Preparation And Research Of Micro/Nanocellular Polypropylene Foam

Microcellular polypropylene?PP?,a new kind of foam material,has many advantages than unfoamed,such as good toughness,light weight,high strength and heat insulation,etc.But there are many difficulties to prepare microcellular PP,and the preparation device of microcellular PP must use expensive and special equipment.So this paper aimed at applying ordinary Injection Molding Machine to prepare microcellular PP by refining the foaming agent particles.First,cheap and nontoxic sodium bicarbonate?NaHCO₃?was chosen as a blowing agent,refined by anti-solvent recrystallization method.And then modified the thermal properties of the refined NaHCO₃.Second,the most suitable PP foam matrix was determined from four kinds of expansion PP,according to dynamic rheological properties,cells morphology,etc.Finally,the influence of foaming agent on PP microcellular was studied.The main conclusions are as follows:1? The average particles size of refined NaHCO₃ is 143.2 nm,with a narrow size distribution.NaHCO₃ mass concentration is 10 %,the volume ratio of water and ethanol is 1:14,the speed of stirring is 1100 rpm,the preparation temperature is-5?,the feed rate is 1 mL · min-1 were determined the optimal preparation conditions.2 ? Compared with the cells size of PP microcellular obtained by commercial NaHCO₃,the cells size of PP microcellular which obtained by refined NaHCO₃ was significantly reduced from 100 ?m to a few hundred nanometers.3 ? Tested by Rheometer,the Storage modulus?G??and loss modulus?G???of PP4 were higher than the other three kinds of PP.So PP4 is the most suitable foaming matrix in theoretically.Actually,microcellular PP prepared by PP4 had better cell structure.The average cells size is only 0.45 ?m,the Standard Deviation 0.17 ?m,which visually indicated that cell size was uniformity.Cell density reached 2.37× 1010 cell / cm3.4?Adding the refined NaHCO₃ into PP4 to prepare microcellular PP,NaHCO₃ amount from 1.5 parts to 9 parts.The results show that better cell quality,which the minimum average size of microcellular PP is 0.44?m,the maximum only 0.54 ?m,the cell density reached 3.92 × 1010 cell/cm3.The density of PP microcellular was down to 5.65 % with constantly.The microcellular PP remained excellent mechanical properties than the unfoamed,which the tensile properties decreased slightly,while the impact strength enhanced 47.8 %?4.5 phr?and the flexural modulus enhanced 20.2 %?4.5 phr?.In short,microlcellular PP showed the best comprehensive properties when NaHCO₃ in an amount of 4.5 parts.5 ? In this study,excellent cell structure and good properties microcellular PP was prepared by ordinary Injection Molding Machine,which have a significant effect on research of microcellular in the future.