Studies On PA66/PHE Blends

Polyamide 66 (commonly known as nylon 66) is an important engineering plastics with high strength wear resistance, corrosion resistance, self lubrication and outstanding fluid processing properties. However, strong water absorption affect the processing properties and dimensional stability because of its rich of polar groups limited its application. In order to improve the integrated property of nylon 66, polyamide 66/poly(hydroxy ether of bisphenol A) (PHE) blends were prepared by a dual-screw extruder in the whole composition range. PHE with different sizes of raw materials were adopted in this research. The PA66/PHE blends were characterized by DSC, WXRD, POM, SEM and so on. The results show that the different size of original PHE and processing conditions remarkably affect the morphology and mechanical properties of PA66/PHE blends while have no influence on the crystalline of the blends.The investigation of the morphology and the mechanical properties of blends showed that the addition of PHE changed the morphology of PA66/PHE blends:from continuous phase-disperse phase to co-continuous phase. When smaller PHE particle is used as the original material, the phase size of PA66/PHE blends are more small and the dispersion and distribution are more homogeneous. The processing conditions can also affect the phase morphology. We find that under the stronger shear force the disperse phase of PA66/PHE blend are smaller.When PHE with small particle size (remarked as PHE-S) was used, the impact and tensile strength of PA66/PHE blends were improved by the addition of the PHE, and presented synergistic effect. When PHE with big particle size (remarked as PHE-B) was used, the impact strength of blends was reduced, but the tensile strength of blends was elevated even higher than that of the corresponding blend started by PHE-S. When other conditions are the same, compare to weaker shear force, stronger shear force leads to better mechanical properties, particularly at low PHE content.The melting and crystallization behaviors of PA66/PHE blends were also investigated in this work by differential scanning calorimetry (DSC), Wide-angle X-ray diffraction (WXRD) and Polarizing optical microscope (POM). The results showed when the content of PHE is below 10%, with the increasing of PHE content the crystallization temperature of blends decreased and the size of PA66 crystal were reduced. When the content of PHE is higher than 10%, the crystallization temperature then decrease with increasing of PHE content. The reasons may be that at low PHE content, the PHE was a good nucleating agent, which could evaluate the crystallization rate of PA66, shorten the half-time of crystallization, increase the crystallization temperature, and reduce the size of PA66 crystal; at high PHE content, the morphology of PA66/PHE blends is inversed, the PHE could hinder the crystallization of PA66, reduce the crystallization rate of PA66, which prolong the half-time of crystallization, and enlarged the size of PA66 crystal. The addition of PHE also reduced the melt temperature of blends, which result from the dilution effect of PHE that reduced the degree of PA66 crystal. The result also showed that the addition of PHE promoted the growth ofα2 crystal, and hindered the growth ofα1 crystal.