Tribological behavior and film-forming mechanism of a polytetrafluoroethylene/polyester fabric composite

Purpose The purpose of this study is to determine the tribological behavior and wear mechanism of a polytetrafluoroethylene (PTFE)/polyester (PET) fabric composite for application as a self-lubricating liner suitable for high-speed and low-load friction conditions. Design/methodology/approach The effects of different loads and sliding speeds on the friction coefficients and wear characteristics of the composite were studied using reciprocating friction tests. Scanning electron microscopy, extended depth-of-field microscopy, and energy-dispersive X-ray spectrometry was used to analyze the worn surface morphology, wear depth and elemental content of the lubrication films, respectively. Findings The friction coefficient curves of the composites presented a long-term steady wear stage under different sliding conditions. With increasing sliding speed, the friction coefficient and wear depth of the composite slowly increased. The film-forming mechanism of the composite revealed that the PTFE/PET ply yarn on the composite surface formed complete PTFE lubrication films at the initial sliding stage. Originality/value The PTFE/PET fabric composite maintained good friction stability and high-speed adaptability, which demonstrates that the composite has broad application prospects as a highly reliable self-lubricating bearing liner with a long lifespan.

Moisture Vapor Resistance of Coated and Laminated Breathable Fabrics Using Evaporative Wet Heat Transfer Method

This study examined the effects of the fiber materials, fabric structural parameters, and surface modification method on the moisture vapor resistance of coated and laminated fabrics according to the measuring method in comparison with evaporative wet heat transfer method. The moisture vapor resistance (Ref) of the coated and laminated fabrics measured using evaporative wet heat transfer method was much more precise than water vapor transmission rate (WVTR) and water vapor permeability (WVP) measured using American Society for Testing and Materials (ASTM) and Japanese Industrial Standard (JIS) methods. The correlation coefficient between Ref and WVTR in the laminated and coated polyethylene terephthalate (PET) fabric specimens was the highest, i.e., −0.833, and −0.715, in coated fabric specimens. Hence, selecting an appropriate measuring method according to the fabric materials and surface modification method is very critical. According to curvilinear regression analysis, the influential factor affecting breathability of the PET fabric specimens measured using evaporative wet heat transfer method was fabric weight (R2 = 0.847) and fabric thickness (R2 = 0.872) in the laminated fabric specimens. Meanwhile, as per multiple linear regression, the most influential fabric structural parameters affecting the breathability of laminated fabric specimens measured using evaporative wet heat transfer method were the fabric density, weight/thickness, and weight followed by the fabric thickness (R2 = 0.943). These results would be valid for laminated breathable fabrics with characteristics within the range of this study and are of practical use for engineering laminated fabrics with high breathability.

Durable flame retardant hybrid sol–gel coating on poly(ethylene terephthalate) fabric and its flame retardant mechanism

In this paper, an organic/inorganic phosphorus and silicon-containing coating was prepared by the sol–gel method and its flame retardant mechanism for poly(ethylene terephthalate) (PET) fabrics was thoroughly investigated. The influence of hybrid coating on PET fabric was investigated by the limited oxygen index (LOI), vertical flammability test (VFT) and microscale combustion calorimetry (MCC). The results revealed that the LOI of the coated PET fabric was up to 29.2% and no dripping was observed in the VFT. MCC results showed that hybrid coating reduced the peak heat release rate, heat release capacity and total heat release of PET fabric. Thermogravimetric analysis demonstrated increased thermal stability and char residue of PET fabrics due to the hybrid coating. Furthermore, the char residues were studied by X-ray photoelectron spectroscopy and scanning electron microscopy. The above results proved that the synergistic effect between the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide group and the silicon network played a key role in the flame retardancy of PET fabrics. In addition, the durability of coated PET fabrics was interpreted by calculating the interaction energy through molecular dynamics simulation.

Electric heating behavior of flexible knitted fabrics comprising reduced graphene oxide, with emphasis on resistance temperature-sensitive behavior and decoupling of contact resistance

Electric fabric heaters have demonstrated potential applications in a wide range of fields for medical electrothermal, human healthcare and athletic rehabilitation. Whereas, little attention has been paid to the resistance variations and the interface of electric heaters. Here, this paper focuses on the resistance temperature-sensitive behavior and interfacial electricity of reduced graphene oxide (RGO)/polyester (PET) fabrics, which are obatained through a facile and scalable dip-coating method. When a current of 0.055 ampere (A) is applied, the RGO/PET fabric can achieve an equilibrium temperature about 89 °C in 20 s, with a maximum heating rate of 11.78 °C/s. Besides, the relative resistance changes of RGO/PET fabric are linearly related to the temperature. When the RGO/PET fabric reaches its steady-state temperature of 89 °C, the value of ΔR/R0 drops by ∼30%, showing that the fabric is endowed with temperature sensitivity. These prominent results indicate that the RGO/PET fabric owns great promise in the field of wearable electric heaters. Notably, the contact resistance at the interface of RGO/PET fabric heater is investigated and the mechanism of the temperature in middle part of heater is higher than that of both ends is analyzed. This provides a qualitative decoupling analysis method for the study and analysis of interfacial electricity and electrothermal distribution of carbon materials.

A Washable Silver-Printed Textile Electrode for ECG Monitoring

Electrocardiography (ECG) is one of the most widely used diagnostic methods to examine heart situations. This paper focuses on the development of a textile-based electrode and the study its ECG-detecting performance. We developed silver-printed textile electrodes via a the flat-screen printing of silver ink on knitted polyester fabric. The silver-printed PET fabric stayed reasonably conductive after washing and stretching, which makes it suitable for wearable applications. Moreover, the ECG measurements in static condition showed that the signal quality collected before and after washing was comparable with standard Ag/AgCl electrodes.