Commercial Polyamides Research Articles

Synthesis of Aromatic Polyamidines by the [2+2]-Cycloaddition Reaction

Aromatic polyamidines based on 4,4′-diphenylmethane diisocyanate and bisamides have been synthesized and studied. The one-step reaction of bisamides with diazocyanate according to the [2+2]-cycloaddition mechanism includes a concerted process of the formation of two new σ-bonds in the transition state. The formation of polyamidine occurs as a result of decarboxylation, which completes this reaction. Due to the availability of starting compounds, ease of synthesis, good solubility, and high heat resistance and thermal stability of the resulting polymers, there are wide opportunities for producing new materials by conventional industrial processes. Polyamidines have a sufficiently large set of important technological properties, which suggest their greater potential in relation to applied problems. The resulting film materials and glass-reinforced plastics based on polyamidines show high mechanical properties that are not inferior to those of materials made from commercial polyamides and polybenzimidazoles.

Metabolic engineering of Escherichia coli for polyamides monomer δ-valerolactam production from feedstock lysine.

Nylon 5 and nylon 6,5 are recently explored as new commercial polyamides, of which the monomer includes δ-valerolactam. In this study, a novel catalytic activity of lysine 2-monooxygenase (DavB) was explored to produce δ-valerolactam from L-pipecolic acid (L-PA), functioning as oxidative decarboxylase on a cyclic compound. Recombinant Escherichia coli BS01 strain expressing DavB from Pseudomonas putida could synthesize δ-valerolactam from L-pipecolic acid with a concentration of 90.3mg/L. Through the co-expression of recombinant apoptosis-inducing protein (rAIP) from Scomber japonicus, glucose dehydrogenase (GDH) from Bacillus subtilis, Δ1-piperideine-2-carboxylae reductase (DpkA) from P. putida and lysine permease (LysP) from E. coli with DavB, δ-valerolactam was produced with the highest concentration of 242mg/L. α-Dioxygenases (αDox) from Oryza sativa could act as a similar catalyst on L-pipecolic acid. A novel δ-valerolactam synthesis pathway was constructed entirely via microbial conversion from feedstock lysine in this study. Our system has great potential in the development of a bio-nylon production process. KEY POINTS: • DavB performs as an oxidative decarboxylase on L-PA with substrate promiscuity. • Strain with rAIP, GDH, DpkA, LysP, and DavB coexpression could produce δ-valerolactam. • This is the first time to obtain valerolactam entirely via biosynthesis from lysine.

Compatibility in biobased poly(L‐lactide)/polyamide binary blends: From melt‐state interfacial tensions to (thermo)mechanical properties

ABSTRACTThe melt compatibility between poly(L‐lactide) (PLA) and polyamides (PAs) with related thermomechanical properties is addressed. A particular attention is paid to four commercial PAs with extrusion processing temperatures close to PLA (PA10‐10 to PA12). PLA/PA blend morphologies without a compatibilizer are first revealed by scanning electron microscopy. PA12 displays the best droplet dispersion into PLA (Dn 700 nm), whereas a poor interfacial adhesion is attested for PLA/PA10‐10 blends. Interfacial tensions corroborate the PLA/PA10‐10 incompatibility (γ12 9 mN/m, 240 °C) with decreasing γ12 in the order PLA/PA10‐10 > PLA/PA11 > PLA/PA12 (γ12 2 mN/m). Surface tensions confirm the highest compatibility between PLA and PA12. Ductilities, toughnesses, and thermal resistances of PLA/PA blends are evaluated up to 40‐wt % PA. Brittle‐to‐ductile transitions are observed for PA content higher than 30‐wt % with the highest ductility for PLA/PA12, in accordance with their enhanced compatibility. Impact strengths display similar trends with a twofold increase for PLA/PA12. An outstanding synergy between PLA and PA is highlighted by dynamic mechanical analyses with heat deflection up to 130 °C for PLA/PA blends. The synergy arises from a peculiar crystallization of PLA in the presence of PA. PLA/PA morphologies/interfaces can be consequently tuned by an appropriate PA choice with interesting improvements of thermomechanical properties for high‐performance/durable applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48440.

Towards High-performance Materials Based on Carbohydrate-Derived Polyamide Blends.

A bio-derived monomer called 2,3:4,5-di-O-isopropylidene-galactarate acid/ester (GalXMe) has great potential in polymer production. The unique properties of this molecule, such as its rigidity and bulkiness, contribute to the good thermal properties and appealing transparency of the material. The main problem, however, is that like other biobased materials, the polymers derived thereof are very brittle. In this study, we report on the melt blending of GalXMe polyamides (PAs) with different commercial PA grades using extrusion as well as blend characterization. Biobased PA blends showed limited to no miscibility with other polyamides. However, their incorporation resulted in strong materials with high Young moduli. The increase in modulus of the prepared GalXMe blends with commercial PAs ranged from up to 75% for blends with aliphatic polyamide composed of 1,6-diaminohexane and 1,12-dodecanedioic acid PA(6,12) to up to 82% for blends with cycloaliphatic polyamide composed of 4,4′-methylenebis(cyclohexylamine) and 1,12-dodecanedioic acid PA(PACM,12). Investigation into the mechanism of blending revealed that for some polyamides a transamidation reaction improved the blend compatibility. The thermal stability of the biobased PAs depended on which diamine was used. Polymers with aliphatic/aromatic or alicyclic diamines showed no degradation, whereas with fully aromatic diamines such as p-phenylenediamine, some degradation processes were observed under extrusion conditions (260/270 °C).

