生物漂白过程木素结构的红外光谱分析

利用富里埃变换红外光谱技术分析了尾叶桉硫酸盐浆原浆的残余木素、经生物处理后浆的残余木素及生物处理后纸浆经氢氧化钠抽出的木素。结果证实 ,在漆酶 助剂生物处理纸浆的过程碳水化合物不发生氧化 ,而木素的Cα羟基发生氧化产生α -羰基 ;酶作用后纸浆进一步碱处理导致木素溶出。从溶出木素的结构分析 ,推断纸浆中具有紫丁香基结构的残余木素优先发生降解     

OXPXP漂白中活化处理的机理和聚糖降解机理的探讨

经活化处理后纸浆中木素含量降低，残余木素中的羰基和酚羟基增多，聚糖中的羰基也增多。木素大分子的降解和酚羟基的增多提高了木素的反应性能，因而有利于后续漂段木素的脱除和纸浆白度的提高。活化处理后聚糖中羰基的生成是导致铜二胺粘度降低的主要原因，也是导致后续漂段聚糖降解的主要原因之一。纸浆经漂白后结晶度提高，聚糖分子量降低，分子量分布半漂浆范围较窄，全漂浆范围较宽并出现双峰。     

竹子木素在GIF仿酶漂白中的降解机理

研究了竹子木素在GIF仿酶漂白中的降解机理,结果表明,GIF仿酶处理后,竹子木素酚羟基、醇羟基和对羟苯基增加,甲氧基、羰基、愈创木基和紫丁香基减少,β-O-4、β-1、β-5联接发生断裂,芳环开裂。此外,GIF仿酶处理后,竹子木素分子量下降,多分散性提高。     

漆酶与助剂氧化体系降解苇浆残余木素的研究

用溶剂抽提法制取了苇浆残余木素 ,用漆酶 /助剂和氧气与其反应 ,通过甲氧基的测定、元素分析、1 3C -NMR、1 H -NMR和IR分析研究苇浆残余木素与漆酶 /助剂反应前后结构的变化。研究发现苇浆残余木素在反应后其甲氧基、酚羟基减少 ,醇羟基增多 ,木素结构中羰基增多 ,木素的苯环结构发生了开环反应     

马尾松化学热磨机械浆酶法改性研究

利用漆树漆酶/介体体系对马尾松化学热磨机械浆进行生物酶处理及后续H2O2漂白,探索漆酶生物改性最佳工艺条件。结果表明,在漆酶用量为2.0 U/g,2,2’-连氮-二(3-乙基噻唑-6-磺酸)(ABTS)用量0.5%,酶处理温度50℃,酶处理时间60 min时,与对照浆相比,纸浆白度可提高3.0%ISO,抗张指数、撕裂指数分别提高22.5%、7.9%。纤维长度、粗度分析及扫描电镜谱图显示,漆酶处理只发生在纤维表面,有利于表面木素的降解溶出,从而提高了纸浆的白度和可漂性。     

氧化剂和反应条件对漆酶与仿酶一锅法降解木素的影响

研究了氧化剂种类,包括H_2O_2、Na_2S_2O_8、O_2、CH_3COOOH、(NH_4)_2S_2O_8和DMD(dimethyldioxirane),对固载型漆酶和Co(salen)/NaY一锅法催化氧化木素的影响,通过正交和单因素实验对反应条件进行优化,通过GC-MS和GPC、~(31)P-NMR技术分别对芳香类木素降解产物和木素结构进行表征。结果显示,不同氧化剂存在下木素的三种基本结构单元发生了不同程度的降解,降解产物主要为香草醛和丁香醛,其中,Na_2S_2O_8氧化效果最好;一锅法催化氧化木素反应存在有效的协同效应,使一锅法催化氧化效率明显优于单独催化;另外,乙醇在木素催化降解中起到了积极作用。最终的一锅法最佳工艺为:木素用量100 mg,催化剂总用量6 mg,Na_2S_2O_8用量0.4 g,催化剂比例2:1,乙醇用量为0.04 mL,反应时间4 h,pH8。GPC和~(31)P-NMR分析表明,一锅法降解残余木素的分子量显著降低、多分散性趋于1,脂肪族羟基减少,酚羟基含量增加,缩合结构被降解。     

酶解―弱酸解法提取麦草浆残余木素的研究

对非木材浆中残余木素的分离和提纯方法进行了研究。利用酶解―弱酸解两段法提取麦草浆残余木素,研究了酶用量对纤维长度、细小纤维含量、纤维形态、酶解率及木素提取率的影响。研究证明这种方法适用于麦草浆,并得出了最佳酶用量为3mL/g。对提取出的木素经衍生化后,通过磷谱核磁共振(31P-NMR)技术得出木素结构谱图,对木素结构中脂肪羟基、总酚羟基和羧基以及总酚羟基中各酚羟基等功能基团进行定量分析对比,对麦草浆残余木素结构有了更全面的了解。     

