Irradiation Induced Crosslinking in “Green” Polylactic-Acid (PLA) Polymers for Enhanced Strength and Elevated Temperature Applications

2020 ◽  
Author(s):  
W. Jiang ◽  
A. Bakken ◽  
R. P. Taleyarkhan
Keyword(s):  
High Temperature ◽  
Polylactic Acid ◽  
Chemical Engineering ◽  
Elevated Temperatures ◽  
Crosslinking Agent ◽  
Industrial Applications ◽  
Significant Loss ◽  
Crystalline Form ◽  
Photon Irradiation ◽  
Gamma Irradiated

Abstract This paper presents interdisciplinary (nuclear-mechanical-materials-chemical) engineering technology and results pertaining to use of ionization radiation for tailoring “green”, renewable corn-soy based amorphous and crystalline form polymers for use as low-to-high temperature adhesives. Both amorphous and crystalline form polymer forms of such the Polylactic-Acid (PLA) polymer were studied with and without photon irradiation, alongside with and without cross-linking agent. In order to study and enhance the high-temperature application of PLA as a novel, multi-purpose adhesive, small concentrations of the crosslinking agent triallyl isocyanurate (TAIC) were included into molten amorphous and semi-crystalline PLA cast as glue sticks, followed with Co-60 gamma-irradiation. Bond strength variations were studied in tensile mode at room temperature using the resulting adhesive in between two steel dowels (head-to-head bonded) as well as via shear strength testing at elevated temperatures (50–120°C) under a set pre-load of 222 N. It was found that gamma irradiated samples with TAIC exhibited noticeably improved bonding strength, and importantly, such strength can potentially prevail towards 100°C. These are exciting results which offer potential for application for building construction and safety enhancements especially under fires and similar accidents. Samples without TAIC exhibited significant loss of strength past 90°C. The full paper will discuss details of apparatus, modeling and simulation of irradiation dose delivery, testing protocols results, and future enhancements via hybrid neutron-photon-electron irradiation for utility in variety of industrial applications.

Influence of Multifunctional Monomers on Gamma Irradiated Polylactic Acid

2015 ◽  
Vol 804 ◽  
pp. 59-62 ◽  
Author(s):  
Kantima Chaochanchaikul ◽  
Wanlop Harnnarongchai
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Polylactic Acid ◽  
Irradiation Dose ◽  
Crosslinking Agent ◽  
Chain Scission ◽  
Chain Extension ◽  
Molecular Characteristics ◽  
High Irradiation Dose ◽  
Gamma Irradiated

The aim of this work was to compare and discuss the influence of multifunctional monomers as crosslinking agent (Triallyl Isocyanurate; TAIC) and chain extender (Joncryl ADR4368) on the gamma irradiated Polylactic acid (PLA). The modified PLA samples with varying amount of TAIC and Joncryl were characterized by observing the molecular characteristics and mechanical properties. The results showed that irradiated PLA had lower average molar mass and mechanical properties compared to non-irradiated PLA due to irradiation induced chain scission. Gel content was observed and increased with increasing irradiation dose for the TAIC modified sample, indicating that the further crosslink of irradiated PLA was occurring. Crosslinking and chain extension were responsible for the improved modulus and tensile strength of irradiated PLA, however the decrease in tensile strength at high irradiation dose was observed for crosslinked PLA.

scholarly journals Improving the Thermal Stability of Hydrophobic Associative Polymer Aqueous Solution Using a “Triple-Protection” Strategy

Polymers ◽  
2019 ◽  
Vol 11 (6) ◽  
pp. 949 ◽  
Author(s):  
Bo Yang ◽  
Jincheng Mao ◽  
Jinzhou Zhao ◽  
Yang Shao ◽  
Yang Zhang ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Elevated Temperatures ◽  
Polymer Network ◽  
Crosslinking Agent ◽  
Water Soluble ◽  
Fluid Viscosity ◽  
Fracturing Fluid ◽  
Temperature Resistance ◽  
Protection Strategy

