Optical silicone is a two-component ultra-transparent liquid silicone raw material with very good optical properties and flame retardant performance. The color remains stable and the optical clarity remains unchanged under long-term harsh environments, such as under high temperature or UV radiation. In addition, the excellent processing properties enable the manufacture of complex or micro-structured optical parts with tight tolerances, which opens up new possibilities for cutting-edge technologies in LED high-powered automotive lighting, indoor and outdoor LED lighting and electronics.
As China top manufacturer of silicone optics, here we'll introduce to you about the properties and strength of LSR molding silicon optics.
Optical lenses should try spread as much lights as possible, if light is absorbed, the light transmission efficiency will be affected. High transparency is the basic requirements for lens material. PC transmittance is around 87%, due to the poor optical performance, it has been eliminated by the optical products industry that requires high transparency. PMMA transmittance is about 92%, the most widely used optical material.
While LSR optical silicone transmittance can reach to 96%, it can greatly reduce the impact of color distortion, reflectivity and clarity on visual perception caused by transparency during use of the optical silicon lens.
The residual stress inside the molded product can easily cause lens deformation and cracking, leading to the birefringence phenomenon of the optical products, which directly affects the optical performance, and the safety is also difficult to guarantee.
The molding process of PC and PMMA thermoplastic compounds is a physical change, the linear molecular chain is under the influence of the injection flow speed and the temperature change off the molding gradient, the stretched and compressed molecular chain is quickly cooled and shaped, and it's in an unstable arrangement state. It cannot be restored to the original free and stable state. Residual stress occurs.
The two-component optical silicone is formed by thermochemical reaction. It is injected into the high-temperature mold at low temperature. When the material reaches a certain high temperature, the cross-linking reaction between the molecular chains will gradually occur. There is basically no cross-linking reaction between the molecular chains during the entire curing and silicone molding processes. There is almost no residual stress in silicone optics.
When light enters another medium from one medium, when its propagation direction is not perpendicular to the interface between the two media, the propagation direction at the interface changes. The refractive index is related to the wavelength of light. The refractive index of the lens is smaller when the wavelength is longer, and the refractive index of the lens is larger when the wavelength is shorter. When the light is refracted through the lens, the wavelength of each color light is different, and the degree of refraction is also different. After refraction, it decomposes into dispersion. The refractive index of the lens material is large, and the degree of refraction after the light passes through is large.
Dispersion is an important indicator to measure the sharpness of lens imaging. The greater the dispersion, the worse the sharpness of its imaging. In terms of refractive index, PC is about 1.526, PMMA is about 1.592, and glass is about 1.523. They all have a certain degree of dispersion, which is easy to cause visual fatigue.
Wacker optical silicone is 1.41, which can maintain a stable low refractive index in high and low temperature environments and a variety of wavelengths of light, with a low degree of dispersion, and high-definition imaging effects can be obtained.
PC and PMMA are thermoplastic materials that can be repeatedly heated and softened and cooled to harden. During the molding process, the product shrinks unevenly due to changes in local temperature and thickness, which leads to shrinkage stress in the lens product. When the product is used, the environmental temperature change affects it mover obviously.
Optical silicone material is a thermosetting material, and there is no significant change after heating after molding. The molding is thermal reaction molding, and the shrinkage during the molding process is balanced. The injection molding process can be used to achieve mass production of molded silicon lenses with fine structures.
Another major advantage of silicone elastomer is their low density. The silicon lens made from it are much lighter than glass parts of the same size, and have a slightly lower density than PC and PMMA. The relative density of PC is generally about 1.2g/cm3, PMMA is generally 1.18g/cm3, and LSR optical silicone is 1.12g/cm3.
LSR silicone optics can reduce the weight-to-volume ratio of the finished product under certain conditions of guaranteed function, which is conducive to the lighter weight of the product.
The thermal deformation temperature of PMMA is about 90 degrees, and that of PC is about 130 degrees. Higher temperatures will cause lens deformation and dimensional instability, which will affect the life of the product.
The organic optical silicone chain is composed of Si-O bonds, the bond energy is 422~494KJ/mol, and the CC bond energy of the plastic polymer chain is 360 KJ/mol. The higher bond energy determines its high temperature resistance. At the same time, Si The unique flexible structure of the -O main chain allows it to maintain good flexibility at low temperatures.
Silicone optics has good thermal stability and can maintain long-lasting elasticity at low temperatures without using plasticizers. They can be used at -40~200°C for a long time, maintaining dimensional stability, and having excellent mechanical and optical properties.
PC and PMMA will gradually turn yellow when exposed to heat, artificial or natural light sources, or ultraviolet radiation, which will seriously affect their use.
Optical silicone is extremely resistant to oxygen or ozone. They will not be affected by long-term exposure to visible light and ultraviolet radiation. Unlike organic plastics, they will not turn yellow. WACKER's new optical silicone, it can maintain crystal-like transparency even under long-term load.
In addition, the silicone optics does not absorb water, has excellent hydrophobicity, and has better anti-fingerprint and anti-fouling ability than PC or PMMA, which also brings convenience to users.
Yejia Silicone, as a silicone molding products manufacturer in the LSR silicone molding, plastic+ silicone LSR overmolding process has more than 10 years of production and manufacturing experience. We've set up class 100,000 clean production workshop for silicone optics. For now, our factory has 9 sets ARBURG LSR injection molding machines. As to materials, the main models we're using are Dow MS-1001& MS-4002, Momentive LSR7180, Wacker LR 7601 and Doneson DSA-7170&DSA-7180.
If you're looking for custom silicone optics supplier, welcome to contact us.