六种沙生灌木pH值,缓冲容量及对脲醛树脂胶（UF）固化时间的影响

为了合理开发我国西北地区的沙生灌木，研究了内蒙古西部地区沙柳，柠条，沙棘，红柳，桦棒，杨柴６种主要沙生灌木的ｐＨ值，酸碱缓冲容量与ＵＦ胶混合物固化时间。结果表明：６种灌木均呈弱酸性，ｐＨ值为６．０３￣４．５４，酸缓冲容量为０．１０５￣０．０４０ｍｍｏｌ，碱缓冲容量为０．３１４￣０．２２２ｍｍｏｌ。种间的ｐＨ值，缓冲容量和ＵＦ胶固化时间差异显著，而每种灌木部位间的上术指标均无显著差异。     

速生水杉的酸性及对脲醛树脂胶固化的影响

为科学开发速生水杉木质复合材料。研究了江苏省丹阳、高邮两地速生木杉的几个与木材胶合有关的指标（ｐＨ值、酸碱缓冲容量、酸含量及木粉与ＵＦ胶混合物的固化时间）。结果表明：两地水杉呈微酸性，ｐＨ值为５．６－６．２８，两地速生水杉或同一产地水杉的各酸性指标值略有差别，但在人造板生产中可采用相同的、常规胶合工艺。     

单宁胶用PUF树脂的制备工艺与结构和交联性能关系的研究

提出了一种单宁胶用ＰＵＦ树脂的制备方法。用＾１３ＣＮＭＲ研究了制备条件对ＰＵＦ树脂组分、结构和交联性能的影响。压板试验表明ＰＵＦ树脂配制单宁胶时，只有折合甲醛值大于１０％，压制的胶合板才能符合室外级板的强度要求。用ＤＳＣ研究了固化温度对该单宁胶固化程度的影响。     

杨树木材pH值及其对脲醛树脂胶固化时间的影响

讨论了１１年生的Ⅰ－６３杨、Ⅰ－６９杨和Ⅰ－７２杨三个无性系在株行距分别为４ｍ×４ｍ、５ｍ×５ｍ、６ｍ×６ｍ和７ｍ×７ｍ四个造林密度条件下木材ｐＨ值和脲醛树脂胶的固化时间。结果表明，心材的ｐＨ值和脲醛树脂胶固化时间均大于边材；Ⅰ－７２杨心材的ｐＨ值大于Ⅰ－６３杨和Ⅰ－６９杨。方差分析表明无性系之间以及株行距之间与脲醛树脂肢固化的间的差异均不显著。     

红锥木材性质与UF胶固化时间关系的研究

对红锥木材性质与UF胶固化时间的测定和分析结果表明：红锥木材呈弱酸性，心边材不同部位、树干不同高度木粉的pH值和缓冲容量无显著差异；UF胶的固化时间与pH值在0．01水平上相关极显著，与酸缓冲容量在0．05水平上相关显著，与碱缓冲容量相关不显著。研究结果为红锥木材的培育和合理利用提供了科学依据。     

豫东产泡桐和沙兰杨木材的pH值、缓冲容量及其对脲醛树脂胶固化时间的影响

实测了豫东产兰考泡桐、杂交泡桐和沙兰杨木材的pH值、酸碱缓冲容量,并就脲醛树脂胶固化时间等指标,从理论上分析三树种木材本身酸碱性质对胶合 性能的影响。结果表明,三树种木材均呈弱酸性,pH为5.05～5.92;三树种间及不同部位间木粉的pH值、酸碱缓冲容量及其对脲醛树脂胶固化时间的影响均无显著差异。     

东北四种榆木材性与胶合性能的研究

春榆、裂叶榆、家榆、白榆（大果榆）４种榆木解剖特征、物理性能、ｐＨ值和缓冲溶量及凝胶时间的测试分析表明，榆木的材性变异、ｐＨ值和碱缓冲溶量影响其胶合性能；在榆木胶合板生产工艺中应使用混合型固化剂。     

