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<p>Borocarbonitride (BCN) nanosheets were incorporated into poly(methyl methacrylate)/styrene–acrylonitrile copolymer (PMMA/SAN) blends to investigate how a two-dimensional, defect-rich nanofiller alters the interfacial structure. The resulting effects on the blend’s rheological, mechanical, fracture, and thermal behavior were then evaluated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman analysis confirmed that the synthesized BCN consists of thin, flexible, turbostratic nanosheets with short-range order and mixed B–N, B–C, and C–N bonding. This makes them suitable for interfacial reinforcement. Steady-shear rheology showed that neat PMMA/SAN blend and its nanocomposites exhibited shear-thinning behavior. The addition of BCN in PMMA/SAN blend showed a non-monotonic response in viscosity, shear stress, and first normal stress difference. Cross-model analysis suggests that the neat PMMA/SAN blend had a strong low-shear structure, whereas the 0.5 wt% BCN reinforced nanocomposites showed the most effective interfacial stabilization among the filled systems. At higher BCN loadings, the decrease in zero-shear viscosity and the irregular high shear response suggested partial agglomeration, reduced interfacial efficiency, and easier shear induced nanofiller orientation. Tensile results revealed that 0.5 wt% BCN reinforcement showed the highest strength ~ 14.0&#xa0;N/mm<sup>2</sup> and modulus ~ 2.57 GPa, whereas the neat blend retained the highest ductility and toughness. With increasing BCN nanosheet concentration, strain at break decreased from about 3.4% for neat PMMA/SAN to about 1.5–1.7% at 1.5–2 wt% BCN, and toughness decreased from about 0.41 to 0.14–0.17 MJ/m<sup>3</sup>. Modified Halpin–Tsai analysis further showed that the effective reinforcement efficiency was highest at 0.5 wt% BCN and decreased strongly at higher loading. Fractography revealed a transition from fibrillated, ductile fracture in neat PMMA/SAN to more terrace-like and localized fracture in BCN-filled blends. Overall, the results show that the performance of PMMA/SAN/BCN nanocomposites is governed by the balance between interfacial reinforcement at low BCN loading and aggregation-induced instability at higher loading, with 0.5 wt% BCN identified as the optimum composition.</p>

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Effect of borocarbonitride nanosheet loading on the rheological, mechanical, fracture, and thermal behavior of PMMA/SAN blends

  • 期刊论文

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  • 发表日期：

    2026年7月21日

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  • Kampa Bala Koteswara Rao,
  • Pankaj Tambe

摘要

Borocarbonitride (BCN) nanosheets were incorporated into poly(methyl methacrylate)/styrene–acrylonitrile copolymer (PMMA/SAN) blends to investigate how a two-dimensional, defect-rich nanofiller alters the interfacial structure. The resulting effects on the blend’s rheological, mechanical, fracture, and thermal behavior were then evaluated. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and Raman analysis confirmed that the synthesized BCN consists of thin, flexible, turbostratic nanosheets with short-range order and mixed B–N, B–C, and C–N bonding. This makes them suitable for interfacial reinforcement. Steady-shear rheology showed that neat PMMA/SAN blend and its nanocomposites exhibited shear-thinning behavior. The addition of BCN in PMMA/SAN blend showed a non-monotonic response in viscosity, shear stress, and first normal stress difference. Cross-model analysis suggests that the neat PMMA/SAN blend had a strong low-shear structure, whereas the 0.5 wt% BCN reinforced nanocomposites showed the most effective interfacial stabilization among the filled systems. At higher BCN loadings, the decrease in zero-shear viscosity and the irregular high shear response suggested partial agglomeration, reduced interfacial efficiency, and easier shear induced nanofiller orientation. Tensile results revealed that 0.5 wt% BCN reinforcement showed the highest strength ~ 14.0 N/mm2 and modulus ~ 2.57 GPa, whereas the neat blend retained the highest ductility and toughness. With increasing BCN nanosheet concentration, strain at break decreased from about 3.4% for neat PMMA/SAN to about 1.5–1.7% at 1.5–2 wt% BCN, and toughness decreased from about 0.41 to 0.14–0.17 MJ/m3. Modified Halpin–Tsai analysis further showed that the effective reinforcement efficiency was highest at 0.5 wt% BCN and decreased strongly at higher loading. Fractography revealed a transition from fibrillated, ductile fracture in neat PMMA/SAN to more terrace-like and localized fracture in BCN-filled blends. Overall, the results show that the performance of PMMA/SAN/BCN nanocomposites is governed by the balance between interfacial reinforcement at low BCN loading and aggregation-induced instability at higher loading, with 0.5 wt% BCN identified as the optimum composition.