Morphological Effects on the Materials Properties of Polyimides

1993 ◽  
Vol 323 ◽  
Author(s):  
T. W. Poon ◽  
J. Leu ◽  
Y. S. Kang ◽  
H. C. Liou ◽  
P. S. Ho
Keyword(s):  
Mechanical Strength ◽  
Deformation Energy ◽  
Thermomechanical Properties ◽  
Film Plane ◽  
Polymeric Chain ◽  
Material Strength ◽  
Strong Material ◽  
Rigid Rod ◽  
Interfacial Strain ◽  
Metal Polymer

AbstractWe have carried out a comparative study on the thermomechanical properties and interfacial fracture for two polyimides, a rigid-rod like BPDA-PDA and a flexible-chain PMDA-ODA. This study is focused on the correlation between material strength and polymeric chain morphology. A strong correlation was observed, with high chain packing order giving rise to strong material strength. Quantitatively, the mechanical strength of PMDA-ODA thin films along the direction tangential to the film plane is about 1/3 of that of BPDA-PDA, and its thermal expansivity 1.5 to 5 times larger. For fracture, the mechanical strength of the polyimide plays a different role. A softer polyimide such as PMDA-ODA will strengthen the confinement exerted by the metal lines with smaller interfacial strain, thereby decreasing the amount of deformation transmitted through the interface into the metal, and shifting the onset of delamination to a higher strain on the entire structure. However, the same softer polyimide layer also induces a larger amount of plastic deformation, leading to fracture of the film at a smaller strain. For a strong metal/polymer interface, the strength of the interfacial bonds is sufficient to hold the interface intact while the polymer near the interface deforms plastically because it is much softer mechanically than the metal. This continues until the deformation energy accumulated in the polymer is sufficient to delaminate the interface. Under this condition, the locus of failure will be determined by the relative fracture toughness of the polymer compared with the interface, which may very well occur in the polymer very close to the interface.

Synergism in Binary (MWNT, SLG) Nano-carbons in Polymer Nano-composites: A Raman Study

2013 ◽  
Vol 1505 ◽  
Author(s):  
Peng Xu ◽  
James Loomis ◽  
Ben King ◽  
Balaji Panchapakesan
Keyword(s):  
Mechanical Strength ◽  
Polymer Composites ◽  
Load Transfer ◽  
Synergistic Effects ◽  
Cooperative Behavior ◽  
Single Layer Graphene ◽  
Polymeric Chain ◽  
Uniaxial Tensile ◽  
Advanced Composites ◽  
Nano Carbon

ABSTRACTLoad transfer and mechanical strength of reinforced polymers are fundamental to developing advanced composites. This paper demonstrates enhanced load transfer and mechanical strength due to synergistic effects in binary mixtures of nano-carbon/polymer composites. Different compositional mixtures (always 1 wt. % total) of multi-wall carbon nanotubes (MWNTs) and single-layer graphene (SLG) were mixed in polydimethylsiloxane (PDMS), and effects on load transfer and mechanical strength were studied using Raman spectroscopy. Significant shifts in the G-bands were observed both in tension and compression for single as well binary nano-carbon counterparts in polymer composites. Small amounts of MWNT0.1 dispersed in SLG0.9/PDMS samples (subscripts represents weight percentage) reversed the sign of the Raman wavenumbers from positive to negative values demonstrating reversal of lattice stress. A wavenumber change from 10 cm-1 in compression (-10% strain) to 10 cm-1 in tension (50% strain), and an increase in elastic modulus of ∼103% was observed for MWNT0.1SLG0.9/PDMS with applied uniaxial tension. Presence of MWNTs in the matrix reduced the segmental polymeric chain length and provided limited extensibility to the chains. This in turn eliminated compressive deformation of SLG and significantly enhanced load transfer and mechanical strength of composites in tension. The orientation order of MWNT with application of uniaxial tensile strain directly affected the shift in Raman wavenumbers (2D band and G-band) and load transfer. It is observed that the cooperative behavior of binary nano-carbons in polymer composites resulted in enhanced load transfer and mechanical strength. Such binary compositions could be fundamental to developing advanced composites.

