胶合板胶合强度新旧标准检测的差异研究

对比分析了新旧两版胶合板国家标准中的胶合强度测试方法及结果,发现GB/T 9846—2015增加的试件预处理使胶合强度降低,但槽口深度的变化又使胶合强度增大,总体来说新标准检测Ⅲ类胶合板会使胶合强度值有所降低,提醒企业在生产质量控制中重视两版标准间测试方法的差异。     

不同预处理温度对Ⅱ类胶合板胶合强度的影响

以Ⅱ类胶合板为研究对象,在保证其他试验条件不变的情况下,通过改变试件预处理浸渍温度,探究不同浸渍温度对Ⅱ类胶合板胶合强度的影响。结果显示,胶合强度随着浸渍温度的增加而降低,当浸渍温度80℃时,胶合强度接近标准中规定的临界值;浸渍温度达到90℃时,胶合强度显著降低,试件均不合格。     

木塑复合胶合板热压复合因子研究

以杨木单板、低密度聚乙烯制备木塑复合胶合板为研究对象,采用正交试验L9（3^4）系统分析了热压温度、热压时间和塑料加入量等热压复合因子对胶合性能的影响。采用方差与极差方法进行试验分析,结果显示在试验选定的因子水平下,热压温度和热压时间对胶合强度影响不显著,塑料加入量对胶合强度影响非常显著,胶合强度随塑料加入量的增加而增加。筛选出最佳工艺复合因子：热压温度140℃、热压时间3min、塑料加入量0．34Kg／m2,采用此工艺条件制备的胶合板进行性能验证,其胶合强度大大高于胶合板国家标准中Ⅱ类胶合板的性能要求。     

阻燃剂用量和胶黏剂种类对竹材胶合强度的影响

研究了3种不同用量的阻燃剂FRA分别与水溶性酚醛胶、三聚氰胺甲醛树脂胶、三聚氰胺改性脲醛胶搭配压制竹材胶合板的胶合强度。结果表明,在本研究的因素水平范围内,FRA对竹材胶合板的胶合强度有一定不良影响,特别是在使用MUF时,胶合强度随阻燃剂用量的增加而降低。     

4A分子筛对阻燃胶合板性能的影响研究

以4A分子筛为阻燃改性剂,BL阻燃剂为阻燃剂,压制了阻燃胶合板.研究了4A分子筛用量对BL阻燃剂处理胶合板的胶合强度与阻燃性能的影响.结果表明:加入适量的4A分子筛,阻燃胶合板的胶合强度显著提高,对阻燃性能影响较小.当分子筛添加量为8%时,阻燃胶合板的胶合强度可达到1.08MPa,氧指数为42.2%.     

人工林杉木胶合工艺优化研究

采用SAS全因子试验设计,研究了胶粘剂类型、涂胶量、单位压力、加压时间和胶合面纹理五个因子对人工林杉木木材胶合性能的影响,并对其胶合工艺进行了优化。研究结果表明:胶粘剂类型对杉木木材常态胶合剪切强度和木破率的影响不显著,但是老化处理后API和PF的胶合剪切强度和木破率比PVAc和UF的要高;在以API为胶粘剂时,涂胶量、单位压力、加压时间和胶合面纹理对杉木胶合剪切强度和木破率的影响显著,优化的胶合工艺为涂胶量250g/cm2,单位压力1.5 MPa,加压时间50 min和胶合面纹理为弦切面-弦切面。     

