Search Results (22)

Polyamides (PAs) are widely used as barrier materials in offshore oil and gas (O&G) equipment due to their mechanical strength and chemical resistance. However, long-term exposure to hydrogen sulfide scavengers (H₂S-SCVs) may significantly affect their physicochemical properties. Previous studies using thermal analysis and ¹H time-domain NMR (¹H TD-NMR) suggest that ethoxylated H₂S-SCVs impose molecular constraints, increasing the glass transition temperature (T_g) and reducing chain mobility above T_g. The present study builds upon these findings using a multi-technique analytical approach, including FTIR, Raman, ¹H DQ-TD-NMR, and ¹³C solid-state NMR (ssNMR), to provide a more comprehensive understanding of the molecular alterations in PA materials. The results clearly demonstrate that H₂S-SCV exposure leads to the progressive exudation of plasticizers from the PA matrix. This plasticizer loss is a key factor contributing to the observed shift in Tg and the reduction in molecular mobility. ¹H DQ-TD-NMR data confirmed an increase in the density of dynamically constrained chains over time and allowed for the characterization of heterogeneity in these constraints throughout the PA matrix. Moreover, ¹³C ssNMR spectra revealed the presence of immobilized H₂S-SCV chemical groups within the polymer matrix, strongly supporting the early statement that the mobility constraints observed in ¹H DQ-TD-NMR are associated with the formation of crosslinks induced by the H₂S-SCV: H₂S-SCV acts as a crosslinking agent. Taken together, our findings indicate that both plasticizer loss and H₂S-SCV-induced crosslinking contribute significantly to the microstructural evolution of PAs when exposed to ethoxylated H₂S-SCVs, offering important insights into their degradation mechanisms and long-term behavior in aggressive operational environments. Full article

Long-chain hyperbranched polyesters (LHBPx, x = 1, 2, 3) with varying lengths of branched chains were synthesized through a thiol-ene click reaction. Subsequently, LHBPx was incorporated into PA4 via the solution method to prepare a LHBPx/PA4 polymer blend, aiming to address the limitations of PA4, such as its narrow thermal processing window (△T = T_d5−T_m) and high brittleness. The results demonstrated that the addition of LHBPx enhanced the △T of PA4 from 1.6 °C to 14.5 °C (LHBP₃/PA4), increasing the rheological properties of LHBPx/PA4 polymer blends, thereby improving its thermal processability. Compared with PA4, the elongation at the break of the LHBP₃/PA4 polymer blend was increased by 20.4%, and the brittle fracture was changed into a ductile fracture. The crystallinity of PA4 was greatly decreased, from 54.41% to 37.42%, owing to the incorporation of LHBPx, whereas T_m of PA4 had almost no change. It was explained that LHBPx hindered the crystal growth stage, whereas it promoted the nucleation stage of PA4, resulting in no significant change in crystal type. Moreover, the longer the branched chain of LHBPx was, the more pronounced the improvement in the thermal processability and toughness of PA4 became. Above all, this work was meaningful for the potential application of PA4 in industrial plastics. Full article

Polyamides’ properties are greatly influenced by the polymerization process and the type of feedstock used. The solid forms of nylon salts play a significant role in determining the final characteristics of the material. This study focuses on the long-chain bio-nylon 512. Firstly, we systematically investigated the possible solid forms of the nylon 512 salt, including crystal forms and morphologies, by massive experimental screening, single-crystal X-ray diffraction, Hirshfeld surface analysis, and TG-DSC measurements. The regulation and control of the various solid forms were achieved through solid-state transformations (SSTs) and solution-mediated phase transformations (SMPTs). Our findings shows that the nylon 512 salt exists in two crystal forms (anhydrate and dihydrate) and four morphologies (needle-like, plate-like, rod-like, and massive block crystal). Many factors will influence the formation of these solid forms, such as water activity, temperature, solvent, and ultrasonic physical fields. We can choose the right factors to regulate this as needed. On this basis, we studied the effects of different solid forms (crystal forms and morphologies) on the properties of the resulting polyamides prepared using direct solid-state polymerization (DSSP). The solid form of the salt had many effects on the polymer, including its structure, melting point, and mechanical properties. The polyamide obtained through DSSP of the anhydrate salt exhibited a higher melting point (204.22 °C) and greater elastic modulus (3.366 GPa) compared to that of the dihydrate salt, especially for the anhydrate salt of plate-like crystals. Full article

