Characterization of cross-links introduced in gelatin

A method for the determination of the effectiveness of gelatin hardeners was proposed. Formaldehyde (FA) and 1,3-bis (vinylsulfonyl)-2-propanol (BVSP) were used as cross-linking agents for the hardening of gelatin. The cross-linked gelatin showed a typical rubber elasticity in a swollen state with a mixed solution composed of concentrated aqueous LiBr and diethylene glycol monoalkyl ether. The energy components to total retractive forces were below 0.3. The amount of intermolecular cross-links was estimated by applying an usual rubber elasticity theory for the swollen samples. The number of cross-linking sites was also determined by the amino acid analysis of BVSP cross-linked gelatin. The cross-linking efficiency for the reaction of BVSP occurring in a casting film with less swelling conditions was about four times higher than in a swollen gel. Approximately 92% or more of BVSP used was reacted with the free amino groups of lysine and arginine residues. There was a significant difference between the reactivities of these amino groups. The amino groups of lysine residues were more reactive than those of arginine in a gel state; the reactivities, however, reversed in a thin layer of wet film. The effectiveness of FA was extremely low. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1879–1892, 1997     

Electrospinning of heated gelatin‐sodium alginate‐water solutions

Most polymers that are electrospun are dissolved in a solvent and are spun at ambient temperature. Gelatin, a natural polymer, has excellent potential in medical applications as a biodegradable polymer, especially when combined with sodium alginate. Unfortunately, gelatin/water or gelatin/sodium alginate/water solutions cannot be electrospun at ambient temperature without the incorporation of substances that are considered potentially toxic to the human body, such as acetic acid. In this study, gelatin/water solutions with and without sodium alginate were successfully electrospun without the use of additional solvents by using heated water solutions. The effect of electrospinning parameters such as solution concentration and applied voltage on the nanofiber morphology of these solutions was studied. These nanofibers from heated gelatin/water solutions exhibited good morphology with an average size of 291 ± 67 nm at 18% concentration to 414 ± 52 nm at 20% concentration. Similar sizes were observed when sodium alginate was incorporated into the gelatin/water solutions, although the relationship was dependent upon the amount of sodium alginate in the solution as well as the total concentration. Typically, these nanofibers containing sodium alginate were produced at a lower gelatin concentration compared with the gelatin/water nanofibers because of the increase of viscosity and conductivity of the solutions due to the addition of the highly viscous and conductivity sodium alginate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Interpenetrating polymer networks based on poly(acrylic acid) and gelatin. I: Swelling and thermal behavior

This article describes the synthesis of full and semi-interpenetrating polymer networks (IPNs) based on poly(acrylic acid) and gelatin as polymers 1 and 2, which were crosslinked sequentially using N,N′-methylene bisacrylamide (B_Am) and glutaraldehyde, respectively. Various samples were prepared by taking varying amounts of acrylic acid and gelatin in the initial feed. Sequential IPNs were prepared by first polymerizing and crosslinking acrylic acid in the presence of gelatin using redox initiators (ammonium persulphate and sodium metabisulphite) and B_Am as a crosslinking agent. Gelatin present in the firm gels was then crosslinked using 4% glutaraldehyde. Characterization of these gels was done by measuring their swelling behavior as a function of pH, temperature, and time. Percent swelling increased with increasing amounts of acrylic acid. The swelling ratio was also determined in the pH range of 1 to 12. Acid/alkali or buffers were used for maintaining pH. A significant increase in the percent swelling was observed when pH of distilled water was above 10. On the other hand, in the case of buffer, the swelling ratio increased with increasing the pH, and a maxima was observed at pH 8.4. A further increase in pH resulted in a decrease in the swelling ratio. Thermal and morphological characterization was done using thermogravimetric analyzer and scanning electron microscopy, respectively. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 217–227, 2001     

Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk‐ or Linen‐Reinforced Gelatin Laminates, 2