不锈钢纤维/木单板复合电磁屏蔽功能胶合板

为了赋予木基复合材料电磁屏蔽功能,在脲醛树脂胶中加入不锈钢纤维(SF)导电单元,制备三层结构的落叶松复合胶合板,研究不同施加量和不同长度的导电单元以及涂胶量对木基复合材料电磁屏蔽性能(SE)和胶合强度(ST)的影响.结果表明,除SF25-80外,胶合强度均达到或超过国家标准.涂胶量增大对电磁屏蔽效能有不利影响.在不锈钢纤维长度相同(6～7 mm)的条件下,胶合板的电磁屏蔽效能为13.63～21.14 dB,电磁屏蔽模型显著,胶合强度模型不显著;在不锈钢纤维施加量相同(40g/m2)的条件下,胶合板的电磁屏蔽效能为13.40～21.37 dB,电磁屏蔽模型和胶合强度模型均显著.不锈钢纤维的加入一方面有利于导电网链的形成,但另一方面对胶合强度有不利影响,进而不利于胶合板的导电性,因此电磁屏蔽性能是这两个方面综合作用的结果.不锈钢纤维长度的增加可以使胶层中不锈钢纤维的搭接率增加,有利于电磁屏蔽效能的增加.     

玄武岩连续纤维增强结构用胶合板的研究

为提高结构用胶合板的力学性能,本研究对使用不同胶黏剂、不同板坯结构以及不同工艺条件的玄武岩纤维增强树脂(BFRP)/结构用胶合板生产工艺进行了研究,并对复合材料的静曲强度、BFRP与结构用胶合板之间的胶合强度进行了检测与分析.结果表明:与未增强的结构用胶合板相比,BFRP增强结构用胶合板的静曲强度提高了1～2倍;羟甲基化间苯二酚(Hydroxymethylated Resorcinol,HMR)的使用大大改善了BFRP与木材界面的胶合性能.使用BFRP提高结构用胶合板的力学性能是切实可行的.     

铜纤维与木单板的复合

为了赋予木基复合材料电磁屏蔽功能,在脲醛树脂胶中加入黄铜纤维导电单元,制备三层结构的落叶松复合胶合板,研究不同施加量和不同长度的导电单元以及涂胶量对木基复合材料电磁屏蔽性能 (SE) 和胶合强度 (ST) 的影响.结果表明,胶合强度均达到或超过国家标准.涂胶量增大对电磁屏蔽效能有不利影响.在黄铜纤维长度相同 (6～7 mm) 的条件下,电磁屏蔽效能为6.34～28.76dB,吨磁屏蔽和胶合强度模型均不显著;在黄铜纤维施加量相同 (120g/m2) 的条件下,电磁屏蔽效能为15.61～35.01dB,电磁屏蔽模型均显著,胶合强度模型不显著.黄铜纤维的加入一方面有利于导电网链的形成,但另一方面对胶合强度有不利影响,进而不利于胶合板的导电性,因此电磁屏蔽性能是这两个方面综合作用的结果.黄铜纤维长度的增加可以使胶层中黄铜纤维的搭接率增加,有利于电磁屏蔽效能的增加.     

插层处理纳米蒙脱土改性脲醛树脂对胶合板性能的影响

将纳米蒙脱土、十六烷三甲基溴化铵插层处理后的纳米蒙脱土、面粉分别对脲醛树脂进行改性,用改性后的脲醛树脂制备胶合板,并检测其胶合强度和游离甲醛释放量。结果表明:相比面粉,用纳米蒙脱土和插层处理纳米蒙脱土改性的脲醛树脂制得的胶合板均表现出了较好的胶合性能和较低的游离甲醛释放量,且插层处理纳米蒙脱土改性的脲醛树脂性能更优异。     

Study on the water resistance of plywood bonded with UF-glutaraldehyde adhesive

A UF-glutaraldehyde adhesive system was used for the preparation of three-ply plywood. It was shown that 10 wt % content of the modifier markedly improves the durability of the plywood in water. The obtained wet shear strengths are comparable to those of dry plywood.     

Study on the water resistance of plywood bonded with UF-glutaraldehyde adhesive

A UF-glutaraldehyde adhesive system was used for the preparation of three-ply plywood. It was shown that 10 wt % content of the modifier markedly improves the durability of the plywood in water. The obtained wet shear strengths are comparable to those of dry plywood.     

