薄膜层数对热塑性树脂胶合板性能的影响

为了解决人造板产品游离甲醛释放的问题,以高密度聚乙烯(high density polyethylene,HDPE)薄膜作为胶黏剂,采用热压-冷压联用的平压工艺,分别对杨木单板与硅烷改性单板进行胶接,制备了不同HDPE薄膜层数(1,2,3和4层)的热塑性树脂胶合板,并测定了胶合板的物理力学性能。结果表明,薄膜层数对未处理材和硅烷处理材性能的影响变化规律相似。随着HDPE层数的增加,热塑性树脂胶合板的胶合强度无显著变化,耐水性能和抗弯性能逐步改善,耐高温破坏能力降低。当层数相同时,硅烷处理材的综合性能远优于未处理材。对于未处理材,当仅使用2层HDPE薄膜时,胶合强度值超过0.7 MPa,达到Ⅰ类胶合板的用材要求。对于硅烷处理材,当使用1层HDPE薄膜时,板材的综合性能最好,耐高温破坏能力最强,胶合强度达到1.89 MPa,木破率增加至95%,24 h吸水率降低至62.24%,130 ℃时板材的标准化模量值比未处理材提高了80%,tan δmax值对应的温度点由141 ℃升至180 ℃。
In order to alleviated the formaldehyde emission problem in the production and use of wood-based panels, high density polyethylene(HDPE)films were selected as wood adhesives to bond untreated poplar veneers and silane-treated veneers respectively using hot flat-pressing followed by cold flat-pressing. Physical-mechanical properties and thermal stability of the thermoplastic bonded plywood using different HDPE film layers(1,2,3 and 4 layers between every two veneers)were investigated by the mechanical testing machine and dynamic mechanical analysis(DMA). Results showed that the number of HDPE film layers had a similar impact on both the untreated and silane-treated panels. It had a slight effect on shear strength while played an important role in water absorption and bending strength of the plywood. When the HDPE film increased from 1 layer to 4 layers, the water resistance and bending strength of the plywood greatly enhanced. Because of the melting behavior of thermoplastic polymer, the thermal stability of the HDPE film bonded plywood was weakened with the increasing film dosage. The performance of silane-treated panels was much better than the untreated samples at the same number of the HDPE film layers. Only when 2-layer HDPE films were used between every two untreated veneers, the shear strength of the untreated plywood was higher than 0.7 MPa and just met the requirement for type I grade plywood in accordance with GB/T 9846.3-2004. The shear strength, wood failure and 24 h water absorption values were 1.89 MPa, 95% and 62.24%, respectively, when only 1-layer HDPE film was used between every two silane-treated poplar veneers. In addition, the silane treatment led to considerable improvement in thermal stability as proved by higher storage modulus and lagged temperature for tand peak value. Nearly 80% increase in storage modulus at 130 ℃ was acheived and the temperature reaching tan δ peak value increased from 141 ℃ to 180 ℃ when 1-layer HDPE film was used between every two silane-treated veneers