Volume 16, Issue 4

Two metal acetate-ethanolamine complexes, namely Cu(OAc) 2 (EA) and Zn(OAc) 2 (EA), were synthesized from metal acetates [M(OAc) 2 , where M=Cu and Zn] and ethanolamine (EA). These metal acetate-ethanolamine complexes can be used as catalysts in the preparation of rigid polyurethane (RPUR) foams. Both Cu(OAc) 2 (EA) and Zn(OAc) 2 (EA) were obtained as viscous liquids, which have very weak odor and could be easily dissolved in the starting materials of RPUR foam formulation. The results were compared with RPUR foam prepared from dimethylcyclohexylamine (DMCHA), which is a commercial catalyst with very strong amine odor. Considering the gel time and rise time, Cu(OAc) 2 (EA) had higher catalytic activity than Zn(OAc) 2 (EA) and both metal acetate-ethanolamine complexes had lower catalytic activity than DMCHA. Density and compressive strength of RPUR foam catalyzed by Cu(OAc) 2 (EA) were comparable to that prepared from DMCHA.

This study investigated the effect of the guar gum content on the degradation behavior of the polyester and polyether polyurethane acrylate composites under outdoor soil-burial exposure. Polyurethane acrylates-guar gum composites were characterized before and after soil degradation by Fourier transform infrared spectroscopy (FTIR), mechanical measurements and scanning electron microscopy (SEM). The results showed that the addition of guar gum produces significant improvement in the degradation rate of these composites. The guar gum filler’s susceptibility to humidity and to soil microorganisms resulted in significant chemical and morphological changes in the entire structure of the composite. Guar gum incorporation into the matrix of the crosslinked polyurethane acrylates leads to a significant decrease in the mechanical properties of the composite films after soil burial exposure.

A study about the influence of the impartment of phthalocyanine pigments into elastomeric composites was conducted. Acrylonitrile-butadiene (NBR) and styrene-butadiene (SBR) rubbers crosslinked by either sulfur or dicumyl peroxide were filled with non-toxic flame retardants (Mg(OH) 2 or Al(OH) 3 ) and thermally stable pigments (zinc or chloroaluminum phthalocyanines). Determination of cross-linking degree, mechanical properties, aging coefficient, thermal analysis (TG, DTG, DTA) and flammability tests (oxygen index, combustion in air) were carried out. The addition of the pigments, apart from the impartment of blue or blue-green color to elastomeric composites, in numerous cases improved their mechanical properties, thermal stability, limited flammability and allowed obtaining self-extinguishing materials in atmospheric air.

A series of copolyimides were prepared by thermal imidization of poly(amic acid)s (PAAs) derived from 3,3′,4,4′-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3′,3,4′-biphenyltetracarboxylic dianhydride (a-BPDA), p-phenylenediamine (PDA) and 4,4′-oxydialinine (4,4′-ODA) commonly used for the production of commercial polyimides. The flexible copolyimide films were obtained from that the molar ratio of s-BPDA, a-BPDA, PDA and 4,4′-ODA was 9:1:8:2 (Co-PIs-3), 8:2:9:1 (Co-PIs-5) and 8:2:8:2 (Co-PIs-6). These obtained copolyimide films were characterized by Fourier transform-infrared spectroscopy(FT-IR), wide angle X-ray (WAXD), Thermogravimetric (TG), dynamic mechanical thermal analysis (DMA), thermomechanical analysis (TMA), field-emission scanning electron microscopy (FE-SEM) and mechanical properties measurement. The results showed that three copolyimides remained semi-crystalline and exhibited high glass transition temperature (T g ), high thermal stability, great ultimate tensile strength and low coefficient of thermal expansion (CTE). The Co-PIs-5 had lower crystallinity, lower CTE, greater elongation at break, higher T g and thermal stability and the greater dense extent, compared with Co-PIs-3 and Co-PIs-6. Structure and property relations of the prepared polyimides were also briefly discussed. The results revealed that the copolymerization of s-BPDA/PDA with a small number of 4,4′-ODA/a-BPDA was a useful means for enhancing flexibility without sacrificing low CTE.

The goal of this work was to synthesis a novel aromatic multiamide derivative based on 1H-benzotriazole (PB) as an organic nucleating agent for poly(L-lactic acid) (PLLA), and investigate the effect of PB on the non-isothermal crystallization, melting behavior and thermal decomposition of PLLA. Here, PB was firstly synthesized through 1H-benzotriazole aceto-hydrazide and terephthaloyl chloride, then PB-nucleated PLLA was fabricated via melt-blending technology at various PB concentration from 0.5 wt% to 3 wt%. Finally, the thermal performances were evaluated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The high thermal decomposition temperature of PB indicated that PB possessed possibility as a nucleating agent for PLLA, and the non-isothermal crystallization behavior confirmed the crystallization accelerating effectiveness of PB for PLLA. Upon optimum concentration of 2 wt%, the onset crystallization temperature, the crystallization peak temperature and the non-isothermal crystallization enthalpy increased from 101.4°C, 94.5°C and 0.1 J·g -1 to 121.3°C, 115.8°C and 35.1 J·g -1 , respectively. In addition, the non-isothermal crystallization behavior was also affected by the cooling rate and the final melting temperature. The melting behavior further evidenced the advanced nucleating ability of PB, and the competitive relationship between PB and the heating rate, the nuclear rate and crystal growth rate. Thermal stability measurement showed that PB with a concentration of 1 wt%–2 wt% could slightly improve the thermal stability of PLLA.

