| Filler,as the second largest raw materials,is widely used in papermaking industry to improve paper properties(e.g.,brightness,printability)and decrease production costs,which is beneficial to protecting forest resources and developing low-carbon economy.The properties of paper are various with filling different types of filler.Even the physical and chemical properties of filler are constant,filler distribution can lead to great difference of paper properties.and particle size filler has various properties.To explore the effect of filler particle size and distribution in Z-direction,some research have been done in this paper.Firstly,the effect of particle size and fractal dimension on paper properties was investigated by the methods of mechanical milling and chemical preflocculation.For the fly-ash based calcium silicate(FACS)with large particle size(23.5?m),filler with different particle size was obtained by the method of milling.For precipitated calcium carbonate(PCC)with small particle size(4.8?m),filler with different particle size was obtained by pre-flocculation.The particle size distribution and fractal dimension of original filler and filler in paper was counted and analyzed by software of ImageJ and Matlab.The paper properties filled with different particle size filler was analyzed and compared.Results showed that the filler particle size and fractal dimension of FACS0,FACS1,FACS2,FACS3 was about 18.6?m,15.8?m,8.6?m,3.6?m;1.76,1.74,1.73,1.68,respectively.While filler particle size and fractal dimension in paper was about 18.0?m,15.3?m,8.5?m,3.6?m;1.73,1.72,1.70,1.63,respectively,indicating that the filler didn't aggregate in the process of paper production.Under this condition,the properties of original filler can be used to analyze the effect on paper properties.The tensile strength order of paper filled with different FACS is: FACS1?FACS0?FACS2?FACS3.Filler particle size and fractal dimension have significant effects on paper structure,strength and optical properties.Paper bulk and air permeability increased with the increase of filler particle size and fractal dimension;while the opacity was not.In a certain range,the paper tensile index increased with the fractal dimension and the particle size,and then decreased after exceeding a certain value.The filler particle size and fractal dimension of PCC1,PCC2 and PCC3 was about 18.5?m,11.1?m,4.3?m;1.44,1.59,1.68,respectively.While filler particle size and fractal dimension in paper was about 28.6?m,19.4?m,4.2?m;1.39,1.40,1.68,respectively,suggesting that the properties of PCC1 and PCC2 has changed,while that of PCC3 was not.After filling the PCC1 with bigger particle size and smaller fractal dimesion,the paper optical property and bulk was worse,while tensile strength was better.Secondly,the effect of filler distribution in Z-direction on paper properties was investigated.The radian factor was proposed to describe the shape of filler distribution.Additionally,the effect of radian factor on paper properties was studied.Results showed that radian factor was greatly related with paper bulk,air permeability,opacity,tensile strength,and internal bonding strength.With the increase of radian factor,paper bulk,air permeability,internal bonding strength decreased,while tensile strength increased.When the radian factor was 0,paper has better bulk,air permeability and worse tensile strength.Finally,to increase the paper strength filled with PCC,the co-flocculation of PCC was explored.The effect of composite flocs size on paper properties was investigated.Results showed that the co-flocculation can further improve paper strength on the base of pre-flocculation.When the flocs size was 48?m,the tensile strength of paper filled with preflocculating PCC increased by about 46%,while that of paper filled with composite flocs formed at the ratio of 1:1 increased by about 54% at the filler content of(20±0.5)%. |
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