Fire performance and mechanical properties of phenolic foams modified by phosphorus-containing polyethers

Two kinds of novel phosphorus-containing polyether toughening agents were synthesized and characterized by ¹H nuclear magnetic resonance (¹H NMR) and Fourier transform infrared spectra (FTIR). Afterwards, a series of phenolic foams with different loadings of phosphorus-containing toughening agents were prepared. The apparent density and scanning electron microscopy (SEM) results showed that the addition of 5 wt% toughening agents increased the expansion ratio and promoted the formation of uniform cells. The limiting oxygen index (LOI) values of modified phenolic foams decreased with the increase of modifier content, but it still remained at 40% even if the amount of modifier loadings was 10 wt%. UL-94 results showed all samples can pass V0 rating, indicating the modified foams still have great flame retardance. Microscale combustion calorimetry (MCC) results indicated that the peak heat release rate (PHRR) and total heat release (THR) of the modified foams were reduced by 42% and 35%, respectively, compared to the pure phenolic foams. Moreover, the thermal stability of samples was investigated by thermogravimetric analysis (TGA). The mechanical properties were evaluated and correlated with composition and structural features.     

Investigation of a combination of novel polyphosphoramide and boron-containing compounds on the thermal and flame-retardant properties of polystyrene

Novel, predominantly alternating poly(ether ester)s, poly(butylene-3/4-hydroxy benzoate)s (PBHB)s were synthesized by the hydrogenation of the corresponding unsaturated polymers obtained by forming ether and ester linkages under one pot conditions. The ether substitution caused a reduction in glass transition temperature, T_g. The melting transition was also lowered by more than 100°C compared to poly(butylene terephthalate) as studied by the differential scanning calorimetry (DSC). Crystallization was observed during heating as well as cooling in the DSC studies. Wide angle X-ray diffraction (WAXRD) analysis also indicated that PB-4-HB was semi-crystalline in nature. The thermal stability of hydrogenated polymer was better than that of the unsaturated polymer.

Influence of nickel ions for electroless Ni–P plating on polyester fabric

Properties of electroless Ni–P plated polyester fabric mainly depend on the plating bath constituents/conditions. The effects of NiSO₄ concentration of the plating bath on the deposition rate, phosphorus content, surface morphology, and crystal structure of the electroless Ni–P plated polyester fabric were investigated. The study revealed that phosphorus content in the deposits decreased at higher NiSO₄ concentration. SEM micrographs showed that nodule size of the Ni–P deposits increased. All the Ni–P deposits had an amorphous structure. The electromagnetic interference (EMI) shielding effectiveness (SE) of electroless Ni–P plated polyester fabric was evaluated. With the rise of nickel ion in the solution, the EMI SE of the Ni–P plated polyester fabric increased.     

Novel styrene polymers functionalized with phosphorus–nitrogen containing molecules: Synthesis and properties

A phosphorus and nitrogen-containing compound with high phosphorus content, AC₂NP₂, was firstly synthesized by the Kabachnik–Fields reaction and followed by esterification with acryloyl chloride. The synthesized comonomer was then incorporated into different amounts of polystyrene via radical solution polymerization. The copolymers were well characterized using Fourier transform infrared (FTIR), UV/vis spectrophotometer, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC) and LOI. The results showed that the AC₂NP₂ was easily incorporated into the backbone of polystyrene, and the copolymers prepared have high transparency. The glass transition temperature (T_g) of the copolymers was decreased with increasing the AC₂NP₂ content, due to the introduction of much more flexible molecular chain. The TGA results revealed that the introduction of AC₂NP₂ units slightly decreased the initial decomposition temperatures, but significantly improved the thermal stability of copolymers at high temperature regions under both nitrogen and air atmosphere. Furthermore, all the copolymers exhibited much lower flammability as compared with virgin polystyrene.     

Construction and evaluation of high-quality n-ZnO nanorod/p-diamond heterojunctions

Vertically-aligned ZnO nanorods (NRs) arrays were synthesized by a low-temperature solution method on boron-doped diamond (BDD) films. The morphology, growth direction, and crystallinity of the ZnO NRs were studied by scanning electron microscopy, X-ray diffraction and cathodoluminescence. Electrical characterization of the ZnO NR/BBD heterostructures revealed characteristic p-n junction properties with an on/off ratio of about 50 at +/- 4 V and a small reverse leakage current approximately 1 microA. Moreover, the junctions showed an ideality factor around 1.0 at a low forward voltage from 0 to 0.3 V and about 2.1 for an increased voltage ranging from 1.2 to 3.0 V, being consistent with that of an ideal diode according to the Sah-Noyce-Shockley theory.     

Developmental changes in prostacyclin synthesis are conserved in cultured pulmonary endothelium and vascular smooth muscle

Annexins are ubiquitous cellular proteins of unknown primary function that bind to anionic phospholipid membranes in a calcium-dependent manner. Correlative studies involving X-ray crystallography and electron microscopy suggest that annexins undergo a structural change upon binding to supported lipid monolayer membranes. In this investigation, novel spectroscopic and analytical techniques have been applied to verify and characterize this change. Soluble annexin V was examined with ordinary transmission infrared spectroscopy, while membrane-bound annexin V was examined with both transmission and internal reflection infrared spectroscopy. Spectra were processed by linked analysis, whereby multiple spectra are fit simultaneously with component bands that are constrained to share common fitting parameters. This approach is shown to enhance the sensitivity and accuracy of the bandfitting procedure. Our results are consistent with the general mode of membrane binding inferred from electron microscopy studies, and they provide independent support for the conclusion that annexin V undergoes a conformational change upon binding to lipid monolayer membranes. Most likely, this change involves the formation of new beta structure in which interstrand hydrogen bonds orient parallel to the membrane surface.     

Phase noise measurement of free-running microwave oscillators at 5.8 GHz using 1/3-subharmonic injection locking

An innovative method using subharmonic injection locking technique for the phase noise measurement of free-running microwave oscillators is presented. To reduce the system cost, a two-tier injection locking approach is used and an effective 1/3-subharmonic injection is established. Measurement on a 1.8-V 5.85-GHz voltage controlled oscillator demonstrates that the measurement system is promising.     

The role of cortical area MST in a model of combined smooth eye-head pursuit

Pseudorandom encoding is a statistical method for designing Fourier transform holograms by mapping ideal complex-valued modulations onto spatial light modulators that are not fully complex. These algorithms are notable because their computational overhead is low and because the space-bandwidth product of the encoded signal is identical to the number of modulator pixels. All previous pseudorandom-encoding algorithms were developed for analog modulators. A less restrictive algorithm for quantized modulators is derived that permits fully complex ranges to be encoded with as few as three noncollinear modulation values that are separated by more than 180 degrees on the complex plane.     

Deformation of mild steel plates subjected to large-scale explosions

This paper presents the results of two test programmes in which quadrangular mild steel plates are subjected to pressure loads created by exploding charges ranging from 100 to 26,288 kg. The charge consists of different ordnances stacked in different configurations, namely compacted and widespread in a carpet-like form. The effects of the charge configurations on the response of the square mild steel plates are investigated. Simple analytical evaluations of the pressures and impulses are used for the purpose of comparison with the experiments. The correlation shows satisfactory agreement, despite the imperfect terrain and different complex explosive loading arrangement.     

机械工程专业生产实习的改革探讨

对大学机械工程专业教学中生产实习基地、实习组织形式和内容、实习管理和考评的改革等进行了探讨.