Flexural behavior of unidirectional polyethylene–glass fiber–PMMA hybrid composites

Unidirectional hybrid laminates based on glass fibers (GF) and high performance polyethylene fibers (PEF) were prepared with a partially polymerized methyl methacrylate (MMA) matrix at room temperature followed by heating at 55°C for the stipulated time (well below the softening point of PEF). The ultimate flexural strength (UFS), flexural modulus (FM) and interlaminar shear strength (ILSS) of the composites were determined and analyzed. An interesting observation of the study was the change in flexural behavior, which was largely dependent on the position of GF and PEF ply/plies in the compression and tension sides. When the ply/plies of PEF were at the tension side, the UFS and FM showed a higher value than that when GF plies were in the tension side of the hybrid composites. The ILSS also follows the same trend regarding the position of the GF and PEF plies.     

Thermal investigations of the calcium salts of monocarboxylic aliphatic fatty acids

Calcium salts of acetic and mono, di and trichloroacetic acids were investigated with respect to their dehydration and decarboxylation, using a derivatograph. A phase transition was noticed only in the case of calcium acetate. Effects of crucible and diluent on the thermal behaviour of the above salts were also studied. The decomposition products were investigated qualitatively, and from these gaseous products and also from the residue after pyrolysis the probable mechanisms of decompositions have been suggested. Activation energies for the decarboxylation processes were evaluated from the TG curves.

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Zusammenfassung Die Calciumsalze von EssigsÄure sowie von Mono-, Di- und TrichloressigsÄure wurden mittels eines Derivatographen hinsichtlich ihrer Dehydratisierung und Decarboxylierung untersucht. Ein Phasenübergang wurde nur im Falle des Calciumacetats beobachtet. Der Effekt des Tiegels und des Verdünners auf das thermische Verhalten obiger Salze wurde ebenfalls untersucht. Die Zersetzungsprodukte wurden qualitativ geprüft und aus diesen gasförmigen Produkten sowie aus ihren Pyrolyseresten wurde ein wahrscheinlicher Zersetzungsmechanismus vorgeschlagen. Die Aktivierungsenergien der DecarboxylierungsvorgÄnge wurden aus den TG-Kurven ermittelt.

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Résumé La déhydratation et la décarboxylation des sels de calcium des acides acétique, mono, di et trichloroacétique ont été étudiées à l'aide d'un Derivatograph. Seul l'acétate de calcium présente une transition de phase. Les effets respectifs du creuset et du diluant sur le comportement thermique de ces sels ont également été suivis. Les produits de décomposition ont été analysés qualitativement. D'après la nature des gaz émis et celle des résidus de pyrolyse, un mécanisme est proposé pour ces décompositions. Les énergies d'activation des réactions de décarboxylation sont calculées à partir des courbes TG.

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The authors express their most grateful thanks to the Council of Scientific and Industrial Research, New Delhi, for financial assistance.     

A theoretical study of the reaction of SiH2 with C2H2 and C2D2

Potential energy surfaces of the reaction of SiH₂ and C₂H₂ (and C₂D₂) have been calculated by means of ab initio molecular orbital theory at the QCISD/6-311G++(2df, 2p)//MP2/6-31G(d, p) level with corrections for the triple excitations to the QCISD energies. The barrier heights for the two reaction channels of the adduct, thus calculated, were further utilized for the dynamical calculation of the rate constants in the framework of quantum statistical Rice-Ramsperger-Kassel theory. Contributions of the rate constants of the various pathways to the total rate constant (K_T) for the disappearance of the reactants are critically examined and compared with experiment. The pressure dependence of K_T(C₂H₂) is primarily due to the formation of silirene. K_T(C₂D₂) is consistently higher than K_T(C₂H₂). The standard heat of formation of silirene is predicted to be 72.1 ± 3 kcal/mol. Rearrangement of silirene to vinylsilylene requires an activation energy smaller than that to silylacetylene.     

A potential role for protein tyrosine phosphatase inhibition by a RuIII-edta complex (edta = ethylenediaminetetraacetate) in its biological activity

[RuIII(edta)(OH2/OH)]1-/2- (edta = ethylenediaminetetraacetate) inhibits protein tyrosine phosphatase (PTP) at physiological pH values in a mechanism that involves binding of the Cys residue of the catalytic domain of the enzyme and similar interactions may be important in the anti-cancer properties of the active forms of many Ru pro-drugs.     

Synthesis,Characterization, and Crystal Structure of the New Schiff‐Bases derived from 1,2,4‐Triazole and the Structure of [(PPh3)2Cu(AMTT)]NO3·EtOH (AMTT = 4‐Amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione)

The reactions of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, L1 ) with 2‐thiophen carbaldehyde, salicylaldehyde and 2‐nitrobenzaldehyde in methanol led to the corresponding Schiff‐bases ( L1a‐c ). The reaction of L1 with [(PPh₃)₂Cu]NO₃ in ethanol gave the ionic complex [(PPh₃)₂Cu(L1)]NO₃·EtOH ( 2 ) All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for L1a at 20 °C: space group P2₁/n with a = 439.6(2), b = 2074.0(9), c = 1112.8(4) pm, β = 93.51(3)°, Z = 4, R₁ = 0.0406, L1b at ?80 °C: space group P2₁/n with a = 1268.9(2), b = 739.3(1), c = 1272.5(1) pm, β = 117.97(1)°, Z = 4, R₁ = 0.0361, L1c at ?80 °C: space group P2₁/n with a = 847.8(1), b = 1502.9(2), c = 981.5(2) pm, β = 110.34(1)°, Z = 4, R₁ = 0.0376 and for 2 at ?80 °C: space group with a = 1247.8(1), b = 1270.3(1), c = 1387.5(1) pm, α = 84.32(1)°, β = 84.71(1)°, γ = 63.12(1)°, Z = 2, R₁ = 0.0539.