Dong Hyun Kim

In this study, a bio-based compatibilizer, itaconic acid-grafted polypropylene (PP-g-IA; IP), was synthesized via melt grafting as a sustainable alternative to the conventional petroleum-based maleic anhydride-grafted polypropylene (PP-g-MAH; MP). Successful grafting was confirmed by Fourier-Transform Infrared (FT-IR) spectroscopy, and the efficacy of the synthesized compatibilizer was systematically evaluated by applying it to composites incorporating both unmodified lignocellulose (LC) and hydrophobically modified LC (mLC). Mechanical evaluation revealed that the PP-g-IA-compatibilized LC composite (PPLCIP) achieved the highest tensile strength of 23.5 MPa among all samples. This result is attributed to a synergistic effect: the PP-g-IA compatibilizer significantly improved the interfacial adhesion issue, thereby allowing the intrinsically higher aspect ratio of unmodified LC fibers (3.0 ± 2.1) to serve as the dominant reinforcement factor. While mLC surface modification improved composite performance over unmodified LC even without a compatibilizer, the introduction of a compatibilizer shifted fiber aspect ratio to the dominant factor, resulting in LC-based composites outperforming their mLC-based counterparts. Furthermore, PP-g-IA maintained mechanical performance comparable to that of the conventional PP-g-MAH while simultaneously achieving enhanced melt flowability. These results demonstrate that the bio-based PP-g-IA is an effective and sustainable compatibilization strategy that satisfies both mechanical performance and processability requirements.

Waterborne two-component polyurethane coatings (WPCs) offer an environmentally favorable route to high-performance protective coatings, but their mechanical durability is often limited by inefficient network formation in aqueous systems. In particular, side reactions between polyisocyanate crosslinkers and water and incomplete interdiffusion between dispersed reactive particles can reduce crosslinking efficiency and generate heterogeneous coating matrices. Herein, waterborne polyurethane–acrylate hybrid emulsions (WPUAs) were designed as hybrid polyols to improve the scratch resistance of WPCs without sacrificing high-gloss appearance. Polyurethane (PU) segments were incorporated into acrylic polymer particles to introduce urethane-based hydrogen bonding and improve compatibility between the acrylic and PU components. Structural, particle-size, calorimetric, and thermogravimetric analyses confirmed the formation of colloidally stable WPUA emulsions with composition-dependent PU incorporation. The WPUAs exhibited single glass transition temperature (Tg) behavior, suggesting good apparent compatibility between the acrylic polymer and PU segments, while the slight increase in Tg with PU content indicated restricted segmental mobility. When applied to WPCs, moderate PU incorporation provided the most favorable balance between surface stiffness, gloss, and scratch resistance. In particular, WPC_A92/U8 showed approximately 6.8% higher indentation elastic modulus (EIT) and 23.9% higher critical scratch load (Lc) than the corresponding polyester-containing WPC_A92/E8. By contrast, excessive PU incorporation increased surface roughness and reduced mechanical performance, likely due to restricted particle coalescence and less uniform network formation. These results demonstrate that WPUA hybrid polyols are effective platforms for high-gloss, scratch-resistant, waterborne two-component polyurethane coatings.

Plasticizers play a critical role in polymer processing by reducing melt viscosity and improving moldability and flexibility. They achieve this by weakening intermolecular forces between polymer chains. However, the use of conventional phthalate‐based plasticizers has raised significant concerns due to their endocrine‐disrupting effects, prompting the need for eco‐friendly, biobased alternatives. Therefore, this study aims to synthesize a series of isosorbide‐based plasticizers with varying alkyl chain lengths and blend them with poly(vinyl chloride) (PVC). The resulting films are fabricated via a solution casting method. A distinct shift in the carbonyl absorption band is observed in the plasticized PVC films, indicating improved molecular interactions and miscibility between PVC and the synthesized plasticizers. As the alkyl chain length increases, the tensile strength and hardness of the films improve, while elongation at break decreases. These changes align with shifts in the glass transition temperature ( T _g ). Moreover, compared to epoxidized soybean oil, the isosorbide‐based plasticizers exhibit significantly lower weight loss during thermal aging, demonstrating superior resistance to migration and enhanced thermal stability. These findings provide experimental evidence supporting the potential of isosorbide diesters as sustainable, high‐performance plasticizers for PVC, offering a promising direction for developing safe and effective alternatives to phthalates.