Pharmaceutical packaging is one of the most used packaging types which contains aluminum and plastics. Due to increasing amounts of waste and rising environmental concerns, recycling approaches are being investigated. Since blisters usually contain a balanced amount of plastics and metals, most of the approaches focus on recycling only one material. Therefore, more sustainable recycling approaches which recover both plastic and aluminum fractions are needed. This study investigates the thermal behavior and degradation mechanisms of plastic-rich and aluminum-rich pharmaceutical blisters using various analytical techniques. Structural characterization revealed that plastic-rich blisters have a thicker profile with plastic and aluminum layers, while aluminum-rich blisters consist of plastic layers between aluminum sheets. Thermal degradation analysis showed two main stages for both types: plastic-rich blisters (polyvinyl chloride) exhibited significant weight loss and long-chain hydrocarbon formation between 210 and 285 °C, and aluminum-rich blisters (polyamide/nylon) degraded from 240 to 270 °C. Differential Scanning Calorimetry and Fourier Transform Infrared Spectroscopy analyses confirmed the endothermic behavior of such a transformation. The gas emissions analysis indicated an increased formation of gasses from the thermal treatment of plastic-rich blisters, with the presence of oxygen leading to the formation of carbon dioxide, water, and carbon monoxide. Thermal treatment with 5% O₂ in the carrier gas benefited plastic-rich blister treatment, reducing organic waste by up to 80% and minimizing burning risk, leveraging pyrolytic carbon for protection. This method is unsuitable for aluminum-rich blisters, requiring reduced oxygen or temperature to prevent pyrolytic carbon combustion and aluminum oxidation. Full article

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). Full article

This study investigated the role of constructing a dual network in toughening bio-based long-chain polyamide 610 (PA610) composites. Rheological studies were conducted to reveal the effects of toughening agent type and content on the material properties. According to the variation trend of mechanical properties and the appearance of a rheological low-frequency plateau of the materials, the percolation network concentration ϕ_c of the toughening agent in the PA610 matrix was determined to be 13.5 vol.%. The interfacial interaction of the composite was evaluated through the percolation theory, and the scaling value v = 1.36 for both indicated the good affinity between PA610 and the toughening agent. Rheology results found that the combination of ethylene terpolymer (PTW) and maleic anhydride-g-styrene-b-(ethylene-butylene)-b-styrene (MAH-SEBS) could achieve an optimal balance between the mechanical properties and fluidity of the composites. Furthermore, the addition of ultra-high-molecular-weight polytetrafluoroethylene (PTFE), in conjunction with the toughening agent, facilitated the construction of a dual semi-interpenetrating network. The strengthened intermolecular interactions restricted the relative slippage and mobility of the polymer chains and therefore enhanced the strength and toughness of the material. This study provides new possibilities and approaches for optimizing the comprehensive properties of bio-based polyamide materials. Full article

The rheological properties of a polyamide (PA) resin with low crystallinity were modified by melt-mixing it with a small amount of an alternative α-olefin–maleic anhydride copolymer as a reactive compound. Because PA has a low melting point, rheological characterization was performed over a wide temperature range. Owing to the reaction between PA and the alternative α-olefin–maleic anhydride copolymer, the blend sample behaved as a long-chain branched polymer in the molten state. The thermo-rheological complexity was obvious owing to large flow activation energy values in the low modulus region, i.e., the rheological time–temperature superposition principle was not applicable. The primary normal stress difference under steady shear was greatly increased in the wide shear rate range, leading to a large swell ratio at the capillary extrusion. Furthermore, strain hardening in the transient elongational viscosity, which is responsible for favorable processability, was clear. Because this is a simple modification method, it will be widely employed to modify the rheological properties of various polyamide resins. Full article

Polyamide-6 (PA) is a popular textile polymer having desirable mechanical and thermal properties, chemical stability, and biocompatibility. However, PA nanofibers are prone to bacterial growth and user discomfort. ε-Poly-L-lysine (PL) is non-toxic, antimicrobial, and hydrophilic but lacks spinnability due to its low molecular weight. Given its similar backbone structure to PA, with an additional amino side chain, PL was integrated with PA to develop multifunctional nanofibers. This study explores a simple, scalable method by which to obtain PL nanofibers by utilizing the structurally similar PA as the base. The goal was to enhance the functionality of PA by addressing its drawbacks. The study demonstrates spinnability of varying concentrations of PL with base PA while exploring compositions with higher PL concentrations than previously reported. Electrospinning parameters were studied to optimize the nanofiber properties. The effects of PL addition on morphology, hydrophilicity, thermal stability, mechanical performance, and long-term antimicrobial activity of nanofibers were evaluated. The maximum spinnable concentration of PL in PA-based nanofibers resulted in super hydrophilicity (0° static water contact angle within 10 s), increased tensile strength (1.02 MPa from 0.36 MPa of control), and efficient antimicrobial properties with long-term stability. These enhanced characteristics hold promise for the composite nanofiber’s application in medical and protective textiles. Full article

