Mechanical And Tribological Properties Of Recycled Carbon Fiber Reinforced Polypropylene Composites

Recently, the use of carbon fiber waste is accepted as a wise approach to benefit the performance of the carbon fiber and considered as green effort for disposal management. This research is an effort to study the potential of recycled carbon fibers as reinforcement in polypropylene (PP) matrix especially for tribology application. The effects of fibers condition, fiber loading as well as chemical modifications on physical, mechanical and tribological properties of PP reinforced with recycled carbon fibers were studied. The composites were prepared via melt compounding using a Haake internal mixer at 180 ºC and rotor speed of 50 rpm for 10 minutes. This research is divided into three different studies; 1) effect of recycled carbon fibers condition (with or without uncured resins) on the physical and tensile properties at different carbon fiber (CF) loading of 0, 3, 5, 10, 13, 15 wt%, 2) effect of chemical modification using 3 and 5 wt% maleic anhydride (MA) on the tensile properties and 3) wear characteristics of recycled carbon fiber reinforced polypropylene composites at CF loading of 0, 0.5, 1.0, 3.0, 5.0, 7.0, 10.0, 13.0, 15.0, 20.0 wt%. In Study 1, the uncured resins on carbon fibers had proven to improve the interaction between reinforcement and matrix which manifested by increment in physical and mechanical properties with the optimum at 3 wt% fiber loading. In Study 2, the recycled carbon fibers were first pulverized into finer fibers before undergone oxidation in nitric acid and treatment with maleic anhydride. The treatment was observed to improve the physical and mechanical properties of the composites at low MA content of 3 wt% and proven to increase interaction at limited loading of fibers for only up to 1 wt%. The properties were supported by morphological analysis on the fracture surfaces observed by using Scanning Electron Microscopy and chemical analysis using Fourier Transform Infrared Spectroscopy. In Study 3, the composites with low carbon fiber loading of up to 3 wt% imposed higher resistance to dry sliding friction. In contrast, the increment of fiber loading at 5 wt% to 20 wt%, decreased the wear rate of the composites due to the formation of patchfilm and transfer film which accelerated with the MA treatment. The wear mechanism of the composites was for different fiber loading was proposed from morphological observation. As the conclusions, the composites showed promising self-lubricating properties with significant physical and mechanical properties

A Review on the Assessment of the Efficacy of Common Treatments in Polycystic Ovarian Syndrome on Prevention of Diabetes Mellitus

Objective: Polycystic ovarian syndrome (PCOS) is a common condition amongst women of reproductive age that can result in increased mortality and morbidity in women due to increased risk of diabetes mellitus and cardiovascular diseases. The aim of this systematic review was to assess the effectiveness of common treatments of PCOS on the predictors of diabetes in non-diabetic PCOS women. Materials and methods: An extensive search was performed on the publications in three medical databases including pubmed, scopus and google scholar from 1995 till 2017. The articles were screened based on their quality and included in this systematic review. A total of 25 articles including cohort, randomised controlled trial, review and meta-analysis were included in the review. Results: This systematic review revealed that the effect of lifestyle modification might be low in PCOS subjects due to high drop-out rate while the benefits of this intervention including weight and fat reduction may not be achieved by medical interventions. Metformin treatment may result in improvements in insulin sensitivity while its weight reduction effect is still not documented in PCOS subjects. Thiazolidendiones might be tolerated by the PCOS subjects and may result in similar effects as metformin but this effect should be documented by further studies. Conclusion: Combination of lifestyle modification with metformin or thiazolidinedions might improve the outcome of the prevention strategies. On the other hand this study revealed a different response to treatments in non-obese compared with obese PCOS subjects