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S-LEC® Multi-Layer Technology
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The first PVB interlayer to combine two high performance technologies.
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 Introduction. Technology is developing every day and driving us closer to the dream car, one that offers unparalleled comfort, safety and environmental protection. Factors that car manufacturers take very seriously in their quest to differentiate their vehicles from competitors. When looking at vehicle trends, glazing plays a much more important role than before, in terms of its functionality, with the emphasis on two or more functions being combined in one glass product. Naturally, PVB interlayer for laminated glass is now being discussed more widely as a practical way of adding new functions to automotive glass systems. That?s why S-LEC?s multi-layer extrusion technology and the S-LEC® ?Function-by-layer? concept (where more functions are added than a normal interlayer) have become so important. These high performance technologies offer the possibilities for interlayer films that meet various market needs, ensuring a bright future.
Current Market Trend - Solar and Sound. The evolution of Sekisui high performance PVB interlayer film took another step forward with S-LEC® Sound and Solar Control Film (SSF). Previously, the individual functions of solar and sound protection were marketed separately, but now Sekisui has brought them together in one film. By using Multi-layer technology, Sekisui was able to combine these two most desirable functions to dramatically increase the comfort level inside the vehicle cabin.
Performance of S-LEC® SSF: Sound Reduction. A multi-layer construction was adopted with a low elastic special resin layer as a core (inner layer) for maximum acoustic performance, and normal PVB resin layers as outer layers for mechanical strength and handling ease just like normal PVB film. This is because Sekisui?s initial development results showed that a ?soft single layer? acoustic interlayer had some disadvantages in safety (penetration resistance) and material handling. The multi-layer solution offered a new way of achieving higher acoustical performance in automotive glazing. The new S-LEC® SSF interlayer maintains the same sound attenuation performance as current S-LEC® acoustic film (SAF).
Engine Noise. Noise is made when the vehicle is running and especially when it?s accelerating. This vibration is transmitted through each part of the vehicle, including the windshield. As a result, the windshield creates solid sound which people experience as noise (Booming Effect). This noise occurs mainly within a low frequency range of 100 to 500 Hz.
Sound (vibration) attenuation in the low frequency range is evaluated by the loss factor. The higher the loss factor, the higher the sound insulation performance. Loss factor is calculated by the mechanical impedance method (MIM) where continuous subtle vibration is applied on the center of a laminated glass test piece. It can be related to the Sound Transmission Loss of the glazing.
Shown in Figure 1a and 1b are the loss factors of normal PVB laminated glass, monolayer acoustic film (Sekisui prototype) laminate, and multi-layer acoustic film laminate. Based on these results, multi-layer acoustic interlayer has the best vibration reduction performance at any frequency and also at any temperature from 10 to 25 degrees C. With its excellent vibration reduction performance, multi-layer acoustic interlayer effectively reduces engine noise from the windshield.
Figure 1a Loss factor of acoustic and normal PVB laminates by frequency.
Figure 1b Loss factor of acoustic and normal PVB laminates by temperature.
Wind Noise. Wind noise is transmitted through glass parts, increasing interior noise level. This noise occurs mainly within a high frequency band of 1,000 to 5,000 Hz.
Figure 2 shows that Multi-layer acoustic PVB interlayer has the highest STL value in the coincidence dip range of 1,000 to 4,000 Hz. Therefore, high frequency sounds like wind noise are more effectively blocked by multi-layer SAF or SSF.
Figure 2 Sound transmission loss of different laminated glasses.
Performance of S-LEC® SSF : Solar Control. Figure 3 shows spectrum curves of different glass/PVB compositions. Compared with a normal clear PVB laminate, S-LEC® Solar Control film (SCF) reduces incoming solar energy effectively, while retaining enough visible light transmission. This leads to a reduction in the dashboard temperature of 10oC compared with a normal PVB laminate. The new S-LEC® SSF interlayer maintains the same solar control performance as current SCF.
Figure 3 Transmission spectrum of solar control interlayer.
One way to evaluate passenger comfort is by calculating the thermal sensation to human skin when heated by solar energy (IR: Infrared, See Figure 3). Laminated windows with SSF can more effectively protect passengers from skin sensation than normal PVB laminates, making SSF a superior choice for laminated side windows and sunroofs.
Regarding absorption and reflection, outside wind or airflow takes the heat away from the glass. When a vehicle reaches a speed of 50km/h, heat energy gain for both absorbing and reflecting technologies is almost the same. Moreover, in a hot season, when the heated interior radiates infrared energy back towards the glass, vehicle glazing with a metal coating layer will retain the heat energy inside the cabin, whereas glass with SSF (absorbing type) re-radiates most of the absorbed energy towards the outside. Which means when the vehicle is moving, temperature is lower with a SSF laminate (Figure 4).
Figure 4 In-Vehicle Test Result (SCF vs. Heat Reflective PET).
SSF laminate also offers radio wave transparency. Cellular phones (1.9 GHz band) are an integral part of our lifestyle and ETC (Electronic Toll Collection System, 5.8GHz band) is a key technology in the development of ITS (Intelligent Traffic Systems) to reduce traffic congestion. Unlike metal-coated glass systems, SSF has no EM (electromagnetic wave) shielding effects working just like normal PVB, whereas a metal-coating system is considered an EM shielding material.
Recognised in the Marketplace. Sound and solar control functions are already proven in automotive applications. Solar Control interlayer is used by Toyota, Nissan and other European OEs, as well as by train manufacturers for air conditioning efficiency and passenger comfort. Alongside this, Acoustic interlayer has long been used for architectural applications like airport buildings or hotels, and is now being used in the automotive sector by European manufacturers like Renault. In addition, some USA and Japanese car manufacturers are currently evaluating this technology for use in future models. But now, with the new combined acoustic and solar protection film (SSF) Sekisui has taken another step towards the ultimate in driver comfort. Currently the automotive industry is showing a strong interest in this new technology.
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Photos: Sekisui
Last review: April, 2008 |
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