【作者】 张兴；

【导师】 欧荣贤； 刘珍珍；

【作者基本信息】 华南农业大学 ， 林业工程， 2023， 硕士

【摘要】 杨木作为重要的速生人工林木材,具有生长速度快、成材时间早、轮伐周期短等优点,但速生杨木材质疏松、力学性能低、尺寸稳定性差,限制其用于建筑结构材及高档家装领域。此外,木材的易燃特性对人类的生命和财产安全造成巨大的威胁,这也引起了政府及社会的广泛关注,同时速生木材存在易腐朽、霉变、虫蛀等缺陷。因此,亟需对速生杨木进行改性以提升其机械性能、阻燃性能和抗生物劣化性能,使其满足更多场景应用的需求。然而,在尽量保持木材原有特性的基础上同时提升速生杨木的机械性能、阻燃性能和抗生物劣化性能仍然具有挑战。针对上述问题,本论文提出了单侧压缩-整体塑合增强杨木性能及功能化研究方案。采用单侧密实化处理工艺提升木材力学性能,并分别浸渍以水性丙烯酸树脂(WAR)复配植酸铵(APA)或四水八硼酸钠(DOT)功能助剂,从而整体固定单侧压缩木材,制备高机械性能、高尺寸稳定性、高阻燃、抗生物劣化性能的改性杨木,使其满足建筑结构材以及高档家具制造等应用领域的需求。主要内容如下:(1)使用植酸(PA)和尿素以摩尔比1:5合成了一种新型生物基植酸铵(APA)阻燃剂。通过改变WAR和APA的质量配比,合成了一系列含N/P的丙烯酸树脂溶液。使用所制备的N/P掺杂WAR溶液整体浸渍杨木,并结合单侧表面密实化处理工艺,成功制备了单侧压缩-整体塑合增强杨木(USD-RA-W)。研究结果表明,相比对照组素材(C-W),USD-RA-W的弯曲强度和冲击强度分别提高了52%和48%,这种显著的力学性能改善得益于表面致密化和含有APA丙烯酸树脂的浸渍改性协同效应。此外,USD-RA-W的表面硬度和耐磨性也得到了明显的改善,相对于C-W,其硬度增加了132%,重量损失减少了22%。由于原位固化的树脂网络可以整体固定单侧压缩木材,防止致密层回弹,因此USD-RA-W表现出优秀的尺寸稳定性。此外,由于生物基APA的引入,USD-RA-W的阻燃性能也得到了明显的提高。UL-94分析结果表明,USD-RA-W的阻燃等级为V-0,极限氧指数达到了50%。锥热量热仪测试结果表明,USD-RA-W的总热释放量和总烟释放量分别下降了32%和77%,同时残炭量达到了41%。(2)在相同的工艺下,调节四水八硼酸钠(DOT)在丙烯酸树脂中的添加量,合成系列DOT复配丙烯酸树脂溶液,使用所复配的系列WAR/DOT溶液来整体浸渍杨木并加以单侧表面密实化,成功制备了杨木改性材(RB-ISD)。探究其在力学、阻燃、生物劣化性能等方面的提升效果。结果表明:经过改性处理的木材样品,力学性能显著增强,RB-ISD的弯曲强度、弹性模量与对照组(C-W)相比分别提高了36%和68%,此外抗冲击强度与对照组相比降低了40%。由于DOT引入,显著提高了杨木速生材的阻燃性,RB-ISD通过UL-94的V-0级测试,其氧指数达到了50%以上。此外,杨木的抗生物劣化性能也得到了显著提高,RB-ISD防霉效果达到100%,平均防腐等级为强耐腐等级,防虫蛀等级为9级以上。综上所述,所制备的RB-ISD杨木改性材具有高阻燃、高力学强度、高尺寸稳定性以及优异的抗生物劣化性能。更多还原

