Miscible blends of styrene-acrylic acid copolymers with aliphatic,crystalline polyamides

Styrene-acrylic acid copolymers exhibit miscibility with various aliphatic, crystalline polyamides (e.g., nylon 6, 11, and 12) at 20% acrylic acid content in the copolymer. At 8% acrylic acid, phase separation is observed with the crystalline polyamides. At 14% acrylic acid, partial miscibility is observed with each polyamide, resulting in the T_g's of the constituents shifted toward the other constituent. The miscibility of the styrene-acrylic acid copolymers ( > 14 wt % AA) can be ascribed to hydrogen bonding interactions with the polyamides. Styrene-acrylic acid (20% AA) copolymers are miscible with other nylons with alternating amide orientation along the chain (e.g., nylon 6,6 and nylon 6,9). These samples tend to crosslink upon exposure to temperatures above the polyamide melting point unlike the nylon 6, 11, and 12 blends in which branching may only occur. Nylon 11/styrene-acrylic acid blends were chosen for crystallization rate studies. A melting point depression of nylon 11 occurs with addition of the styrene-acrylic acid (20% AA). The Flory-Huggins interaction parameter from the melting point depression is calculated to be -0.27. The crystallization rate of nylon 11 is significantly reduced with the addition of the miscible SAA copolymers (20% AA). The spherulitic growth rate equation predicts this behavior based on a T_g increase with SAA addition.     

Miscibility and Mechanical Properties of Poly(4,4′-diaminobenzanilide- 2,6-naphthalamide)/Nylon 6 Molecular Composites

Poly(4,4′-diaminobenzanilide-2,6-naphthalamide) (DBNA) was synthe-sized by reaction of 2,6-naphthalene dicarboxylic acid with 4,4′-diamino-benzanilide. A new family of molecular composites based on the synthesized DBNA and nylon 6 has been discovered. Exploratory studies were con-ducted with polymers that are soluble in a common organic solvent, N-methylpyrrolidone containing lithium chloride, so that a blend could be prepared by precipitating blended materials in solution into a non-solvent such as water. The miscibility of blends of DBNA with nylon 6 was studied using a differential scanning calorimeter, dynamic mechanical analyser and Fourier transform infrared spectrometer. The blends were found to have at least partial miscibility between DBNA and nylon 6. The morphology and mechanical properties of the molecular composites were evaluated using a scanning electron microscope, transmission electron microscope and tensile tester. The etched specimen showed microfibrils with a diameter of a few nanometres. It has been found that improvement in DBNA dispersion and mechanical properties can be obtained by blending small amounts of DBNA in nylon 6. © of SCI.     

The effect of polyamide end-group configuration on morphology and toughness of blends with maleated elastomers

The effect of polyamide end-group configuration on morphology generation and toughness of blends with maleated elastomers was investigated. Two difunctional polyamides, a copolymer containing 15% nylon 6,6 and an amine enriched nylon 6, were compared to monofunctional nylon 6 materials of equivalent molecular weight and melt viscosity. Difunctional polyamides have some chains with amine groups on both ends capable of reacting with the maleated rubber phase resulting in crosslinking-type effects. The elastomers used included styrene-butadiene-styrene block copolymers with a hydrogenated midblock, SEBS, and versions with X% grafted maleic anhydride, SEBS-g-MA-X%, and a maleated ethylene/propylene random copolymer, EPR-g-MA. Blends based on difunctional polyamides form large, complex rubber particles when compounded in a single-screw extruder; however, by compounding with an appropriate twin-screw extruder, the size and complexity of the particles can be reduced to levels similar to blends with the monofunctional nylon 6 controls. Measurement of the extent of reaction between the amine end groups and the grafted maleic anhydride revealed that a larger number of amine groups are consumed for the difunctional polyamides than for their monofunctional controls. The room-temperature Izod impact strength of blends with the difunctional polyamides is greater than are the corresponding blends with the controls; however, subambient toughness depends mainly on the inherent ductility of the polyamide matrix. © 1996 John Wiley & Sons, Inc.     

