Synthesis, Characterization, and Hydrolytic Degradation of Copolymers of 2-Methylene-1,3-dioxepane with Ethylene and with Styrene

2-Methylene-1,3-dioxepane (MDP) was copolymerized with ethylene (E) at a pressure of approximately 1000 psi and a temperature of approximately 70°C with AIBN as the free radical initiator. The copolymers obtained, poly(MDP-co-E), were characterized by elemental analysis, IR, ¹H-NMR and ¹³C-NMR spectroscopy, DSC, and GPC. The copolymers contained 2–15 mol% ester units. MDP was also copolymerized with styrene (S) at 120°C with di-t-butyl peroxide as the initiator to prepare the copolymer, poly(MDP-co-S). The number-average molecular weights of both types of copolymers were in the range of 6000 to 11,000, and the weight-average molecular weights were in the range of 9000 to 17,000. The melting temperatures of poly(MDP-co-E) decreased with increasing ester unit content in the copolymer. For the MDP-S copolymers, the glass transition temperatures decreased with increasing ester unit content. Both poly(MDP-co-E) and poly(MDP-co-S) were degraded by methanolysis, and their molecular weights decreased by the expected amounts based on the ester unit content.     

The Effect of Acetylation on the Hydrolytic Degradation of PLA/Clay Nanocomposites

In this study, the hydrolytic degradation of Poly(lactic acid) (PLA) and acetylated PLA (PLA-Ac)–clay nanocomposites were investigated. The organo clay was obtained by ion exchange reaction using cetyl tri methyl ammonium bromide (CTAB). Nanocomposites containing 2, 5 and 8% mass ratio of organo clay (CTAB-O) were prepared. PLA and its organo clay nanocomposites were characterized by scanning electron microscope (SEM), thermo gravimetric analysis (TGA) and X-ray diffraction (XRD) to determine the morphology before and after hydrolytic degradation. Fourier transform infrared (FTIR) analyses of PLA and PLA-Ac were also obtained. The hydrolytic degradation of polymers and their composites were investigated in the phosphate buffered saline solution (PBS). The results showed that controlled hydrolytic degradation was observed in the samples with end group modification of PLA. While weight loss of PLA films was 28%, that of PLA-Ac films was 18% after 60 days degradation time. The weight loss was obtained as 29.5 and 25.5% for PLA-5 wt% organo clay (PLA/5CTAB-O) and PLA-Ac-5 wt% organo clay (PLA-Ac/5CTAB-O) nanocomposites films, respectively. It was also observed that thermal degradation of PLA-Ac was much more than that of PLA. Hydrolytic degradation increased depending on organo clay content. The end group modificated PLA results in controlled hydrolytic degradation. While hydrolytic degradation in polymer films occurred as surface erosion, bulk erosion was observed in composite films.     

Morphological Study on Hydrolytic Degradation of Poly(tetramethylene succinate) Single Crystals and Spherulites

The morphological changes of Poly(tetramethylene succinate) single crystal lamellae by hydrolysis are investigated, using TEM, WAXD and SAXS. And the morphology of PTMS spherulites was also observed by optical microscopy after treatments as well as single crystal lamellae. The edge region of single crystal lamella can be most easily affected in the initial stage of hydrolysis. As the hydrolysis time increases, the lamellae are separated into small fragments which may be started from the uneven or irregular parts of the surface. The WAXD results showed that crystallinity were increased with increasing of treatment time. The lamellar thickness decreased at the initial stage of hydrolysis and increased again. There were cracks on the surface of spherulites after hydrolysis and the direction of cracks were tangential direction of spherulites. This result was thought to be from the uniformity of molecular arrangement in the crystallographic unit cell.     

Effect of Degree of Substitution of Octenyl Succinate Starch on Enzymatic Degradation

Octenyl succinate starch of degree of substitution (ds) 0.03, 0.07, and 0.11 was synthesized in an aqueous medium. These compounds were then tested for the susceptibility to enzymatic degradation. The multiple-enzyme regime of -amylase, amyloglucosidase, and pullulanase was chosen for the evaluation. This combination of enzymes had been proven to degrade 99.5% of unmodified starch to glucose and hence was chosen for this study. It was found that even small amounts of subsituent caused a considerable decrease in the extent of degradation. The net extent of degradation decreased with increasing ds. Surprisingly, the amount of glucose from all three substituted substrates was quite similar, suggesting the effect small amounts of subtituent had on the enzymatic activity.     

Enzymatic Degradation and Aminolysis of Microbial Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) Single Crystals

Solution-grown single crystals of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] were hydrolyzed by polyhydroxybutyrate (PHB) depolymerase from Ralstonia pickettii T1. Enzymatic degradation proceeded from the edges of lamellar crystals, yielding serrated contour and small crystal fragments. Gel permeation chromatography analysis revealed that the molecular weights of the crystals decreased during enzymatic degradation, suggesting that the enzymatic hydrolysis of chain-folding regions at the crystal surfaces occurred in addition to the enzymatic degradation at crystal laterals or edges. After P(3HB-co-4HB) single crystals were aminolysed in 20% aqueous methylamine solution to remove the folded-chain regions and enzymatic degradation by lipase from Rhizopus oryzae to remove 4HB components at crystal surfaces of single crystal aminolyzed, it was found that a small amount (up to ca. 2 mol%) of 4HB component can be incorporated into the P(3HB) mother crystal lattice irrespective of the 4HB content.     

