Unsaturated polyester resins modified with phosphorus-containing groups: Effects on thermal properties and flammability

A novel reactive phosphorus-containing monomer [1-oxo-2,6,7-trioxa-1- phosphabicyclo-[2.2.2]octane-methyl diallyl phosphate, PDAP] was synthesized, and various amounts of PDAP were combined with unsaturated polyester by radical bulk polymerization. The resulting flame-retardant unsaturated polyester resin (FR-UPR) samples were investigated by thermogravimetric analysis (TGA), microscale combustion calorimetry (MCC), and limiting oxygen index (LOI) tests. Due to the relatively high phosphorus content of PDAP (18.2 wt%), incorporation of this monomer into unsaturated polyester resin (UPR) led to a marked decrease in the heat release capacity (HRC), the total heat release (THR), an increase in the LOI and the char yield upon combustion. In order to elaborate the interactions between the UPR and PDAP in degradation, differences between the experimental and theoretical mass losses of a FR-UPR sample were evaluated. Furthermore, thermogravimetry-Fourier transform infrared (TG-FTIR) and real-time Fourier transform infrared (RTIR) spectroscopy were employed to investigate the degradation behavior of UPRs, providing insight into the degradation mechanism.     

Microbial desulfurization of waste latex rubber with Alicyclobacillus sp.

A microbe with desulfurizing capability, Alicyclobacillus sp., was selected to recycle waste latex rubber (WLR). The growth characteristics of the microorganism and the technical conditions in the co-culture desulfurization process were studied. The desulfurization effect of Alicyclobacillus sp. on the WLR was characterized, and the mechanism for the microbial desulfurization of WLR was tentatively explored. The results showed that adding 5% (w/v) WLR into medium had little effect on the growth of Alicyclobacillus sp. The surfactant polysorbate 80 (Tween 80) had a toxic effect on Alicyclobacillus sp., but the growth of the microbe was vigorous if the proper technique was used: the mixing of WLR with Tween 80, followed by the addition of the mixture into the culture media. With the increase of desulfurization time, the swelling value of desulfurizated waste latex rubber (DWLR) increased, but the crosslink density decreased. After co-culture desulfurization for 8–10 days, a DWLR with good desulfurization effect was obtained. The mechanical properties of natural rubber (NR)/DWLR composite improved significantly over those of NR/WLR composite. XPS and FTIR results revealed that Alicyclobacillus sp. could break the crosslinked sulfur bonds and oxidize them to sulfones groups. The increase of O element content on the surface of DWLR was confirmed by water contact angle measurements. The relationship between the crosslink density and sol fraction of DWLR with different desulfurization times agreed with the Horikx equation, an indication that the microorganisms could break the crosslinked sulfur bonds on the surface of WLR, but leaving the main chains intact.     

Synthesis of poly(l-lactic acid) with improved thermal stability by sulfonic acid-catalyzed melt/solid polycondensation

Melt/solid polycondensation (MP/SSP) is deemed as an alternative synthetic route besides ring-opening polymerization (ROP) in synthesizing poly(l-lactic acid) (PLLA). However, it is found that PLLA synthesized by MP/SSP has much poorer thermal stability than that by ROP due to more residual Sn(II) metallic catalyst in the former, but sulfonic acids does not show any detrimental effect on the thermal stability of PLLA. To synthesizing PLLA with good thermal stability by MP/SSP, a variety of commercially available sulfonic acids were screened as catalysts in MP/SSP of PLLA. Among these nonmetallic catalysts, it was found that 1,3-propanedisulfonic acid (PSA) and 1,5-naphthalene disulfonic acid (NSA) exhibited satisfactory catalytic reactivity and PLLAs with excellent thermal stability, high molecular weight, little coloration and good optical purity were successfully synthesized by MP/SSP. The decomposition temperature was increased by 80–100 °C in comparison to SnCl₂-catalyzed PLLA, and the thermal stability is comparable to commercial PLLA produced by ROP.     

Synthesis of a novel sulfur-bearing secondary antioxidant with a high molecular weight and its comparative study on antioxidant behavior in polypropylene with two commercial sulfur-bearing secondary antioxidants having relatively low molecular weight

A novel sulfur-bearing secondary antioxidant with a high molecular weight of 2252 (OS-POSS), successfully synthesized via photoinitiated thiol-ene click reaction, was compared with two commercial sulfur-bearing secondary antioxidants on the stabilization of polypropylene (PP). The results of their oxidation induction time (OIT) via differential scanning calorimeter measurement (DSC) showed that the higher the molecular weight of secondary antioxidant is, the longer the OIT value, whether such sulfur-bearing antioxidant is used singly or in combination with primary antioxidant. The study of their long-term accelerated thermal aging in the air oven at 150 °C displayed that the molecular structure of sulfur-bearing secondary antioxidant, besides molecular weight, is another highly important factor determining the antioxidant efficiency, i.e., physical loss of antioxidants with the relatively low molecular weight may determine antioxidant efficiency, whereas thioether groups having neighboring ester carbonyl moieties may decompose more hydroperoxides with quicker rate.     

Identification of two polyamides (PA11 and PA1012) using pyrolysis-GC/MS and MALDI-TOF MS

The main goal of this work is to identify two polyamides (PA11 and PA1012) by mass spectrometry including pyrolysis-GC/MS and MALDI-TOF MS. PA11 and PA1012 have similar properties and cannot be distinguished by many other methods. Using pyrolysis-GC/MS, the pyrograms of PA11 and PA1012 at 600 °C were compared. Specific pyrolyzates for PA11 and PA1012 were obtained, 2-azacyclotridecanone for PA11 and 1,10-diaminodecane, 1,10-dicyanodecane for PA1012, respectively, which was the basis to distinguish them. Meanwhile, MALDI-TOF MS can give specific repeat unit for these two polyamides, dehydrated 11-aminoundecanoic acid (M = 183) for PA11, acetylate of dodecanedioic acid and diaminodecane (M = 366) for PA1012, which can be another means of identifying them.     

