Synthesis and nonisothermal crystallization kinetics of thermoplastic polyamide-6 elastomers

Three kinds of thermoplastic polyamide-6 elastomers (TPAEs) with varying polytetramethyleneglycol (PTMG) contents of 10, 20, and 30 wt % were prepared via a one-pot polymerization synthetic route and named as TPAE1, TPAE2, and TPAE3, respectively. First, their structures were investigated by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, scanning electron microscope, and X-ray diffraction. The obtained results confirmed that targeted TPAEs were successfully synthesized and the unit cell of crystallization in TPAEs with α form was confirmed. Subsequently, the thermal properties of prepared TPAEs were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) measurements, respectively. DSC curves showed that melting points of synthesized TPAEs were in the range of 209.2–215.9 °C. Moreover, TGA results showed TPAEs possess good thermal stability and cannot be decomposed under 300 °C. Additionally, the modified Avrami's equation, Ozawa's theory, and Mo's method were employed to investigate the nonisothermal crystallization kinetics of prepared TPAEs. It is found that the Mo's method exhibited great advantages in treating the nonisothermal crystallization kinetics of prepared TPAEs. Meanwhile, the crystallization kinetics and halftime are influenced by the contents of PTMG and follows a nonlinear fashion in agreement with the trend inactivation energies calculated by the Kissinger method. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47388.     

Structure–property relations of nylon‐6 and polytetramethylene glycol based multiblock copolymers with microphase separation prepared through reactive processing

A series of poly(urethane‐urea‐amide) thermoplastic elastomers (PUUAs) based on polytetrahydrofuran (polytetramethylene glycol, PTMG), nylon‐6 and 4,4′‐diphenylmethane diisocyanate were synthesized through reactive processing. This method solved the incompatibility of nylon‐6 and PTMG, and these model elastomers were used to gain insight into the structure–property relations of block polymers. The target products were solvent resistant, transparent and melting‐processable. Fourier transform infrared spectroscopy, XRD, DSC, TEM, dynamic mechanical analysis, tensile testing and TGA were used to study the structure, crystallization, morphology, mechanical properties and thermostability of the PUUAs. The Fourier transform infrared results proved the successful preparation of PUUAs from nylon‐6 and PTMG. TEM examination showed that all samples exhibit microphase separated morphology with the nylon‐6 domain dispersed in the PTMG phase. The results of tensile testing indicated that the elastomers exhibit excellent mechanical properties with stress at break and strain at break exceeding 40 MPa and 600% respectively. The TGA results implied that the PUUAs can be fabricated by transitional processing at proper temperature without any thermodegradation. These favorable features were related to the microphase separated structure of the PUUAs. © 2016 Society of Chemical Industry     

GAP/PET嵌段型热塑性聚氨酯弹性体的低温力学性能

为改善聚叠氮缩水甘油醚(GAP)基黏合剂的低温力学性能,以GAP和环氧乙烷-四氢呋喃共聚醚(PET)为软段,甲苯-2,4-二异氰酸酯(TDI)偶联的丁二醇为硬段,通过扩链聚合反应合成GAP/PET嵌段型热塑性聚氨酯弹性体;分别采用红外光谱(FT-IR)、核磁共振(NMR)、差示扫描量热分析(DSC)、动态热机械分析(DMA)、热重分析(TGA)和万能材料试验机对其化学结构、玻璃化转变温度、热稳定性和低温拉伸性能进行表征。结果表明,随着PET含量的提高,GAP/PET嵌段型热塑性聚氨酯的T_g明显降低,当PET与GAP摩尔比为1∶1时,GAP/PET嵌段型热塑性聚氨酯的T_g为-37.7℃,在-40℃低温环境发生韧性断裂,断裂强度为25.78MPa,断裂伸长率为379.4%,具有优异的低温力学性能;同时TGA试验表明GAP/PET嵌段型热塑性聚氨酯T_d>220℃,热稳定性好。     

Polyether–polyimide thermoplastic elastomers. I. Synthesis and properties

A series of polyether–polyimides based on polycondensation of poly(tetramethylene oxide) glycol di-p-aminobenzoate with different molecular weights (650, 1000, 2000) and benzenetetracarboxylic acid dianhydride (BTDA) or 3,3′,4,4′-benzenetetracarboxylic acid anhydride (BPTDA) was synthesized. Infrared spectroscopy (IR), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and stress–strain tests were used to follow the imidization process and to study the structure–property relations of this family of polymers. FTIR data showed that the imidization was completed after 6 h at 140°C, which is a much lower temperature than that required for polyimides synthesized from low molecular weight diamines. DSC and DMA results indicated that the block copolymer exhibited a well-phase-separated structure and had a broad rubbery plateau from about ?70°C to 260°C, which varied with dianhydride type and hard-segment content. The BTDA series had enhanced mechanical properties compared to the BPTDA series. The excellent tensile properties of the polyether–polyimides suggest that they could be potentially used as heat-resistant thermoplastic elastomers.     

