Influence of the Degree of Crystallinity on the Mechanical and Tribological Properties of High-Performance Thermoplastics Over a Wide Range of Temperatures: From Room Temperature up to 250°C

High-performance anti-wear polyetheretherketone/polytetrafluoroethylene (PEEK/PTFE) blends have drawn much attention over the past few years, owing to their wide range of potential applications. However, a convenient and effective method to prepare such blends with superior mechanical and tribological properties is still lacking. In this work, we propose a promising approach that uses melt-processable PTFE (MP PTFE), instead of conventional PTFE, to prepare anti-wear blends. MP PTFE, with melt flow abilities under appropriate conditions, can disperse homogeneously in PEEK, enhancing both the mechanical and tribological properties of the PEEK/PTFE blend. To prove this postulation, in this work, both MP PTFE and commercial PTFE were blended with PEEK, separately, and the effects of PTFE type and content on the tensile and tribological properties of the blends were studied. The results showed that, although the addition of commercial PTFE to PEEK could increase the wear resistance, it decreased the tensile strength of PEEK significantly. Compared to the blends with commercial PTFE, the blends with MP PTFE exhibited better tribological performance and higher tensile strength for PTFE content below 10 wt%. It was confirmed that the better dispersion of MP PTFE in PEEK endowed the blends with higher tensile strength. The surface analysis indicated that the MP PTFE could readily migrate to and enrich the surfaces of the blends. The relatively high PTFE content on the surface favored the formation of tribo-films, enhancing the tribological properties of the blends.

Download Full-text

An insight on the process–property relationships of melt spun polylactic acid fibers

Textile Research Journal ◽

10.1177/0040517519845684 ◽

2019 ◽

Vol 89 (23-24) ◽

pp. 4959-4966 ◽

Cited By ~ 1

Author(s):

AM Ali ◽

HM El-Dessouky

Keyword(s):

Polylactic Acid ◽

High Performance ◽

Polarized Light ◽

Degree Of Crystallinity ◽

X Ray Diffraction ◽

Scanning Calorimetry ◽

Laser Diffractometry ◽

Wide Range ◽

Innovative Materials ◽

The Degree Of Crystallinity

Polylactic acid (PLA) fibers are receiving growing interest as one of the recent innovative materials being developed for various applications. The inherent biodegradability of PLA makes it highly attractive for the biomedical and health care sectors. PLA fibers need to be partially and/or highly oriented to allow high performance and readiness for a wide range of manufacturability. In this study, the structure and properties of PLA fibers, manufactured at different spinning speeds, were studied. Laser diffractometry, polarized light microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to determine the diameter, birefringence, molecular orientation, enthalpy and degree of crystallinity of as-spun and drawn PLA fibers. The results of DSC and XRD showed that the degree of crystallinity of the PLA fibers is significantly improved for the drawn PLA fibers compared to the as-spun fibers and leveled off in the case of changing the take-up speeds of drawn fibers.

Download Full-text

Plasmonic semiconductor nanogroove array enhanced broad spectral band millimetre and terahertz wave detection

Light Science & Applications ◽

10.1038/s41377-021-00505-w ◽

2021 ◽

Vol 10 (1) ◽

Author(s):

Jinchao Tong ◽

Fei Suo ◽

Tianning Zhang ◽

Zhiming Huang ◽

Junhao Chu ◽

...

Keyword(s):

Surface Plasmon ◽

High Performance ◽

Room Temperature ◽

Spectral Band ◽

High Capacity ◽

Terahertz Wave ◽

Semiconductor Surface ◽

Wide Range ◽

Low Sensitivity ◽

Air Interfaces

AbstractHigh-performance uncooled millimetre and terahertz wave detectors are required as a building block for a wide range of applications. The state-of-the-art technologies, however, are plagued by low sensitivity, narrow spectral bandwidth, and complicated architecture. Here, we report semiconductor surface plasmon enhanced high-performance broadband millimetre and terahertz wave detectors which are based on nanogroove InSb array epitaxially grown on GaAs substrate for room temperature operation. By making a nanogroove array in the grown InSb layer, strong millimetre and terahertz wave surface plasmon polaritons can be generated at the InSb–air interfaces, which results in significant improvement in detecting performance. A noise equivalent power (NEP) of 2.2 × 10−14 W Hz−1/2 or a detectivity (D*) of 2.7 × 1012 cm Hz1/2 W−1 at 1.75 mm (0.171 THz) is achieved at room temperature. By lowering the temperature to the thermoelectric cooling available 200 K, the corresponding NEP and D* of the nanogroove device can be improved to 3.8 × 10−15 W Hz−1/2 and 1.6 × 1013 cm Hz1/2 W−1, respectively. In addition, such a single device can perform broad spectral band detection from 0.9 mm (0.330 THz) to 9.4 mm (0.032 THz). Fast responses of 3.5 µs and 780 ns are achieved at room temperature and 200 K, respectively. Such high-performance millimetre and terahertz wave photodetectors are useful for wide applications such as high capacity communications, walk-through security, biological diagnosis, spectroscopy, and remote sensing. In addition, the integration of plasmonic semiconductor nanostructures paves a way for realizing high performance and multifunctional long-wavelength optoelectrical devices.

