Polymeric Materials Research Articles

Susceptibility to Stress Corrosion Cracking of Selected Amorphous Polymer Materials in a Sea-Water Environment

Susceptibility to Stress Corrosion Cracking of Selected Amorphous Polymer Materials in a Sea-Water Environment

Ultrahigh Heat/Fire-Resistant, Mechanically Robust, and Closed-Loop Chemical Recyclable Polycarbonate Enabled by Facile Bond Dissociation Energy Modulation.

Plastics serve as an essential foundation in contemporary society. Nevertheless, meeting the rigorous performance demands in advanced applications and addressing their end-of-life disposal are two critical challenges that persist. Here, an innovative and facile method is introduced for the design and scalable production of polycarbonate, a key engineering plastic, simultaneously achieving high performance and closed-loop chemical recyclability. The bisphenol framework of polycarbonate is strategically adjusted from the low-bond-dissociation-energy bisphenol A to high-bond-dissociation-energy 4,4'-dihydroxydiphenyl, in combination with the incorporation of polysiloxane segments. As expected, the enhanced bond dissociation energy endows the polycarbonate with an extremely high glow-wire flammability index surpassing 1025°C, a 0.8mm UL-94V-0 rating, a high LOI value of 39.2%, and more than 50% reduction of heat and smoke release. Furthermore, the π-π stacking interactions within biphenyl structures resulted in a significant enhancement of mechanical strength by as more as 37.7%, and also played a positive role in achieving a lower dielectric constant. Significantly, the copolymer exhibited outstanding closed-loop chemical recyclability, allowing for facile depolymerization into bisphenol monomers and the repolymerized copolymer retains its high heat and fire resistance. This work provides a novel insight in the design of high-performance and closed-loop chemical recyclable polymeric materials.

Effects of drilling-induced defects on tensile damage evolution of CFRP laminates

The reliability and service safety of composite structures are compromised by drilling defects on carbon fiber reinforced polymer (CFRP) materials. However, the synergism effect of different types of drilling defects on the mechanical behavior of structures remains unclear. To address this gap, this study focuses on investigating the intralaminar and interlaminar tensile damage evolution response of open-hole CFRP laminates while considering drilling quality. A model is developed, incorporating drilling delamination and tearing defects using the LaRC05 failure criterion and extended finite element method (XFEM). The model implemented in Abaqus/Standard software and the UDMGINI user subroutine is validated through experimentation. Subsequently, three types of open-hole CFRP laminates with typical drilling defect factors are subjected to tensile failure analysis. The results show a notable decline in the mechanical performance of CFRP laminates when drilling defect factors exceed certain levels. Moreover, a progressive damage evolution pattern is analyzed for open-hole CFRP laminates with respect to ply stacking sequences. The interaction between interlaminar delamination propagation and intralaminar crack evolution paths is discussed, highlighting that the concentration of in-plane shear stress primarily influences the location of crack initiation in CFRP laminates.

Isolation and characterization of Banyan Tree Root Filler for Polymer Composites in Light-Weight Applications

Abstract The applicability of bio fillers as reinforcement with polymers is promoted by cost- and environmentally-conscious concerns. Nowadays, a large range of reinforcements are employed for this purpose, including cellulosic fillers and natural fibres owing to the favorable mechanical behavior, minimal price, negligible tool wear, low density, and eco-friendliness etc. The main purpose of the investigation is to explore the possibilities of utilizing plant sources as reinforcing filler in polymeric matrices. In this study particulate fillers were obtained from banyan tree’s aerial roots and were subjected to various characterization such as physiochemical evaluation, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), thermal analysis (TGA), and Scanning Electron Microscopy (SEM). From the physiochemical analysis it was found that the banyan tree aerial root filler (BTAR) contained 40.13% of Cellulose, 15.22% of Hemicellulose, 15.31% of Lignin and 6.86% of Pectin. The density of the BTAR filler was found as 0.27 kg/cc whereas average particle size was 136.3 µm. The maximum inflection temperature referred to the maximum degradation of the BTAR filler was 295.7oC. The SEM analysis exposed the rough surface of filler, with micro-structured strands and pores. The rough surface and the pores could help in better bond ability of the matrix and reinforcement when combined. With these properties the BTAR filler could be a potential candidate as a strengthening material for polymers in different light weight applications.

