The Study Of Barrier HDPE/PA Materials

As one kind of Universal Plastics, High-density polyethylene (HDPE) possesses a wide range of resources, low price and good comprehensive function. However, due to its non-polar polymers, solubility parameters and the majority of hydrocarbons organic solvents is similar, thus the permeability of these materials which is resistant to organic solvents is poor, and nylon (PA) with excellent performance, good oil resistance. Through the preparation of HDPE and PA blends, it can improve the resistance of HDPE infiltration performance of organic solvents, but also it can improve the mechanical properties of HDPE, which is conducive to further broaden the application areas of HDPE. The different polarity between HDPE and PA resulted in bad compatibility. Therefore, the compabilizer was used to improve the compatibility. In this paper, the HDPE/PA blends were prepared,using HDPE-g-MAH (CP)as compatibilizer in melting blend. In order to improved its barrier properties, HDPE/PA composites were produced by extruding mixture and their mechanical properties, barrier properties, morphology structure, rheological behavior and crystallization properties were investigated by scanning electron microscopy (SEM), X-ray diffraction (WAXD), differential scanning calorimeter (DSC) and polarizing microscopy (POM). At the same time, effect of the different types of PA on barrier HDPE / PA materials at different HDPE/HDPE-g-MAH /PA blends was studied.The research of preparation conditions and mechanical properties show that for the HDPE/PA6 blends, shear rate to be about 92S-1 is appropriate. Furthermore, the sample temperature should be taken control of about 220℃in order to make modified PA component in the distribution of HDPE in the form of a layered structure. Under the same conditions of the compatibilizer content (HDPE-g-MAH/HDPE = 5%), with the increasing of the PA content, tensile strength, impact strength has increased and then decreased. In the PA content (PA / HDPE =15%), the tensile strength and impact strength reach the highest point.In the Nylon content (PA / HDPE) = 5%), for the PA6/HDPE blends, when the compatibilizer content is about 10%, the tensile strength and impact strength of the blends reach the maximum; for the PA11/HDPE blends, when the compatibilizer content is 2% ~ 5%, the tensile strength and impact strength of the blends reach the maximum.Effects of the PA contents on barrier properties of PA/HDPE blends are investigated and show that under the conditions which are in the amount of compatibilizer(HDPE-g-MAH/HDPE =15%), when PA6 contents is 15%, barrier property of PA6/HDPE blends is 3.58 times as bigger as that of the pure HDPE; while PA11 contents is 10%, barrier property of PA6/HDPE blends is 2.97 times as bigger as that of the pure HDPE. When w(HDPE/HDPE-g-MAH/PA11) = 100/5/2 , barrier properties of these blends reach the optimum. Simultaneously, SEM analysis showed that the PA was in the form of discontinuous mutual crossover laminar structure dispersed in HDPE, which played a key role in improving the barrier property.The rheological behavior of HDPE /HDPE-g-MAH/PA composite was investigated. The result shows that HDPE / HDPE-g-MAH/ PA composites are pseudo-plasitc. With the addition of compatibilizer, the sensitivity of HDPE / PA composites to shear rate enhances. At the same time, with the increasing of the content of compatibilizer, the apparent viscosity of HDPE/HDPE-g-MAH/PA11 composites is declining, when compatibilizer content is 2%, the apparent viscosity reachs the largest; However, the apparent viscosity of HDPE/HDPE-g-MAH/PA6 has increased and then decreased as a whole.when compatibilizer content is 8%, the apparent viscosity reachs the largest. The decreasing apparent viscous activation energy of composites indicates that the influence of processing temperature on composites decaresed.The non-isothermal crystallization melting behavior of HDPE and HDPE / PA barrier materials is studied as using DSC and found that melting point and crystallization temperature of HDPE / PA composites have increased with compared to pure HDPE; as compatibilizer (HDPE-g - MAH) content has increased, melting enthalpy of HDPE / PA composites first increased and then decrease. Namely compatibilizer content is 2%, exothermic enthalpy and crystallinity of HDPE/PA6 composites reached the maximum, which is consisted with the best barrier properties point. And it indicates that the more large crystallinity of HDPE/PA6 composites, the more conducive to the formation of barrier layers, the lower the penetration rate in order to be more effective to improve the barrier properties.In different systems of PA6 or PA11, the addition of PA in HDPE matrix, it has shown that melting peaks of HDPE and PA is close to each other; and in HDPE / HDPE-g-MAH / PA blends, melting peaks and crystallization peaks of PA disappear, which shows that effects of PA types on HDPE / PA composites is the same.