Overview of technical standards and specifications for flame retardant ABS plastics

ABS is a flammable material and belongs to the HB level according to the UL94 standard. ABS burns quickly when it catches fire, and emits a lot of poisonous gas and black smoke, which is not conducive to practical application. With the advancement of science and technology and the improvement of the quality of life, people's safety awareness is getting stronger and stronger. Domestic and foreign countries have put forward strict fire and flame retardant requirements for plastic materials used in automobiles, construction, household appliances, office supplies, etc., and formulated corresponding technologies. Standards and specifications, so the study of flame retardant ABS has a very important significance.

There are three main ways to reduce the flammability of ABS resin:

1. Blend the flame retardant polymer with ABS, such as CPE and PVC;

2. Chemically modifying the existing ABS, such as adding tribromostyrene as the fourth monomer to prepare four components of ABS;

3. Through the general method, I want to add flame retardant to ABS, including inorganic flame retardant (such as MoO3) and organic flame retardant (such as halogen compound, phosphorus flame retardant). The flame retardant type has an efficient flame retardant effect, but other properties may be poor (such as aging, high cost). Chemically modified ABS requires a specific production process and the process is more complex. The third method strikes a balance between cost and performance and is more flexible in designing multifunctional materials. At present, the flame retardant modification of ABS materials is mainly based on the addition of high-efficiency halogen-containing flame retardants.

Second, heat-resistant (high temperature) grade ABS

The heat distortion temperature of the heat-resistant ABS resin is generally 90 to 105 ° C, and has good heat resistance, toughness and fluidity. It can be used in the production of automobile doors, rear wheel cover inner panels, panels, etc., and is used in home appliances such as microwave ovens, rice cookers, hair dryers, and the like. The heat resistance of ABS can be improved by lowering the rubber content, increasing the SAN molecular weight and the acrylonitrile content, but the method of developing heat-resistant ABS by adding heat-resistant monomers or heat-resistant additives has attracted more attention.

Introduction of α-methylstyrene (MS), maleic anhydride into ABS resin

(MA) and maleimide (MI) improve the heat resistance of ABS. There are two main ways:

1. Copolymerization of MS, MI, etc. as a third monomer with styrene and acrylonitrile increases the rigidity of the matrix resin and increases its Tg. The copolymer of MA and AN has better heat resistance than SAN of the same AN ​​content, and the Vicat softening temperature is 123 ° C and 103 ° C, respectively. The chemical and physical properties of the two are similar, and the production methods are also versatile. The material based on MS is yellower than the styrene based material. In actual production, MS only partially replaces styrene to obtain SMSAN copolymer. The replacement ratio depends on the heat resistance requirements.

2. A heat-resistant styrene-maleic anhydride copolymer (SMA) or a styrene-maleimide copolymer (SMI) is added as a blend component to the ABS resin. The Vicat softening point temperature of SMA can reach 150 °C. However, SMA is unstable at higher temperatures. It will release carbon dioxide, so it must be released to keep it stable enough and can be processed at 260 ° C, otherwise the workpiece will have radiation. The addition of 1% hindered phenol antioxidant and thioester synergist to SMA stabilizes it. SMI can be used where higher than SMA and MS can provide heat resistance. The production process of styrene and MI copolymerization is the same as that of SAN. SMI can also be prepared by reacting SMA with ammonia or an amine to imidize. SMI has good thermal stability at high temperatures and does not produce radiation.

Third, antistatic grade ABS

The resistance performance of the SAN is slightly lower than that of the PS due to the nature of the AN polarity, but it still has sufficient insulation. The surface static charge of ABS causes problems such as adsorption of dust, difficulty in demolding, and electrostatic discharge during processing, transportation, and use. Therefore, ABS products need to have a certain conductivity to prevent internal discharge, and even shield the external electromagnetic interference of precision electronic components. The addition of an antistatic agent prevents the generation of static charges or dissipates static charges, and is the main method for preparing antistatic grade ABS.

Antistatic agents can be added prior to or during processing of the ABS. According to the addition method, the types of antistatic agents are as follows:

(1) An external antistatic agent is applied to the surface of an ABS product in the form of water or an alcohol solution, and a quaternary ammonium salt is most often used. The quaternary ammonium salt can reduce the surface resistance of the workpiece, but is easily removed during use, cleaning, etc., and is therefore widely used for short-term use such as preventing ash deposition on display parts.

(2) The internal antistatic agent is added during ABS processing, and the added amount is small (0.1%~3%), which is compatible with ABS to a certain extent. The internal antistatic agent is divided into a migration antistatic agent and a permanent antistatic agent, the migration antistatic agent is an ionic or nonionic surfactant, the hydrophobic portion is limitedly compatible with ABS, and the hydrophilic portion migrates inside the ABS to The surface can adsorb water to increase surface conductivity. After the surface antistatic agent is removed, the internal antistatic agent can still migrate to the surface until it is completely depleted, so it is used for a longer period of time than the external electrostatic agent. The permanent antistatic agent does not migrate, including highly conductive fillers (such as carbon black, metal coated carbon fiber, stainless steel wire), hydrophilic polymer materials (such as polyoxyethylene copolymer), and conductive polymer materials ( Such as polypropylene, polythiophene). Among them, the hydrophilic polymer material is low, and is mainly used in office automation equipment. Conductive fillers are not suitable for use in indicating color, transparency, and electronics.