The Role of Surface Treatment and Coupling Agents for Adhesion between Stainless Steel (SUS) and Polyamide (PA) of Heterojunction Bilayer Composites.

The growing demand for lightweight and durable materials in industries, such as the automotive, aerospace, and electronics industries, has spurred the development of heterojunction bilayer composites, combining the structural integrity of metals with the versatility of polymers. This study addresses the critical interface between stainless steel (SUS) and polyamide 66 (PA66), focusing on the pivotal role of surface treatments and various silane coupling agents in enhancing the adhesion strength of heterojunction SUS/PA66 bilayer composites. Through systematic surface modifications-highlighted by scanning electron microscopy, atomic force microscopy, and contact angle analyses-the study assessed the impact of increasing the surface area, roughness, and energy of SUS. X-ray photoelectron spectroscopy evaluations confirmed the strategic selection of specific silane coupling agents. Although some coupling agents barely influenced the mechanics, notably, aminopropyl triethoxysilane (A1S) and 3-glycidyl oxypropyl trimethoxysilane (ES) significantly enhanced the mechanical properties of the heterojunction bilayer composites, evidenced by the improved lap shear strength, elongation at break, and toughness. These advancements were attributed to the interfacial interactions at the metal-polymer interface. This research underscored the significance of targeted surface treatment and the judicious selection of coupling agents in optimizing the interfacial adhesion and overall performance of metal-polymer composites, offering valuable insights for the fabrication of materials where reduced weight and enhanced durability are paramount.

Epoxy-Based Copper (Cu) Sintering Pastes for Enhanced Bonding Strength and Preventing Cu Oxidation after Sintering.

The investigation of interconnection technologies is crucial for advancing semiconductor packaging technology. This study delved into the various methods of achieving electrical interconnections, focusing on the sintering process and composition of the epoxy. Although silver (Ag) has traditionally been utilized in the sintering process, its high cost often precludes widespread commercial applications. Copper (Cu) is a promising alternative that offers advantages, such as cost-effectiveness and high thermal and electrical conductivities. However, the mechanical robustness of the oxide layers formed on Cu surfaces results in several challenges. This research addresses these challenges by integrating epoxy, which has advantages such as adhesive capabilities, chemical resistance, and robust mechanical properties. The chemical reactivity of the epoxy was harnessed to both fortify adhesion and inhibit oxide layer formation. However, the optimal sintering performance required considering both the composite composition (20 wt% epoxy) and the specific sintering conditions (pre-heating at 200 °C and sintering at 250 °C). The experimental findings reveal a balance in the incorporation of epoxy (20 wt%) for the desired electrical and mechanical properties. In particular, the bisphenol A epoxy (Da)-containing sintered Cu chip exhibited the highest lab shear strength (35.9 MPa), whereas the sintered Cu chip without epoxy represented the lowest lab shear strength of 2.7 MPa. Additionally, the introduction of epoxy effectively curtailed the onset of oxidation in the sintered Cu chips, further enhancing their durability. For instance, 30 days after sintering, the percentage of oxygen atoms in the Da-containing sintered Cu chip (4.5%) was significantly lower than that in the sintered Cu chip without epoxy (37.6%), emphasizing the role of epoxy in improving Cu oxidation resistance. Similarly, the samples sintered with bisphenol-based epoxy binders exhibited the highest electrical and thermal conductivities after 1 month. This study provides insights into interactions between epoxy, carboxylic acid, solvents, and Cu during sintering and offers a foundation for refining the sintering conditions.

Catalysis of Silver and Bismuth in Various Epoxy Resins.

