Showing 9 results for Ft-Ir
Volume 7, Issue 1 (7-2023)
Abstract
Research subject: The binder system based on of hydroxyl-terminated polybutadiene resin (HTPB), consist of dioctyl sebacate as a plasticizer (DOS), and toluene diisocyanate as the curing agent. Reaction between the HTPB hydroxyl resin group and the curing agent isocyanate group produces a polyurethane mesh to produce a rubber with the desired properties. In this research, the rheological and mechanical properties of the binder system were investigated and Physical properties compared in the presence of three chemicals retarder polymerization Polyurethane, oxalic acid, maleic acid and tetracycline.
Research approach: Oxalic acid, maleic acid and tetracycline alter the properties of the binder system by specific mechanisms. Oxalic acid and maleic acid react with the isocyanate group of the curing agent to produce amides and reduce the viscosity of the binder system. Due to its chemical structure, tetracycline reacts with the curing agent and prevents the development of the main reaction between the HTPB resin and the curing agent TDI and reduces the viscosity. Infrared Fourier transform (FT-IR) test was also used to investigate the functional mechanism of these compounds. In this test, the intensities of the spectra related to each sample were compared with each other and the type of function and mechanism of each of the oxalic and maleic substances and tetracycline were determined.
Main results: The structure of the reaction product between HTPB resin and oxalic acid, maleic acid and tetracycline with curing agent was determined and confirmed by FT-IR spectrum. In-situ FT-IR study showed reduction in isocyanate peak intensity after 60/90 min. Chemorheological investigation showed best performance at 0.05% concentration for all retardants, among them tetracycline, oxalic acid and maleic acid depicted 54%, 48% and 47% reduction in viscosity build-up; respectively. Adding 0.05% of tetracycline to binder system resulted in about 20% decrease in cross link density probably due to better interaction with curing agent which emphasized the best performance of 0.05%-tetracycline as retardant.
Anita Shahifar, Zahra Ghasemi, Reza Shahifar,
Volume 13, Issue 1 (1-2024)
Abstract
Chitin is an important natural polysaccharide that is found in the cell wall of some organisms including crustaceans. The chitosan polymer, which is extracted from chitin, plays a very important role in the production of a wide range of materials used in food products. The present study aimed to extract chitin from the shell of the farmed shrimp Penaeus vannamei using the chemical method, through the steps of deproteinization, demineralization and deacetylation and using it as a natural coating with no negative effects, for protecting the covering of the fruits. To ensure the standard and determine the quality of the chitosan synthesized, FT-IR test was performed. Then, grape and strawberry fruits were covered by chitosan concentrations of zero (control sample), 0.2 and 0.5% as different treatments. During the two-month storage period at 0-4 degrees Celsius, and to control of the changes in the fruits, the appearance quality factors in fruits were controlled weekly. Based on the results, the efficiency of chitin production from the shell was 58%, chitosan production from chitin was 84% and therefore, the efficiency of chitosan production from the shell was 48%, which is a suitable rate. The control samples of both fruits lost their appearance and shriveled in the first week of the test, and spoiled after three weeks. However, in bothe grapes and strawberries coated with dissolved chitosan with a concentration of 0.5%, the best antibacterial coating was created for the fruits and their appearance quality was maintained during the storage period of two months.