Aqueous polyurethane dispersions derived from polycarbonatediols

Aqueous polyurethane dispersions derived from polycarbonatediols, isophorone diisocyanate, and carboxylic diols including dimethylol propionic acid and dimethylol butyric acid were prepared. The effect of dispersing procedure is investigated by FT IR, GPC, and the tensile film properties. The polyurethane dispersions prepared by a standard procedure exhibit lower molecular weights due to the overhydrolysis of the NCO groups. The polyurethane dispersions prepared by a modified procedure exhibit significantly higher molecular weights due to more effective chain extension, and their cast films exhibit higher tensile strength. The particle size, tensile properties, thermal properties, and dynamic mechanical properties are investigated. The chemical structure of the polycarbonatediols seems to affect the tensile strength. The glass transition temperature of the soft segments, T_g(S), of the polyurethane dispersions can be seem from the DSC and DMA data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1723–1729, 2004     

Synthesis and physical properties of lipid-based poly(ester-urethane)s,I: Effect of varying polyester segment length

Four aliphatic thermoplastic poly(ester-urethane)s (PEUs) with similar molecular weights but varying polyesters molecular weight (534–1488 g/mol) were prepared from polyester diols, obtained by melt condensation of Azelaic acid and 1,9-Nonanediol, and 1,7-heptamethylene di-isocyanate (HPMDI) all sourced from vegetable oil feedstock. The thermal, and mechanical properties, and crystal structure of PEUs were investigated using DSC, TGA, DMA, tensile analysis and WAXD. For sufficiently long polyester chain, WAXD data indicated no hydrogen bonds polyethylene (PE)-like crystalline packing and for short polyester chains, small crystal domains with significant H-bonded polyamide (PA)-like packing. Crystallinity decreased with decreasing polyester molecular weights. The polymorphism of PEUs and consequently their melting characteristics were found to be largely controlled by polyester segment length. TGA of the PEUs indicated improved thermal stability with decreasing polyester chain length, suggesting a stabilization effect by urethane groups. Mechanical properties investigated by DMA and tensile analysis were found to scale predictably with the overall crystallinity of PEUs.     

Synthesis and properties of non-isocyanate aliphatic thermoplastic polyurethane elastomers with polycaprolactone soft segments

This study describes a non-isocyanate route for synthesis of aliphatic thermoplastic polyurethane elastomers (TPUEs) with excellent mechanical properties. Melt transurethane co-polycondensation of bis(hydroxyethyl) hexanediurethane with different polycaprolactone-diols was conducted at 170 °C under a reduced pressure of 3 mmHg to prepare a series of TPUEs. The TPUEs were characterized by gel permeation chromatography, FT-IR, ¹H–NMR, wide angle X-ray scattering, DSC, TGA, dynamic mechanical analysis, atomic force microscopy, SEM, and tensile analyses. The TPUEs exhibited M _n above 18,100 g/mol, T _g of ?35 to ?11 °C, T _m of up to 107 °C, initial decomposition temperature over 269 °C, tensile strength up to 32 MPa with a strain at break of 1119%, and resilience of 65% to 83%. TPUEs with good tensile strength and resilience were successfully prepared through a non-isocyanate route.     

Fumed silica/polyurethane nanocomposites: effect of silica concentration and its surface modification on rheology and mechanical properties

The effects of nanosilica type and its content on microstructure, mechanical properties, and rheology of thermoplastic polyurethane (TPU) nanocomposites were investigated. Three different types of silica which included: unmodified (Si-Un) and commercially modified with octylsilane (Si-OS) and polydimethylsiloxane (Si-PDMS) with 5, 10, and 15 wt% of all fillers, were prepared by solution casting method. Scanning electron microscopy (SEM) showed that surface treatment of nanosilica with OS and PDMS reduced the aggregation of particles and improved their dispersion at microlevel. The effect of adding nanoparticles on microdomain morphology of TPU was studied by transmission electron microscopy (TEM), infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The results demonstrated a relatively good interaction between the hard and soft segments in the presence of treated nanosilica that hindered the crystallization of hard segments in TPU. Thermogravimetric analysis (TGA) and tensile test showed that nanocomposites with treated nanosilica have better thermal stability and mechanical properties. The dynamic rheological studies indicated that nanocomposites containing Si-OS and Si-PDMS (with better dispersion and higher interface between the soft and hard domains in TPU) have improved viscoelastic properties in comparison with nanocomposites with untreated silica. In this study, dynamic frequency sweep data were correlated by a generalized Maxwell model and found that elastic constants of TPU chains were improved in the presence of modified silica nanoparticles.     

