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This work aims to predict the noise reduction coefficient (NRC) of nonwoven layers produced from Estabragh/polypropylene blends of fibers. Estabragh is a natural hollow fiber which can be expected to have excellent sound insulation properties. In addition to the investigation of Estabragh’s unique properties in association with the sound absorption capability, the effects of some predictor variables such as blend ratio, punch density, and areal density (g/m2) on the acoustical performance of the produced nonwoven samples also have been studied through this research. For this achievement, a simplex lattice design was used in which the mixture-process crossed regression models with two mixture components and two process variables (punch density and areal density) were built to predict the NRC values of samples. Statistical analysis steps were implemented using Design-Expert statistical software. The correlation coefficient between the predicted and measured values of NRC was found to be 0.98, which confirmed the validity of the developed regression model. It was found that the noise absorption behavior of samples increases as the proportion of Estabragh fibers in the blend increases. Additionally, results showed that samples subjected to more severe needling operation exhibit higher values of NRC. It was also observed that the areal density of samples directly affects their acoustical performance. The higher areal density leads to more sound absorption ability of samples. [ABSTRACT FROM AUTHOR]

An account is given of the use of a strain-gauge system to measure the force exerted on a single needle during the actual punching operation in needle-felting. The variation of this force with distance along the web, test-needle position in the board, web weight, needle penetration, web movement per loom cycle, and fibre orientation in the web is discussed. Finally, an attempt is made to isolate the origin of the punching force and to explain relative values in terms of a known needled-fabric structure. [ABSTRACT FROM AUTHOR]

Treatments designed to increase and decrease friction were applied to rayon staple fibre before processing, as card web, and after needling. Basic frictional properties of the fibres were examined. The first two groups were processed into needled fabrics, and it is shown that considerable damage occurs with high-friction fibres: this results in a deterioration in mechanical properties. Even a wet process without additive causes some loss of strength. However, treatment with a high-friction additive after needling results in increased strength in the fabric. [ABSTRACT FROM AUTHOR]

An account is given of a study of the extent to which fibres were pulled through the web during needling that was made by incorporating one layer of coloured fibres at various positions in a 50-layer web. The number of needle locations at which tracer fibres appeared and the number and length of fibres were determined. Further studies of the occurrence of interlocking loops on the surface of a needled fabric are reported. [ABSTRACT FROM AUTHOR]

An account is given of an investigation in which a small needle board was fitted to the compression cage of an Instron Tensile Tester and used to measure the forces developed during the penetration of a web by needles. The punching speeds were much lower than those in a needling machine. The effects of web weight, type of fibre, fibre length and fineness, density, a reinforcing base fabric, and punching speed were studied. [ABSTRACT FROM AUTHOR]

An account is given of an investigation of the effects of fibre type (rayon, acrylic fibre, wool, and cotton) and dimensions on the properties of needled fabrics, the test methods used being those described in a previous paper. Some fabrics show a stick-slip behaviour in extension; others deform smoothly. Rayon webs — consolidate more easily on needling than Courtelle or wool webs. Longer fibres give higher fabric strengths. Finer fibres also give higher strength, unless fibre damage occurs. The influence of fibre friction is discussed. [ABSTRACT FROM AUTHOR]

The effects of parameters of the needling process—the amount of needling, the needle penetration, the number of passes, the needle arrangement, and the shape of holes—on the structure and properties of needled fabrics are described. In general, increasing the amount of needling and of needle penetration increases the stability of a fabric, but this may be reduced if there is excessive damage during needling. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article on the tensile properties if needle-punched fabric in the previous issues.