Thermal Stability Of Poly Research Articles

Investigation of the thermostability of poly(ethylene terephthalate)–hemp fiber composites: Extending natural fiber reinforcements to high‐melting thermoplastics

ABSTRACTThe thermal stability of poly(ethylene terephthalate) reinforced with 1, 5, 10, 15, and 20% hemp fibers was investigated with the aim of extending the applications of biocomposites to high‐melting thermoplastics. The material was injection‐molded following compounding with a torque‐based Rheomix at 240, 250, and 260°C. A combination of thermogravimetric methods at 5, 10, and 20°C/min, Liu and Yu's collecting temperature method, and Friedman's kinetic method were used for testing and analysis. A significant thermostability for all formulations was observed below 300°C; this demonstrated their potential for successful melt processing. Moreover, two degradation steps were observed in the temperature ranges 313–390 and 390–490°C. The associated apparent activation energies within the temperature ranges were determined as 150–262 and 182–242 kJ/mol, respectively. We found that the thermostability was significantly affected by the heating rates; however, the effect of the temperature of the mixing chamber was negligible. These findings suggest that the successful melt processing of high‐melting thermoplastics reinforced with natural fibers is possible with limited fiber thermodegradation. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42500.

On the use of tris(nonylphenyl) phosphite as a chain extender in melt‐blended poly(hydroxybutyrate‐co‐hydroxyvalerate)/clay nanocomposites: Morphology, thermal stability, and mechanical properties

ABSTRACTThe influence of the incorporation of tris(nonylphenyl) phosphite (TNPP) as a chain extender on the morphology and thermal stability of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV)/clay nanocomposites obtained by melt mixing has been studied. Two different clays have been used: a laminar organomodified montmorillonite (Cloisite® 30B) and a tubular unmodified halloysite (HNT). The morphology of the so‐obtained nanocomposites has been assessed by transmission electron microscopy, scanning electron microscopy, and wide angle X‐ray diffraction, showing a partially exfoliated structure for PHBV/Cloisite® 30B nanocomposites, as well as a good dispersion of the HNT in the PHBV matrix. The crystallinity of the resulting nanocomposites, determined by DSC, does not change when clays or TNPP are added. An increase in the onset temperature of thermal degradation of PHBV has been obtained with the addition of TNPP, as determined by TGA. With regard to the effect of the nanoclays on the thermal stability of PHBV, the onset temperature of the PHBV/HNT nanocomposites is higher than that of the pure PHBV, while this trend is not observed for the nanocomposites containing Cloisite® 30B. The addition of TNPP to the PHBV/Cloisite® 30B nanocomposites resulted in an improved thermal stability; however, for the HNT nanocomposites, the TNPP does not seem to have a significant effect. For all studied systems, it was shown that the variation of mechanical properties of the nanocomposites is due to the reinforcing effect of the nanoclays on the PHBV matrix. In the case of TNPP, it is due to the increased molecular weight and formation of a long‐chain branching structure. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42390.

The use of poly(amide-imide)/CuO as a filler for the preparation of poly(vinyl pyrrolidone) nanocomposites: Thermal and morphological studies

Poly(vinyl pyrrolidone)/poly(amide–imide)–CuO nanocomposites were prepared by adding of poly(amide–imide)–CuO nanocomposite as filler in a poly(vinyl pyrrolidone) matrix via ultrasonication method. First, the surface of CuO nanoparticles was modified with a bioactive coupling agent using the ultrasonic-assisted technique in order to obtain a homogeneous dispersion of CuO nanoparticles in the poly(amide–imide) matrix. Then, modified CuO nanoparticles were dispersed in the poly(amide–imide) matrix. The poly(amide–imide)–CuO nanocomposite was mixed with poly(vinyl pyrrolidone) and the obtained nanocomposites were investigated by Fourier transform infrared and X-ray diffraction spectroscopy techniques. The Fourier transform infrared results indicated interactions between the poly(amide–imide)–CuO nanocomposite and the poly(vinyl pyrrolidone) chain. Thermogravimetric analysis was used to investigate the thermal properties of poly(vinyl pyrrolidone) nanocomposites. Thermogravimetric analysis results illustrated that the thermal stability of poly(vinyl pyrrolidone) is enhanced by adding of nano-filler. The surface topography and morphology of the poly(amide–imide)–CuO nanocomposite and poly(vinyl pyrrolidone)/poly(amide–imide)–CuO nanocomposites were studied by atomic force microscopy, field emission scanning electron microscopy, and transmission electron microscopy techniques. The results showed that the nano-filler was homogeneously dispersed in the polymer matrix.

