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Application of plasma surface treatment machine on printing adhesion

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18 Nov,2020

Application of plasma surface treatment machine on printing adhesion:

 

Flexible packaging is undergoing a technological revolution to improve consumer convenience and convenience, and to provide new solutions to a range of challenges throughout the production and distribution chain. High-performance film structures, packaging structures and applications, as well as printing technologies, will continue to bring flexible packaging to existing and new markets. Although traditional corona and flame surface pretreatment methods have been commonly used for flexible packaging of finished products, which are mainly used for drawing the packaging structure and strengthening the coating, atmospheric plasma surface treatment technology can also improve the adhesive ability of flexible packaging.

 

The atmospheric plasma treatment process has been developed for the treatment/functionalization of various materials and has its unique advantages over corona, flame and primer treatments currently used in flexible packaging applications. Atmospheric plasma surface treatment systems can produce uniform high density plasma using large amounts of inert and reactive gases at atmospheric pressure and low temperature. Atmospheric plasma treatment is similar to vacuum plasma treatment and can be used for surface functionalization of materials. APT production equipment testing has been successfully applied to the treatment of polypropylene, polyethylene, polyester and other materials. The surface energy of the processed material (without any backside treatment or pinhole) can be greatly increased, thus improving its wettability, printability and adhesion.

 

The atmospheric plasma surface treatment process involves contacting the polymer in a low temperature, high density glow discharge. A plasma is a partially ionized gas that contains a large number of excited atoms, molecules, ions, and free radicals. The gas molecules are excited by introducing the gas (transported in an open design) into an electric field (usually at high frequencies). Under the action of high-frequency electric field, free electrons generate energy, collision with neutral gas molecules and transfer energy, causing them to dissociate, forming many active substances. The surface of the excited material interacts with the solid surface of the plasma to modify the surface chemically and physically. The effect of a plasma on a particular substance depends on the chemical reaction between the surface and the reactants in the plasma. When the contact energy is low, the interaction between plasma and surface can only change the surface of the material. The influence is limited to the depth region of several molecular layers without changing the volume characteristics of the substrate.

 

The changes caused by the surface depend on the surface composition and the gases used. Gases or mixtures used to treat polymer plasmas include nitrogen, argon, oxygen, nitrous oxide, methane, ammonia and other substances. Each gas produces a unique plasma composition and different surface properties. Such as plasma induced oxidation, nitrification, hydrolysis or amination, the surface can be rapidly and effectively improved. Based on the chemical properties of the polymer, replacing a portion of the molecule after a surface contact reaction makes the polymer moist. Regardless of the gas composition, the surface treatment can alter the flexible packaging substrate to a degree that depends on chemical and process variables: ablation, crosslinking, and activation. High-energy particles (i.e., free radicals, electrons and ions) bombade the polymer surface and break the covalent bonds of the polymer backbone, thus forming a polymer chain with lower molecular weight. When the long molecular components become short, volatile oligomers and monomer by-products will evaporate (ablative) and excrete out. Crosslinking with an inert working gas (argon or helium), a bond fracture occurs on the polymer surface. But since there is no free radical scavenger, it can connect to nearby free radicals in a different chain (cross-linking).

 

Atmospheric plasmas with high density under atmospheric pressure contain high active substances, which can obviously increase the surface area and form polar groups on the polymer surface, thus making the matrix and its interface (such as ink, paint, adhesive) produce strong covalent bonding. By using atmospheric plasma surface treatment, water-based ink on polyester base structure can be used to improve the adhesion of ink.

Application of plasma surface treatment machine on printing adhesion

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