Effect of ultraviolet light irradiation and sandblasting treatment on bond strengths between polyamide and chemical-cured resin

The aim of this study was to evaluate the effects of ultraviolet light (UV) irradiation and sandblasting treatment on the shear bond strength between polyamide and chemical-cured resin. Three types of commercial polyamides were treated using UV irradiation, sandblasting treatment, and a combining sandblasting and UV irradiation. The shear bond strength was measured and analyzed using the Kruskal-Wallis test (α=0.05). Comparing shear bond strengths without surface treatment, from 4.1 to 5.7 MPa, the UV irradiation significantly increased the shear bond strengths except for Valplast, whose shear bond strengths ranged from 5.2 to 9.3 MPa. The sandblasting treatment also significantly increased the shear bond strengths (8.0 to 11.4 MPa). The combining sandblasting and UV irradiation significantly increased the shear bond strengths (15.2 to 18.3 MPa) comparing without surface treatment. This combined treatment was considered the most effective at improving the shear bond strength between polyamide and chemical-cured resin.

Novel, Fully Biobased Semicrystalline Polyamides

Novel, semicrystalline polyamides and co(polyamides) were synthesized from biobased sebacic acid (SA), 2,5-diamino-2,5-dideoxy-1,4;3,6-dianhydroiditol (diaminoisoidide, DAII) as well as from 1,4-diaminobutane (DAB), also known as putrescine in nature. Low molecular weight polyamides were obtained by melt polycondensation of the salts based on these monomers or by interfacial polycondensation. In order to increase their molecular weights the polyamide prepolymers were submitted to a solid state polymerization (SSP) process. The chemical structure of the polymers was confirmed by 2D NMR correlation spectra (COSY), heteronuclear multiple-bond correlation spectra (HMBC) and by FT-IR spectroscopy. In the present work, FT-IR and X-ray techniques were used as a tool for the investigation of the crystal structure of the polymers after SSP. The X-ray diffractograms of the polyamides point to crystals containing both 4.10- and DAII.10-based repeat units. Because of the presence of diaminoisoidide residues the synthesized fully renewable products exhibit tunable polarities and melting points. Since most commercial polyamides have a much higher melting point than their end application requires, especially for fiber applications, this simple adaption can result in a significant reduction of energy consumption during processing.

ESR study of gamma irradiated 2-methyl nylon3

Gamma radiation-induced radicals of 2-methyl nylon3 (2mN3) have been investigated by electron spin resonance spectrometry. The type of radicals generated, conversion into other radicalic species and their room temperature stability were evaluated. Two types of radicals have been detected. Two different formation mechanisms have been proposed for each radical. As suggested in literature for commercial polyamides, in our system we also observed two different radicals (R1 and R2). Among these radicals, R1 is expected to convert to R2, which is a chemically favorable process.

Progress in the Area of Degradation and Stabilization of Nylon 66

1. INTRODUCTION The two principal commercial polyamides are poly(hexamethylene adipamide) (nylon 66) and polycaprolactam (nylon 6). They are produced by direct amidation of a diacid with a diamine and ring-opening polymerization of ɛ-caprolactam, respectively. Poly(hexamethylene adipamide) is synthesized by hexamethylene diamine and adipic acid [1]. A stoichiometric balance of amine carboxylic group is readily obtained by the preliminary formation of a 1:1 ammonium salt:

Incorporation of diacids into the polyglycine II structure: model studies.

Aliphatic diacids are often incorporated into polypeptide structures in order to obtain model compounds for hormones, protein turns, etc. They are also fundamental components of many commercial polyamides. On the other hand glycine, the simplest amino acid, shows unique conformational features. In order to better understand the structure of such compounds, we have synthetized and determined the molecular structure of three models represented by the general formula CH3-CH2-CH2-NH-CO-CH2-NH-CO-(CH2)n-2-CO-NH-CH2-CO-NH-CH2-CH2-CH3, with n = 3, 4, or 6. Conformational differences have been found in the dicarboxylic moiety, whereas glycine always has the polyglycine II conformation. The -CO-(CH2)n-2-CO-segment adopts a folded conformation: SS, TGT, and SGTGS for n = 3, 4, and 6, respectively. Molecular packing is always pseudohexagonal and a network of hydrogen bonds oriented in three directions at 120 degrees is formed. The results are of interest in order to provide information about polyamides in which glycine residues are incorporated. Our results confirm the tendency of glycine residues to adopt the polyglycine II conformation in its copolymers with aliphatic compounds.

The photochemistry of commercial polyamides

The photochemistry of commercial polyamides

Phosphorescence from commercial polyolefins and polyamides: Effects of thermal and photochemical oxidation

AbstractA study of the phosphorescence emission from the commercial polyolefins, polyethylene, polypropylene and poly‐4‐methylpentene‐1 and the polyamides, nylon 6/6, 6, 11 and 12 is presented and the origin of the emission discussed. Impurity centres in the polymer are responsible for the emission, being present either as groups directly attached to the polymer backbone or as discrete molecules within the polymer matrix. These impurities can play an important part in the thermal and photochemical oxidation of the polymer. Therefore, changes in the phosphorescence spectra can provide valuable information on the mechanisms of both degradation processes.