Role of Urea on the Physico-Mechanical and Degradable Properties of Mercerized and Acid Hydrolyzed Coir (Cocos nucifera) Fibers Photocured with 1,6-Hexanediol Diacylate

Abstract

Coir fibers were modified with 1,6-hexanediol diacrylate (HDDA) by using ultraviolet (UV) radiation. Concentration of HDDA, soaking time, and radiation dose were optimized and found to be 30% HDDA in methanol along with photoinitiator Irgacure-500 (2%) and 120 min of soaking time the better performance registered as the optimum conditions, where polymer loading (PL) was 17% and tensile strength (TS) was 50%. Urea of different concentrations (0.5–2%) was incorporated with 30% HDDA to monitor its effect on the properties and 1% urea produced the enhanced PL (25%) and TS (82%). For the improvement of the properties, the fibers were subjected to surface treatment with alkali (5% potassium hydroxide) at various mercerizing times in hot and normal conditions. Among all the mercerized fibers, fibers treated with hot alkali for 6 h and cured under optimized condition demonstrated the maximum enhancement of PL (35.5%) and TS (130%). The fibers were also subjected to acid hydrolysis for different times with different acid (H₂SO₄) concentrations. Again the effect of urea (1%) on the properties of the pretreated fibers was scrutinized. Water uptake and degradable properties of the treated and virgin fibers were performed.     

A Surface Effect Associated with the Use of Oils Containing Zinc Dialkyl Dithiophosphate

It is shown that the operation of engines on crankcase oils containing appreciable amounts of zinc dialkyl dithiophosphate can increase the small-scale roughness of the lifter-foot surfaces. In addition, the small-scale roughness can be reduced by subsequent operation of the same engine parts on oils containing no zinc dialkyl dithiophosphate. This change in roughness coincides with a change in reflectivity that can be detected visually.

A similar effect of the additive has been demonstrated in a bench test machine. The increase in roughness which accompanies the operation on the additive-treated oil occurs rapidly and is maintained to high contact loads although some smoothing may occur at high loads.

The evidence suggests that the change in roughness results from a reaction of additive decomposition products with the metal surface. The mechanism responsible, however, is not completely understood.     

Development of Iron-Base Seal Materials for High Temperature Applications

This paper describes an experimental investigation of materials for use as high temperature rubbing seals.

The results of a comprehensive evaluation of the rubbing properties of commercial high speed tool steels are presented. It is shown that molybdenum steels have desirable high temperature seal characteristics. Tungsten steels, on the other hand, exhibit inferior properties. The best overall performance is demonstrated by a steel containing both molybdenum and tungsten in combination with cobalt.

These commercial tool steels are not effective over 1000 F; therefore, new material combinations were sought. Using powder metallurgy techniques, a series of iron-base alloys containing molybdenum and cobalt was studied. It was found that alloys containing from 5 to 20% of both molybdenum and cobalt exhibit excellent rubbing properties up to 1200 F, and in general, are superior to the tool steels tested.

Further testing of Fe-Mo-Co materials revealed that friction and wear are markedly dependent upon the test conditions. A minimum coefficient of friction was obtained with the highest surface speed (150 fps) and with the highest ambient temperature (1200 F).

The desirable rubbing properties of this family of materials are explained in terms of surface oxidation products which act as solid-film lubricants during high temperature rubbing.     

Oxidation Stability and Tribological Behavior of Vegetable Oil Hydraulic Fluids

The new generation of vegetable oil hydraulic fluids has a price advantage and provides field longevity comparable to synthetic esters at moderate temperature.

This article investigates the oxidation stability and tribological behavior of fully formulated vegetable oil hydraulic fluids. Differences in origin (canola, soybean, and sunflower oil) and the degree of unsaturation are studied. Modified ASTM D943 (Dry TOST) was found reliable to evaluate the impact on oxidative stability of various additive packages in vegetable oils. Tribological testing utilized laboratory hydraulic pumps such as the Vickers V 104C, Vickers 20VQ, and Vickers PFB-5 under a variety of temperatures, pressures, pump outputs, and speeds. The conditions of aging fluids were monitored by evaluation of TAN, viscosity, wear rate, and depletion of antioxidants. Voltammetric technique was applied to determine the concentration of antioxidant in systems. Based on analysis of antioxidant consumption, the main degenerative process in vegetable oils under demanding pump operations is similar to pyrolytic degradation, rather than oxidation.

