The Effect of Drying Temperature on Physical Properties of Thin Gelatin Films

The molecular morphology of thin gelatin films, controlled through the casting temperature, was monitored by wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Gelatin films dried at lower temperatures had a markedly higher crystalline or helical structure with a slightly higher T_g and lower ΔC_p compared with hot dried films, which had a more coiled structure. The relationship between molecular morphology and gelatin-water interaction in terms of hydration behavior and water diffusivity was assessed using dynamic vapor sorption (DVS). The sorption capacity increased and the level of hysteresis decreased with increasing the degree of crystallinity. The difference in the aging behavior of the films was explained in terms of the difference between the glass transition and aging temperatures, (Tg – Ta).     

Biodegradable sol–gel coatings of waterborne polyurethane/gelatin chemical hybrids

Gelatin from cold fish skin has strong mechanical properties and biodegradability. Cold fish gelatin was introduced into waterborne polyurethane (WPU) by covalent bonding to reinforce and render biodegradability of WPU. For this, gelatin was chemically modified with vinyltrimethoxysilane (VTMS) via the sol–gel type reactions and incorporated into hydroxyl ethyl acrylate (HEA) termini of WPU by UV curing. Covalent incorporations provided the hybrids with enhanced water resistance, hardness, glassy and rubbery state moduli, yield strength, and thermal resistance of soft segment along with significantly enhanced biodegradability both in trypsin solution and soil.     

Microstructure and elastic modulus of mixed gels of gelatin + oxidized starch: Effect of pH

The microstructure and elastic shear modulus of cold-set gels formed from high-sugar aqueous mixtures of gelatin (7 wt%) + oxidized starch (0-6 wt%) were investigated as a function of pH. Samples prepared at 90 °C, with citric acid added to adjust the pH, were rapidly quenched to ∼1 °C, subjected to a standard thermal treatment (40 °C for 10 min), and then investigated by confocal microscopy and small-deformation rheology at 24 °C. Under ‘natural’ conditions of pH ≈ 5.2 (no citric acid addition), the samples exhibited phase separation with a characteristic spinodal-type morphology. The spatial extent of the structural heterogeneity, expressed by a single length-scale parameter, was found to increase with starch concentration. Gradual acidification led to a reduction in this length-scale parameter, leading to complete inhibition of phase separation below a certain characteristic pH value in the range 4.5-4.9 (depending on starch content). Over the investigated pH range, the effect of starch addition was to reduce the storage modulus of the resulting gel. This reduction was more pronounced for the phase-separated samples. The pH of maximum rigidity was found to decrease from pH_max ≈ 4.6 for 0 wt% starch to pH_max ≈ 4.2 for 6 wt% starch. Taken all together, these observations can be understood in terms of the effects of pH on the cross-linking behaviour of the gelatin and the nature of the gelatin-starch electrostatic interactions. The microscopy results are consistent with a transition in behaviour from thermodynamic incompatibility (segregative interactions) at high pH to soluble complexation (associative interactions) at low pH.     

Polyacrylamide-gelatin polymeric networks: effect of pH and gelatin concentration on the swelling kinetics and mechanical properties

This work presents the synthesis of polyacrylamide-gelatin (PAM-G) semi-interpenetrating hydrogels, as well as the study of the swelling capacity of this material at different pH’s, and we report its Young modulus. The hydrogels were crosslinked with N,N′-methylenebisacrylamide and synthesized at different acrylamide/gelatin weight relationship. It was observed that the swelling capacity of the hydrogels increases when the gelatin concentration is increased; while the Young modulus (at the swelling equilibrium) decreases lightly. Therefore, the gelatin has a small effect in the Young modulus, unlike its influence in the swelling ability. The swelling experiments reveal that the PAM-G hydrogels increase its swelling capacity in alkaline mediums because the presence of the hydrophobic functional groups (mainly COO⁻) in the gelatin structure.     

