Polybenzoxazine/carbon nanotube nanocomposites as a polymeric sensing material for volatile organic compounds

The emissions of volatile organic compounds (VOCs) have hazardous effects on humans and the environment, and hence they should be detected and reduced. In this study, polybenzoxazine (PBZ) and amine-functionalized multiwall carbon nanotube (MWCNT) composites were synthesized as a sensor for VOCs. MWCNT were functionalized with two types of diamines, namely, 1,6-hexanediamine (HDA) and phenylenediamine (PDA). HDA or PDA treated MWCNTs were loaded into the benzoxazine matrix with different weight percentages (0.1, 0.3, 0.5, and 1%). FTIR analysis confirmed the chemical attachment of the two types of diamines on MWCNT. XRD diffraction and scanning electron microscopy (SEM) were used to investigate the nanofillers morphology and clarify the differences between pristine and amine-functionalized MWCNT. Thermal gravimetric analysis (TGA) was used to study the composites’ thermal stability and degradation behavior. It was found that, in contrast to neat PBZ, the major degradation temperature of PBZ/0.5%MWCNT-PDA nanocomposites were enhanced by 10%. The electrical conductivity of PBZ was 6.32 × 10–9, which was enhanced to 6.11 × 10–7 in the composites with 1% MWCNT-PDA. This material was tested as a VOCs sensor for methanol, acetone, and toluene and showed that PBZ/1% MWCNT-PDA composite responded to all the vapors.

Recent Progress of High Performance Thermosets Based on Norbornene Functional Benzoxazine Resins

With the growing demand for high performance polymeric materials in industry, several types of thermosets such as bismaleimides, advanced epoxy resins, cyanate esters, and phenolic resins have been widely investigated to improve the performance of thermosetting products. Among them, benzoxazine resins have received wide attention due to their extraordinarily rich molecular design flexibility, which can customize our needs and adapt increasing requirements. To further improve the properties of polybenzoxiazines, researchers have found that the introduction of a norbornene functional group into the benzoxazine moiety can effectively improve the comprehensive performance of polybenzoxazine thermosets. This article focused on reviewing the recent development of high-performance thermosets based on norbornene functional benzoxazine thermosetting resins.

Review on the Accelerated and Low-Temperature Polymerization of Benzoxazine Resins: Addition Polymerizable Sustainable Polymers

Due to their outstanding and versatile properties, polybenzoxazines have quickly occupied a great niche of applications. Developing the ability to polymerize benzoxazine resin at lower temperatures than the current capability is essential in taking advantage of these exceptional properties and remains to be most challenging subject in the field. The current review is classified into several parts to achieve this goal. In this review, fundamentals on the synthesis and evolution of structure, which led to classification of PBz in different generations, are discussed. Classifications of PBzs are defined depending on building block as well as how structure is evolved and property obtained. Progress on the utility of biobased feedstocks from various bio-/waste-mass is also discussed and compared, wherever possible. The second part of review discusses the probable polymerization mechanism proposed for the ring-opening reactions. This is complementary to the third section, where the effect of catalysts/initiators has on triggering polymerization at low temperature is discussed extensively. The role of additional functionalities in influencing the temperature of polymerization is also discussed. There has been a shift in paradigm beyond the lowering of ring-opening polymerization (ROP) temperature and other areas of interest, such as adaptation of molecular functionality with simultaneous improvement of properties.

Effect of acetylacetone metal salts on curing mechanism and thermal stability of polybenzoxazine

To overcome high water absorption of inorganic metal salts and their poor compatibility with resin, acetylacetone metal salts (M(acac) n) were selected as the catalysts of benzoxazine resin. Their effects on the catalytic activity, structure, and thermal stability of polybenzoxazine had been estimated by dynamic differential scanning calorimetry, in situ Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analyzer. The results revealed that M(acac) n of iron (Fe3+), cobalt (Co3+ and Co2+), and copper (Cu2+) exhibited high catalytic activity and reduced evidently activation energy, especially acetylacetone iron salt. The addition of M(acac) n was beneficial to the formation of Ph–N–Ph structure, which was easy to form a denser carbon layer during thermal degradation, prevented heat transfer and further decomposition of the resin, and finally led to the increase of carbon residue at high temperature.

Synthesis and characterization of siloxane-containing benzoxazines with high thermal stability

To understand the influence of phenyl substituents on silicon and to improve the glass transition temperature ( T g) and thermal stability, phenol/bis ( p-aminophenoxyl) dimethylsiloxane-based benzoxazine (P-adms), phenol/bis ( p-aminophenoxyl) methylphenylsiloxane-based benzoxazine (P-amps), and phenol/bis ( p-aminophenoxyl) diphenylsiloxane-based benzoxazine (P-adps) were designed and synthesized. The structure of the siloxane-containing benzoxazines were confirmed by proton and carbon nuclear magnetic resonance imaging and Fourier transform infrared spectra. The curing reaction of the obtained benzoxazines was studied by differential scanning calorimetry (DSC) and in situ infrared spectra. The influence of the aromatic content on the T g and thermal stability were investigated by modulated DSC and thermogravimetric analysis. Compared to aminopropylsiloxane-based benzoxazines, the bis ( p-aminophenoxyl) siloxane-based benzoxazines possessed relatively higher T g about 140°C due to the replacement of flexible propyl chain by phenoxyl chain. With increasing phenyl substituents on silicon, the polybenzoxazines possessed lower T g and higher thermal stability. It is notedthat the phenol/bis ( p-aminophenoxyl) diphenylsiloxane-based benzoxazine (P-adps) still has low viscosity despite high aromatic content due to the flexible ether linkage (Ar–O–Si).