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In this study, two cardanol based epoxidized resins, NC514 with less than two epoxies per molecule and side chain epoxidized cardanol glycidyl ether (SCECGE) with approximately 2.45 epoxies (1.0 phenolic+1.45 aliphatic epoxies) per molecule were methacrylated. The methacrylated versions of cardanol based NC514 (NC514VE) and SCECGE (SCECGEVE) epoxy resins were used as cross‐linker units in vinyl ester formulations with methacrylated lauric acid (MFA) and styrene (ST) as bio‐based and synthetic based reactive diluents respectively, at various concentrations (10–40 wt%). The curing reactions of the resins were studied via FTIR and the extent of polymerization was determined for different cross‐linker units in the presence of ST and MFA. Our mechanical and thermomechanical characterizations showed that VER formulations prepared with cardanol based SCECGEVE cross‐linker unit have significantly improved properties than the samples prepared with commercially available counterpart NC514VE using either reactive diluent. These properties of SCECGEVE were also comparable with to that of methacrylated petroleum‐based diglycidyl ether of bisphenol A vinyl ester (DGEBAVE) formulations unlike NC514VE formulations due to more effective side chain functionalization and cross‐linking. [ABSTRACT FROM AUTHOR]

PMR-type polyimide resins were prepared in an analogous manner PMR-15 resin is formulated, using two furan-based diamines. The PMR resins from both furan-based diamines showed well-separated transitions that are well-known for PMR-type polyimides, and their oligoimide prepolymers showed lower softening temperatures and cure onsets than PMR-15, making them suitable for lower temperature processing. The cure kinetics of the prepolymers were followed by FTIR spectroscopy. The glass transition and thermal degradation of the crosslinked polyimides were characterized by DMA and TGA which showed in general these polyimides had lower thermal properties than PMR-15. A study on the effects of prepolymer molecular weight was conducted using DFDA to find the optimal stoichiometric number n for better processability and thermal properties. The study determined the polyimide based on DFDA with n = 1.5 had overall a good balance in properties. Its oligoimide precursor softens at 135°C and the cure onset temperature is 231°C. The polyimide has a glass transition temperature of 296°C. Degradation study by TGA showed the lower decomposition temperatures which limit their application temperature to below 300°C. A 1000-h thermo-oxidative stability experiment at 280°C resulted only 6.8% weight loss for DFDA-PI with n = 1.5, making it suitable for high temperature applications around 280°C. [ABSTRACT FROM AUTHOR]

Catalysts are often employed to enable nonisothermal reaction kinetic studies when tracking cure progression of polyurethane reactions. However, when quickly reacting, catalyzed materials are prepared through mixing followed by the addition of fillers or additives, subsequent processing of the partially reacted material becomes difficult. Here, chemorheology is used to track changes in viscoelastic properties of uncatalyzed polybutadiene‐diisocyanate reactions for multiple days, which quantifies the degree of cure during polymerization. Viscosity profiles are accurately captured by the two‐stage Arrhenius model (r2>0.95), and conversion progress is adequately represented by the Kamal–Sourour model (r2>0.76). Transition state analysis via Wynne–Jones–Eyring–Evans theory (WJEE) reveals the presence of an associative mechanism according to entropic and enthalpic activation energies ΔS# = −96.9 J K−1 and ΔH# = 36.4 kJ, respectively. These rheokinetic modeling results align with Fourier transform infrared spectroscopy findings. To the knowledge, no rheokinetic studies have tracked cure progress of this uncatalyzed system for the extended timeframe presented here. The cure profile also presents unique viscosity growth, representative of molecular weight buildup, compared to catalyzed systems. This finding emphasizes the novelty of applying previously developed chemorheological models to multiday thermosetting reactions within a flow field in a manner that is generalizable to many long‐term curing systems. [ABSTRACT FROM AUTHOR]

Dynamic mechanical analysis is commonly used to characterize thermoset polymers at temperatures ranging from well below to well above their glass transition temperatures. Many sample fixtures are available; however, the best clamp and best sample dimensions for a given material are not often readily apparent. Five different epoxy amine networks with glass transitions spanning over 100°C were characterized on three-point bending, dual cantilever, and single cantilever clamps with both constant thickness and constant span-to-thickness. Glassy modulus values were accurately measured on all clamps provided span-to-thickness ratios >10 were maintained. Thermal expansion and decreasing sample stiffness with increasing temperature greatly affect measurements in the rubbery region resulting in single cantilever clamps being best suited to measure rubbery data., INTRODUCTION Dynamic mechanical analysis (DMA) is a common analytical technique used to characterize polymers. DMA is often described as applying an oscillatory force to a sample and measuring the sample's [...]

