Articles

In pressworking, large forces cut or deform a material, and specific shearing processes include blanking and piercing of metals, including aluminum. The force requirement is directly proportional to the ultimate shear strength, USS, of the sheared material. Nevertheless, shear strengths are not readily found in engineering references, especially for the multitude of aluminum grades and tempers. Thus, USS is often estimated from some percentage of the ultimate tensile strength. However, analyses for these estimates are lacking, and it is not clear how accurately the USS is predicted. In this review of 197 aluminum alloy data, it is shown that 60% of the ultimate tensile strength provides a satisfactory estimation for USS as the predicted shear strength is, on average, within 5.5% of the actual value. USS of weaker grades, as well as for all annealed material, tends to be underestimated while the strongest grades are overestimated. The availability of reliable aluminum shear strength data makes for more efficient pressworking.

The tensile strength is an imperative properties and essential indications consumers’ look out for in purchasing a quality fabric. The objective of this study was to examine key soap on tensile strength in three washing cycles of selected Printex fabrics in Ghana. Quantitatively, the study adopted both experimental and factorial research designs. Materials for the study consisted of three fabrics with black prints and white as base colour were purchased from the market. These three fabrics had the same designs but two had different fabric finishes and the third one had no finish (plain, embossed and plisse). Six yards each of the Printex black and white fabrics with embossed, plisse and a third one which did not have any special fabric finish were used for the study. Key soap purchased from the Ghanaian market, and standard soap from Ghana Standard Authority was used for the study. Purposive and simple random techniques were used to select materials for the study. The main research instrument for the testing tensile strength was Universal tensile testing machine. Data were analysed with both descriptive and inferential statistics. The one-way analysis of variance (ANOVA) was used to test the hypothesis formulated to guide the study. The study revealed that continuous washing had degrading effects on the tensile strength. The implication is that continuous washing weakens the internal strengths of fabrics which cause them to fail or weakens their resistance to stress test. The study also found that continuous washing had degrading effects on the tensile strength of the selected fabrics. It is recommended that the Ghana Standards Authority should encourage soap producers to get their chemical compositions as close to those of the standardised soap as possible.

Paper is widely used in packaging applications and is biodegradable and therefore perfectly safe as green packaging wrap for the environment. The hydrophilic nature of cellulose fibrils limits the water vapour and oxygen barrier properties of paper. To mitigate these limitations, paper is often associated with other materials, such as plastics, wax and aluminum, for achieving their good barrier properties. However, these materials suffer from serious environmental issues, as difficult and inefficient to recycle. Recently, cellulose nanofibre (CNF) based materials has been considered as an alternative to produce eco-friendly barrier materials. Existing techniques to prepare cellulose nanofibre films/sheets/composites/ laminates on the paper substrates are commercially not feasible and expensive. Therefore, other cost effective and readily implementable methodologies are required to achieve cellulose nanofibre barrier layers. In the present report, a novel approach is developed using spray coating technique to produce CNF materials with excellent barrier properties. Among many coating techniques, the spray coating has many advantages such as the production of even coating surface on the base sheet and contactless coating with the substrate. A laboratory scale spray coating of cellulose nanofibre suspension on a paper substrate was developed. When the cellulose nanofibre suspension concentration was varied from 0.5 to 1.5 wt. %, coat weight is increased from 2.9±0.7 to 29.3±6.9 g/m². As a result, the air permeability of composite was decreased 0.78±0.17 to <0.0030 µm/Pa.s. Scanning electron microscopy studies of spray coated CNF laminates on the paper confirms that the surface pores in the paper substrates are filled with sprayed cellulose nanofibre and forms a continuous film on the surface of the substrate. These are the probable reasons for the reduction of air permeability of composites. A rapid preparation technique to prepare free standing cellulose nanofibre films/sheets was also developed using a bench scale spray coating system. Cellulose nanofibre suspension with concentration ranging from 1 to 2 wt% was sprayed onto a stainless steel plate, which is moving on a conveyor at a velocity of 0.32 cm/sec and then air dried. The basis weight of produced cellulose nanofibre films is varied from 52.8±7.4 to 193.1±3.4 g/m². Processing time taken to prepare films was approximately 1.0 min, which is much less than processing times reported in the previous literature. Thus, the significant reduction in preparation time for producing the cellulose nanofibre sheet recommends that this spray coating technique can be utilized for the development of a scalable process for the fabrication of various cellulose based nanocomposite. Therefore, the laboratory scale spray coating confirms that the spraying could provide a platform for development of films/sheets/nanocomposite and also a CNF barrier layer on the base sheet. The future work is the development of a continuous spray coating of cellulose nanofibre on the base sheet and evaluation of mechanical and barrier properties spray coated barrier layers on the base sheet.