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Characterization of recycled crumb rubber modified binders containing wax warm additives

Journal of Traffic and Transportation engineering(English Edition) 2018年第3期5卷 197-206页

作者： Hyun Hwan Kim Mithil Mazumder Soon-Jae Lee Moon-Sup Lee Department of Engineering Technology Texas State University San Marcos TX 78666 USA Materials Science Engineering and Commercialization Program Texas State University San Marcos TX 78666 USA Korea Institute of Civil Engineering and Building Technology Goyang-si Gyeonggi-do 10223 Republic of Korea

This paper addresses the laboratory experiment of performance properties of recycled CRM binders containing artificially aged CRM binders with wax additives. The warm CRM binders were produced using two wax additives （LEADCAP and Sasobit） and then shortterm and long-term aged using the rolling thin film oven （RTFO） and pressure aging vessel （PAV） procedures. The recycled CRM binders were aged through the RTFO and PAV pro- cedures. A set of Superpave binder tests were carried out on the binders through the rotational viscometer, the dynamic shear rheometer （DSR）, and the bending beam rheometer （BBR）. In general, the results of this study indicated that （1） the addition of longterm aged （LTA） CRM binder can significantly increase the viscosity of the recycled CRM binders as expected, （2） the wax additives in recycled CRM binders were still effective to improve the viscosity and rutting properties even after experiencing the aging process, （3） the CRM binders containing wax additives showed the higher rutting resistance compared to the control CRM binders, （4） the recycled CRM binder containing wax additives was found to have less resistance to fatigue and low temperature cracking, （5） wax warm additives into the recycled CRM binders seemed to have a significant role for cracking properties, based upon their substantial amount.

关键词： CRM binder Wax additives Rotational viscosity Recycling Rutting

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MECHANICAL AND ELECTRICAL CHARACTERIZATION OF 3D PRINTED POLYAMIDE 6 NANOGRAPHENE COMPOSITE FOR ELECTROSTATIC DISCHARGE APPLICATIONS

MECHANICAL AND ELECTRICAL CHARACTERIZATION OF 3D PRINTED POL...

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SAMPE 2022 Conference and Exhibition

作者： Arigbabowo, Oluwasola K. Omer, Liam Tate, Jitendra Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States

ISBN: (纸本)9781934551417

Polyamide 6 (PA 6) is an engineering thermoplastic that can be used to develop polymer nanocomposite with high potential in electrostatic discharge applications. By the incorporation of nanofillers in PA 6 to enhance multifunctional properties, PA 6 nanocomposites can serve as technological alternatives to commercial thermoplastics for 3D printing via fused deposition modelling (FDM). Hence, this study evaluated the mechanical and electrical properties of 3D printed PA6 nanographene composites for electrostatic discharge applications. 2, 4 and 6 wt.% of Graphene Nanoplatelets (GNP) was compounded with PA6 using co-rotating twin screw extruder to produce 1.75mm diameter monofilaments for FDM 3D printing. The test samples were printed using commercial-off-the-shelf (COTS) 3D printer, Lulzbot TAZ 6 FDM printer. Morphology, mechanical and electrical characterization was carried out according to their respective ASTM standard. An improvement in tensile and flexural properties were observed with an increase in nanographene addition, and a maximum improvement of 61.4 and 55.9% in tensile and flexural modulus respectively was recorded at 6wt% loading level. Electrical conduction of the insulative polyamide 6 matrix was enhanced by an appreciable reduction of its volume resistivity to 1011 Ω.cm by 2wt% nanographene loading, which seems promising for manufacturing static discharge products. Copyright 2022. Used by the Society of the Advancement of Material and Process engineering with permission.

关键词： Graphene

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Method for the simultaneous determination of vertical and horizontal mobilities in superlattices

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Physical Review B 2014年第7期89卷 075305-075305页

作者： C. H. Swartz T. H. Myers Texas State University Materials Science Engineering and Commercialization Program 601 University Drive San Marcos Texas 78666 USA

A magnetoresistance method is proposed which extracts both the growth direction mobility and the planar mobility of an anisotropic thin film, such as a superlattice. A magnetic field which varies in magnitude and orientation is employed. Errors appearing in previous magnetotransport studies on superlattices are resolved. In particular, it is shown that the contact layers used to send currents through an active region do not have a negligible resistance, even if they are much more conductive than the active region. The technique is demonstrated on an InAs/GaSb-based structure where the growth axis to planar mobility anisotropy ratio is found to drop rapidly with increasing temperature.

