性能奇异的PBO纤维

通过大量文献分析，系统论述了PBO纤维的原料资源、工艺制备、化学结构和力学性能，全面介绍了PBO纤维的应用领域和研究现状，并对其未来研究发展的具体方向进行了分析和展望。     

PBO纤维的扭转疲劳特征分析

文章主要研究PBO纤维的扭转疲劳,使用扫描电子显微镜分析了纤维的疲劳破坏断裂形态,根据纤维的形态和破坏断裂形态讨论了纤维的扭转疲劳破坏机制。实验讨论了预加应力和扭转角度对扭转疲劳寿命的影响。结果表明PBO纤维的扭转疲劳断裂的循环周期数的自然对数同预加张力、扭转角度之间存在线性关系。     

21世纪超级PBO纤维的性能及其应用探讨

介绍了PBO纤维国内外研究状况及其基本情况,它是聚对苯撑苯并双噁唑纤维(poly-p-phenylene benzobisthiazole)的简称,同时阐述了PBO纤维的制备过程,该纤维的性能及其应用领域.鉴于PBO纤维的优异性能及应用领域的广泛性,其发展空间和应用前景将会更为广阔.     

碳纤维原丝材料——PBO纤维

预计2010年碳纤维的市场约为20亿美元,产量约为3.63万t。碳纤维制造工业的主要挑战是成本效率生产。随着成本的降低,其用途将急剧增加。能够直接从PBO纤维制备碳纤维,无需非常费钱耗时的纤维稳定步骤,意味着能够降低成本。PBO纤维的炭化和石墨化产生优质碳纤维,兼有非常好的热和力学性能。与其他原丝生产碳纤维相比,有非常令人感兴趣的远程有序形成。这导致极好的晶格基性能和较低的电阻率。     

造纸用PBO纤维沉析浆粕的制备

采用沉析法制备造纸用PBO浆粕,实验结果表明,沉析法制备PBO沉析浆粕的最佳工艺条件为:PBO浆液浓度为1%,凝固液为稀硫酸,搅拌设备为果汁机,搅拌速度为2000r/min。制备的PBO沉析浆粕具有较大的比表面积和良好的纤维形态,而且可以通过控制凝固液的浓度,得到不同性能的PBO沉析浆粕。     

PBO纤维原纤化的研究

对PBO(聚苯撑苯并二(口恶)唑)纤维原纤化进行了初步研究,确定了原纤化的路线.实验结果表明,在KMnO4浓度为1%的KMnO4/H2SO4体系表面处理和一定的物理剪切下可以实现PB0纤维的原纤化.原纤化纤维结晶度变化很小,但是BET比表面积从5.18m2/g增大到6.30m2/g.     

PBO纤维及其表面处理技术

本文介绍了PBO纤维的制各、结构、性能及其应用．并针对该纤维作为复合材料增强体，与树脂界面粘合性差的特点，综合评述了国内外对PBO纤维的表面处理方法。     

PBO纤维性能的试验研究及其产品开发

将PBO纤维和几种常见阻燃纤维的性能进行对比研究,分析纤维的回潮率、体积比电阻、极限氧指数、热分解温度以及染色等性能。PBO纤维的极限氧指数为68%,热分解温度高达650℃;体积比电阻较大,可用作高温绝缘材料,但纺纱极为困难;PBO纤维的耐化学性好,但染色困难。同时开发出了PBO编织软管和缝纫线,缝纫线强力是同规格芳纶1414的5倍。     

高性能纤维PBO和Kermel的热性能研究

高性能纤维以其高强、高模、耐高温特性广泛应用于各种场合。对照研究了两种高性能纤维PBO和Kermel的热学性能。发现在100,200,300,400℃下处理1．5h,两种高性能纤维的强度和断裂伸长率都发生了下降,但是模量随着温度先增加直到300℃才出现下降。观察这两种高性能纤维热处理后的断裂形貌,发现它们的芯层中都存在原纤特征。     

Evolution of the oxidative and hydrolytic degradation of biscuits' fatty fraction during storage

BACKGROUND: There is little information in the scientific literature on the degradation of the fatty fraction of biscuits during storage. Thus two trials were performed utilizing two different kinds of margarine for a better evaluation of the phenomenon. RESULTS: Covariance analysis of the data evidenced a significant increase of the oxidized triacylglycerols (P < 0.001), together with a significant decrease (P < 0.001) in the amount of monounsaturated and polyunsaturated fatty acids. On the other hand, the level of hydrolytic degradation did not show significant variation. CONCLUSION: Principal components analysis ascertained that about 60% of the variance of the data could be attributed to the quality of the margarine, while about 30% was ascribable to the increase of oxidative degradation induced by storage. Copyright © 2009 Society of Chemical Industry     

PBO沉析浆粕抄造性能的研究

本文研究了PBO(聚对苯撑苯并二(啞)唑)沉析浆粕的抄造性能,讨论了PBO沉析浆粕与短切纤维、原纤化浆粕的配抄性能.实验结果表明,PBO沉析浆粕有着良好的分散性能;沉析浆粕与短切纤维、原纤化浆粕有着良好的配抄性能,当沉析浆粕原纤化浆粕短切纤维=433时,PBO纸页裂断长可达1.21km,撕裂指数3.13mN·m2/g,耐破指数3.19kPa·m2/g.     

