Blog

PMMA plastic, also known as polymethyl methacrylate, is a synthetic polymer with a wide range of applications in daily life. With many outstanding properties, PMMA plastic has become an indispensable part of various manufacturing sectors. Let's delve into the details of what PMMA plastic is, its structure, properties, and many essential facts about this synthetic polymer, together with EuroPlas. 

1. What is PMMA plastic?

PMMA plastic stands for Poly Methyl Methacrylate. It is a type of engineering plastic that is transparent, known for its flexibility and is used as a substitute for glass. When heated to high temperatures, the plastic softens into a liquid state. However, upon cooling, it can quickly solidify again.

Read more: What is compounding in polymer? Common types of polymer compounding 

PMMA plastic material is also known by other names such as plexiglass or Mica plastic. Depending on the intended use and economic considerations, you can choose the most suitable type of product.

What is PMMA plastic?

2. Structure of PMMA plastic

PMMA plastic is formed through the polymerization process of methyl methacrylate (MMA) monomers. The MMA monomer has a molecular formula of C5H8O2 or CH2=CCH3COOCH3. It has a fibrous molecular structure, arranged in a spatial network. This structure contributes to PMMA's high mechanical strength, high surface hardness, and excellent resistance to abrasion.

PMMA is a linear polymer, where MMA monomers are linked together through ester bonds. These ester bonds are highly durable and heat-resistant.

Structure of PMMA plastic

3. How is PMMA produced?

PMMA, also known as acrylic or plexiglass, is a thermoplastic polymer created by polymerizing methyl methacrylate (MMA). MMA is the monomer used in the production of PMMA. MMA is an organic compound with the chemical formula CH2=C(CH3)COOCH3. It is a colorless, odorless liquid. MMA is produced by the copolymerization of acryloyl chloride with methanol.

The polymerization of MMA can be accomplished using various methods, including:

• Thermal Polymerization: This is the most common method for creating PMMA. MMA is heated to high temperatures, typically around 100-150°C. At this temperature, MMA molecules start to combine with each other to form a polymer chain.
• Catalytic Polymerization: This method involves using a catalyst to initiate the polymerization process. The most common catalyst is benzoyl peroxide.
• Radiation Polymerization: This method utilizes ultraviolet or X-ray radiation to trigger the polymerization process.

How is PMMA produced?

4. PMMA plastic properties

PMMA plastic is widely used in various fields due to its distinctive advantages. Below are the prominent characteristics of PMMA:

• PMMA plastic is approximately 40% lighter than glass and more than 10 times stronger than regular glass.
• It exhibits resistance to abrasion, weathering conditions, as well as resistance to dilute acids, alkalis, salts, and organic solvents.
• PMMA polymer has a refractive index of 1.49, providing high light transmission. A PMMA sheet allows 92% of light to pass through, more than glass or other plastics.
• PMMA plastic has a low heat resistance, being able to withstand temperatures in the range of 60 to 80 degrees
• Celsius, which is a common characteristic of many plastics, and PMMA is no exception.
• It is resistant to ultraviolet radiation and has lower infrared transmission compared to glass.
• PMMA is unaffected by saltwater and alkaline chemicals.
• It possesses good electrical insulating properties, especially at low frequencies.
• However, PMMA is susceptible to damage and swelling when in contact with certain solvents such as H2O2, Acetone, Alcohol...
• PMMA is a tough, durable, and lightweight thermoplastic. The density of acrylic ranges from 1.17 to 1.20 g/cm3, which is less than half that of glass.
• It has excellent scratch resistance when compared to other transparent polymers like Polycarbonate but is less scratch-resistant than glass.
• PMMA has low moisture absorption and water absorption capabilities, ensuring products made from PMMA maintain good dimensional stability.

PMMA plastic properties

5. Some common types of PMMA in the market

Currently, PMMA is widely used as a substitute for glass, which is why it is often referred to as organic glass. Some common types of PMMA available in the market include:

• Taiwanese PMMA: This is the most common type of PMMA in Vietnam. Taiwanese PMMA offers good quality, high durability, and a wide range of colors.
• Chinese PMMA: Chinese PMMA is more cost-effective than Taiwanese PMMA but tends to have lower quality. Over time, Chinese PMMA may yellow and become cloudy.
• Korean PMMA: Korean PMMA boasts high quality, good durability, and attractive colors. However, it is typically more expensive than both Taiwanese and Chinese PMMA.
• Japanese PMMA: Japanese PMMA is of the highest quality with exceptional durability. However, it comes at a premium price.
• Transparent PMMA: This is the most common type of PMMA, used extensively in various applications.
• Colored PMMA: Colored PMMA is used to create visually appealing products with a variety of colors.
• Scratch-Resistant PMMA: Scratch-resistant PMMA is used in applications requiring high durability.
• Heat-Resistant PMMA: Heat-resistant PMMA is used in high-temperature applications.

Some common types of PMMA in the market

6. Recycling PMMA

Polymethyl methacrylate is a material with high biocompatibility and can be 100% recycled without biological degradation. PMMA is categorized as a plastic group 7.

However, the quality of recycled PMMA can be affected if the proportion of recycled materials is too high or if the recycled materials are contaminated. Therefore, recycling PMMA needs to be handled carefully to ensure the quality of the final product. There are two main methods for recycling PMMA:

• Pyrolysis Process: PMMA is heated to extremely high temperatures in an oxygen-free environment. This process breaks down PMMA into monomers, which are then used to produce new PMMA.
• Molecular Depolymerization Process: PMMA is depolymerized using molten lead. This process yields MMA monomers with a purity level of >98%.

Recycling PMMA

7. Comparing PMMA and PC

Both PMMA and PC are thermoplastic polymers, meaning they can be heated and reshaped multiple times without damage. They both have high durability and good impact resistance, and they also exhibit good weather resistance.
PMMA and PC are two types of thermoplastic polymers widely used in various applications. However, there are some notable differences between these two plastics.

• Transparency: PMMA is more transparent than PC. This makes PMMA a better choice for applications that require high transparency, such as safety goggles, sunglasses, and signage.
• Heat Resistance: PMMA has higher heat resistance than PC. This means PMMA can withstand higher temperatures without deforming or damage.
• Corrosion Resistance: PMMA has better corrosion resistance than PC. This makes PMMA a better choice for applications in harsh environments, such as the chemical industry.
• Cost: PMMA is generally more expensive than PC.

The choice between these plastics depends on the specific requirements of the application. If transparency, heat resistance, or corrosion resistance are critical factors, then PMMA is a better choice. If cost is a significant consideration, then PC is a better option.

Comparing PMMA and PC

8. Frequently asked questions

8.1. Is PMMA toxic?

PMMA is not considered toxic. It is considered safe for humans and animals. However, if PMMA is burned, it can produce harmful substances such as smoke and gas.

8.2. What are the advantages of PMMA?

• High transparency, almost equivalent to glass.
• High durability and good impact resistance.
• Excellent resistance to various chemicals.
• Can withstand temperatures up to 120°C.
• Easily processed using various methods.

8.3. What are the disadvantages of PMMA?

• Lower durability compared to glass, susceptible to scratching.
• Higher cost compared to glass.

8.4. What are the processing conditions for injection molding and extrusion of PMMA?

Injection Molding:

• Melting Temperature: 200-250°C
• Mold Temperature: 40-80°C
• High injection pressure is necessary due to its poor flow characteristics. Slow injection may be required for precise flow.
• Stress relief can be achieved by annealing at 80°C.

Extrusion:

• Extrusion Temperature: 180-250°C.
• It is advisable to use a vented screw with an L/D ratio of 20-30 to remove air.