Scattered light in adhesive technology

An underestimated risk

Scattered light is a form of diffuse light that disperses in various directions instead of traveling in parallel, straight paths. To better understand the formation of scattered light, it helps to examine the phenomena of light refraction and reflection.

When light encounters a medium with a different optical density, part of that light is refracted, while another part is reflected. The amount of reflected light depends on the difference in optical density between the two media.

How does scattered light affect the curing process of adhesives?

Light-curing adhesives like DELO PHOTOBOND contain photoinitiators that trigger a curing reaction when exposed to light of a specific wavelength. High-intensity LED lamps such as the DELOLUX 20 can fully cure these adhesives within seconds. In contrast, the intensity of scattered light is usually too low to achieve complete curing. Despite its low intensity, scattered light can still adversely affect industrial processes:

• Uncontrolled and Premature Reactions: Scattered light, with its varied wavelengths and intensities, can have unwanted effects on light-curing adhesives by randomly activating photoinitiators. This can lead to uneven or incomplete curing and even premature curing, which is problematic if components need further adjusting or if application techniques are not ready for full curing. Even at partial intensity, scattered light can initiate a superficial or premature activation in some adhesives.
• Clogging of Dispensing Needles: Scattered light can prematurely cure material residue at the tips of dispensing needles, causing blockages that disrupt even dispensing and hinder precision. This results in undesirable dosing effects like drop formation or uneven adhesive distribution.
• Disruption of Process Control: Unexpected scattered light can interfere with standardized production processes by affecting process parameters and curing times. This can make it challenging to maintain consistent quality and necessitates adjustments to ensure desired outcomes.
• Energy Efficiency: Scattered light disrupts the targeted use of light sources, leading to suboptimal energy use during curing processes. This can reduce energy efficiency, and potentially increase production costs.

How can you reduce the impact of scattered light?

Effective measures are crucial to mitigating the influence of scattered light on industrial processes. Ensuring the quality and efficiency of processes, particularly in light-curing adhesives, can be achieved through several practical approaches:

• Shields: Use physical barriers or shields to reduce the direct impact of scattered light on sensitive production areas. Special coverings or a well-thought-out facility design can also minimize unwanted light intrusion. Our consulting services can offer further assistance here.
• Optimized Lighting: By directing light strategically, you can minimize scattering effects and maximize light efficiency where needed. Using lighting devices like DELOLUX 50, with non-glare or low-reflection features, further supports scattering reduction.
• Technological Adjustments: Invest in specialized curing lamps designed to deliver consistent results, even in the presence of scattered light. These devices often feature more precise control mechanisms and optimized settings. Additionally, use dispensing systems less susceptible to scattered light influences. Utilizing advanced sensor technologies or special materials can enhance dosing effectiveness, even in challenging conditions.

Measuring scattered light

In industrial processes, controlling and measuring scattered light is crucial for ensuring production efficiency and quality. Scattered light measurement aims to identify and eliminate unwanted light dispersions, thereby optimizing adhesive curing processes. Precise measurement techniques help detect and adjust problematic areas to maintain consistent product quality and production consistency.