Thermal Behavior Of Poly Research Articles

Corrosion protection performance of poly(PyM-co-GMA)/SWCNT nanocomposites coating on mild steel

Recently, there has been significant emphasis on developing electroactive functional methacrylate polymers for anticorrosive applications. In this context, we have synthesized Poly[(3,5-dimethyl-1H-pyrazole-1-yl) methyl methacrylate-co-glycidyl methacrylate] [Poly(PyM-co-GMA)] and its nanocomposite with single- walled carbon nanotubes (SWCNTs) [Poly(PyM-co-GMA)/SWCNT]. The resulting materials were characterized using Fourier Transform Infrared spectroscopy (FT-IR) and X-ray Diffraction analysis (XRD). Morphological changes due to the incorporation of SWCNTs were examined using field-emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). The optical properties of Poly(PyM-co-GMA) and Poly(PyM-co-GMA)/SWCNT (0.5, 1.0, and 1.5 wt. %) were investigated. The thermal behavior of Poly(PyM-co-GMA) and its SWCNT nanocomposites was analyzed through thermogravimetric analysis (TGA). The anticorrosive performance of the prepared materials was evaluated on a mild steel substrate (MS) in a 3.5% (w/v) NaCl medium using electrochemical techniques. Results from potentiodynamic polarization and electrochemical impedance spectroscopy indicate that the Poly(PyM-co-GMA) and Poly(PyM- co-GMA)/SWCNT coatings (0.5, 1.0, and 1.5 wt. %) provide effective barrier protection for mild steel against marine environments.

Thermal Behavior of Poly(vinyl alcohol) in the Form of Physically Crosslinked Film.

Evaluation and understanding of the thermal behavior of polymers is crucial for many applications, e.g., polymer processing at relatively high temperatures, and for evaluating polymer-polymer miscibility. In this study, the differences in the thermal behavior of poly(vinyl alcohol) (PVA) raw powder and physically crosslinked films were investigated using various methods, such as thermogravimetric analysis (TGA) and derivative TGA (DTGA), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Various strategies were adopted, e.g., film casting from PVA solutions in H2O and D2O and heating of samples at carefully selected temperatures, in order to provide insights about the structure-properties relationship. It was found that the physically crosslinked PVA film presents an increased number of hydrogen bonds and increased thermal stability/slower decomposition rate compared to the PVA raw powder. This is also depicted in the estimated values of specific heat of thermochemical transition. The first thermochemical transition (glass transition) of PVA film, as for the raw powder, overlaps with mass loss from multiple origins. Evidence for minor decomposition that occurs along with impurities removal is presented. The overlapping of various effects (softening, decomposition, and evaporation of impurities) has led to confusion and apparent consistencies, e.g., from the XRD, it is derived that the film has decreased crystallinity, and apparently this is in agreement with the lower value of heat of fusion. However, the heat of fusion in this particular case has a questionable meaning.

Thermal Behavior of Poly(acrylonitrile-co-1-vinyl imidazole) During Stabilization

Thermal Behavior of Poly(acrylonitrile-co-1-vinyl imidazole) During Stabilization

Compositional Influence on the Morphology and Thermal Properties of Woven Non-Woven Mats of PLA/OLA/MgO Electrospun Fibers.

In the present work, a statistical study of the morphology and thermal behavior of poly(lactic acid) (PLA)/oligomer(lactic acid) (OLA)/magnesium oxide nanoparticles (MgO), electrospun fibers (efibers) has been carried out. The addition of both, OLA and MgO, is expected to modify the final properties of the electrospun PLA-based nanocomposites for their potential use in biomedical applications. Looking for the compositional optimization of these materials, a Box–Wilson design of experiment was used, taking as dependent variables the average fiber diameter as the representative of the fiber morphologies, as well as the glass transition temperature (Tg) and the degree of crystallinity (Xc) as their thermal response. The results show <r2> values of 73.76% (diameter), 88.59% (Tg) and 75.61% (Xc) for each polynomial fit, indicating a good correlation between both OLA and MgO, along with the morphological as well as the thermal behavior of the PLA-based efibers in the experimental space scanned.

