不同相对分子质量壳聚糖絮凝性能

壳聚糖作为天然高分子絮凝剂具有无毒、不存在2次污染、使用方便等优点;但生产和应用成本高,具有一定限制。而相对分子质量是壳聚糖的一个重要分子参数,不同相对分子质量的壳聚糖性质差异很大,研究了不同相对分子质量的壳聚糖对生活污水的絮凝性能,结果表明：高相对分子质量壳聚糖的絮凝效果较好,且随着壳聚糖用量的增加絮凝性能也随之增加,但是5×10^-6后絮凝下降,其在pH值为6.5时絮凝效果最佳。     

超高相对分子质量聚乙烯特性黏数的测试方法

采用毛细管黏度计法测定超高相对分子质量聚乙烯(UHMWPE)的特性黏数([η]),对[η]的准确测定的影响因素进行了探讨。结果表明:以十氢萘为溶剂,使用前进行蒸馏提纯;在配制UHMWPE溶液时,加入质量分数为0.2%的抗氧剂1010,按预溶胀、溶胀、溶解3步骤进行溶解,溶解温度150℃,溶解时间0.5 h,配制UHMWPE溶液浓度为100~600 mg/L;严格控制温度(135±0.2)℃,所测UHMWPE的[η]平行性较好,相对标准偏差为1.08%。     

γ-射线辐照对壳聚糖相对分子质量影响

壳聚糖是地球上蕴藏量最丰富的有机物之一.常用的壳聚糖相对分子质量大,不易溶于水等普通溶剂,使其应用受到极大限制.使用γ-射线(3x1015Bq钴-60装置)辐照壳聚糖,研究了溶液浓度、辐照剂量、辐照气氛、pH值和样品状态等因素在壳聚糖γ-射线辐照过程中对相对分子质量的影响.结果表明壳聚糖辐射降解产物的平均分子量随着溶液浓度增加和辐照剂量增大而降低,而与溶液的pH值无关.水对于壳聚糖辐射裂解有加速效应,溶液态壳聚糖辐照降解比固态辐照可以提高效率约50倍.     

黏度法测定UHMWPE相对分子质量影响因素分析

研究了黏度法测量超高相对分子质量聚乙烯(UHMWPE)的黏均相对分子质量过程中搅拌方式、粒径、清洗和数据处理对测试结果的影响。结果表明,磁力搅拌和摇晃都可以加速溶解;相对分子质量高或粒径大都会导致溶解时间延长,其中粒径的影响更加明显;乌氏黏度计的清洗和维护是保证试验准确的必要条件;相对分子质量较大样品的数据的重复性变差,建议取3组相对较小的数值进行计算。     

超高相对分子质量聚乙烯的相对分子质量及其分布的测试方法

介绍了超高相对分子质量聚乙烯（PE-UHMW）的相对分子质量及分布的测试方法,主要有黏度法、流变法和凝胶渗透色谱法（GPC）。黏度法是目前应用最广泛的一种测试方法,主要采用高温乌氏黏度计,按照聚烯烃稀溶液的黏度测试方法进行,并通过经验公式计算得到PE-UHMW的相对分子质量。流变法是一种有效的测试PE-UHMW相对分子质量及其分布的方法,但目前该方法仍需改进。采用GPC法测试PE-UHMW的相对分子质量及其分布在技术上存在局限性。     

无机聚磷酸盐相对分子质量测定方法

介绍了无机聚磷酸盐水溶液的基本特性和其常用的相对分子质量测定方法,如滴定法、光散射法、黏度法、31P核磁共振法等.阐明了这些方法的基本原理、特点、适用范围及局限性.指出了无机聚磷酸盐水溶液制备过程中应注意溶解方式、温度、酸度等事项.在实验研究结果的基础上,对无机聚磷酸盐相对分子质量测定方法选择提出了建议.     

黏度法测定UHMWPE黏均相对分子质量影响因素分析

研究了黏度法测量超高相对分子质量聚乙烯(UHMWPE)特性黏数过程中恒温浴温度、溶剂、溶解时间对测试结果的影响.结果表明,恒温浴内部测试点附近的温度和温度控制器显示温度之差对最终计算结果影响较小;三氯苯和十氢萘分别作为溶剂所得到的结果较为接近,二者均可作为UHMWPE黏均相对分子质量的测试溶剂;聚合物完全溶解的标准是测试结果平行性好,并且随着时间延长,UHMWPE溶液流出时间不再变化.     

