Usually, we use PMMA materials in our indoor and outdoor lamps, so today let's discuss its performance and application scenarios.

Polymethyl methacrylate (PMMA), commonly known as plexiglass, acrylic, etc., is a non-crystalline plastic copolymerized by MMA monomer and a small amount of acrylic esters. It has good transparency, optical properties, weather resistance, chemical resistance, impact resistance and aesthetics. It is a high-end material known as the "Queen of Plastics". Products include molding compounds, extruded plates and cast plates.

The polymers obtained by polymerization of acrylic acid and its esters are collectively referred to as acrylic resins, and the corresponding plastics are collectively referred to as polyacrylic plastics, among which polymethyl methacrylate is the most widely used. The abbreviation code of polymethyl methacrylate is PMMA, commonly known as plexiglass. It is the most excellent and affordable variety among synthetic transparent materials to date.

Main properties of PMMA

Polymethyl methacrylate is a rigid, hard, colorless and transparent material with a density of 1.18-1.19g/CM3, a low refractive index of about 1.49, a transmittance of 92%, and a haze of no more than 2%. It is a high-quality organic transparent material.

1. Mechanical properties of PMMA

Polymethyl methacrylate has good comprehensive mechanical properties and ranks among the top general plastics. Its tensile, bending and compression strengths are higher than those of polyolefins, polystyrene, polyvinyl chloride, etc. Its impact toughness is poor, but it is also slightly better than polystyrene. The tensile, bending and compression mechanical properties of cast bulk polymerized polymethyl methacrylate sheets (such as plexiglass sheets for aviation) are higher, reaching the level of engineering plastics such as polyamide and polycarbonate.

Generally speaking, the tensile strength of polymethyl methacrylate can reach 50-77MPa, and the bending strength can reach 90-130MPa. The upper limits of these performance data have reached or even exceeded some engineering plastics. Its elongation at break is only 2%-3%, so its mechanical properties are basically hard and brittle plastics, and it is notch sensitive and easy to crack under stress, but the fracture is not as sharp and jagged as polystyrene and ordinary inorganic glass. 40℃ is a secondary transition temperature, which is equivalent to the temperature at which the side methyl groups begin to move. When it exceeds 40℃, the toughness and ductility of the material are improved. The surface hardness of polymethyl methacrylate is low and it is easy to scratch.

The strength of polymethyl methacrylate is related to the stress action time. As the action time increases, the strength decreases. The mechanical properties of polymethyl methacrylate (oriented organic glass) after stretching orientation are significantly improved, and the notch sensitivity is also improved. The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104℃, the maximum continuous use temperature varies between 65℃-95℃ depending on the working conditions. The heat deformation temperature is about 96℃ (1.18MPa), and the Vicat softening point is about 113℃. The heat resistance can be improved by copolymerizing the monomer with methacrylate or diester-based ethylene glycol acrylate. The cold resistance of polymethyl methacrylate is also poor, and the brittle temperature is about 9.2℃. The thermal stability of polymethyl methacrylate is medium, better than polyvinyl chloride and polyoxymethylene, but not as good as polyolefins and polystyrene. The thermal decomposition temperature is slightly higher than 270℃, and its flow temperature is about 160℃, so it still has a wide melting processing temperature range. The thermal conductivity and specific heat capacity of polymethyl methacrylate are both at a medium level among plastics, which are 0.19W/CM.K and 1464J/Kg.K respectively

2. Electrical properties of PMMA

Because the main chain of polymethyl methacrylate contains polar methyl ester groups, its electrical properties are not as good as non-polar plastics such as polyolefins and polystyrene. The polarity of the methyl ester group is not too large, and polymethyl methacrylate still has good dielectric and electrical insulation properties. It is worth pointing out that polymethyl methacrylate and even the entire acrylic plastic have excellent arc resistance. Under the action of arc, no carbonized conductive path and arc track phenomenon will be generated on the surface. 20℃ is a secondary transition temperature, corresponding to the temperature at which the side methyl ester group starts to move. Below 20℃, the side methyl ester group is in a frozen state, and the electrical properties of the material will be improved compared to above 20℃.

