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1.
为提高黑荆树单宁与甲醛反应能力,以纳米TiO 2为催化剂对黑荆树单宁进行紫外光催化降解。以降解物的甲醛结合量为指标,分析催化剂用量对黑荆树单宁降解产物甲醛反应能力的影响。采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)测定黑荆树单宁和具有最大甲醛结合量黑荆树单宁降解产物的分子量和聚合度。采用傅里叶转换红外光谱(FT-IR)对黑荆树单宁及具有最大甲醛结合量黑荆树单宁降解产物的官能团进行表征。结果表明,催化剂用量对降解物甲醛结合量的影响较大,当紫外光功率为400 W、溶液初始质量浓度为60 g/L、反应温度为(35±5)℃、纳米TiO 2添加量为4%(质量分数,以黑荆树单宁质量计)、降解时间为10 h时,降解物的甲醛结合量达到最大值(1.13 g/g),超过了苯酚和间苯二酚的甲醛结合量(0.89 g/g和0.94 g/g),有替代苯酚和间苯二酚与甲醛反应制备木材用胶黏剂的潜能。MALDI-TOF MS分析表明,黑荆树单宁的聚合度和分子量均有明显地下降趋势,降解物分子量分布集中于低分子量部分。FT-IR分析表明,单宁结构中连接棓酰基的醚键、棓儿茶素的苯环骨架、芳醚键、单元间C—C连接键均被破坏。以上结果表明,可通过紫外光催化降解调控黑荆树单宁的化学组成并降低其聚合度和分子量,获得的降解物具有良好的甲醛反应能力。 相似文献
2.
INTR0DUCTI0NOvertheyearsmmpresearchershavefoundUFandPFparticleboardstoedsbitsimilarshorttermphysicalpropeniesatlowhumidityandtemperatUre(DeainandOstInan,l983).DifferentbehaviorpatternsbetWeentl1eresinsemefgeasrelativehumidityandtem-peratUrerise,finallycouldresultinthefailureofboards(R0dwell,l99l).AnumberofworkshavequestionedWhetherhydrolysisistheonlyfactorinvolvedinb0ndfailure.Irlereported(l986)thedifferenteffectsofwettingandredryingonthepropertiesofpureUFandPFresinfilms.Soitmaybeim… 相似文献
3.
In the face of dwindling fossil fuel resources and the environmental imperative to reduce emissions associated with petrochemistry, there is strong demand for a wood composite bonding procedure using natural alternatives. In this study, particleboards were manufactured with a new material adhesive composed of tannin and sucrose, and hot-pressed at 200 °C for 10 min, to a target density of 0.8 g/cm3. We found optimal values for the mat moisture content, the ratio of tannin to sucrose and the resin content of 3–6 wt%, 25/75 and 30–40 wt%, respectively. When the particleboards were manufactured under these optimum conditions, the modulus of rupture and the modulus of elasticity were in the range of 19.6–21.2 MPa and 4.6–5.0 GPa, respectively. The internal bond strength was in the range of 1.1–1.3 MPa. Based on these results, the mechanical properties of particleboard bonded with tannin and sucrose were higher than the requirements of the JIS A 5908 type 18 standard (2003). In the thickness swelling test (TS), the value was in the range of 20–23 %; as the ratio of sucrose and resin content increased, the TS value decreased. The reaction mechanism between tannin and sucrose was studied by fourier transform infrared spectroscopy, and the dimethylene ether bridges were observed. Consequently, it is possible that a tannin and sucrose mixture can be used as a natural adhesive for particleboard. 相似文献
4.
为制备无甲醛的环保型生物基木材胶黏剂,以单宁和纳米SiO2改性脱脂豆粉制备大豆基胶黏剂（DSF）,并分析了改性大豆基胶黏剂的性能。研究结果显示：单宁和纳米SiO2二元复合改性大豆基胶黏剂（DSF-T-SiO2）在固化过程中能够形成稳定的交联结构;TG分析表明单宁和SiO2改性显著提高了胶黏剂的热稳定性;单宁改性大豆基胶黏剂（DSF-T）可提高干态和湿态胶合性能,纳米SiO2改性大豆基胶黏剂（DSF-SiO2）的干态胶合性能略有提高,但湿态胶合性能无明显改善。经分析以25 g脱脂豆粉、 5 g单宁、 0.1 g纳米SiO2和70 g去离子水混合均匀搅拌得到的改性胶黏剂DSF-T-SiO2-2的起始黏度比未改性的DSF降低了79.58%;DSF-T-SiO2-2的固化胶层水溶解率为（27.5±0.05）%,比对照组DSF下降了28.4个百分点。此外,DSF-T-SiO2-2... 相似文献
5.