Epoxy resins find extensive utility across diverse applications owing to their exceptional adhesion capabilities and robust mechanical and thermal characteristics. However, the demanding reaction conditions, including extended reaction times and elevated reaction temperature requirements, pose significant challenges when using epoxy resins, particularly in advanced applications seeking superior material properties. To surmount these limitations, the conventional approach involves incorporating organic catalysts. Within the ambit of this investigation, we explored the catalytic potential of metallic powders, specifically bismuth (Bi) and silver (Ag), in epoxy resins laden with various curing agents, such as diacids, anhydrides, and amines. Metallic powders exhibited efficacious catalytic activity in epoxy-diacid and epoxy-anhydride systems. In contrast, their influence on epoxy-amine systems was rendered negligible, attributed to the absence of requisite carboxylate functional groups. Additionally, the catalytic performance of Bi and Ag are different, with Bi displaying superior efficiency owing to the presence of inherent metal oxide layers on its powder surfaces. Remarkably, the thermal and mechanical properties of uncatalyzed, fully cured epoxy resins closely paralleled those of their catalyzed counterparts. These findings accentuate the potential of Bi and Ag metal catalysts, particularly in epoxy-diacid and epoxy-anhydride systems, spanning a spectrum of epoxy-based applications. In summary, this investigation elucidates the catalytic capabilities of Bi and Ag metal powders, underscoring their ability to enhance the curing rate of epoxy resin systems involving diacids and anhydrides but not amines. This research points toward a promising trajectory for multifarious epoxy-related applications.

Correction to "Electrical and Thermal Properties of Surface-Modified Copper Nanowire/Polystyrene Nanocomposites through Latex Blending".

[This corrects the article DOI: 10.1021/acsomega.3c06775.].

Electrical and Thermal Properties of Surface-Modified Copper Nanowire/Polystyrene Nanocomposites through Latex Blending.

The incorporation of conductive nanofillers into an insulating polymer matrix commonly leads to nanocomposites with good electrical, thermal, and mechanical properties. In this study, copper nanowires (CuNWs) and polystyrene (PS) microspheres were synthesized along with the fabrication of CuNW/PS polymer nanocomposites. The electrical, thermal, mechanical, rheological, and morphological properties of the CuNW/PS nanocomposites were examined. The CuNWs were homogeneously dispersed in the PS matrix through latex blending. For the CuNW/PS nanocomposites, the storage modulus was higher than the loss modulus at all frequencies, indicating their elastic-dominant behavior. The electrical and thermal conductivities of the nanocomposites increased with an increasing CuNW content. Using a mixed dispersion of two monodisperse PS particles of 500 nm and 5 µm in diameter resulted in the highest electrical conductivity (ca. 10° S/m for 30 wt % nanofillers) among the nanocomposites. In addition, the introduction of silica- and polydopamine-coated CuNWs as nanofillers imparted insulation properties to the nanocomposites, with electrical conductivities to 10-10-10-8 S/m. When using 500 nm PS particles, the thermal conductivity of the surface-modified CuNW/PS nanocomposite at 30 wt % of CuNW was enhanced to 0.22 W/m·K compared to 0.17 W/m·K for its unmodified counterpart. We have achieved multiple innovative approaches, including the use of mixed particle sizes, surface modification of CuNW, and the exploration of elastic-dominant behavior. This enhanced thermal conductivity, coupled with the attainment of insulation properties, presents a distinct advantage for thermal interface material (TIM) applications.

Copper Sintering Pastes with Various Polar Solvents and Acidic Activators.

Devices in the developing semiconductor market require high density, high integration, and detailed processing. Conventional wire bonding is inappropriate for fine-sized devices, and connected wires can be damaged by heat generation and external physical impact. Soldering is also used in advanced packaging technologies. However, disturbances and overhead joints can occur during bonding. Thus, sintering has been extensively utilized to overcome these drawbacks. Sintering pastes are pressurized and bonded, resulting in stable bonding during sintering. In this study, the composition of the Cu sintering material was examined using diverse additives and solvents. We manufactured sintering materials comprising Cu (1 µm), a solvent [methanol (MeOH), ethanol (EtOH), or ethylene glycol (EG)] and an acidic additive (benzoic acid, phthalic acid, or hexanoic acid). After the sintering process, the mechanical and electrical characteristics were compared to determine the optimal composition and bonding conditions. The optimum ratios between the acid and solvent were 4:6 (MeOH and EtOH) and 2:8 (EG) due to the high viscosity and effective long-term storage. All samples using EtOH as the solvent exhibited the highest sintering performances. The aromatic and carboxylic groups substantially improved the sintering performance and increased the electrical conductivity. Based on the O1s/Cu2p ratio (2.23%), the best sintering composition was EtOH/PA, which showed the highest electrical conductivity (ca. 104 S/m) and strength (34.0 MPa). The sintering process using various additives and solvents can be helpful to determine the sintering conditions while maintaining the electrical properties.

