Preparation Of CaCO₃/Wood Composites Its Performance Research

This study using chemical precipitation method and hydrothermal method inside the natural wood to synthesize calcium carbonate in situ to get CaCO₃/wood composite to reduce the flammable characteristics of wood in order to alleviate the present situation of high quality timber resources shortage in China,reach the demand of fast-growing forestry.XRD,optical microscope and scanning electron microscopy?SEM?were used to characterize the structure and morphology of the wood composites.The universal mechanical testing machine for axial mechanical properties of the wood composite was tested.Differential scanning calorimeter?DSC?and CONE were used to investigate the thermal stability and combustion performance of the composite.Concrete research context include:1.Paulownia wood were chosen as the matrix.Different concentration of CaCl₂ and Na2CO₃ solution through vacuum impregnation were purged into the wood to get CaCO₃ / wood composite materials.XRD results showed that at 2? = 30.48 and 44.25 obvious CaCO₃ characteristic peak appeared,and elevated temperature were favorable for the aragonite calcium carbonate type.Optical microscope and scanning electron microscope?SEM?show that wood structure remains untouched,CaCO₃ remained in wood cell cavity and uniform distribution closely to the wood,and is hexahedral,block,particles and long rod shaped.With the increase of preparation temperature,the favorable formation type of calcium carbonate is aragonite.Mechanical test results showed that the composite material of the axial compressive strength,elastic modulus and proportional limit of material are obviously improved.The cone calorimeter tests show that the wood material turned into ash after combustion,and wood composite into charcoal,the heat release rate and total smoke release quantity of composite materials were far lower than the original wood,the composites showed good flame retarding activity and smoke suppression effects.2.Paulownia wood as substrate,vacuum impregnation of urea and calcium acetate mixture,high temperature hydrothermal treatment,the urea hydrolysis produces carbon dioxide,and reacted with calcium acetate within the wood matrix generates CaCO₃,to get CaCO₃ / composite wood.XRD results showed that the 2?= 27.1 and 32.7 and 48.4,appeared more obvious characteristics of diffraction peaks of the calcium carbonate.As the concentration of Ca?Ac?₂ in the precursor solution increases,the characteristics of the diffraction peaks intensity of calcium carbonate,especially aragonite type.Optical microscope and scanning electron microscope?SEM?showed that the micro structure of the wood remained untouched.CaCO₃ distributed uniformly in wood cell cavity and combined to the cell wall tightly,mainly hexahedral bouquets shaped,and the calcium carbonate exists in wood cell cavity inner cavity and intercellular space.Mechanical testing machine test showed that the composite axial compressive strength,elastic modulus and proportional limit ofmaterial,increased by 74.45%,74.45% and 74.45% compared to the original wood.DSC results showed that the composite materials only at about 200 °C has an obvious endothermic peak,other location is not evident in the exothermic peak absorption,better thermal stability and flame retardant effect.3.with Paulownia wood as the matrix,vacuum impregnation Ca?Ac?₂,CO?NH₂?₂ and Mg?NO₃?₂ mixture,CO?NH₂?₂ hydrolyzed into CO₃2 + ion and OH-ions,and combine with Ca2+ ions and Mg2+ ions in wood matrix to produce CaCO₃ and Mg?OH?₂,get CaCO₃/Mg?OH?₂/wood composite materials.XRD results showed that in 2?= 24.1 and 26.1 and 31.7 °,there is an obvious characteristic diffraction peaks of calcium carbonate,there is an obvious peak at 2?=44.6,the magnesium hydroxide characteristic diffraction peak.And as the concentration of calcium carbonate increases,magnesium hydroxide of the characteristics of the diffraction peak intensity is stronger.Optical microscope and scanning electron microscope?SEM?showed that the composite wood internal structure integrity,CaCO₃,Mg?OH?₂ in wood cell cavity were uniformly distributed in the cell wall and combined closely to the wall.Results showed that the mechanical testing machine of the composites under different concentration and temperature are superior to the original wood,and with the increase of concentration and temperature,the axial compressive strength,elastic modulus and the proportional limit increase.The DSC figure show better thermal stability that compared with material composites.