Amine Moubarik Bertrand Charrier Fatima Charrier Antonio Pizzi Ahmed Allal 《Annals of Forest Science》2009,66(1):109-109
6.
The study was conducted to evaluate effect of ratio of face to core particles on mechanical and physical properties of oriented strand board produced from Ethiopian highland bamboo.Three-layered oriented particleboards were manufactured with 4 proportions of face to core particles at 750 kg/m~3 target density.Ten percent urea formaldehyde resin was used as a binder.Strength and dimensional stability performances of all boards were assessed based on ISO standards.The results showed that modulus of rupture... 相似文献
7.
For manufacturing low-formaldehyde emission particleboard from wheat straw and urea-formaldehyde (UF) resins using urea treatment for indoor environments, we investigated the influence of urea treatment on the formaldehyde emission, physical and mechanical properties of the manufactured particleboard. Wheat straws were treated at three levels of urea concentration (5%, 10%, 15%) and 95℃as holding temperature. Wheat straw particleboards were manufactured using hotpress at 180℃and 3 MPa with two types of UF adhesive (UF-45,UF-91). Then the formaldehyde emission values, physical properties and mechanical properties were considered. The results show that the formaldehyde emission value was decreased by increasing urea concentration. Furthermore, the results indicate that the specimens under urea treatment have better mechanical and physical properties compared with control specimens. Also specimens under urea treatment at 10% concentration and UF-91 type adhesive have the most optimum physical and mechanical strength. 相似文献
8.
Preparation and properties of waste tea leaves particleboard 总被引：4，自引：0，他引：4
Shi Jin-shu Li Jian-zhang Fan Yong-ming Ma Hong-xia 《中国林学(英文版)》2006,8(1):41-45
Urea-formaldehyde (UF) adhesive is the main source of formaldehyde emission from UF-bonded boards. The components in waste tea leaves can react with formaldehyde to serve as a raw material in the production of low formaldehyde emission boards. In our study, waste tea leaves and UF adhesive were employed in the preparation of waste tea leaves particleboard (WTLB). An orthogonal experimental method was applied to investigate the effects of process parameters on formaldehyde emission and mechanical properties of WTLB. The results indicated that: 1) waste tea leaves had the ability to abate formaldehyde emission from boards; and 2) density of the WTLB was a significant factor affecting its modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB). 相似文献
9.
Improvement of physical and biological properties of particleboards by impregnation with phenolic resin 总被引：3，自引：1，他引：3
Summary Particleboards were treated with a low molecular-weight phenol-formaldehyde resin and their properties were evaluated. Particles were dipped into aqueous solutions of resin or sprayed with resin solutions before spraying the conventional phenol-formaldehyde resin adhesive, or sprayed with a mixture of low molecular-weight resin and the adhesive resin in a single step. Though mechanical properties and dimensional stability of the phenolic-resin-treated boards were affected considerably by the incorporated resin loading (IRL), the methods of treatment did not produce significantly different results. After boiling for 2-hours, the boards treated at 10% IRL retained 80% of their strength values in the dry condition. The internal bond strength increased with increasing IRL values, and the boards with 20% IRL showed twice the value of untreated controls at the same level of board density. Treated particleboards showed a dramatic reduction in the rate of swelling even at low resin loading. Results obtained from accelerated laboratory tests of biodegradation suggested that incorporated resin-solids worked well to enhance decay and termite resistance of particleboards. For a brown-rot fungus, the weight loss was substantially reduced at 15% IRL, whereas attack was suppressed almost entirely even at low resin loadings for the white-rot fungus. 相似文献
10.
