自水解后杨木边材木片化学组分和结构特性的变化及其对木片碱液浸渍的影响

分析了影响杨木边材木片对碱液反应性吸收的化学组分和结构特性在自水解预处理后的变化,及在碱液浸渍过程中浸渍液碱浓和浸渍温度对自水解木片浸渍效果的影响。结果表明,杨木边材木片的综纤维素、乙酰基和木素含量都随着自水解强度的增大而降低,而弱酸性基团含量则先增加后减少。在自水解预处理后,杨木导管内部的基质/侵填体得以清除,部分纹孔膜被溶解破坏。对原料木片及自水解预处理后杨木边材木片进行碱液浸渍处理后发现,木片的NaOH溶液吸收量和NaOH消耗量随自水解强度的增大而增加。自水解预处理改善了杨木边材木片的碱液浸渍效果。各类木片的NaOH溶液吸收量和NaOH消耗量均随浸渍液碱浓的增大和浸渍温度的升高而增加,且都呈现良好的线性相关性。     

三倍体毛白杨CTMP制浆预处理渗透速率研究

研究了三倍体毛白杨边材和心材在不同温度下纵向和横向渗透的速率。结果表明：纵向渗透速率远大于横向渗透速率;边材纵向渗透速率略大于心材纵向渗透速率;边材横向渗透速率与心材横向渗透速率几乎相同;温度越高,渗透速率越大。     

镁碱替代钠碱对杨木P-RC APMP制浆废液的影响

杨木P.RC APMP制浆过程中,在二段化学预浸渍段和高浓停留段,采用不同量的MgO替代NaOH.结果表明,当二段化学预浸渍段和高浓停留段MgO替代NaOH的比例分别为25%和50%时,高浓停留段废液的CODcr、阳离子需求量和电导率比没有MgO替代时分别降低了26.5%、30.3%和54.5%.     

汽蒸处理对杨木尺寸稳定性及横向渗透性的影响

分别采用温度为100℃、120℃、140℃的蒸汽对杨木进行汽蒸处理,测定了汽蒸处理材与未处理材尺寸稳定性变化规律,并采用自行设计制作的渗透性测量装置测定了汽蒸处理材与未处理材的横向渗透性变化规律.结果表明:经过汽蒸处理的杨木尺寸稳定性和横向渗透性均得到了改善.木材干缩率随着蒸汽温度的升高而降低,湿胀率随温度的升高先降后升;不同汽蒸温度对试件的横向渗透性影响程度不同,采用140℃汽蒸处理对杨木横向渗透性改善效果最好,木材弦向和径向渗透性分别提高了52.14％和53.41％.     

KOH与NaOH浸渍麦草化学机械法制浆性能比较

探究了KOH与NaOH在用碱量3%～7%(以KOH计)与浸渍时间10～80 min的不同条件对麦草化学机械浆及所抄纸张物理化学性能的影响。结果表明,在常压、浸渍温度95℃的温和条件下,KOH浸渍的麦草化机浆与NaOH浸渍的麦草化机浆相比,具有更高的紧度和强度。在浸渍过程中,由于KOH具有较强的脱木素能力,纸浆得率下降较多;KOH碱性较强,导致残液的pH值较高。KOH比NaOH破坏麦草纤维素结晶区的能力更强,因此其浸渍后的麦草浆中纤维形态较NaOH浸渍后的纤维形态更优。     

杨木CTMP碱性H2O2漂白中糖醛酸溶出的研究

研究了杨木CTMP碱性H2O2漂白过程中漂白工艺对糖醛酸溶出的影响。结果表明,糖醛酸的溶出主要受体系碱度的影响。高碱度下,H2O2的加入会在一定程度上阻碍糖醛酸的溶出;高温(如高于80℃)会加剧糖醛酸的溶出;一定温度下,糖醛酸的溶出主要在反应初期阶段较快速。正交实验结果表明,影响糖醛酸溶出的漂白工艺条件依次为NaOH用量、温度、H2O2用量、浆浓、反应时间。     

