Zizhao Qian,Yanglei Zheng,Qing Li,Lujie Wang,Feiya Fu,Xiangdong Liu
Diphenolic acid (DPA) is a renewable chemical attracting great interest in biobased polymer science. Despite their low toxicity and high recyclability, the undesirable decarboxylation of DPA-based polymers generally leads to poor thermal stability and material failure restricting their practical applications. Here, we demonstrate that the incorporation of amide groups into a benzoxazine molecule can effectively avoid this problem while improving the thermally mechanical performance of the polybenzoxazine resin. We first synthesized a tetra-phenolic compound via a condensation reaction of DPA with hexanediamine through an ammonium salt route and then prepared a tetrafunctional benzoxazine, denominating as DHDA-fa, by a further reaction with furfurylamine and formaldehyde in a polyethylene glycol 200 (PEG-200) medium. The glass transition temperature (Tg) and decomposition temperature (Td5) of the resulting poly(DHDA-fa) were found to be 326 and 384 °C by DMA and TGA, respectively, which outperformed many biobased benzoxazine resins previously reported. Experimental results revealed that the enhanced hydrogen bonding and doubled oxazine functionary are the important contributors for the improved thermal and mechanical performances. This work confirmed a novel way to perfect DPA-based benzoxazine resins resulting in an effective strategy for developing biobased materials with high performance for practical applications.
In this study, a novel bio-based benzoxazine-terminated hyperbranched polyester (HB-Dfa) was designed and synthesized using renewable diphenolic acid and furfurylamine as raw materials through self-polymerization and Mannich condensation reaction . Meanwhile, the copolymers based on HB-Dfa and benzoxazine monomer (P-ddm) were prepared to investigate the effect of HB-Dfa on the properties of traditional benzoxazine. The chemical structure of HB-Dfa was elucidated by fourier transform infrared (FTIR) and nuclear magnetic resonance ( 1 H NMR) spectroscopies. The curing behavior and curing kinetics were investigated by differential scanning calorimetry (DSC), showing that it possessed a low temperature of exothermic peak and activation energy value compared with the P-ddm. Hence, the curing process of P-ddm was facilitated by the introduction of HB-Dfa. The thermomechanical and thermal properties of P-ddm/HB-Dfa copolymers were determined by dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA), respectively. Compared with the pure P-ddm resin, the introduction of HB-Dfa remained most of glass transition temperature ( T g ), cross-linking density and thermal stability, which could promote the curing reaction and reduce the curing temperature of the copolymers . In addition, HB-Dfa exhibited a low dielectric constant (2.46 ≥ k ≥ 2.16) and a low dielectric loss ( f ≤ 0.05) at frequencies range of 2–18 GHz, which could effectively modify the dielectric properties of the copolymer system.
Diphenolic acid epoxy resin (DPAE), a new type of bio-based epoxy, exhibits many attractive performances, such as high reactivity, low expansion coefficient (CTE), high glass transition temperature ( T g ) and high storage modulus . However, the dielectric constant of DPAE is not satisfied for the requirements of high frequency circuit field, which need to be further improved to expand its application in emerging area of electronic information. In this work, both dicyclopentadiene phenol epoxy resin (DPR) and cyanate ester (CE) were used to modify DPAE in order to improve its dielectric property , while keeping good heat resistance and low dimensional stability. Furthermore, the influence of curing agent types on properties of DPAE/DPR system was studied. Compared with DPAE resin, both DPAE/DPR and DPAE/CE composites exhibited higher glass transition temperature ( T g ), lower dielectric constant, lower loss tangent with good compatibility between DPAE and those two resins. Moreover, CE resin exhibited better modified effect than DPR on thermal and dielectric properties of DPAE with the same addition. For example, the dielectric constant and loss tangent of DPAE/CE with 50 wt% CE were as low as 3.4 and 0.018 at 1 MHz, respectively.
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