Search Results (5)

Bio-based polyamide 56 (PA56) is a new sustainable material in the polyamide family. In this study, dyes suitable for PA56 fibers were experimentally screened from natural plants rich in pigments. The results showed that the preferred natural dyes for PA56 fabric are turmeric for a yellow hue, madder for a red hue, catechu for a brown hue, and indigo for a blue hue. A green hue was achieved by the two-bath dyeing method using indigo and turmeric, respectively. For a dyability comparison with conventional PA6 and PA66, PA56, PA6, and PA66 fabrics were woven under identical conditions and dyed with turmeric, madder, catechu, and commercial indigo extracts. PA56 fabric exhibited the best dye uptake and the fastest dyeing rate (PA56 > PA6 > PA66). The reason for the excellent dyeability of PA56 fibers was analyzed in terms of differential scanning calorimetry measurement and molecular dynamics simulations. The results showed that the lowest crystallinity was exhibited by PA56 (PA56 < PA6 < PA66); in addition, PA56 displayed the largest fractional free volume (PA56 > PA6 > PA66). These structural characteristics contribute to the excellent dyeability of PA56 fibers. Therefore, PA56 fibers are promising materials, as they are derived from a sustainable source and have superior dyeing properties compared to PA6 and PA66 fibers. Full article

Riverbed sediments act as potential retention reservoirs or transport corridors for microplastic particles (MPs) from river water to groundwater. Vertical concentration profiles of MPs, together with river water and groundwater analysis, provide insight into their fate and transport behavior in freshwater systems. However, such data remain scarce. This study provides a depth-specific analysis of MPs ≥ 100 µm (abundance, type, and size) in gravelly riverbed sediments down to 200 cm, along with river water and groundwater analysis. Three sediment freeze cores were collected from the Alpine Rhine, a channelized mountain stream with high flow velocities and permanent losing stream conditions. The average MP abundance in the riverbed was 3.1 ± 2.3 MP/kg (100–929 µm); in the river, 92 ± 5 MP/m³ (112–822 µm); and in the groundwater, 111 ± 6 MP/m³ (112–676 µm). The dominant polymer types in the riverbed were polypropylene (PP), polyvinyl chloride (PVC), and polyethylene terephthalate (PET) (>70%), while polyamide (PA) dominated in the river water (56%) and the groundwater (76%). The comparable MP concentration, particle sizes, and polymer types between river water and groundwater, as well as the vertical MP concentration profiles, indicate that even large MPs up to 676 µm are transported from river water to groundwater without significant retention in the gravel sediment. Full article

Weak bonds usually make macromolecules stronger; therefore, they are often used to enhance the mechanical strength of polymers. Not enough studies have been reported on the use of weak bonds in flame retardants. A water-soluble polyelectrolyte complex composed of polyethyleneimine (PEI), sodium tripolyphosphate (STPP) and melamine (MEL) was designed and utilized to treat bio-based polyamide 56 (PA56) by a simple three-step process. It was found that weak bonds cross-linked the three compounds to a 3D network structure with MEL on the surface of the coating under mild conditions. The thermal stability and flame retardancy of PA56 fabrics were improved by the controlled coating without losing their mechanical properties. After washing 50 times, PA56 still kept good flame retardancy. The cross-linking network structure of the flame retardant enhanced both the thermal stability and durability of the fabric. STPP acted as a catalyst for the breakage of the PA56 molecular chain, PEI facilitated the char formation and MEL released non-combustible gases. The synergistic effect of all compounds was exploited by using weak bonds. This simple method of developing structures with 3D cross-linking using weak bonds provides a new strategy for the preparation of low-cost and environmentally friendly flame retardants. Full article

Bio-based polymers can reduce dependence on nonrenewable petrochemical resources and will be beneficial for future sustainable developments due to their low carbon footprint. In this work, the feasibility of bio-based polyamide 56 (PA56) substituting petroleum-based PA66 is systematically investigated. The crystallization, melting, and decomposition temperature of PA56 were all lower than that of PA66. PA56 formed a γ crystal type with larger grain size and took a longer amount of time to complete the crystallization process since its crystallization rate was lower than that of PA66. Compared with PA66, PA56 exhibited a higher tensile strength of 71.3 ± 1.9 MPa and specific strength of 64.8 ± 2.0 MPa but lower notched impact strength. More importantly, the limited oxygen index and vertical combustion measurement results indicated that the flame retardancy of PA56 was better than PA66, and the LOI values and the UL94 result of PA56 were 27.6% ± 0.9% and V-2. It is worth noting that the PA56 fiber had superior biodegradability compared to the PA66 fiber. PA56 showed significant biodegradation from the eighth week, whereas PA66 remained clean until the sixteenth week (without obvious biodegradation taking place). Eventually, PA56 did not show significant differences compared to PA66 in terms of thermal and mechanical properties. However, PA56 had great advantages in flame retardancy and biodegradability, indicating that the bio-based PA56 could potentially replace petroleum-based PA66 in many fields. Full article

Polymer nanocomposites consist of a polymer matrix and reinforcing particles that have at least one dimension under 100 nm. The processing of nanocomposite polymers is the most important stage, determining the final properties of nanocomposites. Nanocomposites are now preferentially prepared by melt-mixing using conventional compounding processes such as twin-screw extrusion. Many processing parameters (polymer matrix type, content and type of nanofiller, barrel temperature, screw speed, number and shape of extruder screws, etc.) affect the properties of nanocomposites. This research work represents an investigation of the influence of processing parameters (amount of nanoclay filler, the screw rotation speed, and extruder barrel temperature) on the flexural properties of polyamide 12/nanoclay-reinforced nanocomposite. From the test results, it is apparent that an increase in nanoclay content from 1 to 8% significantly increases flexural strength. The obtained nanocomposite has a 19% higher flexural strength and a 56% higher flexural modulus than pure PA12. Mathematical models that show the dependence of flexural strength and flexural modulus on the processing parameters used were obtained as a result of this analysis. Full article