生物可降解聚己二酸-对苯二甲酸丁二醇酯纤维的制备及其环境降解性能

为研究生物可降解聚己二酸-对苯二甲酸丁二醇酯(PBAT)的可纺性及纤维降解性能,采用熔融纺丝-牵伸二步法制得生物可降解PBAT纤维,研究了纺丝温度、牵伸倍数对PBAT纤维结晶度、回潮率、力学性能的影响,对比分析了PBAT纤维在不同环境下的降解性能.结果 表明:PBAT的最佳纺丝温度为260℃,且随着牵伸倍数的增加,PB...     

Response of forage fiber degradation by ruminal microorganisms to branched-chain volatile fatty acids,amino acids,and dipeptides

This study evaluated the effect of branched-chain volatile fatty acids (VFA; isobutyric acid, isovaleric acid), amino acids (valine, leucine), and dipeptides (valine-valine, leucine-leucine) on neutral detergent fiber (NDF) degradation by rumen microorganisms in vitro. The CP (%) and in situ NDF degradation rate (%/h) for alfalfa, bermudagrass, and pangolagrass hays, and napiergrass silage were 17.2 and 7.5, 4.7 and 3.1, 8.3 and 5.3, and 9.6 and 3.4, respectively. In vitro NDF digestibility was the lowest for bermudagrass; alfalfa and napiergrass were the highest. When the incubation contained more ammonia initially, digestibilities increased, but relative differences among forages were unchanged. Adding branched-chain VFA (2 mM) to incubations increased digestibilities more than controls on 15 out of 16 occasions. The effectiveness varied with isoacids and forages used. Amino acid (2 mM) or dipeptide (1 mM) addition consistently increased digestibility over controls. Amino acids further increased digestibility over corresponding isoacids on 14 occasions. Improvement in digestibility over control by leucine appeared to be greater than that by valine. Digestibilities with dipeptides were always greater than those with isoacids, except for one case. Dipeptide addition further increased digestibility significantly over corresponding amino acids on only six occasions, while percent improvement in digestibility numerically by dipeptides occurred in 10 cases. Valine-valine seemed to exert different effect than leucine-leucine, depending on initial ammonia availability. The results indicate that dipeptides could be more effective than isoacids and amino acids in improving NDF digestion. Forages with high CP content or rapid NDF degradation rate appeared to respond to additives to smaller degrees.     

Influence of fermentation methods on neutral detergent fiber degradation parameters

The effect of 3 fermentation methods, in situ (IS) in 4 lactating cows (average pH of 5.8), in vitro (IVn) with media pH of 6.8, or in vitro (IVa) with media pH adjusted to 6.0 using citric acid, on fiber degradation parameters was studied using feeds ground to different particle sizes. Corn silage (CS), grass silage (GS), barley grain (B), sugar beet pulp (BP), and rapeseed cake (RC) were ground using a shear mill. Silages were ground through 8-, 4-, 2-, or 1-mm screens, B and BP through 4-, 2-, or 1-mm screens, and RC through 2- or 1-mm screens. The amylase-treated NDF (aNDF) content of samples ground using a 1-mm screen was 399, 431, 197, 480, and 251 g/kg of DM for CS, GS, B, BP, and RC, respectively, but increased with increasing screen size. Materials were incubated for 0, 6, 12, 24, 48, and 96 h IS, IVn, or IVa. Inoculum for IVn and IVa was prepared as a composite from the cows used for IS. The potentially degradable aNDF (D₀), indegradable aNDF (I), lag time (L), and fractional rate of degradation of potential degradable aNDF (k_d) were estimated using PROC NLIN in SAS. Except for RC, fermentation methods affected most degradation parameters, especially k_d and L. The IVn, IVa, and IS methods resulted in k_d values of 0.291, 0.105, 0.080 h⁻¹ and 0.262, 0.107, 0.103 h⁻¹ for BP and RC, respectively, demonstrating a decreasing rate of degradation for these feeds when fermented under suboptimal pH. In CS, GS, and B, no difference was found in k_d between the IVn and IVa methods, which suggests that differences in pH did not alter k_d in vitro. The k_d values obtained for CS, GS, and B were 0.058, 0.109, 0.168, and 0.028, 0.054, and 0.069 h⁻¹ for the IVn and IS methods, respectively, indicating that the IS method using cows fed at production levels can underestimate the potential rate of NDF degradation. Using the IVa method, L was 12.1, 9.1, 7.8, and 2.5 h for CS, GS, BP, and RC, respectively, which was higher than L obtained from the IVn and IS methods for all feeds except B, where L in all methods were near the parameter boundary of zero hour in NLIN. It was concluded that fermentation methods were more important than grinding screen size on estimates for feed aNDF degradation and that the individual aNDF degradation parameters for the 5 feeds were affected differently by fermentation methods.     

