Introduction: Polycarbonate is a polymer that combines a bunch of advantages to make materials that are more in injection molding process line with modern society. Polycarbonate materials are used in a lot of fields, like construction, cars, medicine, infrastructure, ships, aerospace, etc.

It’s pushing out a lot of traditional materials and becoming a really popular new material. This article is going to tell you everything you need to know about polycarbonate plastic resins for injection molding.

What is Polycarbonate?

PC is a type of plastic that has carbonate groups in its chemical structure.

Polycarbonate resins are used in applications that require strength, heat resistance and toughness, and are available in a variety of transparent and opaque colors. These resins are often converted into finished products by injection molding or thermoforming.

Polycarbonates are used in electronic products because they insulate electricity, resist heat, and stop flames. They’re also used in construction, transportation, aviation, and cars. For example, they’re great for car headlight covers because they don’t break easily and they’re smooth.

What are the Types of PC?

Classification by Ester Structure

Aliphatic polycarbonates, such as polyethylene carbonate, polytrimethylene carbonate, and their copolymers, have low melting points and glass transition temperatures, poor strength, and cannot be used as structural materials.

However, due to their biocompatibility and biodegradability, they can be used in drug sustained-release carriers, surgical sutures, bone support materials, and other applications.

Aromatic polycarbonate: Aromatic polycarbonate is the best kind of polycarbonate and is the most important kind of polycarbonate.

Aliphatic-aromatic polycarbonate: It is a combination of aliphatic and aromatic polycarbonate, but it is not used much in engineering plastics.

Classification by Performance and Use

Polycarbonate film and sheet are one of the main forms it is used in. It can be further divided into multiple types based on different performance and uses:

Transparent PC film: It has the advantages of high transparency, high strength, high heat resistance, and high weather resistance. It is mainly used in optical lenses, display panels, flat-panel TV screens, mobile phone screens, and other fields.

Frosted PC film:Mostly used in wear-resistant and soft light occasions like panels, labels, nameplates, dashboards, in-mold decorative panels, etc., which can effectively reduce the highlights on the surface of objects and have clear printing effects.

Print-grade PC film: It prints well and is flat. It’s used for electronic tags, membrane switches, panels, and other stuff.

Flame-retardant PC film: It’s great at not catching on fire. It’s used for insulation in power systems, disk drives, keyboards, TVs, monitors, computer motherboards, and other stuff.

Optical-grade PC film: It has good optical purity, light transmission performance, and yellowing resistance, and is especially suitable for screen display and optical lens fields.

Functional PC film: It has various special functions, such as anti-static, UV protection, hardening, antibacterial, privacy protection, etc., and is widely used in construction, automobiles, medical equipment, and other fields.

Other Types

Besides the above classification, polycarbonate can also be classified by other standards, such as injection molding grade PC, extrusion grade PC, etc. by different production processes; PC/ABS alloy, PC/glass fiber reinforced materials, etc. by different reinforcing materials.

What are the Properties of PC?

Thermal Properties

Polycarbonate is a good heat-resistant plastic among general engineering plastics. Its decomposition temperature is above 300°C, and its long-term working temperature can reach 120°C. It also has good cold resistance. Its brittle temperature is as low as -100°C. Its long-term use temperature range is 60~120°C.

Electrical Properties

Polycarbonate has a small molecular polarity, a high glass transition temperature, and low water absorption, so it has excellent electrical insulation properties, which are close to or equivalent to PET, which has always been considered to have excellent electrical insulation properties.

The electrical insulation of polycarbonate is closely related to temperature, humidity, electric field frequency, and product thickness.

Chemical Properties

Polycarbonate (PC) is a polyester of carbonic acid. Carbonic acid itself is not stable, but its derivatives (like phosgene, urea, carbonates, carbonates) have some stability.

Physical Properties

Density: 1.18-1.22 g/cm3

Linear expansion rate: 3.8×10-5 cm/°C

Heat deformation temperature: 135°C

Low temperature -45°C, polycarbonate is colorless and transparent, heat-resistant, impact-resistant, flame-retardant BI grade, and has good mechanical properties within normal use temperature.

Flow Properties

Molecular chains are hard to slide, the melt viscosity is high, the fluidity is poor, and the injection molding processability is poor. The melt viscosity of polycarbonate increases with the increase of relative molecular mass. During molding, it is often more effective to improve its flow state by adjusting the temperature than to change the shear rate.

Optical Properties

Polycarbonate is a non-crystalline material. Pure polycarbonate is colorless and transparent with good light transmittance. However, its surface hardness is poor, its wear resistance is poor, and its surface is easy to become hairy, which affects its light-inducing properties.

Mechanical Properties

Polycarbonate has great mechanical and electrical properties , especially its impact strength and dimensional stability. It can keep high mechanical strength in a wide temperature range. Its disadvantages are poor fatigue resistance and hemp resistance, and it is more likely to produce stress cracking.

