【作者】 任一萍；

【导师】 王正；

【作者基本信息】 中国林业科学研究院 ， 木基复合材料科学与工程， 2008， 博士

【摘要】 发展竹质人造板是充分利用国内丰富的竹类资源、缓解木材缺口、促进农村经济发展的有效途径,结构用竹质工程材料对产品的胶合强度要求较高,针对当前竹质结构材普遍存在的胶合质量不高、浸渍剥离率高、产品使用周期短的问题,本研究结合竹材的特性,展开对结构用竹质工程材料粘合体系及其性能评价的研究。研究中以竹篾和竹片为研究对象,通过考察竹篾层积材的浸渍剥离率和竹片的剪切强度来研究竹材的胶合强度性能。利用接触角自动测试仪,考察了竹篾和竹片用四种偶联剂处理前后其表面自由能的变化情况,考察并分析了偶联剂CA5的浓度、热压时间和热压温度这三个变量因子对竹篾层积材的物理力学性能,尤其是胶合强度的影响;测试了用不同浓度的四种偶联剂分别处理竹片表面后,酚醛树脂胶合竹片的剪切强度值。利用傅立叶红外光谱对三种硅烷偶联剂对提高竹材胶合强度的作用机理做了初步研究。利用间苯二酚对酚醛树脂进行改性,旨在提高热固性苯酚-间苯二酚-甲醛(PRF)树脂对竹材的胶合性能,考察了热固性PRF胶粘剂合成条件改变对树脂性能及竹篾层积材板材性能影响,以及不同的PRF树脂对胶合竹片剪切强度的影响,对竹篾厚度及竹帘方向对竹篾层积材的物理力学性能的影响也作了研究;为研制出低成本的冷固型苯酚-间苯二酚-甲醛树脂胶粘剂,考察了各因子对树脂性能的影响,最终优化出性能优良、成本较低的冷固型PRF树脂。通过研究得到了以下结论:竹篾与竹片表面经偶联剂CA5、KH560和KH602处理后,表面自由能有较大增加,表面润湿性改善,经偶联剂KH550处理后表面自由能则明显下降,表面润湿性变差,但是处理竹片后胶合试件的剪切强度均提高,其中KH550在浓度为0.5%时即具有明显的效果,其浓度继续增加出现先增加后减少的现象。KH560和KH602处理竹片表面后,剪切强度均是随着偶联剂浓度的增加而增加,尤其是KH560在浓度为2%时,剪切强度增加率高达400%。对硅烷偶联剂对竹材胶合性能影响机理的初步研究表明:试验中所用三种硅烷偶联剂不仅能与酚醛树脂中的羟基发生化学反应,也能与竹粉中纤维素、半纤维素和木质素大分子中的羟基发生化学反应。偶联剂CA5处理竹篾压制竹篾层积材所得最佳物理力学性能的工艺条件为:板材密度0.8g/cm3,偶联剂CA5含量为2%,热压温度160℃,热压时间14min。这一工艺条件下竹篾层积材的性能指标分别为:静曲强度181.2MPa,弹性模量11000.41 MPa,浸渍剥离率0.66%,24h吸水厚度膨胀率4.36%,优于相关标准规定值。间苯二酚含量对于热固型改性酚醛树脂提高其胶合竹材的强度具有显著的影响,随着树脂中间苯二酚含量的增大,竹篾层积材的浸渍剥离率和24h吸水厚度膨胀率先是显著减小,然后略有增加;竹片剪切强度值比不改性酚醛树脂强度增加50%以上,但是间苯二酚含量在1%到3%范围内的变化对树脂胶合竹片剪切强度影响不明显。优化的热固性PRF变量因子分别为:间苯二酚含量为1.5%,醛酚摩尔比为2.0,竹篾浸胶时胶粘剂浓度为30%。所得竹篾层积材的各项物理力学性能分别为:静曲强度185.2MPa,弹性模量10800.35 MPa,浸渍剥离率0.58%,24h吸水厚度膨胀率4.20%,优于相关标准规定值。合成冷固型间苯二酚改性酚醛树脂时,间苯二酚含量所占比例越高则测试常态强度时的木破率越高,也即胶粘剂的强度越好,但是对28小时循环煮沸试验结果影响不显著;间苯二酚含量为9%是控制PRF树脂质量的一个临界含量,此时料比的变化对树脂的强度性能和凝树脂时间影响较大;苯酚、甲醛摩尔比对树脂贮存稳定性有显著的影响,苯酚、甲醛摩尔比为1.5:1时,树脂的稳定性最好;随着调胶时固化剂多聚甲醛含量的增加,PRF树脂胶合试件的剪切强度值和木破率迅速下降,树脂的凝胶时间缩短,多聚甲醛加入的百分比为6%时,树脂的强度性能最好;优化的两种冷固型PRF树脂其间苯二酚含量分别为10.5%和9%,其剪切强度指标达到JAS SE-9标准规定值。竹篾厚度对竹篾层积材的物理力学性能有较大的影响。随着竹篾厚度的减小,竹篾层积材的24小时吸水厚度膨胀率明显减小,静曲强度值、弹性模量值和密度增加,浸渍剥离率也显著地降低,生产中篾片厚度为0.8-1.4mm较合适。竹帘方向对竹篾层积材的物理力学性能也有较大影响。竹帘方向层与层之间互为垂直时,其压制的板材的各项物理力学性能均大幅下降,其他条件相同时,竹帘垂直胶合时板材的24小时吸水厚度膨胀率和浸渍剥离率的值远远大于竹帘均平行排列时板材的对应值。更多还原

