Impact of posture and upper-limb muscle activity on grip strength

Purpose. The current research was carried out to determine grip strength (GS) with change in posture and upper-limb muscle activity of manual workers and investigate the impacts of these changes. Methods. For the current research, 120 male and 80 female participants were selected and GS was assessed using a digital hand grip dynamometer in various conditions. Results. The outcomes showed that male participants had higher GS as compared to female participants. Maximum GS was found in a standing posture with the fixed forward shoulder at 45°, elbow at 90° and a neutral position of the wrist and forearm for all participants. Conclusions. Higher values of GS were attained in standing postures which may result in attainment of higher performance levels by the workers. The outcomes justify the importance of correct postures during manual work in industries employing traditional methods.     

Development of Lignin and Nanocellulose Enhanced Bio PU Foams for Automotive Parts

The green rigid polyurethane (PU) foam has been developed with 100 % soy polyol after optimization of formulation ingredients and lignin has been introduced and isocyanate content reduced in the green rigid PU foam. The cellulosic nanofibers have also been successfully incorporated and dispersed in green rigid PU foam to improve the rigidity. The influence of nano cellulose fiber modification (enzymatic treatment, hydrophobic modification with latex) on the foam density, open cell content, foam raise height, water vapor, and mechanical properties of rigid PU foam were studied. The foamed structures were examined using scanning electron microscopy to determine the cell size and shape due to the addition of cellulosic nanofibers. The odor test were performed to evaluate the odor concentration 100 % soyol based PU foam including lignin and nanofiber and compared to 100 % synthetic based polyol PU foam. The experimental results indicated that the compression and impact properties improved due to the modification of nano cellulosic fibers. The odor concentration level of nanofiber reinforced rigid PU foam reduced significantly compared to 100 % PU foam due to the replacing of isocyanate content. It can be said that with an appropriate combination of replacing isocyanate by lignin and addition of nanofiber, rigid PU foam properties could be improved.     

Synthesis of Soy-Polyol by Two Step Continuous Route and Development of Soy-Based Polyurethane Foam

Soy-polyol has been synthesized via a low energy two-step continuous route thus avoiding intermediate steps and chemicals. The functional groups of soy-polyol thus produced were identified by Fourier transform infrared (FTIR) spectroscopy which confirmed the cleavage of the double bonds, the formation of new epoxy linkages and the presence of hydroxyl groups. The change in chemical structure and physical properties of the soy polyol was further characterized and the results indicated a successful conversion with reduced unsaturation, increased hydroxyl number and increased viscosity. Polyurethane foam was prepared from soy-polyol using isocyanate and thermogravimetric analysis was used to study its thermal decomposition behaviour. Multiple transitions were identified in relation to depolymerization and bond dissociation. Density and compressive strength of the soy-foam were found to be satisfactory. An investigation of microstructure of soy foam by scanning electron microscope and X-ray computed tomography revealed the internal cell morphology and cell structure.     

Effect of Common Chemical Treatments on the Process Kinetics and Mechanical Properties of Flax/Epoxy Composites Manufactured by Resin Infusion

Chemical treatments are widely employed to improve the fiber-matrix adhesion in composites based on eco-friendly fibers such as flax. To better understand the influence of these treatments on processing behavior, this study characterized the surface chemistry and morphology of woven flax fabrics treated by acetone, alkaline, silane and diluted epoxy. Flax/epoxy composites were then manufactured by resin infusion and the flow front and preform thickness evolution was monitored. The alkaline treatment was shown to result in a 50 % increase in equivalent permeability due to an increase in porosity which led to a decrease in flexural properties. The processing results were found to be in good agreement with predictions of a 1-dimensional model. This study suggests that infusion times are not considerably affected by the observed changes in surface energy. However, other implications of the treatments such as an increase in fibrillation can alter the infusion times significantly.

     

Cellulose–Polymer Based Green Composite Fibers by Electrospinning

Green composite fibers (339?C612?nm in diameter) have been developed from wood pulp, acetylated wood pulp and polyethylene oxide under various concentrations by electrospinning process. A polymer solution concentration of 7 wt% with 5 wt% wood pulp have been found to produce uniform composite fibers. Scanning electron microscopy micro-images demonstrated that composite fibers diameter and morphology depended on the processing parameters, such as solution concentration and molecular weight of polymer. Transmission electron microscopy and laser confocal microscopy observations indicated that the acetylated wood was well dispersed and oriented along the length of composite fibers axis. X-ray diffraction studies revealed that the structure of electrospun composite fibers became more non-crystalline.     

Non-powered hand tool improvement research for prevention of work-related problems: a review

Purpose. In lower-middle-income countries, most of the work is performed manually using non-ergonomic hand tools which results in work-related health problems. Using hand tools designed in line with ergonomic principles may play an important role in reducing work-related health concerns significantly. Methods. Scientific databases (PubMed, EBSCOhost) and e-publishers were searched for articles from 1985 to 2015 using the following keywords: ‘hand tool’, ‘ergonomics’, ‘usability’ and ‘design’. After applying selection criteria to 614 articles, 58 articles related to the physical design of hand tools were selected. Results. Seventeen articles were related to hand tool improvement in the manufacturing sector. Musculoskeletal disorders were found to be the most frequently occurring work-related health problems. Most of the articles focused on product and qualitative variables for improvement in hand tools, while few articles considered human and task variables. Conclusions. Literature shows that hand tool improvement studies have been given less importance in low-income and lower-middle-income countries. However, some work of significance is reported in the agriculture sectors of these countries. Hence, it is concluded that ergonomic intervention in hand tools is much needed for those industries which employ traditional methods of working.     

