What is Polystyrene?
Polystyrene can be divided into thermoplastic materials and thermosetting materials according to its polymer structure. Thermosetting materials cannot be remelted after the initial molding, while thermoplastic materials can be melted and reused many times. Therefore, thermoplastic polystyrene (PS) can be used for injection molding and then recycled.
Polystyrene (PS), a polymer synthesized by free radical addition polymerization of styrene monomer, has a chemical formula of (C8H8)n. It is a colorless and transparent thermoplastic with a glass transition temperature above 100 °C, excellent thermal insulation, insulation and transparency, and is widely used in fields such as plexiglass, ABS resin, electronic appliances and other engineering plastics.
Material Characteristics
Polystyrene is colorless and transparent, can be freely colored, has a relatively low relative density, is similar to polypropylene (PP) and polyethylene (PE), has excellent electrical properties, especially good high-frequency properties, second only to F-4 and PPO. In addition, in terms of light stability, it is second only to methacrylic resin, but its radiation resistance is the strongest among all plastics. The most important feature of polystyrene is that it has very good thermal stability and fluidity when melted, so it is easy to mold and process, especially easy to inject and mold, and is suitable for mass production.
A.Mechanical properties
Polystyrene molecules and their aggregated structures determine that it is a kind of rigid brittle material, which exhibits brittle fracture under stress.
B.Thermal properties
The characteristic temperatures of polystyrene are: brittle temperature around -30 ℃, glass transition temperature 80~105 ℃, melting temperature 140~180 ℃, and decomposition temperature above 300 ℃. Since the mechanical properties of polystyrene decrease significantly with the increase of temperature and its heat resistance is poor, the continuous use temperature is about 60 ℃, and the maximum should not exceed 80 ℃. The thermal conductivity is low, 0.04~0.15 W/(m·K), which is almost unaffected by temperature changes and has good thermal insulation.
C.Electrical properties
Polystyrene has good electrical properties, with volume resistivity and surface resistivity as high as 1016~1018 Ω·cm and 1015~1018 Ω respectively. The dielectric loss tangent is extremely low and is not affected by changes in frequency, ambient temperature, and humidity. It is an excellent insulating material.
D.Optical properties
Polystyrene has excellent optical properties, with a light transmittance of 88% to 92% and a refractive index of 1.59 to 1.60. It can transmit all wavelengths of visible light. Its transparency is second only to acrylic polymers such as plexiglass among plastics. However, due to its poor weather resistance, polystyrene will become turbid and yellow when exposed to sunlight and dust during long-term use or storage. Therefore, when using polystyrene to make highly transparent products such as optical components, it is necessary to consider adding appropriate types and amounts of antioxidants.
E.Chemical properties
Good corrosion resistance, poor solvent resistance and oxidation resistance.
Common Uses of Polystyrene
Solid plastic PS is often used to make medical products, such as petri dishes or test tubes, but can also be used to make common household products such as yogurt containers, smoke detector housings, and red Solo cups. In addition, polystyrene can be used in automobiles, electrical components, and electronics. The transparency of PS also makes it ideal for optical applications such as lighting fixtures.
A: Packaging
Polystyrene is widely used in the packaging industry because of its lightweight, strong, and insulating properties. It is used to make disposable food containers, cups, plates, and trays.
B: Electronics
Polystyrene is used in the electronics industry to make housings and cases for various devices because of its rigidity and electrical insulating properties. It is also used to produce CD and DVD cases.
The transparency of polystyrene makes it ideal for optical applications such as lenses and light diffusers in electronic displays.
C: Construction
In the construction industry, polystyrene is used for thermal insulation because of its low thermal conductivity. Expanded polystyrene (EPS) and extruded polystyrene (XPS) are commonly used for thermal insulation in walls, roofs, and floors.
D: Automotive
In the automotive industry, polystyrene is used to make various parts such as dashboards, knobs, and air vents. Its lightweight properties help reduce the overall weight of the vehicle, thereby improving fuel efficiency.
E: Medical
Finally, the medical industry utilizes polystyrene to make petri dishes, test tubes, and other laboratory equipment because of its high transparency and good chemical resistance. The inertness of polystyrene makes it suitable for applications where chemical reactions or contamination must be avoided.
What are the advantages of plastic injection molding?
The advantages of polystyrene plastic injection molding are low shrinkage, good moldability, and the flexibility to use it in mixed and foamed forms. Like all thermoplastics, polystyrene is reusable and easy to mold. It also has the characteristics of low shrinkage during the injection molding process. Typically, polystyrene shrinks less than 0.5%, which is low compared to other injection molding plastics. This property allows it to capture complex design details of parts.
What are the disadvantages of plastic injection molding?
The disadvantages of polystyrene plastic injection molding are low melt flow index, high melting point, and narrow temperature range. Polystyrene has a relatively high melting temperature of 210 ºC to 250 ºC, so injection molding requires higher energy.
The temperature range in which polystyrene begins to soften and melt is relatively short, so the process must be carefully monitored and designed accordingly. Unmodified polystyrene is also brittle, causing parts to fail easily when demolded from the mold. The ejector pins must be carefully designed to ensure that the part can withstand the bending stresses created during the ejection process.
Polystyrene Recycling
A: Mechanical recycling
By crushing and compressing the discarded EPS, it is processed into granular raw materials for making new plastic products, such as barrels, boxes, plates, etc. This method can not only effectively reduce the pollution of waste to the environment, but also save raw material resources and realize the recycling of resources.
B: Waste solidification
The discarded EPS can be heated and compressed to make its structure tight and form a solid material. This method is suitable for making building materials such as furniture and decorative panels, extending the service life of EPS, reducing the consumption of new plastics, and thus reducing the negative impact on the environment.
C: Biodegradation technology
Decompose it into harmless substances. The application of these technologies has injected new vitality into the sustainable development of the construction industry.
