Influence of n-ZnO Morphology on Sulfur Crosslinking and Properties of Styrene-Butadiene Rubber Vulcanizates

This paper examines the influence of the morphology of zinc oxide nanoparticles (n-ZnO) on the activation energy, vulcanization parameters, crosslink density, crosslink structure, and mechanical properties in the extension of the sulfur vulcanizates of styrene-butadiene rubber (SBR). Scanning electron microscopy was used to determine the particle size distribution and morphology, whereas the specific surface area (SSA) and squalene wettability of the n-ZnO nanoparticles were adequately evaluated using the Brunauer–Emmet–Teller (BET) equation and tensiometry. The n-ZnO were then added to the SBR in conventional (CV) or efficient (EV) vulcanization systems. The vulcametric curves were plotted, from which the cure rate index (CRI) rate of the vulcanization and the activation energy were calculated. The influence on the mechanical properties of the SBR vulcanizates was stronger in the case of the EV curing system than when the CV curing system was used. Of the vulcanizates produced in the EV curing system, the best performance was detected for n-ZnO particles with a hybrid morphology (flat-ended rod-like particles on a “cauliflower” base) and high SSA. Vulcanizates produced using the CV curing system showed slightly better mechanical properties after the addition of nanoparticles with a “cauliflower” morphology than when the rod-like type were used, irrespective of their SSA. In general, nanoparticles with a rod-like structure reduced the activation energy and increased the speed of vulcanization, whereas the cauliflower type slowed the rate of the process and the vulcanizates required a higher activation energy, especially when using the EV system. The crosslink structures were also more clearly modified, as manifested by a reduction in the polysulfidic crosslink content, especially when n-ZnO activators with a rod-like morphology were applied.

Sepiolite-based adsorbents for carbon dioxide capture

Sepiolite and the sepiolite-based materials were studied in terms of carbon dioxide adsorption. The pore structure and the surface characterization of the obtained materials were specified based on adsorption-desorption isotherms of nitrogen measured at –196oC and carbon dioxide at 0oC. The specific surface area (SSA) was calculated according to the BET equation. The pore volume was estimated using the DFT method. Pristine sepiolite has shown the following value of SSA and CO2 uptake at 0oC – 105 m2/g and 0.27 mmol/g, respectively. The highest value of these parameters was found for material obtained by KOH activation of mixture sepiolite and molasses (MSEP2) – 676 m2/g and 1.49 mmol/g. Sample MSEP2 also indicated the highest value of total pore volume and micropores volume with a diameter up to 0.8 nm.

Drying kinetics and sorption behavior of two varieties banana (sagor and sabri) of Bangladesh

The study was concerned with determining the drying kinetics and sorption behavior of two varieties ripe banana of Bangladesh namely, Sagor and Sabri. The fresh ripe banana collected from the local market were sliced into three different thicknesses (4 mm, 6 mm and 8 mm) and dried at 45°C, 55°C and 65°C in a cabinet dryer. The result showed that the drying rate increases with the increase in temperature and decreases with the increase in slice thickness. The sorption properties of dried banana were studied over a wide range of water activity (0.11-0.93). The BET and GAB models were fitted to the sorption data. It was found that both varieties gave sigmoid (type II) shape isotherm and GAB equation gave the much higher value of monolayer moisture content compared to BET equation. The chemical compositions of fresh and dried banana were determined. The dried products gave substantially higher solid content as well as protein, ash and carbohydrate. SAARC J. Agri., 16(2): 181-193 (2018)

Water Vapor Adsorption by Some Manganese Oxide Forms

Manganese oxide forms prepared by different methods differ by their compositions, phase ratios in polyphase samples, and crystallite sizes (XRD and TEM characterization). Among the phases, tunnel-structured β-MnO2 (pyrolusite), α-MnO2 (cryptomelane), ε-MnO2 (akhtenskite), and β-Mn2O3 (bixbyite) have been identified. Water vapor sorption isotherms showed substantial differences in the affinities of water molecules to oxide surfaces of the manganese oxide forms under study. The parameters of the BET equation and pore size distribution curves have been calculated. The manganese oxide forms have mesoporous structures characterized by uniform and non-uniform pore sizes as well as by moderate hydrophilic behavior.