Synthesis and properties of novel aromatic polyamides derived from 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy) phenyl]hexafluoropropane and aromatic dicarboxylic acids

A series of polyamides were synthesized by the direct polycondensation of 2,2‐bis[4‐(4‐amino‐2‐fluorophenoxy)phenyl]hexafluoropropane with various commercially available dicarboxylic acids such as terephthalic acid, isophthalic acid, 5‐t‐butyl isophthalic acid, and 2,6‐naphthalene dicarboxylic acid. The synthesized polyamides were soluble in several organic solvents such as N,N‐dimethylformamide, N,N‐dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and chloroform, and they exhibited inherent viscosities of 0.42–0.59 dL/g. The polyamides exhibited weight‐average molecular weights of up to 26,000, which depended on the exact repeating unit structure. These polyamides showed good thermal stability up to 440°C for a 10% weight loss in synthetic air. The polyamides synthesized from 5‐t‐butyl isophthalic acid and isophthalic acid exhibited glass‐transition temperatures of 217 and 185°C, respectively (by differential scanning calorimetry) in nitrogen. The polyamides synthesized from terephthalic acid and 2,6‐naphthalene dicarboxylic acid showed melting temperatures of 319 and 385°C, respectively. The polyamides films were pale yellow, with tensile strengths of up to 82 MPa, moduli of elasticity of up to 2.3 GPa, and elongations at break of up to 9%, which depended on the exact repeating unit structure. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 691–696, 2003     

Preparation and properties of aramids based on naphthalenedicarboxylic acid and their molecular composites with amorphous nylon

Two naphthalene-aromatic polyamides were prepared from 2,6-naphthalenedicarboxylic acid and various aromatic diamines by a modified Higashi phosphorylation reaction. The first polymer, poly(4,4′-diaminobenzanilide-2,6-naphthalamide)^** (DBNA), was synthesized by the reaction of 2,6-naphthalenedicarboxylic acid with 4,4′-diaminobenzanilide. The second polymer, 50/50 copoly(1,4-phenylene/1,4-bis(4′-phenoxy)benzene-2,6-naphthalamide)^*** (PBNA), is a copolymer synthesized using an equimolar ratio of 1,4-phenylene diamine and 1,4-bis(4′-aminophenoxy)benzene. These two polymers have inherent viscosities of 4.17 and 2.32 dL g^-1, respectively, and dissolve in N-methyl-2-pyrrolidone (NMP)containing LiCl. Highstrength films were obtained by casting from these polymer solutions. Blends of DBNA/amorphous nylon and of PBNA/amorphous nylon were prepared by rapidly precipitating the ternary NMP solution into deionized water, and hot-pressing to films at 185°C. The compatibility, morphology, and mechanical properties were investigated by dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and tensile tests. The results revealed that both DBNA and PBNA were partially compatible with amorphous nylon. DBNA formed microfibrils in the amorphous nylon matrix, and its mechanical properties, tensile strength and modulus, improved with increasing DBNA content. PBNA had no reinforcing effect, perhaps because it did not form microfibrils in the amorphous nylon matrix.     

Synthesis of fully bio-based polyamides with tunable properties by employing itaconic acid

A class of bio-based aliphatic polyamides (BDIS) was synthesized by melting copolycondensation from four biomass monomers: originated (SA), itaconic acid (IA), 1, 10-decanediamine (DD), and 1, 4-butanediamine (BD). IA was introduced into the system in order to adjust the chemical structure and the aggregation structures of the BDIS polyamide. Thus, some new polyamides with tunable properties were obtained, such as semi-crystalline polyamide with relatively low melting point, glassy polyamide with excellent toughness, and even rubbery polyamide after hydration. Some of the BDIS can be well melting spinned into fibers with comparable strength as polyamide-6. The BDIS with 100% itaconic acid can even be dissolved in ethanol, which makes it possibly be used by coating and dipping methods. In vitro cytotoxicity tests showed that these polyamides are nontoxic towards mouse fibroblasts and have great potential in biomedical applications.     

