A Novel Organophosphorus Hybrid with Excellent Thermal Stability: Core-Shell Structure, Hybridization Mechanism, and Application in Flame Retarding Semi-Aromatic Polyamide.
An organophosphorous hybrid (BM@Al-PPi) with unique core-shell structure was prepared through hybridization reaction between boehmite (BM) as the inorganic substrate and phenylphosphinic acid (PPiA) as the organic modifier. Fourier transform infrared spectra (FTIR), solid state (31)P and (27)Al magic angle spinning nuclear magnetic resonance, X-ray diffraction, and element analysis were used to investigate the chemical structure of the hybrids, where the microrod-like core was confirmed as Al-PPi aggregates generated from the reaction between BM and PPiA, and those irregular nanoparticles in the shell belonged to residual BM. Compared with the traditional dissolution-precipitation process, a novel analogous suspension reaction mode was proposed to explain the hybridization process and the resulting product. Scanning electronic microscopy further proved the core-shell structure of the hybrids. BM exhibited much higher initial decomposition temperature than that of Al-PPi; therefore, the hybrid showed better thermal stability than Al-PPi, and it met the processing temperature of semi-aromatic polyamide (HTN, for instance) as an additive-type flame retardant. Limiting oxygen index and cone calorimetric analysis suggested the excellent flame-retardant performance and smoke suppressing activity by adding the resulting hybrid into HTN.
Aluminum Hydroxymethylphosphinate and Melamine Pyrophosphate: Synergistic Flame Retardance and Smoke Suppression for Glass Fiber Reinforced Polyamide 6
In this manuscript, synergistic effect was found when aluminum hydroxymethylphosphinate (AHMP) and melamine pyrophosphate (MPyP) with a suitable mass ratio were used together for glass-fiber-reinforced polyamide 6 composites (GFPA6). Both vertical burning test (UL-94) and limited oxygen index (LOI) results showed that GFPA6 containing 5 wt % AHMP and 25 wt % MPyP had excellent flame retardance, i.e. its LOI value was 31.0 and UL-94 reached V-0 rating even for the sample with 1.6 mm thickness. Besides, the flammable properties and smoke suppression of GFPA6 were also improved demonstrated by cone calorimetry results. The thermal stability and the decomposition activation energies (Eα) were studied by TGA. Moreover, the morphology of char after the LOI test was investigated by SEM. It was found that the interaction existing between PA6, AHMP, and MPyP resulted in the higher char content and stable char layer on the GFPA6 surface, which is helpful in improving the flame retardancy of GFPA6.
Increasing pulp yield in kraft cooking of softwoods by high initial effective alkali concentration (HIEAC) during impregnation leading to decreasing secondary peeling of cellulose
Abstract Pulp yield can be improved by a more homogeneous delignification of the chips, achieved by improved impregnation prior to the cooking stage. Complete and efficient impregnation is obtained by increasing the diffusion rate by means of an impregnation liquor with a high initial effective alkali concentration (HIEAC). In the present study, the effect of HIEAC in the impregnation was evaluated and compared to a reference impregnation procedure and a prolonged impregnation. After the various impregnation scenarios, the alkali concentration was always adjusted to the same level in the beginning of the cooking stage. Impregnation with a HIEAC resulted in yield improvements by 1–1.5% units, due to a higher cellulose yield and possibly also to higher yield of glucomannan. The HIEAC with an even alkali distribution within the chips prior to the cooking stage resulted in a more uniform delignification carbohydrate degradation. Yield increase obtained by uniform delignification is due to both decreased shives content as well as less secondary peeling.