By selecting the appropriate synergistic additive packages, a remarkable pump longevity can be obtained for each vegetable base stock studied.     

Feasibility of Observing Small Differences in Friction Mean Effective Pressure between Different Lubricating Oil Formulations Using a Small,Single-Cylinder Motored Engine Rig

The feasibility of using a motored single-cylinder 517 cc diesel engine to observe small frictional differences between oil formulations is investigated. Friction mean effective pressure (FMEP) is measured and compared for an SAE 10W-30 and an SAE 5W-20 oil in three stages of production: base oil, commercial oil without a friction and wear reducing additive, and fully formulated commercial oil. In addition, a commercial SAE 5W-30 engine oil is investigated. Friction mean effective pressure is plotted versus oil dynamic viscosity to compare the lubricant FMEP at a given viscosity. Linear regressions and average friction mean effective pressure are used as a secondary means of comparing FMEP for the various oil formulations. Differences between the oils are observed with the base oil having higher friction at a given viscosity but a lower average FMEP due to the temperature distribution of the test and lower viscosities reached by the base oil. The commercial oil is shown to have both a higher FMEP at a given viscosity and a higher average FMEP than the commercial oil without a friction and wear reducing additive. The increase in friction for the oil without a friction and wear reduction additive indicates that the operational regime of the engine may be out of the bounds of the optimal regime for the additive or that the additive is more optimized for wear reduction. Results show that it is feasible to observe small differences in FMEP between lubricating oil formulations using a small, single-cylinder motored engine.     

PLA—PEG共聚物的合成与性能研究

采用熔融缩聚法合成一定分子量的聚乳酸（PLA）,并用聚乙二醇（PEG）的聚氨酯预聚体进行扩链。研究了扩链反应条件对产物分子量的影响及产物的热性能。结果表明,扩链反应后PLA的分子量有大幅度提高,且扩链前后的PLA都具有良好的热稳定性。     

The study of epoxidized rapeseed oil used as a potential biodegradable lubricant

The application of epoxidized rapeseed oil as a biodegradable lubricant is described. The epoxidation treatment has no adverse effect on the biodegradability of the base stock. Epoxidized rapeseed oil has superior oxidative stability compared to rapeseed oil based on the results of both oven tests and rotary oxygen bomb tests. Moreover, the oxidative stability can be dramatically promoted by the addition of a package of antioxidants. The epoxidized rapeseed oil has better friction-reducing and extreme pressure abilities according to tribological investigations. Formation of a tribopolymerization film is proposed as explanation of the tribological performance of epoxidized rapeseed oil.     

生物降解型聚氨酯材料的研究进展

论述了国内外生物降解型聚氨酯材料的种类及其性能,以及在各个应用领域中的发展前景。     

Local antibiotic delivery systems for the treatment of osteomyelitis – A review

Osteomyelitis, an inflammatory process accompanied by bone destruction, is caused by infective microorganisms. The high success rates of antimicrobial therapy by conventional routes of administration in controlling most infectious diseases have not yet been achieved with osteomyelitis for several reasons. Local and sustained availability of drugs have proven to be more effective in achieving prophylactic and therapeutic outcomes. This review introduces osteomyelitis – its present options for drug delivery and their limitations, and the wide range of carrier materials and effective drug choices. Local drug delivery for osteomyelitis is a topic of importance for more than 20 years. Carrier materials used for local delivery of antibiotics may be classified as nonbiodegradable and biodegradable. Commonly used non biodegradable carrier materials are polymethyl methacrylate (PMMA), Acrylic beads, PMMA bone cement etc. and biodegradable materials are hydroxyapatite block, bioactive glass ceramics, collagen sponge, polylactide/ployglycolide implants. Both the systems release antibiotic at concentrations exceeding the minimum inhibitory concentrations (MICs) for the most common pathogens involved in osteomyelitis without causing any adverse systemic effects although non biodegradable beads are to be removed from the surgical site after completion of antibiotic release.     

On Green Design (Part 2): The Basic Premises for Green Design

In the second part of his green design series, Ken Yeang highlights how a prospective site can provide the essential springboard for eco-masterplanning. A full survey of the site and its sensitive development allows the built environment not only to be designed analogously with existing ecological systems, but also to reach out beyond the immediate footprint and to have a restorative effect on the surrounding area. Copyright © 2007 John Wiley & Sons, Ltd.