Performance and structure of the hottest PVDC coat

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The performance and structure of PVDC coating film

the coating process of PVDC latex is different from the blowing and extrusion process of PVDC resin. There are only coating spreading and heating and drying processes in the coating of latex. There is no additional additive in the final film formation, so although the coating is only m thick, its barrier performance to oxygen and wet steam is several times equivalent to that of 25 m blown film, which can be seen from table 1

as a barrier packaging material, PVDC coating film is most suitable for making composite packaging bags, because the mechanical and some physical properties of the coating film are determined by the substrate to be coated, and the final permeability, fragrance retention and oil resistance are provided by the coating. Users only need to determine the machinery, fragrance and oil resistance of my packaging materials according to the characteristics of the packaged items and the circulation environment Physical performance requirements and the degree of protection to select the barrier ability of the substrate and coating

the barrier ability of PVDC coating is not only directly related to the aggressiveness of the coating, but also related to the film-forming process and process control of the coating. For example, the film-forming process of PVDC latex coating is: latex state (state 1), drying (state 2) deformation film state (state 3). State 1 to state 2 must ensure that the temperature of the coating is high enough; Ensure sufficient energy supply to make water volatilize at a uniform speed; Ensure that there is no excessive drying, and the coating cracks due to the penetration of water vapor at the bottom layer after the coating pinholes or surface crusting occur due to the boiling of waterproof parts

in the process of state 2 to state 3, it should be ensured that there is sufficient air velocity to purge the water film on the coating surface, so that there is a reasonable water gradient distribution from the interior of the coating to the surface, so that the water can migrate to the surface quickly. It is necessary to ensure that state 3 has a reasonable existence time in the drying process, so as to further deform the PVDC coating and fully move the molecules, so as to improve the crystallinity and eliminate the low amount of PVDC as much as possible. These are conducive to improving the barrier performance of PVDC coating, ensuring that PVDC has strong solvent resistance and effectively reducing the residual solvent in the process of printing and composite processing; It can ensure the peel strength of the coating and improve the gloss and transparency of the coating film

it is certain that the drying and film-forming process of PVDC is not so simple. How to fully understand this process and design a more reasonable process control process is a long-term topic for PVDC workers. Only with reasonable process design and accurate process control, can we produce a perfect PVDC coating, "Meador explained, and the real face of PVDC, a barrier packaging material, be correctly reflected

it is really not easy to reflect this, so there is no quality guarantee to realize PVDC emulsion coating production on the Xerox or printing machine, which can only provide limited barrier performance, and is likely to bring other quality problems. Such as poor oil and solvent resistance, insufficient composite peel strength, etc. In addition, we cannot scribe the coating surface as flat as the horizontal plane. From the microscopic point of view, any surface has a roughness. At present, it is not difficult to find products with coarser coatings in the domestic market

the rough coating (even the raw material industry in Liaoning Province will initially realize the transformation and upgrading of industrial structure and the optimization of industrial layout to the emergence of coating streamline) not only brings uneven defects of ink splashing transfer to printing, but also defects such as thick coating, insufficient drying, insufficient density of coating, insufficient barrier ability, weak solvent resistance and low composite peel strength at the peak of roughness. Strictly speaking, this is not a qualified PVDC coating film product

how to effectively combine the equipment structure, latex formula, tension setting, temperature control and other aspects is the core technical secret of PVDC coating manufacturers, that is, the so-called W. In short, PV DC is a barrier packaging material that has been proved by more than 30 years of use in developed countries. At present, there is no barrier packaging material that can be replaced by materials with better value and function

at present, the key is how to better understand and master the performance and reasonable processing process of PVDC. To objectively show its true appearance

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