Huajun Zhu

The effect of amino-terminated hyperbranched polymers on the impact resistance of epoxy resins

A novel amino-terminated hyperbranched polymer (ATHBP) was synthesized through the end-capping reaction between hyperbranched polymer with hydroxyl group (HBPH) and diethylenetriamine. The chemical structure of ATHBP was characterized by attenuated total internal reflectance infrared spectroscopy (ATR-IR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). The effect of ATHBP content (0–30xa0wt%) on the impact resistance and glass transition temperature (Tg) of diglycidyl ether of bisphenol-A epoxy resin was studied. The toughness mechanism was discussed by observing the fracture surface morphologies of epoxy thermosets using field emission scanning electron microscopy (FESEM). The results showed that the degree of branching of ATHBP was 0.56. And the introduction of ATHBP could favorably improve the impact strength but not sacrifice the Tg of epoxy resin. For example, the impact strength of 25xa0wt% formulation was 60.7xa0% higher than that of the neat epoxy thermoset. FESEM analysis indicated that the toughening mechanism may be attributed to plastic deformation mechanism.

Investigations on mechanical characteristics of glass fiber reinforced epoxy composite modified with amino-terminated hyperbranched polymer

Glass fiber, GF, which was first hydroxylated and silanized, was incorporated into epoxy resin modified with amino-terminated hyperbranched polymer (ATHBP) to obtain high performance composite. The effects of GFs content on the mechanical properties of composites were investigated, discussing the results from flexural, tensile, and impact tests. The composites revealed noticeable improvement in flexural strength, tensile strength as well as impact strength but slow decrease in elongation at break, compared to the epoxy/ATHBP thermoset. FESEM morphology results indicated the good compatibility between epoxy matrix and GF in the appearance of ATHBP and showed that the toughening mechanism was mainly attributed to the stress transfer mechanism.

Impact Resistance Enhancement by Adding Core-Shell Particle to Epoxy Resin Modified with Hyperbranched Polymer

A core-shell particle was fabricated by grafting amino-terminated hyperbranched polymer to the surface of silica nanoparticles. The influences of core-shell particle contents on the tensile and impact strength of the epoxy thermosets modified with amino-terminated hyperbranched polymer were discussed in detail. For comparison, core-shell particle was added into the epoxy/polyamide system for toughness improvement. Results from tensile and impact tests are provided. The introduction of core-shell particle into the epoxy/polyamide systems just slightly enhanced the tensile and impact strength. The incorporation of 3 wt % core-shell particle could substantially improve the tensile and impact strength of epoxy/amino-terminated hyperbranched polymer thermosets. Field emission-scanning electron microscope images of the impact fracture surfaces showed that the excellent impact resistance of epoxy/amino-terminated hyperbranched polymer/core-shell particle thermosets may be attributed to the synergistic effect of shearing deformation and crack pinning/propagation, which is induced by the good compatibility between epoxy matrix and core-shell particle in the presence of amino-terminated hyperbranched polymer.

Evaluation of glass-fiber grafted by epoxide-terminated hyperbranched polymer on the effect of mechanical characterization of epoxy composites

Abstract In this study, glass-fiber, grafted by epoxide-terminated hyperbranched polymer (GF-HBPE), was incorporated into epoxy resins for reinforcement purpose. The effects of GF-HBPE content on mechanical properties of the resulting epoxy-based composites, such as tensile strength, percentage elongation at break, flexural strength, and impact strength, were investigated. The experimental results revealed that GF-HBPE substantially outperformed impact resistance in both tensile and flexural tests. For instance, the tensile strength, percentage elongation at break, flexural strength, and impact strength of the epoxy composite with 1 wt% GF-HBPE increase by about 23.6%, 125%, 26%, and 74.5%, respectively, compared to the unmodified epoxy thermoset.

Synthesis and characterization of hyperbranched polymer with epoxide-terminated group and application as modifier for epoxy/polyamide system

Hyperbranched polymer with epoxide-terminated group was synthesized through end-capping reaction between hyperbranched polymer with hydroxyl-terminated group and epichlorohydrin. The chemical structure of the synthesized polymer was characterized by ATR-IR and 1H NMR spectroscopy. The influence of hyperbranched polymer content on the mechanical properties and fracture toughness of epoxy/polyamide systems was investigated. The toughening mechanism was discussed basing on observing the fracture surface morphologies of epoxy/polyamide/ hyperbranched polymer system.

Synergic improvement of DGEBA/CSP/HBP composite on mechanical behavior

Hyperbranched polymer with amino end groups (HBPA) and core-shell particle (CSP, which is fabricated through grafting HBPA onto the surface of silica nanoparticle) were incorporated into an epoxy matrix to fabricate a high performance composite. The effects of CSPs contents on the mechanical properties of composites were studied, discussing the results from tensile, flexural, and impact tests. The composites revealed noticeable improvements in tensile strength, elongation, flexural strength and impact strength in comparison to the neat epoxy or epoxy/HBPA system. The glass transition temperature (Tg) was also improved by the addition of CSP. Field emission scanning electron micrograph (FESEM) indicated that HBPA could favorable improve the compatibility between CSP and epoxy matrix. And the toughening mechanisms were the synergic effect of shearing deformation, phase separation, crack propagation, crack deflection, and crack pinning.

Mechanical characterization of epoxy composites with glass fibers grafted by hyperbranched polymer with amino terminal groups

Glass fibers grafted by hyperbranched polymer with amino terminal group, GFs-HBPA, were incorporated into an epoxy matrix to prepare a high-performance composite. Mechanical characterization of epoxy-based composites was performed to investigate the effect of GFs-HBPA in the epoxy matrices. The composites revealed significant improvements in flexural strength, elongation at break, and tensile strength, as well as impact resistance in comparison to the neat epoxy. For instance, the flexural strength, elongation at break, tensile strength, and impact strength for composite with 2 wt% GFs-HBPA were increasedxa0by about 17.7, 158, 7.9, and 35.9xa0%, respectively, in relation with the neat epoxy. The reinforcing effect of GFs-HBPA was analyzed on the fracture surface of composites through field emission scanning electron microscopy.