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人类冬季供暖方式经历了燃火取暖到现代的空调、地热等发展历程。传统的采暖方式利用的是导热和对流的原理,室内温度的分布不能达到理想状态,而地热采暖采用的是热辐射的原理,室内温度由下至上逐步降低,让人感觉很舒适[1-2]。地热采暖技术早在20世纪20年代就开始应用,主要是以钢管或者铜管为加热管进行热辐射供暖,但易腐蚀且成本高[1],电缆、热水逐步应用于地热采暖后,钢管或铜管易腐蚀的问题得到了很好的解决[3-5]。近年来,导电油墨[6]、碳纤维材料的快速发展和应用,使得地热采暖取得了长足的发展,碳晶[7]和碳纤维与绝缘膜复合制成电热膜片逐步应用于室内地热采暖,电热转化效率较高,同时能够辐射出有益人类身体健康的远红外线,具有保健杀菌的作用,但是由于与地板分开安装,占用了居住空间,也在一定程度上增加了安装成本。目前,采用短切碳纤维与植物纤维经造纸工艺制成的面状碳纤维纸发热材料[8-9],厚度只有0.08 mm,可通过控制碳纤维的含量调控发热功率,是一种理想的地热采暖材料。碳纤维纸中大量的植物纤维与木竹材是同质材料,有利于与木竹材胶合,同时碳纤维纸通电电热转换效率达到97%[10]以上,比热水采暖节能[11],能够辐射出有益人类身体健康的远红外线。因此,碳纤维纸在地热采暖领域具有很大的应用前景,但是相关研究相对较少[12-13],需要对竹木复合电热地板进行系统的研究。本研究采用4种常用的不同类型胶黏剂,制备了4种不同的竹木复合电热地板材料,通过对其基本的物理力学性能和电热性能进行检测分析,研究不同胶合体系在电热采暖领域的适用性。
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试验通过测试浸渍剥离强度,分析4种胶黏剂的胶合性能。表 1显示出API制备的电热地板材试样的浸渍剥离强度均不合格,出现了较大的开裂情况。PF和MUF制备的板材试样的胶合性能较为优秀,未出现剥离情况,PE和MUF黏度低,浸润性与渗透性更好,与碳纤维纸的胶合更好一些,因此浸渍剥离强度比其他2种胶更好。EP制备的板材试样出现少量剥离。API主剂黏度高,浸润性相对较差一些,因此在浸渍过程中,水分会通过碳纤维纸内部纤维渗透到板材内部,使得API板材的浸渍剥离强度较低。
表 1 不同胶黏剂竹木复合电热地板的浸渍剥离试验结果
Table 1. Results of glue bond tests for bamboo/wood composite electro-thermal plywood made of different adhesives
胶黏剂种类 浸渍剥离合格率/% PF 100.00 MUF 100.00 API 0 EP 85.71 图 2是4种胶黏剂制备的电热地板材MOR和MOE对比图。可以看出:PF制成的试样MOR和MOE最高,分别为68.25 MPa和5 670.57 MPa。API和EP制成的试样MOR和MOE较为接近,MUF制成的试样MOR和MOE最低,分别为36.37 MPa和4 458.72 MPa。
图 2 不同肢黏剂竹木复合电热地板的静曲强度和弹性模量
Figure 2. MOR and MOE of bamboo/wood composite electro-thermal plywood made of different adhesives
根据标准要求,实木复合地板耐热尺寸变化率长度标准值为0.30%,宽度标准值为0.40%,耐湿尺寸变化率长度标准值为0.20%,宽度标准值为0.30%。图 3中所示的耐热尺寸变化率,长度方向上MUF地板材超出标准值,达到0.32%,其他3种地板材变化率均合格,其中API地板材变化率最低,为0.18%,因此可以看出:三聚氰胺改性脲醛树脂用在电热地板上时需要对其耐热性进行进一步改进。在宽度方向上4种地板材的变化率均符合标准,PF地板材变化率最低,为0.24%,EP地板材变化率为0.34%要高于其他3种地板材。在图 4显示的耐湿尺寸变化率上,API地板材长度变化率为0.25%,超出标准要求,其他3种板材变化率均符合标准要求,API主剂的黏度较高,浸润性相对其他3种胶较弱,水分子易通过碳纤维纸内部纤维渗透到板材内部,导致长度尺寸变化大。4种地板材宽度上变化率均符合标准要求值0.30%。
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对4种胶黏剂制备的电热地板材料的电阻下降率和升降温特性研究发现:胶黏剂对竹木电热地板材料的电学特性有一定的影响。在制备电热地板材料之前:碳纤维纸的电阻均为0.76 kΩ,但是经过压制成板材时,其电阻值出现了降低的现象。如图 5所示:PF压制的电热材料阻值下降率最大,为50.77%,MUF次之,为46.85%,而EP压制的电热材料电阻下降率最小,达到了26.66%。根据梁云等[14]的研究,在制备竹木电热地板材时,压板压力使得碳纤维纸厚度减小,密度增大,因此碳纤维纸内部的碳纤维紧密结合,导电通路的密度增大,导电性能提升,因此碳纤维纸的导电率出现降低。PF黏度低,浸润性好,施胶后能够很好地浸润到木竹材中,使得碳纤维纸在热压过程中能够与木竹材接触面更广,碳纤维结合更紧密,因此导电率下降更多。
图 5 不同肢黏剂竹木复合电热地板电阻下降率
Figure 5. Decrease rate of resistance for bamboo/wood composite electro-thermal plywood made of different adhesives