Fractional modeling of cyclic loading behavior of polymeric materials

Fractional modeling of cyclic loading behavior of polymeric materials

Prussian Blue Encapsulated with Brush-like Polyorganosiloxane Nanospheres with Tunable Functionality

Faced with higher demands of pigments in various applications, the performance of pigments in a specific system is in urgent need of optimization and improvement. Polyorganosiloxane (POS) stands out among various encapsulating polymeric materials for pigment modification due to its superior thermal stability and alkali resistance. However, the inherent hydrophobicity of POS causes poor stability in aqueous systems, which is usually applied in environmentally friendly applications. Grafting hydrophilic polymer chains on the surface of POS could improve water dispersity. In addition, the encapsulated pigment can also be endowed with various functionalities by selecting or combining grafted polymers. Herein, we reported a strategy to encapsulate Prussian blue (PB27) with POS grafted with poly(acrylic acid) (PAA) or poly(N-(2-hydroxyethyl) acrylamide) (PHEAA) to allow better stability and functionality of the composite pigment particles, denoted as PB27@POS@PAA or PB27@POS@PHEAA, respectively. The effect of the number of monomers and the amount of initiator potassium persulfate (KPS) on the brush thickness of the grafted polymers was studied, along with various performance properties and the functionality of PB27@POS@PAA and PB27@POS@PHEAA. The dispersity, alkali resistance, and high-temperature stability are studied. The brush-like composite pigment performs better after centrifugation (5000 rpm, 30 min) or treatment under 90 °C when the dosage of grafting monomer AA or HEAA reaches 400 wt%. Optimal alkali resistance was obtained for PB27@POS@PAA (AA, 200 wt%) with a particle size variation of only 31 nm after 8 h. Comparably, PB27@POS@PHEAA behaved worse under similar conditions. Moreover, PB27@POS grafted with PAA was responsive to pH and that with PHEAA showed excellent antifouling properties, which could also be replaced by other functional monomers if needed.

Effect of addition of γ-poly glutamic acid on bacterial nanocellulose production under agitated culture conditions.

Bacterial nanocellulose (BNC), a natural polymer material, gained significant popularity among researchers and industry. It has great potential in areas, such as textile manufacturing, fiber-based paper, and packaging products, food industry, biomedical materials, and advanced functional bionanocomposites. The main current fermentation methods for BNC involved static culture, as the agitated culture methods had lower raw material conversion rates and resulted in non-uniform product formation. Currently, studies have shown that the production of BNC can be enhanced by incorporating specific additives into the culture medium. These additives included organic acids or polysaccharides. γ-Polyglutamic acid (γ-PGA), known for its high polymerization, excellent biodegradability, and environmental friendliness, has found extensive application in various industries including daily chemicals, medicine, food, and agriculture. In this particular study, 0.15g/L of γ-PGA was incorporated as a medium additive to cultivate BNC under agitated culture conditions of 120rpm and 30℃. The BNC production increased remarkably by 209% in the medium with 0.15g/L γ-PGA and initial pH of 5.0 compared to that in the standard medium, and BNC production increased by 7.3% in the medium with 0.06g/L γ-PGA. The addition of γ-PGA as a medium additive resulted in significant improvements in BNC production. Similarly, at initial pH levels of 4.0 and 6.0, the BNC production also increased by 39.3% and 102.3%, respectively. To assess the characteristics of the BNC products, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis were used. The average diameter of BNC fibers, which was prepared from the medium adding 0.15g/L γ-PGA, was twice thicker than that of BNC fibers prepared from the control culture medium. That might be because that polyglutamic acid relieved the BNC synthesis from the shear stress from the agitation. This experiment held great significance as it explored the use of a novel medium additive, γ-PGA, to improve the production and the glucose conversion rate in BNC fermentation. And the BNC fibers became thicker, with better thermal stability, higher crystallinity, and higher degree of polymerization (DPv). These findings lay a solid foundation for future large-scale fermentation production of BNC using bioreactors.