超声波辅助变压滚揉对鸡肉腌制品质的影响

本文研究了超声波辅助变压滚揉对鸡肉腌制品质的影响。取宰后4 h剔除筋腱修整之后的新鲜鸡胸肉(每份50±1 g,5×4×4cm)随机分成两组,分别浸渍于装有腌制液的自封袋中,采用常压滚揉和超声波辅助变压滚揉分别处理,然后对处理后的样品进行剪切力、DSC等指标的测定。结果表明,超声波辅助变压滚揉处理组较常压滚揉处理组,各指标均在较短时间内获得较佳效果;腌制吸收率随处理时间的延长而显著增加(p0.05);超声波辅助变压滚揉能够有效改善鸡肉嫩度,处理100 min时剪切力降至5.3 N;蒸煮损失在100 min降为24.98%;MFI值随处理时间的延长显著增加(p0.05);SDS-PAGE电泳图谱看出,超声波辅助变压滚揉可以缩短大分子量蛋白降解以及小分子量蛋白产生的时间;DSC结果显示,滚揉后蛋白对热更加敏感。因此,超声波辅助变压滚揉能够改善鸡肉的腌制品质。     

高级证券纸施胶量测定方法的比较

对差量法、水煮法测定高级证券纸施胶量的离散程度进行比较,分析了实验室模拟施胶实验、施胶纸水煮前后灰分的变化,优化了测定施胶量的水煮法,并引入统计分析方法分析数据。结果表明,水煮法测定施胶量的离散系数远小于差量法,水煮法测定高级证券纸施胶量的准确性高于差量法;水煮法测定实验室模拟施胶纸的施胶量比真实施胶量低0.29g/m2左右,未溶出表面施胶剂量占总施胶量6.97%左右;施胶纸水煮前后灰分含量相差0.03个百分点,对水煮法测定施胶量可以忽略不计;水煮法工艺条件为:成纸较适宜干燥时间为30min,煮后纸张较适宜干燥时间为40min,成纸水煮较适宜时间为90min。     

落叶松树皮热解油-酚醛树脂胶黏剂制造胶合板的初步研究

以落叶松树皮热解油按比例0、20％、40％、60％代替苯酚制备的4种酚醛树脂胶黏剂和人工林杨木单板为原料，采用正交实验设计方法，选择不同的热压压力、热压时间和涂胶量进行了3层胶合板压制试验。根据试验结果分别针对4种胶分析影响胶合板强度的主要因素，给出了不同胶种的最优胶合工艺参数。     

Investigation on bonding quality of beech wood (Fagus orientalis L.) veneer during high temperature drying and aging

In the present study, the effects of high drying temperature and UV light induced aging on bonding quality of plywood manufactured from untreated and treated veneer layers were investigated. Rotary cut veneers with dimensions of 500 mm×500 mm×2 mm produced from beech (Fagus orientalis Lipsky) log were selected for topochemical, chemical and mechanical analyses. The veneer sheets were oven-dried at 100°C and 180°C after the peeling process. Afterwards, the surfaces were exposed to artificial UV irradiation in an UV chamber for 24 h, 48 h and 72 h representing natural sun irradiation of 2, 4 and 6 months, respectively. Topochemical distribution of lignin and phenolic extractives of the treated and untreated veneers was investigated on a cellular level using UV microspectrophotometry (UMSP). For the chemical characterization of accessory compounds high performance liquid chromatography (HPLC) was used. Furthermore, the shear and bending strengths of plywood manufactured from the treated samples are determined in order to study the bonding quality. The UV microscopic detection shows that after high drying temperature and aging treatment, lignin condensation occurs. With increasing drying temperature and aging duration, more phenolic extractives are situated in parenchyma cells and vessel lumens which can be proved by increased absorbance at 278 nm. The HPLC analysis of the treated tissue showed distinct signals of polymerized compounds such as catechin and 2,6-dimethoxybenzoquinone which are chromophoric compounds in discolored beech wood. The mechanical properties of plywood showed that with increasing drying temperature up to 180°C does not negatively affect shear and bending strengths of samples. After exposure of the veneers to UV irradiation (especially 6 months), decreasing shear and bending strengths of plywood samples can be observed.     

