Semi-aromatic Polyamide Research Articles

Study on reaction kinetics of bio-based semi-aromatic high temperature polyamide PA10T/1010

Study on reaction kinetics of bio-based semi-aromatic high temperature polyamide PA10T/1010

Synthesis and properties of bio-based semi-aromatic heat-resistant copolymer polyamide 5T-co-6T

ABSTRACT Herein, poly(pentanediamine terephthalamide) (PA5T) homopolymer was synthesized via a salt-forming reaction+solid state polycondensation method using bio-based 1,5-pentanediamine and terephthalic acid as the primary raw materials. To address the issue of its narrower processing window, poly(hexamethylene terephthalamide)(PA6T), which also cannot be melt processed due to the processing window is negative, was introduced into its molecular chain to synthesize poly (pentanediamine/hexanediamine terephthaloyl) (PA5T-co-6T) copolymers. The structures were investigated by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance carbon spectroscopy (13C-NMR). Furthermore, the melting temperature, crystallization temperature, thermal stability, and crystal growth mode of the polymer were tested and analyzed using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and wide-angle x-ray diffraction (WAXD), respectively. The results demonstrate that the crystal growth mode gradually changes from three-dimensional spherical growth to two-dimensional disk-like or three-dimensional spherical growth with the increase of 6T chain segment content. Simultaneously, the crystallization temperature, melting temperature, and crystallization rate of the polymer all showed a trend of decreasing first and then increasing, which was due to the combined effects of the increase in the content of 6T chain segments on the molecular-chain structure and crystal structure of the polymer. Bio-based PA5T-co-6T has excellent heat resistance and a wider processing window than PA5T and PA6T, which possesses great application prospects in the fields of automotive, electronic appliances, and LED optics.

One-step facile pathway synthesis of PAPXD/1214-PEA thermoplastic elastomer: Structure and properties

In this study, a novel and facile one-step synthesis route was conducted to prepare semi-aromatic polyamide elastomer (PAPXD/1214-PEA) with p-phenylenediamine, dodecane diamine, dodecanedioic acid and polyether amine (PEA) as monomers. A systematic investigation has been conducted into the effect of hard segment content on the thermal, mechanical and solvent resistance of polymers when semi-aromatic polyamides are used as hard segments. It was found that the melting point of the copolymers gradually increased from 191.2 °C to 231.5 °C with the hard segment content increased from 39 % to 76 %, while the Vicat softening temperature (VST) enhanced from 103.2 °C to 192.2 °C. Compared with the commercial polyamide elastomer Pebax@ (produced by Arkema Inc) with similar hard segment contents, the VST of PAPXD14/1214-PEA were 17.4–66.2 °C higher. The mechanical performance of these elastomers was also largely improved with tensile strength increasing from 15.1 to 40.6 MPa, Young's modulus from 28.2 to 168.7 MPa, toughness from 91.1 to 170.7 MJ/m3. In addition, the solvent resistance properties of PAPXD14/1214-PEA was compared with the commercial polyamide elastomer Pebax@. After soaking in hydrochloric acid for 24 h, the tensile strength of PAPXD/1214-PEA with the hard segment content increased from 50 % to 63 % decreased down to 9.4 and 14.4 MPa, respectively. While the commercial polyamide elastomer Pebax@ (with similar hard segment content) decreased down to 1.5 and 4.3 MPa, indicating the commercial polyamide elastomer products were deteriorated. This suggests the corrosion resistance of the synthesized PAPXD/1214-PEA is much better than that of commercial product, and these semi-aromatic polyamide elastomers can be potentially applied in some harsh service environment especially for high temperature and corrosion sealing.

