ABSTRACT
Bio-based vitrimers present a promising solution to the issues associated with non-renewable and non-recyclable attributes of traditional thermosetting resins, showcasing extensive potential for diverse applications. However, their broader adoption has been hindered by the requirement for catalyst inclusion during the synthesis process. In this study, a cardanol-based curing agent with poly-hydroxy and tertiary amine structures was prepared by a clean synthetic method under the theory of click chemistry. The reaction of a cardanol-based curing agent with diglycidyl ether of bisphenol A formed catalyst-free, self-healing, and recyclable bio-based vitrimers. The poly-hydroxy and tertiary amine structures in the vitrimers promoted the curing of epoxy-carboxylic acid in the cross-linked network and served as internal catalysts of dynamic transesterification. In the absence of catalysts, the vitrimers network can achieve topological network rearrangement through dynamic transesterification, exhibiting excellent reprocessing performance. Moreover, the vitrimers exhibited faster stress relaxation (1500 s at 180 °C), lower activation energy (92.29 kJ·mol-1) and the tensile strength of the recycled material reached almost 100% of the original sample. This work offers a new method for preparing cardanol-based epoxy vitrimers that be used to make coatings, hydrogels, biomaterials, adhesives, and commodity plastics in the future.
ABSTRACT
Herein, a bio-based plasticizer ketalized tung oil butyl levulinate (KTBL) was developed using methyl eleostearate, a derivative of tung oil, and butyl levulinate. KTBL can be used as an auxiliary plasticizer to partially replace traditional plasticizer. The plasticizer has a ketone structure, an ester base, and a long linear chain. It was mixed with dioctyl phthalate (DOP), and the effect of the plasticizer KTBL as an auxiliary plasticizer on the plasticization of poly(vinyl chloride) (PVC) was studied. Their compatibility and plasticizing effect were evaluated using dynamic-mechanical thermal analysis (DMA), mechanical property analysis, and thermogravimetric analysis (TGA). The results demonstrate that when the KTBL to DOP ratio is 1:1, the blended sample with KTBL exhibits superior mechanical performance compared to pure DOP, resulting in an increased elongation at break from 377.47% to 410.92%. Moreover, with the increase in KTBL content, the durability is also significantly improved. These findings suggest that KTBL can serve as an effective auxiliary plasticizer for PVC, thereby reducing the reliance on DOP.
ABSTRACT
Polyurethane is widely used to toughen epoxy resins due to its excellent comprehensive properties and compatibility. However, some demerits of polyurethanes limit their applications, such as the harsh storage condition of isocyanate-terminated polyurethane (ITPU), the limited amount of ITPU in epoxy resin, and using solvents during the preparation of polyurethane-modified epoxy resins. To address these issues, in this study, we reported a facile and green approach for preparing epoxy-terminated polyurethane (EPU)-modified epoxy resins with different EPU contents. It was found that the toughness of the epoxy resin was significantly improved after the addition of EPU. When the EPU content was 30 wt%, the elongation at break and toughness were improved by 358.36% and 73.56%, respectively. In comparison, the toughening effect of EPU outperformed that of ITPU. Moreover, the high content of EPU did not significantly decrease the glass transition temperature and had little effect on the thermal stability of the epoxy resin.
ABSTRACT
Hydrothermal liquefaction (HTL) has been proved to be an efficient method to disrupt cell walls and extract lipids from oleaginous yeast. However, many steps are needed for converting bio-oil into fatty acid methyl esters after HTL. Herein, acidic ionic liquid 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO4]) was introduced as the catalyst in HTL to convert oleaginous yeast Rhodosporidium toruloides to biodiesel in one step. [Bmim][HSO4] has dual effects on cell wall disruption and transesterification in reactions. As a result, the biodiesel yield achieved as high as 15.1 ± 3.2 % in optimal condition. The biodiesel was composed of long chain fatty acid methyl esters, and the higher heating value was 40.62 ± 0.05 MJ·kg-1. After the catalyst recycled 4 times, the catalytic efficiency still kept at 62.8 ± 2.1 %. The results indicated catalytic HTL was a direct and efficient method for biodiesel production from Rhodosporidium toruloides.
