The quality of bag making and heat sealing of composite aluminum foil packaging bags has a significant impact on various aspects such as packaging process, transportation, storage of contents, and product distribution.
1. What should I do if the incomplete heat sealing causes leakage or deterioration of the contents?
Reason:
The poor anti pollution heat sealing performance of the film is mainly due to the inappropriate resin used for the inner sealing layer.
Countermeasures:
Use thin films with good pollution resistance and heat sealing properties.
Generally speaking, LDPE has moderate anti pollution heat sealing performance, EVA has good anti pollution heat sealing performance when the VA content is high, LDPE also has good anti pollution heat sealing performance, while ionic resins and metallocene polymers have excellent anti pollution heat sealing performance.
2. What to do if the seal becomes brittle or brittle?
Reason:
(1) The heat sealing temperature is too high.
(2) Excessive pressure.
(3) The heat sealing time is too long.
(4) The edge of the upper sealer is too sharp or the wrapped polytetrafluoroethylene is damaged.
(5) The silicone rubber at the bottom seal is too hard.
(6) During the compounding and aging process, a portion of the adhesive penetrates into the interior of the film. Due to the penetration effect of the adhesive, the toughness (impact resistance) of the substrate decreases and its brittleness increases.
(7) After cooling and placing, the heat sealing strength of plastic composite packaging bags increases, and there is also a tendency to become brittle. 
Countermeasures:
(1) Select appropriate processing temperature, pressure and heat sealing time according to the heat sealing characteristics of the inner seal material.
(2) Improve the Surface states of the upper heat sealing knife to make the surface of the sealer flat.
(3) Cover well with polytetrafluoroethylene cloth.
(4) Choose a silicone rubber pad with appropriate hardness.
3. What should I do if the bag warps after heat sealing?
Reason:
(1) The thickness of the composite film is inconsistent.
(2) The heat sealing temperature is too high or the heat sealing time is too long.
(3) In the longitudinal heat sealing knife section, the running trajectory of the composite film is uneven.
(4) Insufficient cooling.
(5) Insufficient maturation time.
(6) The surface substrate film has poor heat resistance.
(7) Improper tension matching control of the composite substrate during the composite process leads to residual stress after aging and shaping, especially when the composite film thickness is thin, which is more prone to such failures.
Countermeasures:
(1) Adjust the tension of the floating roller.
(2) Select inner sealing substrate with low-temperature heat sealing properties.
(3) Adjust the heat sealing temperature to a suitable temperature.
(4) Adequate cooling.
(5) Fully ripen.
(6) Re select the surface substrate film.
(7) Adjust the tension of each part of the composite processing equipment to ensure that the shrinkage rates of the two composite substrates are equal as much as possible.
4. What should I do if the outer contour of the heat sealing surface is not clear? (The blade pattern is not clear)
Reason:
(1) Short cooling time.
(2) Poor contact of the cooling plate.
(3) Due to the heating of the silicone pad, the edges melted.
(4) The longitudinal heat sealing force is uneven.
(5) The edges of the heat sealing knife are irregular and blunt.
Countermeasures:
(1) Adjust the cooling time.
(2) Adjust the cooling plate.
(3) Replace or adjust the heat sealing knife.
(4) Prevent edge melting caused by overheating of silicone pads.
5. What to do if the heat sealing strength is poor?
Reason:
(1) The adhesive in the composite film has not yet fully hardened.
(2) Inappropriate heat sealing conditions.
(3) The distance between the heat sealing knife and the cooling knife is too long.
(4) There is a problem with the inner sealing film.
(5) The poor heat sealing performance of ink leads to a decrease in the composite strength of the film at the heat sealing area.
(6) Dust, powder spraying, and other substances adhere to the hot surface.
(7) Low composite strength or excessive decrease in composite strength at the heat seal.
Countermeasures:
(1) By promoting adhesive hardening (aging, curing) through insulation aging, the composite strength and heat resistance of the composite film are improved.
(2) Select the optimal heat sealing conditions (temperature, time, and pressure) based on the composition, structure, and heat sealing state of the composite film, or improve the heat sealing method. Immediately cool down after heat sealing.
(3) Check the shelf life and storage conditions of the heat sealing film. If the heat sealing layer uses old batch number films and films that have undergone heat sealing treatment, special attention should be paid.
(4) Increase the thickness of the heat seal film.
(5) Change the type and grade of the heat sealing film and use an inner sealing film with anti pollution heat sealing properties.
(6) Check if the grade of the adhesive meets the requirements (the leakage of low molecular weight substances in the resin can sometimes affect the composition of the adhesive).
(7) Improve the heat sealing performance of the heat sealing layer (substrate), control the content of the lubricant, and use LLDPE film.
(8) Control the monomer content of MDI in the composite adhesive.
(9) Check the degree of treatment of the hot cover.
(10) Replace the ink (preferably using two liquid ink).
(11) Change the printing pattern of the packaging bag to avoid the heat sealing area where the ink is printed, or change the heat sealing method. (Pay special attention not to print metal ink on the sealing area).