Blends Of Polyamide Research Articles

Polyamide 6 Recycled Fishing Nets Modified with Biochar Fillers: an Effort Toward Sustainability and Circularity

In a further research effort toward sustainability and circularity, this work demonstrates the possibility of designing and producing novel blends derived from recycled polyamide 6 (PA6) fishing net, incorporating two biochars, i.e., carbonaceous materials obtained from the controlled pyrolysis of vegetable biomasses, at different loadings (namely 5, 10, and 15wt.%). The biochar derived from lignocellulosic biomass enhanced both the mechanical properties and moisture resistance of the recycled polyamide, increasing the elastic modulus from 2.6 to 4.5GPa and reducing water uptake from 3.6 to 1.8%. Interestingly, thanks to its high silica content, the biochar derived from rice husk accounted for an increase in the activation energy for combustion of the polymer matrix (from 43.6 to 70.9kJ/mol). However, it also showed a detrimental effect on the water uptake and the mechanical behaviour of the blends. Besides, the possibility of replacing up to 15wt.% of petroleum-derived carbon black pigments with the biochars decreased the overall cost of PA6 blends. Also considering the biochar densities that are lower than those of traditional carbon fillers, the proposed blends may pave the way for the design, development, and exploitation of novel sustainable materials suitable for lightweight applications.

Miscibility of Non-Uniform Aliphatic Polyamide Mixtures.

Mixing different aliphatic polyamides provides opportunities to tune and optimize the properties of these semicrystalline polycondensates. Combining experiment and theory, we predict and explain the miscibility of aliphatic polyamide mixtures. Visual inspection and Raman spectroscopy of polyamide mixtures show that liquid/liquid phase demixing occurs in the melt due to limited miscibility. The large number of potential polyamide mixtures makes it challenging to test all miscibilities experimentally. Moreover, the dependence of miscibility on dispersity and the presence of water implies further challenges to a systematic experimental approach. Our theory predicts polyamide miscibility, while accounting for amide content, non-uniformity, and moisture content, using generalizations of Flory-Huggins theory. Predicted miscibilities align with experimental results obtained on tested mixed polyamides. The gained insights guide the optimization of functional polyamide blends.

Studies on mechanical, thermal, rheological and impact properties of polyamide 6 and thermoplastic copoly(ether-ester) elastomer blends

A series of blends of polyamide 6 (PA-6) (nylon-6) and a copoly(ether-ester) (HYTREL) were prepared by the melt-mixing method using a twin-screw extruder. The HYTREL content was varied from 0% to 25% by weight of the blends. Thermal and rheological studies on the blends using differential scanning calorimetry, dynamic mechanical analysis (DMA) and capillary rheometer showed that the blends are semi-compatible in nature. A two-phase globular morphology of the blends was established by scanning electron microscope (SEM) analysis. The matrix ligament thickness (interparticle distance) in each blend composition was measured from SEM images and compared with those calculated using Wu’s equation. The impact strength of the blends as measured by the Izod impact test was found to be substantially improved as a result of the incorporation of HYTREL. The toughness determined by loss area calculation from the DMA spectrum showed similar trends. The toughness was found to be optimal in a blend having 15 wt.% HYTREL with an average dispersed particle size of around 450 nm. The yield stress of the blend decreased in comparison to PA-6 on addition of HYTREL, while the thermal stability of PA-6 remained unaffected.

Towards the Reuse of Fire Retarded Polyamide 12 for Laser Sintering.

