Injection-Molded Parts of Partially Biobased Polyamide 610 and Biobased Halloysite Nanotubes

Development of Eco-Efficient Composite from Textile Waste with Polyamide Matrix

The main aim of the present work is to evaluate and characterize the mechanical, morphological and thermal properties of wastes coming from the textile industry, mainly composed of cotton and polyester. These wastes will be thereafter implemented in commodity plastic such as polyamide, in order to develop new formulations of environmentally friendly materials. The composites were produced by extrusion and injection-molded processes in amounts between 15 wt.% and 60 wt.% of textile waste. With the objective of improving the properties of the materials, silanes were used as a compatibilizer between the textile fibers and the polymeric matrix. The effect of the compatibilizer in the composites was studied together with the effect of the amount of textile fiber added to the composites. Mechanical, thermal, morphological and wettability properties were analyzed for each composite. The results show that the use of silanes improves the interaction especially in those composites with a higher amount of textile waste, offering a balanced mechanical behavior with significantly high quantities. On the other hand, the melting temperature does not vary significantly with the introduction of silanes and textile waste content, although the incorporation of textile waste slightly reduces up to 23% the degradation temperature of the resulting composites. The wettability of the composites is also increased up to 16% with the incorporation of textile waste. Finally, the appearance of the composites with textile waste is strongly influenced by the incorporation of the reinforcement, offering shades close to dark brown in the whole range of compositions.

Morphological, Thermal, and Mechanical Properties of Nanocomposites Based on Bio-Polyamide and Feather Keratin-Halloysite Nanohybrid

One solution to comply with the strict regulations of the European Commission and reduce the environmental footprint of composites is the use of composite materials based on bio-polymers and fillers from natural resources. The aim of our work was to obtain and analyze the properties of bio-polymer nanocomposites based on bio-PA (PA) and feather keratin-halloysite nanohybrid. Keratin (KC) was mixed with halloysite (H) as such or with the treated surface under dynamic conditions, resulting in two nanohybrids: KCHM and KCHE. The homogenization of PA with the two nanohybrids was conducted using the extrusion processing process. Two types of nanocomposites, PA-KCHM and PA-KCHE, with 5 wt.% KC and 1 wt.% H were obtained. The properties were analyzed using SEM, XRD, FTIR, RAMAN, TGA, DSC, tensile/impact tests, DMA, and nanomechanical tests. The best results were obtained for PA-KCHE due to the stronger interaction between the components and the uniform dispersion of the nanohybrid in the PA matrix. Improvements in the modulus of elasticity and of the surface hardness by approx. 75% and 30%, respectively, and the resistance to scratch were obtained. These results are promising and constitute a possible alternative to synthetic polymer composites for the automotive industry.

Thermodynamic characteristics of the aliphatic polyamide crystal structures: Enhancement of nylon 66α, 610α and 77γ polymers

Despite the polymer industry's reliance on nylon polymers, numerous questions remain about their crystal structures, modeling, and other features. This work discusses the thermodynamic properties and molecular modeling of a polyamides nylon 66α, 610α, and 77γ crystal structure systems for use in various electronics and Nano-devices that feature distinct properties such as exceptional optoelectronic properties at a low cost compared to other structures. This study looked at the crystal structure of a linear polyamide chain made up of repeating units. The influence of the thermal expansion coefficient and thermodynamic parameters on crystal structures' characteristics at different temperatures has previously been explored. The findings of this study demonstrate, on the one hand, the influence of the amorphous phase on the final thermodynamic characteristics of semi-crystalline polymers and, on the other hand, pave the way for greater improvement in the durability of these polymers by increasing their crystalline features. The values of the thermodynamic parameters for nylon 66α, 610α and 77γ such as enthalpy (ΔHExp.) were 35.08, 40.25, and 1.44 kJ/mol, entropy (ΔSExp.) 113.75, 128.84, and 15.10 J/mol-K, free energy (ΔGExp.) was -44.57, -46.62, and -6.86 kJ/mol, respectively. When the nylon data is compared, the nylon 610α exhibits a significantly higher free energy, at high temperatures, the process is spontaneous and exergonic, making it a potentially viable material for use as fibers and engineering thermoplastics.

Non-Isothermal Crystallization Kinetics of Montmorillonite/Polyamide 610 Nanocomposites

Non-isothermal crystallization kinetics of montmorillonite (MMT)/polyamide 610 (PA610) composites were readily prepared by in situ melt polymerization followed by a full investigation in terms of their microstructure, performance, and crystallization kinetics. The kinetic models of Jeziorny, Ozawa, and Mo were used in turn to fit the experimental data, in all of which Mo's analytical method was found to be the best model for the kinetic data. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) studies were used to investigate the isothermal crystallization behavior and MMT dispersion levels in the MMT/PA610 composites. The experiment results revealed that low MMT content can promote the PA610 crystallization, whilst high MMT content result in MMT agglomeration, and reduce the PA610 crystallization rate.