【Abstract】 It is necessary to develop bamboo-based panels. For it can take full advantage of domestic plenty bamboo resource, decrease the deforestion and protect the natural forest effectively, accelerate the development of rural economics as well as help farmer to increase income. Bamboo-based panels for structural engineering material need high bonding strength. Based on the requirement from economic situation and actual market the research started. The aim of the research is that resolve the quality problem of bamboo-based structural materials such as the high ratio of delamination and the short use periods of production. According to bamboo’s properties, we should research on special resin for bamboo use and properties evaluation of adhesive system of bamboo-based structural materials. As a result, the bonding strength of bamboo-based structural materials is improved.In this research, the materials were bamboo strips and bamboo board.Using the automatic contact angle meter, the surface free energy of bamboo strips and bamboo board was investigated, the change of surface free energy after being treated by four kinds of coupling agent was investigated as well. The effects of concentration of coupling agent CA5, the hot compress time and the compress temperature on physical-mechanical properties of Laminated bamboo strips lamber (LBSL) were researched, especially the bonding strength of LBSL. The changing of shear strength of bamboo board after being treated by four kinds of coupling agent was studied. The preparatory mechanism of silane coupling agent improving bonding strength of PF resin using on bamboo materials was researched by FTIR.In order to increase the bonding strength of the hot curing resin used on bamboo, the resorcin was used to modify the PF resin into PRF resin. The changing of synthesize condition of hot curing PRF adhesive effects on properties of resin and physical- mechanical properties of LBSL were investigated as well as the effects of different PRF resin on bonding strength of bamboo boards. The thickness and assembly orientation of bamboo curtain effects on physical-mechanical properties of LBSL were investigated either. The optimized cold curing PRF adhesives were gained by investigating different factors effects on properties of resin.The surface free energy of bamboo strips and bamboo board were increased which treated by coupling agent CA5, KH560 and KH602. The surface wettability was improved as well. However, the result is opposite which treated by coupling agent KH550. While all of the bonding strength which surface of bamboo pretreated by 4 kinds of coupling agent was increased. When concentration of KH550 was 0.5% the shear strength was increased significantly. With adding the concentration of KH550, first the shear strength of bamboo board was increased and then decreased. While with adding the concentration of KH560 and KH602, the shear strength of bamboo board was increased. Especial when the concentration of KH560 was 2%, the shear strength up by 400%.About research of the preparatory mechanism of silane coupling agent improving PF bonding bamboo, the result showed that three kinds of silane coupling agent used in the test all can react with the hydroxide group and form chemical bond. The hydroxide group is from the cellulose, hemicellose and lignin of bamboo as well as the PF and PRF resin. The optimized technology was gained to prepare the LBSL which is made of bamboo strips treated by coupling agent CA5.The technology is that density of LBSL board was 0.8g/cm3, concentration of CA5 2%, hot compress temperature 160℃, hot compress time 14min. According to the technology, the properties of LBSL board were as following: modulus of rupture(MOR) 181.2MPa ,modulus of elasticity(MOE)11000.41 MPa, ratio of delamination 0.66%, Thickness swelling after 24 hours water absorption 4.36%.The values of boards were higher than value of standard.Resorcin could increase the shear strength of modified PF adhesive on bamboo board significantly. The shear strength increased up to 50%. However, as the concentration of resorcin change from 1% to 3%, the shear strength of PRF resin changed a little bit. The optimized variable factors of synthesizing PRF adhesive are that: the concentration of resornic was 1.5%, molar ratio of formaldehyde and phenol was 2.0, the concentration of adhesives used to immersion bamboo strips was 30%. According to the technology, the properties of LBSL board were as following: modulus of rupture(MOR) 185.2MPa ,modulus of elasticity(MOE)10800.35 MPa, ratio of delamination 0.58%, Thickness swelling after 24 hours water absorption 4.20%.The values of boards were higher than value of standard.When the cold curing PRF adhesives were synthesized, the more concentration of resorcin the higher the wood failure measuring the dry shear strength, It means that the better bonding strength. However, the effect on 28h boiling water shear strength was small.9% was a critical concentration of resorcin in PRF adhesive. The change of ratio of composition influenced the shear strength and curing time of the PRF adhesive obviously. The molar ratio of phenol and formaldehyde influenced the stability of adhesive significantly, the stability of adhesive was best when the molar ratio of phenol and formaldehyde was 1.5. As the curing agent polyformaldehyde were added more the shear strength and wood failure of specimens were descended rapidly and the curing time of adhesive were shorted. When the concentration of polyformaldehyde was 6%, the shear strength of PRF adhesive was best.The concentration of resornic was 10.5% and 9%, which the two kinds of optimized cold curing PRF adhesives. The shear strength was up to the standard of JAS SE-9.The thickness of bamboo strips effected significantly on physical-mechanical properties of LBSL. With decreasing of the thickness of bamboo strips, the thickness swelling after 24 hours water absorption (24hTS) of LBSL and the ratio of delamination (DR) was decreased obviously. While the MOR , MOE and density of LBSL were increased. The optimized thickness of bamboo strips is 0.8-1.4mm.Orientation of bamboo curtain effected obviously on physical-mechanical properties of LBSL. When bamboo curtains were assembled crossly layer by layer, Each of physical-mechanical properties of LBSL become worse than that of bamboo curtains were assembled parallely. Especially 24hTS and DR of LBSL changed rapidly.更多还原