Study On Modification Of Polypropylene By Calcium Sulfate / Cellulose Whisker

Polypropylene (PP) with better overall performance,excellent mechanical properties and heat resistance,is non-toxic,no-pollution,therefore,it is more and more applicable in the chemical building materials in recent years.But because of its low notched impact strength and low-temperature impact performance,it does not meet the various requirements.In order to improve and enhance the performance of PP and broaden its applications,PP needs to modified reinforcement,especially new fillers,playing an important role.Calcium sulfate whisker and cellulose whisker are green,non-toxic and environmentally friendly rod sub-nanometer materials,which can reinforce the polypropylene,so it has theoretical and practical significance for these whiskers to be studied.Atmospheric acidification method was used to prepare calcium sulfate whiskers by using a kind of salt waste brine enriched in calcium chloride and acid hydrolysis method was used to prepare cellulose whiskers,and the factors that influence the aspect ratio of cellulose whiskers was discussed.The optimal condition obtained for the preparation of calcium sulfate whiskers reaction was temperature70℃,pH value2,rotation speed150r/min,concentration lmol/L,the reaction time30min.Optimal conditions for preparation of cellulose whiskers was1mol/L sodium hydroxide solution soaked cotton2h,the reaction temperature60℃,the solvent1:12,the reaction time40min,otation speed160r/min,the concentration of sulfuric acid55%.IR was used to verify the composition.XRD and SEM were respectively used to characterize the micro-structure.The results turned out that crystallinity of calcium sulfate whiskers was80%which was higher than the cellulose whiskers36.5%.The average diameter and length of both kinds of whiskers were measured by SEM with calcium sulfate whiskers average diameter1-5μm,length20-100μm and length-diameter40,while cellulose whiskers with length0.5-1μm and diameter50-100μm, respectively.Cellulose whiskers,calcium sulfate whiskers with length-diameter ratio of20,40and polypropylene were used to prepare composite materials by melt extrusion and injection,in order to study the effect of two whisker on modifying the polypropylene.The results show that: when calcium sulfate whiskers content reaches9%and length-diameter40,PP performance was the best,and it improved the PP tensile strength from27.5MPa to29.2MPa,the elongation at break from281.9%to360.8%,the impact strength from6.1kJ·m-2to8.2kJ·m-2,shaw hardness from86to96.3.PP improved heat resistance from420.4℃to425.6℃and the mass loss is reduced by2.3%.KH-550can be used to improve the dispersion of calcium sulfate whisker,and can enhance its performance;Polypropylene also had some reinforcing effect by cellulose modified.When CW content reaches5%,PP performance was the best,and it improved the PP tensile strength from27.5MPa to28.9MPa,the elongation at break rate from 281.9%to300.5%,impact strength from6.1kJ·m-2to7.6kJ·m-2,shaw hardness from86to95.6.PP improved heat resistance from420.4℃to428.5℃and the mass loss is reduced by2.9%;But when combined these two whiskers,the result was unsatisfied.The tensile strength of polypropylene,elongation at break, impact strength and hardness were lower than that of single whisker.The reason why these two kinds of whiskers can modify polypropylene is due to whisker’s pull up effect that matrix crack propagation process, and the mechanism is related to the consistency between the whiskers and polypropylene.