[Preparation of microencapsulated red phosphorus and its flame-retardant application in PP composites].

In the present study, the melamine-formaldehyde prepolymer (MFP) was first synthesized at pH 8-8.5 under about 80 degrees C with melamine, formaldehyde, triethanolamine and methanol as the starting materials. Subsequently, the microencapsulated red phosphorus (MRP) was successfully prepared by in-situ polymerization at pH 5.5 under 65 degrees C, using MFP and red phosphorus (RP) powders as raw materials, and potassium persulphate (KPS) as catalyst. The obtained products were detected by differential scan calorimetry (DSC), scanning electron microscope (SEM), Fourier transform infrared (FTIR) and X-ray photo-electron spectroscopy (XPS). It was found that KPS is useful in enhancing the reaction activity of MFP, which can make RP be well encapsulated by melamine-formaldehyde resin (MF) and reduce the reaction time. The DSC, SEM and XPS results show that it won't get well-encapsulated MRP only under acidic condition and without any KPS. When a proper quantity of KPS is employed, the RP particles can be almost completely-encapsulated by MF and the peak temperature of oxidation reaction for MRP is 480 degrees C, which is much higher than that of RP, extending the applications for MRP. The FTIR spectrum demonstrates that the coating material on the surface of RP accurately is MF, in agreement with the reference. Polyproplene (PP) composites with different formulations were prepared by melt extrusion. It was shown that the flame-retardant efficiencies are very low when the PP composites only contain MRP or MH. However, the flame-retardant property can obviously improve if MRP and MH are both used in the PP composites. When PP : MRP: MH = 100 (phr) : 15 (phr) : 50 (phr), the limited oxygen index of the MRP/MH/PP composite is 26%, and vertical firing ranks UL-94 V-0. In addition, the possible flame-retardant mechanism of the PP composites has also been discussed, and further verified by FTIR and Raman spectroscopy.

1,4-Bis(4,5-dihydro-1H-imidazol-2-yl)benzene-4-amino-benzene-sulfonic acid-water (1/2/2).

The asymmetric unit of the title compound, C(12)H(14)N(4)·2C(6)H(7)NO(3)S·2H(2)O, contains one half of a centrosymmetric 1,4-bis-(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) molecule, one 4-amino-benzene-sulfonic acid molecule and one water mol-ecule. In the bib molecule, the imidazole ring adopts an envelope conformation. The benzene rings of bib and 4-aminobenzenesulfonic acid are oriented at a dihedral angle of 21.89 (4)°. In the crystal structure, inter-molecular N-H⋯O, O-H⋯N and O-H⋯O inter-actions link the mol-ecules into a three-dimensional network. Weak π-π contacts between the benzene and imidazole rings and between the benzene rings [centroid-centroid distances = 3.895 (1) and 3.833 (1) Å, respectively] may further stabilize the structure.

2,3,5,6-Tetra-fluoro-1,4-bis-(2-pyridylmethyl-eneamino-meth-yl)benzene.

The title compound, C(20)H(14)F(4)N(4), is a flexible bis-pyridine-type ligand with an extended fluorinated spacer group between the two pyridyl functions. The centroid of the central aromatic ring is situated on a crystallographic center of inversion. The dihedral angle between the pyridine ring and the central benzene ring is 63.85 (9)°. The crystal structure exhibits inter-molecular C-H⋯F hydrogen-bonding inter-actions.