Physical properties of natural and modified cotton cellulose grafted with acrylate monomers

Natural, cyanoethylated, and formaldehyde-crosslinked cotton cellulose has been grafted with methyl, ethyl, and n-butyl acrylate and methyl methacrylate monomers. Various physical properties such as density, moisture regain, birefringence, and mechanical properties were studied. The results indicate that the density and moisture regain of the grafted fibers are less than those of natural cotton. The birefringence of grafted fibers is also less than that of natural cotton. The variation in birefringence with percent graft-on depends on the monomer. Parameters such as orientation factor, helix angle, and refractive power of fibers were calculated from the birefringence data and the results discussed. It was observed that due to grafting of both natural and crosslinked cotton, there is a decrease in tensile strength, increase in elongation at break, and decrease in the initial modulus. Attempts are made to understand these changes in the properties of cotton in terms of the changes occurring in the fine structure of the fiber.     

Studies in chemically modified celluloses. II. Some aspects of physical properties of chemically modified celluloses

The changes in physical properties such as moisture regain, tensile strength, elongation at break, bursting strength, and resistance to abrasion of cellulose modified with different oxidizing agents such as dichromate–sulfuric acid, sodium hypochlorite in presence of leuco vat dyes, and potassium metaperiodate and of the corresponding products obtained as a result of reduction with sodium borohydride and those by oxidation with chlorous acid have been studied. Results are critically discussed in the light of existing knowledge on the changes that occur in the fine structure as well as in the chemical structure of cellulose during the mentioned modifications. It is pointed out that complex changes in physical properties of cotton cellulose brought about by chemical modification could hardly be evaluated and interpreted in terms of one or two physical or chemical parameters.     

辐射接枝改性聚酯纤维吸湿性的研究

经间甲酚浸泡溶胀后,采用二苯甲酮(BP)的丙酮溶液浸泡,紫外光辐射接枝改性聚酯纤维的吸湿性,研究了辐射接枝条件对纤维回潮率的影响。结果表明:当溶胀剂质量分数为40%,溶胀时间为2.0 h,溶胀温度为60℃,BP丙酮溶液的浓度为0.20 mol/L、浸泡时间为1.0 h,紫外光照时间为2 0 h,丙烯酸浓度为0.58 mol/L时,聚酯纤维的回潮率由0.40%提高至3.04%。     

高线密度胶原蛋白/PVA共混纤维的制备及其结构性能

在胶原蛋白与聚乙烯醇(PVA)共混溶液中,改变原液中胶原蛋白和聚乙烯醇的组成,由湿法纺丝得到初生纤维,经热拉伸、热定形、缩醛化反应制得线密度大于25dtex的胶原蛋白/PVA共混纤维。共混纤维横截面呈圆形,纤维内部无孔洞及裂纹,表面光滑,断裂强度和初始模量分别达到4.63cN/dtex和160.2cN/dtex,断裂伸长率为25.4%,结晶度为48.6%,水中软化点和回潮率分别为104℃和13.67%。     

Infrared–deuteration study of regenerated cellulose fibers

This paper describes a study by infrared, deuteration, and other techniques of the fine structure of three regenerated cellulose fibers (Fortisan, a super tire yarn, and a fiber of high wet modulus). The infrared and deuteration measurement provide information on the amount and perfection of the hydrogen-bond ordered material in these celluloses. The three fibers are markedly different in structure: the Fortisan contains about 40% ordered cellulose of a high average degree of perfection, whereas the super tire yarn contains a smaller amount (about 20%) of ordered cellulose of a lower average degree of perfection: the yarn of high wet modulus contains about as much ordered material as the Fortisan, but of an average degree of perfection more similar to that of the super tire yarn. Infrared-dichroism measurements on the fibers are described. The infrared and dichroism studies are discussed in relation to the results of x-ray, moisture regain, acid hydrolysis, and birefringence measurements on the fibers. The infrared-deuteration behavior of acid hydrolysis residues prepared from the three fibers is described; these residues are more highly ordered than the patent fibers, but yield no information of any value in characterizing the structures of the parent fibers.     