The control of powder aging during Selective Laser Sintering (SLS) processing is one of the challenges to be overcome for the implementation of this technique in serial production. Aging phenomena, because of the elevated temperatures and long processing times, need to be considered when a fraction of the polymer powders present in the build chamber and not used to manufacture the parts are reused at various times. The aim of this study was to investigate the influence of successive reuse of blends of pure Polyamide 12 and its blends with two types of flame retardants (FR): ammonium polyphosphate (APP) and zinc borate (ZB). The composition of the blends was 70/30 (wt/wt) PA 12/FR. Four successive processing stages have been carried out by collecting the remaining powder blend each time. The powders were re-used using the same processing parameters after sieving. DSC measurements showed that the incorporation of FRs entailed a reduction in the processing window up to 4 °C; nevertheless, no further reduction was noted after aging. The TGA curves of aged blends of powders were also similar for pure PA 12 and PA 12 with FR. In addition, initial and reused powders presented a higher degree of crystallinity than the specimens processed from the powders. The heterogeneous character of the PA 12 after LS processing or reprocessing was shown through Pyrolysis Combustion Flow Calorimetry (PCFC) and cone calorimeter (CC) tests. FTIR analysis also showed that post-condensation reactions have occurred. The mode of action of the flame retardants was clearly seen on HRR curves at both tests. The first reuses of PA 12 powders entailed a significant reduction in time to ignition at the cone calorimeter (150 for the initial material to around 90 s for the reused material), indicating the formation of short polymer chains. Only in the case of zinc borate was it noticed that re-used powder was detrimental to the fire performance because of a strong increase in the value of pHRR (between 163 and 220 kW/m2 for reused material instead of 125 kW/m2 for the initial one).

Tribological Properties of Recycled Polyvinyl Butyral (rPVB) and Glass-Fiber-Reinforced Polyamide Blends in Dry and Microabrasive Contacts

As a contribution of recycling of polymers in the automotive industry, recycled polyvinyl butyral (rPVB) from automotive windshields is being explored as a solid lubricant reinforcement for improving lubricity of engineering polymers. This work aims to evaluate the tribological behavior (coefficient of friction [CoF] and wear resistance) of polyamide 6 (PA6) and glass-fiber-reinforced polyamide 6 (PAGF) blended with rPVB as solid lubricant under two-body and three-body abrasive conditions. The different polymer blends were produced by adding recycled polyvinyl butyral (rPVB) into a matrix of either a commercial polyamide 6 (PA6) or a commercial 30% glass-fiber reinforced polyamide 6 (PAGF). The tribological tests were conducted in an instrumented microabrasion tester for generating wear and measuring the coefficient of friction (CoF) in both dry and microabrasion conditions. In the dry condition, rPVB was effective in reducing the CoF for both PA6 and PAGF. Two-body abrasion was found as the predominant wear pattern in the dry condition. On the other hand, in the microabrasion condition, the additions of rPVB were not totally effective since they produced a wear resistance increase for PAGF but a reduction for PA6, which was ascribed to a notable decrease in toughness for PA6 when adding rPVB. Well-defined plowing traces and several SiC particles embedded in the scars were the predominant patterns in all the materials. In both PA6 and PAGF, CoF increased with the rPVB additions.

Boosting polyamide 6: a comparative study on graphene and graphene oxide for improved mechanical and thermal properties

ABSTRACT This study investigates the impact of incorporating graphene (G) and graphene oxide (GO) on the mechanical and thermal properties of polyamide 6 (PA6) composites. We employ a melt-extrusion process to achieve homogeneous dispersion of varying G and GO loadings (1.0–5.0 wt%) within the PA6 matrix. Notably, 2.0 wt% of both G and GO achieve excellent dispersion, leading to significant enhancements in the degradation temperature and a reduction in the thermal decomposition rate of the PA6 blends. Compared to the neat PA6, these composites exhibit improved (mention specific mechanical properties observed, e.g. tensile strength, modulus). This research establishes a novel and cost-effective approach to improve the processability, mechanical properties, and thermal stability of PA6, making it a valuable contribution for applications demanding high performance.

Binary blends of polyamide 6 with aliphatic polyketone: the compatibility analysis of polymer components

The compatibility and interactions of polyamide 6 (PA6) and aliphatic polyketone (APK) were studied when they were mixed in a melt by extrusion. Using the relaxation spectrometry (RS) method, it was shown that the studied PA6/ APK blends had one glass transition temperature (Тg) located on the temperature scale between Тg of initial PA6 and APK. It was also found that in these mixtures, the PA6 b-relaxation peak, responsible for the local movement of small-scale structural units of the main chain and side branches, was socialized with the b-peak of APK. On this basis, conclusions were drawn about the compatibility of PA6 and APK at the segmental and small-scale level. The mutual influence of polymer components of PA6/APK blends on the dynamic shear modulus and the zG3 criterion is shown. The DSC analysis has revealed a slowdown in the crystallization of PA6 and APK in their blends, which is probably due to the formation of extensive interfacial (transitional) layers in the PA6/APK blend, in which crystallization of polymer components is hindered due to intermolecular interactions. The analysis of the IR-spectra in the range of 3000–3800 cm–1 has made it possible to establish the formation of hydrogen bonds between the polyamide –NH-groups and carbonyls –C=O, being part of APK, which contributes to an increase in the compatibility of the polymer components of the blend under study.

