Thermoplastic Lenses in LED Lighting: Degradation Concerns for Greenhouse Growers
As the global lighting industry rapidly adopts energy-efficient LED modules, a new study from Dow highlights potential limitations in the longevity and performance of thermoplastic optics, particularly those used in greenhouse lighting applications. Researchers found that many thermoplastic lens clusters discolor over time and can ultimately fail, impacting light output and potentially requiring premature replacement.
The Dow Study: Blue Light Photothermal Aging
The research, detailed in the white paper “Blue Light Photothermal Aging of Thermoplastic and Silicone Lens Clusters,” authored by Martijn Beukema and Kevin Van Tiggelen, Senior Technical Service & Development Scientists for Lighting at Dow, examined the effects of blue light photothermal aging on various optical materials. The study evaluated silicone and thermoplastic optics made of polycarbonate (PC), polymethyl methacrylate (PMMA), and high-temperature resistant PMMA (HT-PMMA). Researchers subjected lens clusters to stress simulating the operating conditions of high-power LED lighting.
“The principal finding is that most of the tested thermoplastic lens clusters discolour over time and ultimately fail catastrophically,” the researchers reported. While gradual discoloration is known to reduce light output, the study indicates that catastrophic failure can be difficult to predict and requires extended testing periods.
Implications for Greenhouse Lighting
The findings are particularly relevant for greenhouse growers increasingly utilizing LEDs for supplemental lighting to improve crop yields. Philips offers a range of greenhouse LED grow lights for various crops, including vegetables, fruits, and floriculture. However, the choice of lens material can significantly impact the long-term performance of these systems.
Thermoplastic lenses, while often more cost-effective initially, may not offer the same durability as silicone optics. Degradation can lead to reduced light transmission, impacting plant growth and potentially necessitating frequent replacements, increasing operational costs.
Silicone Optics as a Reliable Alternative
Dow, a producer of moldable optical silicones under the SILASTIC™ brand, suggests silicone optics as a more reliable alternative. According to Martijn Beukema, “Luminaire manufacturers are encouraged to take this data into account when choosing optical materials during the design process, and to recognize silicone optics as a reliable alternative that can enhance product longevity and minimise the risk of major failures.”
The research extends beyond horticultural applications, encompassing street and sports lighting where LED modules are also subject to long-term exposure to photothermal stress.
The Growing LED Lighting Market
The Dow study arrives at a time of significant growth in the global lighting industry, driven by the demand for energy-efficient LED solutions. LED lighting offers benefits in efficiency, light output, energy savings, and design possibilities. Ensuring the longevity and light output efficiency of these LED modules is therefore crucial for maximizing return on investment.