Synthesis and properties of thermostable naphthalate-containing copoly(amide–imide)s

Thermostable naphthalate-containing copoly(amide-imide)s with inherent viscosity of 0.53–0.96 dL/g were synthesized by reacting diacid-terminated naphthalate monomers with various diisocyanate-terminated polyimide prepolymers. The poly-imide prepolymers were prepared by using 4,4′-diphenylmethane diisocyanate to react with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, or 3,3′,4,4′-sulfonyl diphthalic anhydride using a direct one-pot method to improve their solubility without sacrificing their thermal properties. The copolymers, except the B-2 and P-2 series, can be dissolved in N,N-dimethylacetamide and 5% lithium chloride or dimethyl sulfoxide at high temperature but are not soluble in pyridine. The solubility of the copolymers is related to their chemical and crystalline structures. Those copolymers with sulfonyl or amorphous structures display good solubility. All the naphthalate-containing copoly(amide-imide)s have glass transition temperatures and melting points in the range of 223–312°C and 348–366°C, respectively, and show a 10% weight-loss temperature of 485–549°C in air and 465–564°C in a nitrogen atmosphere. The tensile strength, elongation at break, and initial modulus of polymer films range from 25–74 MPa, 4–9%, and 0.74–1.60 GPa, respectively. From the X-ray diffraction studies, copolymers of B-2, P-2, and D-2 with symmetrical 2,6-naphthalate amide structure are crystalline, but the others are amorphous. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1581–1593, 1997     

High-resolution thermogravimetry of liquid crystalline copoly(p-oxybenzoate–ethylene terephthalate–m-oxybenzoate)

Thermotropic liquid crystalline terpolymers consisting of three units of p-oxybenzoate (B), ethylene terephthalate (E), and m-oxybenzoate (M), were investigated through high-resolution thermogravimetry to evaluate their stability and kinetic parameters of thermal degradation in nitrogen and air. Overall activation energy data of the first major decomposition was calculated through three calculating methods. Thermal degradation occurs in three major steps in both nitrogen and air. Three kinds of degradation temperatures (T_d, T_m1, T_m2) are slightly higher and the first maximum weight-loss rates are slightly lower in nitrogen than in air, suggesting a higher thermostability in nitrogen. The thermal degradation temperatures range from 450 to 457°C in nitrogen and 441 to 447°C in air and increase with increasing B-unit content at a fixed M-unit content of 5 mol %. The temperatures at the first maximum weight loss rate range from 452 to 466°C in nitrogen and 444 to 449°C in air and increase slightly with an increase in B-unit content. The first and second maximum weight-loss rates are maintained at almost 9.2–10.8 and 4.0–6.1%/min in nitrogen (11.2–12.0 and 3.9–4.2%/min in air) and vary slightly with copolymer composition. The residues after the first major step of degradation are predicted on the basis of the complete exclusion of ester and ethylene groups and hydrogen atoms and compared with those observed experimentally. The char yields at 500°C in both nitrogen and air are larger than 42.6 wt % and increase with increasing B-unit content. However, the char yields at 800°C in nitrogen and air are different. The activation energy and ln(pre-exponential factor) for the first major decomposition are slightly higher in nitrogen than in air and increase with an increase in B-unit content at a given M-unit content of 5 mol %. There is no regular variation in the decomposition order with the variation of copolymer composition and testing atmosphere. The activation energy, decomposition order, and ln(pre-exponential factor) of the thermal degradation for the terpolymers are located in the ranges of 212–263 kJ mol⁻¹, 2.4–3.5, 33–41 min⁻¹, respectively. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2911–2919, 1999     

Synthesis of copoly(ethylene terephthalate /imide)s and crystallization kinetics

Copoly(ehtylene terephthalate/imide)s (PETI) were prepared by melt polycodensation of bis(2-hydroxyethyl)terephthalate (BHET) and imide containing comonomer, 4,4′-bis[(4-carbo-2-hydroxyethoxy)phthalimido]diphenylmethane (BHEI) with Sb₂O₃ as catalyst at 280°C under vacuum (～ 1 mm Hg). The change of T_m with an increase of the BHEI repeat unit in the PETI copolymer was analyzed by the Flory equation. On isothermal crystallization, a longer induction time and a lower activation energy than for the PET homopolymer were observed with an increasing amount of BHEI repeat unit. The Avrami exponent, n, increased from 1.5 to 2.3 as the content of BHEI or crystallization temperature was increased. The Avrami rate constant K decreased with the increase of the BHEL unit. On nonisothermal crystallization, the Ozawa equation and Lawton plot were used to investigate the effect of BHEI units on the crystallization kinetics of PETI copolymers. From the change of the cooling crystallization function and the result of the Lawton plot, it was found that the BHEI unit effectively decreases the rate of crystallization.     

