What is polycarbonate? All about polycarbonate.

Learn all about this material and its different types, uses, benefits, limitations, and toxicity.

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What is polycarbonate?

Polycarbonate is a term for a class of thermoplastic polymers characterized by the presence of functional carbonate groups in their chemical matrix. Due to their unique properties, such as high strength, hardness and, in some cases, excellent clarity, these materials are widely used in the fields of engineering and technology. Polycarbonates can be efficiently machined, formed and thermally shaped, making them extremely versatile materials. They are used in the production of components with high functional requirements, including polycarbonate skylights, which provide unparalleled clarity. It is worth noting that polycarbonates may contain bisphenol A (BPA) as a precursor monomer, which is important when considering their use in the context of health and safety. They are usually produced in sheet form, which further expands their range of applications in various fields of engineering and architecture.

Polycarbonate, as a thermoplastic, is ubiquitous in many industrial sectors due to its unique properties and wide application. It is a key material in the production of glasses, medical devices, protective equipment, automotive components, data carriers such as DVDs and Blu-Rays, as well as skylights and roof hatches. Thanks to its natural transparency as an amorphous thermoplastic, polycarbonate provides light transmission comparable to glass while maintaining exceptional impact resistance, superior to many traditionally used plastics.

Its flexibility allows it to be shaped at room temperature without the risk of cracking or breaking, as well as reformed without the need for heating, which gives polycarbonate its characteristic amorphous properties. The “thermoplastic” aspect refers to the ability of polycarbonate to turn into a liquid state at its melting point, which enables easy molding and injection recycling.

Polycarbonates are synthesized by polymerization of bisphenol A (C15H16O2) and phosgene (COCl2), melt at 260–320°C and remain functional over a wide temperature range. Their impact resistance is almost twice as high as that of the closest analogues, such as ABS and PVC. Due to their higher coefficient of thermal expansion than metals such as steel and aluminum, this needs to be taken into account when using them in complex structures.

With a tensile strength of 8500 psi, the material exhibits minimal shrinkage for precision machining, including traditional drilling, sawing, and milling methods. Polycarbonate can be easily formed at room temperature, and thermoforming provides an economical way to shape polycarbonate sheets, especially for medium to large parts in limited production runs.

The amorphous nature of polycarbonate, meaning the lack of an ordered crystal structure, affects the way the material softens – gradually and over a wide range of temperatures. As a thermoplastic, polycarbonate is hygroscopic, requiring the removal of trapped moisture before molding, typically by heating the material in an oven.

The chemical resistance of polycarbonate is variable and depends on many factors, including exposure time and temperature. Although it is resistant to many mineral acids, alcohols and mild soaps, contact with certain solvents, such as toluene and acetone, can lead to damage. Solutions such as blending with polyester or ABS can improve its properties, including chemical resistance and ductility.

Polycarbonate Material Manufacturing Process

The process of manufacturing a polycarbonate material begins with a chemical reaction between bisphenol A (BPA) and phosgene (COCl2). In the first step of this synthesis, bisphenol A is treated with sodium hydroxide, which leads to the deprotonation of its hydroxyl groups, forming activated phenoxyl species.

Then, these activated phenoxyls react with phosgene, resulting in the formation of chloroformats. These chloroformats are attacked by successive phenoxyl molecules, which leads to successive polymerization and the formation of polycarbonate chains. This process is responsible for the production of about one billion kilograms of polycarbonate per year, which highlights its industrial importance.

Other diols than bisphenol A, such as bis(4-hydroxyphenyl)cyclohexane and dihydroxybenzophenone, were also experimented with to modify the properties of the final product. The use of cyclohexane as a comonomer reduces the crystallization tendency of the BPA-based material, thus increasing its usefulness in a variety of applications. Additionally, the use of tetrabromobisphenol A is intended to improve the flame retardant properties of polycarbonate, which is crucial in many engineering and construction applications.

Availability of polycarbonate

In today’s plastics market, polycarbonate, originally developed in the mid-20th century by GE and Bayer, is now offered by a wide range of manufacturers, each introducing their own unique formulations and production technologies. Thanks to continuous innovation, different types of polycarbonate are available, each designed to meet specific technical and application requirements.

Below is a table with information about the different varieties of polycarbonate and their applications:

Polycarbonate Type	Description	Applications
Clear GP sheet	A clear polycarbonate sheet designed for glazing and industrial applications, offering protection against vandalism and intentional cracking. It has an impact force 250 times that of glass and 30 times that of acrylic sheets.	Facility protection, industrial glazing, protection against vandalism.
Clear SL sheet	UV resistance polycarbonate sheet, designed to survive in violent environments, providing extended life and resistance to color change. It provides UV protection on both sides of the sheet.	Outdoor applications exposed to UV radiation, such as canopies, exterior glazing, protection of materials against aging.
Polycarbonate Mirror Sheet	A versatile sheet with a mirror effect, offering heat resistance, excellent impact strength, dimensional stability and UV.	Automotive industry, security, bidirectional mirrors, traditional mirrors in high-stress environments.