固定化漆酶与Co(salen)/NaY组合催化转化木素的研究

把固定化漆酶和Co(salen)/NaY两种催化剂应用于一锅法组合催化转化木素。通过正交和单因素实验对膨润土固定化漆酶和Co(salen)/NaY催化转化木素的工艺进行探讨,结果显示,两种催化剂组合催化效果比不加催化剂或单独催化好,组合催化最佳工艺为:木素用量100 mg,催化剂比例1∶4,反应时间3 h,H_2O_2用量4 mL,催化剂总用量8 mg,pH8.5。通过GC-MS技术对芳香类木素降解产物进行表征,结果显示,芳香类木素降解产物主要为香草醛,其他为丁香醛、2-甲氧基苯酚、4-羟基-3-甲氧基苯乙酮、4-羟基苯甲醛、4-乙酰氧基苯甲醛、2,6-二甲氧基苯酚、4-羟基-3,5-二甲氧基苯甲酸、2-羟基-6-甲氧基苯乙酮、1,2-二苯乙烯。一锅法组合催化显著增强了香草醛的产生。     

针叶木硫酸盐浆中残留木素的GIF体系仿酶降解机理的研究

由于针叶木硫酸盐浆中的残留木素含有大量难降解的LCC结构及其它缩合型木素结构,所以硫酸盐浆的分离木素可以用作难降解型木素大分子的一种结构模型。文章采用Cu2+/吡啶/过氧化氢组成的GIF仿酶体系对马尾松硫酸盐未漂浆的纤维素酶酶解木素(CEL)进行了仿酶降解,并对降解产物进行了分离和化学组成分析。通过FT-IR以及GC-MS测定,解析了CEL在降解过程中的结构变化,并对CEL的仿酶降解机理进行了探讨。研究结果表明:这种仿酶降解方法对浆中残留木素有较强的降解能力,一部分木素大分子被氧化降解为香草醛和香草酸等低分子化合物,使得降解后的产物中羰基和羟基增多。研究发现木素在仿酶体系中存在苯环及其侧链上C-H键的破坏、木素结构中Ca-Cb连接键的断裂、苯环的开环等反应。因此,该项研究可以为开发纸浆的仿酶漂白技术提供理论依据。     

聚木糖酶对纸浆中LCC的辅助去除作用

在造纸用植物原料中,木素与半纤维素之间存在着化学连接,形成木素与碳水化合物复合体（LCC）。在制浆过程中,当蒸煮进行到一定时间后,尤其是在蒸煮的后期,蒸煮液中药液的浓度下降,而聚木糖浓度较高,溶出的聚木糖有一部分又重新回吸到纤维上,而另一部分半纤维素与残余木素形成新的化学结合,形成LCC。聚木糖的回吸对纸浆中残余本素的进一步去除起到了屏蔽作用。聚木糖酶处理纸浆主要是当用内切聚木糖酶降解、溶出回吸到纸浆纤维上的聚木糖,提高了纤维表面的通透性,使漂白处理时漂白剂容易与残余木素作用,有利于残余木素的溶出。同时,由于聚木糖酶分解LCC中的部分聚木糖,使LCC的分子量降低,易于溶出,进而也促进了残余木素的去除,改善了纸浆的可漂性,降低了漂白剂用量和漂白废水中的AOX含量以及有害物质的排放量。但是,聚木糖酶处理需要与纸浆洗涤和化学漂白处理相结合,还不能完全替代纸浆的化学漂白处理。     

Study of effect of old corrugated cardboard in properties of polypropylene composites: Study of mechanical properties,thermal behavior,and morphological properties

The investigation of the economical use of lignocellulose waste, which is one of the environmental problems facing nations, is ongoing. In this study, waste cardboard paper fiber reinforcing polypropylene (PP) composites was developed. In order to modify the PP matrix maleated PP (MA‐g‐PP) a 5 wt% and a grafting rate of 1 and 2 wt% was used as a compatibilizer. The effects of fiber and compatibilizer content as well as graft content are evaluated by mechanical, thermal property measurements, and scanning electron microscopy (SEM). The compatibilizer improved all mechanical properties significantly. Thus, the tensile strength of MA‐g‐PP‐containing composites increases compared to PP/cardboard composites paper content increases. However, the tensile modulus of a PP‐based composite increases with an increase in paper fiber with the compatibilizer having little effect. SEM revealed that the addition of MA‐g‐PP generates strong interactions between a PP matrix and paper fibers. However, the addition of the MA‐g‐PP compatibilizing agent gives a significant improvement on the crystallization of the composites, whereas the compatibilized PP/old corrugated cardboard (OCC) composites have higher crystallinity (Xc) than uncompatibilized PP/OCC composites. The MA‐g‐PP also diminished the water absorption in the composites. J. VINYL ADDIT. TECHNOL., 22:231–238, 2016. © 2014 Society of Plastics Engineers     

