热/自然交变环境下玻璃纤维增强SiO2气凝胶复合材料模拟使役工况试验研究

目的 研究装备动力舱在热/自然交变环境下玻璃纤维增强SiO2气凝胶复合材料性能随模拟使役工况试验时间的退化规律,提升装备动力舱热/自然交变环境效应控制水平。方法 以玻璃纤维增强SiO2气凝胶复合材料为研究对象,以湿热、盐雾和高温试验为热/自然交变环境试验谱,以振动试验为加速因子,开展5个周期的实验室模拟使役工况加速试验,对比分析样件初始状态和每一个周期试验后的性能。结果 经模拟使役工况试验后,玻璃纤维增强SiO2气凝胶复合材料的颜色由白色逐渐变成黄色,SiO2气凝胶含量逐渐减少,纤维元素组成变化不明显,导热系数升高,隔热性能下降,且均在4周期模拟使役工况试验后出现明显变化。结论 玻璃纤维增强SiO2气凝胶复合材料经5个周期的模拟使役工况试验后,其常温导热系数仅为0.026 4 W/(m.K),热面温度为200 ℃时,冷面平均温度仅为68.5 ℃,热/自然交变温差为43.5 ℃,具有良好的环境适应性。     

Cap and trade schemes on waste management: A case study of the Landfill Allowance Trading Scheme (LATS) in England

The Landfill Allowance Trading Scheme (LATS) is one of the main instruments used in England to enforce the landfill diversion targets established in the Directive 1999/31/EC of the European Parliament and of the Council of 26 April 1999 on the landfill of waste (Landfill Directive). Through the LATS, biodegradable municipal waste (BMW) allowances for landfilling are allocated to each local authority, otherwise known as waste disposal authorities (WDAs). The quantity of landfill allowances received is expected to decrease continuously from 2005/06 to 2019/20 so as to meet the objectives of the Landfill Directive. To achieve their commitments, WDAs can exchange, buy, sell or transfer allowances among each other, or may re-profile their own allocation through banking and/or borrowing. Despite the goals for the first seven years – which included two target years (2005/06 and 2009/10) – being widely achieved (the average allocation of allowances per WDA was 22.9% higher than those finally used), market activity among WDAs was high and prices were not very stable. Results in terms of waste reduction and recycling levels have been satisfactory. The reduction of BMW landfilled (in percentage) was higher during the first seven years of the LATS period (2005/06–2011/12) (around 7% annually) than during the previous period (2001/02–2004/05) (4.2% annually). Since 2008, the significance of the LATS diminished because of an increase in the rate of the UK Landfill Tax. The LATS was suppressed after the 2012/13 target year, before what it was initially scheduled. The purpose of this paper is to describe the particularities of the LATS, analyse its performance as a waste management policy, make a comparison with the Landfill Tax, discuss its main features as regards efficiency, effectiveness and the application of the “polluter pays” principle and finally discuss if the effect of the increase in the Landfill Tax is what made the LATS ultimately unnecessary.     

生物硫铁生成菌的选育及其在重金属废水处理中的应用

为开发高效经济、环境友好的重金属废水处理技术,采用亨盖特(Hungate)厌氧技术分离出一株产生物硫铁复合材料的硫酸盐还原菌(Sulfate reducing bacteria,SRB),命名为SRB2,并对该菌株进行了生理特性、培养工艺和废水处理研究.菌体杆状稍有弯曲,革兰氏阴性菌,最佳碳源为乳酸钠.pH范围5.0～9.0,最适pH 7.0,最适温度为35℃,培养3 d生物硫铁量和硫化物含量能达最大值,分别为2.85 g L-1、358.048 mg L-1.正交试验结果表明,乳酸钠9.0 g L-1+组合氮源1.5 g L-1+硫酸亚铁10.0 g L-1时生物硫铁产量最高.16S rDNA序列分析表明,菌株与脱硫弧菌属Desulfovibriodesulfuricans strain 734同源性为99%.采用生物硫铁处理重金属Cu2+、Pb2+、Cd2+废水,结果表明生物硫铁能快速处理含Cu2+、Pb2+、Cd2+废水,2 min去除率达99.8%以上.因此,生物硫铁在各类重金属废水处理与重金属废水污染事故应急处理中具有较好的应用前景.     