Download Full-text

The Influence of Reinforcing Fibers on the Morphology and Crystallization of Thermoplastic Polymer Composites

MRS Proceedings ◽

10.1557/proc-255-129 ◽

1991 ◽

Vol 255 ◽

Author(s):

Ludwig Rebenfeld ◽

Glenn P. Desio ◽

Veronika E. Reinsch

Keyword(s):

High Performance ◽

Crystallization Process ◽

Polarized Light ◽

Fiber Surface ◽

Weight Fraction ◽

Degree Of Crystallinity ◽

Surface Finishes ◽

Reinforcing Fibers ◽

Glass Carbon ◽

The Degree Of Crystallinity

AbstractSemi-crystalline thermoplastic polymers are being used increasingly as matrices in high performance fiber reinforced composites. The crystallization kinetics and morphology of these polymers have been studied extensively, but relatively little attention has been given to the effects of the reinforcing fibers on the crystallization process.We have studied the effects of glass, carbon and aramid fibers on the rates of crystallization, the degree of crystallinity, and the glass transition temperature of such typical thermoplastics as poly(phenylene sulfide) and poly(ethylene terephthalate). Based on the isothermal crystallization studies using DSC, we find that, in general, reinforcing fibers increase the rates of crystallization and decrease the degree of crystallinity, the extent of these effects being dependent on the weight fraction of fiber in the composite, the specific type of fiber, and the nature of surface finishes (sizes) that may have been applied.The spherulitic morphology that develops in these polymers during the crystallization process, as characterized by polarized light microscopy, is also affected by the reinforcing fibers. In many cases, transcrystalline regions develop near the fiber surface due to nucleation effects.

Download Full-text

Microstructures, mechanical and tribological properties of VN films deposited by PLD technique

RSC Advances ◽

10.1039/c6ra02403c ◽

2016 ◽

Vol 6 (40) ◽

pp. 33403-33408 ◽

Cited By ~ 8

Author(s):

Hongjian Guo ◽

Bo Li ◽

Jianyi Wang ◽

Wenyuan Chen ◽

Zhenyu Zhang ◽

...

Keyword(s):

Tribological Properties ◽

Room Temperature ◽

Laser Deposition ◽

Vanadium Nitride ◽

Deposition Technique ◽

Mechanical And Tribological Properties

Consistent stoichiometric FCC structured vanadium nitride films were fabricated by plused laser deposition technique at room temperature and 300 °C, and their microstructures, mechanical and tribological properties were investigated.

Download Full-text

Mechanical and tribological properties of nano-sized Al2O3 particles on ADC12 alloy composites with Strontium modifier produced by stir casting method

ADI Journal on Recent Innovation (AJRI) ◽

10.34306/ajri.v3i1.346 ◽

2021 ◽

Vol 3 (1) ◽

pp. 9-20

Author(s):

Muhammad Wira Akira ◽

Hanuna Haritsah ◽

Anne Zulfia ◽

Ekavianti Prajatelistia

Keyword(s):

Tribological Properties ◽

High Performance ◽

Spinel Phase ◽

Stir Casting ◽

Grain Refiner ◽

Interface Area ◽

Alloy Matrix ◽

Mechanical And Tribological Properties ◽

Al2o3 Particles ◽

Microstructure Modifier

Nano-Al2O3 particles were incorporated into ADC12 alloy with the addition of Al-5Ti-B, Al-Sr, and Mg to achieve high performance in mechanical and tribological properties. In this study, varied nano-Al2O3 was used from 0.25 vf-% to 0.5 vf-% through stir casting methods to discover the optimum amount to obtain high performance. Besides, the inclusion of grain refiner Al-5Ti-B and microstructure modifier Al-Sr is expected to improve performance to the next level. However, porosity and agglomeration still be a concern in Aluminum alloy matrix composite fabrication. The presence of spinel phase MgAl2O4 in the interface area between nano-Al2O3 particles and ADC12 alloy is relied upon to minimize this porosity and agglomeration issue. The optimum of tensile strength and hardness was found at 0.35 vf-% Al2O3 and wear rate at 0.4 vf%. Although, the optimum point of wear found at 0.4 vf%, porosity began to increase at 0.4 vf% as well. As a result, 0.35 vf% addition of the nano-Al2O3 gives the best performance for the composite.

Download Full-text

Enhanced terahertz detection of multigate graphene nanostructures

Nanophotonics ◽

10.1515/nanoph-2021-0573 ◽

2022 ◽

Vol 0 (0) ◽

Author(s):

Juan A. Delgado-Notario ◽

Wojciech Knap ◽

Vito Clericò ◽

Juan Salvador-Sánchez ◽

Jaime Calvo-Gallego ◽

...

