How is a heat-transfer film inspected?

With the rapid development of the economy, demand for printed materials is steadily increasing, and expectations for print quality are rising accordingly. The quality of printed products must undergo multiple rounds of testing before they can be released to the market. Certain heat‑transfer films require specialized inspection procedures to meet customer specifications. Let’s take a look at several of these specialized testing methods for heat‑transfer films.

Inspection method: Moderate hot stamping

Depending on the substrate material and its properties, select an appropriate heat‑transfer printer and set the corresponding transfer conditions to perform the hot‑stamping process. During transfer, the pattern is fully transferred; a release liner with moderate peel strength indicates a satisfactory result. This method is suitable for both heat‑peel and cold‑peel applications.

  Test method: heat-transfer color change

Appropriate printing equipment and auxiliary tools should be selected to test the thermal stability of printed products. If no noticeable discoloration is observed on the surface of the transferred product, it is considered compliant.

Test method: Adhesion test

Adhesion is a critical factor affecting the quality of thermal transfer films. It refers to the bonding between the thermal transfer image and the substrate, enabling close interfacial molecular contact and forming a new interfacial layer—adhesion.

Some customers have specific requirements for adhesion and therefore require a tape‑test. Typically, the test involves applying a clear adhesive tape to the transfer surface, then pulling it upward at a 45° or 60° angle (a specified angle), repeating this two to three times; if the tape does not peel off, the product is deemed compliant.

  Test method: Water wash test

Before transfer printing, it is necessary to produce several samples for wash‑testing, with the test criteria determined according to the customer’s requirements. Typically, the workpieces are washed in water at least three times. After washing, the product surface must show no discoloration, fading, pattern shedding, warping, or other defects to be considered compliant.

Test method: Alcohol test

Alcohol tests are generally categorized into two types: the alcohol-soaking test and the alcohol-wiping test. Next, I will briefly introduce each of them.

I. Alcohol Immersion Test

Immerse the hot-stamped product in a 65% alcohol solution for approximately 5 minutes. After the allotted time, remove it. If there is no noticeable color change on the surface of the printed product, or if the color has faded or delamination has occurred, the product is deemed合格; otherwise, it is considered不合格.

II. Alcohol Wiping Test

Dip a coarse cotton cloth or fabric in industrial alcohol, keep it damp, press it against the surface of the printed material, and apply a specified pressure while rubbing back and forth. The pressure and number of rubs should be determined according to the customer’s technical specifications.

Flower films and finished products that fail inspection shall be stored in the scrap or nonconforming‑goods area and clearly labeled for subsequent processing.