Everything You Need To Know About Acrylic (PMMA)
Learn about this material, how it is fabricated, uses, and advantages.
This article will explain what Acrylic (PMMA) is, how it is made, the different uses of acrylic, advantages of acrylic, and disadvantages of acrylic.
The following image is an example of PMMA before it is manufactured into a new product:
Plastic raw material.
Image Credit: Pixparts/Shutterstock.com
Acrylic (PMMA) is a transparent and rigid plastic often used instead of glass in products such as shatterproof windows, illuminated signs, skylights, and aircraft canopies. PMMA belongs to the important acrylic family of resins. Acrylic is chemically known as Polymethyl methacrylate (PMMA) and is a synthetic resin created from the polymerization of methyl methacrylate.
Polymethyl methacrylate (PMMA) is also known as acrylic, acrylic glass, and by the trade names and brands Crylux, Plexiglas, Acrylite, Perclax, Astariglas, Lucite, and Perspex, among others. Polymethyl methacrylate (PMMA) is often used in sheet form as a lightweight or shatter-resistant alternative to glass. PMMA can also be used as a casting resin and in inks, and coatings. PMMA is part of a group of materials called engineering plastics.
Polymethyl methacrylate is made through polymerization, as it is one of the synthetic polymers. First, methyl methacrylate is put in a mold with a catalyst added to speed up the process. Because of this polymerization process, PMMA can be shaped into many forms, such as sheets, resins, blocks, and beads. Acrylic glue can also help soften the pieces of PMMA and weld them together.
PMMA is easily manipulated in different ways. It can be bonded to other materials to help enhance its properties. Through thermoforming, it is flexible when heated and solidified when cooled. It can be sized appropriately using a saw or laser cutting. If polished, scratches are removed from the surface, helping to maintain its integrity.
The two main types of acrylic plastic are cast acrylic and extruded acrylic. Cast acrylic is more expensive to produce but offers better strength, durability, clarity, thermoform range, and stability than extruded acrylic. Cast acrylic has superior chemical resistance and durability and is easily colored and shaped in the manufacturing process. Casting acrylic also provides a wide range of thicknesses. Extruded acrylic is more economical than cast acrylic and provides a more consistent, machinable acrylic than cast acrylic (the tradeoff being reduced strength). Extruded acrylic is easy to work and machine and is an excellent substitute for glass panes in application.
There are other acrylic types based on factors besides manufacturing technique, such as grades of acrylic plastic that offer unique heat, light, impact strength, flow rate, or release characteristics for specific engineering applications. These grades can also come coated to improve their scratch resistance, fogging properties, glare, and other downsides. Acrylic is also widely popular as paint, where pigment particles are suspended in an acrylic polymer emulsion. When dried, the acrylic is resistant to water, scratches, cracking, and UV radiation and leaves an attractive glossy finish. The paint can also act as a protective coating, such as in exterior wall paint.
Common uses of Acrylic (PMMA) include: automotive lights, home appliances, lenses for glasses, shatter-resistant panels for windows, skylights, bulletproof security barriers, signs and displays, LCD screens, bathtubs, furniture, and acrylic nails, and many other applications.
PMMA is also used for coating polymers based on MMA and offers stability against environmental conditions with reduced VOC emission. Methacrylate polymers are used broadly in medical and dental applications where purity and strength are critical to performance. Here are some other uses of polymethyl methacrylate.
PMMA is used as an inexpensive alternative to polycarbonate when tensile strength, flexural strength, polishability, transparency, and UV tolerance are most important. PMMA also does not contain the potentially harmful bisphenol-A subunits found in polycarbonate and is a better choice for laser cutting. It is often favored because of its moderate properties, easy handling and processing, and low cost.
Non-modified PMMA is brittle when under load, especially under an impact force, and is more prone to scratching than conventional inorganic glass. Still, modified PMMA can sometimes achieve high scratch and impact resistance.
PMMA has excellent mechanical properties and low toxicity. It is popular for hip-joint transplantations because of its inert properties and displays slow degradation. Therefore, manufacturing a polymer blend of polycaprolactone and PMMA produces a polymer material that is better suited for biomaterial applications.
- Home Improvement and Architecture: PMMA comes in handy for construction. It is often used for shatterproof skylights. It is also used for many shower and bath units. Many even prefer PMMA to ceramic tiles. In addition, PMMA can be found in many sound-resistant rooms, audio studios, and cars.
- Windows: Acrylic is a lighter, versatile material, which means it is easier to install than other options for windows, such as glass. Additionally, PMMA does not break easily, and even if a plexiglass window does fracture, it creates dull-edged pieces instead of sharp glass splinters, which is safer.
- DIY Projects: PMMA is an excellent material for DIY projects, whether for work or leisure. PMMA is easy to work with and safe, and it can be used in constructing art structures and various designs. Acrylic can be found in many coasters, DIY picture frames, and shelving units. In addition, it is an excellent protective and aesthetically pleasing table cover.
- Medical Technologies: PMMA has a reasonable degree of compatibility with human tissue. It is used to manufacture rigid intraocular lenses implanted in eyes when the original lens has been to treat cataracts. Acrylic bone cement is also widely used in orthopedics.
Acrylic is used so often because it has the same beneficial qualities as glass without the fragility issues. Acrylic glass has excellent optical properties, with the same refractive index as glass when in solid form. Designers can implement acrylic, thanks to its shatter-resistant qualities, in places where glass is too dangerous or would otherwise fail (such as submarine periscopes, airplane portholes, etc.). For example, the most common type of bulletproof glass is a single piece of ¼” thick acrylic known as monolithic acrylic. Acrylic also works well in plastic injection molding, allowing it to take virtually any shape a mold maker can create. The strength of acrylic glass, combined with its easy workability and machinability, makes it an excellent material overall and explains why it is used throughout consumer and commercial industries.
