جستجوی مقالات مرتبط با کلیدواژه « experimental design » در نشریات گروه « مواد و متالورژی »

Dissolving pulp or alpha cellulose is one of the most important and valuable biopolymers produced by wood pulp factories. One of the most important applications of dissolving pulp is in military industries to produce of commercial nitrocellulose. In this research, all data of literature about common and developing methods for producing the alpha cellulose are presented. Among the important techniques for purifying wood pulp are cold caustic extraction (CCE) and hot caustic extraction (HCE). These processes were chosen as the best methods for purifying wood pulp owing to their simplicity, low sodium hydroxide consumption and lower production time and optimal energy consumption and these process were investigated precisely in this research. In order to determine the optimal and economic conditions for the caustic extraction process, various experiments were designed by Minitab software and then implemented to determine the contribution of various factors including, concentration of sodium hydroxide, reaction time, speed of stirring and reaction temperature for the purification of industrial wood pulp with 85% alpha cellulose content to 96% dissolving pulp. Based on the experimental data, the concentration of the sodium hydroxide has the highest effect in the purification process. Also this process should be done at low temperature (30 °C). The products were quality controlled by different laboratory methods and equipments including, determination of alpha cellulose content, viscosity value, moisture percentage, ash percentage, extraction with acetone, FT-IR, XRD and ICP spectroscopies along with TGA analysis. These data confirmed that the quality of the produced dissolving pulp sample is same as the linter sample that was used for nitration process and producing of the commercial nitrocellulose.

The increasing demand for highly pure crystalline materials with narrow Crystal Size Distribution (NCSD) leads related industries to utilize the Draft Tube Baffle (DTB) Crystallizers. The product Crystal Size Distribution (CSD) significantly alters by enhancing the mixing characteristics inside crystallizer, therefore acquiring a precise vision of hydrodynamics will help in designing and scaling up the DTB crystallizer. There are numerous studies on the flow field in the DTB crystallizers, but none of them investigates the interactions and effects of the internal arrangement of DTB crystallizers. In this study, the optimal configuration of three geometrical parameters (tube diameter, the ratio of tube diameter to baffle diameter, and the width of the annular settlement zone) was obtained by numerical simulation of the flow field in 18 DTB crystallizers. The interaction of parameters was studied by employing the general factorial method. Each crystallizer was divided into five compartments where various results such as the distribution of axial velocity, the turbulent kinetic energy, and streamlines were considered for data analysis. The results demonstrate that the hydrodynamics requirements in each compartment will be satisfied in crystallizer with 17.5 cm tube diameter, the ratio of tube diameter/baffle diameter=0.5, and the width of the annular settlement zone equal to the tube diameter.

Polypropylene has a poor toughness and impact strength. So, it needs to modification for some applications. Addition of elastomers to PP to enhance the toughness is a traditional way, but it causes to decrease of the modulus and tensile strength of products. In this research a hybrid composite system including PP, thermoplastic elastomer, nanoparticle and compatibilizer was prepared by melt mixing method. The interaction effect of nanoparticle, thermoplastic elastomer, and compatibilizer on the tensile and impact properties of composites were studied using the experimental design technique; response surface methodology. The results of microscopy analysis showed that the blends were two-phase, where thermoplastic elastomer was dispersed phase. The elastomeric particle size was in the range of 100-400 nm and by increasing the rubber content, rubber particle size increased. Nanosilica dispersed in the presence of compatibilizer had a particle size between 40-90 nm, while the lack of compatibilizer created some agglomerations of nanoparticles. As elastomer content increased, the strain of failure and impact strength of nanocomposites increased, while the Young modulus and tensile strength were decreased. Addition of nanosilica to the PP in the absence of compatibilizer lowered the tensile and impact strengths. While, addition of nanosilica along with compatibilizer improved the tensile modulus of blends. According to the experimental design results, some mathematical relations were presented to predict the mechanical properties. The optimal hybrid nanocomposite had significantly higher impact strength than pure PP while their moduli were in the same order.