| As a kind of inorganic mineral filler, anhydrite (A?) possesses high strength and stiffness, good lubricity and friction performance, etc. It has been widely used in numerous applications especially in polymeric composites. In general, the effects of inorganic particles on properties of composites depend strongly on its content, particle size, aggregate size and surface characteristics. In this research, A? was surface modified by different coupling agent and then polyamide 6(PA6)/A? composites were prepared by melt blending. Subsequently, the influences of A? size, content and different coupling agent on properties of composites were investigated. The main contributions are listed as follows:(1) The A? with four different particle sizes (800,1500,2000 and 3000 mesh, denoted as AT?I-800, A?-1500, A?-2000 and A?-3000 respectively) were added to the PA6 matrix to prepare composites by a twin-screw extruder. The effects of A? size and its content on properties of the composites were studied. The results show that both tensile strength and flexural strength of composites first increase with increasing A? content and reach a maximum when A? contents are 15 phr and 20 phr, respectively. The addition of A? causes a sharply decline in the notched impact strength of composites. At the same A? content, the mechanical properties of composites increase with decreasing A? size. The results of DSC indicate that A? could act as a heterogeneous nucleation agent in PA6 matrix and the crystallization temperature of composites notably increases compared to that of neat PA6. Futhermore, the inclusion of A? can lead to the appearance of new PA6 y crystalline form, which can be confirmed by XRD analyses. The crystallization degree of PA6/A?-3000 composites first increases with increasing A?-3000 content and then decreases. When A?-3000 content is 15 phr, the crystallization degree of PA6/A?-3000 composite reaches a maximum. TGA results display that the addition of A?-3000 can better improve the thermal stability of PA6. The contents of A?-3000 have little influence on the thermal stability of composites. SEM images demonstrate that when A?-3000 content is below 15phr, the A?-3000 particles disperse uniformly in the PA6 matrix and the interface adhesion between A?-3000 and PA6 is good. Bases on the above results, PA6/A? composites achieve the best properties with the addition of 15 phr of A?-3000.(2) The A?-3000 were surface modified with KH550, KH560 and NDZ201 respectively, and then PA6/A?-3000 composites before and after modification were prepared by a twin-screw extruder. The effect of different coupling agent modification on properties of composites was studied. FT-IR analysis show that the above three kinds of coupling agent are grafted onto A?-3000 surface by chemical bonding. The results of mechanical tests show thatA?-3000 after modification can better improve the mechanical strength of composites compared with unmodified A?-3000. The modification effect of KH560 is better than that of KH550 and NDZ201. The results of XRD and DSC display that the addition of A?-3000 before and after modification could improve the crystallization temperature and crystallization degree. A?-3000 after modification is more beneficial to promote the appearance of PA6 y crystalline form. TGA results show that the inclusion of A?-3000 modified by KH560 could better improve the thermal stability of PA6/A?-3000 composites. SEM images demonstrate that KH560 modified A?-3000 can not only disperse uniformly in the PA6, but also enhance the interface adhesion between A?-3000 and PA6.(3) The total content of A? can be considered as 100 phr (the actual total content of A? is 15 phr). The content of A?-3000 is 50 phr and the total content of A?-2000, A?-1500 and AII-800 is 50 phr. The A? was surface modified with KH560 and the effect of A? size grading blend on properties of composites was studied using the orthogonal testing method. The tensile strength, flexural strength and impact strength of composites further improve after grading blend. When the weight ratio of A?-3000/A?-2000/A?-1500/A?/800 is 50/10/25/10, the tensile strength and flexural strength of composites are 93.5 and 114.2 MPa, respectively. When the weight ratio of A?-3000/A?-2000/A?-1500/A?/800 is 50/10/25/25, the impact strength of composites is 14.7 KJ/m2. After grading blend, the crystallization temperature and crystallization degree of composites improve and reach a maximum when the weight ratio of A?-3000/A?-2000/A?-1500/A?/800 is 50/10/25/10. In addition, A? size grading blend is benificial to produce PA6 ? crystalline form. |
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