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Self-healing of polymeric material using microcapsules has been developed to repair microcracks within the materials. The self-healing character is reflected from the curing behavior of the material. In this work, curing study of alkyd/epoxy blend was carried out by replacing part of amine hardener with alkyd in the epoxy formulation. The inclusion of alkyd in the epoxy blend resulted in higher degree of curing and higher thermal stability compared to the alkyd-free blend, as evidenced from higher heat of reaction values of differential scanning calorimetry and maximum degradation temperature at 379°C, respectively. Self-healing reaction of epoxy coating as evaluated by Fourier-transform spectroscopy revealed that the 914 cm−1 peak attributed to C–O–C of epoxy has decreased, as the epoxide group was consumed in the reaction. Appearance of a new peak at 1631–1632 cm−1 in the cured coating confirmed that the epoxide has reacted with the carboxylic acid group of alkyd to form ester. [ABSTRACT FROM AUTHOR]

One of the approaches to prolong the service lifespan of polymeric material is the development of self-healing ability by means of embedded microcapsules containing a healing agent. In this work, poly(melamine-urea-formaldehyde) (PMUF) microcapsules containing a palm oil-based alkyd were produced by polymerization of melamine resin, urea and formaldehyde that encapsulated droplets of the suspended alkyd particles. A series of spherical and free-flowing microcapsules were obtained. The chemical properties of core and shell materials were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). Differential scanning calorimetry (DSC) analysis showed a glass transition around -15 °C due to the alkyd, and a melting temperature at around 200 °C due to the shell. Thermogravimetric analysis (TGA) results showed that the core and shell thermally degraded within the temperature range of 200-600 °C. Field emission scanning electron microscope (FESEM) examination of the ruptured microcapsule showed smooth inner and rough outer surfaces of the shell. Flexural strength and microhardness (Vickers) of the cured epoxy compound were not affected with the incorporation of 1%-3% of the microcapsules. The viability of the healing reactions was demonstrated by blending small amounts of alkyd with epoxy and hardener at different ratios. The blends could readily cure to non-sticky hard solids at room temperature and the reactions could be verified by ATR-FTIR. [ABSTRACT FROM AUTHOR]

Preparation of microcapsules of poly(urea-formaldehyde) (PUF) and melamine-modified PUF (PUMF) shells that encapsulated a core of palm oil-based alkyd resin was described. Ethylene maleic anhydride (EMA) was used as emulsifier. The effects of core-shell weight ratio on microcapsules size and surface morphology were studied. The microcapsules obtained were inspected using digital microscope and field emission scanning electron microscope (FESEM) to study the formation of microcapsules and their surface morphology. The core and shell content was verified using differential scanning calorimetry (DSC) and attentuated total reflectance fourier-transformed infrared (ATR-FTIR). Thermogravimetric analysis (TGA) shown that the microcapsules have different degradation rates of core and shell thus reconfirmed the formation of microcapsules. The resultant microcapsules appear as white-yellowish and free-flowing spherical particles, having a rough, non-porous shell which was formed by PUF and PUMF nanoparticles. The microcapsules have their diameters ranging from 150-500 microns, and they contain 87-90% of the alkyd as core and 10-13% of shell by weight. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to modify guar gum (GG) into guar gum acetate (GGA) and phthaloyl guar gum (PHGG) by transesterification and phthaloylation, respectively. Design/methodology/approach: GG has been modified into GGA through transesterification reaction between GG and vinyl acetate and PHGG through esterification reaction with phthalic anhydride. The modified GG was characterized by solubility test, Fourier-transform infra-red (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, X-ray diffractometry (XRD) and thermogravimetric analysis. Swelling properties of GGA and PHGG hydrogels in water were evaluated. Findings: These two types of modified GG have better solubility such as in dimethyl sulfoxide and N,N-dimethylformamide but no true organosolubility was achieved. The modifications were confirmed through FTIR with new absorption peaks at 1,733 cm−1 for GGA and 1,709 cm−1 for PHGG coupled with observed substitution peaks at 1.80 to 2.20 ppm and 7.40 to 7.90 ppm, respectively, from 1H NMR spectroscopies. XRD revealed both GGA and PHGG are less crystalline than native GG. GGA was found to be more thermally stable than native GG, whereas PHGG was slightly less thermally stable than native GG. The swelling property in distilled water for native GG, PHGG and GGA was 918.43 ± 46.62%, 537.04 ± 2.87% and 393.04 ± 13.42%, respectively. Research limitations/implications: The GGA and PHGG hydrogels are expected to be useful for biomedical fields such as tissue engineering and drug-delivery. Originality/value: Modifications of native GG into GGA using vinyl acetate and PHGG using phthalic anhydride are novel. [ABSTRACT FROM AUTHOR]

Cellulose is widely appreciated amongst polymer scientists as the most abundant and cost-effective natural polysaccharide. Nonetheless, the non-dissolving property of cellulose has narrowed its potential from a broader range of applications. Hence, modification has to be made in order to improve its solubility. In this study, a simple, robust and rapid transesterification method using vinyl acetate was carried out by acetylating microcrystalline cellulose (MCC) to obtain cellulose acetate (CA). The solubility test showed an improvement of organosolubility for the modified cellulose. Series of CA powders at five different degrees of substitution (DS) were prepared by varying the composition of cellulose to vinyl acetate molar ratios. Successful acetylation of cellulose was confirmed through Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopies. Physicochemical traits were studied by using X-ray diffraction (XRD) and thermogravimetric analysis (TGA). XRD and TGA measurements revealed that CA powders of different DS were less crystalline and more thermally stable than its native form. The CA powders were turned into quasi-solid polymer electrolytes (PEs) and the highest ionic conductivity reported in this study was 7.31 × 10−3 S cm−1 with incorporation of 20 wt.% sodium iodide (NaI) salt. Rheology study was carried out to investigate the mechanical strength of the gels. Quasi-solid PEs were prepared for potential dye-sensitized solar cells (DSSCs) application. [ABSTRACT FROM AUTHOR]

Cellulose was isolated from waste coconut husk (Cocos nucifera) via alkali and single bleaching treatment. The isolated cellulose (CH-A-1B) was found to have residual lignin which imparts amorphous character to the polymer matrix as confirmed by X-ray diffraction analysis (XRD). Fourier transform infrared (FTIR) peak at 1507 cm−1 confirmed the presence of lignin and the appearance of three new peaks at 1320, 1416, and 1595 cm−1 showed successful attachment of carboxymethyl group onto the cellulose backbone. Carboxymethylation of cellulose from CH-A-1B produced carboxymethyl cellulose (CMC) with lower crystallinity compared to that of the double bleaching treatment cellulose (CH-A-2B). The CMC film prepared by solvent-casting method from CH-A-1B using 38 wt% NaOH possessed the highest conductivity of σ = 4.82 × 10−4 mS cm−1. The electrochemical properties of the CMC polymer electrolyte and the degree of crystallinity of the polymer matrix were found to be influenced by the amount of lignin content which acts as a natural plasticizer. [ABSTRACT FROM AUTHOR]

The original version of this article unfortunately contained many mistakes with regard to some mathematical expressions and to Tables 3 & 5. [ABSTRACT FROM AUTHOR]