Influence of Carbonyl Fe on Degradation of Epoxy in Ozone Environment

Carbonyl iron/epoxy coatings are widely used in military as a radar absorbing coating (RAC). The behaviors of RACs under working environments are very important, especially in the new environments such as ozone appeared with widening of the application fields. The effects of ozone degradation on pure epoxy cured with anhydride and the influence of carbonyl Fe on the degradation of epoxy are studied. The results indicate that if the peak at 1,510 cm⁻¹ was used as the inner standard, the intensity of absorption peaks at 1,738, 1,247 and 1,182 cm⁻¹ increases with exposure time for pure epoxy resin, while for the carbonyl iron/epoxy coatings, the three peaks changes insignificantly with the exposure time. The results indicates the oxidation process begins at the hydroxyl and methyl groups, and finally ozonide and carbonyl are formed on the surface for pure epoxy, and epoxy is eroded gradually in depth by ozone. Carbonyl iron could hinder the meeting of ozone with epoxy with dilution or hindrance effect and could protect epoxy resin from ozone and thus delay the deterioration of the coating performance.     

Action of soil microorganisms on PCL and PHBV blend and films

Poly(hydroxybutyrate-co-valerate) (PHBV) and poly(ε-caprolactone) (PCL) PCL/PHBV (4:1) blend films were prepared by melt-pressing. The biodegradation of the films in response to burial in soil for 30 days was investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The PHBV film was the most susceptible to microbial attack, since it was rapidly biodegraded via surface erosion in 15 days and completely degraded in 30 days. The PCL film also degraded but more slowly than PHBV. The degradation of the PCL/PHBV blend occurred in the PHBV phase, inducing changes in the PCL phases (interphase) and resulting in an increase of its crystalline fraction.     

An Investigation into the Influence of C. moschata Leaves Extract on Physicochemical and Biological Properties of Biodegradable PCL/PLA Blend Film

Journal of Polymers and the Environment - Poly ε-caprolactone (PCL) synthesized by ring-opening polymerization method, and then it blended with polylactic acid (PLA). The blend was loaded with...     

Influence of TiO<Subscript>2</Subscript> Nanoparticles on the Crystallization Behaviour and Tensile Properties of Biodegradable PLA and PCL Nanocomposites

This paper investigated the influence of TiO₂ nanoparticles on the morphologies, as well as crystallization behaviour and kinetics, of neat PLA and PCL, and of these polymers in different PLA/PCL blends. We used transmission electron microscopy to evaluate the morphologies of the systems, while the crystallization behaviour and kinetics were investigated through differential scanning calorimetry (DSC). In addition to standard and modulated (StepScan) DSC analyses, the self-nucleation temperatures of neat PCL and PCL in the different nanocomposites were determined, followed by a self-nucleation and annealing thermal fractionation analysis of PCL crystallization and an Avrami isothermal kinetic analysis of PCL crystallization and PLA cold crystallization. We found that the nanoparticles were well dispersed, but only in the PLA phase of the blends, with only a few on the interface or in the PCL phase. They did nucleate and accelerate, and influence the mechanism of, the PCL crystallization in neat PCL, but had little influence on PCL crystallization in the blends. They strongly influenced the rate of cold crystallization of PLA, but had little influence on this parameter in the blends. The tensile properties were also determined, and changes in these properties could be related to the morphologies of the systems.     

高频超声波降解4-氯酚的反应机理及试验研究

探讨了高频超声波（1.7MHz)降解4-氯酚的反应过程和反应机理，研究了高频超声波降解4-氯酚的效果及4-氯酚的初始浓度，高级氧化方法（AOPs)等因素对降解效果的影响。试验结果表明，高频超声波降解4-氯酚为一级反应，超声波空化效应在降解过程中起主导作用。超声波与其他氧化方法联用可大大提高降解效率。具有良好的工业应用前景。     

A Comparison of the Effect of Silk Fibroin Nanoparticles and Microfibers on the Reprocessing and Biodegradability of PLA/PCL Blends

Journal of Polymers and the Environment - In this research, the effect of reprocessing on the properties of poly(lactic acid)/poly(ε-caprolactone) (PLA/PCL) blends reinforced with silk...     

