热定形工艺对高强型聚酯工业丝结构性能的影响

为探究不同热定形温度获得的高强型聚酯工业丝性能差异的内在结构因素,对3种高强型聚酯工业丝的结构性能进行对比。采用小角X射线散射和广角X射线衍射方法对其多尺度微观结构进行研究,结合力学性能及热收缩等结果,明确不同热定形工艺对高强型工业丝结构性能的影响。结果表明：热定形温度主要影响聚酯工业丝非晶区取向和片晶结构;相比于高强中缩(HTMS)和高强(HT)聚酯工业丝,高强低伸型(HTLE)聚酯工业丝的热定形温度低,高倍牵伸产生的伸直非晶区分子链在较低热定形温度下并未及时排入晶格形成结晶,而发生了小幅的回复,导致HTLE聚酯工业丝表现出非晶区取向高、结晶度低、晶粒尺寸小与片层倾斜角较大的结构特点,从而使断裂伸长率最小、初始弹性模量最大、尺寸稳定性差。     

后加工中热处理张力变化对高模低收缩涤纶工业丝结构与性能影响

针对后加工热处理过程中高模低收缩型(HMLS)涤纶工业丝受热引起性能变化的问题,分别将HMLS涤纶工业丝置于150 ℃不同预加张力(0~0.10 cN/dtex)条件下热处理5 min,分析热处理前后样品的构象变化,阐明其性能调控的结构因素。结果表明:随着预加张力的减小,HMLS涤纶工业丝的断裂强度略有减小,初始模量和5%形变下的断裂强度明显降低,而断裂伸长率明显增大;热处理主要影响非晶区的结构变化,导致HMLS涤纶工业丝的非晶区取向变低、反式构象含量变小、片晶长周期变小以及非晶区厚度变小;可通过施加一定的预加张力有效抵消HMLS涤纶工业丝在后加工中受热时的收缩应力,从而降低非晶区分子链的运动能力,使得力学性能及非晶区结构变化幅度减小。     

P92钢高温蠕变行为与断口形貌组织分析

在600℃、650℃不同应力水平下完成P92钢的高温蠕变试验,观察了蠕变断裂后断口的微观结构,利用幂律关系式拟合出了应力指数n,并计算出损伤容许量系数λ。研究表明,蠕变断裂时间与加速蠕变阶段开始时间的比值范围在1.41~1.82。根据应力指数n及损伤容许量系数λ,引起蠕变加速及最终断裂原因是由于位错的运动。应力指数n随着温度的升高呈下降趋势,是由于位错密度的降低和Laves相的形成所致。微观断口具有明显的韧窝断裂特性,部分韧窝底部存在第二相粒子。Laves相的析出强化是影响蠕变稳定性的主要因素。温度水平较高时,Laves相的快速析出降低了位错密度,使得蠕变断裂强度下降,加速了蠕变断裂。     

应用二维X射线衍射法测定涤纶工业丝结晶和取向行为

为确立涤纶工业丝微观结构与力学性能之间的关系,建立一种有效的测试方法至关重要。利用二维X射线衍射法研究了普通高强型（HT）、低收缩型（LS）、超低收缩型（SLS）3 种不同种类涤纶工业丝的晶态结构和晶区取向度,并分析了对其性能的影响。结果表明：干热收缩率最小、尺寸稳定性最好的SLS 型工业丝结晶度和晶粒尺寸最大,但其晶区取向最小;而断裂强度最高、断裂伸长率最小的HT 型工业丝结晶度和晶粒尺寸最小,晶区取向却最大;LS 型工业丝则介于二者之间。综合分析可知,结晶度和晶粒尺寸主要影响涤纶工业丝的干热收缩率,晶区取向度则影响涤纶工业丝的断裂强度、断裂伸长率以及弹性模量。     

多轴向经编玻璃纤维织物增强复合材料的蠕变特性研究

玻璃纤维增强复合材料在长期服役条件下的蠕变行为会导致结构件发生形变,进而对材料稳定性产生很大的影响,因此对其蠕变性能的研究很有必要。分别以三轴向和四轴向经编玻璃纤维织物为增强体,环氧树脂为基体,采用真空辅助树脂传递模塑(vacuum assisted resin infusion, VARI)成型方法制备复合材料试样。研究不同应力水平下复合材料试样的弯曲蠕变规律,对蠕变曲线进行线性拟合,预测材料蠕变寿命。基于试样断裂失效形貌图,分析蠕变损伤情况,揭示蠕变特性。结果表明,当施加小于弯曲断裂强度值80%的应力时,复合材料蠕变历经2个阶段,减速蠕变阶段,应变随时间延续而增加,但增速逐渐减小;匀速蠕变阶段,应变随时间延续而匀速增加。当施加大于弯曲断裂强度值80%的应力时,2种复合材料在历经减速蠕变和匀速蠕变阶段后,进入加速蠕变阶段,此阶段应变随时间延续而快速增加,直至试样破坏失效。通过蠕变试验,验证复合材料在弯曲断裂强度值80%的应力水平下蠕变寿命预测结果的准确性。结果显示,三轴向和四轴向复合材料试样分别在施加应力2.83 h和37.40 h后发生蠕变断裂,蠕变寿命预测结果与试验结果的误差较小...     

