国内PVA薄膜材料改性研究进展

聚乙烯醇(PVA)是一种性能优异、用途广泛的薄膜材料,在水溶性及可降解性等方面具有独特优点。文章对PVA的优点、特性作了简要介绍。PVA分子链上含有大量羟基,亲水性较高,在湿度较大的情况下,其阻隔性会急剧下降;PVA熔融温度和分解温度十分相近,给热塑加工带来了困难;PVA是一种可完全降解的高分子聚合物,但其薄膜生物降解周期较长;PVA用作制备亲水膜的材料,但PVA膜纯水渗透量高,其在湿态的稳定性和力学性能不佳。因此,需要对PVA进行不同的改性才能使其达到优良的性能。从PVA的耐水性和水溶性改性、热塑性加工的改性、生物降解性的改性和PVA膜渗透和稳定性改性等4方面对PVA薄膜用材料改性研究方面的进展进行了综述。     

臭氧氧化后麦草碱木质素磺化反应性能的研究

首次对O3/H2O2氧化降解木质素产物进行改性研究,测定了不同氧化反应条件下的碱木质素磺化改性后的物化性能.在O3用量5%、温度20℃、pH值11.68、H2O2的用量2.5%的氧化反应后的氧化木质素,经高温磺化后,磺酸基含量最大;此时,木质素产品的表面活性也较好;在H2O2用量为10%、pH值7.08、温度20℃、O3用量5%的O3/H2O2氧化反应条件下,氧化木质素经过高温磺化后,分散性能大大改善.     

尿素/聚乙烯醇胶粘剂合成工艺条件对性能的影响

以尿素为改性剂,对聚乙烯醇(PVA)进行改性。研究了PVA胶水浓度、反应方式、反应温度及尿素的用量等工艺条件,对改性聚乙烯醇胶粘剂性能的影响进行了讨论。     

水溶性高分子纺织浆料的生物降解功能

通过对PVA、聚丙烯酸类浆料及浆料助剂生物降解性能的论述表明,原淀粉和聚丙烯酰胺这两类浆料的生物降解性能较好,而PVA是最难进行生物降解的,其它浆料对生态环境均有一定的污染。浆料助剂多数为表面活性剂,疏水的碳链越长越难生物降解,直链结构较支链结构的生化降解性相对较好。为解决PVA难以降解的问题,目前已开发出新一代的生物分解酶,可使PVA废液快速生物降解。     

丙三醇缩水甘油醚改性胶原纤维支架材料的性能研究

用正交试验优化了丙三醇缩水甘油醚(GPE)改性胶原纤维支架材料(CFSM)的试验条件,对GPE改性支架材料(GPE-CFSM)的理化性能和生物降解性能进行了表征。结果表明:反应条件对改性效果的影响程度为:温度>pH值>时间>用量。红外分析结果显示GPE与胶原纤维发生了开环反应,且GPE-CFSM保持了胶原的三股螺旋结构。GPE-CFSM的孔径在30~150μm,孔隙率为93.16%,其热变性温度达到104.8℃,吸水倍率与保水倍率分别达到26.73g/g和8.19g/g,亲水性能良好;GPE-CFSM的抗氧化降解性和抗溶菌酶降解性较CFSM提高80%。     

醋酸酯淀粉/聚乙烯醇杂化膜的制备和性质

对玉米原淀粉(ST)改性,制备低取代度醋酸酯淀粉(SA),与聚乙烯醇(PVA)共混,添加纳米二氧化硅改性,经增塑后制备可降解的SA/PVA杂化膜.用红外光谱、扫描电镜对SA/PVA杂化膜进行了结构表征,结果表明SA/PVA杂化膜形成了空间网络结构,相容性较好,膜的致密性提高.电子拉力试验和水溶性试验表明该膜力学性能、耐水性能提高.土埋实验表明该杂化膜具有很好的生物降解性.     

疏水阳离子改性聚乙烯醇施胶剂的制备及在彩色喷墨打印纸中的应用

以(3-甲基丙烯酰胺丙基)十二烷基二甲基氯化铵为改性单体,采用共聚方式合成了疏水阳离子改性聚乙烯醇施胶剂,分别用红外光谱、差示扫描量热仪、拉力仪和光学显微镜对合成的疏水阳离子改性PVA的结构、热性能、力学性能以及膜对油墨的吸收性能进行了表征和测定。结果表明,合成的疏水阳离子改性PVA具有良好的力学性能、结晶性能和油墨固着性能。将合成的疏水阳离子改性PVA用于彩色喷墨打印纸表面施胶,并测试了其彩喷打印性能,结果显示疏水阳离子改性PVA能明显增加图像色密度和抗水性,提高图片的打印效果。     