Rheokinetic model to characterize the maturation process of gelatin solutions under shear flow

The characterization of maturing gelatin solutions in shear flow is required for an appropriate formulation of food products. Under static conditions, the maturation process of gelatin solutions may be described through a basic structural parameter evolving to the percolation value (gel point). Within the rheological framework, two asymptotic viscosities are well identified for the maturing process of gelatin solutions at the limit zero shear rate. One involves the initial solution viscosity that may be associated with the null structural parameter (the microstructure is not formed yet). The other is the percolation zero shear rate viscosity (assuming an infinite value when approaching the gel time) and corresponds to the maximum value of the structural parameter. Under flow, thixotropic theories combined with the knowledge of suspension rheology allow one to convert directly experimental data obtained as shear stress versus time for a given shear rate into the time evolution of the structural parameter. Consequently rheometric experimental data available places the search for a rheokinetic model of the structural parameter. Here, different expressions for this model are investigated, mainly those involving both the rates of structure breakdown and buildup, where the average cluster size is affected by the shear rate. The rate equation thus obtained may be then applied to arbitrary shear rate histories. Numerical results of the rheokinetic model proposed in this work fit well experimental rheometric data obtained in shear flow for the maturing of different gelatin solutions. Experimental data acquired in this work are presented and discussed in relation to those reported previously in the literature.     

One-pot synthesis of gelatin-based,slow-release polymer microparticles containing silver nanoparticles and their application in anti-fouling paint

Gelatinous polymer matrix microparticles containing silver nanoparticles (AgNPs) were prepared by a novel method to obtain quasi non-swelling anti-fouling paint additives with slow-release characteristics. A w/o type dispersion were elaborated with the aqueous phase of gelatin, urea, silver-nitrate and formaldehyde dispersed in linseed oil. Gelatin was cross-linked by formaldehyde, together with urea for limiting the swelling of the product. Silver-nitrate was reduced with the assistance of gelatin and formaldehyde into homogenously dispersed AgNPs. The microparticles and embedded AgNPs were visualized by scanning and transmission electronmicroscopy. Encapsulated AgNPs with ∼18 nm crystallite size were identified by X-ray powder diffraction. Characterization of gelatin–urea–formaldehyde polymer matrices was carried out by attenuated total reflectance FTIR spectroscopy. Silver dissolution from microparticles and paints with AgNP-containing microparticles was measured by inductively coupled plasma spectrometer and resulted in highly sustained release, compared to unmodified gelatin microparticles and paints containing uncapsulated silver salts. A 7-month-long fouling experiment run in natural sweetwater media showed that solvent-based acrylic paint with AgNPs-containing gelatinous microparticles as additives offered resistance against biofouling at low Ag-release ratio.     

热降解明胶的研究

报道了明胶热降解反应,并考察了明胶质量分数、降解时间、降解温度、明胶溶液pH值等因素对明胶热降解反应的影响规律。结果表明:热催化是明胶降解的有效方法,较合适的降解条件为明胶质量分数10%,体系pH值7.00,降解温度121℃,降解时间2 h。     

Thermal,Mechanical and Morphological Characterization of Jute/Gelatin Composites

Jute fabrics/gelatin biocomposites were fabricated using compression molding. The fiber content in the composite varied from 20–60 wt%. Composites were subjected to mechanical, thermal, water uptake and scanning electron microscopic (SEM) analysis. Composite contained 50 wt% jute showed the best mechanical properties. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength of the 50% jute content composites were found to be 85 MPa, 1.25 GPa, 140 MPa and 9 GPa and 9.5 kJ/m², respectively. Water uptake properties at room temperature were evaluated and found that the composites had lower water uptake compared to virgin matrix.     

Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.     

二次正交旋转组合设计优化明胶微球的合成工艺

为了优化乳化固化法合成明胶微球的工艺,采用二次正交旋转组合设计分析了pH值、交联剂质量分数及W/O体积比对于明胶微球品质(溶胀度、平均粒径)的影响,并建立了相应的预测模型。方差分析的结果表明:pH值、交联剂质量分数及W/O体积比对溶胀度和平均粒径两项指标均有显著影响。优化的工艺参数为:pH=4.5,交联剂质量分数为0.7,W/O体积比为3。对应的微球溶胀度及平均粒径的预测值分别为:380.35%和16.61μm。试验证明:应用二次正交旋转组合设计所得到的微球合成工艺参数是可行的。