Lower purity dimer acid based polyamides used as hot melt adhesives: synthesis and properties

Hot melt polyamides exhibit high adhesive strength. The polyamides synthesized from dimer fatty acids and diamines can present low crystallinity and a broad range of melting temperatures. In this work, polyamides with different compositions of dimer fatty acids, piperazine, ethylenediamine, sebacic acid and stearic acid and different content of secondary diamine (piperazine) and primary diamine (ethylenediamine) were synthesized. Polyamides with higher purity of dimer acids showed greater molecular weight, adhesion performance and a better mechanical resistance evaluated in stress/strain test. Softening point increased with increase in monomers content. By differential scanning calorimetry analysis, it was observed that polyamides with low percentage of monomer content show only one narrow melting peak in 100 °C. The increase in the acids monomer content leads to a larger temperature range of melting peak. The use of dimer fatty acid with a low content of monomers (up to 6%) in the polyamides synthesis promotes the formation of hot melt adhesives with good adhesion performances. The lowest monomer content leads to an increase in molecular weight, viscosity and mechanical properties of polyamide. Increase in the content of primary amines in polyamides increases crystallinity, viscosity and mechanical properties due to the higher number of hydrogen bonds formed by amide groups.     

Hydrogen bonding in polyamide toughened novolac type phenolic resin

The hydrogen bonding, miscibility, and thermal stability of polyamide toughened novolac type phenolic resin were investigated. The intermolecular force of the resin increased with the content of the soft segments of polyamides (nylon 6, nylon 66) that absorb the loads in the network of brittle phenolic resin. IR (IR region) spectra and differential scanning calorimetry results confirmed that the phenolic/polyamide blend was completely miscible. Its thermal degradation temperature was higher than 400°C and increased with the increasing of polyamide content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2283–2289, 1999     

Crystallization behavior of nylon 6 nanocomposites

The crystallization behavior of nylon 6 nanocomposites formed by melt processing was investigated. Nanocomposites were produced by extruding mixtures of organically modified montmorillonite and molten nylon 6 using a twin screw extruder. Isothermal and non-isothermal crystallization studies involving differential scanning calorimetry (DSC) were conducted on samples to understand how organoclay concentration and degree of clay platelet exfoliation influence the kinetics of polyamide crystallization. Very low levels of clay result in dramatic increases in crystallization kinetics relative to extruded pure polyamide. However, increasing the concentration of clay beyond these levels retards the rate of crystallization. For the pure nylon 6, the rate of crystallization decreases with increasing the molecular weight as expected; however, the largest enhancement in crystallization rate was observed for nanocomposites based on high molecular weight polyamides; this is believed to stem from a higher degree of platelet exfoliation in these nanocomposites. Wide angle X-ray diffraction (WAXD) and DSC were further used to characterize the polymer crystalline morphology of injection molded nanocomposites. The outer or skin layer of molded specimens was found to contain only γ-crystals; whereas, the central or core region contains both the α and γ-forms. The presence of clay enhanced the γ-structure in the skin; however, the clay has little effect on crystal structure in the core. Interestingly, higher levels of crystallinity were observed in the skin than in the core for the nanocomposites, while the opposite was true for the pure polyamides. In general, increasing the polymer matrix molecular weight resulted in a lower degree of crystallinity in molded samples as might be expected.     

Relationship between electron sensitivity and chemical structures of polymers as EB resists. III. Electron sensitivity of various polyamides using 3-amino perhydroazepine

Homopolyamides and copolyamides containing a variety of reactive and/or stabilizing groups, such as double bonds, epoxy groups, or naphthalene moieties, were synthesized using 3-amino perhydroazepine (APA) as a diamine monomer. These polymers were evaluated as electron beam (EB) resists, in order to investigate the relationship between EB sensitivity and chemical structure of the polyamides. It was found that polyamides containing double bonds were easily crosslinked by the EB exposure and that the sensitivity of a polyamide containing double bonds in the side chain was higher than that of a polyamide containing double bonds in the main chain. The sensitivity of a polyamide containing epoxy groups was lower than that of the above. Copolymer from APA, 77 mol % of trans-3-hexenedioyl chloride (HC) and 23 mol % of 2,6-naphthalenedioyl chloride (NC) had the same EB sensitivity as that of the homopolymer from APA and HC. The polyamides had excellent dry etching durability and were adaptable to EB lithography.     