马铃薯氧化羟丙基淀粉的制备及其性能研究

以马铃薯淀粉为原料,环氧丙烷为醚化剂,H2O2为氧化剂,采用先羟丙基醚化后氧化工艺制备了氧化羟丙基淀粉。首先研究了环氧丙烷用量、氢氧化钠用量、反应时间、反应温度对羟丙基醚化反应的影响,应用单因素和正交试验确定了羟丙基醚化反应的最佳工艺条件。在此基础上,对羟丙基淀粉进行氧化改性,研究氧化剂用量对产品羧基含量的影响。探讨了羟丙基和氧化改性对淀粉在颗粒结构、白度、糊化温度、峰值黏度、透明度、冻融稳定性的影响。结果表明:(1)影响羟丙基含量的因素依次为:环氧丙烷用量、反应温度、NaOH用量、反应时间,制备羟丙基淀粉的最优条件为:环氧丙烷18%、反应时间22 h、氢氧化钠1%、反应温度45℃,淀粉的羟丙基含量为5.77%;(2)随着H_2O_2用量的增加,氧化羟丙基淀粉的羧基含量升高;(3)羟丙基改性降低了淀粉的糊化温度,提高了冻融稳定性;氧化改性降低了淀粉的黏度,增加了淀粉的透明度。氧化羟丙基淀粉具有黏度低、透明度好、抗老化性能强等优点。     

试论聚乙烯醇浆料的环保性能(上)

为了探讨聚乙烯醇浆料的环保性能,介绍了环保型纺织浆料的判别原则,分析了PVA浆料的毒性、生物降解性和对环境的影响,阐述了PVA浆料的生物降解机理和PVA降解酶难以商业化的原因.指出,PVA浆料的生物降解性较差,可以通过对PVA降解菌进行驯化这一途径,提高PVA的生物降解性.     

试论聚乙烯醇浆料的环保性能(下)

为了探讨聚乙烯醇浆料的环保性能,介绍了环保型纺织浆料的判别原则,分析了PVA浆料的毒性、生物降解性和对环境的影响,阐述了PVA浆料的生物降解机理和PVA降解酶难以商业化的原因.指出:PVA浆料的生物降解性较差,可以通过对PVA降解菌进行驯化这一途径,提高PVA的生物降解性.     

Analytical Methods for Chitosan

SUMMARY

Biopolymer chitosan is a prospective textile auxiliary agent prepared from chitin or from bioprocesses waste. Chitosan has a lot of important characteristicsespecially high sorption of basic ions and biodegradability. In this study we tested chitosan using the following analytical methodsviscosimetry, spectrophotometry (IR, VIS, UV), ninhydrin reaction and sorption methods. We discussed an influence of molecular weight and degree of chemical modification as well.     

Development of moisture‐absorbing and antioxidant active packaging film based on poly(vinyl alcohol) incorporated with green tea extract and its effect on the quality of dried eel

Active packaging film with functions of moisture‐absorbing and antioxidant activity was developed based on poly(vinyl alcohol) (PVA) incorporated with green tea extract (GTE). The effects of GTE concentrations of 0, 0.5, 1, 1.5, and 2% on the physical, structural, and antioxidant properties of PVA films were investigated. The PVA film containing 2% GTE had lower moisture absorbing efficiency relatively and better antioxidant activity through DPPH radical‐scavenging ability experiment. A packaging system of GTE‐incorporated PVA films was applied to package dried eel and quality of dried eel was evaluated during storage. The result showed that dried eel packed with GTE‐incorporated PVA films showed lower weight change, peroxide value and TBARS value during storage than that packed without PVA films or with PVA films but no GTE. The PVA film containing 2% GTE showed the best quality protective effectiveness to prevent the dried eel from absorbing moisture and oxidizing of lipid.

Practical applications

Poly(vinyl alcohol) (PVA) is a synthetic polymer that is widely used in packaging applications because of its excellent film forming, biodegradability, good mechanical, and gas barrier properties. The present study evidenced that the PVA films incorporated with GTE showed good quality protective effectiveness to prevent the dried eel packed with these films from absorbing moisture and oxidizing of lipid. This active packaging film could be used as inner layer or intermediate layer in the composite packaging film system to improve the storage quality of moisture‐sensitive and high‐fat food. Based on this concept, the moisture‐absorbing agents and antioxidant can be incorporated into the packaging structures to develop an active multifunctional food packaging material potentially to remove or reduce moisture inside the food packaging system instead of desiccants and preservative added in the food.     

退浆废水中自由基引发的聚乙烯醇交联沉淀研究

针对纺织印染工业退浆废水中含聚合度高且化学稳定性强的聚乙烯醇(PVA),是纺织工业水污染治理难点的现状,利用过硫酸盐能够引发自由基交联且氧化性强的优势,结合退浆废水高温排放的特点,使用热活化过硫酸盐体系通过自由基交联快速将PVA从废水中沉淀分离。考察了过硫酸盐投加量、反应时间、反应温度及p H值对PVA去除的影响。并利用电子顺磁共振谱、傅里叶变换红外光谱、X射线光电子能谱等对交联沉淀物进行表征分析。结果表明:在过硫酸盐投加量为10 g/L、废水温度为70℃时,处理30 min后PVA即可有效交联沉淀,化学需氧量(COD)和PVA去除率分别可达95.1%和95.6%;过硫酸钾热活化主要产生硫酸根自由基和羟基自由基,PVA被自由基夺氢产生碳自由基,碳自由基相互结合可高效交联PVA并快速沉淀。     