Polycarbonate’s impact strength is one of the best among general engineering plastics and all thermoplastic resins, and its value is similar to that of 45% glass fiber reinforced poly FET. The main factors affecting the impact strength of polycarbonate are molecular weight, notch radius, temperature, and additives.

Degeneration: Polycarbonate’s resistance to degeneration is pretty good among thermoplastic engineering plastics, even better than nylon and polyurethane. The dimensional change and cold flow deformation caused by water are very small. This is an important sign of its excellent dimensional stability.

What are the Advantages of PC?

Weather Resistance

PC material has excellent weather resistance and can maintain excellent performance in outdoor conditions. It has strong resistance to UV rays, oxidants, and other environmental factors.

Temperature Resistance

The glass transition temperature and melting temperature are high, and the temperature resistance is high. Its decomposition temperature is above 300°C, and the long-term working temperature can be as high as 120°C. At the same time, it has good cold resistance, and the brittle temperature is as low as -100°C. Its long-term use temperature range is -60 to 120°C.

Chemical Resistance

PC material has high resistance to many chemicals, including alcohols, ketones, and acids. However, it has weak resistance to some solvents (such as ketones).

High Strength and Stiffness

PC material has high strength and stiffness, much higher than ordinary plastics like ABS and PVC. This makes PC an ideal choice for making parts that require high durability and impact resistance.

Good Dimensional Stability

PC has better creep resistance compared to other thermoplastic engineering plastics such as PA and POM. It has very low dimensional change and cold flow deformation due to water absorption, and it has low shrinkage rate, so it has good dimensional stability.

Aging Resistance And Flame Resistance

Polycarbonate is also good at resisting heat aging. If you put the film in the air for a long time and heat it, it will change very little. However, if polycarbonate is exposed to sunlight, oxygen, and water vapor for a long time, especially at high temperatures, and contains certain impurities, it will degrade.

Polycarbonate is flammable, with a light yellow flame and black smoke/index of only 25%, which will go out when it is away from the fire source. Generally, halides, trioxide, magnesium hydroxide, phosphoric acid and red phosphorus are added to improve flame retardancy.

Good Transparency and Gloss

PC materials have excellent transparency and gloss, and can be modified to achieve different colors and surface effects. This makes it an ideal choice for manufacturing products that require high transparency.

What are the Disadvantages of PC?

Although PC materials have many advantages, they also have many disadvantages:

Low Fatigue Strength

Polycarbonate sheets can only bear a small load for a long time, so they are not suitable for applications that require continuous or high-intensity pressure. The low fatigue strength of polycarbonate sheets may cause performance degradation or failure during long-term use.

Not Resistant to Acid and Alkali

Polycarbonate is not resistant to acids and alkalis, and it will react chemically with acids and alkalis, causing corrosion on the surface of the sheet. Therefore, the use of PC sheets may be limited in environments that require contact with strong acids or strong alkalis. It should be noted that polycarbonate can resist weak acids, but cannot directly contact strong acids.

Poor Wear Resistance

PC materials have a lot of freedom in their molecular chains, and there is a lot of space between the chains. They are easily affected by external forces and easily scratched and worn.

PC materials have low molecular crystallinity and a relatively disordered molecular chain arrangement, which makes it easy for microscopic pits to form on the surface of PC materials, reducing their scratch resistance.

PC materials can improve their self-lubricity by adding powdered PTFE, and their wear resistance can be improved by adding glass fiber to increase hardness.

Poor Hydrolysis Resistance

Because the molecular chain contains -COO (group), polycarbonate can undergo hydrolysis reaction to generate corresponding acid or alcohol in the presence of acid or alkali. Therefore, conventional PC has low hydrolysis stability and cannot be used for products that are repeatedly subjected to high-pressure steam.

Sensitive to Notches

Notch sensitivity is when a product cracks along a notch (collapse, burr) on the edge of the product when force is applied. PC products are prone to cracking when there is a notch because it is difficult to eliminate the internal stress of PC products.

Poor Stress Cracking Resistance

But when an outside force makes the chains line up, they don’t want to relax back to their original, random state. This makes it hard to get rid of the stress inside the product after it’s been molded.

What are the Applications of PC?

Building Materials Industry

Polycarbonate sheets have good light transmittance, impact resistance, resistance to ultraviolet radiation, and the dimensional stability and good molding and processing performance of their products, making them have obvious technical performance advantages over the inorganic glass traditionally used in the construction industry.

China has built more than 20 polycarbonate hollow board production lines for building materials, with an annual demand of about 70,000 tons of polycarbonate, which will reach 140,000 tons by 2005.

Automobile Manufacturing Industry

Polycarbonate is great for cars and trucks because it’s tough, can handle heat, can handle the weather, and is hard. It’s used to make lots of different parts for cars and trucks, but mostly for lights, dashboards, heater plates, defrosters, and bumpers made out of polycarbonate blends.

