Jie Zhang

Fused Filament Fabrication (FFF) offers a promising route for fabricating thermally conductive polymer composites, but high filler loadings often impair mechanical performance and processability. Here, an immiscible PP/PA6/BN ternary system was developed by integrating selective filler localization with FFF-induced domain alignment. Because of the stronger affinity between BN and PA6, BN platelets preferentially enriched in PA/BN-rich domains rather than dispersing randomly in the PP matrix. During FFF deposition, these domains were elongated and partially interconnected along the main raster direction, forming anisotropic thermal-transport pathways. Compared with compression-molded PP/PA/BN and binary PP/BN, the printed PP/PA/BN composite showed enhanced directional thermal conductivity while retaining mechanical integrity and printability. Morphological, WAXD/XRD, and rheological analyses indicate that thermal transport arises from BN orientation, PA/BN-rich domain interconnection, and multiphase interfacial effects. This work provides a morphology-regulation strategy for printable thermally conductive composites.

Foam materials are widely used in packaging, construction, and aerospace, but their poor degradability raises serious environmental concerns. This work proposes an upcycling strategy that combines fused filament fabrication (FFF) with in situ fibrillation to convert waste low-density polyethylene (LDPE) foam to high-performance microfibrillar composites. A mini corotating twin-screw extruder was developed to melt-blend waste LDPE foam with polystyrene and directly produce printable filaments while removing entrapped gas from the porous foam. During subsequent FFF printing, shear and extensional fields promoted the formation of oriented polystyrene microfibrils and induced oriented crystallization in the LDPE matrix. The foam-derived printed samples achieved a tensile strength of 23.01 MPa, comparable to that of virgin-material counterparts. This study provides a practical route for the high-value recycling of waste LDPE foam.

With the increasing demand for functional polymers, the application scope of high-filled polymers has become increasingly extensive However, high filling often leads to difficulties in their processing. Traditional methods to improve processing conditions always have negative effects on the material properties. Considering that disentanglement can effectively reduce the viscosity of polymer materials, it is highly possible to solve this problem by preparing high-filled composites with low entanglement density. In this work, a series of high-density polyethylene (HDPE) / boron nitride (BN) composites were prepared, and the effect of filler size and content are studied. After using a parallel-plate rotational rheometer to reduce the entanglement density, the rheological properties, crystallization behavior and entanglement recovery rate were studied. The results show that the molecular chain movement ability of the composite is greatly improved, the viscosity is reduced by about 90%, the crystallinity and crystallization temperature are improved. Due to the existence of filler, the entanglement recovery process is limited, and the entanglement recovery rate of T500 sample is only 12% at 1000s. Therefore, we provide a promising method to prepare high-filled composites with low viscosity and slow recovery, which is of great research and practical significance for polymer science.