体外加速降解对聚丙烯/聚乳酸可降解复合疝气补片的影响

为使复合补片性能更加稳定,采用磷酸盐缓冲液(PBS)、Na2CO3溶液和不同质量分数NaOH溶液对聚丙烯(PP) /聚乳酸(PLA)可降解复合疝气补片进行加速降解试验,测试并分析了降解过程对该补片外观、质量等结构参数以及拉伸断裂强力和抗弯刚度等力学性能的影响。结果表明：弱碱Na2CO3溶液能够加速该补片的降解,但效果不太显著。5%浓度的Na2CO3比生理缓冲液PBS更易导致降解过程中补片质量的损失,但对于补片力学性能的损失与PBS的效果相差不大。而强碱NaOH溶液加速降解效果非常显著。加速降解过程中,补片的质量和强力损失均表现为：开始降解速度较快,一段时间后,降解速度有所减慢,最后PLA完全降解后,质量和强力均趋于稳定值;该三梳毛刺结构的复合补片,降解前工艺正反面的抗弯刚度差异较大,且反面抗弯大于正面抗弯刚度,横向抗弯刚度大于纵向抗弯刚度,PLA完全降解后,补片正反面抗弯刚度基本无差异,但纵向抗弯刚度略大于横向抗弯刚度。     

CTMP制浆中三倍体毛白杨木片浸渍机理的研究

通过测定NaOH、Na2SO3以及其不同的浓度组合时木片预浸过程中电导率的变化,对CTMP制浆预处理过程中药液对三倍体毛白杨木片的渗透机理进行了研究。结果表明：CTMP预处理过程中药液在木片中的渗透过程可分三个阶段：初始阶段;渗透速度上升阶段和单纯物理扩散阶段。高浓度药液扩散速度较快,药液扩散量增加。NaOH及其与Na2SO3的混合液在木片的轴向与弦向上渗透速率具有明显差异。在NaOH溶液中加入Na2SO3,可增加扩散通量。提高温度有利于加速乙酰基的脱除以及药液的扩散,从而减少预处理时间。     

绿液预处理杨木硫酸盐法蒸煮脱木素反应历程研究

采用碱回收绿液对杨木木片进行预处理,研究了预处理后硫酸盐法蒸煮过程中脱木素反应历程及NaOH的消耗过程。研究表明,采用绿液预处理后,杨木木片得率为73.1%,木素脱除率为32.54%。预处理后的蒸煮过程中,在初始脱木素段,木素脱除率为14.52%;在大量脱木素段,木素脱除率为42.62%;残余脱木素段,木素脱除率仅为3.41%。这3个阶段的木素脱除率比传统硫酸盐法分别降低了3.55、19.38和9.11个百分点。NaOH几乎全部消耗在蒸煮初期和大量脱木素段,这2个阶段NaOH分别消耗了57.71%和42.29%;Na2S质量浓度在蒸煮初期逐渐减小,蒸煮的中后期又逐渐增大。绿液预处理硫酸盐法蒸煮不仅能提高脱木素选择性,还能提高蒸煮后浆料得率（达到50.8%）,比传统硫酸盐法浆料得率（47.9%）提高2.9个百分点。     

Mg（OH）2部分代替NaOH用于杨木APMP制浆

采用Mg（OH）2部分代替NaOH作为碱源,进行了杨木APMP制浆的研究。探讨了不同Mg（OH）2取代量对最终出料性能、纤维特性以及废水COD的影响。实验结果表明：随着Mg（OH）2取代量的增加,纸张的松厚度和光散射系数提高,强度和白度略有下降。纸浆纤维的平均长度逐渐变短,细小纤维含量增加,同时纤维的扭结程度和卷曲程度均呈现下降趋势;通过对制浆废水COD的研究,发现利用氢氧化镁的杨木APMP制浆可以有效地降低废水中的COD含量,更有利于实现清洁生产,同时可以节约生产成本,提高经济效益。     

Primer cure and adhesion after light organic solvent preservative treatment of Radiata pine

This study examined the effect of preservative treatment and wood drying history on paint primer cure and adhesion for New Zealand radiata pine (Pinus radiata D. Don). Double Vacuum LOSP treatments resulted in a significantly lower LOSP uptake than did Lowry treatments, for both sapwood and heartwood. Wood drying history had no effect on uptake by sapwood, but did affect uptake by heartwood; high-temperature-kiln-dried heartwood retained more solvent than air-dried or conventionally dried heartwood. For sapwood, LOSP treatment method and wood drying history did not significantly affect either primer cure or primer adhesion. For heartwood, primer adhesion in the early stage of cure was better with Double Vacuum treatments. Double Vacuum treatments also resulted in a higher cure of primer, two days after priming, than did Lowry treatment when either conventionally or high-temperature-kiln-dried heartwood was used, but no significant difference was found with air-dried heartwood. It was concluded that, for radiata pine heartwood, Double Vacuum treatment, combined with either air-drying or conventional drying, will reduce LOSP uptake and give better primer performance, so long as effective ventilated solvent removal is achieved before priming.     