凝固浴浓度对离子液体法纤维素纤维结构以及性能的影响

探讨了以离子液体1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂制备的纤维素纤维纺丝工艺条件中凝固浴浓度对纤维结晶结构以及力学性能的影响。实验表明:在相同拉伸比和气隙条件下,凝固浴浓度对再生纤维素纤维的结构以及性能影响较大。随着凝固浴浓度的增加,纤维的结晶度和无定形取向都呈现先增大后减小的趋势,纤维的横向晶粒变小,拉伸强度、初始模量也呈先增大后减小的趋势。     

一步法制备聚乙醇酸纤维的工艺及其性能研究

以聚乙醇酸(PGA)为原料,采用熔融纺丝-拉伸-卷绕一步法工艺制备PGA纤维,研究了工艺路线对纤维结构的影响,重点讨论了拉伸倍数对纤维的结构、力学性能、回弹性能及亲水抗静电性能的影响.结果表明:采用熔融纺丝-拉伸-卷绕一步法工艺,可以较好地实现PGA纤维的热拉伸,纤维与纤维之间不易黏结,纤维结构的稳定性得到改善;随着拉...     

玉米芯纤维的结构性能

玉米芯纤维是以从玉米芯中提炼天然有机物时分离出的纤维素残渣作为原材料,以莱赛尔纤维的纺丝技术小试制造出的一种新型纤维素纤维。对这种新纤维的内部结构和性能进行测试分析,发现其强度高于Lenzing公司的黏胶纤维,略低于国产和进口的莱赛尔纤维,有很好的发展应用前景。小试生产的玉米芯纤维的结晶度高于Lenzing公司的黏胶纤维和3家不同企业生产的莱赛尔纤维,取向度也很高,导致其断裂伸长率和标准回潮率低于上述对比纤维;初始模量高于对比纤维,说明进一步试制需要适当降低牵伸倍数,调整工艺,适当提高纤维的柔韧性。     

充气式微型保鲜冷库纤维保温材料的筛选与评价

纤维材料将是充气式微型保鲜冷库的最佳保温材料之一,其导热系数、回弹力、密度、纤维细度、弯曲度、吸湿率等指标的评价,是库体保温层厚度定量与排列组合的理论基础。研究结果表明:导热系数、回潮率、密度、表面光滑度是影响纤维保温性能的关键因素;涤纶(120 g/m2)的导热系数为0.031 5 W/m·K,回潮率为0.18%,拉伸强度为0.35 MPa,断裂伸长率为127.48%,自熄性好,是一种很好的充气式微型保鲜冷库保温材料。     

丙烯酸接枝改性PET纤维的结构与性能

采用丙烯酸接枝改性聚对苯二甲酸乙二酯(PET)纤维,探讨了接枝率对PET纤维结构、回潮率、染色性能以及力学性能的影响。结果表明:随着接枝率的增加,PET纤维密度变化不大,双折射率略为下降,纤维的吸湿性、抗静电性和染色性能提高,拉伸性能有所下降。当接枝率为10.78%时,PET纤维经0.03 mol/L的Na_2CO_3溶液处理后,其质量比电阻为1.34×10~6Ω·g/cm~2,回潮率为5.05%,纤维拉伸强度为3.31 cN/dtex,上染率达93.8%。     

Extraction and characterization of natural cellulose fibers from common milkweed stems

Natural cellulose fibers with cellulose content, strength, and elongation higher than that of milkweed floss and between that of cotton and linen have been obtained from the stems of common milkweed plants. Although milkweed floss is a unique natural cellulose fiber with low density, the short length and low elongation make milkweed floss unsuitable as a textile fiber. The possibility of using the stems of milkweed plant as a source for natural cellulose fibers was explored in this research. Natural cellulose fibers extracted from milkweed stems have been characterized for their composition, structure, and properties. Fibers obtained from milkweed stems have about 75% cellulose, higher than the cellulose in milkweed floss but lower than that in cotton and linen. Milkweed stem fibers have low % crystallinity when compared with cotton and linen but the strength of the fibers is similar to cotton and elongation is higher than that of linen fibers. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Crosslinked poly(vinyl alcohol) and starch composite films. II. Physicomechanical,thermal properties and swelling studies

