Technological requirements of the hottest moisture

Process requirements of moisture-proof and mould proof polymer composite packaging materials

Abstract: the manufacturing process of moisture-proof and mould proof polymer composite materials is introduced, and its material selection and process requirements are explained

key words: moisture proof and mildew proof packaging materials

0 introduction

moisture proof and mildew proof polymer composites have the characteristics of light and soft, chemical corrosion resistance, good heat sealing performance and so on. It is widely used in the packaging of chemical products, precision machinery, electronic devices, instruments and military products. According to the research and production practice, the moisture-proof and mildew proof performance standards of the packaging materials and their available anywhere; The production process of product structure unit is discussed as follows

1 moisture resistance

1.1 technical performance

chemical products such as gunpowder, explosives, propellants, primary explosives and other materials with strong moisture absorption are very susceptible to moisture deterioration; Electronic instruments and core boards, precision machinery, instruments and meters are prone to rust or mold erosion when affected with moisture. The basic requirements of moisture-proof packaging shall be in accordance with gb5048, and the moisture-proof technical indicators specified in the national standard gjb1444-92 or gjb2605-96 shall be implemented according to the characteristics, transportation, storage conditions and storage period of the packaged products

1.2 manufacturing process

the manufacturing process of moisture-proof packaging materials should be designed according to the internal properties and moisture-proof mechanism of polymer films. Biaxially oriented polypropylene (BOPP) film with high mechanical strength and good moisture resistance is selected. After vacuum aluminizing, PVDC (polyvinylidene chloride) lotion with excellent moisture resistance is coated to prepare composite materials with excellent moisture resistance

vacuum aluminum plating process is to heat and melt the metal aluminum to evaporation under high vacuum, and the aluminum atoms condense on the surface of polymer materials to form a dense barrier layer - aluminum layer. Aluminum plating process requirements: the vacuum degree shall not be lower than MPa to avoid brown stripes or uneven thickness of aluminum layer; Control the system tension and turn on the cooling system to avoid stretching deformation of the film when heated; Accurately control the coiling speed (250~300m/min), aluminum feeding speed (0.6~1.0m/min 2mm aluminum wire) and the heating current of the evaporation boat to obtain a better aluminum layer thickness (250? ~300?). Aluminum atoms block the gaps in or between plastic molecular chains, which greatly enhances the water vapor barrier performance of the film. PVDC lotion is prepared from vinylidene chloride and acrylate by lotion polymerization. The lotion is coated on the surface of vmbopp (polypropylene plating or aluminum with constant zero position change) film, and then plasticized and crystallized into a high barrier composite film. Coating process requirements: use anionic surfactant to adjust the surface tension of lotion at about 40dyn/cm2, and the amount of diluent should not be too large to prevent poor drying; The coating thickness is 2~3 μ M range, set the step temperature of infrared drying source to ensure sufficient plasticization and crystallization of lotion; Add a small amount of anti sticking agent and start the cooling system to avoid film adhesion; The temperature of the curing room is set at 40~45 ℃ and the curing time is 36~48h, so that it can crystallize and solidify fully and obtain excellent water vapor barrier performance. The moisture permeability of the moisture-proof polymer composite formed by this process meets the technical requirements of relevant standards

2 anti mold invasion

2.1 technical performance

chemical products, precision machinery, electronic devices, instruments and meters are very prone to mold invasion under appropriate temperature, humidity, nutrients, light, oxygen and other environmental conditions during transportation, use and storage. The national standard gb/t4768-95 "mould proof packaging" stipulates that the grade of mould proof packaging should be determined according to the anti mould invasion ability of the product, the environmental conditions involved in transportation and storage, the structure of the packaging, the mould resistance of the selected packaging materials and the results of mould test. Mold test shall be carried out according to the national standard gb/t4857.21-95 mold proof test of packaging and transportation packages or national standard gjb573a-98.305 at the specified temperature, humidity, strain and test cycle

2.2 production process

in order to obtain certain mildew resistance of polymer materials, it is necessary to mix mildew resistant substances such as phenolic compounds, organometallic compounds, nitrogen-containing compounds, halogen-containing compounds, sulfur-containing compounds, etc. with thermoplastic resins such as polyethylene (and calculate the cross arm stroke fault value PE), polypropylene (PP), polychloride, and ethylene (PVC) expressed as the percentage of gauge distance, and add a variety of additives. After mixing Granulate and prepare mould proof resin. The carrier resin is low-density polyethylene resin (LDPE) with good moisture resistance, low temperature resistance, easy heat sealing and chemical erosion resistance; Organic fungicides such as tributyltin chloride are added to LDPE resin in a certain proportion (%). Additives should be added in a certain order and fully stirred. The selection of additives should pay attention to their compatibility, compatibility with resin and durability, and adapt to the process conditions. The three-layer (ABC) coextrusion blown film dry composite process is often used to make mold proof polymer composites with mold proof resin. Add mold proof resin into a fabric bucket and extrude. The process requirements: appropriately reduce the heating temperature of each area of the extruder, increase the screw speed, and increase the number of filter layers or meshes to ensure good melt plasticization; Choose the appropriate expansion ratio and traction ratio; B. C fabric bucket adopts low-density polyethylene resin (LDPE) and linear low-density polyethylene resin (LLDPE) with high mechanical strength and less slippery agent content. It should be noted that the mi (melt index) of mold proof resin, LDPE and LLDPE should be as close as possible. The C surface of the film is corona treated to make its wetting tension greater than 38dyn/cm2, and the moisture-proof and mildew proof polymer composite is prepared by dry compounding with the moisture-proof polymer material

3. Conclusion

the design of moisture-proof and mold proof polymer packaging materials should be based on the product technical requirements and the conditions of mold growth and development, reasonably select packaging materials and packaging technology, strictly implement the relevant standards of moisture-proof and mold proof, control the production and circulation environment, use pre drying, vacuum, fill inert gas and seal the packaging, control the temperature and relative humidity, and make the packaging meet the requirements of moisture-proof and mold proof packaging grade

Author: Yang Hulin, Zhang Husheng