Insights into the synergistic mechanism of reactive aliphatic soft chains and nano‐silica on toughening epoxy resins with improved mechanical properties and low viscosity

Abstract

Toughening epoxy resin (EP) without sacrificing strength, modulus, and processing performance is always a harsh task. Here, a series of epoxy systems containing soft butyl glycidyl ether (BGE) and rigid nano‐silica (nano‐SiO2) were prepared. Micro‐phase separation structures derived from the self‐assembly effect of BGE can be observed in atomic force microscopy images by controlling the total amount of BGE and nano‐SiO2 at 2 wt% for the EPC:Si‐m:n (m + n = 4) systems. Due to the synergistic effect of self‐assembly effect of BGE and the rigid effect of well dispersed nano‐SiO2, EPC:Si‐2:2 system exhibited improvement of tensile strength of 59.3% (92.63 MPa), tensile modulus of 24.8% (3.52 GPa), elongation at break of 78.6% (4.84%), and glass transition temperature of 2.4% (138.4°C) compared with Pure EP system. Besides, due to the low loading of nano‐SiO2 (≤2 wt%) and the dilution effect of BGE, the viscosity of all the toughening systems is lower than 600 mPa·s, which can provide this toughening system with superior processing performance for large production of composites by automotive manufacturing methods such as vacuum assistant resin infusion technology.

Directly Using Paraffin as the Toughening Agent of Epoxy Composites: An Experimental and Molecular Dynamics Simulation Study

“…As expected, the tensile modulus and storage modulus at 25 °C show the identical variation trend and reach their highest values in the EP DA‑2.5 system. However, because the storage modulus of the EP DA‑5 sample is lower than that of the pure EP sample when the temperature is higher than 63 °C, the T g of the EP DA‑2.5 system is lower than that of the pure EP system because T g is also related to the rigidity of the materials . The opposite discipline of the storage modulus at 25 °C and T g for the EP DA‑2.5 and pure EP systems will be further discussed in the latter part of this article.…”

“…However, because the storage modulus of the EP DA-5 sample is lower than that of the pure EP sample when the temperature is higher than 63 °C, the T g of the EP DA-2.5 system is lower than that of the pure EP system because T g is also related to the rigidity of the materials. 36 The opposite discipline of the storage modulus at 25 °C and T g for the EP DA-2.5 and pure EP systems will be further discussed in the latter part of this article. In spite of this, the impact and tensile results can exhibit striking conclusions that the impact strength, elongation at break, strength, and modulus are simultaneously enhanced in the EP DA-2.5 system, while the EP DA-5 system possesses the highest tensile strength of 102.7 MPa, higher elongation at break of 5.2%, and the highest impact strength of 24.3 kJ/m 2 .…”

“…T g , which is an important parameter for the epoxy composites, can be characterized by the DSC and DMA measurements . Usually, the peak temperature of tan δ is determined as the T g of the materials in the DMA test . As for the DSC analysis, T g is at the temperature where the slope of the DSC curve reaches its maximum value.…”

“…35 Usually, the peak temperature of tan δ is determined as the T g of the materials in the DMA test. 36 As for the DSC analysis, T g is at the temperature where the slope of the DSC curve reaches its maximum value. In Table 1, the T g values of all the samples tested by DSC and DMA were listed.…”

Toughening shape-memory epoxy resins via sacrificial hydrogen bonds

“…[2][3][4] Generally, highly cross-linked epoxies exhibit superior performance, such as high modulus, strength and thermal resistance; however, high cross-linking also has the adverse consequences of fragility and poor resistance to crack propagation, and these materials are thus prone to permanent damage caused by irreversible covalent bond breakage of the network. 5 Over the past few decades, substantial efforts have been committed to toughening epoxy resins, including the incorporation of elastomers 6 or thermoplastics, 7 the interpenetration of multiple networks, [8][9][10] the addition of nanofillers [11][12][13] and dynamic covalent chemistry. 14 Although the traditional approaches for toughening an epoxy can improve its extensibility dramatically, the existence of a soft component inevitably leads to a sacrifice in strength in most cases.…”