Pulling force prediction using neural networks

Purpose. In ergonomics and human factors investigations, pulling force (PF) estimation has usually been achieved using various types of biomechanical models, and independent approximation of PF was done with the help of upper extremity joints. Recently, multiple regression methods have gained importance for task-relevant inputs in predicting PF. Artificial neural networks (ANNs) also play a vital role in fitting the data; however, their use in work-related biomechanics and ergonomics is inadequate. Therefore, the current research aimed to accomplish comparative investigation of ANN and regression models by assessing their capacity to predict PF values. Methods. Multipositional PF data were acquired from 200 subjects at three different handle heights and body locations. ANN and regression models were formed using a random sample of three subsets (75% training, 15% selection, 10% validation) for proving the outcomes. Results. The comparison of ANN and regression models shows that the predictions of ANN models had a profoundly explained variance and lower root mean square difference values for the PF data at three handle heights. Conclusions. These outcomes advise that ANNs offer a precise and robust substitute for regression methods, and should be considered a useful method in biomechanics and ergonomics task assessments.     

Microwave Assisted Short-Time Alkaline Extraction of Birch Xylan

Efficacy of microwave energy for the extraction of xylan from birch wood as an alternative to conventional method of extraction was investigated. Effect of irradiation time and microwave power input on the solubilization of wood and yield of extracted xylan was studied. The maximum yield of xylan obtained at the higher power level was significantly lesser compared to the lower power level indicating the molecular degradation of the polymer. The highest yield of xylan (60 % of the original xylan) was obtained at the lowest power level studied, 110 W, for an irradiation time of 10 min. Comparison with conventional extraction showed that 10 min of microwave extraction provided a similar wood dissolution to that at 90 °C for 1.5 h, but with a higher yield of xylan. Characterization of the precipitated xylan indicated that the extracted xylan contained 68–88 % of xylose with the major chemical structure consisting of a linear backbone of (1-4) β-d-xylopyransoyl residues. Molecular mass of the extracted xylan indicated that the xylan extracted using microwave contained 60–70 % of high molecular weight fraction, and about 30–40 % of low molecular weight fraction, whereas xylan extracted using conventional method showed a reverse trend. Molecular mass of non-aggregated xylan was reported to be 6,000 Da (in terms of dextran equivalents). Crystallinity of wood fibers increased irrespective of the method of extraction indicating no degradation of the strength of the fibers occurred during the extraction.     

Carbon storage potential in natural fiber composites

The environmental performance of hemp based natural fiber mat thermoplastic (NMT) has been evaluated in this study by quantifying carbon storage potential and CO₂ emissions and comparing the results with commercially available glass fiber composites. Non-woven mats of hemp fiber and polypropylene matrix were used to make NMT samples by film-stacking method without using any binder aid. The results showed that hemp based NMT have compatible or even better strength properties as compared to conventional flax based thermoplastics. A value of 63 MPa for flexural strength is achieved at 64% fiber content by weight. Similarly, impact energy values (84–154 J/m) are also promising. The carbon sequestration and storage by hemp crop through photosynthesis is estimated by quantifying dry biomass of fibers based on one metric ton of NMT. A value of 325 kg carbon per metric ton of hemp based composite is estimated which can be stored by the product during its useful life. An extra 22% carbon storage can be achieved by increasing the compression ratio by 13% while maintaining same flexural strength. Further, net carbon sequestration by industrial hemp crop is estimated as 0.67 ton/h/year, which is compatible to all USA urban trees and very close to naturally, regenerated forests. A comparative life cycle analysis focused on non-renewable energy consumption of natural and glass fiber composites shows that a net saving of 50 000 MJ (3 ton CO₂ emissions) per ton of thermoplastic can be achieved by replacing 30% glass fiber reinforcement with 65% hemp fiber. It is further estimated that 3.07 million ton CO₂ emissions (4.3% of total USA industrial emissions) and 1.19 million m³ crude oil (1.0% of total Canadian oil consumption) can be saved by substituting 50% fiber glass plastics with natural fiber composites in North American auto applications. However, to compete with glass fiber effectively, further research is needed to improve natural fiber processing, interfacial bonding and control moisture sensitivity in longer run.     

Fungal-modification of Natural Fibers: A Novel Method of Treating Natural Fibers for Composite Reinforcement

Growing interest in green products has provided fresh impetus to the research in the field of renewable materials. Plant fibers are not only renewable but also light in weight and low in cost. Polymer composites manufactured using them find applications in diverse fields such as automobiles, housing, and furniture. However, their hydrophilic nature and inadequate adhesion with matrix limits their use in high performance applications. In this study, a novel method for improving adhesion characteristics of natural fibers has been developed. This method is carried out by treating hemp fibers with a fungus: Ophiostoma ulmi, obtained from elm tree infected with Dutch elm disease. Treated fibers showed improved acid–base characteristics and resistance to moisture. Improved acid–base interactions between fiber and resin are expected to improve the interfacial adhesion, whereas improved moisture resistance would benefit the durability of the composites. Finally, composites were prepared using untreated/treated fibers and unsaturated polyester resin. Composites with treated fibers showed slightly better mechanical properties, which is most probably due to improved interfacial adhesion.