company news about From black to light: Dual-cure (UV+thermal) for dark substrates

From black to light: Dual-cure (UV+thermal) for dark substrates

  In the field of industrial coating and material processing, the surface treatment of dark substrates has long been regarded as a "no man's land" for technical breakthroughs. Whether it is the piano black panel of the car interior, the metal matte coating of home appliances, or the dark composite material in the consumer electronics field, the traditional single curing system (such as pure UV curing or pure thermal curing) always faces a core contradiction: due to the strong light absorption of dark substrates, the traditional single UV curing often leads to incomplete deep curing due to insufficient light penetration, causing problems such as poor adhesion and uneven surface shrinkage.

  Traditional UV curing relies on photoinitiators to absorb ultraviolet light to generate free radicals, but when the coating is applied to a dark substrate, high concentrations of pigments (such as carbon black) or dark substrates will form a natural light barrier. Experimental data show that the transmittance of black coatings with a thickness of more than 50μm to 365nm ultraviolet light is less than 5%, resulting in a cross-linking degree at the bottom of the coating of only 30%-40% of the theoretical value.

  This curing defect is directly manifested as reduced weather resistance and insufficient wear resistance of the coating, which is particularly prominent in high-end fields such as automotive interiors and electronic product housings. Although the thermal curing system can avoid the problem of light penetration and achieve uniform curing through heat conduction, the high temperature of more than 150°C not only leads to the risk of material deformation, but is also more likely to cause deformation in heat-sensitive substrates (such as plastics and composite materials).

  The dual-curing system (UV+thermal curing) provides an innovative solution to the curing problem of dark substrates.

  The dual-curing system forms an initial structure by rapid surface cross-linking initiated by UV light, and then completes the deep polymerization reaction with the help of thermal curing, which not only solves the limitation of light penetration, but also improves the overall density of the material. This synergistic mechanism is particularly suitable for composite materials containing carbon black and dark pigments. The molecular chain movement in the thermal curing stage can fill the microporous defects after UV curing, so that the shear strength of the material after thermal curing at 120-150℃ is increased by more than 40%.

  The dual-curing system achieves full-dimensional control from material interface to deep structure through the sequential coordination of UV light and thermal energy. The specific breakthroughs are reflected in three dimensions：

  1. Gradient design of energy penetration

  In the UV stage, a high-energy short-wave light source (such as LED-UV) is used to quickly cure the surface layer to form a dense protective film; in the thermal curing stage, a gradient temperature increase (50-120°C) is used to activate the deep latent curing agent, so that the cross-linking reaction is carried out layer by layer from the surface to the inside of the matrix. Experiments by chemical giant BASF have confirmed that this process reduces the internal stress of the coating by 32% and increases the bonding strength with the substrate to 8.5MPa.

  2. Spatiotemporal decoupling of chemical reactions
  The curing process can be precisely controlled by designing an orthogonal reaction system of UV-sensitive groups (such as acrylates) and heat-activated groups (such as blocked isocyanates). This "staged cross-linking" strategy enables the coating to maintain a high hardness (≥3H) while still achieving an elongation at break of more than 15%, completely solving the contradiction between rigidity and toughness in traditional processes.

  3. Dynamic process window

  Adaptive intelligent dual-curing equipment can adjust UV dosage and hot air parameters in real time according to the color and thickness of the substrate. The AI control module developed by Core Rate Intelligence can increase the curing yield of dark substrates from 68% of single UV to 98%, while reducing energy consumption by 40%. This dynamic adaptation capability makes the dual-curing system a "flexible solution" to meet personalized manufacturing needs.