The nucleation effect of linear polyethylene lamellae over the crystallization of branched polyethylene

Summary The polyamides with aromatic rings in the main chain were synthesized by the solution polymerization of 4,4-diphenylmethane diisocyanate and aliphatic dicarboxylic acid in the presence of catalyst. The thermal properties and the miscibility behaviours with polyamide-6,6 of these aromatic polyamides were studied. The aromatic polyamides synthesized with one kind of dicarboxylic acid had typical thermal properties of crystalline polymers, whereas those synthesized with the mixtures of dicarboxylic acids were not easily crystallized. The observed miscibility behaviours showed some differences from those predicted by binary interaction model.     

Structure–property relationship in polybutadiene–polyamide multiblock copolymers

Two kinds of aromatic–aliphatic polyamide oligomers were newly prepared by the reactant pairs of 3,4′-oxydianiline–adipic acid and 3,4′-oxydianiline–azelaic acid. These oligomers were then condensed separately with α, ω-polybutadienedicarboxylic acid giving two series of polybutadiene–polyamide multiblock copolymers. Properties of four series of polybutadiene–polyamide multiblock copolymers, whose polyamide blocks consisted of not only newly prepared polyamides but also previously synthesized aromatic polyamides derived from 4,4′-oxydianiline–isophthalic acid and 3,4′-oxydianiline–isophthalic acid, were investigated on the view point of structure-property relationship. A larger extent of the T_g depression of polybutadiene phase, and higher tensile strength and modulus were observed in the block copolymers having aromatic polyamides compared with those having aliphatic ones.     

Recognition by nonaromatic and stereochemical subunit-containing polyamides of the four Watson-Crick base pairs in the DNA minor groove

In order to develop an optimal subunit as a T‐recognition element in hairpin polyamides, 15 novel chirality‐modified polyamides containing (R)‐α,β‐diaminopropionic acid (^Rβ), (S)‐α,β‐diaminopropionic acid (^Sβ), (1R,3S)‐3‐aminocyclopentanecarboxylic acid (^RSCp), (1S,3R)‐3‐amino‐cyclopentanecarboxylic acid (^RSCp), (1R,3R)‐3‐aminocyclopentanecarboxylic acid (^RRCp) and (1S,3S)‐3‐amino‐cyclopentanecarboxylic acid (^SSCp) residues were synthesized. Their binding characteristics to DNA sequences 5′‐TGC N CAT‐3′/3′‐ACG N′ GTA‐5′ ( N?N′ =A ? T, T ? A, G ? C and C ? G) were systemically studied by surface plasmon resonance (SPR) and molecular simulation (MSim) techniques. SPR showed that polyamide 4 , AcIm‐^Sβ‐ImPy‐γ‐ImPy‐β‐Py‐βDp (β/^Sβ pair), bound to a DNA sequence containing a core binding site of 5′‐TGC A CAT‐3′ with a dissociation equilibrium constant (K_D) of 4.5×10^?8 m. This was a tenfold improvement in specificity over 5′‐TGCTCAT‐3′ (K_D=4.5×10^?7 M ). MSim studies supported the SPR results. More importantly, for the first time, we found that chiral 3‐aminocyclopentanecarboxylic acids in polyamides can be employed as base readers with only a small decrease in binding affinity to DNA. In particular, SPR showed that polyamide 9 (^RRCp/β pair) had a 15‐fold binding preference for 5′‐TGCTCAT‐3′ over 5′‐TGCACAT‐3′. A large difference in standard free energy change for A ? T over T ? A was determined (ΔΔG^o=5.9 kJ mol^?1), as was a twofold decrease in interaction energy by MSim. Moreover, a 1:1 stoichiometry ( 9 to 5′‐TGC T CAT‐3′/3′‐ACG A GTA‐5′) was shown by MSim to be optimal for the chiral five‐membered cycle to fit the minor groove. Collectively, the study suggests that the (S)‐α‐amino‐β‐aminopropionic acid and (1R,3R)‐3‐aminocyclopentanecarboxylic acid can serve as a T‐recognition element, and the stereochemistry and the nature of these subunits significantly influence binding properties in these recognition events. Subunit (1R,3R)‐3‐aminocyclopentanecarboxylic acid broadens our scope to design novel polyamides.     