水性聚酯对氧化淀粉膜力学性能的影响

研究水性聚酯对淀粉浆膜结构和力学性能的影响.采用浇注成膜法制备了不同水性聚酯含量的氧化淀粉/水溶性聚酯混合膜.通过衰减全反射红外法、X-射线衍射法探讨了水性聚酯对淀粉浆膜结构的影响,并测定了浆膜的机械性能.结果表明,水性聚酯促进了氧化玉米淀粉分子间氢键的形成,增加了玉米氧化淀粉分子的链缠结和无定形区,而氧化玉米淀粉与水性聚酯之间并没有氢键形成;水性聚酯含量增加会使浆膜结晶度逐渐下降,但并未对其结晶形态造成影响;水性聚酯降低了浆膜的初始模量,提高了浆膜的断裂伸长.指出:水性聚酯的加入有助于改善淀粉浆膜的脆硬性.     

有机溶剂处理后丝素纤维的微细结构变化

概述 在前几届国际丝绸会议上,我们已就有机溶剂作用后丝的质地和染色性能的改善从分子聚集结构的变化加以了讨论。在这篇报告中,我们从相互作用参数X_(1.a)(溶剂作用后丝的非晶区与水之间),非晶区膨胀的温度依赖性及晶相与非晶相的双折射和取向度几个方面,对有机溶剂处理后丝蛋白纤维的变化加以了探讨。在这些实验结果的基础上,我们发现经有机溶剂     

钛系聚对苯二甲酸乙二醇酯的增黏行为及其性能

为了拓宽钛系聚对苯二甲酸乙二醇酯(PET)在聚酯工业丝领域的应用,通过超高效聚合物色谱-多角度激光光散射联用法研究其在不同温度下的增黏行为,建立增黏温度与钛系PET分子质量及其分布的关系,并利用紫外-可见分光光度计和差示扫描量热仪研究增黏PET的色相和热性能。结果表明:钛系PET分子质量随增黏温度的升高而升高,且色相受温度影响明显;增黏所需时间随温度升高而下降,270 ℃反应20 min的钛系PET重均分子量与220 ℃反应10 h时的相当,分子质量升高导致聚酯结晶性能和熔点下降;增黏温度超过熔点后,分子质量分布随温度升高而变窄,且分子质量可达到聚酯工业丝要求,高分子质量窄分布钛系聚酯的研究对其在工业丝领域的应用具有重要意义。     

共聚型阻燃聚酯工业丝的纺丝成形

为了纺制兼具良好阻燃与力学性能的共聚型阻燃聚酯工业丝，在分析高分子量阻燃共聚酯流变特性以及量化不同纺丝温度条件下共聚酯热降解程度的基础上，设计和优化熔融纺丝工艺。对纺制的阻燃工业丝力学性能与阻燃性能进行测试，并采用X-射线衍射和声速纤维取向测量仪对纤维的微细结构进行测试分析。结果表明：相较纯PET,共聚酯熔体黏度较低，温敏性更为明显。采用低的纺丝温度(285℃左右),熔体黏度对纺丝压力影响小且热降解程度低，可制备断裂强度为6.75 cN/dtex、极限氧指数(LOI)可达31%的共聚型阻燃聚酯工业丝，且其阻燃耐久性突出，实现了良好阻燃性能与力学性能共聚型阻燃聚酯工业丝的制备。     

微细化玉米淀粉的晶体结构及分子链行为研究

采用偏光显微镜,X-射线衍射仪,示差扫描量热仪、凝胶过滤色谱以及激光光散射分析技术等测试手段,表征和探讨了超音速气流粉碎微细化处理的玉米淀粉的晶体结构和分子链行为.结果表明,机械力非晶化作用使玉米淀粉分子结构松弛,晶体结构受到破坏,结晶度降低,微晶熔融温度下降.机械应力主要作用于玉米淀粉的支链淀粉,从而导致其支链淀粉级分减少,直链淀粉和中间级分增加,重均分子质量下降,分子链柔顺性增加.     

