不同热压方法对无胶竹碎料板力学性能影响

分别采用普通热压和喷蒸热压两种热压方法制备了无胶竹碎料板,对它们的物理力学性能进行了对比研究与分析.结果表明,与普通热压法相比,喷蒸热压法制备的无胶竹碎料板的静曲强度、弹性模量与内结合强度明显提高,吸水厚度膨胀率显著减小,这可能是因为两种热压法热压过程中竹碎料发生的化学变化不同所致.     

红麻秆无胶碎料板的研究

制定了红麻秆(Hibiscus cannabinus)材料在无任何添加剂的条件下制作无胶碎料板的相关工艺,探讨了红麻杆无胶碎料板的密度与其物理力学性能(静曲强度、内结合强度、吸水厚度膨胀率)间的关系,根据国家标准GB/T4897.2-2003干燥状态下使用的普通刨花板要求评价了红麻杆无胶碎料板的性能,结果表明:当密度大于0.7g/cm3时,红麻秆无胶碎料板的性能即能够满足标准要求。并使用傅里叶红外光谱研究了其在热压过程中的官能团变化,进而初步分析红麻秆无胶碎料板的胶合机理。     

蒸爆法棉秆无胶纤维板热压工艺初探

以棉秆为原料,经过蒸爆解纤处理后热压制成无胶纤维板.研究了密度为0.85g/cm3、板厚为4mm的无胶纤维板热压工艺.结果表明:在试验范围内较优的热压工艺为:板坯含水率12%、热压温度210℃、热压时间60s/mm.     

喷蒸真空热压水溶性酚醛胶杨木大片刨花板

我国防水人造板生产目前普遍采用酚醛树脂胶（PF），热压周期长，生产效率低。笔者采用南京林业大学饱和蒸汽喷蒸试验压机，压制水溶性PF胶杨木大片刨花板。结果表明，采用喷蒸真空热压（SIVP）技术，热压时间可缩短到传统热压的35％左右；板的吸水厚度膨胀率（TS）缩小33％；在相同施胶量下，板的内结合强度（IB）提高的15％，同时甲醛释放量降低约24％；但板的抗弯性能有较大幅度的下降；此外，板材芯层最低密度值比传统热压的板增高，断面密度分布趋于均匀。     

汽爆压力对无胶棉秆纤维板性能的影响

不添加任何化学助剂,在不同汽爆压力下进行棉秆解纤,将解纤后的纤维热压制成无胶纤维板.分析了汽爆压力对棉秆纤维形态、化学成分以及无胶纤维板产品性能的影响.结果表明,随着汽爆压力的增大,纤维分离程度提高,纤维中游离酸、游离糖及游离醇的质量分数含量增加,试板的内结合强度增大,但静曲强度和弹性模量则减小.     

喷蒸真空热压对水溶性PF胶在杨木大片刨花中的渗透及对板性能的影响

反射荧光显微镜可观察水溶性酚醛树脂胶（ＰＦ）在杨木大片刨花中的渗透情况。通过显微观察及板内结合强度测试,结果表明,蒸汽冷凝水对水溶性ＰＦ树脂胶有稀释作用,改变胶的流动和渗透性能。采用喷蒸真空热压工艺时,须对水溶性ＰＦ胶进行改性,ＰＦ的分子量要大于传统工艺所要求的分子量,而且有必要采用适当的喷蒸保持时间     

麦秸无胶碎料板制备工艺研究

以麦秸碎料为主要原料,采用漆酶水浴与干法两种不同处理方法压制麦秸无胶碎料板,研究热压温度、热压压力和热压时间对板材物理力学性能的影响。试验结果表明:影响麦秸无胶碎料板物理力学性能的主要因素是热压温度;水浴处理方法压制碎料板的物理力学性能优于干法压制的碎料板;漆酶水浴处理方法较优的热压工艺参数为漆酶用量43.6U/g,含水率10%,热压温度170℃,热压压力3~4MPa,热压时间20~25min。     

Comparison Between Steam-Injection Pressing and Conventional Hot Pressing in Producing Poplar Particleboards Part 2 : To improve the dimensional stability of particleboards with steam-injection pressing

该研究采用传统热压和喷蒸热压两种方法来生产杨木刨花板．刨花板内施加１０％的脲醛树脂胶（ＵＦ），目标厚度分别取１０，１５，２０，和２５ｍｍ，热压温度均为１８０℃．喷蒸热压时饱和蒸汽的压力为０．３～０．５ＭＰａ，每种厚度下喷汽时间一定，取两个热压时间；传统热压时每种厚度下各取４个热压时间．然后测定试件的吸水厚度膨胀率、吸水率、密度、含水率及力学性能．本文重点讨论了喷蒸热压对杨木刨花板尺寸稳定性的影响．结论认为：喷蒸热压相对于传统热压，在保证刨花板的强度、缩短热压时间的条件下，明显改善了杨木刨花板的尺寸稳定性．     

纤维板喷蒸热压传热传质规律研究

采用喷蒸热压方式对中低密度纤维板坯进行热压,测定并记录热压过程中板坯中心层开始升温的时间、达到100℃的时间、稳定温度及达到稳定温度的时间、热压结束后板坯的含水率;分析蒸汽压力、目标厚度、目标密度、热压温度及板坯含水率对其影响,得出了中低密度纤维板喷蒸热压传热传质的基本规律.     

