Search Results (131)

Polysodiumoxy(methyl)siloxane is a highly functional polymer matrix that can be used for the preparation of both functional and non-functional polymers, including molecular brushes. To determine the molecular weight parameters of the matrix, as well as its chemical structure, it is necessary to develop an effective method of blocking functional (in our case, sodiumoxy) groups due to their high reactivity. At the same time, the blocking product should represent a complete non-functionalized replica of polysodiumoxy(methyl)siloxane. Since the obtained polysodiumoxy(methyl)siloxane can contain both sodium- and hydroxy groups in its composition, the presence of both types of functional groups should be considered in the blocking process. In this work, we investigated the blocking process of polysodiumoxy(methyl)siloxane and the influence of blocking conditions on the blocked product. We carried out several variants of blocking, which differed in the order and method of introduction of reagents, as well as in the temperature regime. The chemical structure and molecular weight characteristics of the obtained polymers were analyzed by ¹H NMR spectroscopy and gel permeation chromatography (GPC), respectively. According to the blocking results, only in one case, complete non-functionalized replicas of polysodiumoxy(methyl)siloxane were obtained, which allows this technique to be used as a tool for the analysis of complex, highly functionalized organosilicon systems. Full article

Intense ultraviolet (UV) radiation is often accompanied by large temperature differences in high-altitude cold regions. Therefore, investigating the aging behavior of SBR asphalt under intense UV radiation and large temperature differences is crucial for prolonging the lifespan and maintenance of styrene–butadiene rubber (SBR)-modified asphalt pavements in high-altitude cold regions. This study investigated the aging process of SBR-modified asphalt by analyzing the chemical components, microstructures, and micromechanics of both base and SBR-modified asphalt under combined effects. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), gel permeation chromatography (GPC), and atomic force microscopy (AFM) were utilized to analyze this evolutionary process. The results indicated that the chemical components and microstructural properties of the SBR-modified asphalt underwent significant changes during the aging process under the combined effects of intense UV radiation and large temperature differences. The SBR-modified asphalt exhibited the same aging trend for both the chemical composition and microstructure of the matrix asphalt. However, its aging process in the SBR-modified asphalt was notably slower. This delay was primarily caused by the mesh structure of the SBR-modified asphalt, which created an initial buffer period during aging. Additionally, the degradation of SBR replenished the lost components in the asphalt colloid and inhibited the aging process. The research results indicated that the SBR-modified asphalt exhibited superior aging and cracking resistance with respect to the matrix asphalt. However, the critical cracking time for the surface cracks in the SBR-modified asphalt was earlier than that in the matrix asphalt under the combined effects. It was suggested to use the “modulus ratio” (defined as the Young’s modulus ratio of the surface asphalt layer to the underlying asphalt layer) to quantitatively assess the risk of surface cracking, with a higher modulus ratio indicating a greater risk of cracking or a higher degree of cracking. Full article

Polyimides (PIs) are materials that are resistant to high temperatures and crucial for the manufacturing of films, fibers, coatings, and 3D-printed items. PIs are widely used as electrically insulating materials in electronics and electrical engineering. This study investigated how the chemical structure (i.e., choice of initial monomers), the synthesis conditions of the prepolymer (i.e., choice of amide solvent), and the conditions for forming polyimide films (i.e., final curing temperature) affect the thermophysical properties and short-term electrical strength of obtained polyimide films of different chemical structures. In this work, we varied the compositions of the dianhydrides used for synthesizing polyamic acids—pyromellitic acid (PMDA), tetracarboxylic acid diphenyl oxide (ODPA) and 1,3-bis(3′,4-dicarboxyphenoxy)benzene acid (R)—with a constant diamine: 4,4′-oxydianiline (ODA). Additionally, we varied the amide solvents employed: N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), and N-methyl-2-pyrrolidone (NMP). This study represents the first investigation into how the choice of solvent in the synthesis of thermoplastic polyimide prepolymers affects their short-term electrical strength. The molecular weights of the polyamic acids were determined using gel permeation chromatography (GPC). The deformation and strength characteristics of the investigated films were also assessed. The thermophysical properties of the polyimides were evaluated via dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). X-ray diffraction analysis and infrared spectroscopy (IR) were conducted on the examined film samples. The short-term electrical strength was also evaluated. Full article

