Surface Modification Of Polypropylene Fibre And Its Application In Cement-based Material

Polypropylene fibre is a kind of well-regulated crystalline polymer, which is of many good properties as admixture of cement-based material. While polypropylene fibre is one kind of water-repellent material which has lubricous surface and low surface energy, and whose molecule has not any reactive functional group. When the fibre is added in cement-based material, there will be a problem of fibre's poor performance of dispersion in the matrix arid bad binding capacity between fibre and matrix, which will badly limit application of polypropylene fibre in the field of construction.The author starts with surface modification, and expects to solve the problem mentioned above by introducing hydrophilic reactive functional group into fibre and (or) increasing the degree of coarseness of fibre's surface.In this paper surface modification of polypropylene fibre has been studied deeply, the method and conclusion of surface modification are shown as follows:(1)Treatment by chromic acid: the conclusion shows that such unsubstantial layer as noncrystalline area of PP fibre's surface has been eroded away, concavo-convex grooves fluted in the surface of fibre, and that the degree of coarseness of fibre's surface has been increased. Such reactive functional groups as -COOH and -OH are introduced onto the surface of PP fibre. Fibre's percentage of moisture absorption and content of functional group of fibre's surface have been improved very greatly.(2)Grafting acrylic acid onto PP fibre initiated by KMnO4/H2SO4: the test shows that such reactive functional groups as -COOH are introduced onto the surface of PP fibre, and that the degree of coarseness of fibre's surface has been increased and fibre's percentage of moisture absorption has been improved.(3) Impregnating by the water/ethanol solution of CH2=CHSi(OCH2CH3)3 (SCA-1613): the test shows that the surface of fibre has absorbed some SCA-1613 molecule, and that the PP fibre's percentage of moisture absorption has been improved greatly.(4)Impregnating by the water/ethanol solution of CH2=C(CH3)COOCH2CH2CH2Si -(OCH3)3 (SCA-503): the conclusion shows that the surface of fibre has absorbed some SCA-503 molecule, and that the PP fibre's percentage of moisture absorption has been improved.(5)Grafting CH2=CHSi(OCH2CH3)3 (SCA-1613) onto PP fibre initiated by DCP:the conclusion shows that the SCA-1613 molecule are introduced onto the surface of PP fibre.In order to value the effect of surface modification of polypropylene fibre, the author has designed the crack test to weigh the influence of different fibres. Experimental conclusion shows that modified polypropylene fibre l)(It represents the fibre treated by modification method (1) here, analogizing later), 2), 3) can restrain the plastic shrinkage crack of cement-based material more effectively than unmodified polypropylene fibre.In the end, the author has also studied the influence of modified polypropylene fibre 1), 2) and 3) on fundamental mechanics properties of cement-based material (mortar). Experimental conclusion shows that the reinforcement effect of modified fibre 3) is the best, then in turn, modified fibre 1), 2), and that fundamental mechanics properties of the three kinds of modified fibre reinforced mortar has been improved more greatly than that of unmodified fibre.