明胶接枝改性及应用

<正> 一、引言有关明胶的接枝改性,很多人是感兴趣的。明胶接枝以后,可以提高它的机械物理性能,具有较高的弹性,热稳定性及耐磨性,因此在感光材料及皮革工业中应用它,可以提高涂层的质量。明胶接枝物还可以作为卤化银的沉降剂,沉降卤化银微晶。本文采用明胶与甲基丙烯酸甲酯和甲基丙烯酸(或丙烯酸)混合单体的辐射接枝,研究明胶接枝物作为沉降剂使用的可能性。     

改性明胶的制备

明胶属蛋白质类天然高分子材料，对人体无毒。明胶的化学改性是利用明胶上各种官能团能与低分子量或高分子量物质进行反应的功能，使明胶交联或接枝。Ｆｌｏｒｙ３０年代就已发现可利用链转移的办法将各种乙烯基单体接枝到高聚物上，以改善高聚物的性质。本实验利用乙烯基...     

改性明胶沉降剂研制及应用的发展概况

<正> 目录一、导言二、改性明胶沉降剂的制备 1.试剂类别 2.与明胶接枝的反应条件三、改性明胶沉降剂的物理化学性能 1.取代度 2.电性质(等电点) 3.分子量的分布四、改性明胶沉降剂的照相性质 1.除盐效率 2.回收率(明胶、卤化银) 3.盐的效应 4.对乳剂颗粒生长的影响 5.对感光性能的影响 6.保存性五、改性明胶的沉降机理     

测定照相明胶还原特性的不同方法的比较

<正> 1.引言众所周知,某些杂质如硫代硫酸盐、亚硫酸盐和核酸,在很大程度上影响明胶照相性能。若使用不含这些杂质的惰胶,必要时可定量补加这些物质。但是,即使是这些“惰胶”似平也各不相同,原因之一可能是其还原性质不同。明胶确有还原性,例如,它起溴接受体的作用。据研究,正是某些氨基酸组分,如蛋氨酸、酪氨酸、组氨酸,承担了这种溴接受体的作用。然而在某些明胶中,蛋氨酸部分被氧化,从而导致还原性能的不同。此     

明胶接枝共聚的进展

本文是关于明胶接枝共聚问题近年来进展情况的评述,指出了用乙烯基单体对明胶进行接枝改性的目的和意义。简要介绍了反应介质、原料明胶、单体、引发剂,以及接枝率等有关接枝反应的一般问题。分别讨论了明胶浓度、单体浓度、引发剂浓度、反应温度及时问等变量对接枝反应的影响。介绍了明胶接枝产物的分析鉴定方法。列举了可能的接枝反应机理。此外,还指出了当前在明胶接枝共聚的研究工作中尚未解决和需要进一步研究的问题。     

水解明胶

<正> 近年来,国外水解明胶的发展很受人们重视和欢迎。由于它含有人体成长所必需的某些氨基酸成分,加上它本身所固有的某些物理和化学特性,因而被广泛地应用于食品、化妆品、医药、纤维和涂料等工业中。我国的水解明胶产品仍处于研究试制阶段,在生产上仍是空白。为了使我国制胶工业能够迅速发展,在品种方面能进一步满足社会需要,今将水解明胶的制法、性质和用途作一概略介绍。水解明胶是一种低分子量多肽。是以动物结缔组织中的胶原蛋白为原料,经过水解     

改性酪素——明胶皮革涂饰剂的研究

以食用明胶及酪素为接枝混合母体,与丙烯酸丁酯、甲基丙烯酸甲酯、丙烯腈和苯乙烯等4种混和单体以K_2S_2O_8为引发剂进行接枝共聚,合成改性酪素—明胶皮革涂饰剂,建立了相应的标准及理化指标的检测方法。对所研究的改性酪素—明胶涂饰剂进行了理化指标检验及涂饰应用结果的感观评价。     

明胶文摘

<正>姜黄素-羧甲基化瓜尔胶接枝明胶薄膜在生物医学的潜在应用研究Manna PJ,et al.International Journal of Biological Macromolecules 2015,75:437~446.本研究描述了从天然瓜尔胶(GG)到羧甲基瓜尔胶(CMGG)的合成过程。另外,将制备好的CMGG与明胶接枝形成CMGG接枝明胶,并与姜黄素混合以制备生物材料。所得的生物材料通过1H-NMR,ATR-FTIR,TGA,SEM和XRD手段进行分析以确保羧甲基化和接枝。结果表明,CMGG接枝明胶在生理pH的磷酸     

