Diphenolic Acid-Derived Hyperbranched Epoxy Thermosets with High Mechanical Strength and Toughness

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.

Influence of crosslinking density on the mechanical and thermal properties of plant oil-based epoxy resin

“…17 It is well known that the crosslinking density plays an important role in the performance of epoxy resin. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] However, so far there is no systematic study about the effect of the crosslinking density on the properties of plant oil-based epoxy resins. Understanding the relationship between the crosslinking density and the properties of plant oil-based epoxy resins is essential to design plant oil-based epoxy resins.…”

Challenges and Opportunities in the Catalytic Synthesis of Diphenolic Acid and Evaluation of Its Application Potential

“…Both chemical structures of the corresponding glycidyl ether monomers are reported in Figure 5. The research towards the development of new DGEDPA-based materials is mainly aimed at solving some well-known DGEBA performance drawbacks, including high brittleness and poor impact resistance, due to its inherent rigid aromatic rings [65]. DGEDPAbased epoxy thermosets characterized by a hyperbranched structure may enhance mechanical strength and toughness simultaneously [66].…”

“…The obtained DGEDPA was cured with 3,3′-dimethyl-4,4′-diaminodicyclohexylmethane, and the final material exhibited better performance than that of the DGEBA-based one, including higher curing temperature, glass transition temperature, and thermal expansion characteristics [42]. Consequently, the authors claimed that this innovative epoxy resin shows promising potential for vari- The research towards the development of new DGEDPA-based materials is mainly aimed at solving some well-known DGEBA performance drawbacks, including high brittleness and poor impact resistance, due to its inherent rigid aromatic rings [65]. DGEDPAbased epoxy thermosets characterized by a hyperbranched structure may enhance mechanical strength and toughness simultaneously [66].…”

“…The research formed the groundwork for the development of new DGEDPE-based epoxy resins, with the intention to improve polarization and dielectric constants, which are valuable physical properties for such types of applications. Developing a different approach, Xiao et al [ 65 ] synthesized different DPA-based hyperbranched epoxides (HBEPs) from DPA and dibromobutane to improve the mechanical properties of the final resin. A two-step synthetic approach was proposed by the authors ( Figure 6 ).…”

“…This methodology utilizes DPA as the branching component, thus improving the mechanical durability due to its aromatic ring composition and adding a well-tuned flexibility by including dibromo butane. Such hyperbranched thermosets exhibited exceptional mechanical strength and toughness, with much better performances than those of commercial DGEBA thermosets [ 65 , 69 ].…”