Density of Polycarbonate
A plastic material’s density is described as the mass per unit volume of a material, generally measured in grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).
Polycarbonate density generally ranges from 1.20–1.22 g/cm3 and 1200 kg/m.
Polycarbonate’s density is lower which is lower than many other thermoplastics such as polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC). This relatively low density gives polycarbonate some unique advantages and challenges.
The low density of polycarbonate provides a major advantage in applications where weight is a crucial factor, such as in the automotive and aerospace industries.
Polycarbonate can significantly decrease the weight of components and structures when compared to traditional materials like metal, glass, and ceramic. This results in better fuel efficiency, improved performance, and increased payload capacity.
To begin discussing polycarbonate density, it is crucial to first clarify how the density of plastic material is determined.
What is Density
Plastic density is a measure of the mass of a substance per unit volume. It is a fundamental physical property that can identify a material and determine its behavior under different conditions.
The density of a substance can be measured in units of grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).
Factor Affecting Polycarbonate Density
There are several factors affecting the density of polycarbonate, but let me go through the top three factors that have the most impact.
Polycarbonate can be manufactured using two primary methods: interfacial polymerization and melt polymerization. Interfacial polymerization involves reacting bisphenol-A (BPA) with phosgene in a system containing water and an organic solvent. The resulting polymer has a high molecular weight and narrow molecular weight distribution, which contributes to higher density.
Conversely, melt polymerization involves polymerizing BPA and an ester precursor while in the molten state, leading to lower molecular weight and broader molecular weight distribution. Consequently, polycarbonate produced via melt polymerization has a lower density compared to interfacial polymerization.
The density difference between the two methods can reach up to 0.01 g/cm³, influencing the mechanical properties of the material, such as tensile strength and modulus.
Molecular Weight and Branching
The density and mechanical properties of polycarbonate are influenced by its molecular weight and branching. Interfacial polymerization results in polycarbonate with a higher molecular weight and a narrower molecular weight distribution, which contributes to higher density and better mechanical properties.
In contrast, melt polymerization produces polycarbonate with a lower molecular weight and broader molecular weight distribution, which leads to lower density and inferior mechanical properties.
Additionally, branching in polycarbonate reduces its density by creating more free volume between the polymer chains, which lowers its stiffness and strength. Therefore, polycarbonate with low branching and the high molecular weight is more desirable for applications that require high mechanical strength and rigidity.
The mechanical properties of polycarbonate can be enhanced by reinforcing it with fillers, such as glass fibers, mineral fillers, and carbon nanotubes. However, the addition of fillers also impacts the density of polycarbonate. For instance, glass fibers have a higher density than polycarbonate, so their inclusion increases the density of the composite.
Conversely, mineral fillers like talc or calcium carbonate have a lower density than polycarbonate, so their addition decreases the density of the composite. Carbon nanotubes, with their high aspect ratio and low density, can enhance the mechanical properties of polycarbonate without significantly impacting its density.
Consequently, the selection of filler and its concentration should be meticulously evaluated to achieve a balance between density and mechanical properties in polycarbonate composites.
How Polycarbonate’s Density Affects its Processing Conditions?
Polycarbonate’s density plays a crucial role in its processing as it affects the required processing temperature and time. Generally, polycarbonate with higher density demands higher processing temperatures and longer processing times.
This is due to the stronger intermolecular forces present in higher-density polycarbonate, which makes it harder to melt and process.
On the other hand, polycarbonate with lower density can be processed at lower temperatures and for shorter periods because of its weaker intermolecular forces. Nonetheless, the reduced molecular weight of lower-density polycarbonate may lead to lower mechanical properties.
Polycarbonate’s density can also be affected by the processing method employed. Injection molding, which entails melting and injecting molten polycarbonate into a mold, can lead to increased molecular orientation, resulting in a denser material.
In contrast, extrusion involves melting and shaping polycarbonate through a die and typically results in a lower density than injection molding. Hence, the choice of processing method should also be considered when aiming for the desired density and mechanical properties of polycarbonate.
At last, I would like to say the density of polycarbonate is a crucial aspect that influences its mechanical characteristics, processing, and applications.
The production technique, molecular weight, branching, and fillers utilized in polycarbonate all play a role in determining its density. While higher-density polycarbonate generally has better mechanical properties, it necessitates higher processing temperatures and longer processing times.
Conversely, lower-density polycarbonate may have lower mechanical properties, but it can be processed at lower temperatures and for shorter periods. Therefore, a meticulous assessment of polycarbonate density and its effects on properties and processing is critical for optimal use across different industries.