In this study, a novel bio-based oxazine resin was synthesized through the reaction of naturally renewable materials: cardanol and furfurylamine. The molecular structure of the target product was confirmed via comprehensive characterization techniques, including Fourier-transform Infrared Spectroscopy (FT-IR), Gel Permeation Chromatography (GPC), Mass Spectrometry (MS), and Nuclear Magnetic Resonance (NMR). Differential Scanning Calorimetry (DSC) revealed that the curing process of cardanol-furfurylamine oxazine (CFZ) exhibited three exothermic peaks (~140, ~240, ~270 °C), which not only helped to optimize the processing conditions but also effectively enhanced the material properties. In the modification experiments, CFZ had been blended and cured with benzoxazine (BZ) at the mass ratios of 2:98, 5:95, 10:90, 20:80, and 40:60. Dynamic Mechanical Thermal Analysis (DMTA) further showed an elevated Loss Factor (tan δ) peak of CFZ-BZ resin, suggesting significantly enhanced toughness. Notably, when the content of the CFZ resin in the composite reached only 5%, the storage modulus achieved its maximum value, highlighting that minimal addition of CFZ resin can optimize the rigidity of the composite, which would drastically reduce material costs and simplify the process. Impact strength testing demonstrated that the impact resistance of CFZ-BZ resin was 6.42 times higher than that of pristine BZ. By integrating renewable materials with rational molecular design, this novel oxazine resin synergistically combines high-temperature resistance, superior toughness, and efficient modification at low loading, positioning it as a promising candidate to replace conventional petroleum-based resins in aerospace, renewable energy, and electronic packaging applications. Full article

In response to the complex pretreatment processes (e.g., solvent dissolution and high-temperature melting) of direct coal liquefaction residue (DCLR) in asphalt, its low-dosage limitation for high-value utilization in asphalt pavement, and the unclear interaction mechanisms between high-proportion DCLR and asphalt, this study comprehensively analyzed the molecular composition and structural characteristics of DCLR at multiple scales using FTIR, GPC, SEM, BET, Tg-FTIR, and XRD. DCLR was crushed to a particle size of 0.15 mm and mixed with 70# base asphalt at mass ratios of 10:100, 15:100, 20:100, 25:100, 30:100, 40:100, and 45:100 at 185 °C to prepare high-proportion DCLR-modified asphalt. The conventional and rheological properties of DCLR-modified asphalt at various dosages were evaluated and compared with those of Buton rock asphalt (BRA)-modified asphalt at equivalent dosages. The results indicated that DCLR and BRA significantly improved the high-temperature performance and PG grade of the base asphalt but reduced its low-temperature performance and grade. At equivalent dosages, DCLR exhibited a more pronounced enhancement in high-temperature performance and a greater reduction in low-temperature performance compared to BRA. High-proportion DCLR-modified asphalt meets the technical requirements for high-modulus asphalt. Using FTIR, GPC, four-component analysis, and elemental analysis, the chemical composition and performance variation trends of high-proportion DCLR-modified asphalt were investigated at multiple scales. The interfacial physical, chemical, and mechanical behaviors between DCLR and base asphalt were characterized. The interaction mechanisms between high-proportion DCLR and asphalt were elucidated, and a novel application strategy for DCLR in asphalt was proposed, significantly enhancing its resource utilization rate in road engineering. Full article

