Preparation And Properties Of Polypropylene Modified By Additive Melt Blending

Polypropylene(PP)is one of the most widely used semi-crystalline resins.With the improvement of the properties of PP,the research on nucleating agents and related auxiliaries of PP has attracted extensive attention.However,due to the influence of molecular weight,molecular weight distribution,structure and density of polypropylene,the application of polypropylene as mechanical material is limited to a certain extent.In numerous nucleating agent modification methods,using one or two kinds of nucleating agent distribution is the common way of modification,the modification effects of but in general,and part of the nucleating agent cost is higher,to the enterprise to produce cost problem caused great distress,therefore,in order to improve the performance indicators of polypropylene,at the same time considering the modification of the cost of the enterprise to produce in the process of product,Modification of polypropylene with a variety of nucleating agents and independent synthesis of in-situ anti-thermal oxygen aging agents has become a choice more in line with the production benefits of enterprises.In this paper,different additives,including several categories of nucleating agents and anti-thermal oxygen aging agents synthesized by metal powder,were used to blend or graft polypropylene.The mechanical properties,optical properties and other modification effects were investigated.The specific content is as follows:(1)The mechanical properties,optical properties and other modification effects of the modified polypropylene samples were investigated by using six nucleating agents.The results showed that:(1)In terms of mechanical properties,the impact strength of the simply supported beam was the highest in the 31 tests with the combination of six nucleating agents,which reached 76.6 kJ/m~2.Compared with the three inorganic nucleating agents,the modification effect was increased by 17.48%,and the tensile strength reached the maximum of 36.4 MPa,which was increased by 45.6%compared with the initial three inorganic nucleating agents.The bending modulus of T30 test is up to 1340 MPa,and the modification effect is 48.5%higher than that of three inorganic nucleating agents.The maximum bending strength reaches 28.5 MPa,which is increased by 22.84%,and the nucleation modification effect is obvious.(2)In the comparison of melting and crystallization behavior,the melting temperature of T31 test reached 165?and the crystallization temperature reached 132?,which were 11?and 22?higher than the initial three inorganic nucleating agents,respectively.(3)On the cross section morphology analysis,the combination of the three kinds of inorganic nucleating agent attached to the surface more dark hole,three kinds of organic nucleating cross section on SEM diagram,dark hole decreased significantly,add after six kinds of nucleating agent,significant changes have taken place in its morphology,its become bright and smooth surface,mainly reflected in the surface hole density reduced or even disappear.(4)In the modification of light transmittance,hazy degree and yellow index,the modification effect of six nucleating agents composite modification is much more obvious than that of three inorganic and three organic nucleating agents.T23 experiment hazy degree value reaches the lowest 40%,which is 55.8%lower than that of three inorganic nucleating agents modification.As for the overall modification effect,the light transmittance fluctuates around 70%.With the combination modification of six inorganic/organic nucleating agents,the yellow index value reached the lowest value,which reached 0.4,0.5 and 0.4 in T29,T30and T31 experiments,respectively,and the decreasing multiple reached 85.71%,82.14%and85.71%,respectively.(2)Two kinds of stearates were synthesized by in-situ method.The effects of the two stearates on the mechanical properties,melting index and oxidation induction period of polypropylene were studied.The results showed that:(1)With the increase of calcium stearate,the bending modulus and tensile strength reached the maximum,which were 1425 MPa and38.7 MPa,respectively.Compared with 400 ppm,the bending modulus and tensile strength increased by 16.99%and 32.35%.The impact strength decreased to 6.23 kJ/m~2,which was50.63%lower than 12.62 kJ/m~2when the dosage was 400 ppm.The modification of polypropylene melt index by in situ synthesis of calcium stearate was tested by different times of extrusion.The maximum change rate of melt index was 83.13%with the increase of calcium stearate added in one extrusion.The maximum change rate of melting index is76.39%during the secondary extrusion.The maximum change rate of melting index is77.27%during three extrusions.(2)The bending modulus and tensile strength of in-situ synthesis of Stevenson At reached the maximum,1403 MPa and 38.5 MPa,respectively,while the impact strength decreased to 6.21 kJ/m~2,compared with 12.59 kJ/m~2at 400 ppm.That's a 50.68%decrease.In terms of modification of melt index,the maximum change rate of melt index is 81.30%with the increase of Ste-At content in the first extruder,74.66%in the second extruder and 67.29%in the third extruder.(3)With the increase of Ste-At/calcium stearate addition,the oxidation induction time of polypropylene increased first and then tended to be flat.