O/SExchange Reaction in Synthesizing Sulfur-Containing Polymers.

Using carbon disulfide (CS2) and carbonyl sulfide (COS) as sulfur-containing and one-carbon feedstocks to make value-added products is paramount for both pure and applied chemistry and environmental science. One of the practical strategies is to copolymerize these bulk chemicals with epoxides to produce sulfur-containing polymers. This approach contributes to improving the sustainability of polymer manufacturing, provides highly desired functional polymer materials, and has attracted much attention. However, these copolymerizations invariably exhibit the intensely complicated chemistry of O/S exchange reaction, leading to sulfur-containing polymers with diverse architectures. As the understanding of O/S exchange continues to deepen, recent efforts have guided significant advances in the synthesis of CS2- and COS-based polymers. This review examines the O/S exchange chemistry and summarizes the recent progress in this field to promote the further advance of synthesizing sulfur-containing polymers from CS2 and COS.

Current Trends in Liquid Crystal Polymers and Their Applications: A Review

Liquid crystal polymers (LCPs) are now highly focused by researchers due to their improved thermal properties, mechanical strength, excellent dielectric strength, resistance to solvents, better dimensional stability, and gas barrier properties. LCPs can be used in valuable widespread applications such as energy storage, high-performance polymer fibers, actuators, information technologies, surface modification, shape memory materials, data storage, fiber optics, the medical field, electrical or electronics devices, aircraft, chemical, domestic equipment, ultra-high-strength fibers, biosensing, advanced communication systems, satellite systems, biosensing, bio-oscillators, and bioprocess monitoring. LCPs can self-assemble into different liquid crystalline phases like nematic, cholesteric, smectic, and columnar phases. The self-assembling structures of LCPs can be affected by the chemical and structural structures of the backbone of the polymeric material, nearby alkyl tails, mesogenic units, flexible spacers, etc. Depending on the mesogenic units in their molecular architecture, LCPs are basically classified into various categories, such as crosslinked, main chain, and sidechain. Again, they are also classified as cholesteric, nematic, and smectic mesophases. This paper provides a fundamental understanding, an informative overview, and details of structural aspects, properties, classification, commercial aspects, and applications of LCPs.

Preparation and study on H–MoS2/SLS modified SPI@SPEEK blend proton exchange membrane with balanced proton conductivity and stability

Proton exchange membranes (PEMs) are the core components of fuel cells, and research has long focused on how to balance their proton conductivity and durability. In this work, a series of homogeneous blend of sulfonated polyimide (SPI) and sulfonated polyether ether ketone (SPEEK) hybrid membranes with were constructed refined with sulfonated MoS2 (H–MoS2) and sodium lignosulfonate (SLS). The results showed that the tensile strength of the films was enhanced by 39.4% (67.84 MPa) compared to the base film. The composite films incorporating 1 wt% H-MoS2 and 2 wt% SLS has excellent proton conductivity, which can reach 50.24 mS/cm at 80°C and 100% humidity. The embed hybrid structure constructed by H–MoS2 and SLS, which not only effectively solves the limitations of the proton transport channel of traditional polymer materials, but also provides abundant proton transport sites, which provides a new strategy for preparing high-performance PEM.