Density and moisture content forecasting based on X-ray computed tomography

X-ray computed tomography (CT) technology was applied for log nondestructive testing. The heartwood and sapwood of Larix gmelinii (Dahurian Larch) were scanned by CT system. The appropriate mathematical formulas between wood density and CT number were established for heartwood and sapwood respectively, because of the close relationship between wood density and CT number. The formulas between moisture content and CT number for heartwood and sapwood were built through experiment. The results indicate that though the differences of density and moisture content between heartwood and sapwood of L. gmelinii were not obvious, heartwood and sapwood had different formulas of forecasting wood density and moisture content by CT. The fitted relationships were very strong (coefficient of determination R² > 0.94).     

Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)

From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sapwood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreasedin sapwood from the bottom to the top of the stems while the reversal occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the stems, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the stems. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom, 21.42% at the middle and 19.64% at the top.     

Extractives, acidity, buffering capacity, ash and inorganic elements of black locust wood and bark of different clones and origin

Chemical properties of black locust wood and bark from Greece, Bulgaria and Hungary (clones NY, U and J) were investigated. Disks at breast height were taken from 25 black locust trees (five trees per origin and clone) and were divided into separate biomass components (juvenile heartwood, mature heartwood, sapwood and bark). Hot water soluble (HWSE) and dichloromethane soluble extractives (DSE), acidity (pH), buffering capacity, ash content and inorganic elements were determined according to standard laboratory techniques. Bark had the highest extractive content for both HWSE (9.25–13.49%) and DSE (3.09–4.03%). Differences of extractive contents in wood were found to exist between trees of different origin and between the three clones and ranged in heartwood between 5.04–10.10% for HWSE and 0.53–1.83% for DSE and in sapwood between 3.33–6.76% for HWSE and 0.48–1.47% for DSE. The higher values of pH occurred in sapwood (4.92–5.35), while the differences between bark (4.44–5.12) and heartwood (4.35–4.92) were small. Acid (ABC) and base (BBC) buffering capacities from the initial to pH 10 for ABC and to pH 3 for BBC were greater in bark (ABC 0.0172–0.0219 ml/ml and BBC 0.0079–0.0141 ml/ml) than in the other wood components (for heartwood ABC 0.0069–0.0159 ml/ml and BBC 0.0022–0.0096 ml/ml and for sapwood ABC 0.00330.0066 ml/ml and BBC 0.00330.0049 ml/ml). The total ash content was greater in bark (7.24–8.56%) than in other biomass components (for heartwood 0.34–0.89% and for sapwood 0.72–1.24%). The content of the main inorganic elements (Ca, K, Mg, Na, P) were also found to be much higher in bark while sapwood values were greater than heartwood.     

Comparison between heat treated sapwood and heartwood from Pinus pinaster

Sapwood and heartwood samples of Pinus pinaster were treated in an oven at 190 and 200 °C for 2–6 h. Dimensional stability, measured as Anti Shrinking Efficiency (ASE) between 0 and 65 % relative humidity, durability against fungi, mechanical resistance (MOE and MOR), hardness and chemical composition were determined for treated and untreated sapwood and heartwood. Radial ASE reached 52 % for sapwood and 50 % for heartwood, while tangential ASE reached 50 and 40 %, respectively. MOE increased slightly at the beginning of the treatment, decreasing afterwards. No significant differences were found between sapwood and heartwood. MOR decreased by 50 and 30 % for sapwood and heartwood, respectively. A significant increase in durability against Rhodonia placenta was found for both heartwood and sapwood at the higher temperature (200 °C), but at the lower temperature (190 °C) only heartwood showed good results.     

