Bioplastic Production from Eucheuma Cottoni

Plastic waste has become a global problem because it causes environmental pollution. This is because plastic waste is difficult to decompose. There have been numerous solutions proposed, one of which is theuse of bioplastics. In this research, the bioplastics were made from third- generation biomass, namely the eucheuma cottoni. Eucheuma cottoni is contains biopolymer carrageenan, a carbohydrate with unit structures consisting of d-galactose and 3,6 anhydrogalactose with glycosidic bonds. Goal this research is study the effects of sorbitol plasticizer content and bioplastics manufacturing temperature on bioplastics, tensile strength, elongation, and biodegradation rate. The bioplastics were made by extracting 10 grams of eucheuma cottoni powder in 200 ml of distilled water. The algae extract was added with sorbitol (plasticizer) and heated at various temperatures from 45°C until 60°C. The mixture was poured into a mold tin and dried in the oven to a constant weight. The resulting bioplastics were then characterized to determine the tensile strength and biodegradation rate. The results showed that increasing the plasticizer content from 3.5% reduced the tensile strength, however, it increased the elongation and biodegradation rate. The optimal plasticizer content was 4% with a tensile strength value of 4.8309 Mpa, elongation of 24.1548%, and biodegradation rate of 26.9392%. The temperature variable showed that increasing the temperature of making bioplastics could reduce tensile strength, increase elongation and biodegradation rate of bioplastics. The optimum temperature for making bioplastics at 45oC obtained a tensile strength of6.28 Mpa and an elongation of 20.67%. The biodegradation rate was 39.6665%, and the best sorbitol content was received at 4%.

Thermal Properties of Plasticized Cellulose Acetate and Its β-Relaxation Phenomenon

Cellulose acetate (CA), an organic ester, is a biobased polymer which exhibits good mechanical properties (e.g., high Young’s modulus and tensile strength). In recent decades, there has been significant work done to verify the thermal and thermomechanical behaviors of raw and plasticized cellulose acetate. In this study, the thermomechanical properties of plasticized cellulose acetate—especially its ββ-relaxation and activation energy—were investigated. The general thermal behavior was analyzed and compared with theoretical models. The study’s findings could be of special interest, due to the known ββ-relaxation dependency of some polymers regarding mechanical properties—which could also be the case for cellulose acetate. However, this would require further investigation. The concentration of the plasticizers—glycerol triacetate (GTA) and triethyl citrate (TEC)—used in CA ranged from 15 to 40 wt%. DMTA measurements at varying frequencies were performed, and the activation energies of each relaxation were assessed. Increasing plasticizer content first led to a shift in ββ-relaxation temperature to highervalues, then reached a maximum before declining again at higher concentrations. Furthermore, the activation energy of the ββ-relaxation constantly rose with increases in plasticizer content. The trend in the ββ-relaxation temperature of the plasticized CA could be interpreted as a change in the predominant phase of the overlapping ββ-relaxation of the CA itself and the αα′-relaxation of the plasticizer—which appears in the same temperature range. The plasticizer used (GTA) demonstrated a higher plasticization efficiency than TEC. The efficiencies of both plasticizers declined with increasing plasticizer content. Additionally, both plasticizers hit the saturation point (in CA) at the lowest studied concentration (15 wt%).

Effect of polycarboxylate superplasticizer on fluidity and rheology of cement slurry containing silica fume

The effect of polycarboxylate superplasticizer on the fluidity and rheology of cement - silica fume - water paste was investigated. The changes of dispersion degree, yield stress and plastic viscosity of paste with different superplasticizer content were analyzed. The results show that the rheological properties of paste with different superplasticizer content conform to Herschel-Bulkley model. The shear thinning of the slurry is manifested as a typical yielding pseudoplastic fluid characteristic. When the content of superplasticizer is less than 1.0%, the plastic viscosity and yield stress decrease and the fluidity increase with the increase of plasticizer content. When the content of superplasticizer is more than 1.0%, the yield stress decreases slightly and the plastic viscosity increases with the increase of plasticizer content. The fluidity decreases with the increase of yield stress, and there is a good correlation between them.