Effect of heat treatment intensity on wood chemical composition and decay durability of Pinus patula

Heat treatment is an effective method to improve biological resistance of low natural durability wood species. The aim of this study was to enhance the decay resistance of Pinus patula, an African low natural durability softwood species, via wood thermal modification technique. Heat treatment was performed on wood specimens under inert conditions at different heat treatment intensities to reach mass losses of 5, 10 and 15%. Heat treated specimens were exposed to fungal decay using the brown rot fungus Poria placenta. The wood chemical and elemental composition was determined as well as extractives toxicity before and after wood thermal modification to understand the reasons of durability improvement. The treated specimens exhibited a significant increase in their durability against wood decay in line with the severity of the treatment. Wood holocellulose was found to be distinctly more sensitive to the heating process than the lignin constituent. In addition, obvious correlations were observed between weight losses recorded after fungal exposure and both holocellulose decrease and lignin ratio increase. The same correlations were observed with the elemental composition changes allowing using the observed differences for predicting of wood durability conferred by heat treatment. Furthermore, no significant differences were observed between the toxicity of Pinus patula wood extractives before and after its thermal modification.     

The effects of waiting time of alder (Alnus glutinosa subsp. barbata) veneers before drying on shear and bending strength of plywood

(Alnus glutinosa subsp. barbata ) veneers before drying, on some properties of plywood, were investigated. Veneers produced at laboratory conditions were divided into four groups considering their waiting time before the drying process. pH and 1% NaOH solubility of these four groups of veneers were determined. No significant differences were found in solubility and pH values obtained from test groups. In addition bending strength, shear strength and formaldehyde emission values of plywood, produced from these veneers, were investigated. While bending strength and formaldehyde emission values of the plywood showed no differences, the shear strength of the plywood produced from veneers immediately dried after production was significantly higher than the one of other groups.

---

     

Eigenschaften formaldehydarm verleimter Sperrhölzer

Tests were carried out on both industrial plywood with low content of formaldehyde and laboratory plywood. There were eight series plywood from different industrial manufactures including blockboard and a blockboard with particleboard decks. Twelve lab-series (5×1.5 BU) were produced of different formulae by the technical department of WKI. Bending and bonding properties as well as formaldehyde emissions of plywood were determined. Creep behaviour of plywood will be described in part 2. Plywood showed good bending characteristics dependent on its structure. Bonding strength after tensile and shear tests as well as after prick test complied with IF bonding quality even after alternating climatic storages. The different series, however, differ widely with respect to IW bonding quality. The different potential of formaldehyde emissions of the series was determined according to various methods, correlations between the methods could be proved. The test, however, revealed the difficulties caused by the material to measure formaldehyde emission of plywood.     

Untersuchungen zur Verleimung von Furniersperrholz mit modifizierten Diisocyanat-Klebstoffen

It was the aim of the investigations to find some modified and extended PMDI binders, suitable for bonding vencer plywood of the type AW. The bonding strength had to fullfill the requirements of DIN 68 705 part 3 resp. DIN 53 255. Pretrieatments were a cold water storage and boiling test. Three-ply boards were pressed from spruce, beech and gaboon veneers. Binders were PMDI-glues with and without emulgators and the extender tannin, Organosolv-spruce-lignin, lignosulfonic acid, casein and corn starch. The results showed the following. Veneer plywood of the type AW can be produced applying PMDI together with suitable reactive agents. The veneer wood species, the glue mixtures, the pressing conditions and the fillers have to be adjusted to the PMDI type and to the extender. Plywood made with modified, emulsified diisocyanate showed a better bonding strength and wood failure than plywood bonded with non-emulsified diisocyanate.