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刨切微薄竹和旋切竹单板工艺技术研究——程瑞香
木教育 | 15617 view(s) | 2010/02/03

答辩时间:2004年6月9日下午2:00-4:00
答辩地点:南京林业大学机电院二楼报告厅

答 辩 人:程瑞香
指导老师:张齐生 教授

答辩录音:刨切微薄竹和旋切竹单板工艺技术研究



摘 要:本文首次对刨切微薄竹和旋切竹单板制造工艺技术进行了较为系统的研究。

    通过实验室研究和工厂中试确定刨切微薄竹的生产工艺如下:

    将竹片用A胶粘剂或B胶粘剂在热压温度为95℃、单位压力3MPa、热压时间为30min的条件下,通过侧向胶合制成竹层积板。把压制好的竹层积板放入装有60℃水的压力罐中,在压力0.4 MPa的条件下加压软化3 h后,采用鼓风机把竹层积板表面吹干,待竹层积板表面含水率达到14 ~ 20%左右,刨光后采用水性高分子异氰酸酯(API)胶粘剂(API胶粘剂的主剂与交联剂重量比为100:20)在竹层积板厚度方向上胶合成竹集成方材。胶合竹集成方材的压制条件:单位压力3MPa,冷压3h,养生2d。养生后的竹集成方材经水热处理后可在木材刨切机上刨切成微薄竹。

    通过傅立叶变换红外光谱(FTIR)研究表明:经过NaHCO3软化的竹材,半纤维素和木素均受到了破坏。遂采用高温软化竹筒的工艺,确定为120℃ 软化 30 min。经动态热机械分析(DMA)研究表明:高温软化处理的竹材,其复合模量明显降低。在40℃时,经高温软化处理后竹材的复合模量比未软化处理后竹材降低了57.89%,说明高温软化效果非常明显。另外,DMA也表明未软化处理的竹材的Tg为119.8℃, 软化处理的竹材的Tg为88.4℃,软化处理竹材的Tg比未软化处理竹材的Tg下降了26.21%。

    硬度测试结果也表明:经高温软化处理后,竹材的硬度大幅度下降,下降量为42.0~ 54.6%。
对无纺布强化刨切微薄竹和旋切竹单板的工艺进行了研究。刨切微薄竹和旋切竹单板宜自然干燥到含水率30%左右,采用脲醛树脂胶粘剂和聚醋酸乙烯酯乳液的混合胶液,按1:1的比例混合涂于无纺布上,无纺布的单面涂胶量控制在50~80 g/m2。刨切微薄竹和旋切竹单板背面粘贴无纺布的热压工艺为:热压温度为85℃、单位压力0.5MPa、热压时间为25min(一次压10张),中间把压机开挡排汽三次。

    对刨切微薄竹和旋切竹单板贴面复合地板的生产工艺进行了研究。在热压温度为95℃~100℃、单位压力0.4~0.6MPa、热压时间为3~5min的条件下压制的复合地板的主要理化性能符合GB/T 18102-2000和GB/T 15104-1994的要求。

    文中采用差示扫描量热法(DSC)对API胶粘剂的固化机理进行了研究。DSC的研究结果表明:API胶粘剂在与竹材胶接时,竹材中的-OH、竹材和胶粘剂中的水分以及API胶粘剂主剂中所含的-OH都可以与交联剂中的异氰酸酯基发生化学反应,也就是说交联剂中的异氰酸酯与上述反应活性点存在竞争反应。由于异氰酸酯基能与水发生反应,异氰酸酯系化合物不能与水系胶粘剂直接混合使用。因此,在制作API胶粘剂时,为了使其能与水系胶粘剂复合使用,必须选用合适的溶剂,使异氰酸酯基暂时稳定,尽量少地与水发生反应,而在胶接过程中与水系胶粘剂中的主要基料发生交联反应,起到延长API适用期的作用。

关键词:刨切微薄竹,旋切竹单板,无纺布,傅立叶变换红外光谱(FTIR), 竹材,差示扫描量热法(DSC), 软化处理,动态热机械分析(DMA)

Abstract:Technology of sliced and peeled bamboo veneers was studied in this paper.

Bamboo strips were glued and laminated through tangential face to make glued laminated bamboo planks whose hot-pressing condition were that hot-pressing temperature was 95℃、pressure was 3MPa、hot-pressing time was 30 mins. Then glued laminated bamboo planks were placed in a pressure tank at the pressure 0.4 MPa for 3 h to be softened. Softened glued laminated bamboo planks were brought out and blown to the moisture content range of 14% to 20% with a fan and then were planed and adhered into glued laminated bamboo rectangular timber on the direction of radial face with API adhesive (the ratio of matrix with hardener of API adhesive was 100:20). The hot-pressing conditions were as follows: cold-pressing time 3 h; unit pressure 3MPa。

The results of Fourier Transform Infrared Spectroscopy (FTIR) showed that lignin and hemi-cellulose bamboo were destroyed after softening treatment with NaHCO3. So bamboo blocks used for peeled veneer were softened under the temperature of 120℃ for 30 min。

The results of Dynamic Mechanical Analysis (DSC) showed that complex modulus of DMA for softening treatment bamboo under the temperature of 120℃ was apparently decreased. The complex modulus at the temperature of 40℃ after 120℃ softening treatment was decreased with 57.89% compared with no softening treatment bamboo which demonstrated that the effect of softening treatment under high temperature was apparent.

The results of stiffness showed that the stiffness of bamboo strip after softening treatment 30min at 120℃ was decreased with 42.0~ 54.6% compared with no softening treatment bamboo.

The technology of sliced and peeled bamboo veneer with non-woven cloth was also studied in this paper. Sliced and peeled bamboo veneer should be dried to moisture content 30%. The non-woven cloth was spread with the mixture of urea-formaldehyde adhesive and PVAc emulsion (ratio of weight 1:1) and then was put the underside of sliced and peeled bamboo veneer to glue at the hot-pressing condition. The hot-pressing condition was as follows: hot-pressing temperature was 85℃、pressure was 0.5MPa、hot-pressing time was 25min (pressing 10 sheet per hot-pressing cycle) and press was opened to get rid of vapor three times during hot-pressing.

The physical and mechanical properties of floor over-laid bamboo sliced and peeled veneer manufactured at the hot-pressing temperature 95℃~100℃、unit pressure 0.4~0.6MPa and hot-pressing time 3~5mins could satisfied the requirement of China standards GB/T18102-2000 and GB/T 15104-1994.

The adhesion mechanism between Aqueous Polymer Isocyanate (API) adhesive and bamboo was studied by means of Dynamic Mechanical Analysis(DSC) . The results of DSC showed that the –OH which contained in bamboo , matrix of API adhesive , H2O contained in bamboo and API adhesive could react with isocyanate in the hardener. That was to say that there was a kind of competitive reaction between isocyanate in the hardener and above-mentioned reaction spots. Just because isocyanate in the hardener could react with H2O, isocyanate compound could not be used by directly mixing with water-based adhesive. So during making API adhesive, appropriate solvent which could decrease the reaction between isocyanate and H2O in the hardener to make isocyanate react with –OH in the bamboo and API adhesive during practical adhesion must be chose. This solvent had a action of prolonging pot life of API adhesive.

Key words: Sliced bamboo veneer , Peeling bamboo veneer, Non-woven cloth , FTIR (Fourier Transform Infrared Spectroscopy ), Bamboo, DSC (Differential Scanning Calormetry ), Softening treatment, DMA (Dynamic Mechanical Analysis)

编辑:Pi Ning


2010/02/03

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