As cement production causes large amounts of CO₂ emissions and is not sustainable, there is a growing worldwide interest in developing cleaner construction materials by reducing carbon emissions and reusing existing industrial waste. Also, antimicrobially active construction materials are gaining attention due to enhancing structural longevity. By preventing microbial growth, these materials help to improve indoor air quality and occupant health. Geopolymer mortars/concretes (GPM/GPC) with high mechanical, physical and durability properties are considered as an eco-friendly alternative to ordinary Portland cement (OPC) mortars/concretes. In this study, the composition, microstructural, mechanical and antimicrobial properties of geopolymers produced at different curing temperatures (60, 80, 100 and 120 °C) were investigated. Low-lime fly ash was used as binder and sodium silicate and sodium hydroxide were used as the alkaline solution in geopolymer production. Although X-ray fluorescence (XRF) results showed an increase in geopolymerization products with increasing temperature, SEM analysis showed that the crack formation that occurs in the microstructure of geopolymers cured above 100 °C leads to decreased mechanical properties. The strength and antimicrobial performance test results for geopolymer mortars showed that the optimum temperature was 100 °C, and the highest compressive strength (48.41 MPa) was reached at this temperature. A decrease in strength was observed due to cracks occurring in the microstructure at higher temperatures. The agar diffusion method was used to determine the antimicrobial activity of GPMs against four bacteria and one fungus species. The antimicrobial activity test results showed that the samples subjected to thermal curing at 100 °C formed the highest inhibition zones (38.94–49.24 mm). Furthermore, the alkalinity of the components/mixtures has a direct relationship with antimicrobial activity. As a result, GPMs with superior antimicrobial and mechanical properties can be considered as promising building materials, especially for construction applications where hygiene is a priority and for structures that are likely to be exposed to microbial corrosion. Full article

Polycarboxylate superplasticizers (PCEs) are the most important polymer admixtures in cement and concrete. Developing novel, green, and efficient synthesis methods is essential for lowering energy consumption. Here, a mechanochemical internal mixing polymerization was used to synthesize high-concentration PCEs (INPCEs) for the first time. The optimum reaction temperature, reaction rotating speed, and reaction time were determined using the orthogonal method. The optimum acid–ether ratio (i.e., the molar ratio of acrylic acid (AA) to isopentenyl polyoxyethylene ether (TPEG)) and concentrations of ammonium persulfate (APS) and sodium methacrylate sulfonate (MAS) were also determined. Finally, the molecular structures of the INPCEs were characterized using Fourier transform infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC), and their performance and energy consumption were compared with PCE synthesized via an aqueous solution polymerization (TPCE). The results showed that the optimum reaction temperature, rotating speed, and time were 60 °C, 70 R/min, and 60 min, respectively. In addition, the acid–ether ratio, the concentrations of MAS and APS, and the polymerization method affected the molecular weight and PDI of INPCEs but did not alter the functional groups. At an AA:TPEG:MAS molar of 3.0:1:0.12 and an APS concentration of 1 wt% (relative to TPEG), the initial fluidity of cement paste with INPCE was 312.5 mm at an INPCE dosage of 0.20 wt% and a water–cement ratio of 0.35. Further, the concentrations of the INPCEs were >99.00 wt%, which is much higher than the TPCE concentration of 39.73 wt%, and the dispersion and dispersion retention of INPCE was almost as good as that of TPCE while requiring much less energy for synthesis. These findings can contribute to the reduction in energy consumption in the concrete industry. Full article

A new poly(azomethine) with improved solubility was successfully prepared by the polycondensation of terephthalaldehyde and 2,2-Bis[4-(4-aminophenoxy)phenyl]-hexafluoropropane (4-BDAF) under green chemistry conditions. This new polymer containing hexafluoroisopropylidene was compared with a polymer containing isopropylidenediphenyl to study the influence of the presence of fluorine atoms on the properties of the polymer. Both were characterized by nuclear magnetic resonance (NMR), their molecular weight was measured by gel permeation chromatography (GPC), and their morphology was studied by X-ray diffraction (XRD). The two polymers obtained were soluble in most polar aprotic solvents and even in less polar solvents, which are practical and easily accessible solvents. Their thermal properties were determined by a thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). These two new polymers showed high resistance to thermal decomposition up to 490 °C, with a glass transition temperature (Tg) of 180 °C. The photophysical properties were studied by UV/Visible absorption. The polymers were doped and then deposited on cellulose filaments, an approach that made it possible to produce self-supporting conductive composites thanks to their mechanical properties. The topography of the resulting materials was characterized at submicron scales before estimating their electronic conductivity and gap energy by diffuse reflection spectroscopy. Full article

