Study On The Preparation Of Surface Polarity Fiber And Reinforced Modification Of Cementitious Composites

Cement is the building materials which the largest amount application and the mostwidely used in human society. Cement-based materials has a high compressive strength, butthere are disadvantage that it is easy to occur plastic cracking in the process of use, whichgreatly affected the life and properties of cement-based materials.The fiber as a reinforcingmaterial for cement-based materials can effectively increase the tensile strength, impactresistance and resistance to bending performance of cement-based materials. And it cancontrol or reduce crack generation and propagation on solidification and use of cement-basedmaterials to prevent cracks and water infiltration of the cement-based materials and to preventthe corrosion of steel components. Polypropylene fiber which have excellent crack resistanceperformance are widely added to cement-based materials. But the polypropylene fiber whichhas no polarity and low the surface energy, it is difficult mix evenly in the cement, and it donot have good adhesion too, so polypropylene fiber must pass modification before applicationof it in cement-based materials.In this paper, polypropylene resin prepared surface polarity fiber by surface modificationand blending modification. Characterize the surface polarity fibre by using the infraredspectroscopy, polarized light microscopy, material testing machine, the dynamic contact anglemeasuring instrument, scanning electron microscope and the determination of fiber weightloss rate, grafting ratio, moisture absorption rate. The polarity fiber mixed into cement-basedmaterial, to enhance the cement-based material. Specific research contents are as follows:(1) Using the horizontal screw extruder preparated polypropylene fiber. Fiber diameter,strength and other properties were identified by characterizing the fiber by using test methodssuch as polarizing microscopes and material testing machine. The most type of polypropyleneresin which was found out was PP S1004for this study.(2) Preparation of surface polarity fiber by chemical oxidation. Polypropylene fiber wasoxidized by chromic acid at different treatment conditions. The best oxidation treatmentmethod which was selected was Chromic acid commonly used in industrial formulations,soak2.5h at room temperature and reaction13min under the conditions of70℃. (3) Grafting of butyl methacrylate and acryli cacid by UV. The main factors of thetransformation is grafted environment, monomer concentration, photosensitizer mass ratioand the time of ultraviolet irradiation. The optimal graft method by comparing the fiberstrength, surface roughness, wettability, contact angle was determined. Monomerconcentration was0.8mol/L and photosensitive agent accounted for monomer quality scoreswas1.4%and purple outside light irradiation time was2min when methyl acrylate wasgrafted; monomer concentration was0.8mol/L and monomer mass fraction ofphotosensitizers was1.1%and UV-irradiation time was5min when acrylic was grafted.(4) Preparation of surface polarity fiber modified by blending. Compatibilizer wasmelt-grafting of itaconic acid on polypropylene resin, and then it was mixed into smallamounts of polyvinyl alcohol resin and polypropylene blends. The best proportion betweenthe pp: polyvinyl alcohol: polypropylene melt grafting of itaconic acid (PP-IA) which wasdetermined was100:3:5by comparing the fiber strength, surface roughness, moistureabsorption and contact angle.(5) Surface polarity fibers which were preparated were added to cement to study onenhancement modification of cement-based materials. The best method of preparating surfacepolarity fibers which was determined was blending modification. The fracture resistance andcompressive strength reached the maximum sample value when mixing amount of the fiberreached1.00%of the quality of the cement. At this time, bending strength of3d increased by53.81%and compressive strength of3d increased by14.51%; at7d, the bending strengthincreased by53.14%and compressive strength increased by10.54%.In this paper, various properties of domestic fiber were studied. Tensile strength, elasticmodulus, density, and the alkali resistance properties of domestic fiber meet the requirementswhich were the standard of ideal of cement-based materials. But its surface chemical bondingand fiber diameter still needs improvement. Wet spinning machine which was designed in thispaper can be used for the modification of the diameter and thesurface chemical bonding.