What is the difference between light-curing coatings and solvent-based coatings?

Quick answer: In most UV systems, photoinitiators are selected by balancing wavelength fit, through-cure, color control, and line speed. Buyers usually compare a blended package instead of one isolated product.

Light-curing coating is an efficient, environmentally friendly, energy-saving and high-quality material, and the related technology has been rapidly developed in recent years due to its good characteristics.

The main components of light-curing coatings generally include: photoinitiators, active diluents, oligomers and various additives. Light-curing coatings undergo photochemical reactions under light irradiation, which is different from the role of thermochemically reactive substances. It is for this reason that the light-curing coating properties are also different.

The characteristics of light curing technology.

1. Light curing only needs to be carried out at room temperature, which can meet the construction of products not suitable for heating and drying method.

Conventional solvent-based coatings take hours or even days to dry out. Light-cured products are more productive, saving space for stacking semi-finished products and better meet the requirements of large-scale automated production. At the same time, the quality of light-cured products is also easier to ensure.

2. In addition to increased productivity and energy savings, light curing technology also enables higher levels of coating quality, such as mechanical properties and gloss.

Compared with solvent-based coatings, UV light curing energy used is only equivalent to 1/10~1/5 of the former, light curing coatings at room temperature and rapid cold curing characteristics are also unmatched by other coatings. Baking type coatings and powder coatings need to be heated after painting to promote solvent evaporation and chemical cross-linking reaction, compared to this, light-curing coatings greatly save energy.

3. Because of the “no” solvent system, users do not need to install expensive sewage facilities.

Conventional solvent-based coatings usually contain 30% to 70% inert solvents, which almost all evaporate into the atmosphere when the film dries, causing considerable environmental hazards.

In addition, light curing requires only the radiation energy used to excite the photoinitiator, unlike traditional thermal curing that requires heating the substrate, material, surrounding space and evaporation to remove the heat of water or organic solvents used for dilution, thus saving a lot of energy.

Applications of light curing technology.

Chemical, mechanical, electronic, light industry, communications, automotive and other fields. Light-curing coatings include bamboo, wood flooring, decorative panels, furniture and other UV wood coatings; automotive parts, instruments, CDs, decorative panels, credit cards and other UV plastic coatings; steel rust, color coated steel, printed iron cans, cans and other UV metal coatings; decorative paper, written surface coating.

Light-curing coatings reduce the pollution of the air, the danger to humans and the risk of fire. The production of light-curing coatings has grown rapidly in recent years, information shows that in 2011, China’s light-curing coatings production of 75,177t, an increase of 39% over 2010, an increase of 131% over 2007. As an environmentally friendly “green technology”, light-cured coatings and then the United States, Europe, Japan and so on as a priority technology, but also in line with the growing needs of the public in China.

How formulators usually evaluate this photoinitiator topic

When technical buyers or formulators screen photoinitiators, the most useful decision frame is usually cure quality plus application fit: which package cures reliably, keeps appearance acceptable, and still works under the lamp, film thickness, and substrate conditions of the actual process.

• Match the package to the lamp first: mercury lamps, UV LEDs, and visible-light systems can rank the same photoinitiators very differently.
• Check depth cure and surface cure separately: a film that feels dry on top can still be weak underneath.
• Balance yellowing with reactivity: the strongest deep-cure route is not always the best commercial choice if color or migration risk becomes unacceptable.
• Use the final formula as the benchmark: pigment load, monomer package, and film thickness can all change the apparent ranking of the same initiator.

Recommended product references

• CHLUMINIT TPO-L: A strong low-yellowing reference for LED-oriented UV systems.
• CHLUMINIT 819: Useful when a formulation needs stronger absorption and deeper cure support.
• CHLUMINIT 184: A classic free-radical benchmark for fast surface cure in many UV systems.
• CHLUMINIT TMO: A valuable comparison point when lower yellowing or TPO-replacement discussions matter.

FAQ for buyers and formulators

Why are blended photoinitiator packages so common?
Because one product may control yellowing or lamp fit well while another improves cure depth or line-speed performance, so the full package is often stronger than any single grade.

Should incomplete cure always be solved by adding more initiator?
Not automatically. The real limitation may be the lamp, film thickness, pigment shading, or the rest of the reactive system rather than simple under-dosage.