The use of isosorbide-derived polymers has garnered significant attention in recent decades as a high-performance, renewable material sourced from biomass. Of particular interest is isosorbide methacrylate, which possesses low viscosity (<500 cps), high thermal properties (Tg ≈ 220 °C), and high modulus (>4 GPa). These characteristics present a promising opportunity to replace BPA-derived methacrylate compounds in various applications. This investigation aims to synthesize and characterize isosorbide-based low-viscosity resin systems for 3D printing. The resin blends are composed of isosorbide methacrylate and two bio-renewable methacrylates, furfuryl methacrylate (FM) and bis-hydroxymethyl-furan methacrylate (BHMF-M), polymerized through a digital light processing (DLP) technique. The addition of the bio-based co-monomers serves to enhance the fracture toughness of the brittle isosorbide methacrylate crosslinked homopolymer (GIc = 37 J/m2). The resulting polymers exhibit Tg values greater than 200 °C and GIc around 100 J/m2. These resin systems hold potential for imparting high bio-based content to polymers used in additive manufacturing for high-performance applications. [ABSTRACT FROM AUTHOR]

Vinyl ester and epoxy–amine resins are used to produce polymeric materials for numerous commercial and military applications due to their relatively high moduli (>2 GPa), glass transition temperatures (Tgs) (≥120 °C) and adequate fracture toughness (G1C ≈ 200–250 J m−2). Most commercially available vinyl ester and epoxy–amine resins are typically cured into polymeric materials via traditional manufacturing techniques, such as resin transfer molding and thermal curing. However, additive manufacturing (AM) has gained significant traction as a favorable manufacturing technique over traditional methods due to the ability to create customizable parts with complex geometries on‐demand. Manipulation of polymer network connectivity using a dual‐cure mechanism of methacrylate free radical cure via stereolithography (SLA) and epoxy–amine thermal cure for the in situ creation of interpenetrating polymer networks (IPNs) for AM was investigated. Resins and formulations of individual monomers bearing both vinyl ester and epoxy functionality were either synthesized or formulated to elucidate the effect of interconnecting the two networks at the molecular level. The formation of a multi‐mechanistic, interconnected, sequentially cured IPN via SLA yielded polymeric materials with glass transition temperatures that exceeded 120 °C. Polymer network connectivity was shown to have a minimal impact on thermomechanical and thermogravimetric properties. IPN formation was shown to afford materials with high storage moduli (E′ values as high as 3.2 GPa), tensile strengths (as high as 51 MPa), Young's moduli (exceeding 3.5 GPa) and fracture energies (as high as 790 J m−2). © 2020 Society of Industrial Chemistry [ABSTRACT FROM AUTHOR]

4,4′‐Methylenedianiline (MDA) is utilized to produce high temperature epoxy resins as well as other high‐performance composites; however, MDA is a known carcinogen and liver toxicant. Novel dianilines derived from both petroleum and biomass with different quantities and types of methyl and methoxy substituents on the aromatic ring were prepared and studied to reduce toxicity and carcinogenic aspects of the resulting material while maintaining thermal and mechanical integrity. These dianilines were primarily prepared by coupling commercial anilines using paraformaldehyde under acidic conditions. Another dianiline was prepared by nitration of bisphenol A and subsequent reduction of the nitrates to amines. Structure–toxicity relationships indicate that multiple substituents on the aromatic ring are necessary to reduce the toxicity of the dianiline. Epoxy‐amine resins were prepared by blending the dianilines with 50 wt % Epikure W liquid amine curing agent and mixing with a stoichiometric amount of EPON 828 epoxy resin. Methoxy and methyl substituents increase the melting point of the dianilines by as much as 65 °C, thereby worsening the processing of these monomers as liquid thermoset resins. Structure–property relationships show that the addition of a methoxy group to the aromatic ring and moving the amine from the 4,4′ position on the dianiline reduces the glass transition temperature (Tg) by approximately 10 °C. A single methyl group has little effect on Tg and two methyl groups increase the Tg only when both are ortho to the amine, yet this causes a large 14 °C increase in Tg. Thermal degradation profiles are not significantly affected by the dianiline. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48707. [ABSTRACT FROM AUTHOR]