Fe 3 O 4 nanoparticles (MNP) were coated with 3-aminopropyltriethoxy-silane (APTES), resulting in anchoring of primary amine groups on the surface of the particles, then four kinds of novel magnetic adsorbents (Fe 3 O 4 @SiO 2 -NH-HCGs) were formed by grafting of different heterocyclic groups (HCG) on amino groups via substitution reaction. These Fe 3 O 4 @SiO 2 -NH-HCGs were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and energy disperse spectroscopy (EDS). The results confirmed the formation of Fe 3 O 4 @SiO 2 -NH-HCGs nanoparticles and the Fe 3 O 4 core possessed superparamagnetism. Batch experiments were performed to evaluate adsorption conditions of Cu 2+ , Hg 2+ , Pb 2+ and Cd 2+ . Under normal temperature and neutral condition, just 20 min, the removal efficiency of any Fe 3 O 4 @SiO 2 -NH-HCGs is more than 96%. In addition, these Fe 3 O 4 @SiO 2 -NH-HCGs have good stability and reusability. Their removal efficiency has no obvious decrease after being used seven times. After the experiments were finished, Fe 3 O 4 @SiO 2 -NH-HCGs were conveniently separated via an external magnetic field due to superparamagnetism. These results indicate that these Fe 3 O 4 @SiO 2 -NH-HCGs are potentially attractive materials for the removal of heavy metal ions from industrial wastewater.

This research was carried out to evaluate the effect of oil palm ash (OPA) on the mechanical and thermal properties of biocomposites. Different compositions of OPA (i.e. 0, 10, 20 and 30 vol%) were introduced to unsaturated polyester (UPE) by using simple casting method with methyl ethyl ketone peroxide (MEKP) as a hardener. The specimens were prepared based on ASTM D5083 standards for tensile testing. From the results, it was found that the mechanical properties of UPE/OPA composites were improved in modulus with increasing the OPA content. The physical properties of UPE/OPA were also investigated where the density of biocomposites decrease with increasing OPA while the water absorption of UPE/OPA increase with increasing OPA. The thermal and morphological characterization of the UPE/OPA composites have been done using TGA, DSC and SEM.

In this study, the effect of modified Hestrin Schramm (HS) medium supplemented with different carbon sources viz., glucose, fructose, galactose and lactic acid on the yield and physicochemical properties of bacterial cellulose (BC) produced from Gluconacetobacter xylinus strain MTCC 7795 in shake flask culture conditions was investigated. Growth studies indicated that all carbon sources supported the growth of bacteria, though specific growth rate and doubling time differs. Fructose gave the highest cellulose yield of 7.72 mg/ml after 130 h of fermentation, while yield in glucose and galactose supplemented medium were 4.49 mg/ml and 3.38 mg/ml, respectively. X-ray powder diffraction (XRD) analysis revealed that all BC samples were amorphous in comparison to commercial cellulose. Fourier transform infrared (FTIR) spectroscopic investigations of bacterial cellulose (BC) samples affirm the purity of the cellulose produced. No significant variations in physicochemical properties of cellulose samples produced with different carbon sources were observed. This study for the first time has investigated the effect of carbon sources on physicochemical properties of bacterial cellulose produced by G. xylinus MTCC 7795 and provides a strategy for economical production of BC with anticipated application in therapeutics and tissue engineering.

The effect of the angle of dual slots on an air flow field in melt blowing was researched via numerical simulation. Through establishing the geometric model of air flow field in melt blowing with dual slots, meshing, designating the boundary conditions and their parameters and numerical simulation, the result illustrates the influence of the angle of dual slots on the variations of air velocity, pressure and temperature distributions. Higher peak values of air velocity, pressure and temperature are obtained with larger angles of dual slots near the die, while only a few differences of these parameters are detected away from the die. Our results demonstrate the angle of 70° is the appropriate one that can produce the finest fibers.

Dissipative particle dynamics simulations are performed to study the self-assembly of rod-coil (RC) diblock copolymers confined in a slit with two coil-selective surfaces. The effect of rod length and slit thickness on the assembly structure is investigated. A morphological phase diagram as a function of slit thickness and rod length is presented. We observe several ordered structures, such as perpendicular cylinders, parallel cylinders, and puck-shaped structure. In the assembly structures, long-range rod-rod orientational order is observed when the rod length exceeds a critical rod length. Our results show that the coil-selective slit influences the assembly structure as well as the rod orientation of RC diblock copolymers.