The search for alternatives to petroleum-based thermoplastic polyamide elastomers (TPAEs) has recently drawn great interest. In this study, a bio-massed TPAE, PA12,36, was synthesized using 1,12-dodecanediamine (DDA) and fatty dimer acid (FDA, Pripol^TM1009) precursors via catalyst and solvent-free melt polycondensation. The molecular structure and molecular weight of the PA12,36 were characterized by ¹H NMR, FTIR, and GPC. PA12,36 displayed a low melting temperature of 85.8 °C, an initial degradation temperature of 425 °C, and a glass-transition temperature of 30.4 °C, whereas it sustained satisfactory tensile strength (10.0 MPa) and superior strain at break (1378%). Furthermore, PA12,36 was foamed by supercritical CO₂, and the cell size, cell density, and porosity were determined. The entangled long-chained FDA component generated a physically crosslinked network, which promoted the melt viscosity of PA12,36 against elongations of foam cell growth and increased foamability significantly. As a result, uniform structured cellular foams with a cell diameter of 15–24 µm and high cell density (10¹¹ cells/cm³–10¹² cells/cm³) were successfully achieved. The foaming window was widened from 76 to 81 °C, and the expansion ratio was increased from 4.8 to 9.6. Additionally, PA12,36 foam with a physically crosslinked structure presented a better creep shape recovery percentage (92–97.9%) and sturdier dimensional stability. This bio-based PA12,36 foam is a promising candidate to replace petroleum-based thermoplastic elastomer foams for engineering applications, particularly shoe soles. Full article

SPECPs are electrochromic polymers that contain special engineering plastic structural characteristic groups (SPECPs). Due to their high thermal stability, mechanical properties, and weather resistance, they are also known as high-performance electrochromic polymer (HPEP or HPP). Meanwhile, due to the structural characteristics of their long polymer chains, these materials have natural advantages in the application of flexible electrochromic devices. According to the structure of special engineering plastic groups, SPECPs are divided into five categories: polyamide, polyimide, polyamide imide, polyarylsulfone, and polyarylketone. This article mainly introduces the latest research on SPECPs. The structural design, electrochromic properties, and applications of these materials are also introduced in this article, and the challenges and future development trends of SPECPs are prospected. Full article

Temperature-responsive materials are highly interesting for temperature-triggered applications such as drug delivery and smart packaging. Imidazolium Ionic Liquids (ILs), with a long side chain on the cation and a melting temperature of around 50 °C, were synthetized and loaded at moderate amounts (up to 20 wt%) within copolymers of polyether and a bio-based polyamide via solution casting. The resulting films were analyzed to assess their structural and thermal properties, and the gas permeation changes due to their temperature-responsive behavior. The splitting of FT-IR signals is evident, and, in the thermal analysis, a shift in the glass transition temperature (Tg) for the soft block in the host matrix towards higher values upon the addition of both ILs is also observed. The composite films show a temperature-dependent permeation with a step change corresponding to the solid–liquid phase change in the ILs. Thus, the prepared polymer gel/ILs composite membranes provide the possibility of modulating the transport properties of the polymer matrix simply by playing with temperature. The permeation of all the investigated gases obeys an Arrhenius-type law. A specific permeation behavior, depending on the heating–cooling cycle sequence, can be observed for carbon dioxide. The obtained results indicate the potential interest of the developed nanocomposites as CO₂ valves for smart packaging applications. Full article

Multi-walled carbon nanotubes (MWCNTs) were modified on the tips and inner walls by 12-chloro-12-oxododecanedioic acid-methyl ester groups and then added to the polyamide composite membranes to prepare MWCNT-CH₂OCOC₁₂H₂₃O₂ membranes for desalination. The characterization results of transmission electron microscopy, Fourier transform, infrared transform, and thermogravimetric analysis showed that the 12-chloro-12-oxododecanedioic acid-methyl ester group was successfully grafted to the entrances and inner walls of the MWCNTs. The performance of the MWCNTs’ composite membranes was evaluated by scanning electron microscopy, contact angle, and filtration test. The modified membrane morphology is more uniform, and there is no structural damage. The grafting of carbon nanotubes with methyl 12-chloro-12-oxydodecyldicarboxylate could improve the hydrophilicity of the membrane. Under identical conditions, the water flux of MWCNT-CH₂OCOC₁₂H₂₃O₂ membranes was higher than that of the pristine carbon nanotube’s membrane, and the desalination rate was also slightly improved. Full article

