Role of promaxon-d in controlling tribological performance of cu-free brake pads

Copper appears to be an indispensable ingredient of non-asbestos organic (NAO) brake friction materials owing to its multifunctionality. However, recent findings proved it as a threat to aquatic life and efforts were initiated worldwide over the last few years to find a substitute for it. Recently, the authors’ group had reported on the potential of particulate Promaxon-D (hydrated calcium silicate), a porous material for enhancement of noise–vibration (NV) performance of Cu-free brake pads. It was felt necessary to investigate how Promaxon-D (PD) contributes to controlling tribo-performance of brake pads since this aspect is most important for the brake friction materials. A series of five types of brake pads was developed by keeping parent composition fixed and varying the theme ingredient PD content from 0–20 wt.%. The tribo-performance was evaluated on a full-scale brake inertia dynamometer as per the JASO C406 test standards. The increase in PD contents led to a reduction in density, hardness, and thermal conductivity while an increase in porosity and compressibility. With the increase in PD contents, almost all tribo properties such as average μ, fade ratio, and recovery ratio got enhanced, sensitivity of μ for pressure, speed, and temperature lowered but at the cost of wear resistance. Finally, the worn surfaces of pads and discs were observed under a scanning electron microscope equipped with energy dispersive X-ray (SEM-EDX) to find out the presence of various elements at the contact zone and to monitor specific topographical events responsible for wear mechanism

A clinical study of acute intestinal obstruction in adults-based on etiology, severity indicators and surgical outcome

Background: Patients with bowel obstruction still represent some of the most difficult and vexing problems that surgeons face today. While the adage, “never let the sun rise or set on a bowel obstruction” remains true, there has been a trend towards selective non-operative management of this problem. Aims and objectives were to study the various causes and modes of presentation of intestinal obstruction and to evaluate the importance of different severity indicators of obstruction with early recognition, diagnosis and thus timely abdominal exploration.Methods: 2 years prospective study conducted in PDMMC college, Amravati, Maharashtra, India, from September 2013 to September 2015. Each intestinal obstruction patient was evaluated with specific severity indicators, scored and then analyzed.Results: The commonest cause of intestinal obstruction in adults in this study series was adhesions in 33.33% cases. Other causes were mesenteric ischaemia, i.e. 7 (11.67%), Koch’s abdomen, i.e. 5 (8.33%), sigmoid volvulus, i.e. 5 (8.33%) and carcinoma, i.e. 5 (8.33%). Resection anastomosis was most commonly performed procedure in 45.7 % cases, followed by adhesiolysis in 14% patients. 66.66% patients having a score less than 3 were managed conservatively, 95.83 % having a score of 3 or more where operated on.Conclusions: The evaluation of patients endeavours not only to confirm the diagnosis but also to determine the need for and timing of surgery. Certain severity indicators and scoring systems can help to optimize this timing of surgery and prevent mortality

Strengthening of a Fibre-Matrix Interface: A Novel Method Using Nanoparticles

The surface of carbon fabric (CF) was treated with nanoparticles (NPs) of Ytterbium fluoride (YbF3) (40‐80nm size) in various amounts (0, 0.1, 0.3 and 0.5wt%) to improve its wettability with a Polyetherimide (PEI) matrix. The effect of treatment on the fibres of the CF was also studied by adhesion testing and fibre tow tension testing. An improvement in wettability with PEI and a slight reduction in the tensile strength of the CF was observed in these tests. Fourier transform infrared‐attenuated total reflectance spectroscopy (FTIR‐ATR) indicated the addition of functional groups on the fabric after treatment. Micro‐ Raman spectroscopy (MRS) showed a slight distortion in the structure of the CF due to the treatment. Increased roughness of the fibre surface and adhesion of NPs on the fibre surface were observed by field emission scanning electron microscopy (FESEM). Composites were developed based on untreated and surface‐treated CFs by impregnation techniques. The composites were analysed for interlaminar shear strength (ILSS) and a maximum improvement of 61% was observed for the 0.3% concentration of YbF3, followed by a slight decline in ILSS, indicating that it was the optimum dose

Influence of increasing amount of attapulgite on the performance properties of Cu-free brake-pads

Copper is almost inevitable functional filler in the brake-material and efforts to replace it are continuing since it is now known as a hazard to the aquatic life. It is always desirable to search for ingredients for Cu-free brake-pads, which will be beneficial for friction-related properties and especially fade resistance. Attapulgite, is a mineral which was proven to be an excellent substitute for asbestos in brake-pads long back. However, hardly anything in details is reported on its exact role in controlling tribo-properties of friction materials (FMs). It was of interest, if it can be helpful in enhancing the performance of Cu-free FMs. Hence, in this work a series of brake-pads (five types) was formulated and developed with increasing amount of attapulgite (0, 5, 10 and 15 wt. %) by compensating with inert barite particles in Cu-free FMs. The parent composition was fixed and instead of Cu powder, 10 wt.% stainless steel powder was used. One more type of pads was also developed containing Cu and attapulgite (10 wt. % each) just to compare its performance with that containing 10 % stainless steel powder and attapulgite, (10 wt. % each) keeping every other ingredients in parent composition as constant. The pads were characterised for physical, chemical and mechanical properties. The tribological characteristics were evaluated using full-scale inertia dynamometer as per JASO-C-406 standards under dry condition. The results revealed that the attapulgite exhibited slightly lubricating properties by reducing average μ with increasing amount. However, it helped to increase the wear resistance to small extent, but at the cost of deterioration in some beneficial properties such as fade resistance, fluctuations in μ. Overall, its inclusion in Cu-free brake-pads did not prove beneficial as expected