What is Curing?
The curing process in Pressure Sensitive Adhesive (PSA) Tapes is a crucial process after the coating process, which refers to the process of removing residual solvents and air pockets which get entrapped in the jumbo during the coating process. This process is a significant step to ensure that the adhesive formulation should reach its optimum quality level. The curing cycle and duration for tapes can vary depending on the adhesive formulation, application etc. While some PSA Tapes require specific curing, like putting them in heat/curing chambers, or through chemical reactions, and in others it may require time for the adhesive to achieve optimal bonding properties.
Why is a curing room/chamber important for tapes?
The curing room provides a properly controlled environment to achieve the adhesive’s bond strength and properties. In a curing room, parameters such as temperature, humidity and air flow circulation can be controlled which allows the adhesive to undergo the necessary chemical and physical changes by removing the air pockets developed during coating process, and by facilitating evaporation of solvents in the adhesive. The curing process under the controlled environment can be maintained as required depending on the adhesive used, especially in case of solvent based adhesives. If the PSA Tapes doesn’t undergo proper curing process, the end product might have residual solvents and air pockets which could lead to poor adhesion and poor finishing of the tapes.
Curing Study:
To understand the importance of curing process, we have done a detailed curing study with green polyester tape to show the influence of the curing influence on the various properties of tapes.
For conducting the curing process, we have taken two PET Film jumbo rolls with 25 micron adhesive coating, and kept one jumbo roll inside the curing room, and the other jumbo was kept for natural curing in the ambient environment.
The table below shows the curing of the Green Polyester Tape over 15 days.
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OBSERVATIONS:
- It is evident from the natural curing table, that more the air pockets, lesser is the adhesion and higher the residual solvents, adhesion is higher.
- The air pockets causes problems during finishing of the product. The oxygen that is entrapped in the adhesive causes oxidation & deterioration in the PSA tapes.
- The residual solvent doesn’t allow the adhesive to cure and harden and also creates false adhesion readings and gives no masking properties.
Findings:
| Curing Room | Natural Curing |
| Curing time is faster | Curing takes longer time |
| Air pockets are very less | More air pockets are observed |
| Passes temperature test | Temperature test fails at 180° angle removal in heat test. |
| Better finish in the final product |
Some examples of curing:
From this curing study, it can be easily concluded that curing and curing room/chamber is an important factors for PSA Tapes and PSA Tapes manufacturers, and a proper curing cycle for all PSA Tapes should be maintained for getting a quality product.