双组分室温硫化硅橡胶相对分子质量测定

对双组分室温硫化硅橡胶相对分子质量进行测定.根据双组分室温硫化硅橡胶粘度测定数据,分别用外推法、一点法和算图法计算其平均相对分子质量.一点法计算简单,但误差较大;外推法误差较小;算图法准确性最高,但耗时长.粘度测定结果的影响因素包括粘度计结构和材料以及温度、外界震动和溶剂纯度等.     

壳聚糖氧化降解性能的研究

对壳聚糖在2％乙酸溶液中的氧化降解行为进行了探讨,着重考察了温度、时间和用量比R(H2O2与糖单元的物质量比)对相对分子质量的影响。同时对氧化降解的动力学规律作了初步研究,结果表明,氧化降解分为两个阶段,在后阶段的降解行为符合无规降解规律。     

低相对分子质量聚乳酸及其与壳聚糖的共混为载体的药物控释研究

以两种低黏均相对分子质量(Mη=3 595和10 306)聚乳酸及其与壳聚糖按5∶1,10∶1,20∶1,40∶1质量比共混为载体,用熔融法制备了吡虫啉控释制剂;用体外实验测定了制剂中吡虫啉的释放动力学;通过测定释放过程中释放介质水的pH,初步考察了基体的降解性能;通过测定释放实验结束时制剂残留质量,考察了基体的溶蚀性能,初步探讨了释放机理。结果表明,低相对分子质量聚乳酸及其与壳聚糖共混材料为载体,可以用于吡虫啉的控制释放,呈现扩散和溶蚀共同控制的缓慢释放,和溶蚀控制的快速释放两阶段释放规律。提高聚乳酸的相对分子质量可以减缓吡虫啉的释放,使释放特征发生从初期的快速释放和后期的缓慢释放,到初期缓慢释放和随后的快速持续释放的转变。降低聚乳酸相对分子质量或在基体中加入壳聚糖,可加大基体的溶蚀,使溶蚀控制的吡虫啉快速释放阶段提前。在Mη=10 306的聚乳酸中加入不同质量比的壳聚糖,可使释放介质水的pH约为中性,在117-336 h内调节快速释放开始时间,在228-445 h内调节释药中值时间。这种聚乳酸/壳聚糖共混载体可望在多功能型种子处理控释制剂上获得应用。     

低聚壳聚糖的复合酶法制备研究

通过对黏均分子量、酶活力、水解率和还原糖浓度的测定,研究了由商业α-淀粉酶、纤维素酶和果胶酶1∶1∶1(m/m/m)组成的复合酶降解壳聚糖的最佳工艺条件,结果表明:复合酶在酶底物比为1∶5(m/m)、pH 5.3、温度56℃的条件下,酶解2 h可得到分子量为1 000～4 000的低聚壳聚糖,且通过傅里叶红外光谱分析酶解后的产物结构无明显变化。     

粘度法测定药用聚乙二醇分子量的不确定度评定

粘度法测定了聚乙二醇的相对分子质量,并对测定结果的不确定度进行了分析和评定。通过对测定过程中的各种不确定度分析,得到了测定结果的不确定度主要由溶液配置过程中的容量瓶体积和移液管体积引入的不确定度组成,其他方面的组成较小,在实际评定中可以忽略。     

Synergistic effects of crosslinking and chitosan molecular weight on the microstructure,molecular mobility,thermal and sorption properties of porous chitosan/gelatin/hyaluronic acid scaffolds

