Study On Preparation And Properties Of PA66/HDPE Composites

Polyamide 66(PA66) is semi-crystalline thermoplastic engineering plastics, it has good performance like easy processing, resistant to chemical corrosion, heat-resistant, flame retardant, dimensional stability, etc., it has been widely used in electrical electronics, home appliances, automobiles and machinery and other fields. While its applicationhad be limited, due topoor wear resistance, toughness in engineering plastics fields. High-density polyethylene(HDPE) molecular chains structure is very flexible, and it has a good impact and abrasion resistance. Many people have incorporated HDPE into PA66 matrix to improve the overall performance of PA66. The samples were prepared by melt blending PA66/HDPE composites. All testresults were got from the scanning electron microscopy(SEM), differential scanning calorimetry(DSC) and Raman spectrometer on microstructure morphology, crystalline properties and group absorption peaks of PA66/HDPE composites, respectively.In this thesis, PA66/HDPE binary complex materials was prepared and their performance blends was also studied. The studiesshowed that the tensile strength decreased with the inreasing amount of HDPE, while notched impact strength showed a tendency to decrease firstly and then increase.The observation of the impact fracture surface by SEM showed that obvious “sea-island” morphology, and this means two phases were immiscible. Besides, obvious improvement was observed after add HDPE, and then friction coefficient and wear quantity decreased with the increasing of HDPE content. The average friction coefficient was the least when HDPE content was 30 wt%, about 38.6 percentage of neat PA66. Eventually, the PA66 and HDPE weight ratio of 7:3 was determined as the basic formula for the next step accessment of three-element composites.Following confirmed the right mass weight proportion, 7:3, for PA66 and HDPE, the effects of HDPE-g-MAHcontent as the compatible agent on the properties of the composite were researched. The results showed that their tensile strength reached the maximum value when adding 0.99 wt% HDPE-g-MAH, then decreased; the notched impact strength increased with the increase of HDPE-g-MAH content. The notched impact strength reached its maximum value when the content of compatible agent up to 6.54 wt%,which is 2.9 times of PA66/HDPE binary composites, and the wear resistance of composites were improved with increasing the content of compatible agent. The notched impact strength gradually decreasedwhen the content of HDPE-g-MAH exceed 8.25 wt%. The wear resistance of composites were also decreased. Therefore,the content of compatible agent should not be too high, otherwise, materials properties would be deteriorated.The morphology of impact fracture surface was characterized by SEM. The average phase domain size of the dispersed phase HDPE particles gradually decreased with increasing of the content of compatible agent. The interfaces became vague, which means that good interfacial reaction was formed between PA66 and HDPE. It could be contributed to that a strong chemical reaction between carboxyl group exists in maleic anhydride of HDPE-g-MAH and the terminal amino group of PA66. This reaction leaded to the production of the graftcopolymer(PA66-g-HDPE).Glass fiber as reinforcing filler was introduced into PA66/HDPE/HDPE-gMAH alloy after confirming the content of compatible agent. The mechanical properties of the composite had significant improvement with the increasing of glass fiber content. In particular, their modulus can be significantly improved. The reason of this would be their combinition effects, high strength of the glass fiber helps them to with stand stress. The heat distortion temperature(HDT) is greatly improved. HDT of 10 wt% glass fibers added is 3.62 times than that of PA66/HDPE/HDPE-g-MAH.The crystallization temperature of HDPE reduced with the glass fiber because the glass fiber hindered chain motion of PA66 and HDPE molecular, thus, affecting the velocity of their diffusion and migration. Therefore,higher temperature is needed to promote their segmental stretching and movement.