Biodegradable laminates based on gelatin and on gelatin/starch blend reinforced with fabrics (silk or linen) were prepared by melt pressing. Due to crosslinking during the thermal treatment and in some cases, to additional crosslinking with methylenedi(p‐phenyl) diisocyanate, the fresh and artificially aged samples demonstrated improved mechanical properties, as reported previously. In Part 1 of this study on the environmental behavior of these new laminated composites, the simple dissolution in a buffer solution or water of fresh and artificially aged samples was considered. During this treatment soluble, i.e., uncrosslinked molecules were removed leaving a product resulting from addition reactions and consequent crosslinking. These processes take place during the melt pressing at 180 °C and cause a decreased solubility of gelatin. The present Part 2 deals with the enzymatic treatment of the same samples. We have implicitly shown that the gelatin moiety of the laminates undergoes proteolysis and that this process depends on the laminate composition. At the end of the treatment the enzymatic buffer solution contains only peptides and virtually no high‐molecular gelatin. The degrees of degradation vs. time dependencies differ for water and enzymatic treatment of the samples, indicating different processes in either treatment. The time‐course curves of the enzymatic treatment of different laminates and the kinetic parameters derived therefrom were analyzed. Thereby the effect of many factors on the accessibility of the gelatin moiety to proteolysis was shown. These factors are: temperature treatment, artificial ageing, the nature of the reinforcing fabrics, the “additional” crosslinking with methylenedi(p‐phenyl) diisocyanate, etc. The gelatin‐linen laminate is the most sensitive to crosslinking. There is a tendency that the crosslinking smears the differences in the time‐course of the absorption behavior curves of the different samples.

Degree of degradation, β′, (related to only the gelatin) vs. time, t, for laminates: (a) uncrosslinked gelatin‐linen; (b) crosslinked gelatin‐linen; (c) uncrosslinked gelatin‐silk; (d) crosslinked gelatin‐silk.     

活性染料染色用高浓液体有机固色剂HG的开发和应用

该文介绍了一种自主研发的高浓液体有机固着剂HG,它适用于各种类型的活性染料的染色,也适用于小浴比染色新工艺。对各种结构的活性染料能得到较高的给色量和良好的重现性。它在活性染料染色时用作固色剂,其用量仅为纯碱的1／8～1／10,加碱时间缩短为20～30min,匀染效果佳,可大幅降低染色疵病率。同时,由于用量少,染色后的织物易于洗涤,可以减少水洗道数,省去酸洗,节约了大量的水和汽及工时,用水量仅为纯碱工艺的1／2,蒸汽用量仅是纯碱工艺的1／3,减少了污水和污水中碱剂含量。它和已进入市场的代碱剂有所不同,它是高浓液体的、有机的,它的分子结构中疏抽№基团碳链较短,含有一定的水溶性基团和亲水基团,在缓冲溶液体系中起着助溶、渗透、分散和缓染及移染作用。     

Dissolution and Enzymatic Degradation Studies Before and After Artificial Ageing of Silk‐ or Linen‐Reinforced Gelatin Laminates, 1

In an attempt to overcome the poor mechanical properties of native, i.e., untreated gelatin, laminates based on gelatin and gelatin/starch blend reinforced with fabrics (linen or silk) were prepared by melt pressing. The mechanical properties of fresh and artificially aged samples were reported previously. In the present series of two consecutive papers we present data concerning the dissolution and biodegradation of these laminates. A two‐step procedure for treatment of the laminates was used. The first step is treatment with an aqueous buffer solution, the second with a buffered solution of the enzyme subtilisin. The time‐course of the absorbance at 280 nm of the “washing” solutions was followed. A number of kinetic characteristics was determined and discussed with respect to laminate composition and their treatments. In the present Part 1 about the environmental behavior of these new biodegradable materials, the non‐enzymatic solubilization in water and buffer solution (i.e., simple dissolution) of fresh and artificially aged samples is described. The dissolution process was followed spectrophotometrically as well as by the weight losses. It was found that gelatin‐based silk‐ or linen‐reinforced laminates were subject to dissolution, similarly to the gelatin and gelatin‐based materials studied in previous works. In addition, it was established that the thermal treatment of the laminates during their melt pressing leads to postcondensation reactions and crosslinking of the gelatin macromolecules. Similar reactions occur between the matrix and the reinforcing element silk, thus improving their mutual adhesion. Decreased gelatin dissolution ability was observed after the thermal treatment, in the presence of reinforced fabrics and upon “additional” crosslinking with methylenedi(p‐phenyl) diisocyanate. The untreated gelatin is the only one that dissolves completely in water. The artificially aged samples tend to dissolve better than the respective fresh samples due to degradation processes during aging.