Synthesis and characterization of biodegradable crosslinked polymers from 5‐hydroxylevulinic acid and α,ω‐diols

Novel biodegradable chemically crosslinked polymers, poly(5‐hydroxylevulinic acid‐co‐α,ω‐diol)s (PHLA‐diols), were synthesized from 5‐hydroxylevulinic acid and α,ω‐diols and characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The gel content, swelling ratio, tensile properties, and hydrolytic degradation behaviors were also measured and assessed. The glass‐transition temperature of the PHLA‐diols could be adjusted within a wide range (?50 to 30°C) by the type and feed ratio of the diol. Because of the low glass‐transition temperature and crosslink structure, they exhibited certain elastic properties. The tensile modulus, strength, and elongation at break measured at 37°C were 1.4–6.3 MPa, 0.8–1.6 MPa, and 10–25%, respectively. These polymers could be hydrolytically degraded. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure-property relations of novel polyamide-6 elastomers prepared through reactive processing

A series of polyamide-6 elastomers (PAEs) employing polytetramethylene glycol (PTMG) as soft segments, diphenylmethane diisocyanate (MDI) as chain extender and polyamide-6 as hard segments is prepared through reactive processing. The MDI is also employed to suppress the crystallization capacity of soft segments and to regulate the soft segment length in the obtained PAEs. The chemical structures, crystallization properties, morphology, mechanical properties and thermal stability are extensively studied by Fourier transform infrared spectroscopy (FTIR), Hydrogen nuclear magnetic resonance (HNMR), X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Transmission electron microscope (TEM), Dynamic mechanical analyzer (DMA), Tensile test and Thermal gravity analysis (TGA), respectively. TEM images demonstrate that PAE samples exhibit a microphase separated morphology with polyamide-6 domains disperse in the PTMG phase in nano-scale. DMA curves indicate that the prepared PAEs possess a typical elastomer thermodynamic behavior and a broad temperature-independent rubbery plateau. Meanwhile, PAEs exhibit superior mechanical properties with 55 MPa for tensile strength and 1100% for elongation at break. The TGA prove that the thermal stability of PAE can satisfy the requirement of multiple-processing without decomposition.     

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) reinforced by poly(lactic acid) fibers

Biodegradable composites of poly(butylene succinate‐co‐butylene adipate) (PBSA) reinforced by poly(lactic acid) (PLA) fibers were developed by hot compression and characterized by Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analyzer, and tensile testing. The results show that PBSA and PLA are immiscible, but their interface can be improved by processing conditions. In particular, their interface and the resulting mechanical properties strongly depend on processing temperature. When the temperature is below 120 °C, the bound between PBSA and PLA fiber is weak, which results in lower tensile modulus and strength. When the processing temperature is higher (greater than 160 °C), the relaxation of polymer chain destroyed the molecular orientation microstructure of the PLA fiber, which results in weakening mechanical properties of the fiber then weakening reinforcement function. Both tensile modulus and strength of the composites increased significantly, in particular for the materials reinforced by long fiber. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43530.     

Synthesis and properties of poly(amide-imide-urethane) thermoplastic elastomers

A new class of poly(amide-imide-urethane) thermoplastic elastomers based on two-step synthesis of 4,4′-methylene bis(4-phenylisocyanate) with different polyols (PPG and PTMG) and trimellitic anhydride was synthesized. Both resulting polymers showed semicrystalline structures and were readily soluble in polar solvents such as N-methyl-2-pyrrolidone and dimethyl formamide. The soluble poly(amide-imide-urethane)s afforded transparent, flexible, and tough films. Both new copolymers were then characterized by FTIR spectroscopy, universal tensile tester, simultaneous DTA/TGA (SDT), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction studies, to determine their morphological structures, thermal stability, and mechanical properties. Compared to typical polyurethanes, these polymers exhibited better thermal stabilities due to the presence of imide groups. DSC and X-ray diffraction studies showed semicrystalline patterns for these polymers. Stress–strain properties revealed that these polymers have good extensibility like typical polyurethanes. © 1998 SCI.     