棉秆碎料轻质保温板性能研究

以棉秆为原料,经浸泡、蒸煮、搓磨分丝成纤维束,选择不同规格的棉秆碎料和不同比例的脲醛树脂胶,按照不同的目标密度,在设定的热压胶合条件下进行正交试验。通过KHQ-002H木材和人造板自动万能力学试验机和FWDR准稳态导热系数测试仪进行检测,得到静曲强度、弹性模量和导热系数等相关参数,再对其进行方案优化,得出工艺参数为密度0.4 g/cm3、施胶量10%、棉秆丝长度规格为10~15 mm的轻质碎料保温板的静曲强度、弹性模量和导热系数分别为13.3 MPa、1 353 MPa和0.134 w/m·℃。结果表明,低密度的棉秆碎料保温板导热系数接近或低于常用的建筑板材,具有良好的隔热保温性能,而且其力学性能能够满足墙体内衬保温材料以及非承重墙的隔墙材料的强度要求。     

Properties of kenaf core binderless particleboard reinforced with kenaf bast fiber-woven sheets

Kenaf composite panels were developed using kenaf bast fiber-woven sheets as top and bottom surfaces, and kenaf core particles as core material. During board manufacture, no binder was added to the core particles, while methylene diphenyldiisocyanate resin was sprayed to the kenaf bast fiber-woven sheet at 50 g/m² on a solids basis. The kenaf composite panels were made using a one-step steam-injection pressing method and a two-step pressing method (the particleboard is steam pressed first, followed by overlaying). Apart from the slightly higher thickness swelling (TS) values for the two-step panels when compared with the one-step panels, there was little difference in board properties between the two composite panel types. However, the two-step pressing operation is recommended when making high-density composite panels (>0.45 g/cm³) to avoid delamination. Compared with single-layer binderless particleboard, the bending strengths in dry and wet conditions, and the dimensional stability in the plane direction of composite panels were improved, especially at low densities. The kenaf composite panel recorded an internal bond strength (IB) value that was slightly low because of the decrease of core region density. The kenaf composite panel with a density of 0.45 g/cm³ (one-step) gave the mechanical properties of: dry modulus of rupture (MOR) 14.5 MPa, dry modulus of elasticity (MOE) 2.1 GPa, wet MOR 2.8 MPa, IB 0.27 MPa, TS 13.9%, and linear expansion 0.23%.     

喷蒸热压刨花板断面密度分布的研究

通过喷蒸热压工艺与常规热压工艺压制刨花板的试验结果,分析了刨花板断面密度分布情况与刨花板性能的关系,验证了喷蒸热压工艺的优点。     

Development of boards made from oil palm frond II: properties of binderless boards from steam-exploded fibers of oil palm frond

Binderless boards were prepared from steam-exploded fiber of oil palm(Elaeis guineensis Jacq.) frond at six levels of explosion conditions. Their properties were investigated and evaluated. The mechanical properties (i.e., modulus of rupture, modulus of elasticity, and internal bonding strength) of the boards increased linearly with increasing board density as the usual hardboard. The boards made from fibers treated under a steam explosion condition of 25 kgf/cm² (steam pressure) and 5 min (digestion period) exhibited the maximum strength. These boards at a density of 1.2 g/cm³ met the requirement of S-20 grade of JIS A 5905 — 1994 (fiberboard). Thickness swelling of the boards ranged from 6% to 14% under the JIS A 5908 — 1994 (particleboard) test condition and showed no significant changes with increasing board density. The main bonding strength of the board is believed to be due to a ligninfurfural linkage. Considering the chemical components of oil palm frond, which is rich in hemicellulose, there seems to be a good possibility for producing binderless boards using steam-exploded fibers of oil palm frond.This study was presented in part at the 2nd International Wood Science Seminar, Serpong, Indonesia, November 1998     

Development of binderless particleboard from kenaf core using steam-injection pressing

Binderless particleboards were successfully developed from kenaf core using the steam-injection press. The effects of board density, steam pressure, and treatment time on the properties of the board were evaluated. The target board densities were relatively low, ranging from 0.40 to 0.70g/cm³. The properties [i.e., moduli of rupture (MOR) and elasticity (MOE) in both dry and wet conditions, internal bonding strength (IB), and water absorption (WA)] of the boards increased linearly with increasing board density. Steam pressure and treatment time also affected the board properties. The bending strength and IB were improved with increased steam pressure. A long steam treatment time contributed to low thickness swelling (TS) values and thus better dimensional stability. The appropriate steam pressure was 1.0MPa, and the treatment time was 10–15min. The properties for 0.55g/cm³ density boards under optimum conditions were MOR 12.6MPa, MOE 2.5GPa, IB 0.49MPa, TS 7.5%, and wet MOR 2.4MPa. Compared with the requirement of JIS 5908, 1994 for particleboard, kenaf binderless boards showed excellent IB strength but relatively poor durability.Part of this report was presented at the 19th Annual Meeting of the Japan Wood Technological Association, Tokyo, October 2001     