SORPTION CHARACTERISTICS OF BREAD FROM EINKORN

Определены сорбционные характеристики хлеба из зерна полбы с целью оптимизации условий хранения продукта. Мука из зерна полбы типа 2300 была изготовлена на кафедре технологии зерновых, кормовых, хлебобулочных и кондитерских изделий Университета пищевых технологий, имела основные параметры – влажность 12%, содержание золы 2,3%, кислотность 1,9°H, содержание влажного глютена 1,6% и представляла собой сухое порошкообразное вещество бежево-коричневого цвета, с типичными для высушенного продукта вкусом и запахом, не имеющее посторонних привкуса и запаха. Из полученной муки был выпечен хлеб: масса 398 г, объем 560 см3, формоустойчивость (H/D) 0,41; цвет корки темно-коричневый, корка гладкая, грубая; мякиш насыщенно-желтого цвета, с равномерной пористостью, ощущением привкуса арахиса. Технологические потери составили 9,54. Сорбционные характеристики образцов испеченного хлеба определяли с использованием аппарата Autosorp. Для контроля влажности использовали метод высокоэффективной жидкостной хроматографии. Результаты эксперимента описывали тремя модифицированными моделями. Установлено, что модифицированная модель Oswin является наиболее адекватной для описания сорбционных изотерм исследованного продукта – хлеба из зерна полбы. Мономолекулярная влажность, рассчитанная путем линеаризации уравнения Brunauer–Emmett–Teller (BET), для исследованных образцов хлеба из зерна полбы при температуре 25°С и относительной влажности воздуха 20–60% для процессов адсорбции и десорбции составила 4,80 и 4,69% с. м. соответственно. Sorption characteristics of bread from the einkorn grain are defined in order to optimize the storage conditions of the product. Flour from the einkorn grain of type 2300 was made on chair of technology of grain, fodder, bakery and confectionery of University of food technologies, had the basic parameters – humidity of 12%, ash content of 2,3%, acidity of 1,9°H, the content of damp gluten of 1,6% and represented dry powdery substance of beige and brown color, with the taste and smell typical for the dried product which has no foreign taste and smell. From the obtaining flour have baked bread: weight 398 g, the volume of 560 cm3, formability (H/D) 0,41; color cover dark brown, cork smooth, tough; pulp deep yellow color, with uniform porosity, a sense of mild taste of peanuts. Technological losses amounted to 9,54. Sorption characteristics of baked bread samples were determined using Autosorp apparatus. The method of high-performance liquid chromatography was used for humidity control. The results of the experiment were described by three modified models. It is established that the modified Oswin model is the most adequate for the description of sorption isotherms of the studied product – bread from the einkorn grain. Monomolecular moisture calculated by linearization of the Brunauer–Emmett–Teller (BET) equation for the studied samples of bread from the einkorn grain at a temperature of 25°C and a relative humidity of 20–60% for the adsorption and desorption processes was 4,80 and 4,69% of the dry mass, respectively.

Activated carbons prepared from hazelnut shells, walnut shells and peanut shells for high CO2 adsorption

Research treats about producing activated carbons for CO2 capture from hazelnut shells (HN), walnut shells (WN) and peanut shells (PN). Saturated solution of KOH was used as an activating agent in ratio 1:1. Samples were carbonized in the furnace in the range of temperatures 600°C–900°C. Properties of carbons were tested by N2 adsorption method, using BET equation, DFT method and volumetric CO2 adsorption method. With the increase of carbonization temperature specific surface area of studied samples increased. The largest surface area was calculated for samples carbonized at 900°C and the highest values of CO2 adsorption had samples: PN900 at 0°C (5.5 mmol/g) and WN900 at 25°C (4.34 mmol/g). All of the samples had a well-developed microporous structure.

Pengaruh Kadar Air dan Persamaan Model Bet untuk Prediksi Masa Simpan Kakao (Theobroma cacao L.)

Effect of moisture content and BET equation to the shelf life of cocoa (Theobroma cacao L.) has been conducted. Increasing the quality of cocoa beans is with proper post-harvest handling, including how the harvest, the level of ripeness, curing, fermenting, drying up storage. The purpose of this study was to determine the water content and the appropriate levels of critical in determining the shelf life of cocoa. The benefits of this research are as information for farmers in determining the shelf life of cocoa in order to design a storage area corresponding to the respiratory system owned by cocoa. The results showed that the effect of fermentation facilitator (Staphilococcus cerevisiae) and drying temperature on water content showed that the fermentation facilitator (Staphilococcus cerevisiae) highly significant effect on water content. The drying temperature is also highly significant effect on water content. BET equation obtained was Y = 2,912x + 1.238 (R2 = 0.965), Y = 2,897x + 1.353 (R2 = 0.968) and Y = 2,806x + 1.89 (R2 = 0.954).