Synthesis and characterization of alternating copolymer from carbon dioxide and propylene oxide

High yield and pure zinc glutarate catalysts used for copolymerization of carbon dioxide and propylene oxide have been synthesized in different solvents by ultrasonic methodology. For the purposes of comparison, low‐yield zinc glutarates were also synthesized via mechanical stirring method with other synthetic conditions remaining unchanged. Fourier Transform Infrared Spectroscopy and wide‐angle X‐ray diffraction techniques confirmed the presence of high‐quality zinc glutarate catalysts. Accordingly, poly(propylene carbonate) (PPC) can be synthesized from carbon dioxide and propylene oxide using the zinc glutarate catalysts. It was confirmed that the as‐prepared PPC had an alternating copolymer structure together with high molecular weight. The thermal and mechanical properties of the obtained PPC copolymer were determined by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile test. DSC and TGA results showed that the PPC copolymer exhibited high glass transition temperature (39.39°C) and decomposition temperature (278°C) when compared to their corresponding values reported in the literature. Tensile test showed that the PPC film exhibited superior mechanical strength. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2327–2334, 2002     

Mechanically strong shape memory polyurethane for water vapour permeable membranes

Water vapour permeable polymeric thin films possess significant importance in miscellaneous applications such as packaging, medical devices, controlled‐release systems, electronics and biosensors. In this work, a series of shape memory polyurethanes (SMPUs) were synthesized by a two‐step pre‐polymerization technique with variations in hard to soft segments and molecular weight of macroglycol. DSC, Fourier transform infrared spectra, dynamic TGA and tensile testing were carried out to characterize and evaluate the properties of these synthesized SMPUs. The effect of the soft segment and the molecular weight of macroglycol on the thermal properties, mechanical properties and water vapour permeability of the synthesized SMPUs were investigated to achieve a good water vapour permeable membrane. We found that the synthesized SMPUs demonstrated a good water vapour transmission rate of over 1460 g m^?2 day^–1 as well as robust mechanical properties with tensile strength 19.8 MPa indicating a promising permeable polymeric thin film for many potential applications, especially as protective clothing. © 2018 Society of Chemical Industry     

Radiation Graft Co-polymerization of Methacrylic Acid (MAA) onto Sago Starch Films

Abstract

In this work, the factors that may affect the gamma radiation-induced grafting of methacrylic acid monomer (MAA) onto sago starch films were investigated. The graft copolymers were characterized by tensile mechanical testing, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and infrared spectroscopy. The results showed that the highest grafting yield was obtained within the irradiation dosage level of 10–20 kGy and by using monomer concentration range of 15–20 wt%. The highest tensile mechanical properties were observed for sago starch films having 66% graft yield of MAA. The DSC thermograms indicated a decrease in the gelatinization temperature (temperature at which the disruption of the molecular orders in the starch granules occurs) of sago starch as a result of grafting. This behavior was explained on the basis that radiation grafting prevents the retrograddation process of starch (starch re-crystallization). On the other hand, the IR spectra indicate an increase in the intensity of the absorption band due to C?O stretching, confirming the occurrence of grafted chains of MAA.     

Synthesis and characterizations of branched poly(butylene succinate) copolymers with 1,2‐octanediol segments

Branched poly(butylene succinate) (PBS) copolymers were synthesized, from succinic acid (SA), 1,4‐butanediol (1,4‐BD), and 1,2‐octanediol (1,2‐OD) through a two‐step process containing esterification and polycondensation, with different mole fractions of 1,2‐OD segments. The branched PBS copolymers were characterized with ¹H‐NMR, differential scanning calorimetry (DSC), wide angle X‐ray diffraction (WAXD), thermogravimetric analysis (TGA), dynamic rheological testing, and tensile properties analysis. The results of DSC and WAXD show that, with the increasing of the 1,2‐OD segments content, the glass transition temperature (T_g), melting temperature (T_m), crystallization temperature (T_c), and the degree of crystallinity (X_c) decrease. While the crystal structure of PBS does not change by introducing 1,2‐OD segments. The results of TGA and dynamic rheological testing indicate that the thermal stability of neat PBS is improved with the addition of 1,2‐OD segments. The incorporation of 1,2‐OD segments has some effects on the rheological properties of PBS, such as complex viscosities (|η*|), storage modulus (G′), and loss modulus (G″). Tensile testing demonstrates that the elongation at break is improved significantly with increasing 1,2‐OD segments content, but without a notable decrease of tensile strength. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and Characterization of Thermoplastic Elastomer Based on Amino-terminated Polyamide-6 and Diisocyanate-terminated Polytetramethylene Glycol

Polyamide thermoplastic elastomers are successfully synthesized by adding polycondensation of amino-terminated polyamide-6 (with a molecular weight of 1000 and 2000 g/mol) and diisocyanate-terminated polytetramethylene glycol (with molecular weight of 1500 and2500 g/mol) with dimethylacetamide as solvent at 140°C. The structures of oligomers and polyamide thermoplastic elastomers are characterized by Fourier transform infrared. The thermogravimetry analysis result shows that the product displays good thermostability. Differential scanning calorimetry curves of polyamide thermoplastic elastomers exhibit two melting temperatures indicating phase separation of polyamide thermoplastic elastomers. Besides, the polyamide thermoplastic elastomers display excellent mechanical properties of high tensile strength (33–61 MPa) and high elongation at break (384–1220%).     