关键词： SUPERLATTICES MAGNETORESISTANCE MAGNETIC fields ANISOTROPY THIN films

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Mechanical performance of needle-punched carbon fiber reinforced phenolic composites

Mechanical performance of needle-punched carbon fiber reinfo...

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SAMPE 2021 Conference and Exhibition

作者： Trevino, Esmerehildo Belduque, Camila Tate, Jitendra Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States

ISBN: (纸本)9781934551394

Traditional composite laminates that are highly used in the aerospace and automotive industry have reinforcing fibers that lie in the X and Y orientation of the laminate or ply stack. The resulting composite product is one with anisotropic properties, being weaker in the Z orientation of the laminate. Composite failure will occur between the reinforcing layers at the resin rich interlayer. To improve the composite's resistance to delamination, a needle-punching process is utilized to re-orient parent carbon fibers thru the thickness of the dry fiber ply stack. The needlepunching equipment consists of a needle-board carrying rows of barbed needles. The needleboard drives the needles through the preform, and the barbs re-orienting the fibers in the Z direction. Rayon based 8-harness satin carbon fiber is needle-punched and infused with a phenolic resin using Vacuum Assisted Resin Transfer Molding (VARTM). Varying degrees of needle-punch density are evaluated for their respective inter-laminar shear strengths. A correlation model of needle-density to mechanical behavior was developed and fiber reorientation was analyzed by microscopic imaging. © 2021 Soc. for the Advancement of Material and Process engineering. All rights reserved.

关键词： Needles

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Performance evaluation of 2.5d needle-punched CFRP/phenolics composites 7

Performance evaluation of 2.5d needle-punched CFRP/phenolics...

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7th Composites and Advanced materials Expo, CAMX 2020

作者： Trevino, Esmerehildo Tate, Jitendra Belduque, Camila Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States

With the increase of composite components being introduced into the aerospace industry, the adoption of new manufacturing processes that improve the performance of the created parts when compared to traditional methods can be highly advantageous for a company. In the case of 2D composites, where reinforcement fibers are oriented along two axes, the result is a composite with anisotropic properties, which are typically weaker in the out-of-plane direction. Under high stress conditions, composite parts can delaminate resulting in a drastic loss of the load bearing capabilities of the part. One of the solutions to improve the thru-thickness mechanical properties is to add non-woven fiber layers to a dry composite preform stack and process it through a needle-punching operation. Needle-punching consists of rows of evenly spaced, barbed needles which repeatedly penetrate through the preform. The needles re-orient the loose web fibers through the thickness of the composite laminates, providing the z-axis or out-of-plane fiber reinforcement. In this project, Carbon felt and plain-woven carbon fabric preform is needle-punched and infused with a Phenolics resin, suitable for the Vacuum Assisted Resin Transfer Molding (VARTM) technique. The design and manufacturing parameters of the needle-punching process such as the number of non-woven web layers added to the preform, alternate layup configurations, and varying levels of needle-punch density are analyzed. To evaluate the in-plane and out-of-plane mechanical properties of the 2D and 2.5D needle-punched composites, the following mechanical testing will be performed per ASTM standards: tensile test, flexure, interlaminar shear and impact testing. Additionally, scanning electron microscope (SEM) analysis is conducted on the specimens. © 2020. CAMX – The Composites and Advanced materials Expo.

关键词： Scanning electron microscopy

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SUSTAINABLE HIGH-QUALITY BIO-COMPOSITE OF NOVICE NATURAL FIBER-REINFORCED POLYLACTIC ACID (PLA) 8

SUSTAINABLE HIGH-QUALITY BIO-COMPOSITE OF NOVICE NATURAL FIB...

