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Hydrogel based on kappa carrageenan extracted from Kappaphycus alvarezii was synthesized by film immersion in glutaraldehyde solution (GA 4% w/w) as crosslinker for 2 min and then followed by thermal curing at 110 ^oC for 25 min. The obtained crosslinked films were washed using ethanol to remove the unreacted crosslinker and finally dried to constant weight. The aim of this research was to investigate the effect of carrageenan recovery method on the prepared hydrogel properties. The method of carrageenan extraction strongly determined the swelling properties of crosslinked carrageenan. Hydrogel obtained from alkali treated carrageenan showed higher swelling ability compared to hydrogel from nonalkali treated carrageenan. Hydrogel from alkali treated carrageenan showed the ability of sensitive to pH media. Swelling degree of alkali treated carrageenan based hydrogels increased by increasing pH solution from about 5 g/g for neutral pH to 20 g/g for pH~13.

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Cassava starch-grafted polyacrylamide (CS-g-PAM) hydrogels were synthesized using a microwave-assisted method and K2O8S2 (KPS) as an initiator. In this study, we studied the influence of the amount of acrylamide and irradiation time on the properties of CS-g-PAM. The characterization of CS-g-PAM obtained was shown by Fourier-transform infrared (FTIR) and Scanning Electron Microscope (SEM) analysis. To predict the behavior of the samples under reservoir conditions, the properties of CS-g-PAM, such as swelling ratio, water-solubility, and viscosity were determined as a function of temperature, salt concentration, and aging time. The FTIR spectra and SEM analysis of the CS-g-PAM confirmed that the polyacrylamide chains were successfully grafted onto the cassava starch backbone. The results showed that the increasing amount of acrylamide and the longer irradiation time improved the properties of CS-g-PAM. Preparation of CS-g-PAM with 10 g of acrylamide and 180 s of irradiation time resulted in the highest grafting percentage and water solubility, which was 1565.53 and 96.06%, respectively. Its viscosity also exceeded 97% after 15 days of aging. The results showed that CS-g-PAM expressed properties such as good thickening, temperature resistance, and salt resistance according to reservoir conditions. This finding indicated that CS-g-PAM has good potential for oil recovery applications.

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Poly(lactic acid) or PLA bio‐composite is prepared by filling with micro‐graphite via solution blending. The micro‐graphite loading is varied from 0–15 wt%. The objectives of this research are to investigate the influence of micro‐graphite loading on PLA bio‐composite, on the viscoelasticity and thermal stability. The viscoelasticity behavior exhibits a considerable dependence on the melt properties of the PLA/micro‐graphite bio‐composites on the percentage micro‐graphite. The complex viscosity |η*|, storage modulus (G’), and loss modulus (G″) tend to improve with increasing micro‐graphite loading. Thermogravimetric analyses indicate that the micro‐graphite slightly stabilizes the PLA. The decomposition reaction is shifted to a higher temperature in the range 7–9 °C. This reaction leads to the loss of volatile byproducts, which occur at temperatures higher than 310 °C. It means far from the melt processing conditions. The differential scanning calorimetry thermogram shows that the glass transition temperature (Tg) and the melting temperature are close to that of neat PLA with changes only around 2–4 °C.

Abstract. Taro starch, cassava starch and also their modified were prepared as a backbone of grafted flocculants. These flocculants were synthesized by combining the properties of synthetic and natural polymer via the 'grafting to' method that separated into two stages. The first stage was synthesizing of nonterminated polyacrylamide (nt-PAM) and then followed by the second stage grafting of the nt-PAM onto several kinds of starch. The intrinsic viscosity (K) and average molecular weight (Mv) of starches-g-PAM were observed and their molecular structures were analyzed by using Fourier Transform Infra-Red (FTIR). Finally, the obtained flocculants were tested to evaluate their performance for the treatment of the simulated water turbidity containing 10 g of kaolin in 1000 ml of aquadest. The results showed that all the grafted flocculants can be good comparable to some commercial organic flocculants. The percentages of the water turbidity removal for each of backbones are 93.6% (taro starch), 91.2% (cassava starch), 95.3% (modified taro starch) and 94.1% (modified cassava starch). It can be highlighted that the modified taro starch exhibited the best performance in water turbidity removal up to 95%.

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