Plastic products used in our daily life remain in the environment for a long time. Plastics decompose gradually into smaller fragments (<5 mm) known as microplastics. There are different sources of microplastics contamination, including plastic bags, masks, synthetic textiles, and various coatings. Microplastics’ smaller size enhances toxic pollutants’ adsorption, through which they are easily digested by small biota and finally accumulated along the food chain. Many studies are found concerning marine microplastic distribution and pollution; however, rarely do they address terrestrial contamination. The terrestrial species Eobania vermiculata, Rumina decollata, Porcellio, Armadillo, Lumbricus terrestris, and Scolopendra were evaluated as bioindicators for soil pollution by microplastics and some potentially toxic metallic elements. Microplastics were isolated with the help of caustic potash. The particles were characterized by infrared spectroscopy (FTIR); some associated potentially toxic metals were assessed in the filtrate by inductively coupled plasma spectrometry (ICP). The following polymers were present in all studied samples: copolyamide, nylon, high- and low-density polyethylene, polyamide, and polyester. In addition, the metallic elements antimony, iron, aluminum, selenium, and zinc were determined with different concentrations. Thus, terrestrial biota can serve as bioindicators for microplastic pollution of soil, which could act as a vector for potentially toxic elements. Full article

Novel thermoplastic polyamide elastomers (TPAEs) consisting of long-chain semicrystalline polyamide 1212 (PA1212) and amorphous polyetheramine were synthesized via one-pot melt polycondensation. The method provides accessible routes to prepare TPAEs with a high tolerance of compatibility between polyamide and polyether oligomers compared with the traditional two-step method. These TPAEs with 10 wt % to 76 wt % of soft content were obtained by reaction of dodecanedioic acid, 1,12-dodecanediamine, and poly(propylene glycol) (PPG) diamine. The structure–property relationships of TPAEs were systematically studied. The chemical structure and the morphologic analyses have revealed that microphase separation occurs in the amorphous region. The TPAEs that have long-chain PPG segments consist of a crystalline polyamide domain, amorphous polyamide-rich domain, and amorphous polyetheramine-rich domain, while the ones containing short-chain PPG segments comprise of a crystalline polyamide domain and miscible amorphous polyamide phase and amorphous polyetheramine phase due to the compatibility between short-chain polyetheramine and amorphous polyamide. These novel TPAEs show good damping performance at low temperature, especially the TPAEs that incorporated 76 wt % and 62 wt % of PPG diamine. The TPAEs exhibit high elastic properties and low residual strain at room temperature. They are lightweight with density between 1.01 and 1.03 g/cm³. The long-chain TPAEs have well-balanced properties of low density, high elastic return, and high shock-absorbing ability. This work provides a route to expand TPAEs to damping materials with special application for sports equipment used in extremely cold conditions such as ski boots. Full article

Cutinases are bacterial and fungal enzymes that catalyze the hydrolysis of natural cutin, a three-dimensional inter-esterified polyester with epoxy-hydroxy fatty acids with chain lengths between 16 and 18 carbon atoms. Due to their ability to accept long chain substrates, cutinases are also effective in catalyzing in vitro both the degradation and synthesis of several synthetic polyesters and polyamides. Here, we present a bioinformatics study that intends to correlate the structural features of cutinases with their catalytic properties to provide rational basis for their effective exploitation, particularly in polymer synthesis and biodegradation. The bioinformatics study used the BioGPS method (Global Positioning System in Biological Space) that computed molecular descriptors based on Molecular Interaction Fields (MIFs) described in the GRID force field. The information was used to generate catalophores, spatial representations of the ability of each enzymatic active site to establish hydrophobic and electrostatic interactions. These tools were exploited for comparing cutinases to other serine-hydrolases enzymes, namely lipases, esterases, amidases and proteases, and for highlighting differences and similarities that might guide rational engineering strategies. Structural features of cutinases with their catalytic properties were correlated. The “catalophore” of cutinases indicate shared features with lipases and esterases. Full article