明胶化学基础讲座——三、明胶溶液的粘度

<正> 明胶溶液的粘度,即明胶溶液流变性质,是明胶溶液重要的物理化学性质。众所周知,在生产明胶时,粘度是一项重要质量控制指标;对胶片的涂布工艺,粘度的控制也是一个重要的参数。因此,了解和掌握明胶溶液的粘胶特性及影响粘度的因素,对生产是很重要的。另外,粘度是液体流动时内摩擦大小的量度,它与溶质分子的大小、形状、溶剂的性质,以及其外界因素有关。所以,通过粘度的研究,可以使我们了解明胶分子在溶液中的大小形态等,加深对明胶溶液物理化学规律的认识。明胶是由多种氨基酸组成的复杂蛋白质大分子,除具有一般高分子溶液的特点外,     

水解明胶与接枝水解明胶的护发作用

<正> 国内某些明胶研究工作者业已发现水解明胶对皮肤有十分显著的保护和治疗作用,实际上,水解明胶和接枝水解明胶对头发也有独特的保护作用。一、水解明胶对头发的化学作用著名的化妆品化学家的实验已指出,胶原水解蛋白质对头发有显著的有益作用,尤其是在头发经过强烈的化妆处理,例如在染发、漂白及烫发之后。头发是氨基酸用肽键连结起来的聚合链,并进一步用S-S键交联。对头发的多数的化学处理都导向双硫键,但头发的强度则决定于肽键。当将水解蛋白质配入各种护发液后,对头发中肽键受到的化学攻击能起保护     

Grafting of polymeric side chains to gelatin

Kinetics of grafting of poly(butyl acrylate) onto gelatin was studied with H₂O₂—ascorbic acid redox systm. Percent grafting, grafting efficiency, R_g, and R_h were determined as a function of time, temperature, initiator, monomer, and backbone concentration. It was found that R_g depends on first power of monomer concentration and 0.5 power to the initiator concentrations. A detailed kinetic scheme is proposed to explain these results.     

Grafting of butyl acrylate onto gelatin in a water-isopropanol medium

Graft copolymerization of butyl acrylate onto gelatin using potassium persulphate initiator was studied in a water-isopropanol medium. The crude graft copolymers were soxhlet extracted with acetone to remove the loosely bound ungrafted homopolymer. The influence of a number of experimental factors such as effect of time, monomer concentration, initiator concentration, backbone concentration and temperature on the graft copolymerization of gelatin were investigated.     

The effects of reaction conditions on the electrical conductivity of PAAG hydrogels

The effects of reaction conditions: concentration of crosslinker, monomer, initiator and gelatin and neutralization degree (ND) of acrylic acid (AA), of a graft radical crosslinking polymerization of AA and gelatin, on the specific electrical conductivity and the primary structural parameters of synthesized poly(acrylic acid)-g-gelatin (PAAG) hydrogels were investigated. It was established that: (a) electrical conductivity of all of the investigated hydrogels is higher than of distilled water; (b) the increasing concentration of crosslinker, monomer and initiator leads to the two linear distinct increases of electrical conductivity with different slopes (c) the increasing ND of AA leads to linear decrease in electrical conductivity and (d) gelatin concentration does not significantly influence the electrical conductivity of hydrogel. An analyses of the primary structural parameters of synthesized PAAG xerogels reveals that: (a) values of molar mass between crosslinks and distance between polymer chains are power form function on crosslink density (ρ_c); (b) the critical value of ρ_c corresponds to the percolation threshold of H⁺/K⁺ ions through the hydrogels network and (c) electrical conductivity of PAAG hydrogels is a power form function on ρ_c. Fractal model of conductivity of hydrogel is suggested and explained.     

Continuous emulsion polymerization of vinyl acetate. I. Operation in a single continuous stirred tank reactor using sodium lauryl sulfate as emulsifier

Continuous emulsion polymerizations of vinyl acetate were carried out at 50 °C in a single continuous stirred‐tank reactor using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator. It was found that (1) the so‐called limit cycles could take place in monomer conversion, the number of polymer particles and the molecular weight of polymers produced under certain operating conditions, (2) the time‐average steady‐state monomer conversion was proportional to the 0.31 power of the emulsifier concentration in the feed, to the 0.50 power of the initiator concentration, to the ?1.0 power of the monomer concentration, and to the 0.90 power of the mean residence time, and (3) the time‐average steady‐state number of polymer particles produced was proportional to the 2.1 power of the emulsifier concentration in the feed, to the ?0.80 power of the initiator concentration, to the 0 power of the monomer concentration, and to the ?0.92 power of mean residence time. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2748–2754, 2002     

Graft copolymerization of methyl methacrylate upon gelatin initiated by benzoyl peroxide in aqueous medium