Recycling and reutilization of waste PET through alcoholysis has been a prominent focus of current research. However, the alcoholysis process is reversible, leading to the generation of oligomeric waste byproducts. To further utilize these wastes, this paper processed oligomeric waste derived from various alcoholysis systems to synthesize unsaturated polyester resins (UPRs). The fundamental characteristics, mechanical properties, and curing processes of synthesized UPRs were analyzed based on GPC, FTIR, TG, tensile testing, DMA, and DSC tests. The results indicate that wastes were successfully synthesized to UPRs. The UPRs synthesized from ethylene glycol (EG) and diethylene glycol (DEG) possess more complex compositions; among these, the UPR synthesized from EG exhibited higher thermal stability, whereas the UPR synthesized from DEG showed a broader molecular weight distribution and a lower glass transition temperature (T_g). In addition, the UPR synthesized from DEG exhibited a remarkably high elongation at break (>180%), potentially attributed to its long molecular chains. Regarding curing characteristics, UPRs obtained from DEG and propylene glycol (PG) exhibited slower curing rates and demanded higher activation energies. Moreover, the curing processes of UPRs could be well described by the Sesták–Berggren autocatalytic model. Full article

With outstanding resistance for permanent deformation, high-modulus modified bitumen (HMB) has garnered widespread attention in recent years and has been employed in the construction of bitumen pavements across various regions. However, limited research exists on the ageing behaviour of HMB, and conventional short-term ageing protocols for bitumen may not be applicable to HMB due to its exceptionally high viscosity. Therefore, this study aims to assess the ageing behaviour of HMB and propose a suitable short-term ageing process for HMB utilizing dynamic shear rheometer (DSR) and gel permeation chromatography (GPC) approaches. For comparison purposes, the ageing behaviour of a type of SBS-modified bitumen and a kind of base bitumen were also analyzed. Initially, the study involved a comparison of the properties of bitumen subjected to short-term ageing at various temperatures and those of bitumen within mixtures undergoing short-term oven ageing tests. Subsequently, both the chemical and rheological properties of bitumen under diverse ageing conditions were examined. Finally, investigations were conducted to establish relationships between rheological properties and the molecular weight distribution of HMB. The reported results indicate that the suggested ageing temperature for the thin-film oven test (TFOT) should be increased to 193 °C for HMB, achieving a more accurate simulation of short-term ageing in HMB mixtures during on-site mixing, transport, and paving processes. Compared to base bitumen and SBS-modified bitumen, HMB exhibits superior ageing resistance. Furthermore, the molecular weight distribution of HMB is strongly correlated with its rheological properties. This correlation offers a promising approach to predict the rheological properties of bitumen in HMB mixtures by directly analyzing the chemical molecular weight distribution of the binders, thereby eliminating the need for an extraction process. Full article