     

Preparation of Mineralized Electrospun Fibers as a Biomimetic Nanocomposite

Mineralization of gelatin electrospun nano and micro fiber was investigated in order to prepare a biomimetic bone nanocomposite. For this aim, at first, calcium containing gelatin nanofibers were electrospun by a novel ethanol/water/salt solution. Fibers with mean diameters varying from 300 to 3000 nm were acquired. Then, fiber mats were exposed to phosphate ions by soaking them in phosphate solution or laminating them between phosphate containing gelatin films. SEM micrographs demonstrated the presence of nano to micro sized minerals on gelatin fibers. FTIR and XRD results illustrated that the calcium phosphates in all samples are combinations of brushite and hydroxyapatite.     

Interaction of functional groups of gelatin and montmorillonite in nanocomposite

As an amphoteric polyelectrolyte, gelatin could intercalate into the galleries of montmorillonite (MMT). In this paper, sodium laurate/MMT composites and sodium laurate/dehydroxylated MMT composites were introduced as low molecular simulation to investigate the interaction functional groups of gelatin and MMT. The composites were characterized by X‐ray diffraction (XRD), Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA) and ¹³C nuclear magnetic resonance (¹³C NMR). Furthermore, the effect of interaction between gelatin and MMT on the mechanical properties of the composites was investigated. The results indicated that ? COO^?, not ? COOH, in gelatin chains could interact strongly with the MMT sheets. The reactive sites on MMT were hydroxyl groups, which could interact with ? COO^? in gelatin chains by forming hydrogen bonds. The gelatin/MMT composites prepared in alkalic media have better mechanical properties due to stronger interaction. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1556–1561, 2006     

Effect of Pretreatments and Drying Methods on the Properties and Fishy Odor/Flavor of Gelatin from Seabass (Lates calcarifer) skin

Effects of different pretreatments of seabass skin and various drying methods on properties and fishy odor/flavor of resulting gelatin were evaluated. All gelatins contained α- and β-chains as the predominant components. Generally, a higher gel strength was found in the freeze-dried gelatin, compared with spray-dried counterpart (p < 0.05). Gel strength of gelatin decreased as the inlet temperature for spray drying increased (p < 0.05). All gelatin samples had creamy whitish color but became more yellow as the inlet temperature for spray drying increased. All gelatin gels were sponge- or coral-like in structure. Gelatin from skin pretreated with citric acid had lower fishy odor/flavor than that from skin pretreated using acetic acid. The lower fishy odor/flavor with coincidentally lower abundance of volatile compounds, including aldehydes, ketones, and alcohols, etc., was found in gelatin obtained by spray drying, in comparison with its freeze-dried counterpart. The lower fishy odor/flavor in spray-dried gelatin was in accordance with the lower thiobarbituric acid reactive substances and peroxide values. Thus, spray drying in conjunction with an appropriated pretreatment could be an effective method for production of gelatin with negligible undesirable fishy odor and flavor.     

