Investigation of the usability of hemp fibres doped with boron compounds in the production of building materials for insulation purposes

In order to reduce the need for artificial materials in architecture, the use of plant-based materials is becoming more important day by day. Also, the use of natural materials is limited, and due to the increasing environmental awareness in today's designs and the orientation towards materials suitable for human health, the studies on the development of these materials are increasing. In terms of strength, durability, thermal and acoustic properties of hemp fibers have a high potential for use as plant-based building materials. However, it is significant to increase the usage area of hemp fiber by improving its properties. In this study, it was aimed to increase the resistance against fire and biological pests with boric acid solution doped hemp fibers in different concentrations and to develop building materials with heat and sound insulation properties by using these fibers. The internal structural properties of the fibers were investigated by field emission scanning electron microscopy, and their thermal behavior was investigated by thermogravimetric and differential thermal analysis. Samples were prepared by mixing undoped hemp fibers, hemp fibers doped with 10% and 15% concentrated boric acid solutions and lime binder separately. The fiber:binder ratio is 1:4 by weight in all samples. To determine the heat and sound insulation properties of the samples; thermal conductivity test with heat flow plate method, sound absorption and sound transmission loss tests with impedance (Kundt) tube method were conducted. According to the analysis results, the thermal conductivity coefficients of the samples produced using hemp fibers, which are undoped, doped with 10% and 15% boric acid solution, were determined as 0.0935 W/mK, 0.1926 W/mK and 0.1863 W/mK, respectively; average sound absorption coefficients were measured as 0.33, 0.38 and 0.32, respectively; the average sound transmission loss values were recorded as 24.02 dB, 17.74 dB and 12.13 dB, respectively. The highest sound transmission loss value is 46.92 dB which belongs to the sample containing hemp fiber doped with 15% boric acid. This value indicates that this material can be used in the production of sound insulation material. In addition, while a higher coefficient than the thermal conductivity value, which is required for thermal insulation materials, was obtained; it is possible to reduce this value by changing the type and amount of binder used and the production method, thus it is important to develop studies in this direction. KEY WORDS: Plant-based building materials, Hemp fiber, Boron compounds, Insulation material