This study aims to synthesize a novel biomass‐based silane coupling agent (SCA) and apply it to epoxy/silica composites (ESCs) for performance evaluation in comparison with commercial SCAs. The novel biomass‐based SCA was prepared by epoxidation of cinnamyl alcohol (CA) extracted from cinnamon leaves, followed by a thiol‐ene reaction with (3‐mercaptopropyl)trimethoxysilane (MPTS). The chemical structure of the synthesized SCA was characterized using Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. This synthesized SCA was applied to ESCs, and its performance was compared to that of ESCs utilizing three different commercial SCAs. The experimental results showed that the viscosity of the ESC mixtures with the synthetic SCA decreased by 19.6%. Additionally, observations of the fractured surface revealed that the synthetic SCA participated in the curing system of the epoxy resin, enhancing interfacial interactions and causing the silica particles to be covered by the epoxy resin, making them no longer visible. This enhanced interfacial interaction, driven by the participation of the synthetic SCA in the curing system, improved the cross‐linking density of the epoxy resin, contributing to an increase in the glass transition temperature (T_g), the temperatures corresponding to 5% weight loss (T_5%), and tensile strength of the ESC by 18.5 °C, 10.8 °C, and 49.7%, respectively. These results support that the synthetic SCA improved the compatibility and bonding strength between the epoxy resin and silica and demonstrate its potential as a replacement for commercial SCAs.Highlights: A novel biomass‐based SCA (CA‐SCA) was synthesized for ESC. The chemical structure of CA‐SCA was confirmed via FT‐IR and ¹HNMR. CA‐SCA participated in the curing reaction, bonding epoxy resin and silica. CA‐SCA has improved the thermal and mechanical properties in ESC.

A post‐crosslinked polyurethane dispersion (PUD) with excellent water resistance was prepared using ethylene glycol diglycidyl ether (EGDGE) as a crosslinker. An anionic PUD was synthesized using dimethylol propionic acid as an internal emulsifier. During the curing process of the PUD film, the hydrophilic carboxylic acid and amine groups of PUD were consumed by the reaction with EGDGE. The reduction of hydrophilic functional groups and the increase of the crosslinking density effectively improved the water resistance of PUD films. In addition, the tensile strength of the PUD film increased from 54.2 MPa to a maximum of 75.3 MPa. The crosslinked structure reduced the crystallinity of the PUD film, which led to an increase in transparency.Highlights: Novel EGDGE‐crosslinked PUD films with enhanced water resistance were developed. PUD samples introduced with EGDGE indicated favorable storage stability. Crosslinking reduced hydrophilic groups, improving thermal and mechanical stability. Optimized EGDGE content (6 wt%) yielded maximum tensile strength (75.3 MPa). Transparency increased due to suppressed phase separation in crosslinked PUDs.

Herein, a novel glycidyl carbamate functional epoxy resin (GCE) is synthesized by the additional reaction of the isocyanate group of tolylene diisocyanate (TDI) with the hydroxyl group of hydroxyl-terminated polybutadiene (HTPB) and glycidol. The successful synthesis of the GCE is confirmed by FT-IR and ¹H NMR spectroscopy. Furthermore, a dual-curing adhesive system is developed using acrylic acid and trimethylolpropane triacrylate with varying GCE contents, and its adhesive performance is assessed by testing adhesive strength, pencil hardness, and surface energy. As a result, the dual-cure adhesive containing 0.2 mol of GCE demonstrates an impressive adhesive strength of 11.1 MPa, a pencil hardness of B, and surface energy comparable to that of standard polycarbonate film.

Waterborne polyurethane (WPU) often suffers from poor water resistance and mechanical properties due to hydrophilic emulsifiers. To address these issues, this study introduces glycidyl carbamate (GC) as a crosslinker to improve WPU performance. Three types of GC were synthesized using aliphatic, cycloaliphatic, and aromatic isocyanates, respectively. The crosslinked network was established through a reaction between the epoxide group of GC and the carboxylic acid and amine groups of WPU. Among these, the WPU film utilizing aromatic isocyanate-based GC exhibited the highest crosslink density, modulus, hardness, and water resistance, due to the rigidity of the aromatic molecular structure. However, the film displayed excessive brittleness, resulting in reduced tensile strength, along with yellowing typically associated with aromatic compounds. The WPU crosslinked with cycloaliphatic GC demonstrated the next best mechanical properties and water resistance, with a 2.7-fold increase in tensile strength, a 1.5-fold increase in hardness, and a 66% reduction in the water swelling ratio compared to neat WPU. This study presents a novel and effective strategy to enhance the water resistance and mechanical properties of WPU films, making them suitable for advanced coating applications.