水杉脲醛树脂胶定向刨花板的研究

利用水杉木材制造定向刨花板（ＯＳＢ），既是水杉高效利用的途径之一，又为ＯＳＢ拓展了原材料来源，为ＯＳＢ的发展提供了条件，本文分析了水杉木材与制板工艺有关的物理，力学，化学性质，研究了水杉材ＵＦ胶ＯＳＢ的生产工艺，试验结果表明，利用水杉木材生产ＵＦ胶ＯＳＢ是完全可行的，只要工艺参数选择合理，产品性能可达或过欧共体ＵＦ胶定向刨花板标准要求。     

土壤pH值对湿地松木材酸碱性的影响

研究了土壤ｐＨ值对生长在该立地上的湿地松木材的ｐＨ值，酸碱缓冲容量的影响，结果表明，林分土壤ｐｈ值对木材ｐＨ值有极显著的影响，且呈正相关关系；土壤ｐＨ值对木材酸碱缓冲容量，总缓冲容量有显著的影响，且呈负相关关系。湿地松以生长在酸性土壤的木材制胶合板的质量较优。     

单板含水率对湿固化异氰酸酯胶性能的影响

研究了木材含水率对湿固化异氰酸酯胶黏剂(YQJ-S)性能的影响。结果表明,木材含水率越高,YQJ-S润湿性和渗透性越好,且固化反应起始温度越低。因YQJ-S固化反应活化能较低,可在室温下与高含水率木材发生固化反应。当木材含水率为70%时,YQJ-S胶接强度最大。     

几种废弃木材木粉对脲醛树脂固化行为的影响

测定不同废弃木材纤维的pH值和缓冲容量,探讨不同废弃木材木粉及其混合物,对脲醛树脂固化行为的影响。结果表明,不同废弃木材原料木粉对脲醛树脂的峰值温度均有影响。在实际生产中,企业可以根据实际情况选择相应的原料种类组织生产。     

胶合板用改性脲醛树脂的调制与应用

分别就改性脲醛(UF)树脂的调胶pH值以及面粉加量对胶液胶合性能的影响进行讨论.结果表明,随着pH值降低,胶合强度和预压强度增大,固化时间和适用期缩短,甲醛释放量降低;面粉用量增大对胶液粘度影响显著,对胶合强度、甲醛释放量有不利影响,但可改善预压性能.综合考虑生产实际,以pH值4.5和面粉加量20%为宜.     

芳香型纤维板制造工艺

为实现中密度纤维板的芳香功能,开展了将香精加入至胶黏剂中与木材纤维共混压制中密度纤维板的试验。试验结果表明,无论是檀香香精还是茉莉香精,加入脲醛树脂后,虽对胶黏剂的pH值、黏度及固化时间略有影响,但在纤维板的热压过程中,可作为固化剂使用,对中密度纤维板的物理力学性能并无明显影响,而芳香型纤维板所具有的芳香性能广泛受到好评。     

硅灰石矿物粉改性脲醛树脂胶黏剂的研究

用未改性硅灰石[Ca_3(Si_3O_9)]矿物粉和硅烷类改性硅灰石矿物粉改性脲醛树脂胶黏剂,研究了硅灰石对脲醛树脂胶黏剂性能的影响和改性脲醛树脂制备的刨花板的胶合性能。研究结果表明,硅灰石矿物粉及其添加量对UF胶的固体含量、pH值、黏度、接触角、固化时间均有一定的影响,所制备的刨花板与用原胶相比胶合性能有不同程度的降低,随着硅灰石添加量的增加,刨花板的吸水厚度膨胀率增加,内结合强度有一定程度下降,但可以达到刨花板国家标准的要求。硅灰石矿物粉作为脲醛树脂胶黏剂改性剂是可行的。     

Effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia (Paulownia fortunei) wood

In this study, the effect of nanoclay on some applied properties of oriented strand board (OSB) made from underutilized low quality paulownia wood was investigated. Organo-modified montmorillonite (MMT) at four levels (0, 1, 3 and 5?%) was added to urea formaldehyde (UF) resin. Some chemical properties of paulownia wood (holocellulose, cellulose, lignin and ash contents, pH value and hot and cold water solubility), mechanical [modulus of rupture (MOR), modulus of elasticity (MOE), internal bond strength, screw and nail withdrawal strengths], physical (water absorption and thickness swelling) properties and formaldehyde emission of the strand boards were evaluated. Mechanical properties of all panels complied with the general-purpose OSB minimum property requirements of European Norm. With increasing 5?% nanoclay to UF resin, mechanical and physical properties of the resulting panels improved and formaldehyde emission decreased. However, none of the panels satisfied the thickness swelling and water absorption requirement. The results of X-ray diffraction and transmission electron microscope analysis confirmed the good dispersion of nanoclay in the resulting OSBs. Using paulownia as a fast-growing underutilized species not only can sustain the forests but also can supply raw material to countries facing shortage of wood.     

