Simultaneous reinforcement and toughness improvement of an epoxy–phenolic network with a hyperbranched polysiloxane modifier

Issazadeh

Zhang

et al. 2020

Macro Materials & Eng

The synthesis of inherently ductile epoxy network as measured by their resistance to deformation however is less reported and is the subject of this study. Common strategies have been to incorporate structures that are inherently rigid, [8] such as liquid crystalline [9,10] or highly aromatic, [11,12] while others have sought to build a combination of both rigid and flexible features into a network. [13][14][15] Highly aromatic structures will generally have excellent mechanical and thermal properties and resistance to solvent ingress, but are also notoriously difficult to process. As a result, the following studies are a reflection of the variety of strategies attempting to break this paradigm. Karimata et al. (2016) [16] synthesized a tri-aryl di-epoxide monomer linked by flexible carbosilane segments. After curing with an aromatic amine, the glass transition temperature (T g ) of the network was still below room temperature, suggesting potential application as a reactive flexibilizer. Wan et al. (2016) [17] synthesized a bioderived eugenol epoxy resin, essentially a tri-aryl ether linked epoxy resin with a superior modulus, hardness, and char yield compared with a related epoxy amine cured network. It also had a higher creep displacement attributed to increased chain mobility in the glassy state. Yu et al. (2018) [18] combined a rigid carboxamide structure with flexible aliphatic ethers to synthesize an amine, which when cured with an epoxy resin reported improvements in tensile strength, failure strain, and impact strength without any commensurate deterioration in flexural strength. Varley et al. (2019) synthesized highly aromatic ether-linked epoxy monomers and amines, exploring the impact of substitution patterns on the properties and processability. [19] Improvements in yield and failure strain, referred to as distortional behavior, were attributed to an increase in energy dissipated through phenylene rotations available to para-substituted amine or epoxy resins. [20,21] In this work, two tri-aryl epoxy resins containing flexible methylene linkages instead of ether linkages and a rigid bi-aryl epoxy resin have been synthesized and compared with the commercially available diglycidyl ether of bis phenol F (BisF). A central hypothesis of this work is that flexibility or molecular mobility within a rigid network may impart enhanced distortional behavior of the epoxy amine network as measured by compression. The epoxy resins synthesized were bis[(glycidyloxy)phenyl)]-m-xylene (BGOPmX), bis[(glycidyloxy)phenyl)]-p-xylene (BGOPpX), and In this work, two tri-aryl and one bi-aryl epoxy resin, bis[(glycidyloxy)phenyl)]m-xylene (BGOPmX), bis[(glycidyloxy)phenyl)]-p-xylene (BGOPpX), and bis(glycidyloxy) biphenyl (BGOBP) are synthesized and cured with methylene dianiline and 4,4′-diamino diphenyl sulfone. Structure, property, and processing relationships are investigated and compared against diglycidyl ether of bis-phenol F epoxy resin to better understand the impact of rigid and flexible subunits within the network st...

Section: Resultsmentioning

confidence: 96%

Section: Resultsmentioning

confidence: 99%

Synthesis of Tri‐Aryl Methane Epoxy Resin Isomers and Their Cure with Aromatic Amines

Issazadeh

Zhang

et al. 2020

Macro Materials & Eng

Section: Resultsmentioning

confidence: 99%

“…These can be produced by an increased propensity for higher levels of side reactions such as internal cyclisation or etherification during the diffusion controlled regime of cure for the TGAPB networks. [15,22] Furthermore, symmetrical epoxies, those with an allpara backbone have an axis of rotation for each aryl ring which allows them to undergo aromatic ring flips at elevated temperature or during stress under load, unlike asymmetric epoxy resins. The availability of these additional molecular motions increases the distribution of molecular conformations across different length scales resulting in broader but less intense peaks in the tan δ thermogram as is observed here.…”

Section: Glass Transitionmentioning

confidence: 99%

Synthesis of tri‐aryl ether epoxy resin isomers and their cure with diamino diphenyl sulphone

Journal of Polymer Science

Zhang

Dao

et al. 2020

The synthesis of bi-and tetra-functional tri-aryl ether epoxy resin isomers and their subsequent cure with 44 diamino diphenyl sulphone (DDS) is presented here. The effect of varying aromatic substitution and cross-link density on the structure, property, and processing relationships is explored for 1,3 bis (3-glycidyloxyphenoxy)benzene (133 BGOPB), 1,4 bis(4-glycidyloxyphenoxy) benzene (144 BGOPB), N,N,N,N-tetraglycidyl 1,3-bis (3-aminophenoxy) benzene (133 TGAPB), and N,N,N,N-tetraglycidyl 1,4-bis (4-aminophenoxy) benzene (144 TGAPB). Meta substitution to the aromatic ring reduces the rate of reaction, glass transition temperature, yield strain and crosslink density, coefficient of thermal expansion, and side reactions, while increasing strain softening, compressive modulus and strength, and methyl ethyl ketone ingress. Increasing crosslink density increases the glass transition temperature, promotes side reactions during cure, and increases compressive modulus, strength, and yield strain, while reducing coefficients of thermal expansion, methyl ethyl ketone ingress, and density. The results are discussed in terms of packing efficiency of the meta-substituted epoxy resins and the role of short range molecular mobility caused by the lack of an aromatic axis of rotation. K E Y W O R D Sisomerism, network properties, reaction kinetics, synthesis

“…Despite being primarily controlled by crosslink density or the chemical structure of the network, additive approaches to improving toughness are common, including ductile and rigid inclusions, interlayers, and nanoadditives to name a few. The primary goal of all these strategies, however, remains the enhancement of toughness or distortional behavior, without compromising other desirable properties such as modulus, strength, or processability …”

Section: Introductionmentioning

confidence: 99%

Synthesis of tri‐aryl ketone amine isomers and their cure with epoxy resins

Polymers for Advanced Techs

Dao

Vogel

et al. 2019

Isomeric tri‐aryl ketone amines, 1,3‐bis(3‐aminobenzoyl)benzene (133 BABB), 1,3‐bis(4‐aminobenzoyl)benzene (134 BABB), and 1,4‐bis(4‐aminobenzoyl)benzene (144 BABB) are synthesized and cured with diglycidyl ether of bisphenol A and diglycidyl ether of bisphenol F in this work. Differential scanning calorimetry and near‐infrared spectroscopy reveal higher rate constants and enhanced secondary amine conversion with increasing para substitution attributed to resonance effects and the electron withdrawing nature of the carbonyl linkages. Glass transition temperatures increase from 133 BABB to 134 BABB, but decrease modestly for the 144 BABB hardener. With increasing para substitution, the flexural modulus and strength both decrease while the strain to failure increases but all BABB amines displaying higher mechanical properties than the corresponding 4,4‐diaminodiphenyl sulfone (44 DDS) networks. The thermal stability of the BABB networks is found to be modestly lower than 44 DDS, but char yields are significantly higher. Changes in thermal and mechanical properties are described in terms of molecular structure and equilibrium packing density.