Study of miscibility,crystallization, mechanical properties,and thermal stability of blends of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)

Natural amorphous polymer poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3HB4HB) containing 41 mol % of 4HB was blended with poly(3‐hydroxybutyrate) (PHB) with an aim to improve the properties of PHB. The influence of P3HB4HB contents on thermal and mechanical properties of the blends was evaluated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, stress–strain measurement and thermo gravimetric analyzer. Miscibility of PHB/P3HB4HB blends was mainly decided by the contents of P3HB4HB. When P3HB4HB exceeded 50 wt %, the two polymer phases separated and showed immiscibility. The addition of P3HB4HB did not alter the crystallinity of PHB, yet it diluted the PHB crystalline phase as revealed by DSC studies. DSC and FTIR results showed that the overall crystallinity of the blends decreased remarkably with increasing of P3HB4HB contents. Decreased glass transition temperature and crystallinity imparted desired flexibility for the blends. The ductility of the blends increased progressively with increasing of P3HB4HB content. Thus, the PHB mechanical properties can be modulated by changing the blend composition. P3HB4HB did not significantly improve the thermal stability of PHB, yet it is possible to melt process PHB without much molecular weights loss via blending it with suitable amounts of P3HB4HB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

从微生物细胞中分离提取PHB的方法的综述

介绍和归纳目前文献报导的从微生物细胞中分离提取ＰＨＢ的各种方法，包括溶剂萃取法，化学试剂法，机械破碎法和酶法。对这些方法的优缺点进行了评述，提出发展机械的，物理的，化学的，生物的多种方法相结合以去除菌体中非ＰＨＢ的杂质来分离提取ＰＨＢ半是今后研究的一个方向。     

Eco-friendly electronics,based on nanocomposites of biopolyester reinforced with carbon nanotubes: a review

ABSTRACT

Fabrication of electronic materials from nanocomposite of biopolyesters reinforced with carbon nanotubes can be regarded as the effective alternative for conventional nanocomposites consisting of non-biodegradable polymers. Commercial availability of biopolyester-based nanocomposites is limited because of their high cost compared to other polymers, but the factor of their compostable nature is worthless for environmental protection. Such nanocomposites have potential applications in biodegradable sensors, EMI materials, etc. In this review, the current progress of biopolyester/CNTs nanocomposites in the field of biodegradable electronics is reviewed and also the impact of CNTs dispersion on electrical, thermal and mechanical properties of eco composites is stipulated.     

外碳源投量对亚硝酸型反硝化过程N2O释放影响

为实现N_2O的减量化控制或资源化利用,接种普通活性污泥,以乙酸钠和硝酸盐为基质,通过淘洗反硝化聚磷菌,在SBR中以厌氧/缺氧交替运行的方式启动內源反硝化,单周期内约50%的NO-3-N转化为NO-2-N,N_2O释放速率随着亚硝酸的积累逐渐增大,N_2O转化率(释放量占TN去除的比例)为2.04%.在此基础上,分别取缺氧末和厌氧末污泥,对比研究胞内聚合物PHB合成前后,外碳源投加量(碳氮比为0,0.75和2.50)对亚硝酸型反硝化过程N_2O释放特性的影响,结果表明,外碳源存在时,N_2O释放量随总碳源的增加呈略微减少的趋势,转化率在0.24%~1.61%;而当仅利用內源物质进行反硝化时,N_2O的转化率高达15.90%,单位SS最大释放速率达71.29μg/(min·g),释放量是其余条件下的14~26倍.表明单独利用PHB进行亚硝酸型反硝化会大幅增加N_2O的释放.     

涂层结构对AlSi/PHB封严涂层热应力影响的有限元分析

可磨耗封严涂层是提升航空发动机气密性和运行效能的一种重要途径,而涂层结构对其热应力及使用寿命具有重要影响。本研究以AlSi/PHB封严涂层为研究对象,利用ABAQUS有限元仿真软件和Python编程语言建立了具有不同结构参数的涂层有限元模型,系统研究了面层厚度、聚苯酯颗粒及孔隙结构特性对热震工况下涂层热应力的影响规律。结果表明：当面层厚度为0.1 mm～1.9 mm时,面层厚度对涂层-基体界面应力的影响小于其对涂层侧面应力的影响,且当面层厚度超过0.3 mm左右时,涂层中出现最大拉应力的部位由涂层-基体界面转变为涂层侧面;当聚苯酯颗粒含量为30 vol.%～50 vol.%时,随着聚苯酯含量的增加,涂层-基体界面和涂层侧面的峰值应力均波动不明显;当面层孔隙率为5 vol.%～15 vol.%时,涂层-基体界面峰值应力随孔隙率的增大呈现先降低后增大的趋势;当孔隙直径为60μm～110μm时,涂层内部峰值拉应力随孔隙直径的增大而增大。综合考虑涂层结构与热应力的关系,AlSi/PHB封严涂层的结构参数优选为：面层厚度为0.3 mm～1.1 mm之间,聚苯酯颗粒含量为40 vol.%～50 v...     

Z5-G菌生产聚β-羟基丁酸发酵动力学模型

研究了Z5 G菌株在 3L搅拌发酵罐中以蔗糖为碳源分批发酵生产聚β 羟基丁酸 (PHB)的生长特性。在Lo gistic方程和Luedeking Piret方程的基础上,建立了Z5 G菌发酵过程中菌体生长、基质消耗、产物形成的动力学模型。应用MathCAD软件处理实验数据和模型,拟合出所有模型参数,建立了动力学模型,经过验证模型预测值和实验值吻合较好,表明此动力学模型对指导PHB的发酵生产具有实际意义。     

PHB在生产可降解塑料方面的应用及其微生物累积的研究进展

着重介绍了聚β-羟基丁酸（PHB）的一些性质、用途以及在生产可降解塑料方面的应用情况，同时也介绍了微生物累积PHB的情况，并对微生物累积PHB以及PHB的研究发展提出了一点建议。     

探讨DiffServ在MPLS上的实现

本文介绍了为保证IP网QoS的MPLS,DiffServ及MPLS与DiffServ的结合问题。     

OPNET环境下DiffServ机制的仿真

介绍了DiffServ机制的体系结构和基本机制,并建立了基于OPNET环境下的仿真模型。通过对DiffServ机制的4种转发类型进行仿真,收集仿真结果。通过分析结果研究不同服务级别设置对其QoS性能的影响。