Shadow free adhesives are also known as UV adhesives, photosensitive adhesives, and UV curable adhesives. Shadow free adhesives refer to a class of adhesives that must be irradiated by ultraviolet light to cure. They can be used as adhesives, as well as adhesives for paints, coatings, and inks. UV is the abbreviation for Ultraviolet Rays, which means ultraviolet light. Ultraviolet (UV) rays are invisible to the naked eye, and are electromagnetic radiation beyond visible light, with wavelengths ranging from 10 to 400 nm. The principle of shadowless adhesive curing is that the photoinitiator (or photosensitizer) in UV curable materials absorbs UV light under ultraviolet irradiation and generates living free radicals or cations, initiating monomer polymerization, cross-linking, and branching chemical reactions, enabling the adhesive to convert from a liquid state to a solid state within seconds.
Main Components of the Catalog Common Application Product Features Shadowless Adhesive Advantages: Environmental/Safety Economic Compatibility Usage Methods Operating Principles: Operating Instructions: Disadvantages of Shadowless Adhesive: Comparison with Other Adhesives Application Fields Crafts, Glass Products, Electronics, Electronics, Optics, Digital Optical Disk Manufacturing, Medical Supplies, Other Uses Notes
Main component Prepolymer: 30-50% Acrylate monomer: 40-60% Photoinitiator: 1-6%
Auxiliary agent: 0.2~1%
Prepolymers include: epoxy acrylate, polyurethane acrylate, polyether acrylate, polyester acrylate, acrylic resin, etc
The monomers include: monofunctional (IBOA, IBOMA, HEMA, etc.), bifunctional (TPGDA, HDDA, DEGDA, NPGDA, etc.), trifunctional and multifunctional (TMPTA, PETA, etc.)
Initiators include: 1173184907, benzophenone, etc
Additives can be added or not. They can be used as adhesives, as well as adhesives for paints, coatings, inks, and other adhesives.  Common applications include the bonding of materials such as plastic to plastic, plastic to glass, and plastic to metal. Mainly aimed at self-adhesion and mutual adhesion of plastics in the handicraft industry, furniture industry, such as tea table glass and steel frame bonding, glass aquarium bonding, including PMMA acrylic (plexiglass), PC, ABS, PVC, PS, and other thermoplastic plastics.
Product characteristics: Universal products have a wide range of applications, and have excellent bonding effects between plastics and various materials; High adhesive strength, damage test can achieve plastic body cracking effect, positioning in a few seconds, reaching the highest strength in one minute, greatly improving work efficiency; After curing, the product is completely transparent, without yellowing or whitening for a long time; Compared to traditional instant adhesive bonding, it has advantages such as environmental resistance, non whitening, and good flexibility; The destruction test of P+R keys (ink or electroplating keys) can tear the silicone rubber skin; Excellent resistance to low temperature, high temperature and high humidity; It can be applied through automatic mechanical dispensing or screen printing for easy operation.
Advantages of shadowless adhesive: environmental/safety ● No VOC volatiles, no pollution to the ambient air;
● There are relatively few restrictions or prohibitions on adhesive components in environmental regulations;
● Solvent-free, low flammability
Economy ● Fast curing speed, which can be completed in a few seconds to tens of seconds, which is conducive to automated production lines and improving labor productivity
● After solidification, it can be tested and transported, saving space
● Room temperature curing, saving energy, for example, the energy required to produce 1g of light curable pressure sensitive adhesive only requires 1% of the corresponding water-based adhesive and 4% of the solvent based adhesive. It can be used for materials that are not suitable for high-temperature curing, and the energy consumed by UV curing can be saved by 90% compared to thermal curing resin
The curing equipment is simple, requiring only lamps or conveyor belts, saving space
Single component system, without mixing, easy to use
Compatibility ● Can be used for temperature, solvent, and moisture sensitive materials
● Controlled curing, adjustable waiting time, and adjustable curing degree
● Can be repeatedly applied and cured
● UV lamps can be easily installed on existing production lines without major modifications
Usage and Operating Principle: The process of applying opaque adhesive, also known as ultraviolet glue, requires ultraviolet radiation to the adhesive solution before it can be cured, which means that the photosensitizer in the opaque adhesive will bond with the monomer when exposed to ultraviolet radiation. Theoretically, the opaque adhesive will almost never solidify under the irradiation of no ultraviolet light source.
There are two sources of ultraviolet light: natural sunlight and artificial light sources. The stronger the UV, the faster the curing speed. Generally, the curing time varies from 10 to 60 seconds. For natural sunlight, the stronger the ultraviolet rays in sunlight on sunny days, the faster the curing rate. However, when there is no strong sunlight, only artificial ultraviolet light sources can be used. There are many types of artificial ultraviolet light sources, with significant power differences, ranging from a few watts for low-power ones to tens of thousands of watts for high-power ones.
The curing speed of the shadowless adhesive produced by different manufacturers or different models varies. “The shadowless adhesive used for bonding must be irradiated by light to solidify, so the shadowless adhesive used for bonding can generally only bond two transparent objects or one of them must be transparent, so that ultraviolet light can penetrate and irradiate the adhesive liquid.”. Take the high-efficiency concentrated ring ultraviolet lamp tube launched by a company in Beijing as an example. The lamp tube uses an imported fluorescent coating, which can emit ultra-strong ultraviolet rays. It can generally achieve positioning in 10 seconds and complete curing speed in 3 minutes. However, there is no such requirement for shadowless adhesives used for surface coating, covering, or fixing functions. Therefore, before using the shadowless adhesive, it is necessary to conduct a small test according to your specific process requirements and process conditions.
Post time: Apr-19-2023