Effects of Filler Functionalization on Filler-Embedded Natural Rubber/Ethylene-Propylene-Diene Monomer Composites.

Natural rubber (NR) presents a number of advantages over other types of rubber but has poor resistance to chemicals and aging. The incorporation of ethylene propylene diene monomer (EPDM) into the NR matrix may be able to address this issue. Mineral fillers, such as carbon black (CB) and silica are routinely incorporated into various elastomers owing to their low cost, enhanced processability, good functionality, and high resistance to chemicals and aging. Other fillers have been examined as potential alternatives to CB and silica. In this study, phlogopite was surface-modified using 10 phr of compatibilizers, such as aminopropyltriethoxysilane (A1S), aminoethylaminopropyltrimethoxysilane (A2S), or 3-glycidoxypropyltrimethoxysilane (ES), and mixed with NR/EPDM blends. The effects of untreated and surface-treated phlogopite on the mechanical properties of the rubber blend were then compared with those of common fillers (CB and silica) for rubbers. The incorporation of surface-modified phlogopite into NR/EPDM considerably enhanced various properties. The functionalization of the phlogopite surface using silane-based matters (amino- and epoxide-functionalized) led to excellent compatibility between the rubber matrix and phlogopite, thereby improving diverse properties of the elastomeric composites, with effects analogous to those of CB. The tensile strength and elongation at break of the phlogopite-embedded NR/EPDM composite were lower than those of the CB-incorporated NR/EPDM composite by 30% and 10%, respectively. Among the prepared samples, the ES-functionalized phlogopite showed the best compatibility with the rubber matrix, exhibiting a tensile strength and modulus of composites that were 35% and 18% higher, respectively, compared with those of the untreated phlogopite-incorporated NR/EPDM composite. The ES-functionalized phlogopite/NR/EPDM showed similar strength and higher modulus (by 18%) to the CB/NR/EPDM rubber composite, despite slightly lower elongation at break and toughness. The results of rebound resilience and compression set tests indicated that the elasticity of the surface-modified phlogopite/NR/EPDM rubber composite was higher than that of the silica- and CB-reinforced composites. These improvements could be attributed to enhancements in the physical and chemical interactions among the rubber matrix, stearic acid, and functionalized (compatibilized) phlogopite. Therefore, the functionalized phlogopite can be utilized in a wide range of applications for rubber compounding.

Physical and Chemical Compatibilization Treatment with Modified Aminosilanes for Aluminum/Polyamide Adhesion.

Metal/polymer bilayer composites feature high strength-to-weight ratios and low manufacturing costs despite the weak interfacial adhesion between their components. In this study, aluminum surfaces were modified to generate microporous architectures and hydroxyl moieties by various physical and chemical treatments, including thermal, plasma, anodizing, and hexafluorozirconic acid treatments to overcome the weak interfacial adhesion. The maximum shear strength of the obtained metal/polymer bilayer composites was achieved by anodizing treatment, whereas all treatment methods substantially improved the material toughness. In addition, modified compatibilizing agents with tailorable hydroxyl moieties were applied to enhance the interfacial adhesion using aminoethylaminopropyl trimethoxysilane (AEAPS) and modified AEAPS as a coupling agent. AEAPS modified by monoepoxide (glycidol) produced the strongest positive effect on the composite mechanical properties. These findings can be useful in a myriad of metal/polymer multilayer composites.

