Photoinitiated crosslinking of ethylene‐vinyl acetate copolymers and characterization of related properties

Photoinitiated crosslinking of EVA in the presence of benzophenone (BP) as photoinitiator and triallyl isocyanurate (TAIC) as crosslinker and characterization of the related properties have been studied by gel determination, heat extension, DSC, DMTA, TGA, and mechanical measurements. The photoinitiated crosslinking efficiency of the EVA‐BP‐TAIC system and various factors affecting the crosslinking process, such as photoinitiator and crosslinker and their concentrations, irradiation temperature, and irradiation atmosphere were studied in detail and optimized by comparison of gel contents. The results show that the EVA samples with a thickness of 1 mm are readily crosslinked to a gel content of above 80% with 5 s UV‐irradiation under optimum conditions. The data from the heat extension and DSC show that the crosslinking density of photocrosslinked EVA increase and their crystallinities decrease with increasing the UV‐irradiation time. At the same time, photocrosslinking of EVA leads to a lowering of the melt temperature and a decrease of heat of fusion. The DMTA results show that photocrosslinking increases the amorphous phase and storage modulus of the crosslinked EVA, but does not change the glass transition temperature. The data from TGA and mechanical tests give evidence that the thermal stability and mechanical properties of photocrosslinked EVA samples are much better than those of the uncrosslinked EVA. POLYM. ENG. SCI., 47:1761–1767, 2007. © 2007 Society of Plastics Engineers     

Synthesis and thermotropic liquid‐crystalline behavior of novel main‐chain poly(aryl ether ketones)

Novel aromatic poly(ether ketones) containing bulky lateral groups were synthesized via nucleophilic substitution reactions of 4,4′‐biphenol and (4‐chloro‐3‐trifluoromethyl)phenylhydroquinone (CF‐PH) with 1,4‐bis(p‐fluorobenzoyl)benzene. The copolymers were characterized by differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction, and polarized light microscopy observation. Thermotropic liquid‐crystalline behavior was observed in the copolymers containing 40, 50, 60, and 70 mol % CF‐PH. The crystalline–liquid‐crystalline transition [melting temperature (T_m)] and the liquid‐crystalline–isotropic phase transition appeared in the DSC thermograms, whereas the biphenol‐based homopolymer had only a melting transition. The novel poly(aryl ether ketones) had glass‐transition temperatures that ranged from 143 to 151°C and lower T_m's that ranged from 279 to 291°C, due to the copolymerization. The polymers showed high thermal stability, and some exhibited a large range in mesophase stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1347–1350, 2003     

Capture of gypsy moth,Lymantria dispar (L.), andLymantria mathura (L.) males in traps baited with disparlure enantiomers and olefin precursor in the People's Republic of China

Pheromone traps baited with (+)-disparlure,cis-7,8-epoxy-2methyocta-decane, captured males ofLymantria dispar, L. monacha, andL. mathura in northeastern People's Republic of China.L. dispar responded to the addition of olefin to (+)-disparlure-baited traps in a negative doseresponse manner. Observations on site and seasonal capture ofL. dispar andL. mathura are discussed.Lepidoptera: Lymantriidae.     

Formation of novel polymeric nanoparticles

We have found that not only block copolymers but also ionomers can self-assemble in a selective solvent to form surfactant-free nanoparticles. The self-assembly can be induced by chemical reaction, polymer-polymer complexation, and microphase inversion in addition to the temperature. A recently developed microwave method for the preparation of uniform surfactant-free polymeric nanoparticles is also reviewed. Our results have revealed that for a given dispersion, the particle surface area occupied per stabilizer (surfactant, polymer chains, and ionic groups) is close to a constant.     

PROCESS CONTROL PERSPECTIVE FOR PROCESS ANALYTICAL TECHNOLOGY: INTEGRATION OF CHEMICAL ENGINEERING PRACTICE INTO SEMICONDUCTOR AND PHARMACEUTICAL INDUSTRIES

FDA's Process Analytical Technology (PAT) initiative provides an unprecedented opportunity for chemical engineers to play significant roles in the pharmaceutical industry. In this article, the authors provide their perspectives on (1) the need for chemical engineering principles in pharmaceutical development for a thorough process understanding; (2) applications of chemical engineering principles to meet the challenges from the semiconductor and pharmaceutical industries; and (3) the integration of chemical engineering practice into the semiconductor and pharmaceutical industries to achieve process understanding and the desired state of quality-by-design. A real-world case study from the semiconductor industry is presented to demonstrate how a classic chemical engineering concept, mixing homogeneity, can be implemented by inducing forced flow to ensure an excellent copper electrochemical plating process performance and to improve product quality substantially. Further, a case study of brake system design is discussed with the concept of Dr. Taguchi's robust engineering design to illustrate how quality-by-design can be achieved through appropriate experimental design, in conjunction with the discussion on the concept of quality-by-design in pharmaceuticals. Third, a case study of freeze-dried sodium ethacrynate is presented to demonstrate the vital importance of controlling the processing factors to achieve the desired product stability. Finally, the problems of the current pharmaceutical manufacturing mode, the opportunities and engineering challenges during implementation of PAT in the pharmaceutical industry, and the role of chemical engineering in implementation of PAT is discussed in detail.     