Influence of Machining Parameters on the Dimensional Accuracy of Drilled Holes in Engineering Plastics

This paper explores the interaction between cutting parameters and the geometric accuracy of machined holes in a variety of engineering plastics, with the aim of improving manufacturing processes in the plastic processing industry. In the context of fast and precise manufacturing technology, the accuracy of drilled holes in polymers is of paramount importance, given their essential role in the assembly and functionality of finished parts. The objective of this research was to determine the influence of cutting speed and feed rate on the diameter and cylindricity of machined holes in six diverse types of plastics using a multilevel factorial design for analysis. The key message conveyed to the reader highlights that careful selection of cutting parameters is crucial to achieving high standards of accuracy and repeatability in plastic processing. The methodology involved structured experiments, looking at the effect of changing cutting parameters on a set of six polymer materials. A CNC machining center for drills and high-precision measuring machines were used to evaluate the diameter and cylindricity of the holes. The results of ANOVA statistical analysis showed a significant correlation between cutting parameters and hole sizes for some materials, while for others the relationship was less evident. The conclusions drawn highlight the importance of optimizing cutting speed and feed rate according to polymer type to maximize accuracy and minimize deviations from cylindricity. It was also observed that, under selected processing conditions, high- and medium-density polyurethane showed the best results in terms of accuracy and cylindricity, suggesting potential optimized directions for specific industrial applications.

Water vapor permeability of polymeric packaging materials for novel glass‐free photovoltaic applications

AbstractMoisture ingress in photovoltaic (PV) modules is a critical factor for performance degradation, therefore, a low water vapor transmission rate (WVTR) is highly desirable for polymers used to embed the solar cells, including backsheets, frontsheets, and encapsulants. With the advent of glass‐free modules for integration in building envelopes and vehicles, there is growing interest in polymer composite structures with embedded glass fibers to enhance rigidity. Furthermore, due to environmental concerns, there is increased interest in fluorine‐free polymers for PV applications. In this work, 21 samples with different base polymers, coatings, and/or surface treatments are investigated and their WVTRs are measured. The results show no good alternatives to existing fluoride‐based polymers/coatings for reducing WVTRs of backsheets and frontsheets among the investigated samples. In addition, glass fibers embedded within polymers to provide increased stability to backsheets or in composites for lightweight PV are shown to significantly increase WVTRs, especially, when fibers are not properly embedded, providing additional diffusion pathways for moisture ingress.

Development and characterization of a coaxial strain-sensing cable integrated steel strand for wide-range stress monitoring

Abstract Monitoring the stress of steel strands, from initial tension to eventual failure, is paramount for assessing structural safety and understanding its failure mechanism. Current monitoring methods are restricted in measuring stress only until yielding because of their limited range. This study proposes a novel coaxial strain-sensing cable (CSSC) based intelligent steel strand (CSSC-ISS), which has both functions of force-bearing and self-sensing. First, the prototype design of CSSC-ISS and the sensing principle of CSSC are introduced. Then, a fabrication method of small-diameter CSSC is proposed, which is then encapsulated with glass fiber reinforced polymer (GFRP) material, forming a GFRP sensing rod (GFRP-SR). The next step involves replacing the strand’s central wire with the GFRP-SR, culminating in the creation of the CSSC-ISS. Finally, Laboratory tests show that the CSSC has excellent strain-sensing performance with a resolution of at least 100 µε and a measurement range of 150,000 µε. The GFRP-SR offers good sensing potential and comparable mechanical strength to standard GFRP rods. Notably, the CSSC-ISS could measure stress up to strand failure, retaining 87.9% tensile strength and 88.7% elastic modulus compared to standard steel strands. It is verified that the CSSC-ISS can consistently measure its stress condition throughout its life cycle without compromising its load-bearing potential.

Promoting Cross-Link Reaction of Polymers by the Matrix-Filler Interface Effect: Role of Coupling Agents and Intermediate Linkers.