Based on data from developed countries, the proportion of polycarbonate used in the electronics, electrical, and automotive manufacturing industries is 40% to 50%, while China’s use in this field is only about 10%.

The electronics, electrical, and automotive manufacturing industries are China’s rapidly developing pillar industries, and the demand for polycarbonate in these fields will be huge in the future. China has a large total number of cars and a large demand, so the application of polycarbonate in this field has great potential for expansion .

Medical Equipment

Because polycarbonate products can withstand steam, cleaning agents, heating, and high-dose radiation sterilization without yellowing and physical performance degradation, they are widely used in artificial kidney hemodialysis equipment and other medical equipment that needs to be operated under transparent and intuitive conditions and needs to be repeatedly sterilized.

For example, they are used to make high-pressure syringes, surgical masks, disposable dental appliances, blood separators, and so on.

Aerospace

With the rapid development of aviation and aerospace technology, the requirements for various components in aircraft and spacecraft are constantly increasing, which has led to an increasing application of PC in this field.

According to statistics, there are 2,500 polycarbonate parts used on a Boeing aircraft alone, and a single aircraft consumes about 2 tons of polycarbonate. On the spacecraft, hundreds of polycarbonate parts with different configurations and reinforced by glass fiber and astronauts’ protective equipment are used.

Packaging

A new growth point in the packaging field is various types of water storage bottles that can be repeatedly disinfected and used.

Because polycarbonate products have the advantages of light weight, good impact resistance and transparency, and no deformation and transparency when washed with hot water and corrosive solutions, PC bottles have completely replaced glass bottles in some fields.

It is predicted that as people pay more attention to the quality of drinking water, the growth rate of polycarbonate in this area will remain above 10%, and it is expected to reach 60,000 tons by 2005.

Furthermore, when producing high-quality plastic toys, we use plastic injection molding technique and plastic injection molding resins to ensure the precision and durability of the final product.

Electronics Industry

Polycarbonate is a great insulating material because it has good and consistent electrical insulation in a wide range of temperature and humidity. It’s also got good flame retardancy and dimensional stability, which makes it useful in a lot of different electronic and electrical applications.

Polycarbonate resin is mainly used to make all kinds of food processing machinery, power tool shells, bodies, brackets, refrigerator freezer drawers, and vacuum cleaner parts. In addition, for computers, video recorders, and color TVs that require high precision parts, polycarbonate materials are also very valuable.

Optical lens

Polycarbonate is super important in this field because it has high light transmittance, high refractive index, high impact resistance, dimensional stability, and is easy to process and mold. Optical lenses made of optical grade polycarbonate can be used in cameras, microscopes, telescopes, and optical testing instruments.

They can also be used in movie projector lenses, copier lenses, infrared automatic focus projector lenses, laser beam printer lenses, and all kinds of prisms, multi-faceted reflectors, and other office equipment and home appliances. It has a really wide range of applications.

Another important application area of polycarbonate in optical lenses is as a lens material for children’s glasses, sunglasses, safety glasses, and adult glasses. The annual average growth rate of polycarbonate consumption in the world’s eyewear industry has remained above 20%, showing great market vitality.

Optical Disc Manufacturing Industry

With the rise of the information industry, optical discs made of optical grade polycarbonate are developing rapidly as a new generation of audio and video information storage media. Polycarbonate has become the main raw material for the world’s optical disc manufacturing industry due to its excellent performance characteristics.

The amount of polycarbonate consumed by the world’s optical disc manufacturing industry has exceeded 20% of the overall polycarbonate consumption, and its average annual growth rate exceeds 10%.

China’s optical disc production has grown rapidly. According to figures released by the State Administration of Press and Publication, there were 748 optical disc production lines in the country in 2002, with an annual consumption of about 80,000 tons of optical grade polycarbonate, all of which were imported.Therefore, the application prospects of polycarbonate in the field of optical disc manufacturing are extremely broad.

Food and Beverage Industry

PC (Polycarbonate) is commonly used in the food and beverage industry, high melting point, anti-collision containers, Japanese packaging, water bottles, and Japanese food containers. The selection of practical transparency and durability makes it safe and practical.

Summary

Among plastic resin, acrylonitrile butadiene styrene (ABS) and high density polyethylene (HDPE) are commonly used to manufacture a variety of products, while polycarbonate (PC) offers greater transparency and heat resistance .

PC is a high-performance thermoplastic with excellent mechanical strength, heat resistance, transparency, and electrical insulation. It is widely used in construction, automobiles, medical devices, aerospace, packaging, electronics, optical lenses, and more.

Although it has excellent impact strength and dimensional stability, it also has some drawbacks, such as low fatigue strength, poor acid and alkali resistance, and poor wear resistance. However, PC is versatile and adaptable, meeting the diverse material needs of modern industry.