Sa-Ad Riyajan

Green natural rubber-g-modified starch for controlling urea release

The hydrophilicity of natural rubber (NR) was improved by grafting with modified cassava starch (ST) (NR-g-ST) by using potassium persulfate (K2S2O8) as a catalyst. The modified ST was added to NR latex in the presence of Terric16A16 as a non-ionic surfactant at 60 °C for 3 h and cast film on a glass plate to obtain NR-g-ST. The chemical structure of NR-g-ST was confirmed by FTIR. The swelling ratio of NR-g-ST was investigated in water and results showed that the swelling ratio of the modified NR decreased as function of ST. In addition, the tensile strength of the modified NR in the presence of modified ST at 50 phr was the highest value. Also, the thermal stability modified NR-g-ST was higher than of NR/ST blend confirmed by TGA. Finally, the NR-g-ST was used a polymer membrane for controlling urea fertilizer and it easily degraded in soil. This product with good controlled-release and water-retention could be especially useful in agricultural and horticultural applications.

Effect of chitosan content on gel content of epoxized natural rubber grafted with chitosan in latex form

The epoxidized natural rubber (ENR) latex-g-chitosan (ENR-g-chitosan) was prepared in latex form using potassium persulphate as an initiator. Firstly, the reduction in molecular weight of chitosan was subjected to the addition of K2S2O8 at 70 °C for 15 min. The structure of the modified chitosan was characterized by ATR-FTIR. Secondarily, the influence of chitosan contents, reaction time, and temperature and K2S2O8 concentrations on the gel content of the modified ENR was investigated. The chemical structure of the ENR-g-chitosan was confirmed by (1)H-NMR and ATR-FTIR. The ether linkage of the ENR-g-chitosan was conformed at 1154 an 1089 cm(-1) by ATR-FTIR and 3.60 ppm by (1)H-NMR. The gel content of ENR-g-chitosan at 5% chitosan showed the highest value compared with other samples. But when chitosan increased from 5% to 10% or 20%, the gel content of ENR-g-chitosan dramatically decreased. The ENR-g-chitosan showed good thermal resistance due to incorporation of chitosan. The morphology of ENR-g-chitosan particle showed the core-shell structure observed by TEM. The optimum condition of grafting ENR with chitosan was found at 65°C for 3h of reaction time, ratio of ENR/chitosan at 9:1.

Synthesis and properties of carrageenan grafted copolymer with poly(vinyl alcohol)

The aim of this work was to prepare a carrageenan-g-poly(vinyl alcohol) (CG-g-PVA) polymer using potassium persulphate as an initiator. The effect of different ratios of the polymer blends on the parameters of the grafted polymer was investigated. The grafting ratio decreased with an increase of the CG content in the graft copolymer. The resulting CG-g-PVA was characterized by ATR-FTIR, tensile strength, elongation at break, swelling ratio, contact angle and biodegradation in soil. From the ATR-FTIR the 3,6-anhydride-galactose of the CG showed a peak at 927 cm(-1) that was absent in the CG-g-PVA and the ether linkage of PVA-g-CG between the hydroxyl group of PVA and the 3,6-anhydride-galactose of CG showed a peak at 1089 cm(-1) in the graft copolymer. The tensile strength and elongation at break decreased with an increase of the CG due to its phase separation. The highest tensile strength was observed at 2:8 CG/PVA. In addition, the swelling ratio decreased and the contact angle increased as a function of the increase of the CG in the grafted copolymer. The best ratio of CG-g-PVA was 2:8 CG/PVA. This graft copolymer was easily biodegraded in natural soil.

Physical properties of polymer composite: Natural rubber glove waste/polystyrene foam waste/cellulose

Abstract The polymer composite was prepared from the wastes of natural rubber glove (NRG) and polystyrene foam (PSF) blended with cellulose from sugar cane leaves via the laminate method. The NRG and PSF were firstly dispersed in toluene under continuous stirring. Then, maleic anhydride (MA) was added into the mixture. Effects of blend ratio and of MA content (0.5–15%, w/w) on physical properties of the polymer composite were investigated. The toluene resistance of the polymer blend was improved after adding MA and cellulose. The highest toluene resistance was achieved when using 12% cellulose. The chemical reactions of MA with polymer blend and with composite were confirmed by ATR-FTIR. The hardness of the polymer blend and composite increased as a function of PSF. In addition, their impact strength increased with increasing NRG and cellulose contents.

Preparation and properties of a hydrogel of maleated poly(vinyl alcohol) (PVAM) grafted with cassava starch.

A novel pH-sensitive graft copolymer (PVAM-g-CSt) was synthesized from maleated poly(vinyl alcohol) (PVAM) and cassava starch (CSt) through a grafting reaction using potassium persulfate as a thermal initiator. The chemical structure of the PVAM-g-CSt was revealed by FTIR and ether linkage of the graft copolymer was observed at 1089 cm(-1). The degree of grafting of the copolymer was found to range between 40 and 82%, depending on the PVAM/CSt ratio. The highest tensile strength was found at a ratio of 9:1 PVAM/CSt. In addition, the swelling ratio in water increased with increasing proportions of CSt in the PVAM-g-CSt due to the decrease in the degree of grafting. The resulting hydrogel exhibits good pH sensitivity in different pH mediums. The graft copolymer easily degraded in natural soil, especially at high proportions of CSt in the blend.

Characterization of Modified Bagasse and Investigation Properties of Its Novel Composite

Bagasse was modified with sodium hydroxide and silane, and the obtained three polymer composite types, namely natural fiber, sugarcane bagasse, and plaster were procured by the two-roll mill method. The characterization of the modified sugarcane bagasse was achieved with attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The results show that the presence of Si–CH3 group occurred on the bagasse surface after chemical modification. Adhesion force of cellulose changes after chemical treatment was observed from AFM. The optimum cure time (tc90) and torque of the natural fiber/plaster increased with increasing plaster loading in the composite. The modulus of the resulting composite increased with both plaster and bagasse but the tensile strength and elongation-at-break of the composite decreased as a function of plaster sugarcane bagasse. The polymer composite possesses the best properties at 5 part per hundred rubber (phr) bagasse loading and 30 phr plaster.

Activation Energy and Thermodynamic Parameters of Cyclization in Purified Natural Rubber Latex Using a Trimethyl Silyl Triflate

The property of natural rubber (NR) is more interesting, except for some properties which need to improve. The cyclization reaction is an interesting reaction for modified NR to thermoplastic elastomer. The kinetic cyclization of deproteinized natural rubber (DPNR) or purified NR latex effectively performed in latex phase by using trimethylsilyl-trifluoromethane sulphonate or trimethyl silyl triflate (TMSOTF) is studied at various temperatures and times. The cyclized products are confirmed by NMR spectroscopies including one and 2D NMR. The kinetic of cyclization is investigated. It is found that the degree of cyclization in DPNR is a function of cyclization conditions. The rate constant (k) is 200 (s-1) at 100°C based on 95% of regression and the activation energy of cyclization in DPNR latex is 147.66kJ/mol. Some thermodynamic parameters: enthalpy, entropy, and free energy activation of 144.6kJ/mole, -269.11J/mole, and 246.9kJ/mole, respectively, are obtained for the cyclization of DPNR. The kinetic and thermodynamic parameters of cyclization obtained from this study indicate that an increase in the process temperature would increase the rate of cyclization formation.