Study on supramolecular structural changes of ultrasonic treated potato starch granules

The supramolecular structural features of ultrasonic treated potato starch granules in excess water were investigated. Various ultrasonic treatments were used; an ultrasound probe set with different power (60, 105, 155 W) at a frequency of 20 kHz for 30 min. Scanning electron microscopy (SEM) images show that ultrasonic treatment induced notch and groove on starch granule surface. The B-type crystal structure was scarcely affected according to polarized light microscopy (PLM) and X-ray diffraction (XRD) analysis. However, Small-angle X-ray scattering (SAXS) data manifest that fractal structures changed from surface fractal into mass fractal as the ultrasonic power increased, indicating that the compact starch granules swelled to a larger extent and loosed. The repeat cluster thickness was unchanged. The electron density contrast between the crystalline and the amorphous lamella decreased, while the electron density difference between the amorphous lamella and amylose background increased. Moreover, the molecular order in crystalline lamella was reduced. These results demonstrated that ultrasonic treatment affected cluster structure, especially the crystalline region, and amylose background was affected more compared to amylopectin amorphous lamella.     

纤维素酶酶解苇浆纤维微观结构和结晶结构的变化

采用红外光谱(IR)、X射线衍射分析和扫描电镜对在纤维素酶解进程中苇浆纤维素大分子的结构及纤维形态的变化进行了研究.研究结果表明,纤维素酶酶解进程中,纤维素大分子的晶型没有改变,但结晶度呈现周期性变化,微晶尺寸略有降低.在酶解初期,纤维素酶不仅作用于纤维素无定形区,也开始作用在纤维素结晶区表面;在酶解中、后期,纤维素酶对纤维素结晶区和无定形区的作用呈现周期性变化.纤维素酶解过程中纤维表面呈现周期性"剥皮"现象,并且在纤维表面出现孔洞和沟槽,在孔洞处纤维易断裂,导致纤维长度和粗度的降低.     

Supramolecular structure of A- and B-type granules of wheat starch

The supramolecular structure of the A- and B-type granules of wheat starch was compared. Polarized light microscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to study the granular, crystalline, and short-range structures. The A- and B-type granules displayed a typical A-type crystalline structure with the degrees of crystallinity of 31.95% and 29.38% respectively. In addition, the B-type granules had some V-type crystallites. The nanostructure and fractals were characterized by small angle X-ray scattering (SAXS), which showed that the average thickness of the lamellae of the A-type granules was larger, while the B-type granules possessed a higher degree of ordering in the lamellar regions. A second order reflection was found in both A- and B-type granules, which was proposed due to the crystalline lamellae of the semicrystalline lamellae. The A- and B-type granules had mass and surface fractal structures respectively.     

Structural modifications of granular starch upon acylation with short-chain fatty acids

Low (LAMS) and high (HAMS) amylose maize starches acylated with acetic, propionic and butyric acids at three different degrees of substitution (DS) have been structurally characterized. SEM, XRD, SAXS and FT-IR were used to ascertain the effects of the molecular size of the esterified acid, the composition of the base maize starch and the DS on their structural properties. LAMS and HAMS did not differ significantly at the microscopic level. However, substantial differences were found at the nanostructural levels as a function of the esterified fatty acid, highlighting the importance of these length scales for the understanding of the macroscopic functional characteristics. Although the crystal unit cell remained practically unchanged, as deduced from the similar X-ray diffraction patterns, an increase in long-range order was observed with increasing fatty acid chain length. Conversely, shorter acyl chain lengths were related to greater decreases in the electron density difference between the amorphous and crystalline lamellae, suggesting the introduction of defects in the lamellar structure. From the SAXS results, it appears that the longer esterified chains are able to be accommodated within the crystalline lamellar regions so that the nanostructure is affected less by butyrylation than by the addition of acetyl or propionyl groups.     

Influence of the polarity of the water phase on the mesomorphic behaviour and the α-gel stability of a commercial distilled monoglyceride

The lyotropic mesomorphic behaviour of a commercial distilled monoglyceride based on fully hydrogenated palmstearin at a concentration of 25% was studied as a function of temperature. Differential scanning calorimetry and wide angle X-ray diffraction were used to determine the Krafft temperature. Polarized light microscopy and small angle X-ray scattering were used to analyze the lamellar dispersion to an inverted bicontinuous cubic phase transition. The addition of a polar solvent, namely ethanol, propylene glycol and glycerol shifted the lamellar dispersion region to lower temperatures. The composition of the water phase also played an important role in the stability of the α-gel that was obtained by cooling the lamellar dispersion. In fact, the stability of this metastable phase as expressed by the coagel-index determined by differential scanning calorimetry was negatively influenced by decreasing the water phase polarity.     