Synthesis of thermostable nomex copoly(amide–imide) and their properties

Thermostable Nomex copoly(amide–imide)s with inherent viscosity of 0.72–1.31 dL/g were synthesized by reacting diacid-terminated Nomex prepolymer with various diisocyanate-terminated polyimide prepolymers. The polyimide prepolymer was prepared by using 4,4′-diphenylmethane diisocyanate to react with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, or 3,3′,4,4′-sulfonyl diphthalic anhydride using a direct one pot method in order to improve their solubility. The copolymers, except B-1, P-1, P-2, D-1, and D-2, could be dissolved in N, N-dimethylacetamide +5% lithium chloride at room temperature or dimethyl sulfoxide at high temperature but were not soluble in N,N-dimethylformamide or pyridine. The solubility is considered to be related to their crystallinity. Those copolymers with crystalline structure displayed poor solubility. All the Nomex copoly(amide–imide)s had glass transition temperatures in the range of 223–352°C and showed a 10% weight loss temperature of 438–574°C in air and 441–585°C in nitrogen atmosphere. The tensile strength, elongation at break, and initial modulus of polymer films ranged 63–118 MPa, 4–9% and 1.67–2.53 GPa, respectively. From the X-ray diffraction studies, copolymers of B-1, P-1, P-2, D-1, and D-2 with high content of PmIA showed a crystalline structure, but the others only displayed an amorphous morphology. © 1996 John Wiley amp; Sons, Inc.     

Synthesis and characterization of block copoly(urethane–imide)

A newly synthetic method has been developed for the preparation of block copoly(urethaneimide) (PUI). The copolymer was yielded from the direct reaction of the prepolyurethane terminated with isocyanate and the prepolyimide terminated with anhydride. The latter is prepared by reacting an excess amount of pyromellic dianhydride (PMDA) with bis [4-(3-aminophenoxy)phenyl] sulfone (BAPS) in one-step polymerization. The structure was confirmed by infrared (IR) spectra. Other characterizations were evaluated. Among them were solubility, viscosity, mechanical properties, and thermal properties. © 1996 John Wiley & Sons, Inc.     

Effect of rod-like imide unit on crystallization of copoly(ethylene terephthalate-imide)

The effect of the imide unit on the isothermal and non-isothermal crystallization, kinetics crystallization of a new family of copoly(ethylene terephthalate-imides) (called copolyesterimides or PETIs) was investigated using differential scanning calorimetry. With a combined Avrami and Ozawa equation, one can describe the non-isothermal crystallization process of copolyesterimides, and the results show the same tendency as that in the isothermal crystallization process. These studies show that the processes of crystal nucleation and growth result in mainly three-dimensional growth with a thermal nucleation. In both isothermal and non-isothermal crystallization processes, the crystallization rate of PETIs, with imide content below 0.5%, is higher than that of neat PET, while PETI-3 (0.3 mol% imide) has the highest crystallization rate. This rate is significantly enhanced over PET homopolymer. It is proposed that imide units precipitate from the melt and act as nucleating agents during the crystallization process of these novel copolyesterimides.     

