What is Polymethyl Methacrylate?
Polymethyl methacrylate, or PMMA, is a transparent organic polymer that is used as an alternative to glass. It is a rigid plastic that can find its application in a variety of industries. This synthetic resin is formed by the polymerization of methyl methacrylate.
Also referred to as plexiglass or acrylic glass, PMMA is used because it is easy to shape, tough and cost-effective. It has the ability to keep a light beam reflected within the surface and is also resistant to UV radiation. Acrylic glass can be used in a variety of products, including car windows, aquariums, screens of digital devices etc.
Polymethyl Methacrylate Structure
PMMA is formed by the free radical polymerization of monomer methyl methacrylate. The polymethyl methacrylate structure is a vinyl polymer which is an ester of methacrylic acid (CH2=C[CH3]CO2H).
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The pendant CH3 groups hinder the crystalline packing of the polymer chains. Since they are not allowed to rotate freely around the C-C bond, the resulting structure is quite rigid.
Production of PMMA
It is produced from propylene which is derived from the refining of crude oil. The process of formation of methyl methacrylate polymer involves the following steps:
Propylene reacts with benzene to form isopropylbenzene or cumene.
Cumene gets oxidized to form cumene hydroperoxide.
This reacts with an acid to form acetone.
Acetone forms methyl methacrylate (CH2=C[CH3]CO2CH3) in liquid form.
The polymerization of this compound in the presence of free-radical initiators forms PMMA in solid form.
Polymethyl Methacrylate Uses
Acrylic plastic or PMMA finds its application in a variety of industries due to its properties, easy processing and cost-effectiveness. PMMA is processed by injection molding, compression molding, extrusion or casting.
The extensive polymethyl methacrylate uses are a result of its advantageous properties and adaptability. This transparent plastic is used in a lot of markets. Some of the most common applications of PMMA are discussed below:
Glass Substitute
Acrylic glass is used as a shatterproof alternative for windows and skylights. It is also commonly used in aquariums and aircraft canopies. A lot of hockey rinks also use PMMA. Illuminated sign boards that display advertisements or directions are also usually made up of PMMA.
Construction and Design
Windows, doors, panels, canopies etc., all use polymethyl methacrylate due to its excellent properties such as heat insulation and light transmission. The polymer may also be used in the construction of sinks, baths, knobs or tap tops.
Automobile Industry
One of the most important industries that require PMMA is the transportation and automobile industries. From car windows to windshields, acrylic sheets can be found in a lot of spaces. It is used in the manufacturing of various automotive parts. The aviation and marine industry also require this polymer. Car indicator covers and panels are also made using plexiglass.
Healthcare Industry
PMMA polymer is also known as bone cement in the healthcare industry. It is used by orthopaedic surgeons for procedures like joint replacement or treating bone damages. It can also be used to fill in the gaps between bones. Optical fibres used for endoscopy also consist of PMMA.
Cosmetic Usage
PMMA has also found its usage in various beauty products and injectables. It is used in cosmetic procedures that treat ace, facial lines, wrinkles etc.
Lamps and Lighting
The light-emitting potential, transparency and other such properties allow PMMA to be used in LED lights and lamps. You can find PMMA being used in street and traffic lights. It is manufactured in various colour options, which adds to its usability in lamps and other lighting devices.
Electronic Devices
Acrylic glass can be used in the display of various electronic equipment, including tv screens, laptops and smartphones. This is due to its properties, such as transmittance and high optical clarity.
Solar Devices
The application of polymethyl methacrylate PMMA in solar panels is a result of its UV stability and light transmission ability. It can also be used in the construction of greenhouses, aquariums and marine centres.
Other products where this polymer finds its application include paint, furniture and
optical fibres used for telecommunication.
Advantages of PMMA
PMMA has several advantages over other polymers like polycarbonate (PC) and polystyrene etc. It doesn’t scratch easily or yellow over time. PMMA is used as an alternative to other transparent polymers in situations where extreme strength is not required.
Some of the advantages of PMMA include:
Economical
Resistance to weathering
Various colouring options
Tensile strength
Easy to process and handle
Versatility
Biocompatibility
UV Stability
Durability
Transmittance and better optical clarity
Recyclable
Polishability
BPA-free, non-toxic
FAQs on Polymethyl Methacrylate
1. What are Some of the Drawbacks of Using PMMA?
Ans: PMMA is not as strong or resistant as other synthetic polymers. They are more likely to undergo distortion during construction. Some of the common limitations of polymethyl methacrylate include:
Low impact strength
Low heat and chemical resistance
Known to crack under high load
Poor solvent and fatigue resistance
May scratch easily in comparison to glass
These disadvantages have to be overcome by manufacturers and retailers before using PMMA to maximize its performance. This is done by modifying the polymer using a variety of techniques.
2. What are the Various Modifications that are Made before PMMA is Used Commercially?
Ans: PMMA, which in its unmodified state can not withstand high impact force or scratches like glass, can be modified using a variety of additives. These make the polymer less brittle and improve its impact resistance. The PMMA structure can be modified with the following compounds:
Fillers are used to reduce the cost of the polymer and make it more economical.
Acrylate comonomers are used as stabilizers in polymers that have to undergo heat processing to prevent depolymerization.
Butyl acrylate can improve the impact strength of PMMA, while methacrylic acid can make the polymer suitable for use at higher temperatures.
Plasticizers are used to improve the mechanical and processing properties of the polymers, such as the glass transition temperature and elastic modulus.
The polymer can be used for decorative purposes with the usage of dyes.