Development of high-performance UF-bonded reed and wheat straw medium-density fiberboard

Urea formaldehyde resin-bonded reed and wheat straw fiberboards were produced from the fibers made under different steam cooking conditions in refining processes at densities of 500 and 700kg/m³. The effect of steam cooking conditions on the board properties was examined. The steam pressure and cooking time for reed and wheat straws were 0.4MPa/10min and 0.4MPa/5min, respectively, and 0.6MPa/3min and 0.6MPa/10min for both straws. The effect of steam cooking treatment before the fiber refining process on the wettability and weight losses of the straws was also investigated. The results indicated that the mechanical properties and linear expansion of the straw medium-density fiberboard (MDF) were improved with increasing steam cooking pressure and time during the refining process, whereas the thickness swelling (TS) did not vary much. The wettability of the straws was improved by cooking treatment. The steam cooking conditions had little effect on the wettability of the straw surfaces. For reed and wheat straws, the weight losses increased with increasing steam pressure and cooking time. In addition, it was found that the properties of MDF were significantly higher than those of particleboard, especially the internal bond (IB), where the IB values of MDF were more than 10 times higher than those of particleboard. All the properties of the straw MDF, except the TS of wheat board, can meet the requirement of JIS fiberboard standard. The high performances of MDF could be due to the improved wettability and the removal of extractives during the refining process.     

Properties of particleboard produced using a sealed press

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.     

烟秆/木材刨花板的初步研究烟秆

初步探讨了实验室条件下烟秆/木材刨花板的生产工艺,研究了热压时间、施胶量、密度、木刨花加入量等因素对板材的静曲强度、内结合强度、吸水厚度膨胀率的影响.实验结果表明,烟秆/木材刨花板的静曲强度和吸水厚度膨胀率较纯烟秆刨花板有所提高,内结合强度相差不大.     

Effects of mat moisture content and press closing speed on the formation of density profile and properties of particleboard

Isocyanate resin-bonded 0.5 and 0.7 g/cm³ lauan (Shorea sp.) particleboards were produced from mats with uniform and distributed moisture content (MC) distributions, using three hot press closing speeds. The effects of these processing variables on the formation of density profile in particleboard and board properties were analyzed statistically. A definition of the density profile was introduced, and the correlations among the various defining factors were established. The results are summarized as follows. (1) The peak density (PD) of particleboard could be increased, with a slight reduction in the core density (CD), using mats with different MC distributions. (2) In a conventional density profile, CD and PD are highly dependent on the board mean density (MD); and the gradient factor (GF), peak distance from the faces (Pdi), and peak base (Pb) are significantly correlated to each other, at the 99% significance level. (3) Greater press closing speed reduces Pdi and Pb, with an increase in GF. (4) Greater press closing speed could increase the PD in board of low MD, with minimal effect on CD. (5) The modulus of elasticity (MOE) of particleboards from mats with high MC near the faces were consistently higher than those from mats with uniform MC, irrespective of the press closing speed, whereas their modulus of rupture (MOR) became indifferent at higher MD under slow and fast closing speeds. (6) Sanding does not improve the MOR and MOE of particleboard significantly.     

Development of binderless fiberboard from kenaf core

Binderless fiberboards with densities of 0.3 and 0.5 g/cm³ were developed from kenaf core material using the conventional dry-manufacturing process. The effects of steam pressure (0.4–0.8 MPa) and cooking time (10–30 min) in the refining process, fiber moisture content (MC) (10%, 30%), and hot-pressing time (3–10 min) on the board properties were investigated. The results showed that kenaf core binderless fiberboards manufactured with high steam pressure and long cooking time during the refining process had high internal bond (IB) strength, low thickness swelling (TS), but low bending strength values. The binderless fiberboards made from 30% MC fibers showed better mechanical and dimensional properties than those from air-dried fibers. Hot-pressing time was found to have little effect on the IB value of the binderless board at the refining conditions of 0.8 MPa/20 min, but longer pressing time resulted in lower TS. At a density of 0.5 g/cm³, binderless fiberboard with the refining conditions of 0.8 MPa/20 min recorded a modulus of rupture (MOR) of 12 MPa, modulus of elasticity (MOE) of 1.7 GPa, IB of 0.43 MPa, and 12% TS under the optimum board manufacturing conditions. Part of this article was presented at the 54th Annual Meeting of the Japan Wood Research Society, Hokkaido, August 3–5, 2004