QINGDAO SANJET NEW POWER MACHINERY CO., LTD. , https://www.sanjet.net
Performance and application of polystyrene PS plastic
Polystyrene (abbreviated PS) refers to a polymer synthesized from a styrene monomer by a radical addition polymerization reaction. It is a colorless, transparent thermoplastic with a glass transition temperature above 100 °C. The polystyrene has a glass transition temperature of 80 to 90 ° C, an amorphous density of 1.04 to 1.06 g/cm 3 , a crystal density of 1.11 to 1.12 g/cm 3 , a melting temperature of 240 ° C, and a specific resistance of 1020 to 1022 Ω·cm. The thermal conductivity is 0.116 watts/(m·on) at 30 °C. The usual polystyrene is an amorphous random polymer, which has excellent heat insulation, insulation and transparency. The long-term use temperature is 0 to 70 ° C, but it is brittle and low temperature is easy to crack. There are also isotactic and syndiotactic and atactic polystyrene. The isotactic polymer is highly crystalline, and the syndiotactic polymer has partial crystallinity.
Polystyrene (PS) includes plain polystyrene, expanded polystyrene (EPS), high impact polystyrene (HIPS) and syndiotactic polystyrene (SPS). Ordinary polystyrene resin is non-toxic, odorless, colorless transparent particles, like glass brittle material, its products have extremely high transparency, light transmittance can reach more than 90%, electrical insulation performance is good, easy to color, processing Good fluidity, good rigidity and good chemical resistance. The disadvantages of ordinary polystyrene are that it is brittle, the impact strength is low, stress cracking is easy, heat resistance is poor, and boiling water is not resistant.
Ordinary polystyrene resin is an amorphous polymer, the side group of the polystyrene macromolecular chain is a benzene ring, and the random arrangement of the large volume side groups of the benzene ring determines the physical and chemical properties of the polystyrene, such as high transparency. High stiffness, high glass transition temperature, brittleness, etc.
The expandable polystyrene is made by impregnating a low-boiling physical foaming agent into ordinary polystyrene, and is heated and foamed during processing, and is specially used for making a foamed plastic product. High impact polystyrene is a copolymer of styrene and butadiene, butadiene is a dispersed phase, which improves the impact strength of the material, but the product is opaque. Syndiotactic polystyrene is a syndiotactic structure, which is produced by metallocene catalysts. It has developed a new variety of polystyrene with good performance and belongs to engineering plastics.
Molding performance
Amorphous material, low moisture absorption, does not need to be fully dried, is not easy to decompose, but has a large coefficient of thermal expansion and is prone to internal stress. It has good fluidity and can be molded by screw or plunger type injection machine. It is advisable to use high material temperature, high mold temperature, low injection pressure and prolonged injection time to reduce internal stress and prevent shrinkage and deformation. Various forms of gates can be used, and the gates are connected to the arc of the plastic part to avoid damage to the plastic parts when the gate is removed. The drafting angle is large and the ejection is uniform. The plastic parts have a uniform wall thickness, preferably without inserts. If there are inserts, they should be preheated.
1. The water absorption is extremely small, and it may not be dried before molding. The mold temperature is 30-60 degrees and the material temperature is 140-200 degrees.
2. The property is brittle and easy to crack, and the coefficient of thermal expansion is large, which is easy to generate internal stress.
3. The fluidity is good, and the mold gap should be paid attention to prevent shrinkage and flashing.
4. It is advisable to use high material temperature, high mold temperature and low injection pressure. Prolonging the injection time is beneficial to reduce internal stress and prevent shrinkage and deformation. However, the material temperature is too high, and it is easy to appear silver wire. The material temperature is low or the release agent is more. The transparency is poor.
5. Various forms of gates can be used, the draft angle should be large, and the ejection force should be uniform to prevent cracking.
6. The wall thickness of the plastic parts is even, it is best not to have inserts, each side should be connected by a circular arc, and there should be no gaps or sharp corners.
Applications
Polystyrene is often used to make foamed plastic products. Polystyrene can also be copolymerized with other rubber type polymer materials to produce a variety of different mechanical properties. Common applications in daily life include a variety of disposable plastic tableware, transparent CD cases and so on. Expanded polystyrene is widely used in hollow floor insulation and insulation materials since 2003.
Impact-resistant polystyrene (HIPS)
Impact-resistant polystyrene is an impact-resistant polystyrene product produced by adding polybutyl rubber particles to polystyrene. This polystyrene product adds micron-sized rubber particles and bonds the polystyrene and rubber particles together by means of a graft. When subjected to an impact, the tip stress of the crack propagation is released by the relatively soft rubber particles. Therefore, the crack propagation is hindered and the impact resistance is improved.
Styrene acrylonitrile (SAN)
SAN is an abbreviation for Styrene Acrylonitrile. Styrene acrylonitrile is a copolymer of styrene acrylonitrile and is a colorless, transparent, polypropylene-based engineering plastic with high mechanical strength. The chemical stability of a SAN is better than that of polystyrene. SAN products are less transparent and UV resistant than polymethyl methacrylates but are relatively inexpensive.
Acrylonitrile-butadiene-styrene copolymer (ABS)
ABS is an abbreviation for Acrylonitrilebutadienestyrene. This plastic is a copolymer of acrylonitrile, butadiene and styrene. It has high strength and low weight. It is one of the commonly used engineering plastics.
SBS rubber
SBS rubber is a three-stage block copolymer of a poly(styrene-butadiene-styrene) structure. This material is characterized by both polystyrene and polybutadiene and is a durable thermoplastic rubber. SBS rubber is often used to make tires.