Recycling Polyethylene/Polyamide Multilayer Films with Poly(isoprene-g-Maleic Anhydride) Compatibilizer.

Polymers generally form incompatible mixtures that make the process of recycling difficult, especially the mechanical recycling of mixed plastic waste. One of the most commonly used films in the packaging industry is multilayer films, mainly composed of polyethylene (PE) and polyamide (PA). Recycling these materials with such different molecular structures requires the use of compatibilizers to minimize phase separation and obtain more useful recycled materials. In this work, commercial polyisoprene-graft-maleic anhydride (PI-g-MA) was tested as a compatibilizer for a blend of PE and PA derived from the mechanical recycling of PE/PA multilayer films. Different amounts of PI-g-MA were tested, and the films made with 1.5% PI-g-MA showed the best results in terms of mechanical properties and dart impact. The films were also characterized thermally via thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), using Fourier-transform infrared spectroscopy (FTIR), and morphologically using a scanning electron microscope (SEM). Other parameters, such as tearing and perforation, were analyzed.

MoEpPOSS nanotaneciğinin PA6/TPE karışımlarının morfolojik ve reolojik özelliklerine etkisinin incelenmesi

Polyamide 6 (PA6) is one of the used engineering thermoplastics with the advantages of high resistance to chemicals and abrasion, high fatigue resistance and toughness. However, it has some disadvantages such as low impact strength and notch sensitivity. The blend of PA6 with elastomers can mitigate these shortcomings. Lately, thermoplastic elastomers (TPE) have been frequently used to toughen notch-sensitive polymers such as PA6 due to their outstanding properties such as high elasticity, recyclability, and easy processing. As it is known, obtaining superior properties in polymer blends relies on the interfacial interaction between the components of the blend. Additionally, by using compatibilizers, blends with the required properties can be created by enhancing interaction between phases, or interfacial adhesion. Recently, polyhedral oligomeric silsesquioxane (POSS) nanoparticles, organic/inorganic hybrid nanoparticles, are preferred as an alternative compatibilizer to conventional types. In this study, PA6/TPE blends were compatibilized with POSS nanoparticle with single epoxy group (MoEpPOSS). The morphological and rheological properties of PA6/TPE blends compatibilized with MoEpPOSS nanoparticle were investigated. Also, possible chemical interactions between PA6 and/or TPE and MoEpPOSS nanoparticle were determined via Fourier transform infrared spectroscopy (FTIR) analyses.

Multifunctional nanocomposites based on a polyamide 6/polyamide 12 blend and multi‐walled carbon nanotubes

AbstractNanocomposites based on an immiscible blend of polyamide 6 (PA6) and polyamide 12 (PA12) 50/50 wt.% with different contents of multi‐walled carbon nanotubes (MWCNTs) were prepared by extrusion followed by compression molding. These materials have been proved to be electrically conductive in previous investigations for the range of filler content assayed. The morphology of the nanocomposites was analyzed using scanning electron microscopy, both on cryo‐fractured and postmortem uniaxial tensile samples. Rheological measurements were performed along with differential scanning calorimetry, to assess the materials microstructure and thermal transitions. Furthermore, uniaxial tensile tests were carried out to determine mechanical properties such as stiffness, strength, and strain at break and to investigate the effect of MWCNTs on these properties. Finally, fracture tests were also conducted to evaluate how incorporating MWCNTs affected nanocomposites toughening capabilities. The obtained results suggest a notable improvement in the mechanical properties in the nanocomposites with low amounts of nanofiller. This expands their potential applications as conductive polymer composites (CPCs) and positions them as promising multifunctional materials.Highlights CPCs based on a PA blend and MWCNTs were successfully obtained. CNTs strongly affected the blend morphology and rheological properties. CNTs significantly modified the crystallization behavior of PA6. Ductility greatly improved at low CNT contents but decreased at high loadings. Stiffness increased steadily with increasing CNT content.