Microscopic Visualization of the Enzymatic Degradation of Poly(3HB-co-3HV) and Poly(3HV) Single Crystals by PHA Depolymerases From Pseudomonas lemoignei

As a complement to previous studies of the enzymatic degradation of folded chain lamellar single crystals of polyhydroxyalkanoates, single crystals of a number of polyhydroxyalkanoates were partially degraded with depolymerases from Pseudomonas lemoignei and examined by transmission electron microscopy. Single crystals of bacterial poly(3-hydroxybutyrate-co-3-hydroxyvalerate), bacterial poly(3-hydroxyvalerate), and synthetic poly(3-hydroxybutyrate) with 88% isotactic diads were degraded using purified extracellular PHA-depolymerases from P. lemoignei: PHB-depolymerase A, PHB-depolymerase B, and depolymerases from recombinant E. coli: PHB-depolymerase PhaZ4 (PHB-depolymerase E), PHB-depolymerase PhaZl (PHB-depolymerase C), and PHB-depolymerase PhaZ5 (PHB-depolymerase A). In contrast to previous results with single crystals of bacterial PHB, the predominant effect observed with all crystals was a significant narrowing of the lamellae. This suggests an edge attack mechanism which because of lateral disorder of the crystals leads to a narrowing of the crystalline lamellae as opposed to the splintering effect previously observed. The model suggested for the degradation of single crystals of bacterial PHB by PHB-depolymerases is refined to include the effects of lateral disorder caused by the introduction of valerate or repeat units of opposite stereochemistry into the single crystal.     

Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation

Three high molecular weight (120,000 to 200,000 g mol^–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M _w) was in the range of 50,000 to 75,000 g mol^–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M _w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.     

电解法降解有机污染物机理及动力学的研究

对阳极电解催化降解有机污染物的机理进行了研究。结果表明 ,在电解过程中能够产生氧化能力极强的羟基自由基 (HO· ) ,使有机污染物以间接氧化的方式降解。用非线性最小二乘法对试验数据的分析表明 ,降解过程基本符合两步一级模型 ,并得到了水杨酸降解过程中的两步速率常数和 2 ,3-二羟基苯甲酸在 5 10 nm处的摩尔吸光系数     

胺液脱硫系统再生性能下降原因分析及对策

中国石化茂名分公司两套胺液集中再生装置出现异常,再生后贫液中ρ(H_2S)达到2.0~3.0 g/L,远高于1.2g/L的工艺设计值。通过在实验室模拟装置上考察新鲜脱硫剂的吸收和再生性能、分析工厂胺液脱硫系统贫液的杂质组成和来源、对比实验室净化前后的效果,查明胺液脱硫系统脱硫剂再生性能下降的原因。据此对工厂胺液脱硫系统提出相应的操作建议,包括采取胺液净化技术将系统热稳盐含量(w)从2.35%降至0.95%、规范操作以降低Na~+含量等措施,使得胺液脱硫系统在整改后的两个月运行中,贫液中ρ(H_2S)从原来的最高1.68 g/L降至0.66 g/L以下,达到胺液脱硫系统稳定运行的目的。     

波长与辐射强度对活性艳蓝KN -R光催化降解的影响

以TiO2为光催化剂,分别测定了365 nm和254 nm两种紫外光源波长及辐射强度对活性艳蓝KN-R模拟废水处理效果的影响.实验结果表明:在波长365 nm紫外光源照射2h后,活性艳蓝KN-R降解率达69.1％,活性艳蓝KN-R的降解可用二级反应速率方程拟合;在波长254nm紫外光源照射1h后,活性艳蓝KN-R降解率...     

Effect of Hydrothermal Polylactic Acid Degradation on Polymer Molecular Weight and Surface Properties

In the present work, polylactic acid, PLA, samples were degraded by hydrothermal treatment, and then their molecular weights, crystallinity, surface charges and compositions, were determined, respectively, by using viscometry, ¹H NMR, Differential Scanning Calorimetry (DSC), microelectrophoresis and Infra Red spectroscopy methods. The viscometry and ¹H NMR data indicate that the molecular weight, of the polymer, decreases after the hydrothermal treatment. However, the crystalline fractions of the PLA samples, as obtained from the DSC and X-ray data, were not altered after the hydrothermal treatment. Furthermore, the zeta potential data, as determined by microelectrophoresis, show for both non-degraded and degraded PLA, an increase of the polymer surface charge density with the pH of the aqueous phase. However, at acidic pH values, the surface charge density for the degraded PLA was higher as compared to the non degraded one. These differences in surface charge densities of the PLA samples were confirmed by Infrared study, according to which the spectra of degraded polymer show the appearance of carboxyl groups occurring at 1,600 cm⁻¹ at the polymer surface.     

MCM-41分子筛负载铁铈催化降解甲基橙

采用等体积浸渍法制备了负载型有序介孔Fe-Ce/MCM-41催化剂。研究了该催化剂降解甲基橙的适宜工艺条件,并采用XPS,XRD,TEM技术对该催化剂进行了表征。实验结果表明,该催化剂Fenton氧化降解甲基橙的较适宜工艺条件为:溶液pH 5.0、甲基橙溶液初始质量浓度100 mg/L、催化剂加入量2.0 g/L、H_2O_2浓度20 mmol/L,在此适宜条件下反应120 min时,甲基橙去除率接近100%。表征结果显示:Fe-Ce/MCM-41催化剂主要由铁、铈、氧、碳4种元素组成;铁与铈的摩尔比接近3∶1;铁和铈主要以Fe_3O_4和CeO_2的形态存在于催化剂表面。