Preparation And Characterization Of Cellulose Sponge And Its Composite Phase Change Materials

Developing phase-change energy storage materials is of great importance to energy conservation.polyethylene glycol(PEG)is one kind of organic solid-liquid phase change material commonly used at present.In this article,cellulose sponges were first prepared by physical pore-forming method,and then combined with PEG to prepare PEG/cellulose SS-PCMs,which can solve the problem of liquid leakage of PEG and broaden the application field of cellulose sponge.When the mass ratio of cotton and MCC is 1:4,and the total mass fraction of cellulose is 5%,with the increase of the dosage of pore forming agents,the average diameter of stomates will increase in turn;but the structural stability and the tensile strength of sponges will decrease;the porosity and the capacity of water absorbing and retaining of sponges will increase and then decrease.Compared with other three groups of samples,when the dosage of Na2SO4 is 1.5 times than that of cellulose suspension,the porosity(94.4%)and the hydrophilia of sponges are relatively the highest.However,when the dosage of Na2SO4 is same as that of cellulose suspension,although the porosity and the hydrophilia of samples are lower than the former,the stability of pore structures will be more stable,resulting in a relatively high tensile strength of cellulose sponges(0.73 MPa),the loss of which in the process of preparation is also very small.As the dosage of pore forming agents is equal to that of cellulose suspension,and the total mass fraction of cellulose is 5%,with the increase of the the mass ratio of cotton and MCC,the tensile strength of sponges will be enhanced correspondingly,which can reach 0.85 MPa;when the proportion of absorbent cotton and MCC is 1:2,the sponges have the relatively highest capacity of water absorbing(14.3 times)and retaining(13.0 times);according to the infrared analysis,the main crystal type of cellulose in cellulose sponges is cellulose II.As the mass of the pore forming agents is identical to that of cellulose suspension,and the mass ratio of absorbent cotton and MCC is 1:4,with the increase of the total mass fraction of cellulose,the pore structures of cellulose sponges will be more complete,and the thickness of bubble walls will increase gradually;the tensile strength will increase to 1.02 MPa(6%)and then decrease;the porosity and the water adsorption ability will decrease in general.SS-PCMs were prepared by combining cellulose sponges as matrixes with PEG possessing different molecular weights through physical blending method.The preparation condition of cellulose sponges was chose as that:the mass of pore forming agents is identical to that of cellulose suspension,the total mass fraction of cellulose is 5%,and the mass ratio of absorbent cotton and MCC is 1:1.The experimental results show that,compared with other three kinds of PEG with different molecular weights,PEG-6000 can be composited with cellulose matrixes relatively well,and the thermal stability of SS-PCMs with PEG-6000 is relatively high too.In this article,the mass fraction of PEG-6000 can reach 90.77%in SS-PCMs without liquid leakage.Cellulose matrixes and PEG can be composited with each other,mainly because of pore structures and hydrogen bonds without any chemical reaction.The melting enthalpy(?Hf)of SS-PCMs increases with the increase of the mass fraction of PEG,the highest value of which can reach 146.88 J·g-1,but less than that of pure PEG-6000(179.09 J·g-1).The change rule of crystallization enthalpy(?Hc)is opposite to that of molten enthalpy,and the highest absolute value of ?Hc can reach 137.81 J·g-1.The thermal stability of SS-PCMs is also relatively good.In order to enhance the thermal conductivity of the SS-PCMs prepared,nano TiO2 was chosen as the thermal conductivity enhancement particles.Experimental results show that,with the increase of the mass fraction of nano TiO2 in SS-PCMs,the thermal conductivity of SS-PCMs will gradually increase.When the mass fraction of TiO2 is 2.16 wt%,the thermal conductivity increases by 12.93%compared with that of SS-PCMs without nano TiO2;the increase of thermal conductivity will also accelerate the response speed of temperature change of SS-PCMs,which will promote the ability of SS-PCMs to absorb and release more heat in the processes of phase change.