Dong-heub Lee Myung Jae Lee Dong-Won Son Byung-Dae Park 《Wood Science and Technology》2006,40(3):228-236
The extended use of woods treated with traditional or alternative preservatives for exterior applications requires an assessment
of wood adhesive performance. This study attempts to evaluate the performance of wood adhesives for woods treated with various
waterborne preservatives. Two softwood species, i.e. Korean pine (Pinus koraiensis Sieb. et Zucc.) and Japanese Larch (Larix leptolepis [Sieb. et Zucc.] Gordon) were treated with copper–chrome–arsenic (CCA), CB-HDO, or copper azole (CY), and then bonded with
four different wood adhesives such as urea–melamine–formaldehyde (UMF) resin, melamine–formaldehyde (MF) resin, phenol–formaldehyde
(PF) resin, and resorcinol–formaldehyde (RF) resin. The performance of these adhesives was evaluated by measuring the dry
shear strength of adhesive-bonded wood block on compression. Both UMF and MF resins produced a relatively strong adhesive
strength for CY-treated pine and larch woods. The PF resin also produced good bond strength when bonded with either larch
wood treated with CY or pinewood treated with CB-HDO. The best result was obtained when the CB-HDO-treated woods were bonded
with RF resin. For a better bond strength development, a proper combination of adhesive, preservative, and wood species should
be selected by taking into consideration of the characteristics of these three parameters as well as their interactions. 相似文献
11.
12.
以脱脂大豆粉为原料制备大豆蛋白基胶黏剂(豆胶,S),以普通甲醛制备的酚醛树脂(PF_1)和高浓度甲醛制备的酚醛树脂(PF_2)为交联剂,使用前将两者直接混合得酚醛树脂改性豆胶(PF_1/S、PF_2/S)。利用差示扫描量热(DSC)、红外光谱(FT-IR)、动态热机械性能(DMA)和核磁共振碳谱(~(13) C NMR)分析对产品性能进行了测试与表征。结果表明:等物质的量之比条件下,高浓度甲醛较之普通甲醛制备的酚醛树脂改性豆胶胶合板干、湿剪切强度分别提高4.3%和11.6%,并且强度稳定性好;动态DSC分析表明,PF_2可以降低豆胶体系的固化温度和活化能,与豆胶的交联反应较容易;~(13) C NMR分析表明,PF_2体系羟甲基达88.73%,明显高于PF_1的80.91%;FT-IR分析证实酚醛树脂与豆胶中的氨基发生反应,并且PF_2反应效率更高;DMA分析表明,PF_2/S能够改善胶合产品的力学性能和热稳定性,降低豆胶的固化反应起始温度,提高固化反应速率。 相似文献
13.
This paper describes the features of binderless particleboard manufactured from sugarcane bagasse, under a high pressing temperature of 200–280 °C. Mechanical properties [i.e., modulus of rupture (MOR) and elasticity (MOE) in dry and wet conditions, internal bonding strength (IB)] and dimensional stability [i.e., thickness swelling (TS)] of the board were evaluated to investigate the effect of high pressing temperature. Recycled chip binderless particleboards were manufactured under the same conditions for comparison, and particleboards bonded with polymeric methylene diphenyl diisocyanate (PMDI) resin were manufactured as reference material. The target density was 0.8 g/cm3 for all of the boards. The results showed that the mechanical properties and dimensional stability of both types of binderless boards were improved by increasing the pressing temperature. Bagasse showed better performance than that of recycled chip as a raw material in all evaluations. Bagasse binderless particleboard manufactured at 260 °C had an MOE value of 3.5 GPa, which was equivalent to the PMDI particleboard, and a lower TS value of 3.7 % than that of PMDI particleboard. The MOR retention ratio under the dry and wet conditions was 87.0 %, while the ratio for the PMDI particleboard was only 54.6 %. The obtained results showed the possibility of manufacturing high-durability binderless particleboard, with good dimensional stability and water resistance, which previously were points of weakness for binderless boards. Manufacturing binderless boards under high temperature was effective even when using particles with poor contact area, and it was possible to express acceptable properties to allow the manufacture of particleboards. Further chemical analysis indicated a contribution of a saccharide in the bagasse to the improvement of the board properties. 相似文献
14.
The search for new value-added uses for oilseed and animal proteins led us to develop protein-based wood adhesives. Low-fat
soy and peanut flours and blood meal were hydrolyzed in an alkaline state, and PF-cross-linked protein resins were formulated
by reacting the protein hydrolyzates with phenol-formaldehyde (PF) in solid-tosolid ratios ranging from 70% to 50% hydrolyzates
and 30% to 50% PF. Physical properties of medium density fiberboard (MDF) bonded with protein-based phenolic resins were compared
to those of boards bonded with ureaformaldehyde (UF) and PF resins, and flakeboard bonded with soy protein-based phenolic
resin was compared to PF-bonded board. As MDF binders, adhesive properties of protein-based phenolic resins depended upon
protein content of proteinacious materials. MDF board bonded with blood-based phenolic resin was comparable to PF-bonded board
and met the requirements for exterior MDF. Boards bonded with soy-protein-based phenolic resin met requirements for interior
MDF, while peanut-based phenolic failed to meet some of the requirements. Flakeboard bonded with soy-protein-based phenolic
resins was inferior to PF-bonded board but outperformed PF-bonded board in accelerated aging tests. Although they exhibit
a slow curing rate, the cost effectiveness and superior dimensional stability of protein-based phenolic resins may make them
attractive for some uses. 相似文献
15.