Because of their high viscoelasticity, Hydrophobic Associative Water-Soluble Polymers (HAWSPs) have been widely used in many industrial fields, especially in oilfield flooding and fracturing. However, one major problem which limits the wide applications of HAWSPs is their weak resistance to high temperatures. Once the temperature increases over 100 °C, the viscosity of the fracturing fluid decreases rapidly, because high temperatures reduce fluid viscosity by oxidizing the polyacrylamide chains and weakening the association of hydrophobic groups. To improve the high temperature resistance of one HAWSP, a triple-protection strategy was developed. First, rigid N-vinyl-2-pyrrolidone moiety was introduced into the polymer chains. Second, an environmentally-friendly deoxidizer, carbohydrazide, was selected to prevent polymer oxidization by scavenging dissolved oxygen. Results showed that both the rigid groups and the deoxidizer improved the temperature resistance of the polymer and helped it maintain high viscosity under high temperature and shear rate. Using these two protection strategies, the resistant temperature of the polymer could reach 160 °C. However, the polymer network still got severely damaged at further elevated temperatures. Therefore, as the third protection strategy, the pre-added high temperature responsive crosslinking agent was applied to form new networks at elevated temperatures. The results have shown that the optimized polymer solution as a kind of fracturing fluid showed good temperature resistance up to 200 °C.

scholarly journals Mechanical and Microstructural Characterization of Arc-Welded Inconel 625 Alloy

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3690
Author(s):  
Daniel Kotzem ◽  
Lucas Beermann ◽  
Mustafa Awd ◽  
Frank Walther
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Dendritic Structure ◽  
Microstructural Characterization ◽  
Industrial Applications ◽  
High Yield ◽  
Inconel 625 ◽  
Compression Tests ◽  
Static Compression ◽  
Aerospace Material

The objective of this work was to verify a relatively new fusion-based additive manufacturing (AM) process to produce a high-temperature aerospace material. The nickel-based superalloy Inconel 625 (IN625) was manufactured by an arc-based AM technique. Regarding microstructure, typical columnar-oriented dendritic structure along the building direction was present, and epitaxial growth was visible. The mechanical behavior was characterized by a combination of quasi-static tensile and compression tests, whereas IN625 showed high yield and ultimate tensile strength with a maximum fracture strain of almost 68%. Even quasi-static compression tests at room and elevated temperatures (650 °C) showed that compression strength only slightly decreased with increasing temperature, demonstrating the good high-temperature properties of IN625 and opening new possibilities for the implementation of arc-based IN625 in future industrial applications.

scholarly journals Enhanced High-Temperature DC Dielectric Performance of Crosslinked Polyethylene with a Polystyrene Pinning Structure

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1234 ◽  
Author(s):  
Liang Cao ◽  
Lisheng Zhong ◽  
Yinge Li ◽  
Kai Zhang ◽  
Jinghui Gao ◽  
...  
Keyword(s):  
High Temperature ◽  
Direct Current ◽  
Elevated Temperatures ◽  
Breakdown Strength ◽  
Crosslinking Agent ◽  
Special Design ◽  
Insulation Materials ◽  
High Voltage Direct Current ◽  
Dielectric Performance ◽  
Test Temperature Range

In this paper, we propose a method on improving direct current (DC) dielectric performance by designing a polystyrene (PS) pinning crosslinked polyethylene (XLPE) for the application of insulation materials on high voltage direct current (HVDC) extruded cable. Electrical experimental results show that the addition of PS (1–5 phr, parts per hundreds of resin) can significantly reduce DC conductivity and increase DC breakdown strength of XLPE in the test temperature range of 30–90 °C. Microstructure investigation shows PS distributed as particles could participate in the formation of a crosslinking network with the help of a crosslinking agent, thus forming a polymer pinning structure at the interface between XLPE and PS. It is believed that such a special design strengthens the structure of XLPE, which leads to the improved DC dielectric performance at elevated temperatures. Our findings may contribute a new solution for developing HVDC cable insulation materials.

scholarly journals Formation of Solid Lubricants during High Temperature Tribology of Silver-Doped Molybdenum Nitride Coatings Deposited by dcMS and HIPIMS