A Novel Semiaromatic Polyamide Thermoplastic Elastomer with Excellent Heat Resistance and Mechanical Properties

A Novel Semiaromatic Polyamide Thermoplastic Elastomer with Excellent Heat Resistance and Mechanical Properties

Evaluation of nanofiltration and reverse osmosis membranes for efficient rejection of organic micropollutants

Nanofiltration (NF) and reverse osmosis (RO) membranes have revolutionized water treatment processes. However, emerging separations, such as the removal of organic micropollutants (OMPs), pose a challenge for traditional RO and NF membranes due to either low water permeance (RO) or inadequate OMP rejection (NF). In this work, we investigated the rejection of thirteen frequently detected OMPs at environmentally relevant low feed concentration of 12 μg/L by using a wide range of commercial RO and NF polyamide thin-film composite (TFC) membranes and an in-house prepared NF membrane. The membranes were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), contact angle, and surface charge measurements. We investigated removal capabilities of OMPs at standard brackish water RO operating conditions (i.e., 15.5 bar transmembrane pressure, pH 8) and also examined the effect of feed solution transmembrane pressure on membrane performance. The rejection of ionic OMPs was strongly influenced by electrostatic repulsion effects, whereas rejection of non-ionic solutes was primarily driven by size exclusion and hydrophobic/hydrophilic interactions. The best performing TFC membranes — a lab-made semi-aromatic piperazine-based NF polyamide membrane and a fully aromatic commercial polyamide NF membrane (NF1) — displayed excellent rejection of OMPs comparable to a commercial RO seawater membrane (RO4), but exhibited ∼2-fold and ∼6-fold higher water permeance, respectively.

Thermoplastic Toughening of a Semiaromatic Polyamide with an Amino-telechelic Polyethylene.

Semiaromatic polyamides are used for metal replacement in advanced engineering applications to reduce weight and improve efficiency, but their range of application is limited by their inherent lack of ductility and toughness. Here, we combined semiaromatic polyamide poly(hexamethylene terephthalamide-co-isophthalamide) (PA6TI) with up to 30 wt % amine-terminated polyethylene (PE(NH2)2) by high-temperature melt compounding, which was suggested to lead to the formation of PA-PE block copolymers at the interface between the PE(NH2)2 and the PA6TI. This resulted in PA6TI/PE(NH2)2 blends with smaller, more uniform particle sizes than in PA6TI blended with nonfunctional PE or the commercial impact modifier, maleic anhydride-functionalized styrene-ethylene-butylene-styrene (SEBS) under the same conditions. The PA6TI/PE(NH2)2 blends and the corresponding glass fiber-reinforced composites consequently showed significantly greater increases in room-temperature tensile ductility and fracture energy with respect to unmodified PA6TI, as well as maintained mechanical stability at high temperatures, and only modest decreases in stiffness and strength, even at high PE(NH2)2 contents. These improvements were attributed to the crystallinity of the PE(NH2)2 particles and to improved morphological stabilization and matrix-particle adhesion, consistent with the presence of PA-PE block copolymer at the matrix-particle interfaces.

Preparation and Desalination of Semi-Aromatic Polyamide Reverse Osmosis Membranes (ROMs)

Reverse osmosis membrane (ROM) technology has a series of advantages, such as a simple process, no secondary pollution, high efficiency, energy saving, environmental protection, and good separation and purification effects. High-performance semi-aromatic polyamide reverse osmosis membranes (ROMs) were prepared by interfacial polymerization (IP) of novel cyclopentanecarbonyl chloride (CPTC) and m-phenylenediamine (MPD) monomers. The surface morphology, hydrophilicity and charge of the ROMs were characterized by field-emission scanning electron microscopy (SEM), a contact angle tester and a solid-surface zeta potential analyzer. The effects of CPTC concentration, MPD concentration, oil-phase solvent type, IP reaction time and additive concentration on the performance of semi-aromatic polyamide ROMs were studied. SEM morphology characterization showed that the surface of the prepared polyamide ROMs presented a multinodal structure. The performance test showed that when the concentration of MPD in the aqueous phase was 2.5 wt.%, the concentration of sodium dodecylbenzene sulfonate (SDBS) was 0.2%, the residence time in the aqueous phase was 2 min, the concentration of CPTC/cyclohexane in the oil phase was 0.13 wt.%, the IP reaction was 20 s, the NaCl rejection rate of the semi-aromatic polyamide ROM was 98.28% and the flux was 65.38 L/m2·h, showing good desalination performance. Compared with an NF 90 commercial membrane, it has a good anti-BSA pollution ability.