Each of these polycarbonate varieties uses the unique properties of the material to meet the specific requirements of different applications, from vandalism protection to applications that require high UV resistance and stability.

Application of polycarbonate

Polycarbonate, due to its unique combination of impact strength, durability and light-transmitting ability, is used in a wide range of fields. Its use is particularly appreciated where high transparency is required in combination with resistance to mechanical damage. Here are just some of the typical applications of polycarbonate plastics:

• Car headlights: Thanks to its clarity and impact resistance, polycarbonate is an ideal material for car headlights, providing excellent illumination and protection against stones and other elements.
• Safety windows and motorcycle discs: Polycarbonate is used in safety windows and motorcycle discs, offering impact protection without compromising visibility.
• Prescription glasses and safety glasses: Its high clarity and scratch resistance, especially when properly coated, make it the preferred material for optical lenses and safety glasses.
• Machine guards and skylights: In industry, polycarbonate is used in the manufacture of machine guards and skylights, where its impact resistance and ability to transmit light are crucial.
• Streetlamps: Its resistance to weather and UV conditions, after adding special additives, makes polycarbonate an excellent material for outdoor lighting fixtures.

In addition, polycarbonate is used in medical devices that require sterilization, as well as in consumer products such as kitchen appliances, beverage bottles, and water filters, where its glass-like aesthetics and low weight are valued. The bottled water industry uses polycarbonate for larger containers, though there are concerns about the potential for bisphenol A (BPA) to be released into food, prompting the development of BPA-free versions.

Polycarbonate sheets are used for rapid prototypes and inspections thanks to their clearance capability, while polycarbonate filaments are used for 3D printing. Its versatility also allows it to be used in bus stop constructions, where its durability and clarity offer practical benefits.

Advantages of polycarbonate elements

The use of polycarbonate sheets offers a number of significant advantages that make this material the material of choice for many engineering and architectural applications. Listed below are the key benefits of using polycarbonate:

1. Fire resistance: Polycarbonate is distinguished by its excellent fire retardant properties, classified as a material with a fire resistance class B1, which means that it does not ignite when exposed to an open flame and is self-extinguishing. This feature makes it a safer choice than acrylic in applications that require higher fire safety standards.
2. Sustainable development: Polycarbonate is a sustainable material with a long service life and the possibility of full recycling at the end of its life cycle. Additionally, thanks to their natural UV resistance, polycarbonate sheets are an excellent choice for outdoor applications, providing long-lasting performance without degradation.
3. Vandal Resistance: The exceptional impact resistance of polycarbonate makes it a virtually indestructible and vandal-resistant material. This is a significant advantage for applications that require protection against damage, such as bus stops, bicycle sheds or safety glazing.
4. Insulation properties: Polycarbonate effectively retains heat, which makes it an excellent choice for greenhouse structures, creating optimal conditions for plant growth by maintaining an ideal microclimate.
5. Ease of processing: Despite its greater strength compared to acrylic, polycarbonate is easy to process and form. It can be ground, sawed, engraved, drilled, glued, bent (hot) and polished, making it easy to implement complex projects and applications.
6. Material lightness: Polycarbonate is much lighter than glass, making it easier to transport, handle, and install, which is especially beneficial in projects that require large glazing or curtain structures, such as patio canopies.

These properties make polycarbonate a versatile material used in many fields, from construction to advanced engineering applications, offering both functionality and aesthetics.

What are the disadvantages of using polycarbonate?

Despite the many benefits of polycarbonate, there are also some limitations and disadvantages that can affect its use in certain situations:

1. Scratch sensitivity: One of the main limitations of polycarbonate is its tendency to scratches. This material is less scratch-resistant than some other plastics or glass, which can be a problem when exposed to elements that can cause scratches, such as falling branches on the patio canopy. This problem can be partially remedied by using appropriate protective coatings or polishing the material to remove minor scratches.
2. Thermal Expansion: Polycarbonate has a relatively high coefficient of thermal expansion of 0.065 mm/m/°C, which means that the material expands and contracts more than some other materials in response to temperature changes. In practice, this requires taking into account the extra space during installation to allow for free expansion and contraction, and the use of flexible adhesives and sealants that can accommodate these changes without damaging the joints.

When designing and assembling structures using polycarbonate, it is therefore essential to take these properties into account to ensure long-lasting performance and aesthetics without compromise. For applications where the risk of scratches is particularly problematic, you may want to consider using polycarbonate with protective coatings or choosing alternative materials that better meet your design requirements.

How does polycarbonate affect human health?

Polycarbonate, commonly used in the manufacture of food storage containers and other consumer products, is controversial because of its potential risks to human health, mainly related to the presence and release of bisphenol A (BPA). BPA is a chemical compound that has been linked to various negative health effects in some scientific studies, including disruption of the endocrine system.

