Studies on thermal, mechanical and morphological behaviour of caprolactam blocked methylenediphenyl diisocyanate toughened bismaleimide modified epoxy matrices

Diglycidyl ether of bisphenol A epoxy resin (DGEBA, LY 556) was toughened with 5%, 10% and 15% (by wt) of caprolactam blocked methylenediphenyl diisocyanate (CMDI) using 4,4′-diaminodiphenylmethane (DDM) as curing agent. The toughened epoxy resin was further modified with chemical modifier N,N′-bismaleimido-4,4′-diphenylmethane (BMI). Caprolactam blocked methylenediphenyl diisocyanate was synthesized by the reaction of caprolactam with methylenediphenyl diisocyanate in presence of carbon tetrachloride under nitrogen atmosphere. Thermal properties of the developed matrices were characterized by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), heat distortion temperature (HDT) and dynamic mechanical analysis (DMA). Mechanical properties like tensile strength, flexural strength and impact strength were tested as per ASTM standards. The glass transition temperature (T_g) and thermal stability were decreased with increase in the percentage incorporation of CMDI. The thermomechanical properties of caprolactam blocked methylenediphenyl diisocyanate toughened epoxy resin were increased by increasing the percentage incorporation of bismaleimide. The values of impact strength for epoxy resin were increased with increase in the percentage concentration of CMDI. The homogeneous morphology of CMDI toughened epoxy resin and bismaleimide modified CMDI toughened epoxy resin system were ascertained from scanning electron microscope (SEM).     

Fe3O4‐Methylene diphenyl diisocyanate‐guanidine (Fe3O4–4,4′‐MDI‐Gn): A novel superparamagnetic powerful basic and recyclable nanocatalyst as an efficient heterogeneous catalyst for the Knoevenagel condensation and tandem Knoevenagel‐Michael‐cyclocondensation reactions

In this paper, guanidine groups (Gn) supported on modified magnetic nanoparticles (Fe₃O₄–4,4′‐MDI) were synthesized for the first time. The catalyst synthesized was characterized by various techniques such as SEM (Scanning Electron Microscopy), TEM (Transmission electron microscopy), XRD ( X‐ray Diffraction ), TGA (Thermogravimetric ananlysis), EDS ( Energy‐dispersive X‐ray spectroscopy ) and VSM (vibrating sample magnetometer). The catalyst activity of modified MNPs–MDI‐Gn, as powerful basic nanocatalyst, was probed through the Knoevenagel and Tandem Knoevenagel–Michael‐cyclocondensation reactions. Conversion was high under optimal conditions, and reaction time was remarkably shortened. This nanocatalyst could simply be separated and recovered from the reaction mixture by simple magnetic decantation and reused many times without significant loss of its catalytic activity. Also, the nanocatalyst could be recycled for at least seven (Knoevenagel condensation) and six (Knoevenagel and Tandem Knoevenagel–Michael‐cyclocondensation) additional cycles after they were separated by magnetic decantation and, washed with ethanol, air‐dried, and immediately reused.     

Sulfamic Acid‐functionalized Nano‐titanium dioxide as a Novel and Highly Efficient Heterogeneous Nanocatalyst for One‐pot and Solvent‐free Synthesis of Hexahydroquinolines

Hexahydroquinolines are synthesized via one‐pot, four‐component condensation of 1,3‐cyclic diketones, aromatic aldehydes, malononitrile, and ammonium acetate in the presence of sulfamic acid‐functionalized nano‐titanium dioxide as a novel type of heterogeneous nanocatalyst. The optimized reaction condition is achieved using response surface method (Box–Behnken design [BBD ]). Operational simplicity, low cost, nontoxic nature, and high reusability of the catalyst together with simple work‐up and excellent product yields are the main advantages of this methodology. Also, the nanocatalyst can be recovered easily by centrifugation and reused efficiently for at least seven consecutive runs.     