环氧树脂/马来海松酸酐聚酰胺的固化反应及产物性能研究

以马来海松酸酐为原料,通过与多元胺(二乙烯三胺、三乙烯四胺、四乙烯五胺)进行酰胺化反应,合成了3种环氧树脂固化剂马来海松酸酐聚酰胺,分别命名为聚酰胺样品Ⅰ、聚酰胺样品Ⅱ、聚酰胺样品Ⅲ。利用傅里叶红外光谱仪(FT-IR)、热重分析仪(DTA)、拉力机等分析测试手段,对环氧树脂/马来海松酸酐聚酰胺体系固化产物的特征性能进行了表征。结果表明,环氧树脂分别与3种聚酰胺样品按理论质量配比100:51、100:45、100:45混匀后,在室温放置6 h后再于80℃固化4 h,可完全固化,环氧树脂/聚酰胺样品Ⅰ剪切强度可达21.6 MPa,3种固化体系热分解温度均大于300℃,可望在对剪切强度、耐热等级要求较高的固化剂领域得到广泛应用。     

Interfacial interaction and mechanical properties of nylon 6-potassium titanate composites prepared by in-situ polymerization

A new method was proposed for the synthesis of nylon 6-potassium titanate composites with high strength and high modulus. Dispersion quality of potassium titanate whiskers in the polyamide matrix and the degree of interfacial adhesion between polyamide and whiskers are the key points with ϵ-caproamide and potassium titanate whiskers, which were modified by an alkylsilane coupling agent with n-aminocapric acid as initiator through in-situ polymerization. The contact angle test showed that the surface energy of modified whiskers is similar to nylon 6's, while that of the unmodified ones was much higher than nylon 6's. These results suggest that the modified whiskers would disperse homogeneously in the nylon 6 matrix. Scanning electronic microscope (SEM) results fortified the above hypothesis. According to infrared (IR) spectra, the sample of whiskers that were separated from the modified composite by formic acid have the characteristic peak of nylon 6's; and the whiskers that were separated from unmodified composite do not have them, which suggested that there are chemical bonds between modified whiskers and nylon 6 matrix, and the whiskers served as chemical cross-link points in the composite. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2317–2322, 1997     

An investigation of thermal and mechanical properties of synthesised polyamide-6/γ-alumina composites

Abstract

Polyamide based composites were formed by melt blending of polyamide 6 (PA6) with a γ) -alumina powder toughened with ethylene–octene copolymer grafted by maleic anhydride (EOC-g-MAH) and also without EOC in a corotating twin screw extruder. Mechanical properties, morphological structure and thermal stability of toughened PA6 (PA6-g-EOC) and PA6-g-EOC/alumina composites were investigated in this study.To study the effect of powder loading of γ-alumina on the mechanical properties of the composites such as tensile strength, modulus of elasticity, break point and impact strength, varied amounts of 5, 10 and 15?wt-% were deployed. The toughened PA6–γ-alumina composites, i.e. blended by EOC-g-MAH, revealed higher impact strength and more toughness compared to that of the PA6–γ-alumina composites without EOC-g-MAH. Morphology of the composites was investigated by scanning electron microscopy (SEM) from the as moulded specimens. Micrographs showed a fine dispersion of γ-alumina particles in polyamide matrix due to appropriate mixing. Furthermore, thermal stability and degradation characteristics of the toughened PA6–γ-alumina composites were measured by thermogravimetric analysis. The addition of γ-alumina into the polyamide matrix showed an increase in thermal resistance so that thermal stability was increased by a rise in the powder loading.     

