| Preparation of new polymer materials with blending technology has become a hot field of materials research. Polyethylene and nylon are two commonly used engineering plastics with lots of excellent characteristics which other materials do not have. They have been widely used in the actual production. However, due to the polarity of polyethylene, its barrier properties of organic solvents are poor; absorbent of nylon also affects its structural stability and barrier properties. Therefore, adding nylon to polyethylene can improve the barrier properties of polyethylene, and obtain the barrier material with both overall properties.In this paper, grafting of maleic anhydride (MAH) onto high density polyethylene (HDPE), maleic anhydride grafted polyethylene products (HDPE-g-MAH) was performed by melt-extrusion method. The Fourier transform infrared spectroscopy (FTIR) confirmed the existence of grafting reaction. The effect of screw speed, initiator dicumyl, peroxide (DCP), monomer maleic anhydride (MAH), styrene (St) as the second monomer on the grafting rate and the melt flow rate was studied. The results showed that:the grafting ratio increased gradually with the increase of screw speed and then slowly decreased, while the melt flow rate would gradually increase; the grafting ratio increased with the increase of initiator content first and then decreased, and reached the maximum with the initiator content 0.7%, while the melt flow rate of grafting product decreased gradually with increasing initiator concentration; the grafting ratio increased with the MAH content first and then decreased, the optimal monomer content was 3%, the melt flow rate increased with the increase of MAH content; the addition of St could improve the grafting ratio, and when the MAH/St was about 1:1, the grafting effect was the best.Nylon 6 (PA6) was added to HDPE for its modification, which could improve the barrier properties of the latter. But because the polarity of HDPE and PA6 was different, the system of blends was thermodynamics incompatible. So we used HDPE-g-MAH as the compatibilizer applied to HDPE/PA6 to improve the compatibility. Firstly, the improvement effect of HDPE-g-MAH on the compatibility was analyzed intuitively by the Molau test. Then the scanning electron microscopy images showed that the size of dispersed particle became smaller and more uniform with the addition of compatibilizer, thus improved the compatibility of the system. The reaction of anhydride groups and amino end of nylon was proved by FTIR spectra. The compatibilization mechanism of compatibilizer was preliminarily discussed. The mechanical properties of HDPE/PA6 blends were tested, and the results showed that the addition of compatibilizer could significantly improve the mechanical properties of the blends. HDPE-g-MAH with a higher grafting rate would have a better improvement on the compatibility of the blend system.The oil absorption value method and oxygen permeability test were used to test the barrier properties of HDPE/PA6 blends. The results showed that, with the adding of PA6, the oil absorption of materials decreased, and the oxygen permeability was also significantly reduced. The non-polar organic solvent and gas barrier properties of HDPE were improved effectively by PA6. The amount of compatibilizer had a large influence on the barrier properties of blends, with the amount increasing, the barrier properties of blends will first increased and then decreased, and the excessive amount of compatibilizer was not good for the formation of layered structure, which would affect the barrier properties of materials. Appropriate screw speed could play a decisive role in the formation of the layered structure, and the over-high screw speed would make the dispersion excessively refining thus could not form a layered structure. |
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