Particles Characterization And Expansion Process Of Quercus Variabilis Cork

Cork is a renewable environmentally friendly material with a series of excellent characteristics such as low density,good compression resilience,sound absorption,sound insulation,moisture resistance,insulation and wear resistance.Cork is usually processed into cork particles,which are used to produce all kinds of agglomerated cork in China.Therefore,it is of great significance to study the characteristics of cork particles to improve the quality of cork products in China and develop high-grade cork products.In this paper,the cork particles from Quercus variabilis BL in Qinba mountain area of Shanxi Province was taken as the research object.The main surface and physical properties,combustion characteristics,antifungal properties of extracts and expansion test were studied by laser particle size analyzer,dynamic moisture adsorption analyzer,cone calorimeter and other technical means.The main research results were as follows:(1)As the mesh of cork particles increases,the shape of cork particles tended to be regular.Under the scanning electron microscope,the cork particles had different shapes and uneven surfaces.A large number of cork particles were cut open,leaved broken cell cavities and torn cell walls.The surface lightness(L *),red-green index(a *)and yellow-blue index(b *)of cork particles were 43.38,13.55 and 26.7 respectively.(2)The average longest diameter sizes of 4～6 mesh,8～10 mesh,12～16 mesh and20～40 mesh cork particles were 5.82 mm,3.45 mm,2.56 mm,0.86 mm.The size of 60～100mesh cork particles was in the range of 0～800 μm,the median particle size was 262.98 μm,and the particle size was more in the range of 283.70 μm～320.54 μm,accounted for 9.89%.(3)The tapped bulk density of cork particles was significantly greater than loose bulk density.In the range of 8 ～ 100 mesh,the bulk density and weight gained ratio of cork particles increased with the increase of mesh.(4)Cork particles had obvious hygroscopic hysteresis.Cork particles moisture absorption equilibrium moisture content increased with increasing humidity,and desorption equilibrium moisture content decreased with decreasing humidity.The GAB model predicted the moisture content of cork particles when they reach equilibrium under certain ambient temperature and relative humidity.(5)With the increased of radiant power,the ignition time,peak arrival time and total burning time of cork particles and cork boards were shorter,and the peak heat release rate(pk HRR)became larger with the increase of radiant power.The total release heat andcombustion heat of cork particles and cork board also increase with the increase of radiation intensity.(6)The three extracts of methylene chloride,absolute ethanol and distilled water had no inhibitory effect on aspergillus niger.The components of methanol-sodium methoxide extract are mainly the monomeric substance of suberin,which had obvious inhibitory effect on the growth of aspergillus niger.(7)Cork expansion test equipment were consist of frame,blasting cylinder,electromagnetic heating group,metering water tank,pneumatic door opening mechanism,safety self-locking mechanism,pressure control system,temperature control system,electrical control system and cork recovery system.The expansion process of cork particles included: instrument inspection,parameter setting,feed sealing,heating and water boosting,pressure holding,flash explosion puffing and collection.(8)The volume of expansed cork particles increased significantly,and some broken particles were also produced.The tapped bulk density and loose bulk density of cork particles had obviously decreased.The color of the cork particles had changed significantly,turning into a dark tan.The surface brightness(L *),red-green index(a *)and yellow-blue index(b *)of cork particles decreased by 35.58%,49.00% and 26.52%,respectively.The color difference ΔE value is 18.13.