Recently, a customer came to us experiencing problems with patches lifting off of repairs. They were understandably frustrated to encounter this problem.
There are several factors that can affect the bond between the repair material and the tyre. Identifying the cause isn’t always straightforward.
We worked closely with the customer to identify the potential causes and to recommend the improvements that could remedy the problem.
There is more to a sucessful repair than the correct use of the curing equipment.
The tyre and repair area need to be correctly prepared. The repair materials need to be suitable and properly handled. Cement needs to be applied correctly and allowed to dry adequately before the patch is applied. The patch then needs to conform closely to the prepared tyre surface while the correct combination of heat, time and pressure is applied during vulcanisation.
A problem with any one of these stages can affect the finished repair.
Preparation is critical
One of the first things we look at is the condition of the repair surface.
The rubber needs to be clean, dry and correctly prepared, with an appropriate texture for bonding. Dust, moisture, oil, grease or other contaminants can interfere with adhesion. Even apparently minor contamination can have a significant effect once the repair is subjected to pressure, flexing and heat in service.
The preparation itself also matters. Over-buffing, insufficient buffing, excessive heat during preparation or an uneven surface can all contribute to problems later.
The surrounding liner also needs to be prepared correctly so the patch sits properly within the repair area.
The importance of pressure and patch conformity
A patch needs to make intimate contact with the prepared tyre surface during vulcanisation.
This is particularly important on those tyres where the profile makes achieving consistent contact across the whole repair area more challenging.
If parts of the patch aren’t properly supported, air can become trapped beneath it or the edges may not receive sufficient pressure. The result can be localised lifting, voids or, in some cases, a blister developing beneath the repair.
This is one reason we pay close attention not only to the pressure shown on a gauge, but also to whether that pressure is visibly being transferred uniformly across the repair area.
A pressure reading can look correct but incorrect positioning, or selection, of components, folds, wrinkles or uneven loading can result in uneven pressure distribution
Don’t overlook the repair materials
The condition and application of the consumables are another important part of the investigation.
Repair compounds and patches have storage requirements and shelf lives. They also need to be protected from contamination.
Cement is particularly important. Applying more cement doesn’t necessarily produce better adhesion. The correct product needs to be applied appropriately and given sufficient time for the solvents to evaporate before the patch is positioned.
If solvent becomes trapped beneath the repair, it can contribute to gas or pressure formation during heating and potentially compromise the bond.
What can a failed patch tell you?
One of the most useful things when investigating a failed repair is simply looking carefully at how the patch has separated from the tyre.
For example, if the patch comes away relatively cleanly and little rubber remains attached to it, attention should turn towards adhesion, surface preparation and the cement process.
If rubber remains strongly attached to the patch and the tyre rubber itself has torn, the situation may be quite different. The bond may have developed properly and the failure may instead involve the tyre/ repair rubber.
A hollow or blister beneath the patch can point towards trapped air or inadequate consolidation, while lifting concentrated around the edges can indicate problems with pressure, conformity, preparation or the transition at the edge of the repair.
In other words, the failed repair itself can provide valuable evidence about what happened.
It’s rarely just about the equipment
When we investigate a repair problem, we look at the complete process rather than assuming that the equipment is responsible.
That can mean looking at:
- The original tyre and the type and location of the damage
- Surface preparation and buffing
- Cleaning and contamination
- Patch positioning and conformity
- Repair materials and their condition
- Cement application and drying
- Heat and pressure
- The actual vulcanisation cycle
- How the repair was assembled before curing
The technical document we developed for our customer goes into considerably more detail on each of these areas. The important point is that a good repair is the result of the whole process working together.
Support that goes beyond the equipment
At Monaflex we feel strongly that buying a tyre repair system is only the beginning of the relationship.
Our technical team has decades of experience working with tyre repair operations, and we regularly work alongside customers when they encounter a specific repair challenge, introduce new processes or want to improve the performance of their repair operation overall.
Sometimes that means helping to identify a problem with the repair process. Sometimes it means reviewing equipment setup or consumables. And sometimes it is simply sharing experience from another operation facing a similar challenge.
Our aim is always the same: to help our customers produce consistent, reliable repairs and get the maximum possible value from the tyres they are responsible for.
Having the right equipment is just the first step. Operations also need appropriate procedures and processes, a team with comprehensive understanding of the repair process and equipment…and the right technical support when something doesn’t go to plan.