PMMA powder is often used for nail art, as seen in the image below:
Close up of the process of applying acrylic powder on the nails.
Image Credit: Michelle Aleksa/Shutterstock.com
Heat Deflection Temperature
95° C/ 203° F (@ 0.46 MPa/66 psi)
65 MPa/ 9400 psi
90 MPa/ 13000 psi
Polymethyl methacrylate has a melting point of 320°F and has a density range of 1.17-1.20 g/cm3. It experiences no reactions to an aqueous solution compared to other polymers and plastics, and it has high scratch resistance. If the surface of a product made from PMMA is compromised, it is often because of exposure to ester, aromatic or chlorinated hydrocarbons, or ketone chemicals.
Acrylic is a plastic—it is built out of monomers derived from petroleum. Glass is an amorphous, non-crystalline solid made primarily of silicon dioxides and other elements. While acrylic exhibits excellent optical clarity and refractive properties just as glass does, acrylic is much more impact resistant and will not shatter into dangerous pieces. Acrylic can be used in tension and in compression, while glass typically is only somewhat strong in compression as with other ceramic-like materials such as concrete or bricks.
Compared to glass, polymethyl methacrylate is 50% lighter, 90-92% clearer, more durable, and more affordable. PMMA is scratch resistant, while glass leans towards being delicate as it typically scratches and breaks easily. And when glass breaks, it shatters into many sharp shards. The sharp bits are both inconvenient and dangerous. However, acrylic is both scratch and shatter-resistant. It can hold its properties over a long period, even when exposed to UV rays and weather. Many use PMMA as a substitute for glass for these reasons.
Acrylic was invented in 1928 in several different laboratories by many chemists. Acrylic (PMMA) was first brought to market in 1933 by German Röhm & Haas AG and its partner Rohm and Haas Company under the trademark Plexiglas.
The advantages of polymethyl methacrylate are that it is easy to fabricate, lighter & stronger than glass, easy to shape, highly transparent, and easy to clean and maintain. It is considered an economical alternative to glass.
When PMMA is heated, it becomes malleable and can be molded into many different shapes. PMMA holds its formed shape as it cools down to be machined, drilled, or sawed. When it is shaped, molds can be made from wood or plastic, which is cost-effective. Because it is thermoplastic and softens under high temperatures, acrylic can be formed into virtually any shape.
Another advantage of using the synthetic polymer of PMMA in place of glass is that it is more durable and weighs 50% less than glass. Acrylic is less expensive while remaining ten times more impact-resistant than glass. It can be used over a broad temperature range and has superior weather resistance to glass and other forms of plastic. In addition, it will not shatter under a high impact, and if it does break, it fractures into large, dull-edged pieces.
Acrylic plastic stays transparent even as it ages, without excessive yellow tinting. The ability to remain transparent is essential for PMMA exposed to sunlight. As PMMA is more fade-resistant than other plastics, its light transmittance is equivalent to glass and has the same aesthetic appearance.
There are some rules about acrylic care and cleaning, but it is an easy material to maintain. When cleaning acrylic with slight blemishes and dirt, it is recommended to use a wet microfiber cloth and blot the material. Additionally, it’s essential to ensure particles and grit are entirely removed from the cleaning cloth, as accidentally rubbing rough dirt across the material can cause the PMMA to further scratch.
The disadvantages of using polymethyl methacrylate are poor impact resistance, wear and abrasion resistance, limited heat resistance (with its max resistance at about 80° C), and limited chemical resistance. It is also prone to attack by organic solvents, and cracking under load is possible.
Poly(methyl methacrylate) does not negatively affect human health. Although polymethyl methacrylate is being formed by polymerizing methyl methacrylate, which is an irritant and a possible carcinogen, PMMA is highly biocompatible and is often used in the medical field.
Polymethyl methacrylate is not toxic and is considered safe. It is rated as a low-hazard ingredient by the Cosmetics Database. Like most plastics, PMMA may be harmful if inhaled and may cause respiratory tract irritation. It may also be harmful if absorbed through the skin and can cause skin irritation. Again, like most plastics, it may also cause eye irritation and may be harmful if swallowed.
Acrylic does not contain bisphenol A (BPA). Some plastics will undergo hydrolysis reactions when in contact with water, releasing BPA which has been proven harmful to humans. Acrylic is a BPA-free substitute for clear plastics like polycarbonate and others that do release BPA when in contact with water.
The difference between PMMA and MMA is that PMMA is made from methyl acrylate. PMMA is a polymer of methyl methacrylate without any other substance. It is an amorphous and transparent polymer produced through free-radical polymerization.
Methyl methacrylate (MMA) is a monomer known as methacrylic acid and methyl ester. MMA is a primary building block for acrylic-based polymers and applications, including safety glazing, adhesives, exterior paints, vinyl impact modifiers, and illuminated light displays.
MMA is foundational for many acrylate polymers and is an essential comonomer in paint, coatings, and adhesives resin formulations. MMA elevates the Tg (glass transition) in free radical initiated copolymers and contributes durability, strength, transparency, and UV & abrasion resistance.
Photopolymer systems based on acrylate monomers are a mixture of prepolymers (polymers not completely polymerized) and photoinitiators that initiate because of emitting UV or any other kind of radiation polymerization reaction. As a result, the acrylate prepolymer becomes wholly polymerized.
Xometry offers acrylic (PMMA) sheet in a variety of sizes and material thickness and offers acrylic rod in different diameters and overall lengths, they can be found at Xometry Supplies.
This article presented what acrylic (PMMA) is, how it is made, the different types of acrylic, how acrylic it is used, the different features and properties of acrylic and it's disadvantages and advantages.
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