Joining Techniques for Novel Metal Polymer Hybrid Heat Exchangers

2019 ◽  
Author(s):  
Gowtham Kuntumalla ◽  
Yuquan Meng ◽  
Manjunath Rajagopal ◽  
Ricardo Toro ◽  
Hanyang Zhao ◽  
...  
Keyword(s):  
Heat Exchangers ◽  
Waste Heat ◽  
Cost Effective ◽  
The United States ◽  
Thermomechanical Properties ◽  
Low Grade ◽  
Ongoing Work ◽  
Metal Metal ◽  
Low Grade Heat ◽  
Metal Polymer

Abstract In the United States, over 50% of the unrecovered energy from industrial processes is in the form of low-grade heat (< 220°C). Materials and maintenance costs of common heat exchangers are typically too high to justify their usage. Polymers, though more affordable, are usually unsuitable for HX applications due to their low thermal conductivity (∼0.2 W/mK). Here, we show that metal-polymer hybrids may be attractive from both performance and cost perspectives. The use of polymers further increases the resistance to corrosion by sulfuric and carbonic acids often present in flue gases. An ongoing work explores different configurations of layered polyimide-copper macroscale hybrids for heat exchanger applications using numerical simulations. This paper explores a manufacturing pathway for producing such layered hybrid tubes that involves directly rolling and bonding tapes made of polymer and copper foil into tubes. A critical problem in the fabrication process is the bonding of metal and polymers. We explore approaches involving adhesives (epoxy, acrylic and silicone) for metal/polymer interfaces and direct welding (ultrasonic) for metal/metal interfaces that can be integrated into the manufacturing process. We report characterizations of the thermomechanical properties of these joining processes. This work paves the way for realizing cost-effective manufacturing of heat exchangers for low grade waste heat recovery.

Multifunctional Metal/Polymer Hybrid Fiber for Space and Aerospace Applications

2004 ◽  
Vol 851 ◽  
Author(s):  
Jar-Wha Lee ◽  
Dale L. Hart ◽  
Elizabeth T. Shinn ◽  
Abigail J. Cooley ◽  
Edward L. White ◽  
...  
Keyword(s):  
Electromagnetic Interference ◽  
Test Results ◽  
Hybrid Fiber ◽  
Aerospace Applications ◽  
Polymer Hybrid ◽  
Pbo Fiber ◽  
Rigid Rod ◽  
Space Requirements ◽  
Current Carrying Capability ◽  
Metal Polymer

ABSTRACTThe stringent weight and space requirements of advanced space and aerospace systems have lead to a need for stronger, lighter, smaller, and more flexible cable and wiring components. Syscom has fabricated a multifunctional metal/polymer hybrid fiber from a rigid-rod type of polymer, such as poly(p-phenylene benzobisoxazole) (PBO) fiber, for signal transfer and electromagnetic interference (EMI) shielding in wiring and cable applications. The test results indicated that the metal/polymer hybrid PBO fiber exhibited ∼67% the electrical conductivity, ∼73% the weight and ∼200% the tensile strength of a comparable size of beryllium-copper CS95 wire. Additional experimental results of electric current carrying capability, cable shielding performance and atomic oxygen erosion protection will also be discussed.

The Effect of Curing on the Thermomechanical Properties of BPDA-PDA Polyimide Thin Films

1993 ◽  
Vol 323 ◽  
Author(s):  
J. Leu ◽  
Y. S. Kang ◽  
H. C. Liou ◽  
P. S. Ho
Keyword(s):  
Thin Films ◽  
Film Thickness ◽  
Mechanical Strength ◽  
Heating Rate ◽  
Thermomechanical Properties ◽  
Degree Of Crystallinity ◽  
High Heating Rate ◽  
Molecular Order ◽  
Chain Orientation ◽  
High Heating