Effect of kaolin waste annealing on the structural and thermal behavior of poly(ε−caprolactone)

The heat treatment effect on kaolin waste from mining was evaluated on the structural and thermal behavior of poly(ε-caprolactone) (PCL). The PCL/KW (kaolin waste) and PCL/HTKW (heat-treated kaolin waste) composites were processed in an internal mixer and subsequently characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The kaolin waste showed kaolinite and quartz in its composition, while the heat treatment at 1200°C modified it to mullite, quartz and silica-rich amorphous phase. By XRD, there was an increase in the intensity of the peak 2θ = 23.9° of the PCL/KW composites compared to neat PCL. In contrast, PCL/HTKW composites tended to reduce the intensity of the peak 2θ = 23.9°, especially at 5% HTKW. The crystalline melting temperature and the degree of crystallinity of PCL/KW and PCL/HTKW composites were practically unchanged, compared to PCL. However, the crystallization process was more effective with the kaolin waste (KW) without heat treatment, indicating that the HTKW amorphous phase inhibited crystallization. The PCL/KW development promoted an increase in crystallization temperature, relative crystallinity, and crystallization rate, surpassing PCL and the PCL/HTKW system. In view of this, kaolin waste has the potential to accelerate the PCL crystallization process, contributing to add value to a material that would otherwise be discarded and minimizing environmental impacts.

Miscibility and thermal behavior of poly(methyl methacrylate) and polystyrene blend using benzene as a common solvent.

Polymer blending is one of the advanced technologies to attain polymeric material with tailored properties. In this work, the miscibility of Poly(methyl methacrylate) (PMMA) and Polystyrene (PS) blend in benzene was investigated by employing various techniques such as FTIR spectroscopy, viscosity measurement technique, light scattering techniques, DSC and TGA techniques over an extended range of concentrations, compositions, and temperatures. The results revealed that there exist hydrogen bonding and hydrodynamic interactions which led these polymers to get miscible to a large extent. The compatibility increased with the increasing PS contents or increase in temperature of the system. In addition, the thermal stability of blends was found to be improved with the increase in the compatibility of the polymer.

Study on melting and crystallization of PHBHx thin films using IR and 2D correlation spectroscopy

AbstractThe thermal behavior of poly(hydroxybutyrate‐co‐hydroxyhexanoate) (PHBHx) thin films having various molar fractions of hydroxyhexanoate (Hx) was investigated using IR, 2D gradient mapping, 2D correlation spectroscopy (2D‐COS), and multivariate curve resolution (MCR) analysis. The melting and crystallization temperatures were determined using 2D gradient mapping. The 2D‐COS combined with MCR analysis provided information on the unambiguous components that appeared in PHBHx thin films during the melting and crystallization processes.

Effect of thermal annealing on crystal evolution and multiple melting behaviors of molded poly(L-lactic acid) and poly(butylene succinate) blends upon heating investigated by TMDSC

The influence of post-process annealing treatment on the structural and thermal behaviors of poly(L-lactic acid)/poly(butylene succinate) (PLLA/PBS) blend was investigated by temperature modulated differential scanning calorimetry (TMDSC) and wide-angle X-ray diffractometry. It is shown that the low-order α′-structure of PLLA was formed in the as-molded samples and the molded products annealed at the temperatures below the melting of PBS, whereas the high-order α-crystal was developed when the high temperature of annealing (152 °C) was applied. With the addition of poly(ethylene glycol) plasticizer to the blends, the formation of high-order α-structure was prohibited. During the DSC heating scan, the α′- to α-crystalline phase transformation did not occur. The evidence of multiple melting behaviors observed by TMDSC was ascribed to the simultaneous melting, recrystallization, and remelting of the PLLA and PBS crystals in the blends.

