Screen printing or serigraphy is a widely used technique used in various industries because of its vibrant color reproduction and durability. Commonly used in the fashion industry, screen printing has found its way down onto plastic substrates. In this blog, we are going to discuss the process in detail and provide you with the details of the material used and the process of screen printing onto plastic.
Understanding the Basics
Serigraphy acts as a secondary processing of plastic that involves the transfer of visuals onto plastic surfaces through specialized techniques. Plastic's inherent properties, such as dyeability and solarized colorfastness limitations, necessitate this secondary processing for improved aesthetics.
Plastic Surface Preparation
Given the non-porous nature of plastic, surface preparation becomes imperative for optimal ink adhesion. The molecular structure of plastic contains polar substances, requiring pre-printing treatments to enhance ink adhesion and achieve vivid, distinct images.
Suitable Substrates for Screen Printing
Different types of plastic products necessitate specific serigraphy methods. Whether it's plain printing for sheet and plane plastics, curved silk printing for cambered surfaces, or indirect screen printing for abnormalities, the selection depends on the plastic's characteristics.
Polyvinyl Chloride (PVC): Known for its bright colors, anti-break properties, and affordability, PVC is widely used. However, it's not suitable for food containers due to potential toxicity.
ABS Resin Plastic: Common in televisions and calculators, ABS resin offers easy processing and forming capabilities.
Polyethylene Plastics: Versatile and commonly used, polyethylene can be molded into various finished products through extrusion, injection molding, and other processes.
Polypropylene: Essential for various molding methods, polypropylene can be processed into pipes, boxes, containers, films, and fibers.
Ink Formulation for Plastic Printing
Screen printing ink for plastic printing differs significantly from ink used for paper. Formulated with plastic resins, synthetic solvents, organic solvents, and colorants, it exhibits excellent colloidal fluid properties, ensuring stable adhesion, fast drying, and exceptional printing performance.
How Does it Work?
Screen printing involves pressing the eco friendly inks through a stenciled mesh screen onto a substrate. Plastic substrates, including PVC, ABS resin, polyethylene, and polypropylene, undergo a precise process.
Screen Preparation:
Mesh Composition: Composed of synthetic polymers like nylon, with varying apertures for different design details.
Frame Material: Frames, made of wood or aluminum, support the mesh under tension for effective printing.
Tensiometer Testing: Ensures proper tension for the mesh through the frame.
Stencil Creation:
Negative Image Blockage: Parts of the screen are blocked to create a stencil in the negative image of the design.
Emulsion Application: A pre-press process involves applying emulsion across the mesh.
Ultra-violet Exposure: The exposed areas harden, creating the stencil, while unexposed parts are washed away.
Printing Process:
Ink Application: Ink is poured onto one end of the screen, and a squeegee presses it through the mesh onto the plastic substrate.
Drying and Additional Supplies: Depending on the plastic part, additional supplies like vacuum pallets and drying racks may be required.
Applications
Serigraphy on plastic has evolved to meet the demands of various applications:
Printed Electronics: Thin-film coating for electronic devices with higher density internal structures.
Plastic Types and Applications:
Polypropylene for boxes, plastic bags, posters, and banners.
Polycarbonate for DVDs, CDs, bottles, lenses, signs, and displays.
Polyethylene terephthalate for bottles and backlit displays.
Polystyrene for foam containers and ceiling tiles.
Polyvinyl chloride for credit cards, gift cards, and construction applications.
Screen Print vs. Digital Print Processes
Digital printing differs from screen printing as it transfers an image directly onto a substrate using a specialized printer. While digital printing is more cost-effective for small batches, screen printing offers intensity of color and textured effects that digital printing cannot replicate.
Advantages of Silk Screen Printing on Plastic
Silk printing on plastic products presents a myriad of advantages:
Versatility: Suited for flat, curved, or spherical surfaces.
Durability: Resistant to fading, tearing, staining, wrinkling, or peeling.
Water and Steam Resistance: Withstands exposure to water and steam.
Cost Efficiency: A cost-effective printing method.
Recyclability: Easily recyclable, contributing to sustainable practices.
Customization: No creative restrictions, fully customizable.
User-Friendly: Easy operation with fast delivery.
Conclusion
Screen printing ink on plastic is a versatile and effective technique with diverse applications. From intricate designs on fabric to printing on various plastic substrates, this method continues to evolve to meet the demands of different industries. Understanding the intricacies of serigraphy on plastic is crucial for achieving optimal results.