玻璃纤维增强聚对苯二甲酸乙二醇酯/次磷酸铈复合材料的制备及其阻燃性能研究

首先合成并表征了一种新的阻燃剂-次磷酸铈（CHP）;然后采用熔融共混的方法制备了玻璃纤维（GF）增强聚对苯二甲酸乙二醇酯（PET）/CHP（PET/GF/CHP）复合材料;探讨了CHP对PET/GF复合材料热稳定性和燃烧性能的影响。材料的热稳定性是由热失重分析（TGA）进行表征的,燃烧性能是通过氧指数（LOI）、垂直燃烧（UL-94）以及锥形量热仪进行测试的,炭渣形貌由扫描电子显微镜（SEM）进行表征。结果表明：CHP的引入保持了PET/GF的热稳定性。含有15wt%CHP的PET/GF材料（PET/GF/CHP15）,其LOI为30%,且能达到UL-94V-0级别。此外,与PET/GF相比,PET/GF/CHP15热释放速率峰值和热释放总量分别下降了67%和27%。SEM分析表明CHP的加入使得材料在燃烧后有大量致密的炭渣覆盖在玻璃纤维的表面,这些炭渣不仅降低了玻璃纤维的导热性,而且切断了可燃物质的传送通道,从而提高了材料的阻燃性能。     

Bioabsorbable soy protein plastic composites: Effect of polyphosphate fillers on water absorption and mechanical properties

The use of synthetic and natural bioabsorbable plastics has been severely limited due to their low stiffness and strength properties as well as their strong tendency to absorb moisture. This research focused on the development of bioabsorbable polyphosphate filler/soy protein plastic composites with enhanced stiffness, strength, and water resistance. Bioabsorbable polyphosphate fillers, biodegradable soy protein isolate, plasticizer, and adhesion promoter were homogenized and compression-molded. Physical, mechanical, and water absorption testing was performed on the molded specimens. Results showed improvements in stiffness, strength, and water resistance with increasing polyphosphate filler content up to 20% by weight. Application of a coupling agent produced further mechanical property enhancements and a dramatic improvement in water resistance, interpreted by an interfacial chemical bonding model. Examination of the fracture surfaces of the materials revealed that the addition of the polyphosphate fillers changed the failure mode from brittle to pseudo-ductile. These results suggest that these materials are suitable for many load-bearing applications in both humid and dry environments where current soy protein plastics are not usable.     

Biodegradation by Composting of Surface Modified Starch and PVA Blended Films

Several starch/PVA/glycerol polymer blends were prepared by a solution casting technique and examined for biodegradation by composting over 45 days. Within this time frame, the starch and glycerol components were fully degraded, leaving the PVA component essentially intact. The lowest PVA content film (20%) was selected as a polymer with enough PVA to impart important physical characteristics, but also enough starch to be considered biodegradable. The film characteristics were further improved by surface modification with chitosan. This modification did not interfere with the biodegradation of the starch component. Furthermore, there was slight evidence that PVA biodegradation had been initiated in composted, surface modified starch/PVA blends.     

Biodegradation Behavior of Some Vegetable Oil-Based Polymers

The potential biodegradability of several vegetable oil-based polymers was assessed by respirometry in soil for 60–100 days at temperatures of 30–58°C. Films of soybean oil and linseed oil which were oxidatively polymerized (Co catalyst) on a kraft paper support were 90%–100% mineralized to CO₂ after 70 days at 30°C. Mineralization of polymerized tung oil to CO₂ was much slower than soy or linseed oils. Mineralization of epoxy resins made from epoxidized soybean oil (ESO) and aliphatic dicarboxylic acids was rapid while mineralization of similar resins made with a triacid (citric) was slower. There was no significant degradation of polyamine/ESO resins after 100 days at 58°C. Mineralization of the available carbon in vegetable oil polyurethanes and cationically polymerized ESO was less than 7.5% after 70 days at 30°C and 25 days at 55°C compared to 100% for soybean oil. From these results, it appears that triglycerides highly cross-linked with non-degradable linkages are not biodegradable to a significant extent while triglycerides cross-linked with hydrolysable bonds such as esters remain biodegradable.     

The influence of soil macroinvertebrates on primary biodegradation of starch-containing polyethylene films

The primary biodegradability of polyethylene (PE) films containing different percentages of cornstarch (0–50%) and other additives (prooxidant, oxidized polyethylene) was tested using four species of earthworms (Eisenia fetida, Lumbricus terrestris, Aporectodea trapezoides, Aporectodea tuberculata), three species of cockroaches (Periplaneta americana, Blaberus sp.,Blattella germanica), termites (Reticulotermes flavipes), sowbugs (Porcellio laevis), and crickets (Acheta domesticus). These studies were conducted to elucidate the potential role of soil macroinvertebrates in degrading starch/PE biodegradable plastics. The results of the macroinvertebrate bioassays indicate that crickets, cockroaches, and sowbugs consumed starch-containing PE films most readily. In addition, the degree to which the films were attacked and consumed was directly related to the starch content of the film. Films with oxidized polyethylene and those containing prooxidant (vegetable oil and a transition metal catalyst) were also consumed. None of the four species of earthworms tested or the termites showed any activity toward the starch/polyethylene films. These results have important implications for determining the fate of novel plastic formulations which claim to be biodegradable in natural environments. Studies such as these, coupled with studies on microbial degradation, will help provide the type of information needed to assess the environmental fate of biodegradable starch/PE plastics and fill the voids in the scientific database regarding this rapidly developing field.     