采用不同链长的聚醚多元醇与多亚甲基多苯基多异氰酸酯（PAPI）反应,制备了两种不同结构的水性异氰酸酯（P-C、P-D）,联剂分别加入到氧化玉米淀粉胶黏剂和脲醛树脂胶黏剂中,以改善胶黏剂的胶接性能。通过粘接强度测试研究不同结构、不同用量的水性异氰酸酯对改性胶黏剂的胶接强度和耐水性的影响。实验结果表明：氧化玉米淀粉和脲醛树脂中加入水性异氰酸酯交联剂制备胶合板,胶接强度及耐水性均有显著提高。氧化玉米淀粉胶黏剂中加入10%的水性异氰酸酯P-D后,所制备胶合板的干态剪切强度可达2.64MPa。脲醛树脂胶黏剂中加入7.5%的P-D后,干态、湿态剪切强度分别为1.24MPa和1.23MPa,甲醛释放量为0.31mg/L,达到E0级标准。 相似文献
16.
Straw-wood composites bonded with various adhesive systems 总被引：2，自引：0，他引：2
A. H. Grigoriou 《Wood Science and Technology》2000,34(4):355-365
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 相似文献
17.
In this study, different properties of experimental particleboard produced using a sealed press were determined and were compared
with those for particleboard produced using a conventional press. Three types of binder, namely urea formaldehyde (UF), melamine
formaldehyde (MUF), and polymethylene diphenyl diisocyanate (PMDI), were used for board production. For the UF-bonded boards
produced using the sealed press, the modulus of rupture and the internal bond strength (IB) decreased due to the high temperature
and steam pressure used in comparison to the conditions in a conventional press. However, MUF- and PMDI-bonded boards had
improved IB and thickness swelling (TS). For the PMDI-bonded boards, especially, the TS was further improved and IB was increased
by using a sealed press. PMDI is known to possess superior properties and was confirmed to achieve good properties when used
as a binder for particleboards produced using a sealed press. 相似文献
18.
稻壳的外表面覆盖有二氧化硅膜,使用传统的脲醛树脂(UF)和酚醛树脂胶(PF)生产的100％的稻壳板难以达到木质刨花板的质量指标。本研究采用以异氰酸酯(ISO)改性的脲醛树脂和酚醛树脂胶制造稻壳-木材复合材料。稻壳与木片的混合比例为1:1,施胶量为7％,设计密度0.8g/cm3。试验结果表明,3:4的ISO/UF、2:5的ISO/PF、改性胶粘剂制备的板材的物理力学性能达到国标刨花板二等品的要求;用3:4的ISO/PF改性胶粘剂制备的板材达到优等品的要求。 相似文献
19.
将工业化生产的生物油与聚合4,4’-二苯基甲烷-二异氰酸酯(PMDI)按不同比例混合,并加入一定量的稀释剂形成稳定的PMDI/生物油胶合体系,以此体系作为胶黏剂压制单层结构刨花板,探讨胶黏剂施加量、PMDI/生物油混合比、稀释剂加入量等对刨花板内结合强度、静曲强度、弹性模量、吸水厚度膨胀率、吸水率等物理力学性能的影响。结果表明:加入稀释剂有效地降低了PMDI/生物油体系的黏度,提高了体系在施胶过程中的雾化效果;PMDI/生物油混合比为25∶75的胶黏剂压制的刨花板具有与纯异氰酸酯胶黏剂压制刨花板相似的性能。 相似文献
20.
Wheat straw particleboard bonded with a urea–formaldehyde (UF) resin, usually employed in the manufacture of wood-based particleboards, or with a resin based on epoxidised oil was manufactured using a compression molding machine. The effects of resin type on internal bond strength, flexural modulus, and thickness swelling were examined. The properties of boards using UF resins were poor. Internal bond strength and thickness swelling, linked to adhesion quality, were especially low. The high compatibility between straw particles and oil-based resin was explained in terms of straw surface free energy. In straw, this parameter exhibits a much lower polar component than wood species and leads to higher compatibility with resins based on oil than with water-soluble systems like UF. 相似文献