Coatings ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1415
Author(s):  
Martin Fenker ◽  
Martin Balzer ◽  
Sabine Kellner ◽  
Tomas Polcar ◽  
Andreas Richter ◽  
...  
Keyword(s):  
High Temperature ◽  
Magnetron Sputtering ◽  
Elevated Temperatures ◽  
Indentation Test ◽  
Solid Lubricants ◽  
Industrial Applications ◽  
Film Deposition ◽  
Molybdenum Oxides ◽  
Molybdenum Nitride ◽  
X Ray

The coating system MoN-Ag is an interesting candidate for industrial applications as a low friction coating at elevated temperatures, due to the formation of lubricous molybdenum oxides and silver molybdates. Film deposition was performed by high-power impulse magnetron sputtering and direct current magnetron sputtering. To facilitate a future transfer to industry Mo-Ag composite targets have been sputtered in Ar/N2 atmosphere. The chemical composition of the deposited MoN-Ag films has been investigated by wavelength dispersive X-ray spectroscopy. Morphology and crystallographic phases of the films were studied by scanning electron microscopy and X-ray diffraction. To obtain film hardness in relation to Ag content and bias voltage, the instrumented indentation test was applied. Pin-on-disc tribological tests have been performed at room temperature and at high temperature (HT, 450 °C). Samples from HT tests have been analyzed by Raman measurements to identify possible molybdenum oxide and/or silver molybdate phases. At low Ag contents (≤7 at.%), coatings with a hardness of 18–31 GPa could be deposited. Friction coefficients at HT decreased with increasing Ag content. After these tests, Raman measurements revealed the MoO3 phase on all samples and the Ag2Mo4O13 phase for the highest Ag contents (~23–26 at.%).

Welding Parameters and their Influence on the Abrasion Resistance of Structural Steels at Elevated Temperatures

2016 ◽  
Vol 721 ◽  
pp. 461-466 ◽  
Author(s):  
Harald Rojacz ◽  
Hannes Pahr ◽  
Susanne Baumgartner ◽  
Karl Adam ◽  
Markus Varga
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Abrasion Resistance ◽  
Elevated Temperatures ◽  
Hardness Test ◽  
Industrial Applications ◽  
Structural Steels ◽  
Wear Behaviour ◽  
Welding Parameters ◽  
Hot Hardness

In several industrial applications wear resistance of structural steels is required. Also enhanced temperature can occur when handling hot materials, e.g. in steel industry. Within this study a low alloyed structural steel (carbon steel S355) and a high temperature (HT) 9 % Cr steel ASTM A332 P92 were chosen for investigation. Repair welds with flux cored wires which are often required in applications were investigated, aiming on the role of interpass temperatures, the resulting effect of cooling conditions on the microstructure and their HT abrasion resistance. The influence of different microstructural parameters such as phase content, processing and the resulting temperature-hardness coherence on the wear resistance are evaluated within a high temperature abrasion test and a hot hardness test rig. Results indicate a strong influence of interpass temperature and heat input on the hot hardness and wear behaviour of welded structural steels.

The effect of Sibunit graphitization on the stability of Ru/(Pt, Pd)/Sibunit catalysts in an oxidizing atmosphere at elevated temperatures

2021 ◽  
Vol 1 (1-2) ◽  
pp. 55-61
Author(s):  
V. A. Borisov ◽  
K. N. Iost ◽  
V. L. Temerev ◽  
Yu. V. Surovikin ◽  
A. R. Osipov ◽  
...  
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Analysis Data ◽  
Temperature Treatment ◽  
Significant Loss ◽  
Ruthenium Catalysts ◽  
High Temperature Treatment ◽  
Mean Size ◽  
Temperature Pretreatment ◽  
The Stability

The effect of high-temperature treatment on the thermal stability of a graphitic carbon material Sibunit in an oxidizing medium was studied in dependence on the presence of active component – Pt, Pd or Ru. According to thermal analysis data, a high-temperature pretreatment of Sibunit increases the onset temperature of carbon oxidation. It was found that holding of the Ru/Sibunit samples for 4 h in a nitrogen: air (1 : 1) mixture at a temperature of 400 °С resulted in a partial destruction of the pyrocarbon matrix of Sibunit and increased the mean size of Ru particles. It was demonstrated that ruthenium catalysts can efficiently oxidize CO at a temperature not higher than 200 °С and withstand overheats up to 400 °С without a significant loss in activity.