Volume 13, Issue 58 (0-0)
Abstract
Chemical modification of starch is of the prevalent used methods in order to improve its physicochemical attributes. In this study phosphorylated and hydroxypropylated wheat starches were produced with 0.096 and 2.106% degree of substitution, respectively; and then some of their physicochemical and rheological attributes were studied. The implemented chemical changes due to hydroxypropylation and phosphorylation on native wheat starch were exhibited by FT-IR. X-ray diffraction (XRD) results showed that the native and phosphorylated wheat starches had the most and least amount of crystallinity with 17.34 and 16.14%, respectively. The influence of temperature on swelling power revealed that the native (Ea=46.111) and hydroxypropylated (Ea=26.603) wheat starches had the most and least thermal sensitivity, respectively. Besides, in the case of solubility index, it was observed that native (Ea=77.674) and phosphorylated (Ea=44.478) starches had the most and least thermal sensitivity, in the order given. The high value of determination coefficient (0.895-0.979) attained from the modeling results of the solubility changes with temperature using two power law equations, demonstrated the high capability of these models in prediction. It was seen that hydroxypropylation and phosphorylation of wheat starch resulted in 2.65 times increase and 17.58 times decrease in paste clarity compared to native starch (p<0.05), respectively. Among the used rheological models, the Herschel-Bulkley model was found to be more suitable to predict the flow characteristics of the starch samples.
Volume 15, Issue 84 (2-2019)
Abstract
Volume 15, Issue 85 (3-2019)
Abstract
The aim of the study was to determine the Suitable concentration of Arabic gum, sodium caseinate and beta-cyclodextrin to encapsulation of pomegranate seed oil. For this purpos Beta-cyclodextrin, sodium caseinate and Arabic gum as wall covering by Mixture Design for trapping pomegranate seed oil were used and Then optimized samples with the least turbidity to determine viscosity, encapsulation efficiency, SEM, FT-IR and DLS were choiced. Turbidity of treatments increased at high levels of sodium caseinate as well as in the combination of Arabic gum with beta-cyclodextrin in lack of sodium caseinate. Results of Viscosity showed that the sample containing beta-cyclodextrin-sodium caseinate had a high viscosity than the Arabic gum-sodium caseinate. The maximum encapsulation efficiency was observed in sample containing of sodium casheinate (37.1%) and Arabic gum (62.9%), which had the lowest surface oil. According to the results of DLS , the smallest capsule diameter was related to the sample containing of beta-cyclodextrin and sodium caseinate (439 nm), and had an inverse relationship the diameter of the capsules with the polydispersity index, and values of Zeta potential in the sample containing 62.9% Arabic gum + 37.1% Sodium caseinate was maximum (-25.7). FT-IR results showed the electrostatic interactions in the formation of capsules and their stability. According to SEM images, the capsules irregularly and different morphologically were formed. Therefore, according to the results, 37.1% sodium caseinate and 62.9% Arabic gum is suggested for encapsulation of pomegranate seed oil.
Volume 16, Issue 89 (7-2019)
Abstract
The propose of this study was to investigate the production of biodegradable edible film............
Volume 22, Issue 2 (3-2020)
Abstract
Converting feedstock into biochar is a popular approach to overcome the disposal problem, yet the role of waste type and pyrolysis temperature on biochar properties is not understood well. In this study, biochars were produced from various feedstock such as tea waste, apple wood, wheat straw and walnut shell at 300, 400, 500 and 600°C with 1-hour residence time. The results showed that increase in pyrolysis temperature significantly decreased biochar mass yield. The maximum and minimum mass yields were observed in walnut shell at 300˚C and apple-wood-derived biochars at 600˚C by 69 and 20%, respectively. The produced biochar had pH range between 5.3 to 9.7, and its pH value and ash content increased significantly with increasing pyrolysis temperature, except for walnut shell. Total concentrations of P, Ca, K, Na, Fe, Zn, Cu, and Mn and available concentrations of K, Ca, Mg, and P increased with pyrolysis temperature increasing in all samples, except at walnut shell-derived biochar. According to CHN analysis, by increasing pyrolysis temperature, the total carbon concentration increased but total nitrogen and hydrogen concentrations decreased. The pH value decreased with time until 72 hours, beyond which a near steady-state condition was attained. Relationships between pH and CaCO3-eq content of biochars were close and linear. The FT-IR spectra showed that aromatic C increased by increment in heating. Also, by increasing pyrolysis temperature, the mean pore diameter decreased but micropores volume increased and led to increase in the specific surface area of biochars. The results of this study suggest that biochars produced at 300 and 400˚C may have potential as fertilizer in calcareous soils because of low pH and EC, with high mass yield.
