Detailed explanation of natural fir resin glue
At present. In China's optical industry, the adhesive used mainly falls into four categories. Only one type of adhesive is introduced here, and the other three types will be introduced on Hangzhou Datian website www.hzdtsk.com/about22/1.html.
Fir resin glue is commonly known as hot glue. It is made from the sap excreted by fir plants in the Pinaceae family and purified. The natural fir resin is usually brittle, so (4-I2)% of the cut volume is often increased when it is prepared, such as flaxseed oil, tung oil, vaseline oil and walnut kernel oil. Flaxseed seed fairy is the best in steaming, because its refractive index and specific gravity are near Chengyi gum with natural cold clothes, and its mutual solubility is good.
Among fir resin adhesives, the natural Canadian gum has a long history of application and good functions. I successfully trial produced Dongling Lengshan Optical Resin Glue and Horie Lengshan Optical Resin Glue respectively by Nanjing and Chengdu Academy of Forestry Sciences in the 1960s and 1960s. Its function is to be near Canada Glue. Now I have added this glue to my generation.
Abies resin adhesive has excellent light transmittance and certain drying strength; Near the refractive index (nD=1,52-1.54) and K9 glass, it can be kept clear for a long time, and the volume is reduced by 5-6% when setting, so the bonding stress is small. The use of simple adhesive is simple, non-toxic and harmless. Therefore, it is a kind of old glue widely used. Usually used for gluing lens, shuttle mirror, filter, dial, reticle and other indoor instruments.
However, fir resin adhesive has low mechanical strength and is not suitable for gluing optical elements in outdoor optical instruments. The function of heat resistance and cold resistance is poor (- 40 --+40 ℃), the temperature is slightly high, the adhesive layer becomes soft, and the glued parts are prone to displacement and intermediate error. When the temperature is low, the adhesive is suddenly brittle, and simple cracking causes degumming; In the near ultraviolet region, the spectrum has significant absorption, which cannot be used for bonding of ultraviolet optical parts.
There are three kinds of fir resin glue: solid pure cold shirt resin glue, modified fir resin glue and liquid fir tree energy glue.
The softening temperature of solid fir resin glue is 65-72 ℃. When the temperature rises, the viscosity decreases, and the fluidity increases. If it continues to be hot, the glue layer will become brittle. Pay attention to the temperature control when using it. Liquid cold coat resin glue is made by dissolving it in solvent, which can be used for gluing large flat optical parts.
In order to reduce the deformation of parts caused by bonding stress, when using fir resin glue to glue the lens, glue with different hardness should be selected according to the shape of the parts. The low temperature resistance of soft glue is better than that of hard glue. If the diameter of the part is large and the thickness difference between the middle and the side line is large, soft adhesive shall be used. For parts with small diameter and radius of curvature, difficult glue shall be used.
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