Study On Pulp&Paper Thermal Properties And Their Evaluation Methods

As a material for writing, printing, and packaging, paper has the characteristics ofabundant sources, biodegradability, recyclability, excellent mechanical properties andpost-processing performance, low cost, and flexibility. With the rapid economic developmentand social progress of human civilization, more potential areas will be explored in future.The properties of paper alter as the change of environmental conditions during theapplication of paper, one of significant factors is temperature which will severely affectpaper’s performance that hinders the application of paper. In this thesis, the thermalperformance of pulp&paper and its evaluation method are systematically studied aiming toclarify the factors influencing the thermal performance of paper and explore the intrinsic lawexisting among pyrolysis of paper, thermal aging, yellowing and so on under thermalcondition. More specifically, the research work establishes scientific method to evaluate thethermal properties of paper and provides theoretical support for efficiently utilizing paperunder high temperature atmosphere and developing new paper with excellent thermalstability.Thermogravimetric analysis shows that there are four phases occurring in the course ofthe thermal degradation of paper: loss of adsorbed water, dehydration, the main thermaldegradation and residual pyrolysis. Three primary temperatures (Tw, T0.5, and TWax) are usedto evaluate the thermal stability of pulp.The mechanism for the thermal degradation of pulp is depicted by the model equation. Kinetic equation isln()lnE, the activation energy be used to evaluate the thermal stability of pulp, the higher pulp activation energy representsbetter thermal stability of paper.When it comes to the thermal stability of various pulp, bleached softwood pulp issuperior to bleached hardwood pulp; for the non-wood pulp, cotton and hemp possess highestthermal stability; besides, deinking pulp (DIP) is inferior to virgin bleached chemical pulp, unbleached pulp is worse than bleached pulp; and BCTMP has poor thermal stability.For the given light-induced conditions, the brightness of BCTMP decreases as theincrease of light-induced time, but the PC value shows a downward trend. BCTMP made fromfir demonstrates a worst brightness stability and a serious yellowing phenomenon. R and PCvalues of BCTMP exhibit a linear relationship in a certain range with lgt of BCTMP,respectively, and the model demonstrating the R and PC value of BCTMP vary as theextension of light-induced time was deduced by regression analysis.Light-induced yellowing mechanism of BCTMP is studied by using Infraredspectroscope (IR) and Raman spectroscope to analyze the structure of functional groupswithin BCTMP before and after it exposes to ultraviolet light, and results illustrate that theappearance of double bond and triple bond between two carbons in BCTMP during thelight-induced procedure primarily causes the color reversion of BCTMP.There are three phases occurring in the pyrolysis of paper: dehydration, mass loss ofcellulose, and mass loss of char residue. The addition of fillers or other additives in the paperresults in the pyrolytic difference in the third phase compared with paper made of purecellulose. Filler loading is beneficial to thermal stability of paper, however, mechanical pulpand recyclable pulp have an adverse effect on thermal stability of paper. According toDynamic mechanical analysis (DMA), the loss modulus and damping factor of paper improveas the increase of temperature, but no turning point is observed in the pyrolytic curve. Inaddition, the storage modulus varies as the basic weight of paper and pulp proportion.Tensile strength, brightness, degree of polymerization, crystallinity and activation energyof paper during the aging process are investigated in detail. As the increase of aging time,tensile strength and brightness of paper present a downward trend. SEM images of the paperbefore and after aging indicates the phenomenon of cracking was even more serious and more and more voids appeared on the surface of paper fibers. This led to the binding force betweenfibers decreased; the crystallinity and crystal type of cellulose of paper before and after aginghad not changed under the aging temp.150°C based on XRD results.With the aging time increases, the degree of polymerization of the paper demonstrates adecreasing trend, however, the activation energy of the paper first increases and thendecreases.There is a quantitative relationship between the relative value of paper polymerizationdegree (DP/DP0) and Δθ0.5which can be used to evaluate the aging degree of paper. Therelative value of the polymerization degree can be calculated from the obtained equation, andthe evaluation model fits well with the experimental data, which indicates the good predictionof our model.A novel method for evaluating insulating properties of paper is proposed by taking papercup as the research object. We define temperature factor ω as the integral area of temperaturecurve on hot and cold side that deviates from standard curve in a certain temperature range,The relationship between temperature factor ω and temperature t is described by an equationThe temperature factors ω in a certain temperature range can be used toquantitatively assess the thermal insulation performance of paper material.