Wood‐fiber/high‐density‐polyethylene composites: Coupling agent performance

The coupling efficiency of seven coupling agents in wood–polymer composites (WPC) was investigated in this study. The improvement on the interfacial bonding strength, flexural modulus, and other mechanical properties of the resultant wood fiber/high‐density polyethylene (HDPE) composites was mainly related to the coupling agent type, function groups, molecular weight, concentration, and chain structure. As a coupling agent, maleated polyethylene (MAPE) had a better performance in WPC than oxidized polyethylene (OPE) and pure polyethylene (PPE) because of its stronger interfacial bonding. A combination of the acid number, molecular weight, and concentration of coupling agents had a significant effect on the interfacial bonding in WPC. The coupling agents with a high molecular weight, moderate acid number, and low concentration level were preferred to improve interfacial adhesion in WPC. The backbone structure of coupling agents also affected the interfacial bonding strength. Compared with the untreated composites, modified composites improved the interfacial bonding strength by 140% on maximum and the flexural storage modulus by 29%. According to the statistical analysis, 226D and 100D were the best of the seven coupling agents. The coupling agent performance was illustrated with the brush, switch, and amorphous structures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 93–102, 2005     

4-溴-1-溴甲基-2-对氯苯基-5-三氟甲基吡咯-3-腈的合成

以2 对氯苯基1 甲基5 三氟甲基2 吡咯啉3 腈为原料,经三步反应合成了4 溴1溴甲基2 对氯苯基5 三氟甲基吡咯3 腈,合成总收率为29.8%。     

Fabrication of polysulfone asymmetric hollow‐fiber membranes by coextrusion through a triple‐orifice spinneret

Polysulfone (PSf) asymmetric hollow‐fiber membranes, which have a dense outer layer but a loose inner layer, were tentatively fabricated by coextrusion through a triple‐orifice spinneret and a dry/wet‐phase inversion process. Two simple polymer dopes were tailored, respectively, for the dense outer layer and the porous inner layer according to the principles of the phase‐inversion process. By adjusting the ratio of the inner/outer extrusion rate, the hollow‐fiber membranes with various thicknesses of outer layers were achieved. The morphology of the hollow‐fiber membranes was exhibited and the processing conditions and the water permeability of the membrane were investigated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 259–266, 2004     

Structure and properties of nitrile rubber (NBR)–clay nanocomposites by co‐coagulating NBR latex and clay aqueous suspension

Nitrile rubber (NBR)–clay nanocomposites were prepared by co‐coagulating the NBR latex and clay aqueous suspension. Transmission electron microscopy showed that the silicate layers of clay were dispersed in the NBR matrix at the nano level and had a planar orientation. X‐ray diffraction indicated that there were some nonexfoliated silicate layers in the NBR–clay nanocomposites. Stress–strain curves showed that the silicate layers generated evident reinforcement, modulus, and tensile strength of the NBR–clay nanocomposites, which were significantly improved with an increase in the amount of clay, and strain‐at‐break was higher than that of the gum NBR vulcanizate when the amount of clay was more than 5 phr. The NBR–clay nanocomposites exhibited an excellent gas barrier property; the reduction in gas permeability in the NBR–clay nanocomposites can be described by Nielsen's model. Compared with gum NBR vulcanizate, the oxygen index of the NBR–clay nanocomposites increased slightly. The feasibility of controlling rubber flammability via the nanocomposite approach needs to be evaluated further. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3855–3858, 2003     

Preparation of V doped lanthanum silicate electrolyte ceramics by combustion method and study on conductance mechanism

Vanadium doped La_9.33Si_6−xV_xO_26+0.5x (x = 0.5, 1.0, 1.5) (LSVO) electrolyte powder was prepared by combustion method at 600°C for 5-7 min. The powder was sintered at 1500°C for 3 hours to prepare LSVO ceramics. XPS, IR, XRD, and EIS analysis show that V⁵⁺ doping replaces Si⁴⁺ in [SiO₄] to form [Si(V)O₄] tetrahedron. With the increase in x, the lattice volume increase. When x = 2.0, the LaVO₄ phase was formed, indicating that the limit doping amount of V⁵⁺ replacing Si⁴⁺ is x ≤ 1.5. The conductivity of LSVO increases significantly with the increase in x (x ≤ 1.0), which attributed to the defect reaction caused by V⁵⁺ doping. The addition of the interstitial oxygen Oi* in 6₃ channels and the increase of lattice volume leads to increased conductivity. When x = 1.0, the highest conductivity is 1.46 × 10⁻² S·cm⁻¹ (800°C). The doping enhancement conductivity mechanism is the Interstitial oxygen defect-Lattice volume composite enhancement mechanism.