Chitosan/Gelatin Blend Membranes for Pervaporation Dehydration of 1,4-Dioxane

Abstract

This paper deals with the development of compatible blend membranes of chitosan (CS) and gelatin (GL) by solution casting and crosslinking with glutaraldehyde. The membranes were tested in pervaporation (PV) dehydration of 1,4-dioxane. Membrane characterizations by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and a universal testing machine were done to understand their physicochemical properties and for their suitability under PV conditions. The blend membranes were more water selective compared to pristine chitosan membrane at 30°C. Flux increased with increasing wt.% of water of the feed and also by increasing the gelatin content of the blend, but selectivity decreased. Sorption experiments gave information on the interaction between feed mixture and membrane polymers. Membranes of this study could extract nearly 97 wt.% of water from the feed mixture. Arrhenius activation parameters and diffusion coefficients estimated from a temperature dependence of PV results could explain the PV results satisfactorily.     

Concentration of gelatin solution with polyethersulfone ultrafiltration membranes

In this work, polyethersulfone (PES) flat sheet ultrafiltration (UF) membranes were prepared by immersion precipitation phase inversion process with polyvinylpyrrolidone (PVP 30K) and acetone as additives. The best preparation condition for PES membranes with high water flux and rejection (to BSA) was decided. It was found that the optimal composition of the polymer casting solution was: 16 wt% (PES), 2 wt% (PVP 30K), and 1 wt% (acetone). Pure water flux of the membrane prepared at this condition reached to 373 L/m² h at 0.1 MPa, and the rejection to BSA was 91%. Compared with other reports, the rejection was slightly low but the flux of the PES membrane was high. When the membrane was used to concentrate gelatin solutions, the rejection value was over 75%. It was found that increasing the feed temperature and transmembrane pressure enhanced the permeation flux, but the rejection decreased slightly. However, increasing the cross-flow velocity of the feed solution simultaneously increased both the permeation flux and the rejection.     

Biodegradable Laminates Based on Gelatin, 2

Compression moulded laminates based on a gelatin or a blended gelatin/starch matrix reinforced by fabrics (linen or silk) were prepared. Three linen or five silk sheets with a powdered matrix between them were compression moulded at 180 °C for several minutes. In addition, cross‐linked laminates were obtained by using methylenedi(p‐phenyl) diisocyanate as a cross‐linking agent expected to obtain an improved integrity between the matrix and the reinforcing elements. In this way a total of ten uncross‐linked and cross‐linked samples differing in the type of the matrix (gelatin or gelatin/starch) and the type of the reinforcing element (linen or silk), both uncross‐linked and cross‐linked, were obtained. All samples were characterized by means of mechanical testing (Young's modulus, tensile strength, elongation at break and impact strength), as reported in Part 1 of this study. In the present Part 2, the same ten samples were artificially weathered, and changes in both the mechanical properties and the specific wear rate with aging time were followed. It was found that the majority of the mechanical parameters generally became worse with aging time; only the Young's modulus and the tensile strength remained on the same order of magnitude for all laminates. The linen reinforced laminates showed much higher values of the deformation at break, the impact strength and the wear resistance in comparison to the silk reinforced laminates. A similar tendency was found for the sliding wear tests against smooth steel counterparts. A reinforcement of gelatin or gelatin/starch with linen was much more effective in improving the laminate wear resistance than a reinforcement with silk. In addition, the abrasion resistance of neat gelatin was found to be much higher than that of the gelatin/starch blend, as evaluated by the Taber index.

Dependence of Young's modulus on aging time for the neat matrix samples (gelatin and gelatin/starch) and the compression moulded laminates reinforced with fabrics.     

Preparation of gelatin/polyoxypropylene grafted copolymers by isocyanate promoted “grafting onto” reaction