Aliphatic unsegmented polyurethanes (PUs) have garnered relatively limited attention in the literature, despite their valuable properties such as UV resistance and biocompatibility, making them suitable for biomedical applications. This study focuses on synthesizing poly(ester-urethanes) (PEUs) using 1,6-hexamethylene diisocyanate and the macrodiol α,ω-hydroxy telechelic poly(ε-caprolactone) (HOPCLOH). To optimize the synthesis, a statistical experimental design approach was employed, a methodology not commonly utilized in polymer science. The influence of reaction temperature, time, reagent concentrations, and solvent type on the resulting PEUs was investigated. Characterization techniques included FT-IR, ¹H NMR, differential scanning calorimetry (DSC), gel permeation chromatography (GPC), optical microscopy, and mechanical testing. The results demonstrated that all factors significantly impacted the number-average molecular weight (M_n) as determined by GPC. Furthermore, the statistical design revealed crucial interaction effects between factors, such as a dependence between reaction time and temperature. For example, a fixed reaction time of 1 h, with the temperature varying from 50 °C to 61° C, did not significantly alter M_n. Better reaction conditions yielded high M_n (average: 162,000 g/mol), desirable mechanical properties (elongation at break > 1000%), low levels of unreacted HOPCLOH in the PEU films (OH/ESTER response = 0.0008), and reduced crystallinity (ΔH_m = 11 J/g) in the soft segment, as observed by DSC and optical microscopy. In contrast, suboptimal conditions resulted in low M_n, brittle materials with unmeasurable mechanical properties, high crystallinity, and significant amounts of residual HOPCLOH. The best experimental conditions were 61 °C, 0.176 molal, 8 h, and chloroform as the solvent (ε = 4.8). Full article

Geopolymer concrete (GPC) can be produced by the chemical activation of industrial by-products and processed natural minerals that contain aluminosilicates with the presence of an alkaline activator. Raw components are one of the critical parameters affecting geopolymer performance. On the other hand, the mixing procedure of geopolymer concrete is not any less important. Few demonstrative constructions have been built using GPC as a greener alternative to Portland cement concrete. Numerous variables affect GPC manufacture, such as raw material specification, activator type and dosage, and curing regimes. Despite the conventions of the building industry, the lack of proper mix design methods limits the wide acceptance of GPC in the industry. This report conducted experimental trials on GGBS-based GPC to optimize a mixing design procedure to achieve best mechanical strength and structural integrity. Geopolymer concrete properties were evaluated through slump and unconfined compressive strength tests. The laboratory trials in this report revealed that all geopolymer mixes, except SD0HV and 1W-SG, exhibited high workability values. Also, the presence of an alkaline activator was vital to attain satisfactory compressive strength values. The alkaline activator could be used when cooled and reached room temperature after two hours of preparation and was not necessary after 24 h. Mix G-(0.5W-S) with a 0.5A.A. (alkaline activator)/precursor (GGBS) ratio, SSA (sodium silicate alternative)/SH (sodium hydroxide with 10 M molarity) ratio of 1:1, and 0.55 W/B (water to binder) ratio is recommended to achieve best mechanical performance and structural integrity. Full article

This study investigates the environmental issue of air pollution (PM 2.5) from agricultural waste in Thailand and promotes the utilization of agricultural wastes by using their chemical compositions, especially cellulose content. The fourth readily available varieties of agricultural waste, such as rice straw, corn husk, hemp shive, and durian rind, were selected to evaluate their fiber morphology and chemical properties. Subsequently, dialdehyde carboxymethyl cellulose (DCMC) was produced from four kinds of agricultural wastes under synthesis conditions involving a pH value of 3.0, a reaction temperature of 35 °C, a mass ratio of NaIO₄ and carboxymethyl cellulose (CMC) of 1:3, and a reaction time of 4 h. The formation of aldehyde substitution was confirmed by the degree of oxidation (DO) and aldehyde content. To characterize the DCMC properties determined, Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), gel permeation chromatography (GPC), and scanning electron microscopy (SEM) were used. The results revealed that rice straw, corn husk, hemp shives, and durian rinds presented high DO and aldehyde content; the aldehyde contents were more significant than 30% and 50%, respectively. The highest DO and aldehyde contents were 38.63 and 77.23%, respectively, for the hemp shives. The characterized data in recent research illustrated that the added value of agricultural wastes could be increased by DCMC production, which can be applied as a crosslinking reagent for future novel biopolymer film applications. Full article

