How to determine if leather release paper can still be used?

To determine whether leather release paper can still be used, the following aspects can be considered:
VISUAL INSPECTION
Observing color: Normal release paper has a uniform color. If there is obvious discoloration, yellowing, or blackening, it may be due to high temperature, chemical substances, or prolonged storage time, and its performance may have changed. It should be used with caution.
Check the surface: Inspect the release paper surface for any damage, scratches, wrinkles, or foreign object attachment. Damage and scratches may cause defects in leather during the release process, wrinkles can affect the smoothness of the leather surface, and foreign object adhesion may contaminate the leather. If there are many such problems on the surface, it is not recommended to continue using it.
Release performance test
Manual peeling: Take a small piece of release paper and a suitable leather material, stick them together, process them according to normal production processes, and then manually peel the leather from the release paper. Feel the force during peeling. If the peeling force is significantly too large or too small, it indicates that the release performance of the release paper may have changed. Excessive release force can cause damage to the leather surface, while insufficient force may cause premature detachment of the leather during production, affecting production quality.
Observation of residues: After peeling, carefully observe whether there are residues on the surface of the leather and release paper. If there are residues of release paper on the surface of the leather, or residues of leather material on the release paper, it indicates that the release effect of the release paper is poor and may no longer be suitable for continued use.
Physical strength testing
Stretching test: Gently stretch the release paper by hand and observe if it is prone to breakage. If the release paper shows obvious cracks or easily breaks during the stretching process, it indicates a decrease in its tensile strength and may not be able to withstand normal tension during production, making it unsuitable for continued use.
Tear test: Try tearing off a small piece of release paper by hand and feel the difficulty of tearing it. If the release paper is easily torn, it indicates that its tear strength is insufficient, and it may be damaged due to external forces during production, affecting the smooth progress of production.
High temperature resistance performance evaluation
Simulation testing: If there is a high-temperature process in the production process, a small amount of release paper can be taken for simulated high-temperature testing. Place the release paper in an environment at the same temperature as the production process for a period of time, and then observe whether there is any deformation, brittleness, discoloration, or other phenomena. If these problems occur, it indicates that the high temperature resistance of the release paper can no longer meet the production requirements.
Chemical stability assessment
Chemical contact test: Conduct a contact test between release paper and commonly used chemical raw materials in the production process to observe whether a chemical reaction occurs. For example, soak the release paper in a coating or adhesive for a period of time, and then check whether the properties of the release paper have changed, such as whether the release performance has decreased, the paper has become soft or hard, etc. If there is a significant change, it indicates that the chemical stability of the release paper has deteriorated and should not be continued to be used.
If there are strict requirements for the performance of release paper, professional testing equipment and methods can be used for comprehensive testing, such as using electronic tensile testing machines to test physical strength, using differential scanning calorimetry to analyze high temperature resistance, etc., to more accurately determine whether leather release paper can continue to be used.