| Poly(phenylene oxide) (PPO) has advantages such as excellent mechanical properties, thermal stability, electrical insulation, flame retardancy and water resistance, and disadvantages such as high melting temperature and melt viscosity. Polyamide 6 (PA6, Nylon 6) has advantages such as good solvent resistance and processability, and disadvantages like high water absorption, relatively low dimensional stability and heat resistance. Thus PPO and PA6 are blended to get an alloy with comprehensive properties. PPO/PA alloy is widely used in automotives, electronic appliances and medical devices.PPO is an amorphous polymer with low polarity, while PA6 is a crystalline polymer with high polarity. When the two immiscible polymers are melt-blended, PA6 would form the continuous phase due to its relatively low viscosity while PPO would be the dispersed phase. Our experiments result showed the equivalent diameter of dispersed phase was about 3μm on average for PPO/PA6 (30/70) alloy, indicating an obvious phase separation occurred due to their poor compatibility, leading to poor mechanical properties especially low notched impact strength. The compatibilization and toughening of PPO/PA6 alloys were investigated in this dissertation, and the relationship between their structure and properties was studied.Styrene-based polymers have been often used to compatibilize PPO/PA6 and typical examples are carboxylated polystyrene, styrene-glycidyl methacrylate copolymer. Styrene-maleic anhydride copolymer (SMA) with maleic anhydride (MA) contents lower than 8 % was an effective compatibilizer for PPO/PA6 alloys. SMA with a high MA content (21.8 %) was used in PPO/PA6 alloy in this study. The morphology, melting and crystallization were studied by scanning and transmission electron microscopies and differential scanning calorimetry (DSC). The compatibilization mechanism was explored by Fourier transform infrared spectroscopy (FTIR). The comparison of mechanical properties of PPO/PA6 alloy with different SMA content indicated SMA (21.8 % MA) was an effective compatibilizer for PPO/PA6 ally; especially when the content of SMA was 2-5 phr, the alloy achieved optimum mechanical properties, and the equivalent diameter for dispersed phase size decreased from 3μm to below 1μm.PPO/PA6/SMA (30/70/2) alloy has the notched impact strength of 23 MPa. The impact modification is needed to meet the requirement for applications. Here MA grafted styrene-ethylene-butadiene-styrene copolymer (SEBS-g-MA) was used as an impact modifier for the alloy. The morphology, mechanical properties and rheological behaviors of PPO/PA6/SEBS-g-MA/SMA with different SEBS-g-MA and SMA content were studied. The results showed that SEBS-g-MA is an effective impact modifier for the alloy, and its notched impact strength reached 143 J/m at the SEBS-g-MA content of 25 phr. In particular, PPO/PA6/SEBS-g-MA/SMA (30/70/25/2, 30/70/30/2) alloys could still maintain high notched impact strengths (80 J/m and above) at -30 oC, which could greatly enlarge the scope of the using temperature.The competitive reaction of MA groups between SEBS-g-MA and SMA with amino groups of PA6 was found in the PPO/PA6/SEBS-g-MA/SMA alloys. The reaction was studied by two-step extrusion with a different adding order of SEBS-g-MA and SMA. And the addition order of SEBS-g-MA first would effectively suppress the strong reactivity between SMA and PA6, resulting in a material with good performance. The properties of PA6/SEBS-g-MA and PA6/SMA alloys were studied to explore the influence of this competitive reaction on the compatibilization and toughening effect of PPO/PA6 alloys.
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