Crystallization and Thermal Behaviors of Poly(ethylene terephthalate)/Bisphenols Complexes through Melt Post-Polycondensation.

Three kinds of modified poly(ethylene terephthalate) (PET) were prepared by solution blending combined with melt post-polycondensation, using 4,4′-thiodiphenol (TDP), 4,4′-oxydiphenol (ODP) and hydroquinone (HQ) as the bisphenols, respectively. The effects of TDP, ODP and HQ on melt post-polycondensation process and crystallization kinetics, melting behaviors, crystallinity and thermal stability of PET/bisphenols complexes were investigated in detail. Excellent chain growth of PET could be achieved by addition of 1 wt% bisphenols, but intrinsic viscosity of modified PET decreased with further bisphenols content. Intermolecular hydrogen bonding between carbonyl groups of PET and hydroxyl groups of bisphenols were verified by Fourier transform infrared spectroscopy. Compare to pure PET, both the crystallization rate and melting temperatures of PET/bisphenols complexes were reduced obviously, suggesting an impeded crystallization and reduced lamellar thickness. Moreover, the structural difference between TDP, ODP and HQ played an important role on crystallization kinetics. It was proposed that the crystallization rate of TDP modified PET was reduced significantly due to the larger amount of rigid benzene ring and larger polarity than that of PET with ODP or HQ. X-ray diffraction results showed that the crystalline structure of PET did not change from the incorporation of bisphenols, but crystallinity of PET decreased with increasing bisphenols content. Thermal stability of modified PET declined slightly, which was hardly affected by the molecular structure of bisphenols.

Study of thermal behavior of poly (lactic) acid composites with electron beam irradiated luffa fiber

Modification of surface of natural fibers by high energy electron beam irradiation (6 MeV) is a process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, light weight and environment friendly factors. We have studied the thermal properties such as thermal degradation and crystallinity behavior of biodegradable composites using biodegradable polymer poly (lactic) acid (PLA) and fiber of luffa cylindrica (LC) fabricated by using injection molding technique. First, reinforcement LC fibers are irradiated with electron beam of 0.5, 1.0, 2.0, 4.0 and 10.0 Gy using 6 MeV linear accelerator at room temperature in presence of air. The thermal properties like glass transition temperature [Formula: see text], cold crystallization temperature [Formula: see text], melting peak temperature [Formula: see text] and thermal stability of the composites are studied using differential scanning calorimetry (DSC) in the temperature range from 30[Formula: see text]C to 250[Formula: see text]C and thermogravimetric analysis (TGA) in temperature range from 20[Formula: see text]C to 700[Formula: see text]C. The variation of these properties in response to the irradiation dose is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature increase. However, the thermal stability of the composites is found to increase with increase in irradiation dose.

Study of Thermal Behaviour of Poly(Lactic) Acid Composites with Gamma Irradiated Luffa Fiber

Modification of surface of natural fibers by high-energy gamma irradiation (6 MV) is a competent process for enhancing the adhesion between fiber and matrix. Composites reinforced with natural fiber have gained a prominent place in the field of research and innovation due to the advantages such as low cost, lightweight and environment friendly. We have studied the thermal properties of biodegradable composites using biodegradable polymer poly(lactic) acid and fiber of Luffa cylindrica (LC) fabricated by using injection molding technique. Before reinforcement LC fibers are irradiated with gamma rays of 0.5, 1 and 2 Gy using 6 MV linear accelerator at room temperature in the presence of air. The thermal properties like glass transition temperature (Tg), crystallization temperature (Tcc), melting peak temperature (Tm) and thermal stability of the composites are studied using differential scanning calorimetry in the temperature range from 30 to 250 °C and thermogravimetric analysis in temperature range from 20 to 700 °C. The variation of these properties in response to the irradiation dose and fiber loading is analyzed in detail. It is observed that with increase in irradiation dose, glass transition temperature and crystallization temperature are increasing. However, the thermal stability of the composites is found to decrease with increase in irradiation dose.

