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Flexo printing machines are suitable for a variety of materials, including paper, metal foil, plastic film, and non-woven fabrics. Consequently, the ink used should be compatible with the material. The ink used in flexographic printing machines features low viscosity and quick drying. The low viscosity of the inks ensures excellent ink transfer properties for flexographic printing machinery. Due to the rapid drying of flexographic inks, adjacent colours can achieve dry trapping, making them highly suitable for printing on non-absorbent substrates such as milk powder packaging film, candy wrappers, and chocolate wrappers. This article will discuss how to select flexographic inks based on four aspects: substrate material, performance requirements, printing effect, and cost.

Flexography Machine for Coffee Paper Cups

Substrate Material

The most common substrates for flexographic printing include paper, plastic film, aluminium foil, metallised film, non-woven fabric, and breathable film. 

Paper

Paper substrates such as cupcake paper cups, soup paper bowls, takeaway paper bags, and hamburger paper boxes typically utilise water-based inks. Water-based inks use water-soluble or water-dispersible resins as binders. Compared to solvent-based inks, they eliminate the hazards posed by certain toxic substances to human health and prevent contamination of packaged goods. Moreover, their eco-friendly nature means flexographic presses require no additional fire suppression systems or solvent recovery equipment, thereby reducing environmental protection expenditure.

However, water-based inks are unsuitable for film printing due to their slower drying speed and inferior gloss properties.

Plastic Film

Solvent-based inks are often used for plastic films such as PE, PP, PET, BOPP, and PVC used in the production of meat wrapping film, fresh fruit wrapping film, and body soap wrapper packaging film.

Solvent-based inks offer fast drying, excellent gloss, strong adhesion, and abrasion resistance. Alcohol solvents are the least toxic of organic solvents and do not corrode or damage flexographic printing plates. Good alcohol-soluble inks offer excellent flow, fast drying, strong adhesion, and high gloss.

However, compared to water-based inks, alcohol solvents pose certain environmental and safety risks.

Flexo Presses for Tissue Plastic Packaging Film Bags

Paper and Plastic Film

Flexographic UV inks are universal inks that can be printed on both paper and plastic films.

UV inks utilize ultraviolet radiation of a specific wavelength to transform liquid UV inks into solid inks through a photochemical reaction. UV inks are safe and reliable, with no solvent emissions, are non-flammable, and are environmentally friendly. They are suitable for packaging and printing products requiring high hygiene standards for food, beverages, alcohol, tobacco, and pharmaceuticals, such as medical sterilization pouches, cigarette boxes, and sandwich wrapping paper.

Aluminum Foil and Metallised Film

Aluminum foil and metallized films require specialized composite inks to ensure a compatible substrate with the adhesive or laminating layer.

Non-woven Fabrics and Breathable Film

Non-woven fabrics and breathable films generally use water-based inks or specialized inks to ensure breathability and environmental friendliness.

Flexo Printer for Baby Diaper Back Sheet

Performance Requirements

When selecting ink for flexographic printers, you can consider the required performance.

Abrasion and Water Resistance

Food packaging and consumer product packaging, such as gift paper bags and vitamin bottle labels, require high abrasion and water resistance.

Adhesion

Film substrates, such as sauce powder aluminum foil bags and chocolate bar seal film bags, require corona or flame treatment to increase surface energy and ensure ink adhesion.

Environmental Regulations

Export packaging, such as butter wrappers and wine shipping packaging paper boxes, must comply with FDA and EU food contact regulations and typically utilize low-VOC water-based inks.

Flexographic Machine for Biscuit Sealing Film

Printing Effect

If you require vibrant, saturated colors with good coverage (for applications like ice cream cups and candy bags), choose water-based inks.

If you require fine dots and high-definition overprint (for applications like perfume labels and gold foil shampoo stickers), choose UV inks.

If you require high gloss and scratch resistance (for applications like wet wipes packaging and jelly cup sealing film), choose solvent-based or UV inks.

Flexo Printing Machine for Nuts Packaging Pouches

Cost

Water-based inks are relatively inexpensive and suitable for high-volume production.

Solvent-based inks, while slightly more expensive, are suitable for high-end film packaging.

UV inks dry quickly and produce beautiful results, but they also require high equipment investment and consumables.

Flexo Printing Press for Baking Bread Packaging Bags

The right flexo ink can help enhance product value and brand effectiveness. Water-based inks are preferred for printing on paper-based materials. For printing on film-based materials, solvent-based inks or specialized composite inks are preferred. UV inks can be considered for high-end labels or specialized packaging. Manufacturers can consider substrate material, performance requirements, print quality, and cost to select the most suitable flexo ink for products such as milk tea paper cups, disposable medical face masks, QR code labels, and sanitary pad outer wrap films.