Thermal behavior and tensile properties of poly(ethylene terephthalate‐co‐ethylene isophthalate)

Poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) homopolymers were synthesized by the two‐step melt polycondensation process of ethylene glycol (EG) with dimethyl terephthalate (DMT) and/or dimethyl isophthalate (DMI), respectively. Nine copolymers of the above three monomers were also synthesized by varying the mole percent of DMI with respect to DMT in the initial monomer feed. The thermal behavior was investigated over the entire range of copolymer composition by differential scanning calorimetry (DSC). The glass transition (T_g), cold crystallization (T_cc), melting (T_m), and crystallization (T_c) temperatures have been determined. Also, the gradually increasing proportion of ethyleno‐isophthalate units in the virgin PET drastically differentiated the tensile mechanical properties, which were determined, and the results are discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 200–207, 2000     

Crystallization kinetics of new copoly(ethylene terephthalate-imide)s

Crystallization kinetics of copoly(ethyleneterephthalate-imide)s (PETIs) of various imide contents were studied by the DSC technique. The results of isothermal and nonisothermal crystallization kinetics studies showed a consistent trend in that the crystallization of all copolyesterimides comprised a primary stage and secondary stage, and that the crystallization mechanism was a three-dimensional growth with athermal nucleation. The crystallization rate of PETIs first increased and then decreased as the content of imide units in the copolyesterimides increased. This indicates that the imide units in the copolymer decreased the chain-packing regularity of poly(ethylene terephthalate) (PET) and the same units also enhanced the copolymer chain rigidity. The copolyesterimide with 0.2 mol% imide unit content showed a dramatic increase of the crystallization rate, and exhibited the highest crystallization rate of all the studied compositions. Studies of isothermal and nonisothermal crystallization kinetics, showed that small amounts of imide units in the the backbone act as nucleating agents during the crystallization process of copolyesterimides.     

Poly(thioether imide)s via chloro-displacement polymerization

Summary Thioether containing polyimides were prepared by displacement of chlorine groups from substituted imides by aromatic and aliphatic sulfur nucleophiles. The allaromatic monomers and polymers had poor solubility which led to precipitation during synthesis and low molecular weight polymers. However, these polymers were thermally stable up to 400 °C and had T_g's ranging from 212 °C to 233 °C. Poly(thioether imide)s prepared from 1,3-propanedithiol and 2-mercaptoethyl sulfide had good solubility but lower thermal stability, showing TGA loss onset temperatures of 297 °C and 298 °C, respectively.     

Synthesis of polyurethane–imide (PU–imide) copolymers with different dianhydrides and their properties

This study reports the synthesis of polyurethane–imide (PU–imide) copolymers using 4,4′-diphenylmethane diisocyanate (MDI) polytetramethylene glycols (PTMGs) and different aromatic dianhydrides. Differential scanning calorimetry (DSC) results indicate that PU–imide copolymers had two phase structures containing four transition temperatures (T_gs, T_ms, T_gh and T_mh). However, only PU–imide copolymers were formed by soft PTMG(2000) segments possessing a T_ms (melting point of soft segment). When different aromatic dianhydrides were introduced into the backbone chain of the polyurethane, although the T_gs (glass transition temperature of the soft segment) of some of PU–imide copolymers did not change, the copolymers with long soft segments had low T_gs values. The T_gh (glass transition temperature of hard segment) values of PU–imide copolymers were higher than that of polyurethane (PU). In addition, the high hard segment content of PU–imide copolymer series also had an obvious T_mh (melting point of hard segment). According to thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTGA), the PU–imide copolymers had at least two stages of degradation. Although the T_di (initial temperature of degradation) depended on the hard segment content and the composition of hard segment, the different soft segment lengths did not obviously influence the T_di. However, PU–imide copolymers with a longer soft segment had a higher thermal stability in the degradation temperature range of middle weight loss (about T_d 5%–50%). However, beyond T_d 50% (50% weight loss at temperature of degradation), the temperature of degradation of PU–imide copolymers increased with increasing hard segment content. Mechanical properties revealed that the modulus and tensile strength of PU–imide copolymers surpassed those of PU. Wide angle X-ray diffraction patterns demonstrated that PU–imide copolymers are crystallizable. © 1999 Society of Chemical Industry     

Morphological changes of poly(ethylene terephthalate‐co‐isophthalate) during solid state polymerization

Poly(ethylene terephthalate‐co‐isophthalate) (PETI) prepolymer was submitted to solid state polymerization (SSP) at 184–230°C in a fixed bed reactor, to study the evolution of morphological changes during the process. Short reaction times were selected to investigate crystallization phenomena during nonisothermal (heating) and isothermal SSP phases. More specifically, multiple PETI melting behavior was observed and attributed to secondary crystallization, the rate of which increased significantly with SSP temperature. Reaction time was also found to exert a positive effect on solid‐phase perfection of secondary crystals, leading at each temperature to melting points close to the value of bottle‐grade poly(ethylene terephthalate). Finally, the mass fraction crystallinity of the SSP grades was found to comply with the crystal morphology encountered. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Poly(amide imide)s and poly(amide imide) composite membranes by interfacial polymerization