ABSTRACT
Plant oil-based epoxy resins are of great interest due to their ecological and economic necessity. Previous studies suggested that the crosslinking density had a considerable influence on the mechanical and thermal properties of plant oil-based epoxy resins. However, so far, the relationship between the crosslinking density and the thermo-mechanical properties of plant oil-based epoxy resins is not clear. To address this issue, model tung oil-based epoxy resins with different crosslinking densities were fabricated to investigate the influence of crosslinking density on the mechanical and thermal properties of tung oil-based epoxy resins. Results show that the tensile strength, Young's modulus, and glass transition temperature are linearly increased with increasing crosslinking density. The elongation at break and tensile toughness show nonlinear downward trends as the crosslinking density increases. The elongation at break decreases gently at first, then dramatically, and finally slowly as the crosslinking density increases. The tensile toughness declines sharply at first and then slowly with increasing crosslinking density. The relationship between the thermostability and the crosslinking density is complex, because the thermostability is determined by both the molecular structure of the curing system and the crosslinking density. These results provide some information for designing plant oil-based epoxy resins according to the requirements of their applications.
ABSTRACT
Diglycidyl ether of bisphenol A (DGEBA) is a kind of widely used epoxy resin, but its thermosets normally show high brittleness and poor impact resistance due to the intrinsic rigid aromatic rings, which limit its application greatly. To avoid this drawback, we proposed a method to prepare a series of hyperbranched epoxies (HBEPs) with different molecular weights. After HBEPs were cured with methyl tetrahydrophthalic anhydride (MTHPA), characterizations were carried out to evaluate the properties of the cured HBEP samples. Testing results indicate that the hyperbranched thermosets can achieve excellent mechanical strength and toughness (tensile strength: 89.2 MPa, bending strength: 129.6 MPa, elongation at break: 6.1%, toughness: 4.5 MJ m-3, and impact strength: 6.7 kJ m-2), which are superior to those of the thermosets of commercial DGEBA (tensile strength: 81.2 MPa, bending strength: 108.2 MPa, elongation at break: 3.0%, toughness: 1.5 MJ m-3, and impact strength: 4.2 kJ m-2). In addition, HBEP with the highest molecular weight and degree of branching shows the best comprehensive mechanical properties. All hyperbranched thermosets exhibit high glass-transition temperatures (T g) and thermostability, which further illustrates the potential application value of HBEPs.
ABSTRACT
A novel hyperbranched ester plasticizer (SOHE) was synthesized from soybean oil. FTIR, 1H NMR, and 13C NMR spectroscopies were used to analyze the chemical structure of SOHE. SOHE was added into poly(vinyl chloride) (PVC). Thermal, mechanical, and dynamic mechanical properties of PVC samples were studied with thermal gravimetric analysis, dynamic mechanical analysis, and tensile tests. The results of SOHE substitution of petroleum-based dioctyl phthalate (DOP) in soft PVC samples were studied. The results indicated that PVC blends mixed with the obtained plasticizer showed higher thermal stability and flexibility. When DOP was completely replaced with SOHE, the T i, T 10, and T 50 of the films were raised to 267.5, 275.3, and 338.0 °C, respectively. The plasticizing mechanism was also investigated. The volatility resistance and extraction were studied, which results indicated that the migration stability of PVC samples was significantly enhanced with the increasing amount of SOHE.
ABSTRACT
In this study, a modifier (CTMA) prepared by emulsion copolymerization of tung oil fatty acid, methyl esters of tung oil fatty acid and acrylonitrile was used to toughen epoxy resins. The structural characterization of the copolymer was carried out by Fourier transform infrared spectroscopy, 1H NMR spectroscopy and high-temperature gel permeation chromatography. Mechanical testing, thermal characterization and scanning electron microscopy were conducted to investigate the properties of epoxy resin modified by the copolymer and further reveal its toughening mechanism. The results indicated that the newly synthesized copolymer effectively toughened the epoxy resin because the elongation-at-break was increased to 89.48%, the maximum toughness calculated by work before break was nearly 4.6 times that of the neat epoxy resin, and apparent shear yields and plastic deformations were observed in the morphology of the fractured surfaces. CTMA, which acts as a flexible cross-linker in the epoxy thermoset, may decrease the cross-linking density.
ABSTRACT
A novel renewable plasticizer based on castor oil, epoxidized glycidyl ester of ricinoleic acetic ester (EGERAE), was synthesized and applied into Poly(vinyl chloride) (PVC) for the first time. Its molecular structure was characterized by FT-IR and ¹H NMR. The effects of replacement of petroleum-based commercial plasticizer dioctyl phthalate (DOP) with EGERAE in poly(vinyl chloride) (PVC) films were researched. Thermal stability, dynamic mechanical property and mechanical properties of PVC films were investigated with thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA) and tensile tests. The results indicated that this castor oil-based plasticizer was able to improve the thermal stability of PVC blends when partially of completely substituting for DOP. Furthermore, EGERAE endowed PVC resin with enhanced flexibility. In addition, the exudation, volatility and extraction resistance characteristics of plasticizers were researched. The degradation mechanism and possible interaction between EGERAE and PVC molecules in the plasticized system were also investigated.