Semi-Aromatic Polyether Amide Thermoplastic Elastomer: Nucleophilic Substitution Polymerization and Properties

Different from the traditional electrophilic polymerization method of thermoplastic elastomer, here, we adopted a new nucleophilic reaction route, which did not need extreme high temperature and vacuum condition to prepare a novel kind of semi-aromatic thermoplastic polyether amide elastomers. First, difluoro-terminated semi-aromatic di-amide monomer containing long chain ether (or 1,12-diaminododecane) was synthesized through facile interfacial electrophilic substitution reaction. Then, they were conducted to react with hydroquinone under atmospheric pressure to yield polyether amide elastomer. Additionally, a small amount of branched structure with trifluoro-terminated semi-aromatic amide monomer was designed and further introduced into the polymer chain to adjust the mechanical property. These semi-aromatic polyamide elastomers were found to have excellent thermal properties with glass transition temperature (Tg) of −39.5 to −34.8 °C, melting temperature (Tm) of 227.3–260.4 °C [which is much higher than that of the commercial products such as Pebax5533 (Arkema, Paris, France) (Tm = 159 °C)], the 5% weight-loss temperature (Td,5%) of 376.3–408.7 °C, and Vicat softening temperature of 73.0–223.6 °C. The mechanical properties of these resultant elastomers were good and can be controlled with different copolymerization ratios of soft, hard, and branched segments. The tensile strength, elongation at break, and elasticity modulus were in the range of 9.8–23.4 MPa, 87.6–712.3%, and 30.8–362.0 MPa, respectively. Besides, such a series of copolymers showed a relatively low water absorption of 1.57–3.67%. Interestingly, it was found that these resultant polyether amide elastomers had better organic solvent resistance and acid–base corrosion than the traditional TPAE-containing ester bond (−COO−) in the polymer molecular chain. It can be potentially applied in the chemical mechanical seal, especially in the high temperature and corrosion environment.

The Structural Evolution and Mechanical Properties of Semi-Aromatic Polyamide 12T after Stretching.

The development of semi-aromatic polyamides with excellent mechanical properties has always been a popular research avenue. In this work, the semi-aromatic polyamide 12T (PA12T) with the maximum tensile strength of 465.5 MPa was prepared after stretching at 210 °C 4.6 times. Wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) were used to characterize the structural evolution of semi-aromatic polyamide 12T (PA12T) after stretching at different stretching temperatures and stretching ratios. The formation mechanism of this change in mechanical properties was investigated from different aspects of the aggregated structure such as crystal morphology, crystal orientation and crystallinity. The relevant characterization results show that the crystal structure, crystal orientation and crystallinity of PA12T were the highest when the sample was pre-stretched at 210 °C, which is crucial for improving the mechanical properties of PA12T. These findings will provide important guidance for the preparation of polymer materials with excellent mechanical properties.

Polyamide nanofiltration membranes with rigid–flexible microstructures for high-efficiency Mg2+/Li+ separation

