Effect of rubber reactivity on the morphology of polybenzoxazine blends investigated by atomic force microscopy and dynamic mechanical analysis

Synthesis of Novel Benzoxazines Containing Sulfur and Their Application in Rubber Compounds

This work reports the synthesis and successful use of novel benzoxazines as reinforcing resins in polyisoprene rubber compounds. For this purpose, three new dibenzoxazines containing one (4DTP-fa) or two heteroatoms of sulfur (3DPDS-fa and 4DPDS-fa) were synthesized following a Mannich condensation reaction. The structural features of each benzoxazine precursor were characterized by 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) and Raman. The new precursors showed well suited reactivity as characterized by differential scanning calorimetry (DSC) and rheology and were incorporated in rubber compounds. After the mixing, the curing profiles, morphologies and mechanical properties of the materials were tested. These results show that the structural feature of each isomer was significantly affecting its behavior during the curing of the rubber compounds. Among the tested benzoxazines, 3DPDS-fa exhibited the best ability to reinforce the rubber compound even compared to common phenolic resin. These results prove the feasibility to reinforce rubber compounds with benzoxazine resins as a possible alternative to replace conventional phenolic resins. This paper provides the first guide to use benzoxazines as reinforcing resins for rubber applications, based on their curing kinetics.

Epoxy/methyl methacrylate acrylonitrile butadiene styrene (MABS) copolymer blends: reaction-induced viscoelastic phase separation, morphology development and mechanical properties

Epoxy/MABS blends undergo viscoelastic phase separation during curing due to the dynamic asymmetry of the phases and a significant improvement in the mechanical properties of the system is observed.

Toughening effect and mechanism of polyamide 12 and modified montmorillonite in polybenzoxazine resin

The mechanical properties of polybenzoxazine (PBa) resins were improved by adding polyamide 12 (PA12) and modified montmorillonite (OMMT) as additives. The mechanical properties and thermal stability of PBa and resulting PBa composites were investigated using an Instron universal material testing instrument and dynamic mechanical analysis. The morphologies of the fracture surfaces were characterized by scanning electron microscopy. The results of morphological studies showed that PBa/PA12/OMMT composites exhibit significantly improved mechanical properties and thermal stability compared with that of the pristine PBa. When the OMMT content increased to 1 wt%, the fracture toughness (1.36 MPa·m1/2) and the fracture energy (G IC, 315.76 J·m−2) of PBa/PA12/OMMT-1 composites increased by 67.9% and 181.4%, respectively, compared with those of the pristine PBa. The thermal stability properties demonstrated that the storage modulus and glass transition temperature (T g) of PBa/PA12/OMMT composites gradually increased with the addition of OMMT particles. The scanning electron microscopy results indicated that PBa/PA12/OMMT composites possess a toughening mechanism of crack deflection, with a large bulk of voids and debonding induced by PA12 and OMMT clay particles. Moreover, the OMMT might provide microvoid nucleating sites at its surface to release constrains for shear yielding.

Modification of benzoxazine with aryl-ether-ether-ketone diphenol: preparation and characterization

A modified benzoxazine resin system with “high strength, high modulus and high toughness” was prepared by introducing an efficient modifier (m-DHPBP) with high catalytic activity and an aryl-ether-ether-ketone (PEEK) structure.

Copolymers of vinyl-containing benzoxazine with vinyl monomers as precursors for high performance thermosets

A benzoxazine containing a vinyl group (P-4va) was prepared by the reaction of phenol, 4-vinylaniline, and paraformaldehyde. A differential scanning calorimetry (DSC) study revealed that ring-opening polymerization of the benzoxazine and chain polymerization of the vinyl group occurred in the same temperature range. When 2,2'-azobisisobutyronitrile was added as a radical initiator to P-4va, however, only the vinyl groups were polymerized at lower temperature, giving oligo(P-4va) that contains pendent benzoxazine units. Radical copolymerization of P-4va with various vinyl monomers such as styrene, methyl methacrylate (MMA), and n-butyl acrylate (BuA) was examined. The chemical structure of the copolymers was confirmed by FT-IR and ¹H-NMR to be one of polyolefins bearing benzoxazine units as the pendant groups. The weight-average molecular weights of the copolymers determined by size exclusion chromatography were to be in the range of 1900–51,500 depending on the comonomers. DSC of the copolymers showed that the maxima of the exothermic peaks corresponding to the ring-opening polymerization of the pendent benzoxazine units were observed in the temperature range of 229–250 °C. Thermal cure up to 240 °C of the copolymer films afforded homogenous transparent films with improved thermal properties. Tough cured film was obtained by the copolymerization with MMA, while a tough and flexible film was obtained by the copolymerization with BuA.