Thermal oxidation of blends of polypropylene and polyamide 6/66. Effect of inhibition

The thermal oxidation of the blends of isotactic polypropylene (PP) and mixed copolyamide PA6/66 has been studied in a wide range of compositions: 0, 5, 10, 20, 30, 40, 50 and 100 wt % PA6/66. Data obtained by differential scanning calorimetry (DSC) and FTIR indicate the immiscibility of two polymer phases in the blends. The melting enthalpy of mixtures is increased during oxidation that is explained by chemi-crystallization of PP under PP oxidation. PA6/66 component is found to retard the growth of PP enthalpy during PP oxidation. According to DSC data on the PP/PA6/66 blends in air, PA6/66 phase greatly enhances the oxidation onset temperature of the PP/PA6/66 blends thus indicating the improved thermal stability of new material. The oxygen consumption of the PP/PA6/66 blends at 130°C proceeds with a large oxidation induction time (OIT) which is increased with increase in PA6/66 content. After OIT is ended, a constant oxidation rate is established, which is characteristic of the autoxidation mechanism. Kinetic analysis of the thermal oxidation of the PP/PA6/66 blends was carried out on the base of two models of polyolefin autooxidation with hydroperoxide decomposition via the 1st or the 2nd order reaction. The both models were found to describe the experimental kinetic curves of the oxygen consumption. Two possible explanations of the inhibition of PP oxidation by PA6/66 phase are discussed. The migration of active radicals from the PP phase to the PA6/66 phase with their transformation into low-active PA6/66 radicals may be responsible for inhibition and an increase in OIT of PP. Another mechanism of OIT increase may be related with a change in the structure of the PP/PA6/66 blends depending on PA6/66 content.

From Waste Vegetable Oil to a Green Compatibilizer for HDPE/PA6 Blends.

When properly compatibilized, the blending of polyethylene (PE) and polyamide (PA) leads to materials that combine low prices, suitable processability, impact resistance, and attractive mechanical properties. Moreover, the possibility of using these polymers without prior separation may be a suitable opportunity for their recycling. In this work, the use of an epoxidized waste vegetable oil (EWVO) was investigated as a green compatibilizer precursor (CP) for the reactive blending of a high-density PE (HDPE) with a polyamide-6 (PA6). EWVO was synthesized from waste vegetable cooking oil (WVO) using ion-exchange resin (Amberlite) as a heterogeneous catalyst. HDPE/PA6 blends were produced with different weight ratios (25/75, 75/25, 85/15) and amounts of EWVO (1, 2, 5 phr). Samples with WVO or a commercial fossil-based CP were also prepared for comparison. All the blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), rheology, and mechanical tests. In the case of HDPE/PA6 75/25 and 85/15 blends, the addition of EWVO at 2 phr showed a satisfactory compatibilizing effect, thus yielding a material with improved mechanical properties with respect to the blend without compatibilizer. On the contrary, the HDPE/PA6 25/75 ratio yielded a material with a high degree of crosslinking that could not be further processed or characterized. In conclusion, the results showed that EWVO had a suitable compatibilizing effect in HDPE/PA6 blends with high HDPE content, while it resulted in unsuitable for blends with high content of PA6.

Crystallization and Performance of Polyamide Blends Comprising Polyamide 4, Polyamide 6, and Their Copolymers.