Pseudomonas lemoignei has five poly(hydroxyalkanoic acid) (PHA) depolymerase genes: A comparative study of bacterial and eukaryotic PHA depolymerases

Four polyhydroxyalkanoate (PHA) depolymerases were purified from the culture fluid ofPseudomonas lemoignei: poly(3-hydroxybutyrate) (PHB), depolymerase A (M _r , 55,000), and PHB depolymerase B (M _r , 67,000) were specific for PHB and copolymers of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3HV) as substrates. The third depolymerase additionally hydrolyzed poly(3-hydroxyvalerate) (PHV) at high rates (PHV depolymerase;M _r , 54,000). The N-terminal amino acid sequences of the three purified proteins, of a fourth partially purified depolymerase (PHB depolymerase C), and of the PHB depolymerases ofComamonas sp. were determined. Four PHA depolymerase genes ofP. lemoignei (phaZ1,phaZ2,phaZ3, andphaZ4) have been cloned inEscherichia coli, and the nucleotide sequence ofphaZ1 has been determined recently (D. Jendrossek, B. Müller, and H. G. Schlegel,Eur. J. Biochem. 218, 701–710, 1993). In this study the nucleotide sequences ofphaZ2 andphaZ3 were determined.PhaZ1,phaZ2, andphaZ4 were identified to encode PHB depolymerase C, PHB depolymerase B, and PHV depolymerase, respectively.PhaZ3 coded for a novel PHB depolymerase ofP. lemoignei, named PHB depolymerase D. None of the four genes harbored the PHB depolymerase A gene, which is predicted to be encoded by a fifth depolymerase gene ofP. lemoignei (phaZ5) and which has not been cloned yet. The deduced amino acid sequences ofphaZ1–phaZ3 revealed high homologies to each other (68–72%) and medium homologies to the PHB depolymerase gene ofAlcaligenes faecalis T₁ (25–34%). Typical leader peptide amino acid sequences, lipase consensus sequences (Gly-Xaa-Ser-Xaa-Gly), and unusually high proportions of threonine near the C terminus were found in PhaZ1, PhaZ2, and PhaZ3. Considering the biochemical data of the purified proteins and the amino acid sequences, PHA depolymerases ofP. lemoignei are most probably serine hydrolases containing a catalytical triad of Asp, His, and Ser similar to that of lipases. A comparison of biochemical and genetic data of various eubacterial and one eukaryotic PHA depolymerases is provided also.Paper presented at the Bio/Environmentally Degradable Polymer Society—Second National Meeting, August 19–21, 1993, Chicago, Illinois.     

Effects of biodegradable plastic components on metabolism of an estuarine benthos

We examined the metabolic response of an estuarine benthic community to additions of three materials being considered for use in manufacture of biodegradable substitutes for plastics. Diver-collected cores containing benthos were dosed with 59 g/m² of three test materials, cornstarch, a bacterial polyester (PHBV), and ethylene vinyl alcohol (EVOH), or left undisturbed as controls. Fluxes of dissolved nutrients (ammonia, nitrate + nitrite, phosphate, silica) and dissolved inorganic carbon (DIC) were similar in control cores and cores dosed with EVOH during a 1-month test period at 20°C. Fluxes in cores dosed with starch and PHBV differed significantly from controls but not from each other. After 2 weeks of incubation, production of DIC was higher in cores containing starch and PHBV, while efflux of ammonia, nitrate, and nitrite was reduced. After 4 weeks of incubation, production of DIC was similar among all treatments and controls, while efflux of ammonia was high in the starch- and PHBV-containing cores compared to controls and cores with EVOH. Fluxes of silica and phosphate were similar in all cores during the experiment. These results indicate that both starch and PHBV are carbon-rich substrates readily metabolized by the benthic community but that their presence significantly alters normal nutrient exchange patterns. This response is expected because of the high carbon-to-nitrogen ratio of starch and PHBV and indicates that impacts of these two materials would be similar. However, the high biological oxygen demand of such materials and resulting disturbance of normal nutrient regeneration patterns of the benthos (delayed ammonia efflux and potential stimulation of denitrification) must be considered in developing strategies for their disposal.Paper presented at the Biodegradable Materials and Packaging Conference, September 22–23, 1993, Natick, Massachusetts.