Keyword(s):

High Performance ◽

Room Temperature ◽

Thz Radiation ◽

Electron Hole ◽

Back Gate ◽

Potential Barriers ◽

Terahertz Detection ◽

Wide Range ◽

Order Of Magnitude ◽

Effect Transistor

Abstract Terahertz (THz) waves have revealed a great potential for use in various fields and for a wide range of challenging applications. High-performance detectors are, however, vital for exploitation of THz technology. Graphene plasmonic THz detectors have proven to be promising optoelectronic devices, but improving their performance is still necessary. In this work, an asymmetric-dual-grating-gate graphene-terahertz-field-effect-transistor with a graphite back-gate was fabricated and characterized under illumination of 0.3 THz radiation in the temperature range from 4.5 K up to the room temperature. The device was fabricated as a sub-THz detector using a heterostructure of h-BN/Graphene/h-BN/Graphite to make a transistor with a double asymmetric-grating-top-gate and a continuous graphite back-gate. By biasing the metallic top-gates and the graphite back-gate, abrupt n+n (or p+p) or np (or pn) junctions with different potential barriers are formed along the graphene layer leading to enhancement of the THz rectified signal by about an order of magnitude. The plasmonic rectification for graphene containing np junctions is interpreted as due to the plasmonic electron-hole ratchet mechanism, whereas, for graphene with n+n junctions, rectification is attributed to the differential plasmonic drag effect. This work shows a new way of responsivity enhancement and paves the way towards new record performances of graphene THz nano-photodetectors.

Download Full-text

Development of Antifriction Materials Based on Polytetrafluoroethylene with Carbon Fibers and Tungsten Disulfide

Materials Science Forum ◽

10.4028/www.scientific.net/msf.992.745 ◽

2020 ◽

Vol 992 ◽

pp. 745-750

Author(s):

A.P. Vasilev ◽

T.S. Struchkova ◽

A.G. Alekseev

Keyword(s):

Wear Resistance ◽

Polymer Composites ◽

Carbon Fibers ◽

Coefficient Of Friction ◽

Tribological Properties ◽

Relative Elongation ◽

Tungsten Disulfide ◽

Degree Of Crystallinity ◽

Mechanical And Tribological Properties ◽

The Coefficient Of Friction

This paper presents the results from the investigation of effect the carbon fibers with tungsten disulfide on the mechanical and tribological properties of PTFE. Is carried out a comparison of mechanical and tribological properties of polymer composites PTFE-based with carbon fibers and PTFE with complex filler (carbon fibers with tungsten disulfide). It is shown that at a content of 8 wt.% CF+1 wt.% WS2 in PTFE, wear resistance increases significantly while maintaining the tensile strength, relative elongation at break and low coefficient of friction at the level of initial PTFE. The results of X-ray analysis and investigation of SEM supramolecular structure and friction surfaces of PTFE and polymer composites are presented. It is shown that the degree of crystallinity of polymer composites increases in comparison with the initial PTFE. The images of scanning electron microscope reveal that particles of tungsten disulfide concentrating on the friction surface is likely responsible to a reduction in the coefficient of friction and increase the wear resistance of PTFE-based polymer composites with complex fillers.

Download Full-text

The synergistic effect of SiC/R-GO composite on mechanical and tribological properties of thermosetting polyimide

Journal of Composite Materials ◽

10.1177/00219983211049288 ◽

2021 ◽

pp. 002199832110492

Author(s):

Aijiao Li ◽

Suoxiao Wang ◽

Zhe Chen ◽

Hong Liu ◽

Hongding Wang

Keyword(s):

Friction Coefficient ◽

Wear Rate ◽

Tribological Properties ◽

High Performance ◽

In Situ Polymerization ◽

Effective Means ◽

Compression Modulus ◽

Nanocomposite Films ◽

Mechanical And Tribological Properties ◽

Industry Applications

The effective means to solve material wear is to develop self-lubricating composite materials with excellent tribological, thermal, and mechanical properties. Herein, the composites of reduced graphene oxide (r-GO) nanosheet decorated with Silicon Carbide (SiC) were facilely prepared with employing a silane coupling agent, and the corresponding r-GO/SiC/thermosetting polyimide (r-GO/SiC/TPI) nanocomposite films were obtained by in situ polymerization method. The mechanical, tribological, and thermal properties of these nanocomposite films were investigated. When the content of r-GO/SiC was at 1.0 wt%, the compression strength and compression modulus of the composite increased by 37.7% and 47.3%, respectively, which were much higher than that of TPI composites addition of r-GO or SiC alone. Furthermore, r-GO/SiC/TPI composites also exhibited the lowest wear rate and friction coefficient in these reinforced TPI nanocomposites. When the content of r-GO/SiC was 0.8 wt%, particularly, the friction coefficient and wear rate of r-GO/SiC/TPI decreased by 22.8% and 79.8% compared to pure TPI, respectively. Additionally, trace amount r-GO/SiC hybrids also significantly enhance the thermal stability of TPI matrix. Compared to the polyimide composites reinforced by common nano-scale inorganic fillers, the outstanding mechanical and tribological properties of this r-GO/SiC/PI composites could be attributed to the ball on plane structure of GO/SiC, which lead to crack reflection, strength increment. These r-GO/SiC/TPI composites demonstrate the promising potential to be used as high-performance tribological materials in industry applications.

Download Full-text