Akm Manzurul Alam

Mechanical properties of polypropylene composites: A review

There has been a growing interest in utilizing fibers as reinforcement to produce composite materials. Scientists prefer thermoplastic polymeric matrices than thermosets due to the low production cycle, lower cost of processing and high reparability of thermoplastics. Fiber-reinforced thermoplastic matrix composites have gained commercial success in the semistructural and structural applications. Various fibers are widely used as reinforcement in thermoplastic polypropylene (PP) matrix to prepare composites. Mechanical properties of fiber-reinforced PP composites (FRPCs) are studied by many researchers and few of them are discussed in this article. Various fiber treatments, which are carried out to improve the fiber–matrix adhesion to get improved mechanical properties, are also discussed in this article. This article also focuses on coupling agents and fiber loading which affect the mechanical properties of FRPCs significantly.

Preparation and characterization of natural silk fiber-reinforced polypropylene and synthetic E-glass fiber-reinforced polypropylene composites: a comparative study

Bombyx mori silk fiber-reinforced polypropylene (PP) matrix and E-glass fiber-reinforced PP matrix composites were fabricated using compression molding. The prepared silk/PP composite tensile strength (TS), bending strength (BS), and impact strength (IS) were 55.1u2009MPa, 56.3u2009MPa, and 17u2009kJ/m2, respectively. E-glass fiber-reinforced PP matrix composites were fabricated in the same way and TS, BS, and IS values of these composites were 128.7u2009MPa, 141.6u2009MPa, and 19u2009kJ/m2, respectively. Environmental degradation of the composites showed that silk/PP composites degrade faster. Other degradation studies like thermal aging and soil degradation tests also gave similar result.

Thermal, Mechanical and Morphological Characterization of Jute/Gelatin Composites

Jute fabrics/gelatin biocomposites were fabricated using compression molding. The fiber content in the composite varied from 20–60 wt%. Composites were subjected to mechanical, thermal, water uptake and scanning electron microscopic (SEM) analysis. Composite contained 50 wt% jute showed the best mechanical properties. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength of the 50% jute content composites were found to be 85 MPa, 1.25 GPa, 140 MPa and 9 GPa and 9.5 kJ/m2, respectively. Water uptake properties at room temperature were evaluated and found that the composites had lower water uptake compared to virgin matrix.

Effect of matrix modification by natural rubber on the performance of silk-reinforced polypropylene composites

Silk fiber-reinforced polypropylene (PP) matrix composites were prepared by compression molding. Tensile strength, tensile modulus, bending strength, bending modulus, impact strength (IS), and hardness of the prepared composite (20 wt%) were found to be 54.7 MPa, 1826.2 MPa, 58.3 MPa, 3750.7 MPa, 17.6 kJ/m2, and 95, respectively. To improve the biodegradable character of the composite, natural rubber (NR) was blended (10, 25, and 50 wt%) with PP using extruder, and thin films were prepared by heat press for composite fabrication. Silk fiber-reinforced blended PP plus NRbased composites (20 wt% fiber) were fabricated and characterized. It was found that the mechanical properties of the composites decreased with the increase of NR in PP but IS improved significantly. The IS improved by 48% when 25% NR was incorporated in PP for the silk-based composites. The water uptake property of the composites was investigated. Degradation of all the composites was studied using simulating weathering, thermal degradation, and soil degradation tests. The study makes it clear that mechanical properties of silk/PP composites are greater than those of silk/PP plus NR composites. But silk/PP plus NR composites are more degradable than silk/PP composites, that is, silk/PP composites retain their strength for a longer period than silk/PP plus NR composites.

The Preparation and Characterization of Silk/Gelatin Biocomposites

There is a growing interest in the use of composite materials. Silk fiber/gelatin biocomposites were fabricated using compression molding. The fiber content in the composite varied from 10–30 wt%. Composite containing 30 wt% silk showed the best mechanical properties. Tensile strength, tensile modulus, bending strength, bending modulus and impact strength, hardness of the 30% silk content composites were found 54 MPa, 0.95 GPa, 75 MPa and 0.43 GPa and 5.4 kJ/m2, 95.5 Shore A, respectively. Water uptake properties at room temperature, accelerated weathering aging, irradiation, thermomechanical analysis, and degradation in soil were carried out in this experiment.