Lithium extraction from salt-lake brine with a high Mg2+/Li+ ratio is crucial for mitigating lithium supply shortage. Positively charged polyamide nanofiltration membranes, which are often prepared by performing interfacial polymerization (IP) using polyethyleneimine and trimesoyl chloride, are considered to be promising candidates for Mg2+/Li+ separation owing to their high energy efficiency and low environmental impact. However, the performance of these membranes is severely hindered by “useless pores” and “defects” present in the flexible polyamide layer. Herein, we provide a facile strategy for modifying flexible semi-aromatic polyamide chains by intercalating a rigid electropositive monomer, histamine, to remold the internal pores and positive charge density at a molecular level. Two routes, namely, “swelling-embedding-reacting-shrinking (SERS)” and “in-situ interposition (SIP)” were used to construct a new polyamide layer with rigid–flexible microstructures. The fabricated SERS-0.50 membrane showed a 5-fold higher water flux and 2-fold increase in the Mg2+/Li+ separation factor compared with the IP membrane. Moreover, the SIP-0.15 membrane with an enhanced positive charge density exhibited a considerably higher Mg2+/Li+ separation factor (15.38, 500 % increase compared with that of the IP membrane) for brine with a Mg2+/Li+ ratio of 20. This study provides a reference for developing nanofiltration membranes used for high-efficiency Mg2+/Li+ separation.

Oxidation resistances of polyamide nanofiltration membranes to hydroxyl and sulfate radicals

The oxidation compatibility with polyamide membranes is an important feature of nanofiltration (NF) technology in practical water treatment processes. In this study, we systematically investigated the oxidation resistance of fully aromatic (NF90) and semi-aromatic (NF270) polyamide NF membranes to reactive oxidative species including SO4•- and HO• in terms of membrane surface properties and filtration performance. SO4•− and HO• exhibit different oxidative behaviors in NF membranes with different polyamide structures. The HO•-dominated oxidation significantly damaged the membrane integrity of NF90 and NF270, with notably varied surface morphology, hydrophilicity, and charge. Further analysis of the chemical property on membrane surfaces revealed that the SO4•−-dominated oxidation was more reactive to the N moieties (N–H or N–C) of the NF90 membrane, whereas HO• unselectively reacted with polyamides. The radicals also impact the permselectivity (water permeability and salt rejection) of the NF90 and NF270 membranes in different ways. The NF90 membrane after SO4•−-exposure exhibited higher water permeability and slightly decreased salt rejection, whereas the permselectivity of the NF270 membrane was more significantly affected by HO•-exposure. To further reveal the underlying oxidation mechanisms, polyamide monomers were selected to react with the peroxodisulfate solutions. The results demonstrated that a fully aromatic polyamide membrane was more resistant to oxidative radicals than a semi-aromatic polyamide membrane. This study will facilitate the development of novel antioxidant membranes and provide information for selecting appropriate membrane materials in specific water treatment processes.

Fire-safe and tough semi-aromatic polyamide enabled by halloysite-based self-assembled microrods

High performance flame-retardant engineering plastics are highly desirable in electronic appliances, automotive industry, and aerospace fields. However, traditional flame retardants usually lead to impaired intrinsic properties of plastics, especially mechanical properties. Here, we present a hybrid flame retardant with unique hierarchical microrod structure via self-assembly of halloysite nanotube loaded with phenylphosphinic acid. The resultant hybrid integrates excellent thermal stability (Td = 406 °C), interfacial adhesion, and superior flame-retardant efficiency, that endows semi-aromatic polyamide great mechanical properties (tensile strength 67.3 MPa and 73.2 MPa)，improving by 27% and 38% via 5 wt% and 10 wt% addition, compared to that of pristine resin, and excellent flame retardancy with anti-dripping and self-extinguishing (UL-94 V-0, LOI 30.4%) via 10 wt% addition. Meanwhile this hybrid is demonstrated, with 5 wt% or 10 wt% addition of self-assembly halloysite, the composites can form an effective char barrier, that emphasize its fire-safety properties in simulating fire scenario via approximately halving peak of heat release rate and peak of carbon monoxide release rate of the composites. This self-assembly strategy outlined here paves a novel and facile approach for fabrication and widely application of high performance fire-safety polyamides. This will largely improve the reliability of materials in service, reduce the fire probability of electronic devices and casualties caused by fire.

