Study on the regulation of ABS molecular structure for enhancing the interlayer bonding strength and properties of FDM products

Interlayer bonding strength (IBS) is the decisive factor governing the performance of fused deposition modeling (FDM) parts. However, limited research has been conducted on regulating the material molecular structure within FDM processes to enhance IBS. In this study, different acrylonitrile butadiene styrene (ABS) specimens for FDM were fabricated by strategically modifying the molecular structure of ABS through emulsion grafting polymerization (to control grafted layer thickness) and seed amplification methodology (to achieve a bimodal particle size distribution). The grafted layer thickness of ABS polybutadiene (PB) phase particles, the compatibility between the two phases, the IBS, and the resulting properties of the FDM parts were investigated. The results demonstrate that increasing the grafted layer thickness of the ABS PB phase particles enhances the compatibility between the phases and increases the fluidity of the ABS melt. Consequently, this improves both the diffusion ability and time for molecular chains during the FDM process, thereby further enhancing IBS. Regulating a bimodal distribution of PB phase particle size further increased ABS melt fluidity, leading to additional IBS improvement. The IBS was directly quantified by T-peel tests, revealing an 110.8 % increase from ABS-1 to ABS-3, with ABS-3 exhibiting a 32.2 % higher peel strength (3.12 N/mm) than a commercial ABS. Following IBS enhancement, the impact strength increased by 60.7 % at 25 °C and by 161.5 % at −30 °C, while the tensile strength increased by 55.6 %. The retention rate of low-temperature impact strength increased by 62.6 %. Furthermore, the dimensional stability of the FDM parts demonstrated significant improvement.