The graft copolymerization of methyl methacrylate upon gelatin was studied using benzoyl peroxide as an organic initiator in aqueous medium. The grafting reactions were carried out within the 65–90°C temperature range, and the effect of monomer and initiator concentrations on the graft yield were also investigated. The maximum graft yield was obtained at a benzoyl peroxide concentration of 0.20 × 10⁻² mol/L and the optimum temperature was 80°C. Thermogravimetric analysis showed that the thermal stability of gelatin increased as a result of grafting. Further, such changes in the properties of methyl methacrylate‐grafted gelatin as density, moisture regain, and water uptake were also determined. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1547–1556, 1999     

研究丙烯腈与淀粉在微波加热时的接枝共聚反应

通过微波加热,研究了以硝酸铈铵为引发剂,淀粉与丙烯腈的接枝共聚反应,探讨了引发剂浓度、单体浓度、反应时间和微波功率对接枝共聚的影响。     

微波辅助法合成高分子量聚丙烯酰胺

以丙烯酰胺(AM)为单体,水为溶剂,过硫酸铵(APS)和偶氮二异丁基脒盐酸盐(AIBA)为复合引发体系,采用微波辅助法制备聚丙烯酰胺(PAM)。研究了微波辐照功率、辐照时间、单体浓度、引发剂用量对聚丙烯酰胺分子量和单体残留率的影响,采用红外光谱(FT-IR)表征了聚合物产物结构,最后考察了剪切作用对PAM性能的影响。结果表明:采用微波辅助法制备的PAM反应时间短、能耗低、分子量高、单体残留率低;当微波功率为100 W,辐照时间为8 min,单体浓度为25%,引发剂用量为0.05%时产物分子量可达1050×104,并且单体残余量低;PAM的降解随着剪切时间的延长和剪切速度的加快而加快。     

Swelling behavior of gelatin‐g‐poly(butyl acrylate) copolymers

Gelatin‐g‐poly (butyl acrylate) copolymers were prepared with gelatin and butyl acrylate. The effects of various reaction parameters, including the concentration of the monomer, the concentration of the initiator, the concentration of gelatin, the reaction time, and the temperature, on the swelling behavior were studied systematically. In addition, the effect of the intercalation of graft copolymers with montmorillonite on the swelling behavior was investigated. The results indicated that the graft copolymerization and intercalation with montmorillonite could greatly reduce the swelling degree of gelatin. The swelling process of the copolymers followed second‐order kinetics identical to those of the original gelatin. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1033–1037, 2005     

Polymerization of methyl acrylate in the presence of ultrasound and peroxodisulfate

A systematic polymerization kinetic study of methyl acrylate with an added initiator, peroxodisulfate, in the presence of low‐power ultrasound was done. The polymerization experiments were conducted at various concentrations of monomer and initiator at different temperatures (303–323 K). The polymerization was found to proceed without an induction period, and the steady state was attained in a fairly short time. The rate of monomer disappearance showed a second‐order dependence on monomer concentration. The chain lengths of the polymer were calculated, and we found that the chain length increased with increasing monomer concentration and decreased with increasing initiator concentration. The reaction scheme proposed is based on the kinetic studies that indicated linear termination by sulfate‐ion‐radical‐incorporating direct reaction between the monomer and the initiator. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Poly(methyl methacrylate) and polyacrylonitrile dispersions stabilized by gelatin

Methyl methacrylate was polymerized in an aqueous medium in the presence of gelatin using potassium persulfate as initiator. The dispersion mode of polymerization, when the monomer is completely miscible with water, was investigated and compared with an emulsion process, which proceeds at higher monomer concentration. Spherical and relatively uniform polymer particles were formed. Macroscopic precipitation of polymer is prevented by combination of the steric stabilization by grafted gelatin and of repulsive electrostatic interactions from the initiator residues attached to the particle surface. Static and dynamic light scattering have been used to determine the molar mass (molar mass of the whole dispersion particle, M_wD ～ 10⁸-10⁹ g mol^?1) and hydrodynamic radius (R_hD ～ 50-120 nm) of the particles. The number of particles per unit volume does not depend on overall monomer concentration, and it is higher, and therefore the particle size is smaller, than that observed for the soapless emulsion polymerization. The addition of gelatin may be thus used to modify the particle size. Acrylonitrile dispersions were prepared under similar conditions. Unlike methyl methacrylate, this monomer does not swell the polymer particles. While poly(methyl methacrylate) particles are spherical and relatively uniform, the polyacrylonitrile dispersions consist of polydisperse aggregates of tiny polymer particles.