Synthesis and thermal degradation mechanism of a semi-aromatic copolyamide from renewable sources

Bio-based polyamide has attracted increasing attention in recent years. However, it remains a challenge to synthesize bio-based polyamide combining excellent high temperature resistance and mechanical properties. And the thermal degradation mechanism of pentamethylenediamine-based semi-aromatic polyamide has not been reported. In this work, a semi-aromatic bio-based polyamide (PA5T/56) with high melting point, excellent mechanical properties, and high temperature resistance comparable to petroleum-based polyamide (PA6T/66) was successfully synthesized. The thermal degradation behaviors of PA5T/56 and PA6T/66 were characterized via TG-FTIR-MS and Py/ GC–MS, and the possible thermal degradation mechanisms were proposed. Different from PA6T/66, unique pyridines were traced in the degradation volatiles of PA5T/56 because of the cyclization tendency of the pentamethylenediamine structural unit. Moreover, the thermal degradation mechanism of PA5T/56 was mainly dominated by cleavage-cyclization of C–N bond accompanied by high-temperature radical cleavage reaction. This work will provide theoretical and practical basis for the design of bio-based high temperature resistant polyamide.

One-step method for synthesis of bio-based semi-aromatic high-temperature polyamide PA5T/56 and its non-isothermal crystallization kinetics

One-step method for synthesis of bio-based semi-aromatic high-temperature polyamide PA5T/56 and its non-isothermal crystallization kinetics

Effect of Aliphatic Chain Length on the Stress–Strain Response of Semiaromatic Polyamide Crystals

Effect of Aliphatic Chain Length on the Stress–Strain Response of Semiaromatic Polyamide Crystals

Semi-aromatic polyamide membrane incorporated with yolk-shell mesoporous hybrid nanospheres for ultrahigh permeability and improving comprehensive property

In this report, yolk-shell (YS) organic-inorganic hybrid nanospheres (YSHNs) with radially ordered mesopores were synthesized by a co-assembly strategy using 1,2-bis(triethoxysilyl)ethane and tetraethoxysilane as precursors, and cetyltrimethylammonium bromide as a soft template. Then, Silver nanoparticles (AgNPs) were uniformly embedded in the hollow cavities of the YSHNs. The semi-aromatic polyamide (SAP) based nanocomposite membrane was fabricated using 1,3,5-cyclohexane tricarbonyl chloride as an organic phase, meta-phenylene diamine as an aqueous phase, and the mesoporous YS hybrid nanospheres as nanoadditives by an interfacial polymerization approach. The results show that the YS nanospheres were successfully incorporated into the polyamide (PA) separation layer, and the membrane becomes very hydrophilic. The membrane incorporated with the aminated YS mesoporous nanospheres exhibits ultrahigh pure water permeability (PWP, 9.34 L m−2 h−1 bar−1) and comparable NaCl rejection (96.1%), which is dramatically higher than the membrane with common mesoporous nanospheres. It is because that the hollow cavity of the YS nanosphere further decreases the membrane resistance, and the aminated spherical surface improves the interfacial compatibility between the PA matrix and the YS nanospheres. Furthermore, the flexible YS hybrid structure and the mesoporous core could play an important buffering for avoiding the shell fracture under a high operation pressure. The chlorine resistance of the YS-nanosphere incorporated membrane is significantly improved compared to the pristine SAP membrane in a strong chlorination strength (5500 ppm h, pH = 5). The confined AgNPs in the YS mesostructure endow the membrane with a sustainable antibiofouling property. Moreover, the polylysine modification improves the membrane fouling resistance and performance stability.