Synthesis and proton conductivity studies of 5‐aminotetrazole‐doped sulfonated polymer electrolyte membranes

This work reports the preparation and characterization of a new anhydrous proton conducting membrane based on poly(vinyl alcohol) (PVA), sulfosuccinic acid (SSA), and 5‐aminotetrazole (ATet) at various stoichiometric ratios. The proton conductivities of membranes were investigated as a function of ATet composition, SSA composition, and temperature. New anhydrous proton conducting membranes were characterized by infrared spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), methanol permeability, and impedance measurements for proton conductivity. TGA showed that the samples were thermally stable up to 150°C. DSC results illustrated the homogeneity of the materials. Mechanical analysis showed that the storage modulus of the PVA–SSA–ATet blend polymer membranes decreased with increasing ATet content. The membranes with higher tetrazole content, or higher acid doping level presented the higher proton conductivity. PVA–SSA–ATet4 can exhibit an anhydrous proton conductivity of 1.7 × 10⁻³ S/cm at 130°C and the proton conductivity increased with increasing temperature and acid doping level. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Multifunctional,robust, and self-healable polyurethane coatings cross-linked by Diels–Alder reaction of calix[4] arenes containing furan groups

Self-healing coatings can restore their performance after inevitable damage and are promising in the industry owing to their longer service life and lower repair cost. The use of Diels–Alder reaction bonds is well-known to generate thermally self-healing coatings. In this study, a series of cross-linked self-healing polyurethane (PU) coatings were synthesized through Diels–Alder reactions of p-tert-butyl calix[4]arene bearing furan groups (C4A-FA) as a new chain extender and a bismaleimide (BMI) polyether amine as a Diels–Alder cross-linking agent. Adding C4A-FA to PUs improves their mechanical properties, thermal stability, and self-healing ability. Additionally, these modifications can result in the formation of composite networks with PU that exhibit thermoreversibility and self-healing properties. These changes have led to PUs containing modified calix[4]arene (C4A-FA) having better properties compared with unmodified calix[4]arene PUs. The properties of prepared coatings were evaluated by Fourier transform infrared spectroscopy, scanning electron microscope, differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), and tensile tests compared with a typical PU sample. The tensile and TGA results show an improvement in the thermal and mechanical properties of the polymers by increasing the C4A-FA content. By replacing 15% of butandiol (BDO) with C4A-FA in PU pure, the tensile strength increased from 1.69 to 5.14 MPa. Furthermore, adding diels–alder (DA) bonds enhanced the tensile strength to 10.49 MPa for PU-C4A15-DA. According to DSC results, a broad endothermic peak from nearly 80–140°C confirmed the retro-DA reactions in the synthesized thermoreversible samples. The healing efficiency of the PU-C4A15-DA sample was obtained at 92.5% (measured by tensile test), which is the highest value among cross-linked self-healing PUs reported in the literature.     

Synthesis,characterization, and properties of degradable poly(l‐lactic acid)/poly(butylene terephthalate) copolyesters containing 1,4‐cyclohexanedimethanol

High‐molecular‐weight copolyesters based on poly(butylene terephthalate) as rigid aromatic segments and poly(l‐lactic acid) (PLLA) as degradable aliphatic segments were synthesized via the polycondensation of terephthalic acid, 1,4‐butanediol (BDO), 1,4‐cyclohexanedimethanol (CHDM), and PLLA oligomer. By tailoring the molar ratio of diols (BDO and CHDM), we investigated in detail the effects of the CHDM rigid hexacyclic ring on the synthesis, mechanical properties, thermal stabilities, and degradation behaviors of the copolyesters. With increasing CHDM content, the initial decomposition temperature increased from 282.5 to 322.2°C, and the tensile strength improved by nearly four times, from 5.4 to 19 MPa. When the molar ratio of BDO/CHDM was 95/5, the weight‐average molecular weight of the copolyester was 89,400 g/mol with a polydispersity of 1.96. In addition, hydrolytic degradation results in phosphate buffer solution indicate that the degradation rate of the copolyesters displayed a strong dependency on the temperature and CHDM composition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011