In this study, synergistic effects of crosslinking and chitosan molecular weight on the microstructure, molecular mobility, thermal, and sorption properties of porous chitosan/gelatin/hyaluronic acid hybrid foams are reported. Fourier transform infrared spectroscopy has been utilized to confirm the covalent attachment of hyaluronic acid to gelatin and chitosan, and covalent chemical crosslinking between gelatin and chitosan. Detailed image analysis of scanning electron microscopy images of the porous scaffold hydrids reveal that the pore size of the materials formulated using either low‐ or high‐molecular‐weight chitosan increases significantly upon crosslinking using ethyl(dimethylaminopropyl) carbodiimide/N‐Hydroxysuccinimide. These microstructural changes are even more pronounced for the crosslinked hybrid scaffolds formulated using low‐molecular‐weight chitosan, highlighting a synergistic effect between crosslinking and the use of low‐molecular‐weight chitosan. Results obtained using differential scanning calorimetry demonstrate a significant reduction in molecular mobility reduction in molecular mobility for crosslinked scaffolds formed using high‐molecular‐weight chitosan compared to non‐crosslinked hybrids and crosslinked hybrids formulated using low‐molecular‐weight chitosan. Correspondingly, dynamic vapor sorption evidenced significantly lower water vapor sorption for crosslinked scaffolds formulated using high‐molecular‐weight chitosan. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44772.     

Stabilization of epidermal growth factor on thermal and proteolytic degradation by conjugating with low molecular weight chitosan

Epidermal growth factor (EGF, 5900 Da) has been reported to have the high efficiency of wound repair. However, the half‐life of EGF in the body is too short to exert the biological activity effectively when applied in free forms. Conjugation of the low molecular weight chitosan (LMC) to EGF was carried out to enhance its stability. EGF was conjugated with LMC activated by water‐soluble carbodiimide. The formation of EGF–LMC was quantitatively measured by indirect enzyme‐linked immunosorbent assay (ELISA). In a study of the thermal and the proteolytic stability of free EGF and EGF–LMC, EGF covalently attached to LMC was found to be more stable than free EGF in thermal and proteolytic stabilities. In animal experiments of which free EGF (control), EGF–LMC (test) and LMC (carrier) diluted in viscous carboxymethyl cellulose (CMC) solution (vesicle) were applied to the incisional wounds in rats, the EGF–LMC conjugates are considered to be potent wound healing agent with mitogenicity and wound‐healing property. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5072–5082, 2006     

不同相对分子质量的尼龙6流变性能研究

用毛细管流变仪研究了尼龙 6试样相对分子质量对其流变性能的影响。结果表明 ,在实验范围内试样熔体为假塑性流体。随着相对分子质量的增加 ,非牛顿指数 (n)减小 ;熔体稠度 (K)增大 ;lgη～lg γ直线的斜率和截距均增大 ;粘流活化能降低。且试样的相对分子质量与表观粘度及熔融指数均有较好的对数线性关系。     

Effects of the molecular weight and the degree of deacetylation of chitosan oligosaccharides on antitumor activity

Effects of the degree of deacetylation (DDA) and the molecular mass of chitosan oligosaccharides (CTS-OS), obtained from the enzymatic hydrolysis of high molecular weight chitosan (HMWC), on antitumor activity was explored. The DDA and molecular weights of CTS-OS were determined by matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-TOF MS) analysis. The CTS-OS were found to be a mixture of mainly dimers (18.8%), trimers (24.8%), tetramers (24.9%), pentamers (17.7%), hexamers (7.1%), heptamers (3.3%), and octamers (3.4%). The CTS-OS were further fractionated by gel-filtration chromatography into two major fractions: (1) COS, consisting of glucosamine (GlcN)(n), n = 3-5 with DDA 100%; and (2) HOS, consisting of (GlcN)(5) as the minimum residues and varying number of N-acetylglucosamine (GlcNAc)(n), n = 1-2 with DDA about 87.5% in random order. The cytotoxicities, expressed as the concentration needed for 50% cell death (CC(50)), of CTS-OS, COS, and HOS against PC3 (prostate cancer cell), A549 (lung cancer cell), and HepG2 (hepatoma cell), were determined to be 25 μg·mL(-1), 25 μg·mL(-1), and 50 μg·mL(-1), respectively. The HMWC was approximately 50% less effective than both CTS-OS and COS. These results demonstrate that the molecular weight and DDA of chitosan oligosaccharides are important factors for suppressing cancer cell growth.     

