The hottest moisture-proof and mildew proof polyme

2022-08-09
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Moisture proof and mildew proof polymer composites

chemical products such as gunpowder, explosives, primary explosives and other materials with strong moisture absorption are very vulnerable to moisture failure; Electronic instruments and core boards, precision machinery, instruments and meters are prone to rust or mold erosion when affected with moisture. The national military standard gjb1444-92 stipulates that only when the water vapor permeability of packaging materials is less than 3G · 30d can they meet the moisture-proof performance requirements of chemical products on packaging materials

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 good mechanical strength and moisture resistance is selected. After vacuum aluminizing, PVDC (polyvinylidene chloride) lotion with excellent moisture resistance is coated to prepare composite materials with excellent barrier properties

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 (280 ~ 320m ﹤ min) and aluminum feeding speed (0.4 ~ 0.7m ﹤ min Φ 2mm aluminum wire) and evaporation boat heating current to obtain a better aluminum layer thickness (more than 250!!). 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 aluminized) film, which is plasticized and crystallized into a high barrier composite film. The coating technology company has deeply studied the production process requirements of various processes such as tire production, molding, vulcanization, testing, storage and so on: anionic surfactant is used to adjust the surface tension of lotion at about 40dyn C, and the amount of diluent should not be too large to prevent poor drying; The coating thickness is 2.0 ~ 3.0 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 chamber 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 requirements of the national military standard gjb1444-92

everyone is familiar with precision machinery, chemical products, communication devices, instruments, etc. during transportation, use, storage, under appropriate temperature, humidity, nutrients, light, oxygen and other environmental conditions, mold erosion is very easy to occur. 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. The mold test is carried out according to the national military standard gjb573a-98.305 at the specified temperature, humidity, strain and test cycle

in order to obtain certain mold resistance of polymer materials, it is necessary to mix mold resistant substances such as phenolic compounds, organometallic compounds, nitrogen-containing compounds, halogen-containing compounds, sulfur-containing compounds, etc. with thermoplastic resins such as polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) in a certain proportion, and add a variety of additives. After mixing, plasticizing and granulating, the mold resistant resin is prepared. The carrier resin is low-density polyethylene resin (LDPE) with good moisture resistance, low temperature resistance, easy heat sealing and chemical erosion resistance; Add organic fungicides such as tributyltin chloride into LDPE resin according to 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 following two processes are often used to make mold proof polymer composites with mold proof resin:

three-layer (ABC) coextrusion blow molding dry compounding

Add mold proof resin into a fabric bucket for extrusion. The process requirements: under the condition of ensuring good film plasticization, appropriately reduce the heating temperature of each area of the extruder; The screw speed matches the heating temperature; 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 this film is corona treated, and the wetting tension of food and drugs is greater than 38dyn/cm2, which is compounded with the outer material by dry method. The mould proof polymer composite was prepared by dry compounding process, and the A-side was used as the functional surface of the mould proof material

double sided (AB) coextrusion composite

add mold proof resin into a fabric bucket for extrusion. The technological requirements: select the mold proof resin with high MI value (about 7g/10min); Properly adjust the melt temperature close to the viscosity to prevent metamorphism due to excessive temperature; Screw speed, heating temperature and vehicle speed are matched; Appropriately increase the melt pressure and increase the number of filter layers or mesh. B. coating grade polyethylene (LDPE) resin with the brand of 1c7a is added to the fabric bucket. The surface of the processed material is coated with polyurethane adhesive, which is dried in the oven and then compounded with surface B. Select the appropriate solid content and coating roll to make the dry weight of adhesive within 1-2g. Other process requirements are the same as dry compounding. The mold proof polymer composite material made by double-sided (a, b) coextrusion composite process, with side a as the mold proof functional surface

the moisture-proof and mildew proof polymer packaging materials must also have sufficient mechanical strength to ensure that the products will not be damaged in case of extrusion, friction, impact, vibration and fall during stacking, loading, unloading, transportation and storage. Therefore, in the design process of product packaging, it is necessary to select materials with good mechanical strength and their optimal combination in order to enhance the comprehensive performance of packaging materials

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