AbstractThe effect of the heating rate during curing on the thermal expansivity and mechanical properties of poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide thin films has been investigated in the range from 3 to 40 μm, which is commonly used for packaging application. Structural characterization was carried out using birefringence and wide-angle x-ray diffraction (WAXD) techniques. The morphology and packing order are found to be strongly influenced by the heating rate and, to a lesser extent, by the film thickness. The themomechanical properties of the polyimide films show an overall variation consistent with the changes in the molecular packing, thus demonstrating a close structure-property correlation. For slow-cure films, the variation of the molecular order is almost independent of film thickness. In contrast, the molecular order for the fast-cured films strongly depends on the thickness. The in-plane chain orientation decreases, but crystallinity increases with increasing film thickness. The heating rate gives rise to an opposite effect on the morphology for thin (∼ 5 μm) and thick films (∼ 38 μm). For thin films, high heating rate yields a high degree of crystallinity and in-plane chain orientation of the polymeric chains, leading to low thermal expansion coefficient (TEC) and high mechanical strength. In contrast, high heating rate for the thicker film gives a low in-plane chain orientation, leading to high TEC and low mechanical strength. The close correlation between morphology and the thermomechanical properties such as Young's modulus, stress-strain relationship, and lateral TEC is demonstrated.

scholarly journals Evaluation of Different Compatibilization Strategies to Improve the Performance of Injection-Molded Green Composite Pieces Made of Polylactide Reinforced with Short Flaxseed Fibers

Polymers ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 821 ◽  
Author(s):  
Ángel Agüero ◽  
David Garcia-Sanoguera ◽  
Diego Lascano ◽  
Sandra Rojas-Lema ◽  
Juan Ivorra-Martinez ◽  
...  
Keyword(s):  
Mechanical Strength ◽  
Interfacial Adhesion ◽  
Mechanical Performance ◽  
Linseed Oil ◽  
Fiber Surface ◽  
Random Copolymer ◽  
Reactive Extrusion ◽  
Thermomechanical Properties ◽  
Chain Extension ◽  
Green Composite

Green composites made of polylactide (PLA) and short flaxseed fibers (FFs) at 20 wt % were successfully compounded by twin-screw extrusion (TSE) and subsequently shaped into pieces by injection molding. The linen waste derived FFs were subjected to an alkalization pretreatment to remove impurities, improve the fiber surface quality, and make the fibers more hydrophobic. The alkali-pretreated FFs successfully reinforced PLA, leading to green composite pieces with higher mechanical strength. However, the pieces also showed lower ductility and toughness and the lignocellulosic fibers easily detached during fracture due to the absence or low interfacial adhesion with the biopolyester matrix. Therefore, four different compatibilization strategies were carried out to enhance the fiber–matrix interfacial adhesion. These routes consisted on the silanization of the alkalized FFs with a glycidyl silane, namely (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and the reactive extrusion (REX) with three compatibilizers, namely a multi-functional epoxy-based styrene-acrylic oligomer (ESAO), a random copolymer of poly(styrene-co-glycidyl methacrylate) (PS-co-GMA), and maleinized linseed oil (MLO). The results showed that all the here-tested compatibilizers improved mechanical strength, ductility, and toughness as well as the thermal stability and thermomechanical properties of the green composite pieces. The highest interfacial adhesion was observed in the green composite pieces containing the silanized fibers. Interestingly, PS-co-GMA and, more intensely, ESAO yielded the pieces with the highest mechanical performance due to the higher reactivity of these additives with both composite components and their chain-extension action, whereas MLO led to the most ductile pieces due to its secondary role as plasticizer for PLA.

scholarly journals Analysis of the Impact of Changes in Thermomechanical Properties of Polymer Materials on the Machining Process of Gears

Polymers ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 28
Author(s):  
Adam Gnatowski ◽  
Rafał Gołębski ◽  
Piotr Sikora
Keyword(s):  
Surface Condition ◽  
Gear Wheel ◽  
Thermomechanical Properties ◽  
Thermal Modification ◽  
Polymer Materials ◽  
Machining Process ◽  
Material Strength ◽  
Cnc Milling ◽  
Cnc Machine ◽  
The Impact

This paper presents an analysis of the impact of modification of thermomechanical properties of polymer materials on the process of gear wheel machining on a CNC machine tool. Polymer materials Tecaflon (PVDA) and polyethylene (PE) were used for processing. The materials underwent thermal modification i.e., annealing. Prepared samples (gear wheel dimensions Ø76.5 × 20 mm) were machined under the same conditions, only changing the feed rate parameter. A CNC milling machine of its own construction was used for machining with a horizontal numerical dividing attachment. The obtained gear wheels were tested using ZEISS GEAR PRO gear analyzes software. Deviations of the involute outline and the tooth line allowed classification of wheels in the 9th grade of accuracy. Machined teeth surfaces were examined for changes in the properties of surface layer, taking into account the influence of polymer material thermal modification on the surface condition. The samples were tested for mechanical properties (tensile strength) and thermomechanical properties (DSC and DMTA). The tests showed positive changes in material strength and significant improvements in PVDA Tecaflon after heat treatment.