Polyamide 4 (PA4) is a biobased and biodegradable polyamide. The high hydrogen bond density of PA4 bestows it with a high melting point that is close to its thermal decomposition temperature, thereby limiting the melt processing of PA4. In this study, PA4 was blended with polyamide 6 (PA6) and further modified with copolyamide 4/6 (R46). The effects of composition on the crystallization behavior of the blends were studied. The results demonstrated that the binary PA4/PA6 (B46) and ternary PA4/PA6/R46 (B46/R46) blends formed two crystalline phases (PA4- and PA6-rich phases) through crystallization-induced phase separation. With increasing PA6 content, the thermal stability and crystallinity of the B46 blend increased and decreased, respectively, and the contribution of PA6 toward the crystallization of the PA4-rich phase diminished. Molecular dynamics simulations showed the molecular chain orientation of the B46 blends well. The melting points, crystallinities, and grain sizes of the B46/R46 blends were lower than those of the B46 blends. The crystallization of the PA4-rich phase was restrained by the dilution effect of molten-state PA6, and the nucleation and crystallization of the PA6-rich phase were promoted by the presence of crystallized PA4. The B46 blends with 30-40 wt% PA6 had the best mechanical properties.

Eutectic In Situ Modification of Polyamide 12 Processed through Laser-Based Powder Bed Fusion.

Laser-based powder bed fusion (LPBF) of polymers allows for the additive manufacturing of dense components with high mechanical properties. Due to inherent limitations of present material systems suitable for LPBF of polymers and required high processing temperatures, the present paper investigates the in situ modification of material systems using powder blending of p-aminobenzoic acid and aliphatic polyamide 12, followed by subsequent laser-based additive manufacturing. Prepared powder blends exhibit a considerable reduction of required processing temperatures dependent on the fraction of p-aminobenzoic acid, allowing for the processing of polyamide 12 at a build chamber temperature of 141.5 °C. An elevated fraction of 20 wt% of p-aminobenzoic acid allows for obtaining a considerably increased elongation at break of 24.65% ± 2.87 while exhibiting a reduced ultimate tensile strength. Thermal investigations demonstrate the influence of the thermal material history on thermal properties, associated with the suppression of low-melting crystalline fractions, yielding amorphous material properties of the previously semi-crystalline polymer. Based on complementary infrared spectroscopic analysis, the increased presence of secondary amides can be observed, indicating the influence of both covalently bound aromatic groups and hydrogen-bound supramolecular structures on emerging material properties. The presented approach represents a novel methodology for the energy-efficient in situ preparation of eutectic polyamides, potentially allowing for the manufacturing of tailored material systems with adapted thermal, chemical, and mechanical properties.

High impact strength of aliphatic polyketone/polyamide 6 blends induced by a chemical reaction

Compatibility and physical properties of aliphatic polyketon (PK)/polyamide 6 (PA6) blend were investigated. The PK and PA6 showed high adhesion strength and thus impact strength of PK/PA6 blends was very high. It was observed that PK-PA6 copolymers are formed by a chemical reaction between the two polymers and the copolymers act as a reactive compatibilizer in the PK/PA6 blends. The presence of the PK-PA6 copolymer was confirmed by FTIR analysis. The adhesion strength between PK and PA6 was very high compared to a typical incompatible polymer pair. PA6 investigated herein has two end groups, NH2 and carboxylic acid. We also adopted end-capped PA6 that has two carboxylic acid end groups. The adhesion strength and impact strength of the PK/end-capped PA6 blends was much lower than that of PK/PA6 blends. More importantly, the PK-PA6 copolymer was not formed in the PK/end-capped PA6 blends. Thus, it was concluded that the chemical reaction occurs between the carbonyl of PK and the primary amine end group of PA6. Due to the high impact strength of PK/PA6 blends, possible applications could be automotive parts where higher impact strength is required.

Molecular dynamics simulation and non-isothermal crystallization kinetics of polyamide 4 and different bio-based polyamide blends.