Zum Verhalten des Splint- und Kernholzes der Lärche (Larix decidua) bei der Herstellung von feuchtebeständigen Spanplatten unter Einsatz verschiedener Bindemittel

Chips from sap- and heartwood of 20, 40 and 102-year-old larch (Larix decidua) were prepared and chemically characterized. From the chips one-layer boards of 20 mm thickness were prepared using melamine-urea-phenol-formaldehyde resin (MUPF-resin), phenolformaldehyde resin (PF-resin), polymeric diisocyanate (PMDI), and tannin-formaldehyde resin (TF-resin). The physical and chemical properties of the boards were determined. Moreover, the influence of hot water extractives on the pH-value, viscosity and gelation time of the resins was assessed. Sap- and heartwood chips are different in their chemical properties as well as in bonding behaviour. The age of the tree has also an influence on the bonding characteristics of the chips. Thickness swelling, water absorption and equilibrium moisture content of heartwood boards were always lower than those of sapwood boards. Moreover, bending and internal bond strength of heartwood boards made from 20- and 40-year-old trees are much higher than those produced from sapwood. The strength properties of the boards deteriorate, however, with increasing age of the tree. This applies for both heartwood and sapwood boards. The water extractives of heartwood boards are of lower pH-value and higher buffering capacity than the corresponding boards from sapwood. Moreover, the emanation of acetic acid from heartwood boards is much higher than that of formic acid. In addition, boards from heartwood are in general of lower formaldehyde release compared with boards from sapwood. The addition of heartwood extractives to MUPF-resin increases the viscosity and gelation time of the resin and decreases its pH-value, whereas in case of PF-resin no such increase in the gelation time was registered. The extracts of heartwood increase the viscosity and gelation time of TF-resin.     

Thermal stability of <Emphasis Type="Italic">Abies alba</Emphasis> wood according to its radial position and forest management

Most of the defects affecting heat-treated wood quality are often attributed to heterogeneous heat transfers in industrial kilns. Even if interspecific variability of wood has been reported to affect thermal degradation of the material, little has been reported on the effects of intraspecific variability. The aim of this work was to study the effect of intraspecific variability of silver fir (Abies alba Mill.) wood on its thermal degradation. For this purpose, wood samples were sampled along the radius of cross-sections to estimate the effect of radial position on wood thermal degradation. Sampling was carried out on discs of four trees, two resulting from dynamic growth stand and two from standard growth stand. The study was performed at different scales: at wood compartments scale involving juvenile and mature heartwood, transition zone between heartwood and sapwood and sapwood as well as at intra-ring scale. Wood samples were ground to sawdust and subjected to thermogravimetric analysis and chemical analysis. Juvenile heartwood was shown to be more sensitive to thermal degradation than other compartments. The thermal behavior of sapwood was not particularly different from that of heartwood, and the presence of extractives did not influence significantly thermal degradation. Earlywood was more sensitive to thermal degradation than latewood explaining the higher susceptibility of fast growing heartwood containing larger rings with higher contents of earlywood.     

Influence of phenolic compounds in heartwood of Silver fir (Abies alba Mill.) on the equilibrium moisture content

Experiments were undertaken to differentiate between sapwood and uncolored (light) heartwood of Silver fir (Abies alba Mill.). Paired samples of sapwood and heartwood were removed from five randomly selected healthy trees without wetwood, aged over 170 years, and (a) the percent of extractives, (b) the amount of total soluble phenols and (c) the equilibrium moisture content (EMC) at three relative humidities (RH) were determined. The percentage of extractives and the amount of total soluble phenols in the heartwood were significantly higher and EMC lower than in the sapwood. The effect of extractives on the EMC was most marked in the upper range of the RH.     

The water absorption of sapwood and heartwood of Scots pine and Norway spruce heat-treated at 170 °C, 190 °C, 210 °C and 230 °C

Heat-treatment changes the chemical and physical properties of wood. Wood polymers are degraded, dimensional stability is enhanced, equilibrium moisture content is lowered, colour darkens and biological durability is increased. The properties of heat-treated wood have been researched considerably, but the differences between sapwood and heartwood have not been reported separately. In this research, water absorption differences between sapwood and heartwood of Scots pine and Norway spruce heat-treated at temperatures 170 °C, 190 °C, 210 °C and 230 °C were investigated. The results were compared to industrially kiln-dried reference samples. Water absorption was determined with a floating test based on the EN 927-5 standard. The heartwood of both wood species absorbed less water than sapwood. Heat-treatment evidently decreased the water absorption of spruce and pine heartwood. The higher the heat-treating temperature, the lower the amount of absorbed moisture. However, a very interesting exception was pine sapwood, whose water absorption actually increased with heat-treatment after the three lowest heat-treatment temperatures compared to the reference material. Water absorption did not decrease until the heat-treatment temperature was 230 °C.