图 6所示的为4种胶黏剂竹木复合电热地板材在通电和断电条件下的升温与降温情况。升温过程和降温过程中,均是在20 min内升/降温速度较快,能够快速升温至30 ℃以上或者快速降温至30 ℃以下,20 min以后升降温速度逐渐降低。研究结果显示:PF电热地板材料升降温速度最快,在相同时间内,升温达到的温度相比其他3种地板材温度更高,在20 min内温度升至35.04 ℃,降温达到的温度相比其他3种地板材温度更低,20 min内降温至23.52 ℃。梁云等[15]研究结果显示:碳纤维密度增加,碳纤维纸的导电性能就会增加,酚醛胶电阻下降最大,导电性能最好,因此发热速度就会更快,转换的热量就更高。API与EP地板材的升温过程比较相似,尤其是在20 min后升温较为一致,但是API地板材的降温过程最为缓慢,20 min只降至29.08 ℃。
Adhesives used to make bamboo/wood composite electro-thermal plywood
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摘要: 利用酚醛树脂(PF),三聚氰胺改性脲醛树脂(MUF),水性高分子异氰酸酯胶黏剂(API)和环氧树脂(EP)等4种常用胶黏剂,制备竹木复合电热地板材料,对比研究其基本物理力学性能与电热特性。结果表明:PF竹木复合电热地板材浸渍无剥离情况,静曲强度(MOR)和弹性模量(MOE)最高,分别为68.25 MPa和5 670.57 MPa;耐湿热尺寸稳定性均符合标准;电阻值下降率最大,为50.77%;升降温速度最快。API板材浸渍剥离强度不合格;MUF板材的MOR和MOE最低,分别为36.37 MPa和4 458.72 MPa;MUF与API板材耐湿/热尺寸稳定性不合格;EP竹木复合电热地板材电阻下降率最小,为26.66%;20 min为竹木复合电热地板材的快速升降温区间,PE板材的升温速度最快,API板材的降温速度最慢。利用酚醛树脂制备竹木复合电热地板是一种可行的途径。Abstract: To compare basic physical and mechanical properties and electric heating properties of bamboo/wood composite electro-thermal plywood, four kinds of common adhesives:phenol-formaldehyde (PF), melamine-urea-formaldehyde (MUF), aqueous polymer isocyanate (API), and epoxy (EP), were applied. The bamboo/wood composite electro-thermal plywood treated by four kinds of adhesives were tested according to the China national standard and industrial standard:GB/T 18103-2013, LY/T 1700-2007. Results showed that the plywood treated by PF did not peel after the immersion test, and its modulus of rupture (MOR) (68.25 MPa) and modulus of elasticity (MOE) (5 670.57 MPa) were highest. The damp and hot dimensional stability of PF plywood was better than standard requirements, and the decreasing rate of resistance was maximal at 50.8%. Also, the heating and cooling rates with PF plywood were fastest. In contrast, all plywood treated by API peeled after the immersion test, and the MOR (36.37 MPa) and MOE (4 458.72 MPa) of MUF plywood were lowest. The damp and hot dimensional stability with both MUF plywood and API plywood failed. The decreasing rate of resistance for EP treated plywood reached 26.7%, which was the lowest among the four adhesives used; the rapid heating and cooling period of bambool wood composite electro-thermal plywood was 20 min. In general, the heating rate of PF plywood was the fastest, and the cooling rate for API plywood was the slowest. Overall, the phenolic resin (PF) was a suitable adhesive to make bamboo/wood composite electro-thermal plywood.