A “grafting onto” method for the synthesis of protein-based grafted copolymers is here described. Monofunctional oligo(oxypropylene) chains carrying a terminal isocyanate group were prepared and coupled with gelatin likely by reaction with hydroxyl or primary amino groups. A grafting yield higher than 85% was obtained by using an amount of isocyanate terminated oligo(oxypropylene) of 0.2 mmol per gram of gelatin. A tailored purification procedure based on fractionation with selective solvents was set up to remove homo-coupling products, affording water soluble gelatin-oligo(oxypropylene) graft copolymers having up to 19% wt of grafted oligo(oxypropylene) chains, as indicated by elemental analysis. The composition of all sample fractions were accomplished through NMR, FT-IR and elemental analysis. A negligible insoluble fraction and a water soluble gelatin fraction having a higher modification degree were obtained when the unreacted 1,6-diisocyanatehexane was removed by distillation from the intermediate reagents.The solid films of the graft copolymers showed single-phase morphology by scanning electron microscopy (SEM) observation, confirming the covalent bond formation between oligo(oxypropylene) and gelatin. Simple oligo(oxypropylene)/gelatin blends were prepared and characterized by SEM and stress-strain measurements for comparison.     

The performance of chitosan/gelatin composite microspheres in the wash‐off procedure of reactive dyeing

A chitosan/gelatin composite microsphere (CGMS) adsorbent prepared by inverse suspension was used as a reactive dye washing agent. Techniques such as scanning electron microscopy, X‐ray diffraction analysis, and atomic force microscopy facilitated the evaluation of the materials. A series of experiments were conducted to assess the effect of variables, i.e. initial pH, temperature, microsphere dosage, and contact time. The wash‐off effectiveness increased with increase in temperature and decrease in pH. Results obtained from this study showed that it was possible to reduce the number of wash‐off stages and the water consumption. Furthermore, the microspheres had the properties of resistance to hard water and electrolyte as a wash‐off agent. The efficiency of the microspheres can rival routine detergent in colour fastness, while the chemical oxygen demand of the wash‐off residue of the microspheres amounted to about 1/10 of the chemical oxygen demand of detergent wash‐off residue. This research proved that chitosan/gelatin composite microspheres are a potential candidate for use as an adsorbent washing agent for reactive dyes.     

Alginate/gelatin crosslinked system through Maillard reaction: preparation,characterization and biological properties

Maillard reaction (MR) was studied in aqueous model systems containing gelatin and sodium alginate, which were heat treated for different pH (7, 8, 9, 10 and 11) at three temperatures (70, 80 and 90 °C). Some indicators were used to evaluate this reaction:degree of crosslinking, release of gelatin, free amino groups and browning intensities. The results indicated that alginate/gelatin crosslinked by MR showed an increase of degree of crosslinking as the pH and temperatures were increasing while release of gelatin decreased. Furthermore, samples prepared at a high temperature exhibited stronger browning intensity owing to the formation of Maillard reaction products (MRPs). The obtained materials were analyzed by FTIR and XRD. The antioxidant ability by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and power reducing, as well as the anti-inflammatory activity were investigated.     

Preparation and Characterization of Gelatin Nanofibers Containing Silver Nanoparticles

Ag nanoparticles (NPs) were synthesized in formic acid aqueous solutions through chemical reduction. Formic acid was used for a reducing agent of Ag precursor and solvent of gelatin. Silver acetate, silver tetrafluoroborate, silver nitrate, and silver phosphate were used as Ag precursors. Ag⁺ ions were reduced into Ag NPs by formic acid. The formation of Ag NPs was characterized by a UV-Vis spectrophotometer. Ag NPs were quickly generated within a few minutes in silver nitrate (AgNO₃)/formic acid solution. As the water content of formic acid aqueous solution increased, more Ag NPs were generated, at a higher rate and with greater size. When gelatin was added to the AgNO₃/formic acid solution, the Ag NPs were stabilized, resulting in smaller particles. Moreover, gelatin limits further aggregation of Ag NPs, which were effectively dispersed in solution. The amount of Ag NPs formed increased with increasing concentration of AgNO₃ and aging time. Gelatin nanofibers containing Ag NPs were fabricated by electrospinning. The average diameters of gelatin nanofibers were 166.52 ± 32.72 nm, but these decreased with the addition of AgNO₃. The average diameters of the Ag NPs in gelatin nanofibers ranged between 13 and 25 nm, which was confirmed by transmission electron microscopy (TEM).     

