This paper describes basic principles and techniques involved in designing waterproof breathability fabrics. Breathable fabrics are available in a large variety, which can be categorized as — closely woven fabrics, microporous membranes and coating, hydrophilic membranes and coating, combination of microporous and hydrophilic membranes and coating, use of retroreflective microbeads, smart breathable fabrics and fabric based on biomimetics. Basic principles and mechanisms of water vapor transmission solely depend on the type of breathable fabrics. The formulation and application of microporous and hydrophilic membranes and coatings have been well researched in different fields of application. Smart breathable fabric and fabric based on biomimetics, which are of recent origin, are also showing their potential. The technology is continuously evolving in the areas of a cost-effective manufacturing process, improving material formulation to enhance the film's properties, and controlling pore sizes and their distributions, developing improved monolithic film and coating materials for a variety of applications. Method of incorporation of membrane, coating techniques, fabric substrate, lining material and above all the garment construction are also undergoing changes and play vital role in designing breathable garments.

This article describes engineering design of waterproof breathability fabrics specifically designed for leisure, medial uses and survival clothing. In many applications, breathable fabrics not only satisfy water-vapor permeability but also a number of other functional characteristics. Garment design, cut and fit, design of seam, constituent of multilayer structure and various forms of ventilation system are often modified depending on the functional requirement. In the comparative evaluation of several breathable fabrics, it is often very difficult to suggest the product which performs best. The conditions of application and corresponding requirements imposed on the product are quite different depending on the end use.

The process of making spun bond fabrics combines the production of fabrics with the production of filaments. High process efficiencies and excellent properties of these fabrics have made them acceptable in different areas of application like civil engineering, medical and hygiene, automotive industry, shoe industry and packaging. Controlling the structure and properties of the fabric is a difficult task as there are several process parameters affecting fabric properties besides the structure and properties of the filaments. Several scattered studies explain the influence of process parameters on filament and fabric properties but lot of information on the fabric properties is missing. A comprehensive review of the spun bonding technique, fabric characteristics and the process parameters is presented in this paper. An understanding on this will help in optimizing the process parameters for producing desired properties in the fabric.

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Polypropylene spunbond, spunbond/meltblown/spunbond, and spunlace fabrics of 35 and 50 g/m 2 weight are tested for barrier properties against microorganisms and liquid or body fluids to estimate their suitability for surgical gowns. The fabrics are also treated with different levels of antibacterial and fluorochemical finishes in a single bath using pad-dry-cure method. Liquid barrier properties of samples are analyzed by water impact penetration, hydrostatic pressure test, and blood repellency test. Parallel streak method is used to measure the antibacterial activity on the fabric samples with Staphylococcus aureus. The fabric samples are also analyzed for air permeability and stiffness. It is observed that spunbond/meltblown/spunbond fabric of 35 and 50 g/m 2 weight offer sufficient liquid barrier properties for level 2 protection as per the Association for the Advancement of Medical Instrumentation barrier protection classification. Spunlace and spunbond fabrics of 35 and 50 g/m 2 weight offer only level 1 protection. Spunbond/meltblown/spunbond fabrics are poorest in terms of comfort, because of their higher stiffness and lower air permeability values; spunlace fabric offers the highest air permeability and lowest stiffness force. Spunbond/meltblown/spunbond fabric samples with 4% and 7% fluorochemical finish and 1.5% antibacterial finish can provide level 4 protection. Spunbond fabrics require 4% and spunbond/meltblown/ spunbond fabrics require 1% fluorochemical finish to achieve level 2 protection.

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Purpose This paper aims to develop a single regression model (instead of developing models separately for each thread type) to predict the sewing thread consumption for cotton and polyester staple spun threads. Design/methodology/approach A single regression model is developed for predicting sewing thread consumption for cotton and polyester threads. The polyester sewing threads have lower sewing thread consumption as compared to cotton threads because of their higher elongation behaviour. The model differentiates between the cotton and polyester sewing threads using their elongation values at peak levels of tensions experienced by the sewing threads during stitch tightening. By comparing the estimated thread consumption values with actual values, the effectiveness of model is evaluated with root mean square error and coefficient of determination (R2). Findings During the sewing process, by understanding the behaviour of different types of sewing threads, it is possible to develop a single regression model for all types of threads. Practical implications The sewing thread consumption can be easily calculated for cotton and polyester sewing threads using a single regression equation using the sewing assembly thickness, stitch density and elongation of thread at peak tension. The garment manufacturers need not depend on different charts for sewing thread consumption for stock management. Originality/value The sewing thread consumption is different for different types of threads, and garment manufacturers have to depend on different charts given by sewing thread manufacturers or use different equations for each type of threads. Using this single regression equation, sewing thread consumption for cotton and polyester sewing thread can be estimated accurately.