High-Temperature Instability of A Cr2Nb-Nb(Cr) Microlaminate Composite

1996 ◽  
Vol 54 ◽  
pp. 374-375
Author(s):  
M. Larsen ◽  
R.G. Rowe ◽  
D.W. Skelly
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Aircraft Engine ◽  
Lattice Parameter ◽  
Microstructural Stability ◽  
Elevated Temperature Strength ◽  
Cross Sectional ◽  
Bcc Structure

Microlaminate composites consisting of alternating layers of a high temperature intermetallic compound for elevated temperature strength and a ductile refractory metal for toughening may have uses in aircraft engine turbines. Microstructural stability at elevated temperatures is a crucial requirement for these composites. A microlaminate composite consisting of alternating layers of Cr2Nb and Nb(Cr) was produced by vapor phase deposition. The stability of the layers at elevated temperatures was investigated by cross-sectional TEM.The as-deposited composite consists of layers of a Nb(Cr) solid solution with a composition in atomic percent of 91% Nb and 9% Cr. It has a bcc structure with highly elongated grains. Alternating with this Nb(Cr) layer is the Cr2Nb layer. However, this layer has deposited as a fine grain Cr(Nb) solid solution with a metastable bcc structure and a lattice parameter about half way between that of pure Nb and pure Cr. The atomic composition of this layer is 60% Cr and 40% Nb. The interface between the layers in the as-deposited condition appears very flat (figure 1). After a two hour, 1200 °C heat treatment, the metastable Cr(Nb) layer transforms to the Cr2Nb phase with the C15 cubic structure. Grain coarsening occurs in the Nb(Cr) layer and the interface between the layers roughen. The roughening of the interface is a prelude to an instability of the interface at higher heat treatment temperatures with perturbations of the Cr2Nb grains penetrating into the Nb(Cr) layer.

Electron energy loss near edge structures of intermetallic alloys and grain boundaries in NiAl

1996 ◽  
Vol 54 ◽  
pp. 522-523
Author(s):  
G.A. Botton ◽  
C.J. Humphreys
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Energy Loss ◽  
Grain Boundaries ◽  
Industrial Applications ◽  
Edge Structure ◽  
Structural Applications ◽  
Yield Behaviour ◽  
Late Transition ◽  
Metal Aluminides

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.

Phase transformation and layer evolution in molybdenum disilicide-silicon carbide nanolayered coatings

1994 ◽  
Vol 52 ◽  
pp. 538-539
Author(s):  
H. Kung ◽  
T. R. Jervis ◽  
J.-P. Hirvonen ◽  
M. Nastasi ◽  
T. E. Mitchell ◽  
...  
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Oxidation Resistance ◽  
Elevated Temperatures ◽  
Matrix Material ◽  
Molybdenum Disilicide ◽  
High Temperature Strength ◽  
Cross Sectional ◽  
Good Oxidation Resistance ◽  
Structural Applications

MoSi2 is a potential matrix material for high temperature structural composites due to its high melting temperature and good oxidation resistance at elevated temperatures. The two major drawbacksfor structural applications are inadequate high temperature strength and poor low temperature ductility. The search for appropriate composite additions has been the focus of extensive investigations in recent years. The addition of SiC in a nanolayered configuration was shown to exhibit superior oxidation resistance and significant hardness increase through annealing at 500°C. One potential application of MoSi2- SiC multilayers is for high temperature coatings, where structural stability ofthe layering is of major concern. In this study, we have systematically investigated both the evolution of phases and the stability of layers by varying the heat treating conditions.Alternating layers of MoSi2 and SiC were synthesized by DC-magnetron and rf-diode sputtering respectively. Cross-sectional transmission electron microscopy (XTEM) was used to examine three distinct reactions in the specimens when exposed to different annealing conditions: crystallization and phase transformation of MoSi2, crystallization of SiC, and spheroidization of the layer structures.

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