PBO纤维纸基复合材料的热老化及高温力学性能研究

本研究采用湿法成形技术制备了聚对苯撑苯并二噁唑（PBO）纸,将其浸渍聚酰亚胺（PI）树脂后,得到PBO纤维纸基复合材料（PBO/PI),随后对PBO/PI进行300℃的老化,并在300℃下测试了其拉伸性能。将PBO/PI与模拟蜂窝格壁的间位芳纶浸渍纸（PMIA/PI）进行对比,分析了老化和高温对PBO/PI和PMIA/PI力学性能的影响。结果表明,在300℃的高温老化下,由于材料微裂纹的产生及扩展,二者拉伸强度均呈下降趋势,但老化前后PBO/PI的强度均比PMIA/PI更强。动态力学性能显示,老化前后PBO/PI的储能模量大于PMIA/PI的储能模量,说明PBO/PI的刚性比PMIA/PI大,在高温下仍不易发生变形。在300℃的高温拉伸测试下,PBO/PI的拉伸强度和保持率均比PMIA/PI要高。PBO/PI在常温及300℃高温下的力学性能均优于PMIA/PI,PBO纤维制备的复合材料可用于需要高的抗变形和热稳定性的承重结构和蜂窝部件中。     

Conditions stimulating neutral detergent fiber degradation by dosing branched-chain volatile fatty acids. II: Relation with solid passage rate and pH on neutral detergent fiber degradation and microbial function in continuous culture

To support improving genetic potential for increased milk production, intake of digestible carbohydrate must also increase to provide digestible energy and microbial protein synthesis. We hypothesized that the provision of exogenous branched-chain volatile fatty acids (BCVFA) would improve both neutral detergent fiber (NDF) degradability and efficiency of microbial protein synthesis. However, BCVFA should be more beneficial with increasing efficiency of bacterial protein synthesis associated with increasing passage rate (k_p). We also hypothesized that decreasing pH would increase the need for isobutyrate over 2-methylbutyrate. To study these effects independent from other sources of variation in vivo, we evaluated continuous cultures without (control) versus with BCVFA (0 vs. 2 mmol/d each of isobutyrate, isovalerate, and 2-methylbutyrate), low versus high k_p of the particulate phase (2.5 vs. 5.0%/h), and high versus low pH (ranging from 6.3 to 6.8 diurnally vs. 5.7 to 6.2) in a 2 × 2 × 2 factorial arrangement of treatments. Diets were 50% forage pellets and 50% grain pellets administered twice daily. Without an interaction, NDF degradability tended to increase from 29.7 to 35.0% for main effects of control compared with BCVFA treatments. Provision of BCVFA increased methanogenesis, presumably resulting from improved NDF degradability. Decreasing pH decreased methane production. Total volatile fatty acid (VFA) and acetate production were decreased with increasing k_p, even though true organic matter degradability and bacterial nitrogen flow were not affected by treatments. Decreasing pH decreased acetate but increased propionate and valerate production, probably resulting from a shift in bacterial taxa and associated VFA stoichiometry. Decreasing pH decreased isobutyrate and isovalerate production while increasing 2-methylbutyrate production on a net basis (subtracting doses). Supplementing BCVFA improved NDF degradability in continuous cultures administered moderate (15.4%) crude protein diets (excluding urea in buffer) without major interactions with culture pH and k_p.     

黄麻/热熔纤维针刺非织造材料的自然降解性能研究

分析了黄麻/热熔纤维针刺非织造材料在不同自然降解环境中的降解性能差异,通过测试其暴露于户外和土壤掩埋(潮土)两种环境中不同时间段后的质量损失率、拉伸强力和纤维之间的缠结状况,研究了其随降解时间变化的降解特性.结果表明:黄麻/热熔纤维针刺非织造材料随降解时间的增加在不同的时间段表现出不同的降解速率,质量损失率增大,外貌形...