Evolution of the structure and mechanical performance of Cansas-II SiC fibres after thermal treatment

Herein, an in-depth analysis of the effect of heat treatment at temperatures between 900 and 1500 °C under an Ar atmosphere on the structure as well as strength of Cansas-II SiC fibres was presented. The untreated fibres are composed of β-SiC grains, free carbon layers, as well as a small amount of an amorphous SiC_xO_y phase. As the heat-treatment temperature was increased to 1400 °C, a significant growth of the β-SiC grains and free carbon layers occurred along with the decomposition of the SiC_xO_y phase. Moreover, owing to the decomposition of the SiC_xO_y phase, some nanopores formed on the fibre surface upon heating at 1500 °C. The mean strength of the Cansas-II fibres decreased progressively from 2.78 to 1.20 GPa with an increase in the heat-treatment temperature. The degradation of the fibre strength can be attributed to the growth of critical defects, β-SiC grains, as well as the residual tensile stress.     

Solid‐state polymerization of melt‐spun poly(ethylene terephthalate) fibers and their tensile properties

The production of high modulus and high strength poly(ethylene terephthalate) fibers was examined by using commercially available melt‐spun fibers with normal molecular weight (intrinsic viscosity = 0.6 dL/g). First, molecular weight of as‐spun fibers was increased up to 2.20 dL/g by a solid‐state polymerization, keeping the original shape of as‐spun fibers. Second, the polymerized as‐spun fibers were drawn by a conventional tensile drawing. The achieved tensile modulus and strength of as‐drawn fibers (without heat setting) were 20.0 and 1.1 GPa, respectively. A heat setting was carried out for the as‐drawn fibers. Tensile properties of the treated fibers were greatly affected by the condition of the heat setting. This was related to the increase of sample crystallinity and molecular degradation during the treatments. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1791–1797, 2007     

Synthesis of high-performance composites by in situ polycondensation and their mechanical properties

High-performance composites of vinylpyridine-styrene copolymers and polyamic acid (PAA) were prepared by the so-called ‘in situ polymerization method’. Poly(4-vinylpyridine-co-styrene) (P4VPy-St) and poly(2-vinyl pyridine-co-styrene) (P2VPy-St) were used as flexible matrix polymers. A molecular composite could be obtained from a polymer pair having an attractive interaction such as a coulombic interaction. Their morphologies were observed by scanning electron microscopy (SEM); mechanical properties of these composites were studied by tensile tests. The PAA content dependence of tensile strength for the composite films obtained by the in situ polymerization method was investigated. The tensile strength of the resulting composite was about 1.5 times higher than that of PAA film. The coulombic interaction between the pyridine moiety in the matrix copolymer and resulting PAA enhanced both the miscibility and mechanical properties of the composites. Furthermore, a polyimide (PI) structure was formed by stepwise heat-treatment and greatly enhanced the tensile strength of the composite films.     

A comparative study on mechanical properties and water absorption behavior of fiber‐reinforced polypropylene composites prepared by OCC fiber and aspen fiber

Fiber‐reinforced polymers have received considerable attention from industry in recent years. Due to the sharp ecological damage, worldwide shortage of trees in many areas and the global demand for fibrous material, there has been growing interest in the use of recycled wood fiber as an alternative or substitute fiber source. The present study investigates the tensile, flexural, Izod impact, and water absorption behavior of Old Corrugated Container (OCC) and aspen (AS) reinforced polypropylene (PP) composites as a function of fiber content. The surface of AS and OCC fibers was modified through the use of MAPP coupling agent. From the studies it was found that mechanical properties increase with increase in fiber loading in both cases. However the addition of wood fibers resulted in a decrease in impact strength of the composites. The water absorption property at varying fiber loading were evaluated and found maximum for the OCC/PP composites. The weight gains for all specimens were less than 3.5%. Finally, the results showed the usefulness of OCC fiber as a good alternative and reinforcing agent for composite. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Strength and failure modes of ceramic multilayers

A model was developed for the prediction of the tensile strength of thin, symmetric 3-layer sandwich specimens. The model predictions rationalize the effect of heat-treatment temperature on the strength of sandwich specimens consisting of an YSZ (Yttria-Stabilized Zirconia) substrate coated with porous NiO-YSZ layers. The model accounts for two different failure modes. Coated YSZ specimens heat-treated below 1200 °C were predicted to fail from flaws in the substrate while specimens heat-treated at higher temperatures were predicted to fail from channeling cracks forming in the coating and propagating into the substrate. These predictions are consistent with microstructural observations of the fracture surfaces. A good agreement was found between the measured strength values and model predictions.     