Poly(azomethine‐imide)s containing siloxane moities: Optical, thermal, mechanical, and morphological properties

ABSTRACTA new series of poly(azomethine‐imide)s having siloxane moities in backbone was prepared using different dianhydrides.Thermal, optical, and morphological properties of these polymers were clarified. Also, bulky CO and CF3 group effects and meta or para‐substituted aldeyhde effects on the mentioned properties were evaluated. The structural characterization of poly(azomethine‐imide)s was carried out using a FT‐IR spectroscopy. The optical properties of the polymers were performed via an UV–Vis spectrophotometer. Optical band gap of the poly(imide)s containing azomethine was calculated between 2.20 and 2.33 eV. Thermal behavior of poly(azomethine‐imide)s was also studied using TG‐DTA, DSC, and DMA techniques. The onset degradation temperature and percentage char values of the polyimides were found in the range from 429 to 545 °C and 22 to 35%, respectively. Thermal stability results demonstrated that benzophenone bearing poly(azomethine‐imide)s have higher onset temperature, percentage char, and the glass transition temperature than poly(azomethine‐imide)s derived from hexafluoroisopropylidene. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48364.

Relationships between crystalline structure and the thermal behavior of poly(ethylene 2,5‐furandicarboxylate): An in situ simultaneous SAXS‐WAXS study

Poly(ethylene 2,5‐furandicarboxylate) (PEF) is an emerging bio‐based polymer with interesting thermal and barrier properties. In this study, the melting behavior of PEF was investigated in situ by means of simultaneous wide and small angle X‐ray scattering (WAXS and SAXS) measurements coupled with DSC measurements. This study gives the first evidence of what happens from a structural point of view during the multiple melting behavior of PEF, which is composed of three distinct events, taking into account the nature of the initial crystalline phase present. The first result is that the α′ form, induced at low crystallization temperature, does not undergo any phase transformation upon heating revealing its stable character. Second, the comparison of the SAXS and WAXS results with the DSC ones showed that the multiple melting behavior observed is attributed to a melting–recrystallization–melting process. Third, this work also definitely shows that the low amplitude melting endotherm observed in the DSC thermograms is ascribed to the melting of secondary crystals. Finally, SAXS‐WAXS results led to the conclusion that the secondary crystals cannot be depicted by the commonly accepted lamellar insertion model. Another microstructural representation of these secondary crystals is proposed. In this model, the secondary crystals consist of bundles of macromolecules, which formed small crystalline entities located between the primary crystalline lamellae stacks. POLYM. ENG. SCI., 59:1667–1677 2019. © 2019 Society of Plastics Engineers

Thermal behavior of poly[3,3-bis(azidomethyl)oxetane] compositions with an energetic plasticizer: Calorimetric and optical studies

An experimental phase diagram for the high-energy system poly[3,3-bis(azidomethyl)oxetane] – three-component mixture of dinitrodiazaalkanes has been for the first time constructed in a broad temperature-concentration range using an original optical method and differential scanning calorimetry. The diagram belongs to the type semicrystalline polymer – thermodynamically good solvent, which is better than pure 2,4-dinitro-2,4-diazapentane studied earlier. The diagram contains two boundary curves, one describing full polymer amorphization and the other reflecting the solubility of the dinitrodiazaalkanes mixture in the amorphous polymer regions. The curves are shifted toward lower temperatures with an increase in the molar mass of the polymer. The domains on the phase diagram are classified using an original concept that treats semicrystalline polymers as microheterogeneous, internally stressed liquids with crystallites acting as crosslinks of the intermolecular network. The phase structure of the mixture at different points of the temperature-concentration field is illustrated with optical microphotographs. It is argued that calorimetry is not suitable as a standalone technique for investigating phase behavior of slowly crystallizing polymer systems.

