竹材气相氟化处理的尺寸稳定性和防霉性能

Dimensional stability and mold resistance to bamboo treated in gaseous phase fluorination

【目的】以氟气作为改性剂,利用其较强的渗透性和反应活性与木材细胞形成化学键,达到长效存留和改性竹材的目的。【方法】将4年生的毛竹Phyllostachys edulis置于管式反应器中,通入质量百分比为25%的氟气,在150℃下反应4 h。为了进一步提高氟化效果,先用不同质量分数硫酸预处理竹材,再进行高温氟化处理。【结果】氟化反应主要发生在木质素上。氟化材红外光谱说明氟化处理材在739 cm-1处产生了表征碳氟键(C—F)的新峰,浓硫酸预处理氟化竹材在878和1088 cm-1出现木质素苯环氟多取代(C—Fn)吸收峰。X射线光电子能谱中结合能为687.8 eV的C—F特征峰和689.2 eV的C—F2特征峰证实了氟化处理竹材中C—Fn键的生成。热氟化试块在3次吸湿-干燥和吸水-干燥循环中平均抗胀率分别为19.1%和7.5%。硫酸预处理能进一步提高氟化材的尺寸稳定性,其中20 g·kg^-1的硫酸预处理氟化材效果最为显著,平均抗胀率分别达31.0%和15.8%。防霉测试显示氟化处理材对木霉Trichoderma viride、青霉Penicillium citrinum和黑曲霉Aspergillus niger混合霉菌的抑制效果不明显,硫酸预处理后的氟化材防霉性能有所增加。【结论】竹材气相热氟化能对竹材内部进行改性,处理后的竹材尺寸稳定性和防霉性能均优于未处理竹材。利用氟气对竹材进行气相改性是一种渗透性强、反应活性高的竹材改性新技术。

[Objective]The strong permeability and reactivity of gaseous fluorine supposedly helps form chemical bonds between fluorine and bamboo.This aim is to increase the leaching resistance of gaseous fluorine[Method]The four-year-old bamboo(Phyllostachys edulis)was heated in a tubular reactor at 150℃and treated with 25%fluorine for 4 h.To improve the fluorination effect,bamboo was pretreated with sulfuric acid at different concentrations before the fluorine thermo treatment.Analysis included fourier transformed infrared spectra and X-ray photoelectron spectroscopy.Tests on mold resistance for fluorinated bamboo with mixed fungi of Trichoderma viride,Penicillium citrinum,and Aspergillus niger were conducted.[Result]The chemical analysis and testing of fluoride bamboo showed obvious changes in lignin.Fourier transformed infrared spectra demonstrated that the new peaks at 739 cm-1 were C—F(carbon-fluorine)monosubstituted bonds;whereas,concentrated sulfuric acid pretreated fluorinated bamboo showed double C—F peaks at 878 and 1088 cm-1 caused by the polysubstitution of C—F bonds on the benzene ring of lignin.Binding energies of 687.8 eV(C—F)and 689.2 eV(C—F2)in X-ray photoelectron spectroscopy confirmed the presence of the C—F bond in fluorinated bamboo.The dimensional stability of treated bamboo was tested under three moistening-drying cycles and water soaking-drying cycles,respectively.The average anti-shrink efficiency(ASE)for three cycles of thermo fluorinated bamboo was 19.1%for moistening-drying and 7.5%for water soaking-drying.Sulfuric acid pretreatment further improved dimensional stability of thermo fluorinated bamboo where 20 g·kg^-1 sulfuric acid pretreatment behaved the best with a corresponding ASE of 31.0%for moistening-drying and 15.8%for water soaking-drying.Tests on mold resistance for fluorinated bamboo with mixed fungi of T.viride,P.citrinum,and A.niger,showed no obvious anti-mold efficacy;whereas,for fluorinated bamboo pretreated with sulfuric acid there was slight improvement.[Conclusion]Thus,with gaseous-phase thermo fluorination,a new way of bamboo modification with strong permeability and high reactivity,dimensional stability and mold resistances of treated bamboo were better than the controls making them effective for inner modification of bamboo.