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8th Annual Composites and Advanced materials Expo, CAMX 2021

作者： Panta, Subash Alvizo, Elizabeth Nichol Candelas, Matt Thramann, Harrison Tate, Jitendra S. Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States

ISBN: (纸本)9781934551400

Current biodegradable plastics have inferior properties to non-biodegradable plastics. To overcome these challenges, this research is proposing to fabricate a biocomposite using a biodegradable polymer polylactic acid (PLA) as a matrix and natural fiber obtained from Giant Ragweed (Ambrosia trifeda). The addition of natural fibers into PLA is a challenge because of opposing hydrophilic and hydrophobic interfacial bonding between fiber and matrix. Experiments were conducted to reduce hydrophilic tendencies of the natural fibers by surface treatment with 2% maleic anhydride (MA) in xylene. To find the optimum fiber/matrix ratio, fibers were studied at 10 wt.% and 15 wt.%. The scope of this paper focuses on 10 wt.% due to its consistent fiber diameter compared to 15 wt.%. Single screw extrusion was employed for the filament manufacturing process, and samples were fabricated using fused filament fabrication additive manufacturing. SEM imaging was conducted to check the dispersion of fibers in the PLA matrix before and after surface treatment. Tensile and flexural properties were evaluated using ASTM standards D638 for the tensile test to study ultimate tensile strength and tensile modulus. Similarly, ASTM D790 for flexure test to study flexural strength and flexural modulus. The research has established detailed process parameters and analysis of maleic anhydride treated Ragweed reinforced PLA Biocomposites at 10 wt.% loading level. Copyright 2021. Used by CAMX – The Composites and Advanced materials Expo

关键词： Surface treatment

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Processing and characterization of high temperature phenolic nanocomposites

Processing and characterization of high temperature phenolic...

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SAMPE 2021 Conference and Exhibition

作者： Nahar, Aziza G. Omer, Liam Diaz, Matthew T. Tate, Jitendra S. Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States Materials Science Engineering and Commercialization Program Texas State University 601 University Drive San MarcosTX78666 United States

ISBN: (纸本)9781934551394

As the performance of electronics and aerospace technologies increases, the demand for lightweight composites capable of maintaining the performance at high temperatures follows in tandem. Besides ablative applications these composites are playing a vital role as friction materials, insulative materials, and shell moldings material. Phenolic resin, SC-1008 exhibits hightemperature (Glass transition temperature, 250°C) and mechanical performance with extraordinary char yields in high-temperature environments. Zirconia and Alumina nanoparticles often enhances thermally and electrical insulative properties and increases thermal stability in nano structured composites. In this study, a rayon-based carbon reinforced phenolic composites composed of 2wt% Alumina Nanofibers and 5wt% Zirconia nanoparticles was fabricated using combination of hand layup and compression molding. Nanocomposite performance is highly dependent upon dispersion quality. Nanoparticles were dispersed in the phenolic resin using combination of 3-roll mill and sonication. Scanning electron microscopy (SEM) was performed on resin samples to determine uniform dispersion. Char yield was evaluated using Thermal Gravimetric Analysis (TGA). Tensile and flexural properties were evaluated using appropriate ASTM standards. Oxyacetylene test bench (OTB) was used to determine the ablation rate, heat soak temperature, and mass-loss rate. The ablative performance of newly developed nanocomposites was compared with industry standard, MX-4926. © 2021 Soc. for the Advancement of Material and Process engineering. All rights reserved.

关键词： Nanocomposites

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Characterization and sustainable retting of ragweed fibers

Characterization and sustainable retting of ragweed fibers

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International SAMPE Conference and Exhibition 2020

作者： Alvizo, Elizabeth N. Tate, Jitendra S. Holthaus, Serra E. Irvin, Jennifer A. Ingram School of Engineering Texas State University United States Materials Science Engineering and Commercialization Program Texas State University United States Department of Chemistry and Biochemistry Texas State University United States Texas State University San MarcosTX78666 United States