Polyarylate/polyamide 6 blends: A calorimetric study

Summary A calorimetric study has been done of the miscibility of blends composed of polyarylate (PAr) and poly(-caprolactam) (polyamide 6, nylon 6). The thermal transitions of blends subjected to two different thermal treatments have been determined. Two glass transitions have been observed in the blends irrespective of the thermal history. These glass transitions indicate the existence of two amorphous phases in the blends, a practically pure nylon phase and a mixed PAr/nylon 6 phase. The variation of the melting temperature of nylon with the blend composition is in good agreement with the existence of phase separation in the blends. However, the melting heat shows a slightly positive deviation from linearity when it is represented against the blend composition.     

Synthesis and properties of novel soluble aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups

Three diamine monomers containing pyridine groups were prepared via the modified Chichibabin reaction of aromatic aldehydes with 4′-nitroacetophenone, followed by reduction with hydrazine hydrate in the presence of Pd/C. Novel aromatic polyamides containing 4-aryl-2,6-diphenylpyridine moieties and pendant fluorinated phenoxy groups were synthesized from these diamines and two fluorinated isophthaloyl dichlorides by the low temperature solution polycondensation in N,N-dimethylacetamide (DMAc). All the polymers are amorphous and readily soluble in strong polar organic solvents such as DMAc, N-methyl-2-pyrrolidinone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO) at room temperature. The resulting polymers showed glass transition temperatures between 270 and 314 °C and 5 % weight loss temperatures ranging from 442 °C to 475 °C, and char yields at 800 °C higher than 53 % in nitrogen. These polyamides could be cast into transparent, flexible and strong films from DMAc solution with tensile strengths of 72.5–87.3 MPa, tensile moduli of 2.35–2.87 GPa, and elongations at break of 5.3–9.5 %. The polyamide films exhibited low dielectric constants of 3.21–3.54 (1 MHz), low water uptakes in the range of 1.17–1.38 %, and high transparency with an ultraviolet-visible absorption cut-off wavelength in the 380–391 nm range.     

Acrylic acid containing copolymers as reactive compatibilitzers for toughening nylon 6

Nylon 6 has been toughened by rubber particles that were dispersed within the matrix via additives that physically interact with the elastomer phase but chemically react with the polyamide phase. To disperse a core-shell impact modifier having a poly(methyl methacrylate) or PMMA shell, most of the work presented is based on the use of a styrene/acrylic acid copolymer containing 8 wt% acrylic acid, SAA8. SAA8 is miscible with PMMA and should located in the PMMA grafted chains of the impact modifier while chemically reacting with the nylon 6 matrix; hence, it should aid in both the dispersal and strenghtening the modifier-matrix interface. Microscopy and mechnical properties confirm that SAA8 does function in this way but less effectively than styrene/maleic anhydride copolymers, which are also miscible with PMMA but evidently react more effectively with the polyamides. The use of ethylene/acrylic acid copolymer for dispersal of the coreshell impact modifier and a styrene/ethylene-butene/styrene block copolymer in nylon 6 was also briefly considered. Low-temperature toughness of the blends proved to be a much more critical test of the effectiveness of such additives than room temperature impact strenght.     

Crystallization and dissolution behaviour of polyamide 6–water systems under pressure

The solubility of polyamide 6 (PA6) in water under pressure has been reported recently and is explored further here using a pressurized differential scanning calorimeter equipped with a pressure regulator, enabling operation at constant pressure. The optimum parameters for solubility (temperature, pressure, concentration) were determined. Crystallization and melting temperature depressions of a maximum of 60 °C were found. The minimum water concentration needed to reach the maximum temperature depression was found to be approximately 30 mass%. Because in such a case the end melting/dissolution temperature for PA6 in water is approximately 165 °C, the pressure level has to be high enough to prevent water from evaporating, i.e. above 8 bar (0.8 MPa). The expected industrial uses of the water solubility of polyamides under pressure are to ease the processing of polyamides by extrusion; to make polyamide composites; to disperse temperature‐sensitive fillers in polyamides; and, in general, to realize ‘green’ routes for the formation of polyamides. Copyright © 2010 Society of Chemical Industry