咸味香精中美拉德反应产物的抗氧化性研究

利用膜分离手段从肉味香基中分离得到不同分子量范围的美拉德反应产物(MRPs),考察咸味香精中的肉味香基以及不同分子量的MRPs对卵磷脂脂质体的抗氧化效果。结果表明,肉味香基对脂质体过氧化有抑制能力,其抗氧化能力随反应物浓度的增加而增强。高分子量MRPs的抗氧化能力最强,其次为中分子量MRPs,小分子量MRPs抗氧化能力最弱,并且MRPs的抗氧化能力与其褐色程度成正比。     

Factors in Various Fractions of Meat Homogenates That Affect the Oxidative Stability of Raw Chicken Breast and Beef Loin

ABSTRACT:  The fractions of meat homogenates were analyzed to find the factors that determine the susceptibility of raw chicken breast and beef loin to lipid oxidation. The fractions used in this study were meat homogenate, precipitate, and supernatant of homogenate after centrifugation, and high and low molecular weight fractions from the supernatant. Chicken breast showed greater oxidative stability than beef loin during 10-d storage ( P < 0.05). All fractions from chicken breast showed lower amounts of free ionic iron and myoglobin and higher total antioxidant capacity (TAC) than those from beef loin during storage. The TAC level of chicken breast maintained during storage. This suggested that the oxidative stability of chicken breast was ascribed to high, stable total antioxidant capacity with low level of catalysts for lipid oxidation. The water-soluble high molecular weight fraction, which contained myoglobin, was responsible for the high lipoxygenase-like activity and lipid oxidation potential (LOP) in beef loin. TAC in all fractions from beef loin decreased during storage. This suggested that high myoglobin content in beef loin caused the imbalance between pro- and antioxidant factors leading to the high susceptibility of beef loin to lipid oxidation. Myoglobin served a major source of catalysts, ferrylmyoglobin, hematin, and/or free ionic iron, for lipid oxidation.     

Antioxidant activity of yoghurt peptides: Part 1-in vitro assays and evaluation in ω-3 enriched milk

The aim of the present study was to investigate important factors contributing to the high oxidative stability of fish-oil-enriched yoghurt, with particular emphasis on the possible antioxidative effects of peptides released during yoghurt fermentation. Yoghurt samples were stripped from sugars and lactic acid and subsequently fractionated by ultrafiltration using membranes with cut off sizes of 30 kDa, 10 kDa and 3 kDa. The fractions were tested for antioxidant activity by investigating the inhibition of oxidation in liposome model system, 1,1-diphenyl-2-picrylhydrazyl radical-scavenging activity, iron-chelating activity, and reducing power. The lower molecular weight fractions were found to be more effective antioxidants than higher molecular weight fractions. The lower molecular fractions were further tested as antioxidants in fish-oil-enriched milk. On the basis of peroxide value, volatiles, tocopherol and sensory characteristics, the lower molecular weight fractions 3–10 kDa and <3 kDa showed protection against oxidation of fish oil to the same extent as caseinophosphopeptides. The oxygen content of the yoghurt was also found to be lower than that of milk. Thus our findings suggests that the higher oxidative stability of yoghurt might be due to antioxidant peptides released during the fermentation of milk by lactic acid bacteria and/or by the lower oxygen content of yoghurt, which subsequently reduces the oxidative stress of fish oil incorporated in the yoghurt. The results show that antioxidant peptides may be used as an ingredient in foods enriched with fish oils to increase their oxidative stability.     

聚乙烯醇缩醛产品的生物降解性

利用从污水、污泥中分离得到的聚乙烯醇(PVA)降解菌,采用吸光光度分析法,考察了甲醛和戊二醛改性对PVA生物降解性的影响。结果表明,PVA缩醛化产物的降解性均明显低于未改性PVA的降解性,并随着缩醛度或交联度的增加而下降。降解前后的FT-IR分析表明,在降解过程中缩醛产物的主链发生了断裂。     

扇贝性腺多糖提取物的抗氧化及免疫调节活性

通过酶解法制备扇贝性腺多糖提取物(SGP),研究其抗体外氧化及免疫调节活性。采用1,1-二苯基-2-三硝基苯肼DPPH体系反应、Fenton反应和还原反应测定SGP的抗氧化活性;3-(4,5-二甲基噻唑-2)-2,5-二苯基四氮唑溴盐(MTT)法测定SGP 对活性氧叔丁基脂氢过氧化物(tBOOH)致细胞氧化损伤及淋巴细胞增殖活性的调节作用;分光光度法测定SGP 对补体活性的影响。结果表明：SGP具有DPPH自由基清除能力(IC50=9.92mg/mL)和羟自由基清除能力(IC50=7.31mg/mL)及还原能力(AC20=7.74mg/mL);0.2μg/mL的SGP可明显改善tBOOH致RAW264.7细胞的氧化损伤作用,还可显著提高脾淋巴细胞的增殖活性及补体经典途径活性。