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Abstract Hyperbranched epoxy resins (HERs) is a group of thermoset resins which can be used to improve specifically the toughness and strength of popular diglycidyl ether of bisphenol-A (DGEBA). However, a relationship between the epoxy equivalent weight (EEW) of HERs and the level of property improvement has not been established due to the difficulty to control their EEW. Here we report the synthesis of a series of hyperbranched epoxy resins with different EEW (EHBP-n) through thiol-ene click reaction between thiol-ended hyperbranched polyesters and allylglycidyl ether. The rheological properties of the uncured EHBP-n/DGEBA blends are determined by viscosity and modulus changes, and are directly affected by the EEW of EHBP-n. Moreover, the EEW of EHBP-n also can tune the glass transition temperature and mechanical performances of the cured EHBP-n/DGEBA composites, and these properties first increased and then decreased with a decrease in the EEW of EHBP-n. At 9 wt % of EHBP-6, the improvements on the tensile, flexural, impact and adhesive strengths are 38.9%, 35.3%, 158.6% and 96.2%, respectively, compared with those of cured DGEBA. This result will give a basic guidance for obtaining epoxy resins with various performance. Graphical abstract Image 1 Highlights • Hyperbranched epoxy resins with a controlled epoxy equivalent weight (EHBP-n) were synthesized. • The rheological properties of the uncured EHBP-n/DGEBA blends were also researched. • EHBP-n has an positive effect on mechanical strength on DGEBA. • The paper will give a basic guidance for obtaining epoxy resins with various performance. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hyperbranched epoxy resins with a controlled degree of branching (NPEHP-n) were synthesized. • The particle sizes, rheological properties, mechanical and thermal properties of NPEHP-n/DGEBA were studied. • Excellent flowability and disentangling function of NPEHP-n on DGEBA were reported. • The paper will supply an available route to obtain low viscosity and solvent-free epoxy resins. Abstract Epoxy-ended hyperbranched polymers (EHPs) are increasingly used in toughening and reinforcing diglycidyl ether of bisphenol-A (DGEBA). Synthesis of EHPs with a precise degree of branching (DB) and the effect of DB on the property of EHPs are still a challenge. Here we report the synthesis and properties of nitrogen-phosphor skeleton epoxy-ended hyperbranched polymers (NPEHP-n) with a controlled degree of branching. The particle sizes, rheological properties, mechanical and thermal properties of NPEHP-n/DGEBA composites were studied in detail and compared with those of pure DGEBA. The particle sizes, viscosities, storage modulus and loss modulus of NPEHP-n/DGEBA blends decrease with an increase in DB and content of NPEHP-n, indicating excellent flowability of NPEHP-n with high DB and disentangled function of NPEHP-n. The mechanical performances of the cured NPEHP-n/DGEBA composites increase distinctly with the increase of the DBs and content of NPEHP-n, including the tensile, flexural and impact strength, showing a maximum value at about 9 wt% of NPEHP-n. The improvements on the tensile, flexural, and impact strengths are 31.7–42.8%, 56.4–76.4%, and 172.0–198.3%, respectively. The results will supply available route for disentangling DGEBA chain to obtain low viscosity epoxy resins and solvent-free coatings. [ABSTRACT FROM AUTHOR]

Hyperbranched epoxy resins are excellent materials for toughening and reinforcing diglycidyl ether of bisphenol‐A (DGEBA), but the glass transition temperature usually decrease sharply. Here we report synthesis of novel epoxy‐ended hyperbranched polyesters (HEHP‐n, n = 1, 2, 3, and 4) with different molecular weights. Chemical structure of the HEHP‐n and intermediates were characterized by FT‐IR and 1H NMR. The HEHP‐n has shown remarkable effect for toughening and reinforcing DGEBA. The mechanical strength of the HEHP‐n/DGEBA composites first increased and then decreased as the molecular weight and content of HEHP‐n increased. When the composites contain 12 wt% HEHP‐3, the impact, flexural and tensile strengths of the cured HEHP‐n/DGEBA composites reached 48.0 kJ/m2, 41.2 MPa, and 74.8 MPa, respectively, which are 223.6%, 73.0%, and 46.1% higher than those of the cured DGEBA. The glass transition temperature of the cured HEHP‐n/DGEBA also increased in comparison with that of the epoxy‐ended hyperbranched polyesters/DGEBA composites reported previously. POLYM. COMPOS., 39:E2046–E2055, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Owing to the outstanding mechanical performance, diglycidyl ether of bisphenol A (DGEBA) becomes an important thermoset resin, but its brittleness and difficulties in degradation and recycling retard sustainable development. Herein, we have prepared several hyperbranched epoxy resins containing 1,3,5-hexahydro-s-triazine (HER-HT n , n = 3, 6, 12, 24) which showed versatility on modifying DGEBA, including simultaneous reinforcing and toughening function, rapid degradation and recycling, and good compatibility. The detailed results showed that the HER-HT 12 could increase the flexural, impact and tensile strengths of cured DGEBA by 132.7%, 190.4%, and 57.7%, respectively, and also increase degradation degree from 37.2 wt% to 99.9 wt%. The mechanical performance of the cured HER-HT n /DGEBA reinforced in the beginning and then decreased with an increase in the content and the molecular weight of HER-HT n , however, their degradation degrees increased distinctly. The reinforcing and toughening mechanism and degradation mechanism of the composites were investigated by SEM micrographs and GC-MS spectra. HER-HTn showed versatility in modifying DGEBA, including simultaneous reinforcing and toughening function and improving degradation. Image 1 • HER-HTn showed versatility in modifying DGEBA. • HER-HTn could improve distinctly the tensile, flexural, impact strengths of the DGEBA. • HER-HTn could promote remarkably the degradation ability of the cured HER-HT 12 /DGEBA composites. • The reinforcing and toughening mechanism and degradation mechanism of the composites were investigated. [ABSTRACT FROM AUTHOR]