Volume 22, Issue 2 (6-2022)
Abstract
Fine-grained soils, especially those consist of high content clay minerals, generally have high strength in dry state, but they loss their strength when subjected to absorb water as well as they may be swell. These phenomenon may lead to damage the structures located on them and it is required to stabilize them with different additive materials. Common additives for stabilization of problematic soils are cement, lime, fly ash, etc., which are almost costly and have environmental consequences. Nowadays, non-traditional material such as polymeric materials were added to the soils in order to their stabilization.
In this research, the effect of polyester polymer resin on the physical and mechanical properties of fine-grained bentonite soil, with liquid limit and plasticity index of 226% and 179% respectively, was studied by performing Atterberg limits and unconfined strength tests. For this purpose, a polyester polymer resin were added to bentonite soil with various amount of 1.0, 2.5, 5.0, and 7.5 percent in dry weight. Soil mixtures were cured about 7 days and Atterberg tests were performed on them. Moreover, cylindrical specimens with 50 mm in diameter and 100 mm in height were prepared and cured during 7, 14 and 28 days. Soil specimens compacted in a splitted steel mold at four equal thickness layers. Then, the unconfined compression tests were carried out on these specimens with loading rate of 0.5 mm/min.
The results of Atterberg tests indicated that the addition of polyester resin reduces liquid limit and increases plastic limit of bentonite and consequently it is led to decrease in plasticity index of the soil. Maximum decrements in liquid limit and plasticity index observed in treated soil with 7.5 percent polyester, which are about 41.0 and 65.0 percent respectively. In addition, the polyester resin improves the unconfined compressive strength of the soil and the rate of increment is high when the polyester amount rises from 0 to 7.5%. It was revealed that the polyester resin influences the unconfined strength considerably in a short time, and the rate of improvement gradually decreases with passing time. For example, adding 5.0 percent polyester polymer resin to bentonite soil improves the strength up to 2.05, 2.11 and 2.58 times respectively after curing times of 7, 14 and 28 days. It also means that after 7 day curing time the improvement effect of stabilizer is considerable and by passing time its effect diminishes. Moreover, adding polyester polymer resin to the soil decreases deformability of soil; it means that this additive cause the treated soil exhibits more brittle behavior rather than the pure soil. The photos of specimen after failure explain that failure surface of pure bentonite is inclined in relation with horizontal, while it tends to vertical direction in treated specimens. Analysis of SEM images, results of XRD analysis and FTIR spectroscopy suggest that polyester stabilizer penetrates into the layers of soil particles and, by inducing effective interaction makes the layers closer or sticks them together. These phenomena decrease water absorbing tendency in soil minerals and improve the plastic characteristics and shear strength of the soil.
Volume 25, Issue 6 (11-2023)
Abstract
In the present study, bacterial endophytes were obtained from weeds of potato fields. Their antagonistic activity was screened against potato storage pathogen, Pectobacterium carotovorum subsp. carotovorum (Pcc) (JX029052), in the maceration assay. An endophytic strain, PC-2B was isolated from Convolvulus arvensis L. as a dominant weed of potato fields. In vivo application of this strain led to 58.8% reduction in tuber decay. This motile strain that can produce amylase was identified as Pantoea sp. using phenotypic features and 16S rRNA sequencing. Following PC-2B treatment, 56.7% Reduction in Disease Incidence (RDI) was obtained in preventative and 52% in curative challenges under semi-practical storage trails. Anti-Pcc bioactive compounds of Pantoea sp. was extracted and identified based on H NMR and FT-IR techniques. Two peptide antibiotics including Pantocin A and B with inhibitory effect against Pcc were characterized. These results might indicate that the tested Pantoea strain could be a promising candidate to protect potato tubers against soft rot disease caused by Pcc. However, large-scale complementary trials have to be conducted to validate these results before any recommendations.
