Department of Textile Technology

Transcription

1 STUDIES ON THE INFLUENCE OF SOME RAW MATERIAL AND OTHER PARAMETERS ON THE STRUCTURE AND PROPERTIES OF AIR-JET TEXTURED YARNS by R. S. RENGASAMY Department of Textile Technology submitted in fulfilment of the requirements of the Degree of DOCTOR OF PHILOSOPHY to the INDIAN INSTITUTE OF TECHNOLOGY, DELHI March, 1990

2 CERTIFICATE This is to certify that the thesis entitled 'Studies on the Influence of Some Raw Material and Other Parameters on the Structure and Properties of Air-jet Textured Yarns' submitted by Mr. R.S. Rengasamy to the Indian Institute of Technology, Delhi, for the award of Degree of Doctor of Philosophy is a record of the bonafide research work carried out by Mr. R.S. Rengasamy. He has worked under our guidance for the submission of this thesis, which to our knowledge has reached the requisite standard. This thesis or any part thereof, has not been submitted to any other University or Institution for the award of any degree or diploma. (A.K. Sengupta) (V.K. Kothari) Professor Asstt. Professor Thesis Supervisors Department of Textile Technology Indian Institute of Technology, Delhi New Delhi

3 ACKNOWLEDGEMENTS I wish to put on record my deep sense of gratitude to Prof. A.K. Sengupta and Dr. V.K. Kothari of Department of Textile Technology, Indian Institute of Technology, Delh:, for their invaluable guidance and constant involvement throughout the course of this work. It is due to their tireless supervision that this work has developed into its present form- I thank Prof. V.B.. Gupta, Dr. P.K. Banerje,.2. and Dr. Kushal Sen for their kind help in times of need. My thanks are also to my friends and research colleagues especially, Mr. J. Srinivasan, Mr. R. Alagirusamy Mr. R.B. Joshi, Mr. R. Anandakumar, Mr. C. Brahatheeswaran, Mr. K. Mohan, Mr. K.R. Srinivasan and Dr. T. Murugesan who at times relieved my stress by their help and moral support. I am very greateful to Spinning Laboratory Technicians Mr. R.S. Ojha, Mr. J.K. Dang for their co-operation. I thank Mr. Rajesh K. Arora for typing this thesis so quickly and Mr. K.G. Padam and Mr. R.P. Kapoor for their neat tracing of figures both for the thesis and for publications. (R.S. Rengasamy)

4 Dedicated to My Parents

5 ABSTRACT In the air-jet texturing process, the action of fluid forces causes the filaments of continuous filament yarns to separate, forces them to form loops of various configurations and to entangle. The form and frequency of loops are expected to influence the appearance and properties of fabrics made with the air-jet textured yarns. Many methods of analysis of the structure and measurement of the more important properties of these yarns such as instability and bulk have been reported, without agreement regarding the suitability of these methods. This has led to differences in the interpretation of the texturing behaviour. A method of analysing the structure of air--jet textured yarns is described. This method is used t ) quantify the structural parameters such as configuration of loops, loop frequency, average loop height and length, and core diameter. The various methods of assessing the instability of air-jet textured yarns are evaluated as regards their suitability. It is found that the instability values measured by all the methods have a good correlation with texturability. However, the measure of instability based on the extension values of the yarns is dependent on parent yarn extension properties and hence cannot be used for comparing the stability of textured yarns made usinc; parent yarns of different filament extensibilities The instability test method, based on percentage decay in the

6 work done after a fixed number of repeated loading cycles, which is not influenced by the extension properties of parent yarns and also simulates the deformation pattern of the yarns during processing and while in fabric form, is, therefore, recommended. To evaluate the bulkiness of airjet textured yarns, the methods reported in the literature to assess the bulk, and also the relationship between the physical bulk measured Oy the package density method and structural parameters such as core diameter and loop frequency are studied. The static and dynamic wicking behaviour of air-jet textured yarns are examined in terms of the structure and filament properties. Water plays 3n important role in air-j-t texturing. Wetting of the supply yarns before entering the texturing jet, is known to improve texturability. Changes in the fluid properties inside the jet and a reduction in the friction of filaments during texturing are the explanations put forward by various research workers. To study the influence of water, polyester yarns of different friction levels and nylon yarns conditioned in environments of different relative humidities have been textured in both dry and wet conditions. A test rig was fabricated to measure the interfilament friction. The tensions generated at the nozzle exit and in stabilizing the structure, the instability, bulk, mass uniformity and tensile properties of air-jet textured yarns have also been studied in relation to the frictional levels ii

7 of the filaments. Friction influences the structure and properties of air-jet textured yarns. A deterioration in air-jet textured yarn quality has been observed at higher levels of interfilament friction. It has been found that the role of interfilament friction is same within dry and wet textured yarns. Discrepancies between the structures of dry and wet textured yarns and yarn properties are observed when they are analysed in terms of Friction levels of feeder yarns during texturing. The results suggest that the role of water is not related to frictional aspects alone. The analysis of the influence of filament parameters on the structure and properties of air-jet textured yarn is important in understanding the interaction between the filaments and fluid forces during the process. Filament parameters such as filament fineness, cross-sectional shape and the number of filaments in the yarn have been studied in relation to their influence on structure and properties. A high level of dependence has been observed. Texturability of yarns with 'aeavier filaments is poor in terms of loop frequency, loop height and length, loop shape and yarn bulk. Yarns with trilobal filaments perform better in air-jet texturing compared to yarns with circular filaments of similar fineness. There is an optimum number of ends for good stability of textured yarns using a particular jet. Mass uniformity, tensile strength realisation and bulk levels of air-jet textured yarns tend to improve with an increasing number of ends. iii

