Melt Spinning of Flexible and Conductive Immiscible Thermoplastic/Elastomer Monofilament for Water Detection

In many textile fields, such as industrial structures or clothes, one way to detect a specific liquid leak is the electrical conductivity variation of a yarn. This yarn can be developed using melt spun of Conductive Polymer Composites (CPCs), which blend insulating polymer and electrically conductive fillers. This study examines the influence of the proportions of an immiscible thermoplastic/elastomer blend for its implementation and its water detection. The thermoplastic polymer used for the detection property is the polyamide 6.6 (PA6.6) filled with enough carbon nanotubes (CNT) to exceed the percolation threshold. However, the addition of fillers decreases the polymer fluidity, resulting in the difficulty to implement the CPC. Using an immiscible polymers blend with an elastomer, which is a propylene-based elastomer (PBE) permits to increase this fluidity and to create a flexible conductive monofilament. After characterizations (morphology, rheological and mechanical) of this blend (PA6.6CNT/PBE) in different proportions, two principles of water detection are established and carried out with the monofilaments: the principle of absorption and the short circuit. It is found that the morphology of the immiscible polymer blend had a significant role in the water detection.

FLOATING TANK FOR TRANSPORTING OIL AND HYDROCARBONS FOLLOWING A MARITIME DISASTER

Storage of recovered oil and oily water is an important issue when it comes to maritime disasters, being a significant factor of the overall operation. Using large storage vessels is not always an option especially when the vessel is close to the shore. Currently, floating or non-inflatable tanks made of composite textile materials are used worldwide for the storage of the water/hydrocarbon mixture, regardless of the area of action (maritime or fluvial). The research carried out so far by INCDTP specialists, which consists in modelling, simulation and numerical analysis of various constructive forms and devices, led to the conclusion that for the making of a floating tank for storing water/hydrocarbon/oil mixtures, the best solution for its construction is represented by textile materials woven from high-tech yarns (p-aramid and polyamide 6.6) covered with polyurethane. The experimental model of the floating tank for the transport of oils and hydrocarbons in case of disaster was designed by INCDTP specialists and consists of five experimental models of floating materials (made of five variants of covered textile structures) and assembled in collaboration with specialists from SC CONDOR SA, in the form of a floating storage tank. The storage tank that has been created will be tested on the ground first, in order to perform all gravimetric and quality measurements

DEVELOPMENT AND CHARACTERIZATION OF STITCH-BASED SENSORS

Strain sensing seams have been developed by integrating conductive sewing threads in different types of seam designs on a fabric typical for sports clothing using sewing technology. The aim was to obtain a simply integrated stitch-based sensor that can be applied on sports clothing to monitor the movements of the upper body parts of the user during exercising. Stitch types 304; 406; 602 and 605 were produced. The seams were made on a knitted fabric composed of 80% polyamide 6.6 and 20% elastane. The seams underwent stretch cycling for 10 cycles and up to 44 cycles following EN ISO 14704-1:2005 (modified), using an INSTRON tensile tester machine. The changes in the resistance of the seams with time were recorded simultaneously using Agilent meter U1273A. Sensing functionality among which is sensor gauge factor (GF), stability, drift, and reproducibility were evaluated on the promising sensor seams. The type of base fabric used, stitch type, stitch formation process (friction and dynamic forces during sewing), integrated EC thread length, and positioning of thread(s) in the fabric have a significant influence on the performance of the seams. Sensor seam 406-001comprising 2 EC yarns (Madeira HC12) and Sensor seam 304-010 comprising 1 EC yarn (Madeira HC40) turned out to be very promising and others shall be improved (sensor 602-006 with Madeira HC 40 and sensor 605-002 with a Muriel yarn).

Determination of Fatigue Damage Initiation in Short Fiber-Reinforced Thermoplastic through Acoustic Emission Analysis

This study investigates the damage initiation in short glass fiber-reinforced polyamide 6.6 under fatigue loading using acoustic emission analysis. An optimized specimen geometry was developed to meet the specific requirements of this testing method, at the same time allowing further micromechanical studies. Specimens were preloaded with tensile–tensile fatigue loading, varying the maximum stress and the number of load cycles. Subsequently, the acoustic emission signals in residual strength tests were compared to those of undamaged specimens. The idea behind this approach is that only the damage that has not already occurred under fatigue load can be recorded in the residual strength tests. Using the analysis of acoustic energy, a stress threshold for damage initiation was identified. Furthermore, with tension–tension fatigue tests, the SN curve of the material was determined to estimate the lifetime for the identified stress threshold. The presented approach allows us to estimate a so-called endurance limit of short glass fiber-reinforced polyamide 6.6.

A new approach to the assessment of changes in air permeability, waterproofness, surface, and thermal properties of polyamide 6.6 fabric with polyurethane coating after washing

The research aim was to analyse the changes in the air permeability, waterproofness, surface, mechanical and thermal properties of the polyamide 6.6 fabric with a polyurethane coating before and after 1, 5, and 10 washes in the same conditions using specialized (V1) and universal (V2) laundry detergent. A new approach based on SEM and DSC techniques and assessment of surface free energy combined with standard methods was proposed to explain the nature of observed changes in waterproof and breathable material after washing treatment. SEM analysis indicated that after 10 washes the porosity of the polyurethane coating increased from 8.94% to 14.56% and 18.75% for V1 and V2, respectively. The air permeability increased from 0.747 mm/s for the reference sample to 0.766 mm/s and 0.774 mm/s after 10 washes for V1 and V2, respectively. The waterproofness of the reference sample of 992 mbar decreased with the increasing number of washes to 246 mbar and 122 mbar for V1 and V2, respectively. After 10 washes the surface free energy (γS) decreased by 18.8% and 24.3% for V1 and V2, respectively. The average tensile strength amounted to 833 N and decreased by 13.5% for V1 and by 20% for V2 after 10 washes. The glass transition temperature of the reference fabric was 47.6°C. After 10 washes it increased by 7.2°C and 8.8°C for V1 and V2, respectively. The temperatures of thermal degradation increased by 24.6°C and 22.2°C and the heat of thermal decomposition decreased by 23.6% and 15.8% after 10 washes for V1 and V2, respectively.

Biodegradable Polyamide 6.6 for Textile Application

The study evaluates comparatively some physical and chemical properties of polyamide 6.6 standard and biodegradable. It also evaluates the period of biodegradation of the biodegradable yarn sample and standard sample. The physical properties analyzed were tensile strength, elongation, and tenacity. The chemical properties were related to the behavior of the samples in dyeing and the evaluation of subsequent strength dyeing. The evaluated samples were taken from knitwear produced with polyamide textured filament yarn 80 dtex f 68x1, standard and biodegradable, being purged, bleached, and dyed. The results of the physical tests, although statistically different, have values ​​very near the average, which in practice represent acceptable values ​​within the statistical control process. Both standard and biodegradable samples had the same chemical behavior and there is no difference. Concerning to biodegradation time under laboratory conditions, the carbon dioxide produced by the samples was monitored and measured to determine the percentage of biodegradation according to ASTM D 5511. After 735 days the percentage of biodegradation of the biodegradable yarn was 81.7% and of the normal yarn was 5.2%. This is an expressive gain in ecological terms for synthetic fiber.