Electrocautery Maze for Chronic Atrial Fibrilation in Patients Undergoing Mitral Valve Replacement

Aims : The present research aimed at to study of the compartmentalization of the posterior wall of the left atrium by using conventional electrocautery in order to reverting atrial fibrillation in patients undergoing mitral valve replacement Methods : This Quasi experimental study carried out in department of cardiac surgery, National Institute of Cardiovascular Disease (NICVD) and Hospital, Dhaka, Bangladesh. Total 64 patients are taken and then grouped into group A and group B. Each group contains 32 patients. Group A patients who underwent MVR with electrocautery maze Group B Patients who underwent for MVR only. All patients were evaluated continuous and with 12 lead ECG in immediate post-operative period, during discharge. Statistical analysis of the results was obtained by windows based computer software with statistical package for the social sciences program (SPSS version 21). Results : Freedom from atrial fibrillation in group A and group B was 28 (88.6%) and 6 (16.5%) patients at 1month follow up respectively and 11.5% and 75.0% patients AF persist in group A and group B respectively. 1 (3.1%) patient in group B was AF with slow ventricular rate. Conclusion :The finding of this study permit to conclude that the present study showed that the surgical treatment of atrial fibrillation with electrocautery, in mitral valve surgery, was capable of determining the reversion of this arrhythmia in a significant number of patients during a shortterm clinical follow-up, with low mortality and with low morbidity University Heart Journal Vol. 13, No. 2, July 2017; 46-49

Clinical Outcomes for Radial Artery Versus Saphenous Vein in Coronary Artery Bypass Graft Surgery

Aims : The aim this study was to see the clinical outcome of coronary artery bypass grafting (CABG) in patients of coronary artery disease and to compare the patients revascularisedwith left internal mammary artery (LIMA) and radial artery (RA) group with LIMA and reverse saphenous venous group(RSVG) group. Methods :Between March 2011 and November 2015, 200 patients underwent isolated CABG and were randomized in 1:1 fashion to receive either LIMA and RA grafts or LIMA and SVGs.All patients were operated in department of cardiac surgery, National Institute of Cardiovascular Disease (NICVD) and Hospital, Dhaka, Bangladesh and Al Helal Specialized Hospital, Mirpur- 10, Dhaka.Written consent was obtained from all patients prior to the procedure. Patients were followed for 4 years since index surgery for the composite of cardiovascular mortality, non-fatal myocardial infarction and need for repeat myocardial revascularization (either surgical or percutaneous). Data were collected either by phone or during visits. The data were entered into an electronic database (Access, Microsoft) and analyzed using the SPSS 16.0 software (SPSS Inc.). Results : This study reports on our series of 200 patients undergoing isolated, primary CABG using LIMA grafting and the SVG in one group, and RA grafting as the second conduit in the second group. Our data indicate that there is no difference in the long-term clinical outcome between the patients in whom RA or SVG is used as a second conduit, beside LIMA. Conclusion : In this small randomized study our data indicate that there is no difference in the 4 year clinical outcomes in relatively young patients between those having a RA or a saphenous vein graft used as a second conduit, beside LIMA, for surgical myocardial revascularization. University Heart Journal Vol. 13, No. 1, January 2017; 21-25

Preservation of Posterior Mitral Leaflet in Mitral Valve Replacement: Effect on Left Ventricular Geometry with Immediate Outcome.

Bcakground: Preservation of the posterior mitral leaflet and subvalvular structures during mitral valve replacement (MVR) preserve left ventricular geometry and function. We evaluated the effect of preservation of subvalvular structures during mitral valve replacement on LV ejection fraction (LVEF). Methods: Total 60 patients were taken and then grouped into group A and group B. Group A include patients of MVR with preservation of posterior leaflet and subvalvular structure, Group B without preservation of subvalvular structures. All patients were evaluated before operation, at discharge, and at 3 months follow-up. Left ventricular function was assessed by ventricular ejection fraction (LVEF). Results: Preoperative LV ejection fraction was 58.3±11.0% and 56.6±8.4% in Group A and Group B respectively. Post-operative mean LVEF at discharge was found 44.2±5.1% in group A and 37.3±4.8% in group B. Observation at three months follow-up showed that mean LVEF was 49.0±4.7% in group A and 39.6±4.7% in group B. Conclusion: Left ventricular function is better maintained when MVR is done preserving posterior leaflet and subvalvular structure. Cardiovasc. j. 2018; 11(1): 39-41

Synthesis and characterization of polyethylene oxide (PEO)—N,N-dimethylacrylamide (DMA) hydrogel by gamma radiation

AbstractNovel polyethylene oxide (PEO)/N,N-dimethylacrylamide (DMA) blend hydrogel (PD hydrogel) has been prepared by applying gamma radiation on aqueous mixture of PEO and DMA. Different concentrations of DMA have been blended with aqueous solution of PEO and then gamma radiation of different doses was applied to form the hydrogels. The synthesized hydrogels were characterized using Fourier transform infrared-attenuated total reflection spectroscopy (FTIR-ATR) and scanning electron microscopy (SEM). The effect of different radiation doses, concentration of monomers on the properties of prepared hydrogel (PD hydrogel), such as gel content, swelling behavior, and mechanical properties (Tensile strength) was investigated thoroughly. Results showed that hydrogels were formed at the experimental conditions without the use of any external cross-linker. All the prepared hydrogels showed a significantly larger swelling ratio and improved mechanical strength.n Graphical abstractNovel hydrogels were prepared by applying gamma radiation on a mixture containing commercially available polymer and monomer.