This work aims to characterize the North American native plant, Ambrosia trifida, commonly known as ragweed. The purpose of this research is to build a cost-effective manufacturing process that will produce quality microfibers to be used as a reinforcement in polymer matrix composite (PMC) applications. Chemical retting methods were employed and evaluated based on cellulose content extracted. Hydrogen peroxide (H2O2) was used to expedite the retting process as previous experiments have shown it to produce cellulose with less impurities. Water retting was conducted in parallel with H2O2. Distilled, tap, and river water were compared based on impurities and time allotted. Sodium hydroxide chemical treatment was used to cleanse the fiber from non-cellulose material. The overall mechanical properties of natural fiber reinforced PMC are highly dependent on morphology, aspect ratio, hydrophilic tendency and dimensional stability of the fibers. Scanning Electron Microscopy (SEM) was used for morphology studies of the fiber. Mechanical properties were identified using MTS Exceed. Tensile strength, tensile modulus, and elongation at break mechanical properties were compared to commercially available natural fibers, such as jute, kenaf, hemp, and flax. After retting, the ragweed fibers were ground up and converted to cellulose acetate through esterification. The soluble cellulose acetate was characterized using Fourier Transform Infrared Spectroscopy (FT-IR) and titrated to determine the degree of esterification. Properties of ragweed based cellulose acetate were compared to commercially sourced cellulose acetate. The resultant cellulose acetate was a soluble polymer that could be electrospun to form a nanofiber. © 2020 Soc. for the Advancement of Material and Process engineering. All rights reserved.

关键词： Cellulose

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FATIGUE AND FATIGUE DAMAGE MECHANISMS OF HIGH-TEMPERATURE THERMOPLASTICS COMPOSITES: A REVIEW 10

FATIGUE AND FATIGUE DAMAGE MECHANISMS OF HIGH-TEMPERATURE TH...

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10th Composites and Advanced materials Expo, CAMX 2024

作者： Sheley, Rahul Tate, Jitendra Tehrani, Mehran Materials Science Engineering and Commercialization Program United States Ingram School of Engineering Texas State University 601 University Drive San MarcosTX78666 United States Jacobs School of Engineering University of California 9500 Gilman DriveLa Jolla San DiegoCA92093 United States

ISBN: (纸本)9781934551462

The growing demand for materials that can withstand extreme conditions in the aerospace and automotive industries has led to significant research on high-temperature polymeric composites. These composites are designed to maintain their structural integrity and mechanical properties at temperatures above 300 degrees Celsius. The development of these advanced materials is crucial for improving the performance and safety of aerospace and automotive components operating in extreme environments. Traditionally, thermosets were the most favorable for working in extreme environmental conditions due to their superior heat resistance and durability. Researchers have recently focused more on the development of reinforced thermoplastic composites. The specific challenges faced by researchers and engineers when developing high-temperature composites include maintaining structural integrity and mechanical properties under extreme conditions. The specific techniques used by researchers to modify and reinforce high-temperature thermoplastics for enhanced performance include the use of advanced nanofillers and their dispersion methods, fiber reinforcement strategies, flame retardant formulations, and toughening agent incorporation. The research has shown promising results in improving the mechanical, thermal, and physical performance of thermoplastics composites. However, challenges remain in predicting the long-term performance and durability of high-temperature thermoplastics in aerospace and automotive environments. These materials are essential for applications requiring thermal and chemical resistance, but their deployment in critical environments exposes them to conditions that can lead to fatigue failure through different mechanisms. These mechanisms include oxidation, thermal degradation, matrix crystallinity changes, fiber-matrix interface degradation, residual stresses, creep, and microcracking. This article aims to review the approaches various authors have adopted to ana

关键词： Durability

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Shallow and Deep States of Beryllium Acceptor in GaN: Why Photoluminescence Experiments Do Not Reveal Small Polarons for Defects in Semiconductors

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Physical Review Letters 2021年第2期126卷 027401-027401页

作者： D. O. Demchenko M. Vorobiov O. Andrieiev T. H. Myers M. A. Reshchikov Department of Physics Virginia Commonwealth University Richmond Virginia 23220 USA Materials Science Engineering and Commercialization Program Texas State University San Marcos Texas 78666 USA

Currently, only one shallow acceptor (Mg) has been discovered in GaN. Here, using photoluminescence (PL) measurements combined with hybrid density functional theory, we demonstrate that a shallow effective-mass state also exists for the BeGa acceptor. A PL band with a maximum at 3.38 eV reveals a shallow BeGa acceptor level at 113±5 meV above the valence band, which is the lowest value among any dopants in GaN reported to date. Calculations suggest that the BeGa is a dual-nature acceptor with the “bright” shallow state responsible for the 3.38 eV PL band, and the “dark,” strongly localized small polaronic state with a significantly lower hole capture efficiency.

关键词： Defects Electronic structure Doped semiconductors Semiconductor compounds Density functional calculations Photoluminescence

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