Preparation And Properties Of High-density Fiberboard From Ground Calcium Carbonate And Wood Fiber

In order to deal with the shortage of large-scale timber raw materials in China’s forestry resources,the wood-based panel industry is booming.At present,ordinary wood raw materials for wood-based panel manufacturing are also gradually showing a trend of supply shortage.In addition,the general wood raw materials are flammable,which limits their use in practical applications.In view of the shortage of raw materials and inflammability of fiberboard in the three traditional wood-based panels,this paper,based on the conventional dry fiberboard manufacturing process,selects calcium carbonate to replace part of wood fiber,and prepares ground calcium carbonate/wood fiber composite high density fiberboard that can be used for composite floor substrate.Firstly,the effects of calcium carbonate addition method,addition ratio and plate density on the physical and mechanical properties of fiberboard were explored.In view of the poor compatibility between calcium carbonate and wood fiber,the coupling agent was used to regulate the interface,and the flame retardant properties of ground calcium carbonate/wood fiber composite high density fiberboard after optimization were studied.The main research contents and results are as follows:(1)The effects of calcium carbonate addition method,calcium carbonate particle size,calcium carbonate addition ratio and plate density on the properties of fiberboard were explored.Firstly,the resin mixed with calcium carbonate was characterized and analyzed.It was found that there was no chemical reaction between calcium carbonate and resin,but the initial curing temperature of resin shifted to low temperature,and the thermal stability of resin was also improved.By observing the surface quality of the plate and measuring the physical and mechanical properties of the plate,it is found that the mixing effect of calcium carbonate and resin is better,and the particle size of calcium carbonate has little effect on the performance of the fiberboard.The effects of calcium carbonate replacement ratio of wood fiber and fiberboard density on the properties of fiberboard were further studied.The results showed that the bending properties of fiberboard decreased significantly with the addition of calcium carbonate,but the internal bonding strength decreased first and then increased with the increase of calcium carbonate replacement ratio.The chemical groups and thermal stability of the fiberboard were characterized and analyzed.It was found that calcium carbonate did not react with wood fiber and resin in the fiberboard,but with the increase of calcium carbonate replacement ratio,the thermal stability of the fiberboard was significantly improved.(2)By improving the interfacial compatibility between calcium carbonate and wood fiber,the negative effect of calcium carbonate on the properties of fiberboard is reduced.The fiberboard with calcium carbonate replacement ratio of 30%and density of 900 kg·m-3 was used as the modification object.The coupling agent addition method,coupling agent type and specific type number were used as variables.The physical and mechanical properties of the modified plate were measured.The following conclusions were drawn:titanate coupling agent can lead to a serious decline in the waterproof and moisture proof performance of the fiberboard,which is not suitable for improving the interface compatibility between materials.The modification effect of coupling agent sprayed on wood fiber surface before sizing was better.KH-560 is the most effective coupling agent for modification.After KH-560 modification,the internal bonding strength of the fiberboard increased from 1.13 MPa to 1.37 MPa,and the 24 h thickness swelling decreased from 6.1%to 5.6%.The modified fiberboard was characterized and analyzed.It was found that the grafting reaction between calcium carbonate and wood fiber in the modified fiberboard was carried out by KH-560,and the interfacial compatibility between the two was enhanced.The wood fiber could combine with calcium carbonate in the resin mixture more closely after sizing.(3)Based on the coupling agent and coupling agent addition method in(2),the hotpressing process parameters of fiberboard were optimized to further improve the physical and mechanical properties of ground calcium carbonate/wood fiber composite high density fiberboard,and the flame retardant properties were tested and evaluated.The orthogonal experiment of five factors and four levels was carried out with hot pressing time,hot pressing pressure,fiber moisture content before paving,sizing amount and coupling agent ratio as variables.The optimal hot-pressing process of fiberboard was found by comparing the physical and mechanical properties of the prepared fiberboard.The test results show that the optimum hot-pressing process of fiberboard is as follows:hot pressing time 8 min,hot pressing pressure 4 MPa,fiber moisture content before paving 8-9%,glue content 14%,and coupling agent ratio 1%.In the cone calorimeter test,compared with the fiberboard without calcium carbonate,the total mass loss,total heat release,total smoke production and total CO production of the ground calcium carbonate/wood fiber composite high density fiberboard in the combustion process decreased by about 26%,33%,48%and 63%,respectively.In the oxygen index and vertical combustion test,the limit oxygen index of ground calcium carbonate/wood fiber composite high density fiberboard is 27.34%,and the flame retardant level reaches V-0 level,which has excellent flame retardant properties.After calculation,the raw material cost of ground calcium carbonate/wood fiber composite high density fiberboard is reduced by about 8.5%compared with that of ordinary fiberboard,which has broad development prospects.