【Abstract】 As an important fast-growing tree species in artificial forests,poplar wood has advantages such as fast growth,early maturity,and short felling cycles.However,the wood quality of fast-growing poplar is poor in terms of low density,low mechanical properties,and poor dimensional stability,making it difficult to be used in building structures and high-end home decor fields.In addition,the flammability of wood poses a considerable threat to human life and property safety,which has also attracted widespread attention from governments and society.Fast-growing wood also has defects such as easy decay,mold growth,and insect infestation.Therefore,it is urgent to modify fast-growing poplar to enhance its mechanical properties,flame retardancy,and resistance to biological degradation,so that it can meet the needs of more application scenarios.However,it is still challenging to improve the mechanical properties,flame retardancy,and resistance to biological degradation of fast-growing poplar while maintaining its original characteristics as much as possible.To address these issues,this research paper proposes a study on enhancing the performance and functionality of Poplar wood through unilateral compression and overall plasticization.The wood’s mechanical properties are improved through unilateral densification and then impregnated with water-based acrylic resin(WAR)and either ammonium phytate(APA)or disodium octaborate tetrahydrate(DOT)functional additives.This results in the overall fixation of the unilaterally compressed wood,producing modified Poplar wood with high mechanical strength,dimensional stability,fire resistance,and resistance to biological degradation.These properties make it suitable for use in applications such as construction and high-end furniture manufacturing.The main contents of the study are as follows:(1)A novel bio-based phytate cyanamide flame retardant curing agent(APA)was prepared by chemical synthesis using phytic acid(PA)and urea(molar ratio of 1:5).By varying the mass ratio of WAR and APA,a series of N/P-containing acrylic resin solutions were synthesized.Using the prepared N/P-doped WAR solutions for monolithic Impregnation of poplar wood,combined with a unilateral surface densification treatment process,unilateral compression-monolithic plasticized reinforced poplar wood(USD-RA-W)was successfully prepared.Research results indicate that compared to the control group material(C-W),the bending strength and impact strength of USD-RA-W was increased by 52%and 48%,respectively.This significant improvement in mechanical performance is attributed to the synergistic effect of surface densification and impregnation modification with acrylic acid resin containing APA.In addition,the surface hardness and wear resistance of USD-RA-W were significantly improved.Relative to C-W,its hardness increased by 132%,and weight loss decreased by 22%.Due to the resin network cured in situ being able to overall fix the unilateral compressed wood and prevent the rebound of the dense layer,USD-RA-W exhibits excellent dimensional stability.Additionally,due to the introduction of bio-based APA,the flame retardancy of USD-RA-W was also significantly improved.The UL-94 analysis results showed that the flame retardant rating of USD-RA-W was V-0,and the limit oxygen index reached 50%.Cone calorimeter test results showed that the total heat release rate and smoke release rate of USD-RA-W decreased by 32%and 77%,respectively,while the residual char reached 41%.(2)Under the same process,a series of DOT compounded acrylic resin solutions were synthesized by adjusting the amount of disodium octaborate tetrahydrate(DOT)added to the acrylic resin.The series of WAR/DOT solutions were used to impregnate poplar wood as a whole and subjected to single-sided surface densification to successfully prepare the modified poplar wood(RB-ISD).The improvement effects of RB-ISD on flame retardancy,mechanical and biological degradation properties were investigated.The results showed that the mechanical properties of the modified wood samples were significantly enhanced.RB-ISD’s bending strength and elastic modulus were increased by 36%and 68%,respectively,compared with the control group(C-W),while its impact strength was reduced by 40%.Due to the introduction of DOT,the flame retardancy of the modified poplar wood was significantly improved.RB-ISD achieved a V-0 rating in UL-94 testing,with an oxygen index of over 50%.In addition,the anti-biological degradation performance of poplar wood was significantly improved,with RB-ISD’s mold prevention rate of 100%,an average anti-rot level of strong durability,and a termite resistance level of"9".In summary,the RB-ISD has high flame retardancy,high mechanical strength,high dimensional stability,and excellent anti-biological degradation performance.更多还原