Straw-wood composites bonded with various adhesive systems

In order to study the feasibility of utilizing wheat straw as an alternative raw material for panels, experimental one-layer particleboards were produced by mixing straw with industrial wood particles in various proportions (100:0, 75:25, 50:50, 25:75, 0:100). Three different adhesive systems were used for blending the raw materials: a UF resin (E₂ grade), a PMDI resin and various UF:PMDI combinations (10:0, 8:2, 7:3, 6:4, 5:5). The evaluation of the mechanical and hygroscopic properties of panels showed the following results: Partial replacement of wood particles from straw in panels bonded with pure UF resin resulted in deterioration of all properties except linear swelling. Partial or whole substitution of wood by straw in PMDI bonded panels, improved the bending strength and all hygroscopic properties of the panels but reduced the internal bond (dry and wet) and screw holding strength, although to a much smaller degree compared to UF bonded panels. The properties of panels bonded with various UF:PMDI combinations and comprising 50% wood and 50% straw were considerably improved by increasing the PMDI content. In terms of the properties, pure straw panels or panels made of certain wood/straw mixtures, if bonded with PMDI resin or the appropriate UF:PMDI combination, can be used for specific applications where high quality panels are required according to the specifications of the related standards. Received 11 February 1998     

The ambient aging of wood fiber and its effect on mechanical properties of MDF panels

Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to study ambient-aged wood fibers and their effects on the mechanical properties of medium-density fiberboard (MDF). It was found that MDF made with ambient-aged fibers had poorer mechanical properties than MDF made with fresh fibers; this difference resulted from the alterations of surface characteristics of wood fibers after ambient aging, which led to poor wettability of the urea–formaldehyde (UF) resin applied to the aged wood fibers. After 6 months of ambient aging, the concentration of carbonyl groups in the fibers increased by 144%, while the pH value of wood fiber decreased from 5.2 to 4.7. SEM showed that much more UF resin agglomerated on the surface of ambient-aged fibers and the breakage of MDF made with aged fiber frequently occurred at the resin-fiber interfaces, indicated the poorer wettability of UF resin to fibers due to the decrease in surface energy after aging.     

固体核磁共振法对低甲醛释放脲醛树脂化学结构的研究

在采用液体核磁对3种低甲醛释放脲醛树脂化学构造进行分析的基础上,利用13CCP/MASNMR对脲醛树脂固化产物的化学结构进行了研究.结果表明,不同固化体系下,3种低甲醛释放脲醛树脂胶黏剂的固化历程不同,固化后树脂的结构有所差别.不添加固化剂时,脲醛树脂的固化交联反应程度低,固化产物中羟甲基含量高,甲醛释放量也随之增加.加入固化剂后,促进了羟甲基的固化交联反应,脲醛树脂固化产物中羟甲基含量普遍降低.3种固化体系下,UF-3羟甲基含量最高;在氯化铵为固化剂的条件下,UF-2羟甲基含量最低,为0.0582;不添加固化剂和复合固化体系条件下,UF-1羟甲基含量最低,分别为0.0784和0.0713.不同固化体系对不同种类脲醛树脂的固化效果不同,固化后树脂的结构不同,其力学性能和甲醛释放能力也不同.     

微波等离子处理对脲醛胶性能的影响

脲醛树脂胶粘剂是木材加工领域应用最广泛的胶粘剂,在保障其胶合性能的前提下降低脲醛胶的甲醛释放量是社会关注的焦点和难点。通过试验,研究不同的微波等离子处理方法对脲醛树脂胶粘剂的固化时间、适用期、胶合强度、游离甲醛含量的影响。试验结果表明:等离子处理对脲醛树脂胶粘剂的固化时间和适用期的影响不明显;合适的等离子处理条件可以改善脲醛胶的胶合性能;与未经等离子处理脲醛胶相比,等离子处理后脲醛胶的游离甲醛含量显著降低。