Influence of Ionomer and Cyanuric Acid on Antistatic, Mechanical, Thermal, and Rheological Properties of Extruded Carbon Nanotube (CNT)/Polyoxymethylene (POM) Nanocomposites.

The electrical properties of carbon-based filler-embedded polymer nanocomposites are essential for various applications such as antistatic and electromagnetic interference (EMI) applications. In this study, the impact of additives (i.e., ethylene-co-acid-co-sodium acid copolymer-based ionomer and cyanuric acid) on the antistatic, mechanical, thermal, and rheological properties of extruded multiwalled carbon nanotube (MWCNT)/polyoxymethylene (POM) nanocomposites were systematically investigated. The effects of each additive and the combination of additives were examined. Despite a slight reduction in mechanical properties, the incorporation of ionomer (coating on CNTs) and/or cyanuric acid (π-π interaction between CNTs and cyanuric acid) into the POM/CNT nanocomposites improved the CNT dispersity in the POM matrix, thereby enhancing electrical properties such as the electrical conductivity (and surface resistance) and electrical conductivity monodispersity. The optimum composition for the highest electrical properties was determined to be POM/1.5 wt% CNT/3.0 wt% ionomer/0.5 wt% cyanuric acid. The nanocomposites with tunable electrical properties are sought after, especially for antistatic and EMI applications such as electronic device-fixing jigs.

Electrically Conductive Silicone-Based Nanocomposites Incorporated with Carbon Nanotubes and Silver Nanowires for Stretchable Electrodes.

Stretchable electrode materials have attracted great attention as next-generation electronic materials because of their ability to maintain intrinsic properties with rare damage when undergoing repetitive deformations, such as folding, twisting, and stretching. In this study, an electrically conductive PDMS nanocomposite was manufactured by combining the hybrid nanofillers of carbon nanotubes (CNTs) and silver nanowires (AgNWs). The amphiphilic isopropyl alcohol molecules temporarily adhered simultaneously to the hydrophobic CNT and hydrophilic AgNW surfaces, thereby improving the dispersity. As the CNT/AgNW ratio (wt %/wt %) decreased under the constant nanofiller content, the tensile modulus decreased and the elongation at break increased owing to the poor interaction between the AgNWs and matrix. The shear storage moduli of all nanocomposites were higher than the loss moduli, indicating the elastic behavior with a cross-linked network. The electrical conductivities of the nanocomposite containing the hybrid nanofillers were superior to those of the nanocomposite containing either CNT or AgNW at the same filler content (4 wt %). The hybrid nanofillers were rearranged and deformed by 5000 cyclic strain tests, relaxing the PDMS matrix chain and weakening the interfacial bonding. However, the elastic behavior was maintained. The dynamic electrical conductivities gradually increased under the cyclic strain tests due to the rearrangement and tunneling effect of the nanofillers. The highest dynamic electrical conductivity (10 S/m) was obtained for the nanocomposite consisting of 2 wt % of CNTs and 2 wt % of AgNWs.

Near-Infrared Light-Responsive Shape Memory Polymer Fabricated from Reactive Melt Blending of Semicrystalline Maleated Polyolefin Elastomer and Polyaniline.

A shape memory polymer was prepared by melt mixing a semicrystalline maleated polyolefin elastomer (mPOE) with a small amount of polyaniline (PANI) (up to 15 wt.%) in an internal mixer. Transmission electron microscopy (TEM), FTIR analysis, DMA, DSC, melt rheological analysis, and a tensile test were performed to characterize the structure and properties of the mPOE/PANI blends. The results revealed that the blends form a physically crosslinked network via the grafting of PANI onto the mPOE chains, and the PANI dispersed at the nanometer scale in the POE matrix served as a photo-thermal agent and provided increased crosslinking points. These structural features enabled the blends to exhibit a shape memory effect upon near-infrared (NIR) light irradiation. With increasing PANI content, the shape recovery rate of the blend under NIR stimulation was improved and reached 96% at 15 wt.% of PANI.