Sustainable thermoplastics from renewable resources: Thermal behavior of poly(1,4-cyclohexane dimethylene 2,5-furandicarboxylate)

Poly(1,4-cyclohexane dimethylene 2,5-furandicarboxylate) (PCHDMF) is a sustainable thermoplastic that can be prepared from renewable resources with potential uses as a replacement for its terephthalate (PCHDMT) and naphthalate (PCHDMN) analogues. A detailed study has been undertaken to assess its thermal behavior and chemical/structural characteristics, in comparison to its counterparts. The melting temperature of PCHDMF was observed at Tm = 264.5 °C, the glass transition was obtained at 77 °C and the cold crystallization temperature was seen at 121 °C. The melting of the polymers was studied under a variety of conditions and all samples displayed the characteristic melting-recrystallization-remelting behavior. Isothermal and dynamic crystallization tests revealed that PCHDMF crystallizes at faster rates than its analogues, while the equilibrium melting point of PCHDMF was established at 300 °C. The enthalpy of fusion values for the polyesters were found ΔHm = 137 J/g for PCHDMF, ΔHm = 108 J/g for PCHDMT, ΔHm = 119 J/g for PCHDMN. Using the Lauritzen-Hoffman analysis of spherulite growth rates, larger Kg values were found for PCHDMF, due to its less flexible structure.

Thermal behavior of poly(VDF-ter-TrFE-ter-CTFE) copolymers: Influence of CTFE termonomer on the crystal-crystal transitions

Depending on their CTFE content (from 0 to 10 mol %), poly (VDF-ter-TrFE-ter-CTFE), poly(vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene) copolymers exhibit ferroelectric (FE) or relaxor ferroelectric (RFE) properties at low temperature whereas they all present paraelectric (PE) behavior at high temperature. This thermal evolution of their electro-active properties is related to reversible crystal-crystal transitions. We studied these structural transitions for three different copolymers with various amount of CTFE (0, 4.4 and 9.7 mol %) using simultaneous SAXS-WAXS experiments along thermal cycles. We identified two types of crystalline phase at low temperature with their proper crystal-crystal transition: the first one containing all-trans conformations (orthorhombic FE phase) has a discontinuous transition towards the hexagonal PE phase, the second one which incorporates gauche disordered conformations (orthorhombic DFE (Defective Ferroelectric) or RFE) transits continuously towards the same hexagonal PE phase. For the intermediate composition (4.4 mol % CTFE), we observe the coexistence of these two simultaneous phase transitions, one discontinuous (FE to PE) and one continuous (RFE to PE), whereas only the continuous one exists in the higher CTFE composition (9.7 mol %). Relaxor ferroelectric properties are precisely observed in the temperature range of the structural RFE to PE transition [0 °C, 40 °C], highlighting the importance of this crystal-crystal transition. By coupling electric displacement−electric field (D−E) loop measurements, thermo-mechanical experiments (DSC and DMA) and dielectric spectroscopy, we propose a model to explain this RFE-PE continuous crystal-crystal transition in terpolymers.

Thermal behaviour of poly(methyl methacrylate)/fullerene composite films

ABSTRACTPoly(methyl methacrylate) films and poly(methyl methacrylate)/fullerene composite films were fabricated by casting from toluene solutions. The mass fraction of fullerene (C60) was varied from 0.05–3 wt. %. The effect of the fullerene (C60) content on the thermal degradation parameters of the composite films was evaluated by thermogravimetric (TG) analysis. It was found that the incorporation of C60 improved the thermal stability of the polymers. The films eventually decomposed in three stages. Incorporation of fullerene caused a change in the distribution of mass loss over the stages of degradation in comparison with the pristine polymer. Using differential scanning calorimetry (DSC), the phase transitions from the glassy state to the elastic one was studied for the examined polymeric materials. New data relating to the effect of C60 on the glass transition temperature of composites with low weight fractions of filler were obtained. Specifically, for films containing up to 0.1 wt. % of C60, a single glass transition temperature was found, whereas for composites with a higher concentration of filler, two glass transition temperatures were recorded.