BPA Bioactivity

• Polycarbonate Hydrolysis and BPA Leaching: High temperatures can accelerate the degradation of polycarbonates, leading to the release of BPA into food or beverages. This leaching phenomenon is particularly worrying in the context of food contact products.
• Effects on Experimental Organisms: Studies in laboratory animals such as mice have shown that exposure to BPA can lead to changes in the size of the reproductive organs, suggesting a potential impact on the reproductive system.
• Analysis of the Impact of Funding on Research Results: There is evidence to suggest that the source of research funding can influence outcomes, with industry-sponsored studies less likely to show negative effects of BPA compared to government-funded studies.

Chemical Interactions and Recommendations

• Reactions with Chemicals: Certain chemicals, such as sodium hypochlorite bleach and other alkalis, can catalyze the release of BPA from polycarbonate products. Polycarbonate is also incompatible with ammonia and acetone, highlighting the need for caution when choosing cleaning agents for these products.
• Recommended cleaning agents: To clean polycarbonate products, it is recommended to use alcohol as a safe solvent to remove grease and oils, minimizing the risk of BPA release.

Public Health Implications

Concerns about BPA have prompted the development of alternative BPA-free materials in the manufacture of food storage containers and other consumer products. At the same time, further research is being conducted to better understand the effects of BPA on human health and to identify potential countermeasures to reduce exposure to the compound. Consumers are encouraged to make informed product choices and adopt practices that minimize the risk of BPA exposure, especially in the context of food storage and heating.

Is polycarbonate toxic?

Polycarbonate as a material is widely used in a variety of applications, including consumer products, building components, as well as medical and food applications. A key issue that has arisen in connection with its use is the presence of bisphenol A (BPA), a compound used in the production process of many polycarbonates, which can be released into food or beverages when exposed to high temperatures or as a result of material degradation.

Polycarbonate toxicity

• BPA Release: The main concern about polycarbonate toxicity is the potential release of BPA, especially when polycarbonate products are used to store food or beverages. BPA is a compound that can interfere with the endocrine system, raising concerns about its effects on human health.
• Non-food uses: Polycarbonates used in non-food applications, such as building materials, electronic components, or spectacle lenses, are generally considered safe because the risk of direct release of BPA into the body is minimal.
• BPA Free Polycarbonates: In response to concerns about BPA, BPA-free polycarbonates are being developed and marketed. These alternative formulations are designed to eliminate the risks associated with BPA release, making them safer for direct food and beverage contact applications.

Regulation and Security

Regulations on the safety of food contact materials, including polycarbonates, are used in many countries to reduce exposure to BPA and other potentially harmful substances. Manufacturers and regulators are working to develop and implement safer alternatives and production methods that minimize health risks.

While traditional polycarbonates can pose risks associated with BPA release, the development of BPA-free versions and strict regulations are designed to increase the safety of these materials. Consumers are advised to pay attention to product labelling and choose BPA-free options, especially for articles intended to come into contact with food, to minimise potential health risks.

What are the differences between polycarbonate and acrylic?

Comparison of Polycarbonate (PC) and Acrylic (PMMA) Properties:

Property	Polycarbonate (PC)	Acrylic (PMMA)
Impact resistance	Much higher than acrylic, about 250 times that of standard glass	Less impact-resistant than polycarbonate, but still better than glass
Clarity and aesthetics	Good optical properties, but may yellow after prolonged exposure to UV	Exceptional transparency and high gloss, ideal for display cases or displays
Resilience and high-strength applications	Higher resilience than acrylic, ideal for applications requiring high resistance (e.g. bulletproof windows)	Less resilience than polycarbonate, less ideal for highly demanding applications
Machining and forming	Harder to process and polish than acrylic, harder to scratch	Easier to process and polish; can be heated and formed repeatedly without losing transparency
Cost	Usually more expensive than acrylic	Typically cheaper than polycarbonate
Recyclable and weatherproof	Recyclable; greater resistance to weather and UV conditions after proper treatment	Recyclable; less resistant to weather conditions than polycarbonate

The choice between polycarbonate and acrylic should be dictated by the specific requirements of the project, including the need for impact resistance, clarity, cost, and how it is processed and formed.

Summary

In conclusion, polycarbonate (PC) and acrylic (PMMA) are two versatile and widely used plastics that are used in many industries thanks to their unique properties. Polycarbonate has significant impact resistance, making it an ideal material for applications that require high strength and safety, such as bulletproof windows and protective covers. However, it is also more prone to scratches and can turn yellow when exposed to UV rays.

Acrylic, on the other hand, offers exceptional transparency and gloss and is the preferred choice for applications where aesthetics and clarity are key, such as display cases or decorative elements. Acrylic is also easier to process and form, which further expands its range of applications. Although less impact-resistant than polycarbonate, acrylic offers better scratch resistance and is cheaper to buy.

The choice between the two materials should depend on the specific design requirements, taking into account aspects such as impact resistance, transparency, cost, processing and forming, as well as environmental and health impacts. In the context of the latter, it is also important to highlight concerns about BPA in polycarbonates, which are driving manufacturers and consumers to look for safer BPA-free alternatives. As such, both polycarbonate and acrylic remain key materials in modern engineering and design, each offering unique advantages tailored to a variety of applications.

Autor: Tomasz Matuszek; Dział Marketingu - Firma Gulajski