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Polycarbonate is a popular engineering plastic used in many domestic and industrial applications.
Polycarbonate manufacturers employ a wide range of techniques to achieve shapes with detailed finishing and tight tolerance.
In this eBook, you will learn about 9 different polycarbonate fabrication methods used in industries. It will focus on how and when you should choose a particular processing or finishing technique.
However, before we start discussing these fabrication techniques, let’s begin by explain unique facts about polycarbonates.
Chapter One: What Is Polycarbonate?
Polycarbonate (PC) is a thermoplastic polymer with the carbonate groups in its chemical structure.
Its structure contains carbon, hydrogen and phenyl groups (aromatic rings). It is these three that are responsible for the desirable chemical and physical properties of polycarbonate products.
Generally, it has a monomer referred to as bisphenol A.
Below, is an image showing the chemical structure of polycarbonate:
Chemical structure of polycarbonate (PC)
Manufacturing process of polycarbonate sheet is due to a reaction between bisphenol A and carbonyl chloride. On the other hand, bisphenol A is produced by condensation of acetone and phenol. This reaction takes place under acidic conditions.
At the moment, polycarbonate sheet is the most popular engineering plastic used globally. The global demand for the product has increased exponentially over the past decade to more than 1.5 million tons.
This is mainly attributed to superior physical and chemical properties.
Chemical and physical properties of polycarbonates
All these features are attributed to the nature of the bonds that exist between polycarbonate structures. It involves a critical analysis of every single element. This forms a critical part when optimizing the general performance of this material.
phenyl and methyl groups
Physical properties of polycarbonates
1. High strength
It can withstand a large amount of impact. This explains a reason why PC sheets are a perfect choice for hurricane barricades, anti-ballistic shields and glazing applications, just to mention a few.
The sheet is generally shatterproof. Normally, the magnitude of impact it can resist will also depend on the thickness of the sheet.
Ideally, polycarbonate sheets have a compressive yield strength of 70MPa and modulus of 2.0GPa.
2. Optical properties
Polycarbonates are transparent plastics that can transmit up 99.99% of visible light. The aromatic rings prevent the formation of crystalline structure. Crystalline structure tends to undermine optical properties of substances.
On average, polycarbonate sheets have a refractive index of 1.584.
Normally, companies that manufacture polycarbonate sheets may decide to manipulate optical properties to suit a given application. The process may include tinting or embossing.
Tinted and embossed polycarbonate sheet
3. Dimensional stability
Both phenyl and methyl structures make polycarbonate rigid. Again, due to their amorphous structure, polycarbonates experience little elongation when subjected to high stretching or compressive forces.
4. Electrical resistance
There is zero mobility of electrons within a polycarbonate structure. Therefore, it is considered an insulator. Of course, this is attributed to the existence of molecular forces between its molecules.
5. Heat resistance
Polycarbonate will maintain its desirable physical and chemical properties at extreme temperatures. That is, between 140°C to -20°C. This makes them a perfect choice for most electrical applications.
Polycarbonate heat resistance
Polycarbonate is self-extinguishing. That is, it is classified as UL94. They do not burn during fire outbreak, thus, a perfect choice in fire prone areas.
Here, you will understand how polycarbonate may react with other substances or chemicals. These are important factors that play a pivotal role in performance and reliability of polycarbonate sheets.
1. Reaction with chemicals
Polycarbonate is generally resistant to dilute acids, mineral oils, vegetable oils and alcohols. However, it is worth noting that it reacts easily with bases, esters, aliphatic hydrocarbons, oxidizing agents, halogenated hydrocarbons and concentrated acids.
It is for this reason that most polycarbonate manufacturing companies recommend certain cleaning agents.
Reaction with chemicals
2. Water absorption
These plastics absorb a very small amount of water (<0.6%). However, they may begin to decompose when washed for a long time in hot water. The fact that polycarbonates absorb a low amount of moisture makes them dimensionally stable
Again, it is due to this that manufacturers employ different mechanisms to ensure that the final product has the desired performance properties.
For example, during molding, polycarbonates are subjected to a ventilated or dryer temperature of 120° C and 0.1% humidity.
In addition to these, polycarbonates are not inherently resistant to scratched and UV radiation. This is actually the main reason manufacturers add certain chemical additives to improve their performance.
A good manufacturer should avail all test results to verify the physical and chemical properties discussed above. These tests many include: impact analysis, tensile strength, thermal and light transmission tests.
With all these, it is possible to classify polycarbonates based on design and structure. Normally, this is where polycarbonate manufacturers use their ability to fabricate it into desired shapes and parts.
Classification of polycarbonates
They are available in form of panels or sheets. They don’t have air spaces between the polycarbonate sheets and are popular for their high impact strength and excellent optical properties.
Polycaronate solid sheet
As the name suggests, they have air spaces in between the layers of polycarbonate sheets. They provide an excellent insulation. The dividing walls between the layers act as a supportive structure.
Classification criteria is based on the number of walls – twin, triple, etc.
Polycaronate hollow sheet