolts, metal stitching plates, or internal pins that bridge the defect. The bolts or plates carry the load, and the putty functions only as a seal and filler around the load-bearing elements.
  • Re-Design Load Path: If the repair is part of a bolted flange, ensure the bolts themselves bear the load and maintain the gap, not the cured putty. The putty should be compressed but not subjected to continuous, high-shear stress.
• Wedge-Locking: For a filled cavity, prepare the geometry so the putty is mechanically locked in a way that converts the external load into a compressive force on the putty, rather than a tensile or shear force. Putties are significantly stronger and more creep-resistant under compression.

2. Managing the Cure and Operating Environment

Temperature is a major accelerator of creep. Higher temperatures soften the polymer, making it deform more easily under stress.

• Full Post-Cure Conditioning: Ensure the putty is fully and properly cured, including any recommended post-cure heating cycles. A fully cross-linked polymer matrix resists creep far better than a partially cured one. The process raises the material’s Glass Transition Temperature (Tg​), allowing it to maintain rigidity under load at higher operating temperatures.
• Minimize Operating Temperature: If the load is unavoidable, try to reduce the component’s temperature in the area of the repair. Even a reduction of 10°C can drastically slow the rate of creep. Techniques like heat shielding or improving local airflow can help.
• Avoid High Stress at High Temperature: Never subject the putty to its maximum mechanical load while it is also at its maximum operating temperature, especially immediately after cure. Introduce the load and the heat gradually.

3. Controlling Thickness and Geometry

The shape of the repair influences the stress distribution and, therefore, the susceptibility to creep.

• Thin Bond Lines: Use the minimum effective thickness. Thick sections of polymer are more prone to creep than thin bond lines because the bulk material has less surface area contact with the rigid metal substrate to restrain its movement.
• Maximize Bonding Area: Spread the load over the largest possible area of the rigid metal substrate. By feathering the repair edges and overlapping the defect significantly, you decrease the stress (force per unit area) experienced by the putty, which reduces the impetus for creep.
• Avoid Stress Concentrators: As noted in previous sections, use radii and fillets rather than sharp 90∘ corners in the repair geometry. Stress concentrations accelerate creep by overloading a small portion of the material.