Phlogopite-Reinforced Natural Rubber (NR)/Ethylene-Propylene-Diene Monomer Rubber (EPDM) Composites with Aminosilane Compatibilizer.

Rubber compounding with two or more components has been extensively employed to improve various properties. In particular, natural rubber (NR)/ethylene-propylene-diene monomer rubber (EPDM) blends have found use in tire and automotive parts. Diverse fillers have been applied to NR/EPDM blends to enhance their mechanical properties. In this study, a new class of mineral filler, phlogopite, was incorporated into an NR/EPDM blend to examine the mechanical, curing, elastic, and morphological properties of the resulting material. The combination of aminoethylaminopropyltrimethoxysilane (AEAPS) and stearic acid (SA) compatibilized the NR/EPDM/phlogopite composite, further improving various properties. The enhanced properties were compared with those of NR/EPDM/fillers composed of silica or carbon black (CB). Compared with the NR/EPDM/silica composite, the incompatibilized NR/EPDM/phlogopite composite without AEAPS exhibited poorer properties, but NR/EPDM/phlogopite compatibilized by AEAPS and SA showed improved properties. Most properties of the compatibilized NR/EPDM/phlogopite composite were similar to those of the NR/EPDM/CB composite, except for the lower abrasion resistance. The NR/EPDM/phlogopite/AEAPS rubber composite may potentially be used in various applications by replacing expensive fillers, such as CB.

Impact Modifiers and Compatibilizers for Versatile Epoxy-Based Adhesive Films with Curing and Deoxidizing Capabilities.

Epoxy resins with acidic compounds feature adhesion, robustness, and deoxidizing ability. In this study, hybrid adhesive films with deoxidizing and curing capabilities for semiconductor packaging were fabricated. The compatibilizing effects and mechanical properties were chiefly investigated by using various additive binders (thermoplastic amorphous polymers) and compatibilizing agents. The curing, deoxidizing, thermal, and rheological properties were systematically investigated. For uniform film formation and maximizing deoxidizing curable abilities, a thermoplastic--thermoset mixture containing a phenyl and carboxylic acid-based additive (benzoic acid), and a polycarbonate was chosen as the model adhesive film. Without either a phenyl or an acidic group in the compatibilizing agent, deoxidizing and compatibilizing effects were not achieved. The manufactured hybrid adhesive film can be effectively used, especially for electronic devices that require deoxidization and adhesion.

Morphology, Mechanical Properties and Shape Memory Effects of Polyamide12/Polyolefin Elastomer Blends Compatibilized by Glycidylisobutyl POSS.

Small amounts of glycidylisobutyl polyhedral oligomericsilsesquioxane (G-POSS) (up to 10 phr) were added into a immiscible polyamide12 (PA12)/polyolefin elastomer (POE) blend (70 wt%/30 wt%) by simple melt mixing. The effects of the G-POSS on phase morphology and mechanical properties were investigated by FE-SEM, tensile testing, Izod impact test and dynamic mechanical analysis. FE-SEM analysis revealed that domain size of the dispersed POE phase in matrix PA12 is decreased significantly by adding the G-POSS, indicating a compatibilization effect of the G-POSS for the immiscible PA12/POE blend. The PA12/POE blend compatibilized with POSS showed simultaneous enhancement in mechanical properties including tensile modulus, strength and toughness. Further, thermally triggered shape memory effect was observed in this compatibilized blend.

Vertically aligned nanostructured gold microtube assisted by polymer template with combination of wet phase inversion and Cu grid mask.