Structure and thermal behaviors of poly(vinyl alcohol)/surfactant composites: Investigation of molecular interaction and mechanism

Poly(vinyl alcohol) (PVA) is a promising biocompatible polymer, whose applicability is limited by its narrow processing window. Here, we adopted a facile approach to broaden the processing windows of PVA based on phosphoric ester of poly(ethylene oxide) (10) nonylphenyl (NP‐10P). Thermal analysis shows that both the melting temperature (Tm) and the glass transition temperature (Tg) of PVA decrease noticeably as NP‐10P content increases, indicating good miscibility of NP‐10P with PVA. The thermal degradation kinetics suggests composites display excellent thermal stability compared with neat PVA. The pyrolysis mechanism of PVA before and after modification with NP‐10P varies from chain unzipping degradation followed by chain random scission to chain random scission. The processing window of PVA is broadened from 9°C to 98°C with low content NP‐10P (5 wt%). Moreover, the composites maintain significant mechanical performance and transparency. This work provides an environmentally friendly and economical method to improve the possibility of thermal melt processing for PVA.

Properties and phase structure of melt-processed PLA/PMMA blends

This study examines the rheological, mechanical and thermal behavior of Poly(lactic acid)/Poly(methyl methacrylate) (PLA/PMMA) blends and takes a look at the phase structure evolution during their melt processing. Semi-crystalline or amorphous PLA grades were combined with PMMA of different molecular weight to prepare the blends. The rheological properties and phase structure was first assessed using small-amplitude oscillatory shear experiments. The blends were injection molded into bars and characterized in terms of their tensile properties and of their dynamic mechanical behavior. Differential scanning calorimetry was also used to study the miscibility and crystallization behavior of prepared blends. Tensile properties of the blends nearly followed a linear mixing rule with no detrimental effect that could have been associated with an uncompatibilized interface. However, dynamic mechanical analysis and calorimetric experiments showed that some phase separation was present in the molded parts. Nevertheless, a single Tg was found if sufficient time was given in quiescent conditions to achieve miscibility. The Gordon-Taylor equation was used to assess the polymer interactions, suggesting that miscibility is the thermodynamically stable state. The ability of PLA to crystallize was strongly restricted by the presence of PMMA and little or no crystallinity development was possible in the blends with more than 30% of PMMA. Results showed an interesting potential of these blends from an application point of view, whether they are phase separated or not.

Influence of lithium salt-induced phase separation on thermal behaviors of poly(vinylidene fluoride)/ionic liquid gels and pore/void formation by competition with crystallization.

The thermal behavior of poly(vinylidene fluoride)/1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide/lithium bis(trifluoromethylsulfonyl)amide (PVDF/[C2mim][TFSA]/LiTFSA) gels, prepared by cooling from the hot solution, was investigated with various concentrations of LiTFSA (CLiTFSA). The peak melting temperature (Tm) of the gels shifted toward higher temperatures with increased CLiTFSA. However, the thickness of lamellar crystal was found to decrease with the increase in CLiTFSA, which meant that the increase in Tm was not caused by the thickening of lamellar crystal. Furthermore, we found the appearance of domains above Tm in the high CLiTFSA region (≥20 wt%), which was a lithium ion-rich phase caused by the phase separation. Therefore, it is considered on the basis of Nishi–Wang equation that an increase in the interaction parameter with increasing CLiTFSA toward the phase separation increased the Tm. The phase-separated domains competed with the subsequent crystallization, which resulted in the formation of micrometer-sized pores and nanometer-sized voids in the spherulites. Spectral measurements revealed that PVDF was not specifically solvated in the solution state above the crystallization temperature, while [TFSA]− anion formed a complex with lithium ion irrespective of the PVDF content. These results led to the consideration that an increase in the interaction parameter might be caused by the strong interaction between lithium ion and [TFSA]− anion to form the complex, which would also lower the interaction between PVDF and [TFSA]− anion.