Study On The Coating Modification Of Basalt Fibers And Their Chemical Stability Performance

Basalt fiber is a new inorganic fiber appearing in recent years, which has realized industrialization in China. However, there are still many ascendant potencials in its product quality and technical process. This research focuses mainly on the fiber's performance and microscopic microstructure as well as its surface modification technology, in order to fully understand the new fiber and provide data and theoretical support for further extending its application fields.In the present work, the continuous basalt fibers'basic structure, performance, chemical stability and microscopic fine structure were investigated. Based on this, the basalt fibers were modified by coating technology. Meanwhile, the modified basalt fibers'mechanical properties, chemical stability, interface performance and basalt fiber reinforced composites'chemical stability were also analyzed. Furthermore, the corresponding mechanisms were studied.The results showed that the composition of the basalt fiber was relatively complicated and there was a hygroscopic phenomenon existing on the fiber surface. The basalt fiber surface free energy was larger and the polarity portion occupied the main part. The strength distribution rule of the basalt fiber fited weibull distribution law and its diameter distribution conformed generally to the normal distribution law. There are still lots of room for its growth in performance stability. Basalt fibers have good chemical stability and their acid resistance is much higher than their alkali resistance. The basalt fibers and their reinforced composite could be used in a chemical environment for long-term service, especially in an acidic environment. Basalt fibers'corrosion mechanisms are different in different media. Under an acid environment, the network modifier elements in the basalt fibers were leached out from their surfaces. With the extending of treating time, there were cracks appearing and extending along the axial direction, and also extending into the interiors of the fibers at the same time. In the later period of treating, the damaged surfaces were partially healed. Under the conditions of strong alkali, the chemical reactions were mainly precipitation of network former elements and the corrosion process is following the layer-by-layer mode. Howerer, under the conditions of weak alkali Ca(OH)2, the case is different. Local corrosion occurred on the basalt fiber surface. The basalt fiber is composed of various chemical compositions. Each component played a special role in the fibers'network structure. The whole basalt fiber existed in an amorphous form and remained at a metastable state. In its microscopic fine structure, there were structure units of [SiO₄]^4-, [Si₂O₆]^4-, [Si₂O₅]^2- and Si-Al substitution existing. The microscopic fine structure of the fiber had a characteristic which was similar to the"plane-liked"structure.Through applying the nanosized SiO₂/epoxy composite coating on the basalt fiber surface, the fibers'mechanical properties and chemical stability were improved a lot. Its tensile strength was increased by ¹5% and its alkali resistance was improved by about 40%. In addition, after the treatment with nanosized SiO2/epoxy composite coating, there were many small particles attached to the basalt fiber surfaces. These particles were uniformly distributed, increasing the fiber surface roughness and thus benefiting the adhesion of fibers to the composite matrix. After modification, the interlayer shear strength (ILSS) of the basalt fiber reinforced composites was increased by ²0%. The size and concentraton parameters of nanoparticles embedded into the coating could directly influence the coating modification effect. As a result, nanocoating modification technology could be widely used in fiber surface modification, paint, chemical engineering fields, etc.Basalt fiber reinforced polymer (BFRP) is a kind of composites with a promising seawater resistance. The results showed that its resistance to seawater was almost the same as that of glass fiber reinforced polymer (GFRP), and therefore it could be widely applied to marine and shipbuilding fields. It is suggested that an effective lowering of the Fe content in the basalt fiber could lead to a higher stability of BFRP in seawater environment.