Poly(vinyl alcohol) (PVA) was blended with 10, 20, 30, 40, and 50 wt % of starch with and without crosslinking by solution casting process. The solution‐casted films were dried and tested for physicomechanical properties like tensile strength, tensile elongation, tensile modulus, tear and burst strengths, density, and thermal analysis by differential scanning calorimetry (DSC). These PVA/starch films were further characterized for moisture content; solubility resistance in water, 5% acetic acid, 50% ethanol, and sunflower oil; and swelling characteristics in 50% ethanol and sunflower oil. The crosslinked PVA/starch composite films show significant improvement in tensile strength, tensile modulus, tear and burst strengths, and solubility resistance over the uncrosslinked films. Between the crosslinked and uncrosslinked films, the uncrosslinked films have higher tensile elongation, moisture content, moisture absorption, and swelling over the crosslinked films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 909–916, 2007     

A comparison of the dielectric method with density,moisture regain,and x-ray diffraction methods of determining fine structure in cellulosic materials

A comparison between the dielectric method and density, moisture regain, and x-ray diffraction methods of estimating crystallinity in cellulosic materials is presented. The merits of the dielectric method compared to the other methods are discussed. Although the permittivities of completely crystalline and completely noncrystalline celluloses are not directly measureable, the use of extrapolated values for completely crystalline and completely noncrystalline celluloses make it possible to assign a percentage crystallinity to a given material from a single permittivity measurement. Capacitance measurements are very sensitive, accurate, and rapid. Therefore, the dielectric method is capable of following small and rapid changes in crystalline content arising from mechanical, chemical, or thermal treatments. In such a study, permittivities of completely crystalline and completely noncrystalline celluloses are not required. Since the relationship between permittivity and crystallinity is linear, it appears reasonable to continue to represent the fine structure of a cellulosic material by a simple model of a mixture or two hyprothetical components: “crystalline” and “noncrystalline” cellulose and to retain the concept of “percentage crystallinity” in its present form.     

凝固浴温度对Ionicell纤维结构及性能的影响

以离子液体1-丁基-3-甲基咪唑氯盐([BMIM]Cl)为溶剂,水为凝固浴,α-纤维素质量分数95.5%的棉浆为原料,通过干湿法纺丝制备再生纤维素(Ionicell)纤维。探讨了凝固浴温度对纤维结晶结构以及力学性能的影响。结果表明:在其他相同条件下,随着凝固浴温度的升高,纤维的结晶度、双折射和非晶区取向都呈现先增大后减小的趋势,纤维的断裂强度、初始摸量也呈先增大后减小的趋势,当凝固浴温度为20℃时纤维的力学性能最佳,断裂强度为2.98 cN/dtex,断裂伸长率为3.5%,初始模量为59.7 cN/dtex。     

Improvement of hydrophilicity of polypropylene by liquid-phase mutual irradiation of acrylics

N-butanol was found to promote the inclusion of methyl acrylate and methyl methacrylate in polypropylene, but did not affect the uptake of acrylic acid in the polymer. Polymerization of the monomers was, however, not significantly affected by the use of this swelling agent. The monomer exchange process followed by a liquid phase mutual irradiation has proved to be very effective in enhancing the polymerization of all three monomers on polypropylene. Optimum radiation doses for effective polymerization of the monomers were found to be around 3.2 Mrad for methyl acrylate and around 4.8 Mrad for methyl methacrylate and acrylic acid. Surface wettability of the film and moisture regain of the fiber were tremendously improved with all monomers regardless of the swelling agent and temperatures. Also, a low radiation dose of 1.6 Mrad was as effective as the higher doses. Methyl acrylate and methyl methacrylate modified fibers showed no marked changes in strength and elongation, but did result in a harsher hand. Acrylic acid modified fibers increased greatly in elongation, decreased to a greater extent in strength, and softened in hand.     

