Engineering Plastics Resins Roundup! Part II- Resins

In exploring the world of engineering plastics and their flame retardants, we have not only gained an in-depth understanding of the properties and applications of these materials, but have also witnessed the critical role they play in enhancing the safety and performance of products.

1. PC / ABS

PC has the advantages of high impact strength, creep resistance, good dimensional stability, heat resistance, transparency and dielectric properties, but there are also poor processing fluidity, prone to stress cracking, notch sensitivity, poor abrasion resistance and other shortcomings; ABS has a better resistance to chemicals and molding and processing, however, its heat resistance and weathering resistance is relatively poor. The two blended modified PC / ABS alloys in the performance of complementary, not only heat resistance, impact strength and tensile strength is better than ABS, and its melt viscosity is lower than the PC, good processing performance, the product of the internal stress and impact strength of the thickness of the product sensitivity are greatly reduced.

PC/ABS alloys are widely used in the automotive industry, communication equipment, electronic appliances, lighting equipment and so on. In order to meet the fire safety requirements in some applications, PC/ABS alloy must have good flame retardancy. For example, in the new energy vehicle charging pile and some electrical and electronic flame retardant grade to reach V-0. For PC / ABS blending system is currently a good effect of good thermal stability of bis-phosphate esters and phosphate ester zwitterionic polymers, etc., of which the BDP on PC / ABS alloys show good flame retardant properties.

2. PC

PC has good heat resistance, excellent optical properties, good dimensional stability, high mechanical strength and impact strength, etc., widely used in household appliances, electronic appliances, automotive parts, mechanical equipment and optical instrument parts, etc. PC's Limit Oxygen Index (LOI) of up to 21% to 24%, the material itself can be up to UL94V-2 flame retardant, but still can not meet the special areas of flame retardant. The material itself can reach UL94V-2 level of flame retardancy, but it still can't meet the higher requirements for flame retardancy in special fields, such as electrical and electronic and automobile fields, which require PC to reach V-0 level of flame retardancy.

Flame retardant PC, with potassium perfluoroalkyl sulfonate (PPFBS) as the representative of the sulfonate flame retardant is the best effect, adding a small amount of sulfonate flame retardant can significantly improve the flame retardant properties of PC to achieve a flame retardant grade of 1.6 to 3.0mmV-0, and the physical and mechanical properties of the modified PC is comparable to the general-purpose PC.

Industrialized PC products in the most used phosphorus flame retardant is mainly triphenyl phosphate (TPP), resorcinol bis (diphenyl phosphate) (RDP) and BDP, in the flame retardant additive amount of 10% (mass fraction), 1.6mm thickness of PC up to the V-0 level, which is volatile at high temperatures, TPP only play a role in the gas phase of the flame retardant; RDP and BDP can play a flame retardant effect in the gas phase and solid phase at the same time, TPP is solid at room temperature, thermal stability is relatively poor, easy to volatilize in the PC processing temperature; RDP and BDP at room temperature for the liquid, thermal stability is better; BDP better than the hydrolysis resistance of RDP.

3. ABS resin

ABS has high gloss, good toughness, good heat and low temperature resistance, excellent processing performance, with excellent overall mechanical properties; ABS electrical properties do not appear with the temperature and humidity changes and great changes, is a good insulating material, widely used in household appliances, audio-visual equipment, office supplies and electrical and electronic fields.

ABS resin is combustible, the LOI is 18.3% to 18.8%, according to UL94 standard belongs to HB level, ABS burns fast when it catches fire, and emits a lot of poisonous gas and black smoke, which is unfavorable for practical application. At present, the main halogen flame retardants and Sb2O3 compound use, halogen antimony synergistic effect of flame retardant modification of ABS.Flame retardant ABS is mainly used in telephones, computers, liquid crystal displays (LCD) and other electrical and electronic equipment shells, automotive components and external components, small kitchen appliances, tool boxes, vacuum cleaner shells and so on.

4. HIPS

HIPS is made of polystyrene (PS) and polybutadiene (PB) through the copolymerization of the two common advantages, easy to process, good dimensional stability and excellent electrical insulation, high impact resistance, is widely used in food packaging, household appliances, electronic products and military materials, such as shell packaging and other fields.

However, the LOI of HIPS is only 18%, easy to burn, in order to improve the safety of use, it must be flame retardant modification. Used in HIPS flame retardant modification of the main bromine flame retardants such as decabromodiphenyl ethane (DBDPE), most of the synergistic effect with Sb2O3 with excellent flame retardant effect.

5. PBT

PBT is a crystalline saturated polyester, with excellent mechanical properties, good dimensional stability, good electrical insulation and resistance to chemicals, etc., widely used in automobiles, electrical and electronic appliances, machinery and other fields.

However, PBT has poor flame retardant properties (UL94 HB level), easy to burn in the air, difficult to become charcoal, easy to drip when burning, and releases a large amount of smoke and toxic gases, easy to produce a relatively large number of hazards, so it must be flame retardant modification.

Flame retardants for PBT flame retardant modification is mainly halogenated flame retardants, more commonly used brominated flame retardants such as DBDPE, brominated epoxy resins, etc., through the synergistic effect with the Sb2O3, to achieve excellent flame retardant effect.PBT flame retardant used in the use of the flame retardant also includes aluminum diethylphosphonate (ADP) or its magnesium hydroxide, aluminum hydroxide, etc., the compound products.

6. PA

PA has good mechanical properties, electrical properties and more prominent lubricating properties, widely used in electronic components and automotive parts and other fields. Unmodified PA flame retardant grade UL94 V-2, LOI of 20% to 22%, in contact with open flames, rapid combustion will occur, releasing a large amount of heat, but also due to the presence of molten flame drop phenomenon, which creates conditions for the further spread of open flames.

In order to prevent fire hazards, the industry has clear flame retardant requirements for PA composites used in automobiles, electrical appliances and other products, which are generally required to reach UL94V-0 level. Halogenated flame retardants are widely used in PA due to their good compatibility with PA and high flame retardant efficiency.

Flame retardants used in PA also include aluminum diethylphosphonate (ADP) or its compound products with magnesium hydroxide and aluminum hydroxide. In summary, at present, in the flame retardant system of engineering plastics, flame retardant PC/ABS, flame retardant PC mainly use phosphorus flame retardant BDP; flame retardant ABS, flame retardant HIPS, flame retardant PBT, flame retardant PA mainly use bromine flame retardants.

Conclusion

Whether in electronic devices, building materials, or automotive manufacturing, engineering plastics and their added flame retardants play an integral role in ensuring the safety and convenience of our daily lives.

As technology continues to advance and new materials are developed, we expect that these materials will continue to drive innovation and growth in a variety of industries in an even more environmentally friendly and efficient manner. Ultimately, through continuous research and improvement, we will be able to create engineering plastics products that are safer, more reliable and in line with our sustainability goals to meet the challenges of the future.