Development and Characterization of High Environmentally Friendly Composites of Bio-Based Polyamide 1010 with Enhanced Fire Retardancy Properties by Expandable Graphite

Bio-based polyamide 1010 was melt-compounded with different percentages (2.5 to 10.0 wt.%) of expandable graphite (EGr) as an environmentally friendly solution to improve the flame retardancy properties. The mechanical, morphological, thermal and fire retardancy properties (among others) are analysed. The novelty of the article lies in the use of fully removable polyamide. The effect of the incorporation of EGr in the properties of this polymer was analysed and characterised. The incorporation of EGr into the PA1010 matrix led to very promising results. Mechanically, the EGr provided increased stiffness and a tensile strength up to 7.5 wt.%, verifying good mechanical performance. The DMTA results also show how the incorporation of EGr in the PA1010 matrix clearly increases the stiffness of the composites over the entire temperature range analysed. In terms of physical properties, water absorption of PA1010 was reduced particularly in the 10% EGr, which reduces the water absorption of PA1010 by 20%. In terms of flame retardant properties, with the incorporation of EGr, a significant reduction in the heat release rate (HRR) values as the concentration of the additive increases and a reduction in the maximum peak heat release rate (pHRR) can be observed for all compounds. In particular, it goes from 934 kW/m2 for neat polyamide to a value of 374 kW/m2 with 10% EGr. Finally, an improvement in the UL-94 rating of the 7.5 and 10% EGr composites was also observed, going from V-2 in the PA to V-1 in these composites.

The Effect of Halloysite Nanotubes on the Fire Retardancy Properties of Partially Biobased Polyamide 610

The main objective of the work reported here was the analysis and evaluation of halloysite nanotubes (HNTs) as natural flame retardancy filler in partially biobased polyamide 610 (PA610), with 63% of carbon from natural sources. HNTs are naturally occurring clays with a nanotube-like shape. PA610 compounds containing 10%, 20%, and 30% HNT were obtained in a twin-screw co-rotating extruder. The resulting blends were injection molded to create standard samples for fire testing. The incorporation of the HNTs in the PA610 matrix leads to a reduction both in the optical density and a significant reduction in the number of toxic gases emitted during combustion. This improvement in fire properties is relevant in applications where fire safety is required. With regard to calorimetric cone results, the incorporation of 30% HNTs achieved a significant reduction in terms of the peak values obtained of the heat released rate (HRR), changing from 743 kW/m2 to about 580 kW/m2 and directly modifying the shape of the characteristic curve. This improvement in the heat released has produced a delay in the mass transfer of the volatile decomposition products, which are entrapped inside the HNTs' lumen, making it difficult for the sample to burn. However, in relation to the ignition time of the samples (TTI), the incorporation of HNTs reduces the ignition start time about 20 s. The results indicate that it is possible to obtain polymer formulations with a high renewable content such as PA610, and a natural occurring inorganic filler in the form of a nanotube, i.e., HNTs, with good flame retardancy properties in terms of toxicity, optical density and UL94 test.

Post-Forming Mechanical Properties of a Polymer Sheet Processed by Incremental Sheet Forming: Insights into Effects of Plastic Strain, and Orientation and Size of Specimen

The innovative Incremental Sheet Forming (ISF) process affects the post-forming properties of thermoplastic polymers. However, the effects of degree of plastic strain, and the orientation and size of specimen on the mechanical properties are still unknown. In the present study, therefore, the ISF process is performed on a polymer sheet by varying the plastic strain ranging from 6% to 108%. The corresponding effects on the properties and associated polymer structure are quantified by conducting a variety of mechanical and structural tests. The results reveal that the post-ISF tensile properties like yield stress, ultimate stress, drawing stress, elastic modulus and elongation decrease from 26.6 to 10 MPa, 30.5 to 15.4 MPa, 18.9 to 9.9 MPa, 916 to 300 MPa and 1107% to 457%, respectively, as the strain increases in the investigated range. The value of post-ISF relaxation properties, contrary to the tensile properties, increases with increasing strain up to 62%. Particularly, reductions in stress, strain and modulus increase from 41% to 202%, 37% to 51%, and 41% to 202%. As regard the orientation effect, the sheet in the feed direction shows greater strength than the transverse direction (up to 142% in yield stress and 72% in ultimate stress). Moreover, the smaller sample offers greater strength than the larger one (up to 158% in yield stress and 109% in ultimate stress). The analysis of the post-ISF tensile properties and structural results lead us to conclude that the drop in the tensile properties due to increasing strain occurs due to corresponding increase in the voids area fraction (1.25% to 31%) and a reduction in the crystallinity (38% to 31%).