Relationship Between Interfacial Strain and the Elastic Response of Multilayer Metal Film

1988 ◽  
Vol 130 ◽  
Author(s):  
Bruce M. Clemens ◽  
Gary L. Eesley
Keyword(s):  
Film Plane ◽  
Elastic Response ◽  
X Ray Diffraction ◽  
Repeat Distance ◽  
Multilayer Systems ◽  
X Ray ◽  
Interfacial Strain ◽  
Bulk Effect ◽  
Multilayer Metal ◽  
Elastic Softening

AbstractWe have used x-ray diffraction and picosecond transient piezoreflectance to investigate the structural and elastic properties of three distinct multilayer systems: Mo/Ni, Pt/Ni and Ti/Ni. We demonstrate that the commonly observed lattice expansion perpendicular to the film plane is not a bulk effect, but is localized at the interface between the contacting metals. Incorporating the measured interfacial expansion into a universal binding relation, we show that the measured elastic softening versus compositional repeat distance can result from the interfacial strain.

scholarly journals Crystallizing Vanadium Pentoxide Nanostructures in the Solid-State Using Modified Block Copolymer and Chitosan Complexes

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
C. Diaz ◽  
G. Barrera ◽  
M. Segovia ◽  
M. L. Valenzuela ◽  
M. Osiak ◽  
...  
Keyword(s):  
Solid State ◽  
Preparation Method ◽  
Product Formation ◽  
Polymeric Chain ◽  
Calcination Process ◽  
Molar Ratios ◽  
Light Region ◽  
Modified Block ◽  
Metal Polymer ◽  
Coordination Reaction

A systematic study of the synthesis of V2O5nanostructured materials using macromolecular PS-co-4-PVP·(VCl3)yand chitosan·(VCl3)ycomplexes is presented. It is demonstrated that various coordination degrees of the metal into the polymeric chain specifically influence the product formation after pyrolysis. PS-co-4-PVP·(VCl3)yand chitosan·(VCl3)ycomplexes were prepared by simple coordination reaction of VCl3with the respective polymer in molar ratios 1 : 1, 1 : 5, and 1 : 10 metal/polymer and characterized by elemental analysis, IR spectroscopy, and TGA/DSC analysis. Solid-state thermolysis of these precursors at several temperatures under air results in nanostructured V2O5using all precursors. The size and shape of the nanostructured V2O5depend on the nature of the polymer. For the chitosan·(VCl3)yprecursors sub-10 nm nanocrystals are formed. The calcination process, involved in the preparation method, produces V2O5with photoluminescence in the visible light region, suggesting the possible application in oxygen sensing devices.

Efficient Design on Body Strength and Capacitance of MLCC

2010 ◽  
Vol 156-157 ◽  
pp. 724-731
Author(s):  
Ching Ming Cheng ◽  
Yao Hsu ◽  
Wen Fang Wu
Keyword(s):  
Mechanical Strength ◽  
Empirical Equation ◽  
Design Approach ◽  
Design Stage ◽  
Design Parameters ◽  
Material Strength ◽  
Efficient Design ◽  
Material Test ◽  
Body Strength ◽  
Ceramic Capacitor

When designing the capacitance of a Multi-Layer Ceramic Capacitor (MLCC), engineers used to focus on the way to find appropriate combination of the design parameters. These design parameters usually include materials, layer numbers and thicknesses of the electrodes and the dielectrics. However, not considering the mechanical strength in the design stage may lead the manufactured MLCC prototypes to fail in material test, and a redesign is very often needed. Such a design-and-redesign process is inefficient and needs to be improved. The present paper proposes a simple and efficient design approach to replace the traditional one. It first identifies an empirical equation correlating the capacitance of a MLCC to the design parameters based on specifications. The strength of the MLCC can be evaluated in advance with the help of mechanics of material. A design platform which considers simultaneously the capacitance and the material strength under various design parameters can be established. Demonstration of a MLCC design by the developed platform indicates the proposed approach does help engineers improving and speeding their designs.

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