3. PMMA's resistance to chemical reagents and solvents

Polymethyl methacrylate can resist dilute inorganic acids, but concentrated inorganic acids can corrode it. It can resist alkalis, but warm sodium hydroxide and potassium hydroxide can corrode it. It can resist salts and oils, and resist aliphatic hydrocarbons. It is insoluble in water, methanol, glycerin, etc., but it can absorb alcohol swelling and produce stress cracking. It is not resistant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8 (J/CM3)1/2. It can be dissolved in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene, etc. It can also be dissolved in vinyl acetate and acetone. Polymethyl methacrylate has good resistance to gases such as ozone and sulfur dioxide.

4. Weather resistance of PMMA

Polymethyl methacrylate has excellent atmospheric aging resistance. After 4 years of natural aging test, its sample has changed in weight, slightly decreased in tensile strength and light transmittance, slightly yellowed in color, and significantly decreased in silver streak resistance. The impact strength is slightly improved, and other physical properties are almost unchanged.

5. Combustibility of PMMA

Polymethyl methacrylate is very easy to burn, and the limited oxygen index is only 17.3.

Application Areas

01 Lighting and construction industry

The high light transmittance and weather resistance of PMMA make it an ideal glass substitute in the construction industry. It is widely used in the manufacture of windows, skylights, sound insulation boards and decorative panels. The exterior wall panels made of PMMA are not only light and easy to install, but also can withstand the influence of bad weather and maintain long-term stable performance. In addition, PMMA panels can be made into various textures and colors through special processes to adapt to different architectural styles and design requirements. In terms of indoor lighting, the high light transmittance of PMMA makes it an ideal material for manufacturing lighting equipment, such as outdoor lamps and indoor decorative lamps. These lighting equipment can not only provide efficient lighting effects, but also ensure beauty and safety.

02 Automotive industry

PMMA is widely used to manufacture car headlights and taillight covers. These parts not only need to provide good lighting effects, but also need to be able to withstand the impact of flying stones during high-speed driving. In addition to the lighting system, the transparency and glossiness of interior parts such as dashboards, control panels and decorative strips can enhance the beauty of the car interior. At the same time, PMMA's chemical resistance can resist various liquids and detergents that may be exposed in daily use.

In addition, PMMA's weather resistance and aging resistance make it an ideal material for automotive exterior parts, such as sunroofs and side windows for automobiles. These parts need to maintain good transparency and mechanical properties under various climatic conditions.

03 Medical Devices

In the medical device industry, PMMA is widely used due to its biocompatibility, transparency, and chemical resistance. One of the main uses of PMMA is as a manufacturing material for artificial joints and bones. Due to its high strength and wear resistance, PMMA is able to provide support and wear resistance similar to natural bones. Similarly, the transparency and aesthetics required for dental trays and dental braces in the dental field can make PMMA an ideal dental restoration material, and chemical resistance can resist corrosion in the oral environment.

In addition, the biocompatibility and stability of PMMA make it an ideal material for drug delivery systems and biosensors. In these applications, PMMA can be designed into specific shapes and structures to accommodate different drug release and sensing needs.

In addition, the biocompatibility and stability of PMMA make it an ideal material for drug delivery systems and biosensors. In these applications, PMMA can be designed into specific shapes and structures to accommodate different drug release and sensing needs.

Conclusion

PMMA, as a high-performance engineering plastic, plays an important role in many industries. With the continuous advancement of synthesis technology and the continuous expansion of application fields, the market prospects of PMMA are broad. In the future, the PMMA industry needs to pay attention to the development trend of environmental protection and energy conservation, and strengthen technological innovation to meet the market demand for high-performance PMMA products.

Thanks for reading:)

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