Modification of poly (acrylamide-co-acrylic acid) superabsorbent hydrogels with varying starch concentration (1-3%) via simultaneous gamma radiation have been carried out. The structure and morphology of copolymers were characterization by Fourier transform infra red spectroscopy and scanning electron microscopy. The gel fraction, swelling kinetics and the equilibrium degree of swelling (EDS) of the hydrogels were studied. It was found that the an increase in the starch content present in the hydrogels (1-3%) and with increase irradiation dose from 10 kGy up to 30 kGy, the swelling ratio decreased from 250-100 g/g. Incorporation of 1% starch increases the EDS of the hydrogels up 350 g/g. Under maximum conditions, poly(AAm-co-AA)-starch hydrogels with high gel fraction (~93%) was prepared from aqueous solution containing 5% AAm, 15% acrylic acid and 0-3% starch. The hydrogels were sensitive against salts solution.
Crosslinked PEO hydrogel containing chitosan for wound dressing has been prepared by gamma radiation technique. Chitosan solutions with different concentration (0.5-2% w/v) have been blended with 5% aqueous solution of PEO and irradiated at the doses 20-40 kGy by gamma rays. The copolymers were characterized by Fourier transform infra red spectroscopy and their physico-chemical properties of hydrogels were evaluated in terms of gel fraction, swelling ratio, elongation at break and antimicrobial activities. It was found that under maximum condition of incorporation 1% chitosan with irradiation dose of 20 kGy, PEO-chitosan hydrogels with high gel fraction (85%), swelling ratio (10 g/g) and elongation at break (145%) were obtained. The examination of the microbe penetration shows that the prepared hydrogels can be considered as a good barrier against microbes. Thus, PEO-chitosan hydrogel showed satisfactory properties for use as a wound dressing.
Hydrogels are ideal biomaterials owing to their unique network structure that facilitates considerable hydrophilicity and biocompatibility. At the same time, hydrogels also possess soft physical properties when combined with living tissue. In this study, metformin hydrogen chloride (metformin HCl)-loaded stimuli-responsive poly(N-isopropylacrylamide) (pNIPAAm) -chitosanpolyvinyl alcohol (PVA) hydrogels were synthesized through a freezing and thawing procedure and subsequently subjected to gamma irradiation at room temperature. The gel content and the water absorption capacity of the synthesized hydrogels were analyzed. The polymer interaction in the matrix was observed by Fourier transform infrared spectroscopy, and the release of metformin HCl was studied in different pHs and temperatures. The hydrogels had 85% of the gel content and 373% of the water absorption capacity after 24 h of water immersion. The metformin HCl-loaded (pNIPAAm-chitosan-PVA) hydrogels demonstrated a sustained drug release profile over 7 h. The drug release exhibited pH-dependent and temperature-dependent behavior. The developed hydrogels showed good metformin HCl release ability at pH 3 and pH 6.86 at the temperature of 37 o C. The results showed that pNIPAAm-chitosan-PVA hydrogels could be employed for controlled drug release of metformin HCl.
The beam stability factor (CL) is applied in construction practices to adjust the reference bending design value (Fb) of sawn lumber to consider the lateral-torsional buckling. Bending tests were carried out on 272 specimens of four wood species, namely, red meranti (Shorea sp.), mahogany (Swietenia sp.), pine (Pinus sp.), and agathis (Agathis sp.), to analyze a simply supported beam subjected to concentrated loads at several points. The empirical CL value is a ratio of the modulus of rupture (SR) of a specimen to the average SR of the standard-size specimens. The non-linear regression estimated the Euler buckling coefficient for sawn lumber beam (KbE) in this study as 0.413, with 5% lower and 5% upper values of 0.338 and 0.488. Applying the 2.74 factor, which represents an approximately 5% lower exclusion value on the pure bending modulus of elasticity (Emin) and a factor of safety, the adjusted Euler buckling coefficient (KbE′) value for a timber beam was 1.13 (0.92–1.34), which is within the range approved by the NDS (KbE′ = 1.20). This study harmonizes the NDS design practices of CL computation with the empirical results. Because agathis has the lowest ductility (μ), most natural defects (smallest strength ratio, S), and highest E/SR ratio, the agathis beam did not twist during the bending test; instead, it failed before twisting could occur, indicating inelastic material failure. Meanwhile the other specimens (pinus, mahogany, and red meranti), which have smaller E/SR ratio, higher ductility, and less natural defects, tended to fail because of lesser beam stability. This phenomenon resulted in the CL curve of agathis being the highest among the others. The CL value is mathematically related to the beam slenderness ratio (RB) and the E/SR ratio. Because the strength ratio (S) and ductility ratio (μ) have significant inverse correlations with the E/SR ratio, they are correlated with the CL value. Applying the CL value to adjust the characteristic bending strength is safe and reliable, as less than 5% of the specimens’ SR data points lie below the curve of the adjusted characteristics values.
Dalam kerangka mendapatkan hidrogel dengan kemampuan menyerap airyang relatif tinggi, telah dilakukan sintesis hidrogel superabsorben (HSA) berbasis asam akrilatmenggunakan teknik radiasi. Satu seri larutan asam akrilat dengan derajat netralisasi (Dn) 0;0,20; 0,40; 0,60; 0,80 dan 1 masing-masing diiradiasi sinar gamma pada dosis10 kGy (lajudosis 5 kGy/j). Pengaruh derajat netralisasi terhadap nisbah pengembung hidrogel dipelajari.Sifat termal hidrogel diukur menggunakan Differential scanning calorymetry (DSC). Perubahanstruktur kimia hidrogel diukur menggunakan Fourier transform infra red (FTIR), dan morfologihidrogel diobservasi menggunakan Scanning electron microscope (SEM). Hasil eveluasimenunjukan bahwa pada kondisi optimum (Dn=0,80, 10 kGy, 20 menit), hidrogelmenunjukkan kemampuan menyerap air yang relatif tinggi (~600 g/g). Hasil pengukuranDSC mengkonfirmasi kemungkinan terbentuknya jenis produk akhir hasil iradiasi asamakrilat. Spektra FTIR menunjang bahwa reaksi polimerisasi asam akrilat melalui ikatanrangkap dua dalam struktur molekul asam akrilat. Hasil pengujian SEM menunjukkan bahwahidtogel berpori ukuran makro.Kata kunci : Hidrogel, superabsorben, asam akrilat, irradiasi, derajat netralisasi.
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