Effect of immobilized neutral protease on the preparation and physicochemical properties of low molecular weight chitosan and chito‐oligomers

Neutral protease was immobilized on glutaraldehyde‐pretreated N‐succinyl chitosan hydrogel beads and the biocatalyst obtained was used for the preparation of low molecular weight chitosan and chito‐oligomers with molecular weight of 1.9–23.5 kDa from commercial chitosan. Factors affecting the chitinolytic hydrolysis were described. The degradation was monitored by gel permeation chromatography. The structure of degraded chitosan was characterized by Fourier transform infrared, X‐ray diffraction and liquid chromatography‐mass spectrometry. Immobilized neutral protease showed optimal depolymerization at pH 5.7 and 50°C. The degree of deacetylation of the hydrolysates did not change compared to that of the initial chitosan. The decrease of molecular weight led to transformation of crystal structure but the chemical structures of residues were not modified. The degree of polymerization of chito‐oligomers was mainly from 3 to 8. The method allows cyclic procedures of immobilized enzyme and N‐succinyl chitosan support utilization, and is suitable for a large‐scale production of the low molecular weight chitosan and chito‐oligomers free of protein admixtures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4185–4193, 2006     

UHMWPE纤维联合生产线自动控制系统介绍

利用富士触摸屏UG30系列程序操作显示器(简称POD)的通讯、控制功能构建一套开放式结构的自动化平台,通过与变频器-同步电机及PID控制器的直接联网,实现了全部电控设备的主控制台集中控制。该控制系统实现了丝束的拉伸速度变频控制,清洗机系统进出液流量及液位控制,清洗机系统与外围液体回收系统物料输送自动化,干燥机风量、风温自动控制等。传动控制采用同步电机与变频的开环控制,高精度变频调速器和永磁同步电机构成系统,无需采用闭环控制,可保证电机转速精度达到0．1％-0．01％。     

Effect of time/temperature treatment parameters on depolymerization of chitosan

Depolymerization of the biopolymer chitosan by an autoclaving process at 121°C and 15 psi was investigated using various treatments. Acetic acid was found to be the most effective solvent in decreasing chitosan viscosity among the six organic acids tested. The rate of viscosity decrease increased with increasing chitosan concentration. The viscosity of 1% chitosan in 1% acetic acid decreased rapidly to 91% of the initial viscosity following the initial 15 min of autoclaving. This decreased gradually to 93% and 94% in 30 and 60 min, respectively, without being adversely affected by the chitosan solution volume. The degree of deacetylation was comparable before and after autoclaving for 60 min. Chitosan at three molecular weights (M_r = 1597, 1110, and 789 kDa) decreased in molecular weight by 46%–51% in the 15‐min treatment, 55%–60% in the 30‐min treatment, and 60%–62% in the 60‐min treatment. The addition of 0.1%–1.0% (v/v) concentrations of hydrogen peroxide to the chitosan solution autoclaved for 15 min decreased viscosity by 94%–98% and molecular weight by 69%–83%. This process is a simple, timesaving, homogeneous depolymerization procedure, and it is possible to prepare partially hydrolyzed chitosan with specified molecular weights by regulating the time of treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1890–1894, 2003     

Encapsulation of salicylic acid in acylated low molecular weight chitosan for sustained release topical application

Acylated low molecular weight chitosan was used to encapsulate salicylic acid (SA) for sustained release in topical delivery. Chitosan nanoparticles were prepared from the depolymerization of commercial chitosan and further acylated with short alkyl chains. The successful acylation of butyryl chitosan [low molecular weight chitosan (LMWC)‐B] were proved by Fourier transform infrared (FTIR) and ¹H‐NMR. Successful encapsulation of SA was observed by the shift of amide I band from 1648 cm^?1 in LMWC‐B to 1641–1633 cm^?1 in SA‐loaded LMWC‐B in FTIR analysis, which further confirmed with the size increment from dynamic light scattering and transmission electron microscopy analyses by comparing its unencapsulated LMWC‐B. SA release from LMWC‐B studied by Franz diffusion experiment followed Korsmeyer–Peppas model where the release component n value (0.502) indicated diffusion and polymer swelling were involved in release mechanism. The slow release study of SA showed the acylated chitosan exhibited sustained release property toward SA. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45273.