Structure–property relationship of different types of polyester industrial yarns

Four major types of polyester industrial yarns (1000 Denier) which are used commercially were studied for their key structural parameters. An attempt has been made to establish a relationship between morphology and properties of these yarns. High tenacity (HT) polyester yarn has the highest birefringence, amorphous orientation, and long period but is relatively less crystalline. High shrinkage characteristic of HT polyester yarn can be accounted for its higher amorphous orientation. High modulus low shrinkage (HMLS) polyester yarn has higher crystallinity and crystal size compared to HT yarn. Fraction of tie molecules of these yarns has been calculated and found that low shrinkage (LS) and super low shrinkage (SLS) yarns have lesser tie molecules. These LS and SLS yarns are tailor-made to achieve lower shrinkage and at the same time maintaining a good level of tenacity. This is achieved with lower amorphous orientation in the final drawn yarn structure. Amorphous orientation was found to have stronger influence than any other structural parameter on the key yarn properties like modulus, tenacity, elongation, and shrinkage.     

醇水相湿热处理对玉米淀粉颗粒性质的影响

采用醇水相湿热处理对玉米淀粉进行研究,考察了处理温度范围为70-90 ℃内淀粉颗粒偏光十字,形貌,粒径分布,结晶结构及糊性质等性质变化。随着湿热处理温度升高,发现：淀粉颗粒偏光十字消失增多,最终颗粒破碎;颗粒平均粒径由23.6 μm持续增加至50.4 μm,其中小颗粒（〈10 μm）数目减少,中等颗粒（10-30 μm）和大颗粒（30-100 μm）数目均有不同程度的增加;淀粉颗粒表面出现小孔和凹坑,最终颗粒成团,干燥粉碎之后破碎成片状;淀粉的X射线衍射在衍射角15°,18°和23°处峰强度逐渐降低,但在衍射角20°处峰强度增加。淀粉的Brabender粘度曲线显示,湿热处理后玉米淀粉糊化起始温度由80.5 ℃升高至90.6 ℃,粘度降低,表明玉米淀粉热糊稳定性和冷糊稳定性增强,糊凝沉性降低;测定分析淀粉分子量可知,淀粉颗粒内部分子链发生了断裂、降解。     

超疏水聚酯滤布的性能及其在油水分离中的应用

为改善纳米二氧化硅的分散性,提升其与聚酯滤布的结合力,采用巯丙基三甲氧硅烷对纳米二氧化硅进行表面修饰,并通过浸渍-涂覆的方法将修饰后的二氧化硅负载在聚酯滤布表面,得到超疏水滤布。通过场发射扫描电镜、光电子能谱仪、傅里叶变换红外光谱仪及特征X射线能谱仪等对滤布进行了微观形貌、结构、元素及价态等方面的分析。结果表明:滤布表面均匀负载的低表面能硅树脂及其在滤布表面构建的微纳米多级凸起结构赋予滤布超疏水性,接触角高达156°;该滤布耐溶剂性能优良,在不同有机溶剂中浸泡72 h后,接触角仅下降1°~4°,滤布兼具高强度、超疏水/超亲油的特性。     

Compression creep behaviour of polyester needle-punched nonwoven fabrics

This present study deals with the compression creep behaviour of polyester needle-punched nonwoven fabrics. Polyester fibres of three different cross-sectional shapes (round, circular hollow and trilobal) have been selected for this study. An instrument has been designed and fabricated to measure the compression creep property of needle-punched fabrics. The effect of duration of compression load, fabric weight, fibre cross-sectional shapes and reinforcing material on percentage compression creep has been studied. It has been observed that initially, compression creep decreases rapidly and with increase in time, decrease of percentage creep becomes minimal. After about 8500?min of application of the same compression load, no change in compression creep is noticed. The percentage compression creep decreases with the increase in fabric weight irrespective to fibre cross-sectional shapes of polyester needle-punched nonwoven fabrics. Trilobal cross-sectional fabric shows maximum amount of percentage compression creep at all levels of fabric weight followed by round and hollow cross-sectional polyester samples, respectively. The percentage compression creep is higher in case of fabric samples made without reinforcing material compared to the samples with reinforcing material. Hollow cross-sectional polyester fibre can be successfully used as raw material for the preparation of needle-punched nonwoven fabrics with or without reinforcing material carpet or floor mats. However, normal round cross-sectional polyester fibre only with reinforcing material can be used for the said application. Compression creep values of these selected polyester needle-punched fabric samples are much lesser in comparison with commercial market polypropylene needle-punched carpet samples.