Novel amic acid diamines (AADs) (2‐carboxyterephthalamido‐bis(alkyl or aryl amine)s, H₂N? X? NH(O?)C? C₆H₃(COOH)? C(?O)NH? X? NH₂, where X is were synthesized by reacting trimellitic anhydride chloride with aromatic or aliphatic diamines in dimethylformamide at 5–10 °C. Poly(amide imide)s (PAIs) with an amide to imide ratio of three in the polymer chains were prepared by interfacial polycondensation of the AADs in aqueous alkaline solution with isophthaloyl chloride or terephthaloyl chloride in dichloromethane at ambient temperature to form poly(amide amic acid)s, followed by their subsequent thermal cycloimidization. All of the PAIs were soluble in polar aprotic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide and N‐methylpyrrolidone, and have inherent viscosities in the range 0.15–0.48 dL g^?1. The polymers were characterized by IR and NMR spectroscopy, TGA and DSC techniques. The PAIs have initial decomposition temperatures in the range 250–460 °C in air, and glass transition temperatures of 128–320 °C, depending upon the structures of the monomers. Composite membranes containing a poly(amide amic acid) and poly(amide imide) barrier layer on the top of a porous polyethersulfone support were prepared by in situ interfacial polymerization of the AADs in aqueous alkaline solution with trimesoyl chloride in hexane, and subsequent curing. The performances of these membranes were evaluated by using aqueous feed solutions containing 2000 ppm NaCl, Na₂SO₄ or CaCl₂. Copyright © 2006 Society of Chemical Industry     

Melt rheological properties of polypropylene/SEBS (styrene–ethylene butylene–styrene block copolymer) blends

Study of melt rheological properties of the blends of polypropylene (PP) with styrene–ethylene butylene–styrene block copolymer (SEBS), at blending ratios 5–20% SEBS, is reported. Results illustrate the effects of (i) blend composition and (ii) shear rate or shear stress on melt viscosity and melt elasticity and the extrudate distortion. In general, blending of PP with SEBS results in a decrease of its melt viscosity, processing temperatures, and the tendency of extrudate distortion. However, the properties depend on blending ratio. A blending ratio around 5–10% SEBS seems optimum from the point of view of desirable improvement in processability behavior.     

Synthesis and thermal properties of poly(urethane‐imide)

The synthesis and thermal properties of thermoplastic poly(urethane‐imide) (PUI) resins were studied. Model reaction studies on the reactions of 4,4′‐diphenylcarbamatodiphenylmethane and 4,4′‐diisocyanatodiphenylmethane with phthalic anhydride were performed. We found that the reaction of anhydrides with urethane groups could take place under certain reaction conditions. According to the model reaction studies, N‐2‐methyl‐pyrrolidone was employed as a solvent, and no catalyst was used in the polymerization. To restrain the side reaction of anhydrides with urethane groups, we adopted a two‐step chain‐extending procedure in a chain‐extending reaction. The inherent viscosity of PUI was 0.83–0.99 dL/g. The prepared polymers not only exhibited improved solubility in organic solvents but also formed flexible films. Thermogravimetric analysis showed that PUI exhibited a two‐step thermal weight‐loss pattern. The first step of the thermal degradation of PUI was attributed to the thermooxidizing cleavage of weak and labile linkage, such as urethane groups, isopropylidene, and methylene, except for imide rings. The polymer inherent viscosity decreased sharply during the first step of thermal degradation. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 773–781, 2001     

Copolyester studies. VI. Melt spinning and mechanical properties of tetramethylene terephthalate–poly(tetramethylene oxide) random block copolymers

Fibers were prepared from tetramethylene terephthalate–polytetrahydrofuran (PTHF) random block copolymers, containing the latter in the range of molecular weights 1000–5000 with up to 30% by weight incorporation, using a conventional melt spinning technique. The spinnability of the copolymer and the mechanical properties of these undrawn fibers were evaluated. The changes in mechanical properties brought about by the incorporation of PTHF groups in 4GT units were related to the PTHF block size and content in the copolymer. X-ray diffraction data are also discussed briefly in terms of the structural differences.     