The matrix-filler interface effect plays an important role in determining the structural stability and mechanical properties of polymer composite materials, which remain ambiguous and need to be studied. The network-forming dynamics of poly(3,3-bis (azidomethyl) oxetane-tetrahydrofuran) (PBT) at the ammonium perchlorate (AP) surface was studied by using atomistic molecular dynamics simulation, considering the additives of curing agent toluene diisocyanate (TDI), cross-linker trimethylolpropane (TMP), and coupling agent triethanolamine (TEA). The presence of the AP surface promotes chain cross-link reaction, which is attributed to the increased production of intermediate linkers formed by TDI, TMP, and TEA. The intermediate linker has three reactive sites that can react with PBT main chains to form a cross-linked structure. Owing to the strong interaction with the AP surface, the coupling agent TEA plays a dominant role in forming the intermediate linker. At the early stage of network forming (reaction ratio r < 30%), the AP surface adsorbs TEA, which leads to a maximum contact density to PBT. As r increases to 60%, the density of intermediate linkers near the AP surface reaches a maximum value. Consequently, the chain cross-link reactions between the intermediate linker and PBT main chains are enhanced as r > 60%. This work explains the micromechanism of the promotion of chain cross-link reaction by the interface effect and provides important insights on designing polymer materials with high mechanical properties.

Thermally conductive polymer materials with high dielectric characteristics based on oligodimethylsiloxane with terminal hydroxyl groups

The results of studying a polyfunctional heat-resistant composition based on oligodimethylsiloxane with terminal hydroxyl groups filled with boron nitride are presented. The influence of boron nitride on the physical-mechanical, thermophysical and electrical properties of the sealing composition is shown. The dependence of thermal conductivity coefficient, electrical resistivity and other characteristics on the content of the modifier has been established.

The effect of pre-vulcanized latex usage on Marshall characteristics and stiffness modulus in hot mix asphalt wearing course (AC-WC) mixtures

Flexible pavement itself uses asphalt binder as a binding material between aggregates, but with the increasing number of vehicle loads, the ability of flexible pavement needs to be improved. A rubber is a natural polymer material that can be used to improve asphalt mixtures’ performance. This paper aims to analyze the effect of using pre-vulcanized latex on characteristics in hot mix asphalt wearing course mixtures. Pre-vulcanized latex is used as a substitute material for asphalt binder at levels of 7% and 9% by weight. Based on Marshall test results, the AC-WC mixture using pre-vulcanized latex achieved Marshall stability of 11.63 kN or increased by 32.28% at 7% content, while at 9%, it resulted in Marshall stability of 10.69 kN or increased by 21.06%, compared to the specification limit, which is 8.83 kN. The stiffness modulus test results of the asphalt mixture showed that at a temperature of 25°C, there was an increase of 17.46% and 28.26%, respectively, when using pre-vulcanized latex at levels of 7% and 9%. These findings indicate that the use of pre-vulcanized latex as a partial replacement for asphalt has a positive impact on temperature changes in the pavement material.

Enhanced Zinc‐air Batteries through the Fabrication of Structured Zinc Electrodes using Freeze‐casting

Ice templating, a versatile manufacturing process, is widely utilized to create porous materials by freezing aqueous solutions. Notably, this technique is material independent, allowing for the fabrication of microstructured bulk or sheet materials of ceramic, glass, metal, polymer, and composite materials. In this study, the influence of freeze‐cast zinc electrodes on zinc‐air batteries is investigated. The analysis included the charge and discharge cycling behavior of pure powder, gel matrix, and sintered freeze‐cast zinc electrodes, complemented by the study of the distribution of relaxation times. Remarkably, the best cycling performance was achieved with the combination of a gel electrolyte and a freeze‐cast zinc electrode, highlighting the potential significance of this microstructure‐electrolyte pairing for enhancing the performance of zinc‐air batteries.This article is protected by copyright. All rights reserved.

