How to distinguish and identify the real cause of odor? In the author’s opinion, odor problems caused by solvent residues (including solvent vapors absorbed from the environment during transportation and storage) should be distinguished from additives, low-molecular-weight substances in resins, and odors generated during film processing. After eliminating the cause of the residual solvent, consider finding the cause from the perspective of the substrate. Vacuum packaging bags, tea packaging bags Regarding the peculiar smell of food packaging coils, experience tells us that the odor stimuli that cause the sense of smell are mainly volatile and soluble organic substances. Obviously, PET, PA, PE, PP, cured polyurethane adhesives, and dried inks are macromolecular substances without volatility, so there is no odor problem. As stated in the article “Analysis of Odor of Flexible Packaging Film”: The odor in the composite “film mainly comes from these parts: one is the various additives of the resin itself and its own low molecular substances; the other is the odor produced in the film processing; The peculiar smell in flexible packaging processing; the fourth is the peculiar smell in storage.” There are two steps to eliminate the cause of residual solvent: One is to cut a 0.2 square meter piece of composite material according to the standard residual solvent test method, cut into pieces and preheat. , extract the gas, and inject it into the gas chromatograph to detect the residual solvent; the second is to intercept a piece of composite film as large as possible, make a bag, fill it with air, seal the mouth, heat it in an electric oven for a period of time, and use a gas chromatograph The injection needle extracts a certain amount of air from the bag and injects it into the gas chromatograph for residual solvent detection. [Vacuum bag]