Acrylonitrile-butadiene-styrene copolymer (ABS) has excellent electrical properties, cold resistance, oil resistance, chemical stability, and impact properties, and is widely used in the fields of electromechanics, home appliances and transportation. However, the oxygen index of ABS is only 18%, and it can continue to burn after the fire, which limits its products in many application fields. In order to achieve the flame retardant rating of ABS to UL94 V-0, the amount of flame retardant added is generally large. The mechanical properties of the material are reduced, and the cost is higher.
Acrylonitrile-butadiene-styrene copolymer (ABS) has excellent electrical properties, cold resistance, oil resistance, chemical stability, and impact properties, and is widely used in the fields of electromechanics, home appliances and transportation. However, the oxygen index of ABS is only 18%, and it can continue to burn after the fire, which limits its products in many application fields. In order to achieve the flame retardant rating of ABS to UL94 V-0, the amount of flame retardant added is generally large. The mechanical properties of the material are reduced, and the cost is higher.
Polytetrafluoroethylene (PTFE) has a good anti-dropping effect and has been widely used in flame retardant PC/ABS and other materials, but there are few research reports on PTFE in flame retardant ABS. The common ABS flame retardant in the industry, while introducing PTFE, discussed the effect of PTFE on the performance of flame retardant ABS.
1. Experimental part
1.1. Main raw materials
ABS, brominated triazine, antimony trioxide, PTFE, antioxidants, lubricants, etc.
1.2. Main equipment
Twin-screw extruder: SHJ-35 type; injection molding machine: T80 type; computer-controlled electronic universal testing machine: CM6104 type; thermal deformation temperature measuring instrument: 303; thermogravimetric (TG) analyzer: 209C type. Pendulum impact tester: Model ZBC-25B; Melt flow rate (MFR) instrument: MPXRZ-40A; Horizontal and vertical combustion tester: Model HVR-2.
1.3. Sample preparation
Dry ABS at 80℃ for 3 to 5 hours, then mix ABS, brominated triazine, antimony trioxide, PTFE, and other additives uniformly, melt and blend through a twin-screw extruder for extrusion and granulation. Extrusion temperature is 215-225℃, screw speed is 360 r/min; then it is blown and dried at 80℃ for 2 hours, then injected into the standard sample, injection temperature is 200～210℃.
1.4. Performance test
Combustion performance: tested according to UL94; tensile performance: tested according to GB/T 1040-1992; bending strength: tested according to GB/T 9341-2000; impact strength of cantilever notch: tested according to GB/T 1843-1996; MFR: according to GB/T 3682-==2000 test, temperature 220 ℃, load 220kg; heat distortion temperature: test according to GB/T 16341-2004; TG analysis: heating rate 10. C/min,. The temperature range is 30 ~ 700 ℃, under nitrogen atmosphere.
2. Results and discussion
2.1. The sample without flame retardant completely burns after the first ignition, and the flame retardant effect is poor. When a certain amount of brominated triazine and antimony trioxide flame retardant is added, the flame retardant effect is obviously improved, and the flame retardant level reaches the UL94V-2 level, but the burning time is longer, and the flame retardant effect is still not ideal. The addition of PTFE significantly shortens the burning time of the material. When 0.2% PTFE is added, the flame retardant level of the material is increased from V-2 to V-0. This is because PTFE has a high melting point (323°C), and it does not melt at the material processing temperature, but it is easy to fibrillate to form a fiber network under the blending shear force, which reduces the spread of flame.
2.2. After adding the flame retardant, the notched impact strength of the material drops sharply, while other mechanical properties change little. In contrast, when flame retardants and PTFE are added at the same time, the toughness of the material is slightly improved compared with the use of flame retardants alone, and as the amount of PTFE increases, the notched impact strength of the material also increases, which may be The fiber network structure formed by PTFE in the material plays a reinforcing role to a certain extent.
2.3. As the amount of PTFE increases, the MFR of the material gradually decreases. When the amount of PTFE added is 0.3%, the MFR of the flame retardant ABS decreases from 23.1g/10min to 14.5g/10min, indicating the effect of PTFE on the flow properties of the material. The larger one is mainly due to the existence of PTFE fiber-forming material, which hinders the flow of ABS molecules. Due to the special structure formed by PTFE during processing, the material strips appear to swell at the exit of the material strip, resulting in thicker material strips and slower pelletizing. Extrusion of materials without PTFE is more normal.
2.4. TG and DTG analysis of materials
There is only one peak of thermal weight loss in the process of thermal weight loss of pure ABS, and two peaks of thermal weight loss appear in the process of thermal weight loss of flame retardant ABS. The first peak is caused by the decomposition of flame retardant, and the second peak is caused by the decomposition of ABS. With the addition of PTFE, the peak thermal weight loss temperature (427°C) of ABS is 1.8°C higher than that of pure ABS (428.8°C), but the peak differential thermal weight loss rate (mass heat loss rate) (11.7%/min) is only The peak differential thermal weight loss rate of pure ABS (18.8%/min) is 62.2%, which is 7.9% lower than the peak differential thermal weight loss rate (12.7%/min) of sample 28 without PTFE added. The addition of PTFE can improve the flame retardant performance of the material.
Bromotriazine and antimony trioxide are typical halogen-antimony flame retardants, which not only change the gas phase flame retardant reaction but also change the thermal degradation reaction of the condensed phase. The residual carbon rate of pure ABS at 700℃ is 1.2%, and the flame retardant ABS with brominated triazine and antimony trioxide is added. The residual carbon rate at 700℃ is 3.5%. The formation of the carbon layer also helps to increase the resistance of the material. Ignitability. At the same time, the residual carbon rate at 700°C with PTFE added was 3.6%, indicating that PTFE failed to promote carbon formation. The addition of PTFE may promote a denser carbon layer structure and better insulation and oxygen barriers, thus Used with halogen-antimony flame retardant, the flame retardant effect is more excellent.
3. Conclusion
3.1. The addition of PTFE can further reduce the peak thermal weight loss rate of the flame retardant ABS, significantly reduce the burning time of the material, and improve the flame retardant grade of the material.
3.2. The addition of PTFE has little effect on the mechanical properties of flame retardant ABS, and to a certain extent improves the toughness of the material.
3.3. PTFE has a significant effect on the processing performance of flame retardant ABS materials, and the dosage should be adjusted according to needs during the use.
Post time: Jun-11-2020