To develop fully biodegradable and reinforced poly(lactic acid) (PLA) melt-blown nonwovens (MBs) for separation and filtration, PLA/aminated halloysite nanotubes (PLA/A-HNTs) MBs were prepared using PLA/A-HNTs master-batches, compatibilized by dual-monomer glycidyl methacrylate-styrene (St-co-GMA) melt-grafted PLA (PLA-g-(St-co-GMA)). The morphology, crystallization, pore size distribution, filtration performance, and mechanical properties of PLA/PLA-g-(St-co-GMA)/A-HNTs MBs were characterized. The results indicated that PLA/PLA-g-(St-co-GMA)/A-HNT MBs could be successfully manufactured, with well dispersed A-HNTs in PLA MB fibers due to improved compatibility by PLA-g-(St-co-GMA). Incorporation of A-HNTs and PLA-g-(St-co-GMA) slightly increased the average diameter and pore size of PLA MBs. A-HNTs increased the crystallinity degree of PLA MBs, while the crystal forms remained unchanged. In comparison with PLA MBs, the tensile strengths of PLA/PLA-g-(St-co-GMA)/A-HNTs MBs were enhanced but the elongation decreased. PLA/PLA-g-(St-co-GMA)/A-HNT MBs could obtain higher filtration efficiency than neat PLA MBs.

With increasing demands on the high-performance and environmental-friendly melt-blown nonwovens (MBs) for separation and filtration, herein, we reported a poly(lactic acid)/polyamide 11 (PLA/PA11) 100% bio-based MBs in situ compatibilized by dual-monomer glycidyl methacrylate–styrene melt-grafted poly(lactic acid) (PLA-g-(St-co-GMA)). The morphology, crystallization, thermal and rheological behaviors of reactive extruded PLA/PA11/PLA-g-(St-co-GMA) melt blends were investigated, and the structure and filtration performance of corresponding MBs were fully characterized. The results indicated that the interface between PLA and PA11 were effectively improved due to the compatibilizer of PLA-g-(St-co-GMA). PA11 promoted the cold crystallization and enhanced the thermal stability of PLA matrix. The reactive blends displayed a higher viscosity with unchanged rheological behaviors compared with PLA. In comparison with PLA MBs, the average fiber diameter and pore size of PLA/PA11/PLA-g-(St-co-GMA) MBs were slightly increased, whereas the strength and toughness were significantly improved. All the PLA/PA11/PLA-g-(St-co-GMA) MBs presented high air permeability and low filtration resistance. High filtration efficiency (>99.8%) could also be obtained especially for the target particles with diameters larger than 2.5 µm.

Optimization of the mechanical and thermal properties of isotactic polypropylene (iPP) homopolymer blended with relatively new low molecular low modulus polypropylene (LMPP) at different blend ratios was carried out via surface response methodology (RSM). Regression equations for the prediction of optimal conditions were achieved considering eight individual parameters: naming, elongation at break, tensile strength and elastic modulus, crystallization temperature (T_C), first melting temperatures (T_M1), heat fusion (Hf), crystallinity, and melt flow rate (MFR), which were measured as responses for the design of experiment (DOE). The adjusted and predicted correlation coefficient (R²) shows good agreement between the actual and the predicted values. To confirm the optimal values from the response model, supplementary experiments as a performance evaluation were conducted, posing better operational conditions. It has been confirmed that the RSM model was adequate to reflect the predicted optimization. The results suggest that the addition of LMPP into iPP could effectively enhance the functionality and processability of blend fibres if correctly proportioned.

The emergence of graphene-based polymer composite fibers provides a new opportunity to study the high-performance and functional chemical fibers. In this work, we have developed an efficient and convenient method with polydopamine (PDA) to functionalize and reduce graphene oxide (GO) simultaneously, and the modified graphene nanosheets can obtain uniform dispersion and strong interfacial bonding in nylon 6 (PA6). Furthermore, the reinforced PA6 composite fibers were prepared through mixing PDA-rGO into the PA6 polymer matrix and then melt spinning. The functional modification was characterized by surface analysis and structural testing including SEM, TEM, FTIR, and Raman. When the addition amount of the modified GO was 0.15 wt%, the tensile strength and Young’s modulus of the composite fiber reached 310.4 MPa and 462.3 MPa, respectively. The results showed a meaningful reinforcement with an effect compared to the pure nylon 6 fiber. Moreover, the composite fiber also exhibited an improved crystallinity and thermal stability, as measured by DSC and TGA.

Dynamic oscillatory shear testing is used to investigate polymeric viscoelastic behaviors. Small and large amplitude oscillatory shear tests are the canonical method for characterizing the linear and nonlinear viscoelastic behaviors of any polymeric material. With prominent and abundant work on linear viscoelastic studies, the nonlinear behavior is evasive in terms of generating infinite higher harmonics in the nonlinear regime. For this reason, intrinsic nonlinearities from large amplitude oscillatory shear (LAOS) studies have recently been used for insights on microstructural behaviors. This study is carried out for linear and nonlinear viscoelastic behavior with a main focus on LAOS of isostatic polypropylene (iPP) and relatively new low molecular weight and low modulus polypropylene-based polyolefin (LMPP) blends. The morphological results showed reduced spherulitic crystal nucleus size and increased distribution in blends with increasing LMPP. The blends showed subtle linear viscoelastic responses with strong nonlinear mechanical responses to variant strain and stress compared to pure iPP. The intracycle strain thickening and intracycle strain stiffening of high-content LMPP blends were comparatively dominant at medium strain amplitudes.