TargetATPsite: A template‐free method for ATP‐binding sites prediction with residue evolution image sparse representation and classifier ensemble

Understanding the interactions between proteins and ligands is critical for protein function annotations and drug discovery. We report a new sequence‐based template‐free predictor (TargetATPsite) to identify the Adenosine‐5′‐triphosphate (ATP) binding sites with machine‐learning approaches. Two steps are implemented in TargetATPsite: binding residues and pockets predictions, respectively. To predict the binding residues, a novel image sparse representation technique is proposed to encode residue evolution information treated as the input features. An ensemble classifier constructed based on support vector machines (SVM) from multiple random under‐samplings is used as the prediction model, which is effective for dealing with imbalance phenomenon between the positive and negative training samples. Compared with the existing ATP‐specific sequence‐based predictors, TargetATPsite is featured by the second step of possessing the capability of further identifying the binding pockets from the predicted binding residues through a spatial clustering algorithm. Experimental results on three benchmark datasets demonstrate the efficacy of TargetATPsite. © 2013 Wiley Periodicals, Inc.     

Improvement in Uranium Adsorption Properties of Amidoxime-Based Adsorbent Through Cografting of Amine Group

Amidoxime (AO)/amine co-functionalized polypropylene fiber adsorbents were prepared. The all-polymeric structures were characterized by using Fourier transform infrared spectroscopy (FTIR), optical microscope, contact angle meter and electron spin resonance (ESR) analysis methods, confirming the grafting, modification, and amidoximation stages gravimetrically, spectroscopically, and visually. The properties for the removal of uranyl(VI) from aqueous solutions were investigated. For amidoxime (AO) fiber, high adsorption rate was observed within the first 30 minutes and the plateau value of 40.6% uranium loading (0.0812 mg/g) was reached at around 30 minutes. The adsorption equilibrium for AO/amine fiber was attained within 20 minutes, resulting in the adsorption of 92.6% uranium loading (0.185 mg/g). The percentage of adsorption increases with increasing pH value (2–6), reaches a maximum at pH 6.0 and then remains almost constant for AO/amine fiber, whereas reduces slightly for AO fiber.     

Studies on the Phenol Oxidation with H2O2 Catalyzed by Metallomicelle Made from Crowned Schiff Base Mn(III) Complexes

Metallomicelles made from two Schiff base manganese(III) complexes (MnL¹ and MnL²) and surfactants (CTAB and Brij35) were used as mimetic peroxidase in the catalytic oxidation of phenol by H₂O₂. The catalytic activity of the complexes (MnL¹ and MnL²) were investigated. The mechanism and a kinetic mathematic model of the phenol catalytic oxidation were also studied. The results show the optimum acidity of the enzyme-like system in the paper is ca. pH 7.0, the optimum temperature which is ca. 35°C and the optimum molar ratio of H₂O₂ to the complex is ca. 30 in the complexes-H₂O₂-buffered solution; the Schiff base manganese(III) complexes and their metallomicelles as peroxidase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme.     

Polyvinyl alcohol fibers with functional phosphonic acid group: synthesis and adsorption of uranyl (VI) ions in aqueous solutions

PVA functionalized with vinylphosphonic acid was prepared as a new adsorbent for uranyl (VI) adsorption from aqueous solutions. The vinylphosphonic acid was cografted onto PVA fibers by preirradiation grafting technique. The adsorbent were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorbent was observed to possess a fibrous structure and was bonded with phosphonic acid groups successfully. The adsorbent was used for the adsorption of low levels uranyl (VI) ions from aqueous solutions. The influence of analytical parameters including pH, adsorption time, amount of adsorbent, metal ion concentration, and temperature were investigated on the recovery of uranyl (VI) ion in aqueous solution. The maximum adsorption capacity (32.1 mg g^?1) and fast equilibrium time (30 min) were achieved at pH of 4.5 at room temperature. Thermodynamic parameters (ΔH° = 2.695 kJ mol^?1; ΔS° = 31.15 J mol^?1 K^?1; ΔG° = ?6.748 kJ mol^?1) show the adsorption of an exothermic process and spontaneous nature, respectively. The possible coordination mechanism was illustrated. Adsorption and desorption coexist in aqueous solutions and then the system becomes equilibrium.     

氢分离与CO催化甲烷化双功能型钯复合膜

以多孔Al₂O₃陶瓷为基体材料, 采用浸渍法担载NiO后用2B铅笔修饰NiO/Al₂O₃表面, 通过化学镀法沉积约5 μm厚的金属钯, 还原后成功制得Pd/Pencil/Ni/Al₂O₃膜. 为进行对比, 还制备了未担载镍的Pd/Pencil/Al₂O₃膜. 膜的表面和断面形貌分别采用扫描电镜和金相显微镜观测, 膜的透氢动力学通过H₂/N₂单气体法测试, 并以成分为H₂ 77.8%, CO 5.2%, CO₂ 13.5%和CH₄ 3.5%的原料氢测定了膜的氢分离效果. 结果表明, 未载镍的Pd/Pencil/Al₂O₃膜只具有氢分离作用, 而Pd/Pencil/Ni/Al₂O₃膜还可以有效地将钯膜泄漏的CO和CO₂转化为甲烷, 因而成为双功能型钯膜. 这种双功能膜尤其适用于面向质子交换膜燃料电池(PEMFC)的氢气分离, 既有效解决了PEMFC对氢燃料中CO格外敏感的难题, 又提高了对钯膜缺陷的容忍度, 因而延长了钯膜的使用寿命.