8 The air-jet texturing process provides an effective means of blending yarns with filaments of different chemical natures and properties. As the appearance of fabrics is influenced by the blend uniformity of the constituent threads, an understanding of the role of the various parameters of air-jet texturing in influencing blend uniformity is important, so that the required degree of blend intimacy in the air-jet textured yarns may be engineered. Blend inhomogeneity is quantitatively assessed in relation to raw material and nozzle parameters etc. Blend uniformity is poor in the case of blends of components of dissimilar properties. Blend homogeneity improves with the degree of texturing as assessed by the delivery zone tension. In the case of components of similar properties, finer filaments are found to produce better blend homogeneity. iv

9 Page No. CONTENTS CHAPTER 1 : INTRODUCTION AND GENERAL REVIEW Introduction Classification of Textured Yarns and Texturing Methods Classification of textured yarns Classification of texturing methods Air-jet Texturing Air-jet texturing process 6 1.3,2 Mechanism of bulking in air-jet texturing Developments in air-jet texturing Industrial nozzles developments Wetting devices Developments in air-jet texturing machines Types of air-jet textured yarns Properties of air-jet textured yarns Variables in air-jet texturing process Range of feeder yarns and end-products Production speeds and future projections Air-jet Texturing as an Alternative to False- Twist Texturing and Spun Yarn Methods Air-jet texturing vs. false-twist texturing Air-jet texturing vs. spun yarn methods Objectives of the Present Study 38

10 CHAPTER 2 : REVIEW OF LITERATURE PERTAINING TO THE PRESENT WORK 2.1 Structure and Properties of Air-jet Textured Yarns Structure of air-jet textured yarns Methods of analysing structure of air-jet textured yarns Measurement of instability of air-jet textured yarns Bulkiness of air-jet textured yarns Frictional Behaviour of Textile Fibres General mechanism of friction Friction of high polymers Friction and lubrication of synthetic fibres Parameters influencing frictional behaviour Chemical structure of lubricants Input tension Surface roughness Speed and viscosity Area of contact Temperature of guide or fibre Lubricant concentration Fibre lustre Fibre material and wetting of fibres Role of Water in Air-jet Texturing Role of water in changing the fluid properties 65 ii

11 2.3.2 Role of water as a lubricant for hydrophobic fibres Effect of wetting on textured yarn properties Spin finishes, frictional behaviour and wetting Relative humidity and air-jet texturing of hydrophilic fibres Raw Material and Jet Parameters in Air-jet Texturing Interaction of fluid and filaments in air-jet texturing Effect of filament properties on properties of air-jet textured yarns Effect of jet parameters Converging-diverging nozzles Cylindrical nozzles Effect of impact elements Blend Intimacy in Air-jet Textured Yarns Quantitative Analysis of Blend Inhomogeneity 81 CHAPTER 3 : EVALUATION OF STRUCTURE AND PROPERTIES OF AIR-JET TEXTURED YARNS 3.0 Introduction Experimental Structural geometry of air-jet textured yarns Evaluation of methods for measuring instability Materials Tension measurements at the nozzle exit and at the stabilizing zone 86

12 Methods of measuring instability Evaluation of Bulkiness of air-jet textured yarns Package density method Fabric thickness method Water uptake method Structural analysis as a possible measure of bulk Measurement of Wicking Properties Results and Discussion Structure of air-jet textured yarns Evaluation of structural stability of air-jet textured yarns Evaluation of bulkiness of air-jet textured Yarns Wicking properties of air-jet textured yarns Equilibrium wicking behaviour Dynamic wicking behaviour Summary 143 CHAPTER 4 : ROLE OF WATER IN AIR-JET TEXTURING 4.0 Introduction Role of Water ink Air-jet Texturing of Polyester Filam nt Yarns Experimental Materials Spin finish application Measurement of interfilament friction Test methods 154 i v

13 4.1.2 Results and Discussion Role of Conditioning Environment and Water in Air-jet Texturing of Nylon Yarns Experimental Conditioning of feeder yarns Test methods Results and Discussion Summary 207 CHAPTER 5 : EFFECT OF RAW MATERIAL CHARACTERISTICS ON STRUCTURE AND PROPERTIES OF AIR-JET TEXTURED YARNS 5.0 Introduction ' Experimental Results and Discussion Effect of filament fineness (dpf) Effect of filament cross-sectional shape Effect of number of filaments Summary 255 CHAPTER 6 : BLEND INHOMOGENEITY IN AIR-JET TEXTURED YARNS 6.0 Introduction Experimental Materials Process parameters Nozzles Free filament yarn speed measurement Preparation and examination of yarn cross-sections 263

14 6.1.6 Computational method Tension measurements Results and Discussion Summary 287 CHAPTER 7 : CONCLUSIONS AND RECOMMENDATIONS FOR FUTURE WORK 7.1 Conclusicns Recommendations for Future Work 293 REFERENCES 295 LIST OF PUBLICATIONS vi