The strength of particulate polymer composite: A new insight on crystallinity and structural morphology

We have demonstrated the significant impact of high density polyethylene (HDPE) crystallinity and structural morphology on the tensile strength of 60/40 NR/HDPE polymer blend composites. Introducing nanoscale Boron Carbide (B4C-type compounds) fillers noticeably changed the crystallinity and morphology of HDPE, leading to the formation of fine spherulites. Conversely, microscale fillers mainly impacted the crystallinity while preserving a coarse architecture. Although both composites experienced a reduction in crystallinity, the nanocomposites outperformed microcomposites and even the pristine polymer blend in terms of strength, implying the effect of a fine structure. The nanocomposite with a filler loading of 2 wt% exhibited the highest strength. This investigation provides novel insights into the interplay between crystallinity, HDPE structure, and the size of fillers, which heavily influence the strength of polymer blend composites.     

Sorption behavior and crystallinity of jute fiber at higher alkali treatments

Moisture regain of jute fiber was studied at different alkali concentrations and temperatures. It was found that the moisture regain increased up to 4.5N alkali treatment and then leveled off. Variation in swelling temperature had no significant effect on moisture regain. Amorphous fraction calculated from Valentine's equation using sorption ratio was compared with infrared crystallinity. The accessibility was increased with decreasing crystallinity in alkali-treated jute fiber, where as in cyanoethylated jute fiber it increased with increasing the degree of cyanoethylation.     

磁性纤维及其纱线的基本性能

通过对磁性纤维的微观形态结构、单丝力学性能及其混纺纱的断裂强力、回潮率和含水率、耐热性和耐酸碱性等性能的测试发现:磁性纤维表面分布着不规则的磁粉微粒;磁性纤维的断裂伸长率较大;磁性纤维湿纺纱的单纱断裂强力接近300 cN,其延伸性较好,回潮率和含水率均较低,耐干热性良好,耐湿热性较差,耐酸不耐碱,尤其不耐强碱。     

The effect of denim color fading ozonation on yarns

Denim color fading ozonation is dissimilar from other ozone applications as it is employed with distinctive parameters and on special products. In this study, yarns of cotton, lyocell and PET treated by denim color fading ozonation were investigated in terms of the effects of time, pH and water content on their physical properties, which included chemical and crystalline structures, surface microstructure, yarns strength and elongation. It is found that, the cellulose in cotton and lyocell yarns has a loss of strength and elongation, while only slight impacts on their crystalline structures are observed. An aggregation and compact crystalline structure of PET prevents it from the decomposition of ozone, whose prevention may also benefit from its poor ability of moisture regain. As a result, synthetic materials, such as PET is recommended more than cellulose fibers to be used in ozone fading process. Meanwhile, such process should neither be employed on cotton, lyocell and other cellulose yarns at pH < 7 nor without paying attention to select a proper water content.     

Structural changes in Tencel by enzymatic hydrolysis

The NaOH‐, fibrillation‐, and cellulase‐ treated Tencel fabrics were characterized by weight loss, tensile strength, scanning electron microscopy (SEM) analysis, X‐ray diffraction analysis, measurements of moisture regain and dye adsorption (K/S value), degree of polymerization (DP), and copper number. Weight loss increased and tensile strength decreased with increase in cellulase concentration and treatment time. At a similar weight loss, tensile strength retentions of the NaOH‐pretreated samples were better than those of the NaOH‐nontreated samples because of more uniform enzymatic hydrolysis. SEM photographs showed more surface peeling and interfibrillar splitting as enzymatic hydrolysis progressed. Crystalline structure and degree of crystallinity were not much changed by cellulase treatment. As enzymatic hydrolysis progressed, moisture regain and K/S value increased slightly due to increase of specific surface area by fibrils. DP initially decreased as enzymatic hydrolysis progressed and then leveled off. Copper number increased largely at an initial stage of degradation and then decreased gradually. The NaOH‐pretreated samples showed higher degree of crystallinity, DP, moisture regain, and K/S value, but lower copper number than the NaOH‐nontreated ones. These results were attributed to extraction of short chain molecules in the amorphous region during NaOH pretreatment and change of amorphous region into the open‐up structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1644–1651, 2000