Blends of poly(vinyl butyral‐co‐vinyl alcohol) and poly(ethylene terephthalate‐co‐ethylene naphthalate): thermal,mechanical, and morphological properties

The miscibility behavior and morphology of a series of poly(vinyl butyral‐co‐vinyl alcohol) (PVBA) copolymers containing 29, 52, 76, and 88 mol % of vinyl alcohol units with poly(ethylene terephthalate‐co‐ethylene naphthalate) (PETN) was investigated by DSC and SEM. Blends of the PETN with PVBA were prepared by coprecipitation from a chloroform/o‐chlorophenol (20/80 wt %) mixture solvent. It was found that PVBAs with different vinyl alcohol content will form an immiscible phase with the amorphous PETN in the solution‐cast films. Also, PETN and PVBA with 29 mol % vinyl alcohol (PVBA‐29) are not miscible within the whole composition range. The glass‐transition temperatures of the blends were higher than those of the two‐component polymers. The values of the tensile properties of the blend films were also better than those of the original copolymer films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2746–2751, 2001     

Synthesis, characterization and thermal properties of soluble aromatic poly(amide imide)s

Novel diamines such as N,N′-bis(aminoaryl)terephthalamido-2-carboxylic acids (BATCA), which contain primary amine, amide and carboxylic acid groups and are soluble in dilute aqueous NaOH solution, were synthesized by reacting aromatic diamines with trimellitic anhydride chloride in dimethylformamide. Poly(amide imide)s containing 3:1 ratio of amide:imide groups in the polymer chain were prepared by low temperature solution polymerization of BATCAs with isophthaloyl chloride or terephthaloyl chloride in dimethylformamide at 5-10 °C to form poly(amide amic acid)s, and followed by treating with a mixture of triethylamine and acetic anhydride. The PAIs were soluble in polar aprotic solvents like dimethylformamide, dimethylacetamide, dimethylsulphoxide and N-methylpyrrolidone, and have inherent viscosities in the range of 0.30-0.66 dL/g. The PAIs were characterized by IR, ¹H NMR and ¹³C NMR techniques. Thermogravimetric analysis (TGA) has shown that the initial decomposition temperatures of the polymers are in the range of 250-440 °C, depending upon the structures of diamine and diacid chloride. The glass transition temperatures of the PAIs are in the range of 128-320 °C. The IDT and T_g values of the polymers containing terephthaloyl unit are higher by about 20-40 °C than those of the polymers with isophthaloyl unit. BATCA could be utilized for the preparation of thin film composite membranes having PAA/PAI barrier layer on PES by in situ interfacial polymerization with IPC/TPC/TMC.     

Antielectrostatic poly(ether ester) block copolymer of poly(ethylene terephthalate‐co‐isophthalate)–poly(ethylene glycol)

Poly(ethylene terephthalate) (PET) fiber has a low moisture regain, which allows it to easily gather static charges, and many investigations have been carried out on this problem. In this study, a series of poly(ethylene terephthalate‐co‐isophthalate) (PEIT)–poly(ethylene glycol) (PEG) block copolymers were prepared by the incorporation of isophthalic acid (IPA) during esterification and PEG during condensation. PEG afforded PET with an increased moisture affinity, which in turn, promoted the leakage of static charges. However, PET also then became easier to crystallize, even at room temperature, which led to decreased antistatic properties and increased manufacturing inconveniences. IPA was, therefore, used to reduce the crystallinity of the copolymers and, at the same time, make their crystal structure looser for increased water absorption. Moreover, PET fibers with incorporated IPA and PEG showed good dyeability. In this article, the structural characterization of the copolymers and antistatic and mechanical properties of the resulting fibers are discussed. At 4 wt % IPA, the fiber containing 1 mol % PEG with a molecular weight of 1000 considerably improved antistatic properties and other properties. In addition, the use of PEIT–PEG as an antistatic agent blended with PET or modified PET fibers also benefitted the antistatic properties. Moreover, PEIT–PEG could be used with another antistatic agent to produce fibers with a low volume resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1696–1701, 2003