单组分阴离子聚氨酯水乳液结构与性能

聚氨酯乳液;聚醚多元醇;二羟甲基丙酸;单组分阴离子聚氨酯水乳液结构与性能     

TDI和MDI洁净合成方法的研究进展

对甲苯二异氰酸酯（TDI）和二苯甲烷二异氰酸酯（MDI）的合成方法,尤其是用碳酸二甲酯（DMC）代替光气的洁净合成方法的研究进展进行了综述。重点讨论了反应所涉及到的催化剂体系及其反应性能。     

甲苯二异氰酸酯的气相色谱-质谱分析

采用气相色谱－质谱分析甲苯二异氰酸酯（TDI）,以TDI80为例,对测试过程中样品的存放、溶剂及色谱条件的选择、组分定量作了探讨,获得满意的结果。该法无需标样,具有定性定量准确、简便的特点。     

Biofunctional rapid prototyping for tissue-engineering applications: 3D bioplotting versus 3D printing

Two important rapid-prototyping technologies (3D Printing and 3D Bioplotting) were compared with respect to the computer-aided design and free-form fabrication of biodegradable polyurethane scaffolds meeting the demands of tissue-engineering applications. Aliphatic polyurethanes were based on lysine ethyl ester diisocyanate and isophorone diisocyanate. Layer-by-layer construction of the scaffolds was performed by 3D Printing, that is, bonding together starch particles followed by infiltration and partial crosslinking of starch with lysine ethyl ester diisocyanate. Alternatively, the 3D Bioplotting process permitted three-dimensional dispensing and reactive processing of oligoetherurethanes derived from isophorone diisocyanate, oligoethylene oxide, and glycerol. The scaffolds were characterized with X-ray microtomography, scanning electron microscopy, and mechanical testing. Osteoblast-like cells were seeded on such scaffolds to demonstrate their potential in tissue engineering. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 624–638, 2004     

Metal-Containing Initiator Systems. 30. Vinyl Polymerization Initiated with Bis(ethyl acetoacetato)copper(II) and Maleimide

Some electron-accepting compounds such as maleimide (MIm), maleic anhydride (MAn), and tetracyanoquinodimethane were found to show pronounced accelerating effects on vinyl polymerization initiated with metal chelates. The polymerization of methyl methacrylate (MMA) initiated with bis(ethyl acetoacetato)-copper(II) (Cu(eacac)₂) and MIm was studied kinetically in benzene. The overall activation energy of the polymerization was calculated to be 11.5 kcal/mol. This value was much lower than that (17.6 kcal/mol) for the polymerization of MMA with Cu(eacac)₂ alone. The polymerization rate (R_p) was expressed as R_p =k[MIm]^1/2 [Cu(eacac)₂]^1/2 [MMA] The first-order dependence of R_p on the monomer concentration indicated that the monomer had no participation in the initiation step, in contrast with polymerization in the absence of MIm (where a monomer concentration dependence of 1.4th order was observed). Electronic spectroscopic study revealed that a complex between MIm and Cu(eacac)₂ had been formed. The ligand radical, an acetylcarboethoxymethyl radical, was trapped by 2-methyl-2-nitrosopropane in the reactions of Cu(eacac)₂ with MIm and with MAn in benzene. From these results the mechanism of the initiation of polymerization is discussed.     

Functional Monomers and Polymers. LX. Effects of Counterions on the Structure of Cu(II)-Polyvinylimidazole and Cu(II)lmidazole Complexes in Aqueous Solution

The effect of counterion types on the structure of Cu(II) complexes of imidazole and poly-4(5)-vinylimidazole in aqueous solution was studied by spectroscopic and electron spin resonance (ESR) techniques. Visible and ESR spectra of both complexes in aqueous solution containing NaClO₄, KNO₃, KC1, and KBr showed only a slight change from each other in the presence of different counterions. On the other hand, the frequency of the center of absorption band in the visible region (λ_max) and ESR parameters of the complex in aqueous solution did not correspond to those reported for its crystalline state, and in addition, those of the polymeric Cu(II) complex were different from those of the low molecular weight Cu(II) complex. It was proposed that in aqueous solution, water molecules are coordinated to the axial position of the complex where counterion molecules are present in the crystalline state, and that the structure of the polymeric Cu(II) complex is different from that of the low molecular weight Cu(II) complex due to steric hindrance of the polymeric ligand.