Main categories of optical plastics and raw material applications

What is optical plastic?

Generally divided into thermoplastic and thermosetting plastics. Thermoplastic refers to plastic that can be repeatedly heated and still plasticized. The optical plastic is mostly thermoplastic.

Commonly used materials

Polymethylmethacrylate (PMMa), polystyrene (PS), polycarbonate (PC), and the like.

Thermosetting plastic means that the synthetic resin used is softened at the initial stage of heating and has plasticity. When heating is continued, the shape is fixed and does not change with the chemical reaction.

Commonly used materials

Allyl diglycol carbonate resin ophthalmic lens.

Epoxy optical plastics are all thermoset plastics.

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Main optical plastic

1, polymethyl methacrylate

Referred to as PMMa, the molar amount is about 500,000 - 1 million, (the molar amount has a great influence on the performance of the polymer) nd = 1.491, the dispersion coefficient Vd = 57.2, is the "Wang Hao" material, the transmittance is about 92%, after accelerated aging, the 240H transmittance can still reach 92%, and after 10 years of outdoor use, it only drops to 88%, and can transmit ultraviolet light with a wavelength above 270nm. PMMa can transmit X-rays and Y-rays, and its sheets can transmit alpha rays and beta rays, but absorb neutron rays.

PMMa resistant to inorganic acid decontamination liquid, excellent performance of oil and weak base, medium resistant to concentrated inorganic acid, not resistant to alcohol, ketone, soluble in aromatic hydrocarbons, chlorinated hydrocarbon organic solvent, strong alkali and warm NaOH, KOH Erosion, does not react with the developer.

PMMa has excellent weather resistance and has been exposed to sunlight for many years. Its transparency and color change are small.

PMMa is currently used in the manufacture of cameras, camcorders, projectors, disc read heads, and aspherical lenses and mirrors in military fire control and guidance systems. It is also used to make Fresnel lenses, microlens arrays, Contact lenses, optical fibers, optical disc substrates and other parts.

2. Copolymer of styrene and acrylate

Abbreviation: NaS. A copolymer of 70% styrene and 30% acrylate, which is superior to polystyrene in performance. The transmittance is up to 90%, the refractive index nd can vary from 1.533 to 1.567, and vd = 35, which can be used as a second material for positive color difference, but it is generally only used as a thin lens.

3, polycarbonate

Referred to as PC. A thermoplastic with excellent comprehensive properties, good heat resistance, cold resistance, high mechanical strength over a wide temperature range (-135°C---+120°C), good dimensional stability, and elevated temperature The linear size of the material increases by 0.07% at 105 ° C, has high impact strength, good ductility, uniform molding shrinkage, low water absorption, soaking 24H in water only gains 0.13%, but it is not easy to mechanically process, injection molding Molding is the most common method.

4, polystyrene

PS for short, this is a flint thermoplastic optical plastic. Although its anti-ultraviolet radiation performance and scratch resistance are not as good as PMMa, its refractive index is high, nd=1.59-1.660, Abbe's coefficient is small Vd=30.8, so When combined with PMMa, it can be an achromatic lens that corrects the F and C lines. The correction of the secondary spectrum is generally better than the achromatic lens of the glass.

Its transmittance is 88%, its birefringence is large, and polystyrene tends to turn yellow under the action of sunlight.

PS can be freely colored, odorless, tasteless, non-toxic, no mold, and only 0.02% hygroscopic.

PS heat distortion temperature is 70--98 °C, which is related to the formulation and post-treatment. Its maximum continuous use temperature is 60--80 °C, the molding shrinkage is 0.45%, and its parts can be annealed to reduce internal stress. Mechanical strength, no heat distortion temperature, the annealing resolution is generally 5-6 ° C lower than the actual heat distortion temperature. The thermal conductivity of PS does not change with temperature, so it can be used as a good frozen insulation material.

The specific heat capacity of PS has a significant change, which is a lower specific heat in plastic. In high vacuum and in the 330--380 ° C, it will violently degrade and release 43% of volatiles, 41% of styrene, 2%. It was toluene and the remaining dimeric trimeric tetramer and polymer were 57%.

PS can withstand certain mineral oils, organic acids, alkalis, salts, low-energy alcohols and their aqueous solutions. It is softened by many ketones, higher fatty esters, etc., soluble in aromatic hydrocarbons such as benzene, toluene, ethylbenzene and styrene. Wait.

PS is one of the most radiation-tolerant polymers, and a large amount of radiant energy must be applied to change the properties.

PS is one of the varieties of easy-to-shape processing in resin. It has the characteristics of large difference in molding temperature and decomposition temperature, low melt viscosity and stable dimensional. It can be molded and used in injection molding, but its brittleness is larger than other optical plastics. Therefore, it is easy to crack. When cutting the gate, care should be taken to prevent cracking. It can also be machined with general metal or wood processing tools such as drilling, sawing, cutting, etc.

The PS is used to replicate the grating assembly in addition to the lens in which the PMMa is achromatic.

In order to improve the performance of PS, some improved varieties such as 70% polystyrene and 30% copolymerized with methyl acrylate were used to form a new optical plastic NaS.

Another copolymer, acrylonitrile-styrene, is called SaN. It is mainly used in engineering plastics. It is mainly used as a window in optics, which basically maintains the transparency of PS, but still has a tendency to yellow, nd=1.567 The maximum use temperature is 75--90 ° C, the heat distortion temperature is 82--105 ° C, the linear expansion coefficient (6.5-6.7) * 10-5 K-1, and the density is 1.06 kg/m3---1.08 kg/m3.

The aluminum housing is very suitable to use in cold environment.

The gear hard is 48-52 HRC.

The motor power is high.Axis use chromium manganese titanium.

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