Tubular architecture has been extensively exploited in diverse applications such as solar cells and sensors. However, the synthesis of microtubes with high aspect ratio using polymer templates has been rarely reported. In this study, we designed a facile avenue for the synthesis of well-aligned Au nanoparticle-agglomerate microtubes with an aspect ratio of ~ 30 using a hollow polyetherimide (PEI) template. The combination of wet phase inversion and use of a Cu grid mask enabled straightforward production of a hollow PEI template with vertically aligned tubular architecture. During wet-phase inversion, exchange between a solvent (N-methyl-2-pyrrolidone) and a non-solvent (water) occurred at the corners of the square mask cells rather than along their side, thereby producing pores at the corners due to geometrical and entropic factors. The hollow microtubes were comprised of agglomerated Au nanoparticles that coated the inner surfaces of the pores during an electroless plating process performed after wet-phase inversion. This finding is applicable to diverse applications such as sensors and catalysis.

Porous polyimide membranes prepared by wet phase inversion for use in low dielectric applications.

A wet phase inversion process of polyamic acid (PAA) allowed fabrication of a porous membrane of polyimide (PI) with the combination of a low dielectric constant (1.7) and reasonable mechanical properties (Tensile strain: 8.04%, toughness: 3.4 MJ/m3, tensile stress: 39.17 MPa, and young modulus: 1.13 GPa), with further thermal imidization process of PAA. PAA was simply synthesized from purified pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in two different reaction solvents such as γ-butyrolactone (GBL) and N-methyl-2-pyrrolidinone (NMP), which produce Mw/PDI of 630,000/1.45 and 280,000/2.0, respectively. The porous PAA membrane was fabricated by the wet phase inversion process based on a solvent/non-solvent system via tailored composition between GBL and NMP. The porosity of PI, indicative of a low electric constant, decreased with increasing concentration of GBL, which was caused by sponge-like formation. However, due to interplay between the low electric constant (structural formation) and the mechanical properties, GBL was employed for further exploration, using toluene and acetone vs. DI-water as a coagulation media. Non-solvents influenced determination of the PAA membrane size and porosity. With this approach, insight into the interplay between dielectric properties and mechanical properties will inform a wide range of potential low-k material applications.

Catalytic behavior of Sn/Bi metal powder in anhydride-based epoxy curing.

In this paper, we report the catalytic activity of the Sn/Bi alloy beads and its acceleration of the exothermic epoxy curing reactions in various thermal conditions and bead compositions. As being used as low-melting solder balls in electronic interconnection processes with various epoxy systems, it was found that the Sn/Bi beads substantially lowered the exothermic peak temperature of the diglycidyl ether of bisphenol A (DGEBA)/anhydride systems in up to ca. 140 degrees C depending on different types of anhydride curing agents. The catalytic activation of Sn/Bi powder was initiated with a small amount of Sn/Bi powder, for example, lowering ca. 50 degrees C of the exothermic peak temperature by adding only 0.1 vol% of Sn/Bi powder. The catalytic capability of the powder was increased by using smaller sized beads corresponding to larger catalytic surface area at the same volume fraction. Exhibiting a latent catalytic effect, the catalytic activity of Sn/Bi powder was remained latent at temperatures lower than 100 degrees C in isothermal conditions.

Fabrication of poly(3-hexylthiophene) thin films by vapor-phase polymerization for optoelectronic device applications.

The vapor-phase polymerization (VPP) of poly(3-hexylthiophene) (P3HT) was achieved successfully as an alternative method to conventional solution-based thin film fabrication. Using Fe(III)Cl(3).6H(2)O, a spontaneous reaction of 3-hexylthiophene monomers resulted in the rapid formation of conducting P3HT thin films directly on substrates, such as glass, indium-tin-oxide, and poly(ethylene terephthalate), at thicknesses ranging from 50 to 1000 nm. The VPP of P3HT was achieved using ferric chloride hexahydrate and a 1:1 ratio of a methanol/ethanol mixture as the solvent system. The developed VPP technique can provide good processing consistency with an electrical conductivity, a transmittance, and a surface roughness of approximately 10(-2) S/cm, >90%, and <10 nm, respectively.