Effects Of Ozone On Biodegradable Dissolved Organic Carbon And Heterotrophic Plate Counts In The Distribution System

The impacts of ozone dose in the formation of biodegradable dissolved organic carbon (BDOC) were studied at the North Bay Regional Water Treatment Plant (NBR). Increasing the ozone to total organic carbon ratio to 0.45 (mg/mg) resulted in the formation of BDOC. Sedimentation and filtration/adsorption were effective in removing BDOC to non-measurable levels prior to the water entering the distribution system. Data from an on-going distribution system monitoring program indicate no discernible adverse impacts on microbiological parameters from using ozone during water treatment. Heterotrophic plate count (HPC) levels were similar before and after the use of ozone. Maintaining chlorine residual levels above 0.3 mg/L appears to be important for controlling HPC levels.     

C-21 dicarboxylic acids in soap and detergent applications

A unique polycarboxylic acid, 5(6)-carboxy-4-hexyl-2-cyclohexene-1-octanoic acid, has been available commercially for over 15 years. A new high-purity (>97%), light-color version of the C-21 dicarboxylic acid has been developed recently. Soaps of the C-21 dicarboxylic acid can be used as hydrotropes to increase the solubility of nonionic surfactants in aqueous solutions containing builders and/or anionic surfactants. Since these soaps are anionic fatty acid derivatives, they reduce the surface tensions of formulations, thus improving detergency. The nontoxic and biodegradable nature of this dicarboxylic acid makes it an attractive formulation component. This paper outlines application evaluations of the soaps prepared from the C-21 dicarboxylic acids. These evaluations demonstrate how the soaps interact with nonionic surfactants or pine oil to provide clear formulations, how they wet cotton skeins in neutral to highly alkaline solutions, and how they inhibit gel formation when preparing high-solids fatty acid soap solutions. Furthermore, the preparation and characterization of the soaps of the C-21 dicarboxylic acid products are discussed. Mass-balance equations describe the preparation of aqueous soap solutions at any given concentration. Characterization of the resulting soap solutions includes acid number, pH, color, color stability, foam stability, surface tension as a function of concentration, and hard-water compatibility.     

Isothermal crystallization in PCL/clay nanocomposites investigated with thermal and rheometric methods

Nanocomposites based on biodegradable poly(ε-caprolactone), (PCL) and organically modified layered silicates (organoclay) were prepared by melt mixing. The isothermal crystallization of PCL/clay nanocomposites at different clay concentrations (from 0.1 to 10 wt%) were investigated by differential scanning calorimetry (DSC) and rheometry in dynamic tests. The results showed that the well dispersed organoclay platelets acted as nucleating agents in the PCL matrix, as confirmed by a remarkable reduction of the crystallization half-time, t_1/2. This effect was most pronounced at very low clay concentrations. In particular, in composites with 0.4% of clay, t_1/2 was one order of magnitude lower than the pure polymer. The heating thermograms, performed on PCL and on PCL/clay after isothermal crystallization showed a reduction of the melting temperature with the increase of the clay content, suggesting that the degree of perfection of the crystals and the degree of crystallinity were affected by the restricted mobility of the chains, which did not allow the growth of well developed lamellar crystals. The rheological measurements confirmed the effect of clay on crystallization kinetics. The evolution of G′ and G″ vs. time was correlated to the clay concentration and to the development of the crystalline phase during isothermal experiments.     

pH/temperature sensitive poly(ethylene glycol)-based biodegradable polyester block copolymer hydrogels

Novel pH and temperature sensitive biodegradable block copolymers composed of poly(ethylene glycol) (PEG), polyglycolide (GA), ?-caprolactone (CL) and sulfamethazine oligomers (OSMs) were synthesized by ring opening polymerization and 1,3-dicyclohexyl-carbodiimide (DCC) mediated coupling reactions. Their physicochemical properties in aqueous media were characterized by ¹H NMR spectroscopy and gel permeation spectroscopy. The sol-gel phase transition behavior of OSM-PCGA-PEG-PCGA-OSM block copolymers was investigated both in solution and injection to PBS buffer at pH 7.4 and 37 °C. Aqueous solutions of OSM-PCGA-PEG-PCGA-OSM changed from a sol to a gel phase with increasing temperature and decreasing pH. The sol-gel transition properties of these block copolymers are influenced by the hydrophobic/hydrophilic balance of the copolymers, block length, hydrophobicity, stereoregularity of the hydrophobic components within the block copolymer, and the ionization of the pH functional groups in the copolymer, which depends on the environmental pH. Degradation of the triblock and pentablock copolymers at 37 °C (pH 7.4), and at 0 °C and 5 °C both at pH 8.0, was investigated. It was demonstrated here using the in vitro test method, that the anticancer agent paclitaxel (PTX) could be loaded and released by the pH and temperature sensitive OSM-PCGA-PEG-PCGA-OSM block copolymer, such that this could be used as a suitable matrix for subcutaneous injection in drug delivery systems.     

Gelation and degradation characteristics of in situ photo-crosslinked poly(l-lactide-co-ethylene oxide-co-fumarate) hydrogels

The objective of this work was to determine the gelation kinetics, extent of swelling, sol fraction, and degradation kinetics of photo-crosslinked poly(l-lactide-co-ethylene oxide-co-fumarate) (PLEOF) hydrogels, with N-vinyl-2-pyrrolidone (NVP) crosslinker, as a function of composition as well as the time and intensity of UV radiation. The gelation process was monitored by in situ rheometry. The crosslinking was shown to be facilitated by increasing NVP concentration up to a certain value above which the hydrogel shear modulus did not increase with additional amount of NVP. Increasing the hydrophobicity of PLEOF macromer resulted in a decrease in the hydrogel swelling ratio and increase in sol fraction which was due to a reduction in the apparent reactivity of the PLEOF fumarate units. The degradation characteristics of PLEOF hydrogels depended on the ratio of PLA to PEG with PLEOF 30/70 (30% lactide) having the highest degradation rate.     