Evaluating the integration of nanofiltration membranes in advanced water reclamation schemes using synthetic solutions: From phosphorous removal to phosphorous circularity

The more stringent regulations related to the reduction of residual phosphorous concentration in treated wastewater and the consideration of phosphorous as a critical raw material are boosting new technologies towards its recovery from waste effluents. The concentration of phosphate in these effluents can be easily increased using nanofiltration (NF) due to its high phosphate rejections (>99%) in order to recover it as a raw material for the fertilizer industry. In this work, different model solutions were used to characterise the transport of phosphate species across a semi-aromatic polyamide membrane (NF270) using the Solution-Electro-Diffusion-Film coupled with reactive transport (SEDFRT) model. Experiments were carried out with waters containing one dominant salt (NaCl or Na2SO4) and one trace salt (dihydrogen or hydrogen phosphate salts) to easily determine membrane permeances to species without simulating the complexity of real solutions. Besides, for the first time the transport of H+ and OH– was also modelled. Results showed a high performance of NF270 when separating phosphate (rejections higher than 90%). Finally, the obtained permeances were used to evaluate the recovery capacity of phosphate as struvite from a model secondary treatment effluent through the SEDFRT model. Results demonstrate the potential of NF as a step forward towards closing the urban phosphorus cycle.

Improved interfacial shear strength in carbon fiber enhanced semi-aromatic polyamide 6T composite via in-situ polymerization on fiber surface

The interfacial property of carbon fiber (CF) reinforced semi-aromatic poly (hexamethylene terephthalamide) (PA6T) thermoplastic composite has been improved by in-situ polymerization on fiber surface. On that basis, PA6T oligomer was coated upon fiber to form a reactive polymeric layer and modified fiber surface structure. SEM, FTIR and XPS analysis were conducted to investigate its surface status, finding that CF was perfectly wetted and formed a much rougher surface on which large quantity of polar –CO–NH- groups attached. After polymerization under 320 oC for 10 min, this layer could bond tightly around fiber. And TGA results demonstrated that polymerized layer had excellent heat-resistance and possessed an initial decomposition temperature over 400 °C. A microbond test was implemented to accurately evaluated the interfacial shear strength (IFSS), meanwhile, a facile approach of “spraying” was applied to form microdroplets in quantity onto single carbon fiber within a few minutes. It was found that the fiber and the matrix was efficiently bonded and the interaction was efficaciously enhanced by the polymeric layer, thus 20.9% of IFSS and 20.9% of bulk composites’ tensile strength improvement were achieved compared to those without modification. Notably, the in-situ polymerization formed a gradient transition of interfacial modulus and raised the interphase thickness to 800 nm, thus a “buffer” in interphase region was established. Our work provided a facile method to manufacture high-performance thermoplastic composite with outstanding interfacial property and broaden its application in advanced materials field.

Study on reaction kinetics of bio-based semi-aromatic high-temperature polyamide PA5T/56

Study on reaction kinetics of bio-based semi-aromatic high-temperature polyamide PA5T/56

Micro and macro analysis of physicochemical properties of bio-based semi-aromatic high temperature polyamide PA5T/56

ABSTRACT In this paper, bio-based semi-aromatic high-temperature polyamide PA5T/56 was synthesized from bio-based monomer glutamine. The micro and macro physicochemical properties of PA5T/56 were studied by Materials Studio software, Universal Testing Machine and Impact Testing Machine and other software and instruments, and the effect of PA5T content on its properties was explored. The results showed that the Poisson’s ratio and modulus of PA56 molecule were the largest, PA5T molecule was the smallest, and PA56T molecule was between the two, indicated that the addition of PA5T molecule enhances the overall mechanical properties; With the increase in PA5T content, the tensile strength and bending strength of PA5T/56 increases, while the elongation at break and impact strength decreases, the density of PA5T/56 increases first and then decreases, and the oil absorption rate and water absorption rate of PA5T/56 decrease gradually; Moreover, PA5T/56 has excellent solvent resistance, it is insoluble in conventional organic solvents and only soluble in concentrated sulfuric acid and trifluoroacetic acid; With the extension of soaking time, the tensile strength and bending strength of PA5T/56 decrease, while the impact strength of PA5T/56 increases first and then decreases.