阳离子改性滑石粉处理OCC纸浆中胶黏物的研究

研究了阳离子改性滑石粉处理废旧瓦楞纸箱(old corrugated containers,OCC)纸浆胶黏物过程的影响因素和作用机理,同时比较了改性前后滑石粉对胶黏物作用效果的差异。结果表明:在一定的滑石粉用量的条件下,适当的纸浆温度和浓度可以促进改性滑石粉的作用效果,当改性滑石粉用量为1.5%,温度80℃,浆浓为20%(wt)时,胶黏物去除率可达到58%;阳离子型助剂能够使滑石粉表面带正电荷,增大滑石粉的比表面积,促进胶黏物吸附改性滑石粉,形成胶黏物―滑石粉微球,有利于胶黏物黏性降低和去除;由OCC手抄片的纸性检测发现:其作用后纸页的紧度、耐破指数、抗张指数和撕裂指数略有下降。     

Using Persulfate Oxidized Chitosan as a Novel Additives in Easy-Care Finishing for Cotton Textiles

Easy care finishing of cotton fabric using glyoxal in the presence and absence of low molecular weight chitosan, i.e., persulfate-oxidized chitosan, as a novel additive along with MgCl₂·6H₂O as an acid catalyst was studied in detail. Major factors affecting finishing reaction were studied with respect to glyoxal, oxidized chitosan, and catalyst concentrations in addition to curing time and temperature of treatment according to the pad-dry-cure method. The obtained results show the following findings: (a) increasing the glyoxal concentration from 5–50 g/l in absence of oxidized chitosan is accompanied by an increase in crease recovery angle and a decrease in tensile strength of the finished fabric, whereas that treated in the presence of oxidized chitosan shows a higher tensile strength and to some extent comparable crease recovery angle with respect to that finished in the absence of it when the concentration of glyoxal increases; (b) increasing the oxidized chitosan concentration is accompanied by decreasing crease recovery angle, whereas the tensile strength increases when glyoxal concentration increases within the range studied; (c) increasing the MgCl₂·6H₂O from 0–15 g/l is accompanied by an increase in the crease recovery angle and a decrease in tensile strength of the finished fabrics in the presence and absence of oxidized chitosan; (d) increasing the time and temperature of curing of the finished fabrics is accompanied by an increase in crease recovery angles and decreases in tensile strength; and (e) the dry wrinkle recovery angle of cotton fabric samples finished in presence of O-chitosan is decreased after washing, and the higher the washing cycle the lower the dry wrinkle recovery angle.     

PTFE乳液制备PTFE/ZrO2微孔膜及性能研究

尝试以聚四氟乙烯（PTFE）乳液为原料制备PTFE微孔膜,选定化学稳定性、热稳定性优异的纳米二氧化锆（ZrO2）作为增强剂以提高微孔膜强度,采用电子万能力学试验机测试了样品的力学强度,用单因素法讨论了纳米ZrO2含量、拉伸比例、热处理温度和热处理时间对微孔膜拉伸强度的影响;同时采用低温等离子体处理PTFE/ZrO2复合微孔膜以改善其表面亲水性。结果表明,PTFE/ZrO2复合微孔膜的拉伸强度与纳米ZrO2含量成正比,与拉伸倍数成反比;其拉伸强度随着热处理温度的升高或热处理时间的延长,呈先增大后减小的变化趋势,分别在310 ℃和10 min时出现最大值;低温等离子体处理的最佳时间为30 s。     

Evaluation of Laser Treatment on Reline-Base Composites

The effects of different laser treatments on some mechanical properties of acrylic resin and soft liner were investigated. A total of 60 test specimens were fabricated according to test requirements. The specimens were roughened with Potassium-ticanyl-Phosphate (KTP), Er:YAG, and Nd:YAG lasers before application of soft liner. The flexural, peel, and tensile bond strengths were measured using a universal testing machine. Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) spectra of surfaces were also obtained to evaluate changes on the lased surfaces. No significant difference was apparent between the tensile bond strength values of the groups. Although peel strength values obtained for each of the laser types were lower than those of the control group, flexural strength values were higher than those of the control specimens. The spectra of specimens showed that lasing led to some chemical changes on the resin surfaces. Physical changes on the treated surfaces were visualized by scanning electron microscopy (SEM) analysis. Results of this study suggest that such treatments may be warranted because of the increase in flexural strength.