The effects of the structural units and blending ratio on the crystallization behavior of blends of polyamide 4 (PA4) with polyamide 56 (PA56) and polyamide 11 (PA11) were studied using molecular dynamics simulations and non-isothermal crystallization kinetics. The simulation results show that the crystallinity of PA4/PA56 blends (B4/56) with a PA56 content of 30-50% was 3.5-10.8% lower than that of B4/56 with a PA56 content of 20%, and the crystallinity of PA4/PA11 blends (B4/11) decreased by 9.5% as PA11 content increased from 20% to 50%. The experimental results show that both B4/56 and B4/11 form PA4- and PA56-rich (PA11-rich) phases through crystallization-induced phase separation. The interplanar spacing of the PA4-rich phase of B4/56 changed relative to that of PA4, indicating that some PA56 entered the PA4-rich phase unit cell. As the PA56 content increased from 20% to 50%, the crystallinity of B4/56 decreased by 11.2%, and the crystallization-induced phase separation grew distinct. The B4/56 with a higher PA4 content crystallized more easily. As the PA11 content increased from 20% to 50%, the crystallinity of B4/11 decreased by 12.5%, and PA11 barely participated in the crystallization of the PA4-rich phase. The blending ratio had no significant effect on the crystallization rate and crystal-growth degree of B4/11, and the non-isothermal crystallization activation energy of B4/11 was significantly higher than that of B4/56, indicating that the crystallization ability of the B4/11 blend system is worse. This study provides a theoretical basis for the design and performance regulation of PA4-based polyamide blends.

High-throughput 3D printing of continuous carbon fiber–reinforced Polyamide 6/Maleic Anhydride-modified Polypropylene/polypropylene composite by a multifilament feeder

A multifilament feeder was developed to achieve the high-throughput 3D printing of continuous carbon fiber–reinforced thermoplastic composites. Four filaments were supplied to the feeder and simultaneously printed by controlling the feeding speeds to quadruple the manufacturing volume. A water-resistant filament was also developed by the polymer blending of polyamide 6 (PA6) and polypropylene (PP), which provided good adhesion to the carbon fibers and water resistance, respectively. The polymer structure in the continuous carbon fiber–reinforced thermoplastic composites was characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The multilayer polymer structure was observed, which enhanced the water-resistant property. The bending test results revealed that the blending minimized the degradation of the flexural modulus of the 3D-printed unidirectional carbon fiber–reinforced thermoplastic composite under wet conditions.

Strengthening of polyamide 6 and isosorbide-containing copolyester immiscible blends by in-situ reactive compatibilization

Polyamide 6 (PA6) is a representative engineering plastic and is used in various fields due to its impact, chemical, and weather resistance. In industrial applications that require high impact strength, glass-fiber-reinforced PA6 is often used. It is important to note, however, that due to the high hardness of glass fibers, screws and injection molds are very easily worn during extrusion and injection. Poly (ethylene glycol 1,4-cyclohexanedimethylene isosorbide terephthalate) (PEICT) is a copolyester containing isosorbide derived from biomass and has the characteristics of high impact resistance. In this study, PA6 and PEICT blends were prepared by melt processing. A reactive compatibilizer with multifunctional epoxy groups was introduced to reduce the interfacial tension of immiscible PA6 and PEICT. The epoxy groups reacted with the terminal groups of blend components to form branched PA6-co-PEICT copolymers. The copolymers inhibited the aggregation of PEICT and improved the interfacial adhesion between PA6 and PEICT, effectively performing compatibilization. In the successful PA6/PEICT blend, an impact strength of 29.59 kJ/m2 was achieved, comparable with glass fiber reinforced PA6.

Biobased Polyamide Blends (PA610/PA1010)—A Miscibility Analysis

In the present work, blends of biobased polymers were formulated using two polyamides made from biorenewable resources. Polyamide 610 (PA610) and polyamide 1010 (PA1010) were meltmixed in different compositions, producing polymer blends with renewable carbon content from 74 to 89%. Physical properties of the PA610/PA1010 blends were investigated by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and impact strength testing. From the DMTA results, it was possible to identify a single glass transition temperature (Tg) for each PA610/PA1010 blend. The measurements of the impact testing show intermediate values compared to the pure polymers. The DSC thermograms show melting point depression for the PA610 crystals with increasing PA1010 content. All those results indicate the two polyamides are fully miscible in the melt in the composition range investigated.

Engineered polylactide (PLA)–polyamide (PA) blends for durable applications: 1. PLA with high crystallization ability to tune up the properties of PLA/PA12 blends

Engineered polylactide (PLA)–polyamide (PA) blends for durable applications: 1. PLA with high crystallization ability to tune up the properties of PLA/PA12 blends