Synthesis Of Aminated Polystyrene And Its Hydrophilic Modification To Polypropylene

As one of the world's five synthetic polymer materials,polypropylene(PP)has the characteristics of low price,excellent mechanical properties,colorless,non-toxic,easy processing and so on.Films,fibers,non-manufactured fabrics and sheets made from PP have been widely used in daily life and industrial production.However,due to its strong hydrophobic property,PP is difficult to be widely used in textile,construction and other industrial fields.If the hydrophilic property of PP is improved,the dyeing property and comfort of clothing can be enhanced in textile field.In industrial field,the bonding force with concrete can be strengthened to improve the comprehensive mechanical properties of concrete.Therefore,the hydrophilic modification of polypropylene is of great significance.In our previous studies,PS was synthesized and modified to improve the properties of PP by introducing more amorphous zones,molecular diffusion channel and polar groups into PP,the morphology and structure of dispersed phase in PP matrix were also tuned to improve the dyeability and surface properties of PP fibers.However,the introduction of polar groups of PS made the melting processing of modified PS/PP more difficult.The aminated polystyrene was prepared by using an molecular weight adjusted PS as a template based on our previous studies.The hydrophilicity of PP was improved by tuning the amine group content and morphology of PS-EDA dispersed phase in PP matrix.The main contents and conclusions are shown as blow:(1)Preparation and properties of aminated polystyrene: Low molecular weight polystyrene was prepared based on the basic principle of free radical suspension polymerization.Acylated polystyrene was prepared by F-C acylation reaction.The effect of reaction conditions on the acylation of polystyrene was studied.It was found that the feed ratio has a greater influence on the acylation reaction.Acylation degree reached the highest value when the ratio of catalyst and acylation reagent to PS was 1:0.9:0.9.Complexes formed in the system have almost completely reacted in 2 hours.The degree of acylation is higher when the concentration of reactant is 0.33 mol/L and the reaction temperature is 26 °C.Four kinds of PS-EDA with different amino content were prepared by using acylated polystyrene with different acylation degree as intermediate product.The results of thermal properties of PS-EDA show that the introduction of amino group increased the Tg of polymer.The higher the content of amino group,the higher the Tg.The initial decomposition temperature and the termination decomposition temperature of the modified polymer increase with the increase of the amino content.However,when the amino content is high,the polymer exhibits weight loss at lower temperature because of its strong hygroscopicity.(2)Preparation and Properties of PP/PS-EDA Blends: The crystallinity of PP and PP/PS,PP/PS-EDA blends were studied.It was found that the introduction of modified additives reduced the spherulite size and increased the interface between crystals of PP.It was found that the presence of PS and PS-EDA dispersed phase reduced the melting point of the blend polymer.When the amino content in PS-EDA increased,the melting point moved to low temperature.PS had little effect on the crystallization temperature of PP,but the addition of PS-EDA with different amino content made the crystallization temperature of PP move to low temperature.In addition,the addition of PS and PS-EDA increased the initial decomposition temperature of PP,which is beneficial for the melt processing of PP/PS-EDA polymer blend.The un-modified PS phases can uniformly disperse in PP matrix with spherical dispersed phase particles.In the case of low amino content of PS-EDA,the dispersed phase could be uniformly dispersed as sphere particles in PP matrix.While in the case of high amino content of PS-EDA,the high intermolecular force between PS-EDA molecular made it difficult to break and dispersed in PP matrix,which formed larger particles in PP matrix.Increasing the mixing temperature is beneficial for the PS-EDA phase to rupture and disperse under shear field.At 240 °C,the dispersed phase breaks into fine particles and distributes well in the matrix.FTIR and XPS results confirmed the existence of amino groups on the surface of the blend polymer.The results of surface morphology observation and contact angle analysis showed that the hydrophilicity of the modified PP matrix was not improved significantly when the amino content on the surface was low.The hydrophilicity was improved obviously with the increase of the amino content.The water contact angle of PP is larger when the dispersed phase aggregates into larger particles.When the dispersed phase particles are fine and uniformly distributed,the contact angle of PP decreases significantly.The contact angle of modified PP decreases from 100.8° to 66.3°.With the improvement of hydrophilicity,the application prospect of polypropylene can be predicted to achieve very ideal results.