Epoxy-terminated hyperbranched polymers (EHBPs) are a class of macromolecular polymers with a hyperbranched structure containing epoxy groups. They possess characteristics such as low viscosity, high functionality, and thermal stability, which endow them with broad application potential in materials science and chemical engineering. This study uses epoxidized soybean oil (ESO) as the raw material, which undergoes ring-opening reactions with glycerol and is esterified with 2,2-bis(hydroxymethyl)propionic acid (DMPA) to obtain epoxy soybean oil polyol (EGD) with a high hydroxyl value. Subsequently, four types of EHBPs are synthesized by incorporating epichlorohydrin (ECH) in mass ratios of 1:3, 1:4, 1:5, and 1:6 under strong alkaline conditions. The product structure is characterized using FT–IR and GPC. The degree of branching of EGD is calculated using ¹H NMR and ¹³C NMR spectroscopy. The epoxy value of EHBPs is tested using the hydrochloric acid–acetone method, and the water contact angle, adhesion properties, rheological properties, and thermal properties of the EHBPs are also evaluated. The results show that the degree of branching of EGD is 0.45. The epoxy values of the EHBPs are 0.73, 0.79, 0.82, and 0.89 mol/100g, respectively. As the epoxy value and molecular weight of the epoxy hyperbranched polymers (EHBPs) increase, the water contact angle and adhesion strength of the EHBPs rise progressively and the viscosity decreases. Additionally, the glass transition temperature increases with the increase in the epoxy value. These epoxy hyperbranched polymers with low viscosity and high adhesion strength offer a promising approach for modifying surface coatings or formulating adhesives. Full article

Polyester-based polyurethane coatings were widely used in automotive, industrial, construction, and plastics industries due to their excellent mechanical properties, adhesion, and relatively outstanding oil and chemical resistance. In these coatings, the type and ratio of polyester and isocyanate curing agents influenced the cohesion energy, hydrogen bonding, crystallinity, crosslinking density, molecular weight, and morphology of the polyurethane at the microscopic level, thereby affecting the macroscopic mechanical properties, electrical performance, and environmental resistance of the material. However, there was limited systematic research on the effect of crosslinking density on the properties of polyester-based polyurethanes. In this study, an HTP-1 system was composed of neopentyl glycol (NPG) and phthalic anhydride (PA), and an HTP-2 system was composed of neopentyl glycol (NPG), hexahydrophthalic anhydride (HHPA), and adipic acid (AA). A series of polyesters (HTPs) were synthesized by adding polyols with different functional groups and adjusting their proportions in the system. The synthesized polyester was characterized using FT-IR, GPC, and DSC, and then cured with polyisocyanate curing agent N3390 to prepare the coating. The following properties of the films were evaluated: adhesion, impact resistance, pencil hardness, gloss, flexibility, oil resistance, and weather resistance. The results showed that in the HTP-1 system, the introduction of dipentaerythritol resulted in a polyester with a broad molecular weight distribution at high hydroxyl values, with a maximum PDI of 12.66 and a glass transition temperature (Tg) reaching 40.19 °C. The polyesters prepared by introducing three types of multifunctional polyols into the HTP-1 system exhibited good impact resistance, adhesion, and hardness. At low hydroxyl values, the coatings demonstrated good flexibility, but due to the lower crosslinking density, the oil resistance was poor. As the hydroxyl value increased, flexibility decreased, while oil resistance improved. In the HTP-2 system, coatings prepared with three different multifunctional polyols showed good impact resistance, flexibility, and hardness at low hydroxyl values but poor adhesion and oil resistance. As the hydroxyl value increased, adhesion improved from grade 1 to grade 0, and oil resistance improved for coatings prepared with trimethylolpropane and ditrimethylolpropane. However, the oil resistance of coatings prepared with dipentaerythritol decreased. Regarding weather resistance, the HTP-1-series resins primarily exhibited the cleavage of -CH₂ groups, while the HTP-2-series resins showed the cleavage of C-N bonds. Overall, the HTP-2 series resins demonstrated better weather resistance. In the high-hydroxyl-value HTP-2 system, the incorporation of trimethylolpropane or ditrimethylolpropane has been shown to produce coatings that achieve a balance among mechanical properties, flexibility, and oil resistance. This finding provides valuable insights for the design and development of high-performance polyester-based polyurethane coatings. Full article