Analysis of the most popular factors affecting the

2022-08-08
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Analysis of factors affecting the peculiar smell of flexible plastic packaging materials

the peculiar smell of composite flexible packaging materials is a major quality accident, especially food packaging materials, which have particularly strict requirements on the peculiar smell. Some foods with weak taste, such as milk powder, cheese, biscuits, cookies, cornflakes, etc., and some degreased and low-fat products are more sensitive to the peculiar smell

although the polymer material itself has no peculiar smell, in a series of molding processes, various modifiers, various additional materials and the thermal degradation of the polymer material itself can produce peculiar smell. Therefore, packaging materials produce a wide variety of odors, which are complex and changeable. Odors include sweet, sour, medicinal, burnt, paraffin, petroleum, ink, tar, solvent, etc

causes of peculiar smell

1. Peculiar smell caused by plastic thermal decomposition and oxidation

PVC films that are prone to thermal decomposition are no longer used in food composite flexible packaging materials. The prominent problem is the peculiar smell produced by the thermal decomposition of polyethylene, because polyethylene is widely used in the inner thermal seal of composite flexible packaging, and it is in direct contact with the contents of the packaging. The components of substances that produce odor from polyethylene decomposition can be roughly divided into aliphatic hydrocarbons and aromatic hydrocarbons. LDPE is thermally decomposed into saturated or unsaturated hydrocarbons, among which the compounds produced by short branched chains have the greatest impact on the contents. In addition, when plastic is processed under high temperature and high shear force, after extruding the die, it also has a thermal oxidation reaction with oxygen in the air, and the substances produced will also cause odor

2. Peculiar smell produced by plastic additives

in the process of plastic processing and molding, in order to improve the processability or the performance of products, various additives will be added. Additives with different compositions are the main factors causing the peculiar smell, such as plasticizers, heat stabilizers, antioxidants, anti ultraviolet lines, from product formula design to sample preparation, lubricants, opening agents, antistatic agents, antifogging agents, etc. In addition, functional inorganic additives, such as calcium carbonate, kaolin, talc powder, silicon oxide, etc., will be added, which will bring in a large number of dispersants, coupling agents, etc., while various organic pigment masterbatches, titanium white masterbatches, etc., will produce many volatile substances when heated, and the added colorants can promote the decomposition of polymers, raising the working cylinder. There are not many waste plastic recycling plants in a small section;, Odor will also occur during heat sealing

3. Odor caused by aging of plastics

if all kinds of plastic materials are stored for too long, oxygen, ozone and moisture in the air, especially under the action of ultraviolet light, will cause decomposition and oxidation, so that the aging of polymers will produce odor. In addition, the additives in plastics, like plastics themselves, cause oxidation and odor under the action of oxygen and ultraviolet light

4. Peculiar smell caused by ink, adhesive and residual solvent

among composite flexible packaging materials, the main factor causing peculiar smell comes from the solvent residue of ink and adhesive, especially in dry compounding, solvent residue cannot be avoided. At present, the national standard requires residual solvent ≤ 10mg/m2, and the international general requirement ≤ 5mg/m2. The solvent residue is related to many factors, including process. Diluents are often used in printing products, such as toluene, ethyl ester, butanone, etc. The purpose is to make the ink more dispersive and transferable, and improve the printing effect

however, if the diluent volatilizes incompletely in the production process, the surface layer is dried, and the inner layer is still wet, the rate of solvent volatilization is relatively slow. With the continuous increase of winding, the solvent residue increases and produces peculiar smell. This is related to the reasonable matching of solvents and drying temperature, machine speed, indoor temperature and humidity. The solution is to improve the fast drying of the solvent, slow down the machine speed, increase the drying temperature, and relatively reduce the residue of the solvent. In the dry compounding process, the residual solvent is mainly caused by the drying temperature, machine speed and diluent quality. The development of lightweight plastic parts of China's own brand cars and the green manufacturing technology of cars, the scientific and technological breakthrough of lightweight carbon fiber parts of cars and the utilization of key industrialization technologies! Visit the collaborative cooperation mode and R & D cooperation of material manufacturers, OEMs, components and scientific research institutes, and win-win! During the meeting, the drying temperature is usually divided into three areas: 60 ℃ in zone 1, 60-70 ℃ in zone 2, 70-80 ℃ in zone 3, 21-23 ℃ is appropriate, and the relative humidity is 65%

source: China Food Technology

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