فهرست مطالب somayyeh mohammadian gezaz

A key issue to the development of using modified bitumen is the high price of additives, including fibers, which in turn, can increase the cost of bitumen and modified asphalt mixtures. In contrast to other research, in this study, cheap waste materials obtained from paper-making manufacture, including Liquor and cellulose microfibers (obtained from waste pulp mills) are used to improve the properties of modified bitumen while reducing the cost of producing modified bitumen. Further, bitumen modified by styrene-butadiene-styrene (SBS) and styrene-butadiene rubber (SBR) were examined in this study in order to compare with bitumens modified by cellulose microfibers. For this purpose, SHRP tests, including dynamic shear rheometers and bending beam rheometers, were performed on polymer and fiber modified specimens. Based on the results of this study, all modified samples displayed a significant increase in bitumen hardness. Tests of classical bitumen and rotational viscosity demonstrated that polymers of butadiene-styrene-styrene and styrene-butadiene rubber significantly enhanced the viscosity and hardness of bitumen in comparison with other polymers. Consequently, the mix and compaction temperature of the modified samples with these additives have significantly increased. Results revealed that Liquor-containing bitumen improved its high-temperature performance, but it had a negative effect on the bitumen's low-temperature performance. Furthermore, cellulose microfibers had less effect on improving bitumen's properties than polymers such as styrene-butadiene-styrene and styrene-butadiene-rubber. However, cellulose microfibers' capabilities to modify the properties of bitumen, including a lower mixing and compaction temperature of asphalt mixtures than polymers and cheaper production and implementation of asphalt pavements due to the use of cheap waste materials, cannot be overlooked.

In this study, after the preparation of unsaturated polyester with various ratios of anhydride monomers, the effects of nanosilicate on the polymerization, curing behavior, and mechanical properties were investigated. The unsaturated polyester resin was synthesized at various molar ratios of anhydride monomers (maleic/phthalic: 10 to 90%) and propylene glycol. Acid number measurement was used to evaluate polymerization. With an increase in the molar maleic content, the time of polymerization reaction and the acidic number increased. In the next step, the resin was cured with an accelerator and initiator, and styrene monomer. curing behavior was determined using a curing curve and gelation time measurement. The curing curve showed that by increasing the maleic anhydride monomer ratio from 10% to 90%, the curing time decreased by 77%, and the maximum thermogenic temperature increased by 24%. Increasing the maleic content from 10 to 90% resulted in tensile strength changes from 11 to 70 MPa and tensile modulus from 60 to 359 MPa. The impact strength and the heat distortion temperature increased and became plateaued at higher maleic percentages. The nanocomposites were prepared with 50 mol% maleic anhydrides, containing 2, 4, 6, and 8 wt.% of nanosilicate. By increasing the amount of nanoclay, the curing time decreased and the maximum exothermic temperature increased. Mechanical properties were evaluated by using Heat Deflection Temperature (HDT), tensile properties, impact strength, and surface hardness tests. The impact strength and the heat distortion temperature also showed an upward trend with an increase in the amount of nano, even in small quantities. By adding 8% nanoclay to the matrix, the impact strength and heat deflection temperature increased by 11% and 13%.

In this study, the polyamide6/ thermoplastic starch (TPS) blends were prepared. Firstly, the starch became thermoplastic and was chemically modified using glycerol and maleic anhydride, under different conditions. After the preparation of maleated thermoplastic starch (MTPS), polyamide6/ MTPS (or TPS) blends were produced considering three variables; and the effects of various variables were investigated on their bio-degradability. In both steps, the experimental design method of Response Surface Methodology (RSM) was used. In the first step, the effects of Maleic Anhydride (MA) amount, time and temperature of the reaction were evaluated on the “degree of MAgrafted on the starch”. With increasing MA content, the processing time and temperature, higher MA grafting was achieved. While at a higher temperature and longer time, it was constant or slightly decreased. The highest grafting of MA was obtained at 140 ºC, 10 min and 4-6 % MA. In the second step, the influences of polyamide6/starch ratio, degree of MA grafting and degradation time were studied on the bio-degradability of the blends in the active sludge, in 90 days. Samples having TPS, showed some weight losses (or degradation) comparing to the purepolyamide6 which had no degradation. The amount of bio-degradation increased clearly with increasing MA grafted on the starch and MTPS amount. A blend containing 30 % MTPS, reached 45 % weight loss after 75 days. Using RSM, the equations of “degree of MA grafting” and “bio-degradation” versus variables, were obtained with suitable accuracy and low error. Besides, the interactions between the parameters were discussed considering 3D plots and the coefficients of the equations. The predicted results from the equations had a good fitting with the experimental data.

The role of carbon black (CB) in the viscoelastic behaviour of rubber compoundswas investigated to better understand the reinforcing mechanism. The influenceof CB nanoparticles on the strain-dependency and relaxation phenomena ofseveral styrene butadiene rubber (SBR) compounds was evaluated using rubberprocess-analyzer (RPA). Rheological results of uncured samples showed that reducedcomplex modulus with strain strongly depend on CB-rubber interactions. Filled mastercompounds showed greater modulus compared to raw SBR, which dropped ratherabruptly; meaning more noticeable non-linear viscoelastic behaviour. The observedtrend of damping factor recognized the linear viscoelastic behaviour for strain <15%,however, at higher strains a large positive deviation was noticed. In the strain regionunder 15%, CB-filled rubber showed more elastic behaviour than gum; more elastic asthe CB loading increased while in the non-linear zone, the reverse trend was observed.Torsion relaxation modulus based on standard linear solid (SLS) model was plotted andfound disputable changes regarding to varied factors. Both values of relaxed modulusand the relaxation slope increased as the functions of CB surface area and content,and also the relaxation time (τ) shifted to higher values. In addition, CB affected thecure characteristics and after cure relaxation. In the cured compounds, the slope ofrelaxed modulus was steeper at starting time (~0.01 s) and less steep at longer timethan those of the master compound, reaching a considerable set at the end of relaxationwhich was dependent on CB level and size