Plasma electrolytic oxidation based superhydrophobic coatings: fabrication, rudiments, and constraints

AbstractPlasma electrolytic oxidation (PEO) has evolved as a versatile technique for depositing low surface energy organic-based materials useful in fabricating superhydrophobic (SHP) coating materials. The application of silane-based polymeric organic materials atop PEO coating is the most common method to prepare coating materials for wetting and corrosion protection. Herein, the latest developments in PEO-based coatings employing polymeric/silane-based organic materials with the inclusion of ceramic oxides are reviewed, with emphasis on the structure, wettability, and corrosion resistance. The relevant and existing fundamental design theories and strategies for fabricating highly efficient SHP PEO coatings are also outlined and discussed. The systemic design of SHP coatings by deposition from organic particle dispersion and their inclusion into PEO-micropore layers, as well as the most important parameters affecting the properties of PEO-assisted SHP-based coatings, are highlighted. Furthermore, the merits and challenges of the PEO-assisted SHP-based coating fabrication are critically evaluated to identify remaining challenges and future research directions.

The Development Cycle of Machining Operations on an Educational CNC Machine

The paper presents a technological analysis, the phases and working methods, as well as the parameters of the processing cycle of a flange for a high-pressure hydraulic gear pump, which has the code FHP-05-12-24, made of polymeric material of ERTALON 66 SA type. The processing was made by cutting with the help of an educational milling and drilling machine with numerical control called EMCO MILL 55 CNC. The commands were programmed through a computer interface, using a conventional numerical code that commands the same kinematic chains, defining specific elements such as the geometric structure of the part, the technological conditions, the structure of the CNC kinematics, the calculation of the programmable coordinates, the parameters of the cutting tools and the parameters of the cutting regime. Based on the characteristics of the polymer material, but also on the identification of programmable functions and routines, the complete development cycle of the complex part processing operations was defined using special functions dedicated to the drilling and milling processes of the profiled surfaces. The part program structure contains program blocks associated with each stage and machining tools. The purpose of the study is to highlight, at an early stage, how students and young researchers can use computer numerical control (CNC) machines, which can be used as a support for the physical processing of complex surfaces, possibly obtained by digitizing and measuring data through a digital correlation based on specialized software products (e.g. GOM Scan, GOM Inspect, FEM analysis, etc.).

Non-Flammable Epoxy Composition Based on Epoxy Resin DER-331 and 4-(β-Carboxyethenyl)phenoxy-phenoxycyclotriphosphazenes with Increased Adhesion to Metals

Functional cyclophosphazenes have proven to be effective modifiers of polymer materials, significantly improving their performance properties, such as adhesive characteristics, mechanical strength, thermal stability, fire resistance, etc. In this study, 4-(β-carboxyethenyl)phenoxy-phenoxycyclotriphosphazenes (CPPP) were obtained by the condensation of 4-formylphenoxy-phenoxycyclotriphosphazene with malonic acid. Its structure was studied using 31P, 1H, and 13C NMR spectroscopy and MALDI-TOF mass spectrometry, and the thermal properties were determined by DSC and TGA methods. Molecular modeling using the MM2 method showed that CPPPs are nanosized with diameters of spheres described around the molecules in the range of 1.34–1.93 nm, which allows them to be classified as nanosized structures. The epoxy resin DER-331 was cured with CPPP, and the conversion of epoxy groups was assessed using IR spectroscopy. Using optical interferometry, it was shown that CPPPs are well compatible with epoxy resin in the temperature range from 80 to 130 °C. It was established that the cured epoxy composition was fire resistant, as it successfully passed the UL-94 vertical combustion test due to the formation of porous coke during the combustion process and also had high heat resistance and thermal stability (decomposition onset temperature about 300 °C, glass transition temperature 230 °C). The composition has low water absorption, high resistance to fresh and salt water, fire resistance, and adhesive strength to steel and aluminum (11 ± 0.2 MPa), which makes it promising for use as an adhesive composition for gluing parts in the shipbuilding and automotive industries, the aviation industry, and radio electronics.