Synthesis and properties of novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) and poly(ethylene glycol)

Novel biodegradable triblock copolymers of poly(5-methyl-5-methoxycarbonyl-1,3-dioxan-2-one) (PMMTC) with poly(ethylene glycol) (PEG), PMMTC-b-PEG-b-PMMTC, were synthesized by the ring-opening polymerization of MMTC in bulk, using the dihydroxyl PEG as initiator and Sn(Oct)₂ as catalyst. The triblock copolymers with different compositions were characterized by IR and ¹H NMR, their molecular weight was measured by gel permeation chromatography (GPC). The results showed that the molecular weight of triblock copolymers increased either with the increase of the molar ratio of MMTC in feed while the PEG chain length kept constant, or by lengthening the backbone chain of PEG block with the same ratio of MMTC in feed. The hydrophilicity of copolymers was greatly improved by incorporation of PEG block into polycarbonate. The in vitro hydrolytic/enzymatic degradation and controlled drug release properties of the triblock copolymers were also investigated.     

可生物降解润滑油基础油低温性能研究

回顾了矿物润滑油降凝机理的发展历史，指出了传统降凝机理在解释生物可降解润滑油低温流变的局限性，并通过试验来研究生物可降解润滑油的低温流变机理。     

Lifetime prediction of biodegradable polymers

The determination of the safe working life of polymer materials is important for their successful use in engineering, medicine and consumer-goods applications. An understanding of the physical and chemical changes to the structure of widely-used polymers such as the polyolefins, when exposed to aggressive environments, has provided a framework for controlling their ultimate service lifetime by either stabilising the polymer or chemically accelerating the degradation reactions. The recent focus on biodegradable polymers as replacements for more bio-inert materials such as the polyolefins in areas as diverse as packaging and as scaffolds for tissue engineering has highlighted the need for a review of the approaches to being able to predict the lifetime of these materials. In many studies the focus has not been on the embrittlement and fracture of the material (as it would be for a polyolefin) but rather the products of degradation, their toxicity and ultimate fate when in the environment, which may be the human body. These differences are primarily due to time-scale. Different approaches to the problem have arisen in biomedicine, such as the kinetic control of drug delivery by the bio-erosion of polymers, but the similarities in mechanism provide real prospects for the prediction of the safe service lifetime of a biodegradable polymer as a structural material. Common mechanistic themes that emerge include the diffusion-controlled process of water sorption and conditions for surface versus bulk degradation, the role of hydrolysis versus oxidative degradation in controlling the rate of polymer chain scission and strength loss and the specificity of enzyme-mediated reactions.     

Contamination of animal feed and food from animal origin with mineral oil hydrocarbons

Oils and fats used for the production of animal feed can become contaminated with mineral oil material originating from gas oils (C₁₈-C₃₅) or synthetic oils (poly alpha olefins, C₂₅ to beyond C₄₅). An important cause is assumed to be the discharge of waste oils, such as motor oil and hydraulic oils. Mineral oil material was analysed by on-line LC-GC-FID directly in the fat or in a raw extract from animal feed or foodstuffs. In Switzerland in summer/autumn 1999 concentrations in oils and fats for feed production were often found to be between 100 and 1000mg/kg. In the feeds, the average concentration was around 100mg/kg with values ranging up to a maximum of 1000mg/kg; few samples were free of contamination. In animal body fat, the average concentration determined in summer 1999 was 25mg/kg, with a maximum of 150mg/kg, although in samples from December 1999, contamination was substantially lower. In the fat phase of eggs, the average concentration was 30mg/kg, with a maximum of 80mg/kg. Paraffin oil is used for feed production, which may account for part of the contamination problem (e.g. eggs).     

Effect of different drying methods on chemical and molecular structure of heteropolysaccharide–protein gum from durian seed

The functional properties and biological aspects of a natural biodegradable biopolymer depend on its chemical and molecular structure. In this study, the effect of different drying processes on the chemical and molecular structure of the natural biodegradable biopolymer from durian seed was investigated. The chemical structure was analyzed by assessing the carbohydrate profile, protein, amino acid composition, moisture, and ash. Molecular weight (M_w), number average molecular weight (M_n), M_w/M_n ratio and mass recovery were assessed by using a size-exclusion chromatography coupled to multi angle laser light-scattering (SEC-MALS). The present study revealed that main monosaccharides in the chemical structure of differently dried durian seed gums were galactose (50.1–64.9%), glucose (29.4–45.7%%), arabinose (0.11–0.89%), and xylose (0.019–0.86%). The protein analysis indicated the presence of a low amount of the protein fraction (3.2–3.9%) in the chemical structure of the biopolymer from durian seed. The most abundant amino acids in the chemical structure of durian seed gum were leucine (31.78–43.02%), lysine (6.23–7.78%), aspartic acid (6.45–8.58%), glycine (6.17–7.27%), glutamic acid (5.43–6.55%), alanine (4.60–6.23%), and valine (4.49–5.52). The current study exhibited that the biodegradable biopolymer from durian seed was a heteropolysaccharideprotein complex with medium M_w ranging from 1.06 × 10⁵ to 1.15 × 10⁵ (g/mol).