Synthesis and characterization of polypropylene‐grafted gelatin

Modification of polypropylene (PP) has been successfully carried out by graft copolymerization of gelatin, by chemical method using benzoyl peroxide (BPO) as radical initiator. PP was preirradiated by gamma rays at a constant dose rate of 3.40 kGy/h before grafting to introduce hydroperoxide groups. Optimum conditions pertaining to maximum percentage of grafting were evaluated as a function of different reaction parameters. Maximum percentage of grafting of gelatin (115%) was obtained at BPO concentration = 4.132 × 10^?2 mol/L in 120 min at 70°C using 30 mL of water. Characterization of PP‐g‐gelatin was carried out through FTIR, thermogravimetric analysis, and scanning electron microscopy. Swelling studies were carried out in pure, binary, ternary, and quaternary solvent systems comprising distilled water, ethanol, dimethylsulphoxide (DMSO), and N,N‐dimethylformamide (DMF) in different ratios. Maximum swelling of PP‐g‐gelatin (both composite and true graft) was observed in pure solvents that is, DMSO followed by DMF, ethanol, and water and was higher than that observed in the mixed solvent system. Water retention studies of unmodified PP, that is, pristine PP and PP‐g‐gelatin (both composite and true graft) were investigated at different time periods, temperatures and pH. Maximum % water retention for PP‐g‐gelatin (composite; 170%) was observed in 8 h at 50°C in neutral medium (pH = 7). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

TiO_2/壳聚糖/明胶复合棉织物的制备及功能特性

采用了溶胶-凝胶法制备了TiO_2溶胶,使纳米TiO_2在棉织物的表面和内部原位生成,从而实现无机纳米TiO_2粒子与棉织物的牢固结合;再与壳聚糖明胶混合液进行浸轧,制备TiO_2/壳聚糖/明胶复合棉织物材料。用扫描电镜和X射线衍射仪对样品的形貌和结构进行表征,并测试了样品的力学性能、耐洗牢度和光催化性能。结果表明:原位生成的TiO_2与棉织物结合牢固,粒径均匀,分散性较好;纳米TiO_2主要是锐钛矿晶型;所制得试样对活性红染液具有良好的光催化降解作用。     

SOLID BASE CATALYZED TRANSESTERIFICATION OF CANOLA OIL

Catalytic activities of synthesized solid base catalysts (alumina loaded with solution of different potassium compounds such as KI, KF, K₂CO₃, and KNO₃ with the loading amount of 35 wt.%) were tested for the transesterification reaction of canola oil with methanol and ethanol in a batch reactor in a temperature range of 25–60°C and different feed ratios of methanol/oil between 6:1 and 18:1. Synthesized KF/Al₂O₃ solid base catalyst showed the highest activity in the transesterification of canola oil with methanol and gave much stabler methyl ester content during the reaction with the highest yield of 99.6% at the end of the eight-hour reaction time at 60°C, with a methanol/oil ratio of 15:1 and a catalyst amount of 3 wt.%. Formation of K₂O phase and the formation of the surface Al-O-K groups by salt-support interactions were observed during the synthesis of the catalysts. Methanol was found to be much more reactive than ethanol in the transesterification reaction.     

Preparation and characterization of alginate/gelatin blend fibers

Alginate and gelatin blend fibers were prepared by spinning their solution through a viscose‐type spinneret into a coagulating bath containing aqueous CaCl₂ and ethanol. The structure and properties of the blend fibers were studied with the aid of infrared spectra, scanning electron micrography, X‐ray diffraction, and thermogravimetric analysis. Mechanical properties and water‐retention properties were measured. The best values of the tensile strength and breaking elongation of blend fibers were obtained when gelatin content was 30 wt %. The water‐retention values of blend fibers increase as the amount of gelatin is raised. The structural analysis indicated that there was strong interaction and good miscibility between alginate and gelatin molecules resulted from intermolecular hydrogen bonds. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1625–1629, 2005