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表 1 不同胶黏剂竹木复合电热地板的浸渍剥离试验结果
Table 1. Results of glue bond tests for bamboo/wood composite electro-thermal plywood made of different adhesives
胶黏剂种类 浸渍剥离合格率/% PF 100.00 MUF 100.00 API 0 EP 85.71 -
[1] 王洪泉, 张恒奎.室内低温地板辐射采暖技术[J].鞍山科技大学学报, 2003, 26(5):345-348. WANG Hongquan, ZHANG Hengkui. Heat radiant transfer technology used in low temperature room floor[J]. J Anshan Univ Sci Technol, 2003, 26(5):345-348. [2] 曹振华.一种新型的供暖方式:地板辐射供暖[J].应用能源技术, 2007(1):29-30. CAO Zhenhua. A new kind of heating "floor radiated heating"[J]. Appl Energy Technol, 2007(1):29-30. [3] ARMSTRONG T B. Wire mesh floor heating systems[J]. IEEE Trans Ind Appl, 1978, 14(6):498-505. [4] SALVAIS G. Warming customers' hearts and 'oles' with electric floor heating[J]. Natl Floor Trend, 2004, 6(12):52-54. [5] ZHAO Haiqian, WANG Zhonghua, ZHANG Lanshuang. Influence of covering layer on surface temperature of floor radiant heating system[J]. Appl Mech Mater, 2012, 204/208:4260-4263. [6] 殷昊. 采暖用电热膜的研究与室内热工性能分析[D]. 北京: 北京化工大学, 2013. YIN Hao. Research and Indoor Thermal Performance Analysis of Electricthermal Film Used in Heating[D]. Beijing:Beijing University of Chemical Technology, 2013. [7] 刘正明. 一种电热地板: CN201688489U[P]. 2010-12-29. [8] 杨小平, 荣浩鸣, 沈曾鸣.碳纤维面状发热材料的性能研究[J].高科技纤维与应用, 2000, 25(3):39-48. YANG Xiaoping, RONG Haoming, SHEN Zengmin. Study on the properties of carbon fiber facial heating material[J]. Hi-Tech Fiber Appl, 2000, 25(3):39-48. [9] 李灵忻.高性能碳纤维纸及其应用[J].高科技纤维与应用, 2002, 27(5):15-16, 40 LI Lingxing. The application of high performance carbon fiber paper[J]. Hi-Tech Fiber Appl, 2002, 27(5):15-16, 40. [10] 钱学仁, 宋豪, 王丽娟.导电纸的开发与应用[J].纸和造纸, 2006, 25(4):37-40. QIAN Xueren, SONG Hao, WANG Lijuan. Development and application of conductive paper[J]. Paper Paper Making, 2006, 25(4):37-40. [11] QI Hanbing, HE Fuyun, WAN Qiushi, et al. Simulation analysis of heat transfer on low temperature hot-water radiant floor heating and electrical radiant floor heating[J]. Appl Mech Mater, 2012, 204/208:4234-4238. [12] 袁全平. 木质电热复合材料的电热响应机理及性能研究[D]. 北京: 中国林业科学研究院, 2015. YUAN Quanping. Performance and Electric Heating Response Mechanism of Wooden Electric Heating Composites[D]. Beijing:Chinese Academy of Forestry, 2015. [13] 张泽前. 竹木电热复合板的湿热老化研究[D]. 北京: 中国林业科学研究院, 2015. ZHANG Zeqian. The Study of Hygrothemal Aging of Bamboo/Wood Composite Electrothermal Plywood[D]. Beijing:Chinese Academy of Forestry, 2015. [14] 梁云, 孙励志, 胡健.树脂模压固化工艺对碳纤维纸性能的影响[J].中国造纸, 2010, 29(12):19-22. LIANG Yun, SUN Lizhi, HU Jian. Effect of resin molded curing process on the performance of carbon fiber paper[J]. China Pulp Paper, 2010, 29(12):19-22. -
链接本文:
https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2017.02.023