Preparation And Mechanical Properties Of Cellulose Microspheres For Column Fillin

With the progress of society and the development of science and technology,people’s demand for the quality of material life is increasingly higher,and the demand for materials is also increasing.Column filling materials,as a separation and purification material,have applications in the fields of pharmaceutical research,biotechnology,fine chemicals,and food analysis.Currently,column filling materials are mainly divided into three types: inorganic materials,synthetic polymer materials,and natural polymer materials.Inorganic materials have limited applicability;synthetic polymer materials,although widely applicable,have high preparation costs and require non-renewable resources.Natural polymer materials,such as glucan,agar and chitin,have renewable sources and are non-toxic and harmless,making them a promising alternative to synthetic polymer materials.As a natural polymer,cellulose is widely available and ubiquitous in nature,and it is inexhaustible as long as it is used rationally,and it has hydrophilic,good mechanical properties,chemical stability and biocompatibility,so it is suitable to be chosen as a column filling material instead of synthetic materials.As a new material,cellulose microspheres not only have the above properties,but also have low non-specific adsorption properties,and have regular shape,adjustable particle size,high specific surface area,simple preparation method and low cost,which are considered as an excellent biomedical column filling material.Cellulose microspheres as biomedical column filling materials,column efficiency is very important,high column efficiency has the following characteristics: 1,the shape of the filling material is regular,2 particle size is appropriate(generally 400 ～ 800 μm),not too large nor too small,and the particle size distribution range is narrow,2,good mechanical properties.Cellulose microspheres are a hydrogel material with high water content(≥ 95%)makes its mechanical properties limited,and it is difficult to withstand the pressure brought by the liquid at high flow rate after filling the column,making it impossible to maintain the prototype,resulting in column blockage,resulting in low column efficiency.In order to improve the column efficiency of cellulose microspheres as column packing materials,this article uses emulsion method to prepare regenerated crosslinked cellulose microspheres with controllable particle size,and controls the mechanical properties of microspheres through physical methods and emulsion protection-in situ polymerization method,intending to be used for medical column filling.The main research contents are:(1)Particle shape regulation of cellulose microspheres: the effects of starting viscosity of cellulose solution,cross-linking agent content,emulsifier dosage,stirring speed,and mass ratio of dispersed phase to continuous phase on the particle size of prepared cellulose microspheres.The effect of different cross-linking agent content on the mechanical properties of cellulose microspheres was also explored to provide basic data for later experiments to enhance the mechanical properties of cellulose microspheres.(2)Physical method to improve the mechanical properties of cellulose microspheres:heat treatment and ethanol treatment of cellulose microspheres with different degrees of cross-linking,and control the aggregation state structure by controlling the water content and the volume fraction of ethanol,and the effect on the mechanical properties after rehydration.The effect of the gap between the microspheres on their mechanical properties was also investigated after the change of the aggregation state structure.(3)Preparation of composite cellulose microspheres by in situ polymerization: The in situ polymerization of polyacrylic acid-cellulose composite microspheres was prepared by emulsion protection,and the effects of volume fraction of acrylic acid on the particle size,morphology,surface hydroxyl group and mechanical properties of the composite microspheres were investigated.The following results were obtained.1.the regulation of cellulose microsphere particle shape: the increase in the starting viscosity of the cellulose solution will increase the average particle size of the microspheres,the starting viscosity will be too large to make the particle size distribution too wide;the increase in the content of cross-linking agent on the average particle size of the microspheres is not obvious,but it will make the particle size distribution larger;the increase in the amount of emulsifier in a certain range will increase the average particle size of the microspheres when more than the average particle size of the impact is not obvious,the particle size The particle size distribution will become wider with the increase of emulsifier;the increase of stirring speed will reduce the average particle size of microspheres;with the increase of mass ratio of continuous phase to dispersed phase,the average particle size of microspheres will increase and the particle size distribution will become wider.In order to make the average particle size of cellulose microspheres at 600 μm with a narrow particle size distribution,the following conditions were determined for the preparation of cellulose microspheres: the starting viscosity of cellulose solution was 2474 m Pa·s,the cross-linking agent content was 3%,the emulsifier content was 1%,the stirring speed was 200 rmp,and the mass ratio of continuous phase to dispersed phase was 3:1.2.The physical treatment of cellulose microspheres has an important effect on the regulation of their mechanical properties,and the mechanical properties of cellulose microspheres have obvious changes after heat treatment and ethanol treatment and rehydration.The mechanical properties of the cellulose microspheres were significantly changed by heat treatment and ethanol treatment with water rehydration,and the mechanical properties of the cellulose microspheres were improved with the reduction of water content.The mechanical properties of cellulose microspheres treated with ethanol were found to be better than those of heat treatment.And the mechanical properties of column filling by sieving different levels of microspheres were tested.Cellulose microspheres with small particle size,small gaps between microspheres and high resistance,are not suitable as filling materials;as the particle size of microspheres increases,the gap between microspheres and microspheres also increases,the resistance is reduced,and the mechanical properties are better;the particle size of microspheres is too large,and the gap between the microspheres is too large,the microspheres do not work;with different levels of The mechanical properties of the filled column were tested with different levels of microspheres: when the mass ratio of particle size <400 μm: 400 ～ 800 μm: >800 μm was 1:2:1,the mechanical properties of the cellulose microspheres of the filled column were the best,and the blockage did not occur when the water flow rate was ≤100 m L/min.3.The in-situ polymerization of cellulose microspheres by soaking in acrylic acid and increases the solid content of the microspheres,thus increasing their mechanical strength.The mechanical properties of the composite microspheres increased with the increase of acrylic acid concentration,and the morphology of the microspheres deteriorated with the increase of acrylic acid concentration.The compressive modulus was increased from 19.3KPa to 648.2 KPa,and the composite microspheres were not deformed at high water flow rates(≥150 m L/min)during the column-filling mechanical properties experiments.This article describes the preparation of regenerated cellulose microspheres using emulsification,and the control of their mechanical properties through physical and emulsion protection-in situ polymerization methods.Microspheres with adjustable particle size and excellent mechanical performance were prepared,providing a new approach for using natural polymer microspheres as filling column materials to improve the column efficiency of medical filling columns.This has the potential to be applied in the field of medical functional filling columns.