Effect of electrospun fibers of polyhydroxybutyrate filled with different organoclays on morphology, biodegradation, and thermal stability of poly(ε‐caprolattone)

ABSTRACTThe properties of nanocomposites of poly(ε‐caprolattone) (PCL) were studied, the pristine PCL was implemented with the introduction of electrospun fibers of polyhydroxybutyrate (PHB), containing a cationic (Cloisite) or an anionic (Perkalite) clay. These multicomponent composites containing a very low amount of clay confined in fibers are different from usual nanocomposite materials containing clay dispersed in the polymer matrix, which are produced by solvent casting or melt extrusion. To analyze the influence of the different fillers on the final composite, a preliminary study on PHB cast films and fibers prepared from the same solution was carried out, and then a thorough analysis was accomplished of the behavior of these particular nanocomposites PCL/PHB fibers/clay to elucidate the effects of the filled electrospun fibers on the PCL matrix. The structure and morphology of the samples were characterized by wide‐angle X‐ray diffraction and small angle X‐ray scattering; differential scanning calorimetry and thermogravimetric analysis were used to understand the influence of the fillers on the thermal behavior and stability; mechanical properties were evaluated and biodegradation studies were carried out. The PHB electrospun fibers and the fractured surface of the final composites were examined by scanning electron microscopy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42342.

Enhanced thermal stability of poly(methyl methacrylate) composites with fullerenes

The thermal stability of poly(methyl methacrylate) (PMMA) composites with the two fullerenes C60 and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), was studied over the whole composition range under nitrogen (N2) and air atmosphere using dynamic thermogravimetric analysis (TGA). The aim of this study was to compare the thermal stabilization effect of both fullerenes on PMMA. When compared with pure PMMA, both C60 and PCBM increase substantially the thermal degradation temperature of the corresponding composites, both in nitrogen and air atmospheres. The amounts of C60 and PCBM in the PMMA composites can be successfully determined along the whole composition range using TGA. The initial amounts of fullerene present in the composites correlates linearly with the residual mass values obtained above 450 °C in nitrogen and with the residual mass values observed at the temperatures of transition from the first to the second decomposition steps in air. There are no significant differences between the thermal stabilization effects of C60 and PCBM in both atmospheres (nitrogen and air).

Thermal properties of poly (vinyl alcohol)(PVA)/halloysite nanotubes reinforced nanocomposites

Natural halloysite nano clay with tubular structure was used for the preparation of polyvinyl alcohol (PVA) nanocomposites. A systematic and detailed study was conducted on the effect of nanotubes on the properties such as flame retardancy, water absorption capacity, and thermal stability of poly (vinyl alcohol) matrix. Morphological and structural characterizations of nanocomposites were performed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and fourier transform infra red (FTIR) spectroscopy. XRD results showed peak broadening and disappearance in nanocomposites when compared to the peaks for nanotubes, indicating the better dispersion of nanotubes in the matrix. Owing to the hydrophilicity of nanotubes the nanocomposites exhibited enhanced water sorption properties. At higher temperature nano filler reinforced PVA showed better thermal stability and flammability due to barrier effect.

In situ synthesis of poly(N-vinylimidazole)/montmorillonite nanocomposites using intercalated monomer and thermal properties

A series of poly(N-vinylimidazole)/montmorillonite nanocomposites were prepared by in situ polymerization. This method is the first example of in situ polymerization of VI monomers within the montmorillonite layers for the preparation of nanocomposites at different clay loading degrees. N-vinyl imidazole was first intercalated into the interlayer regions of clay minerals by ion exchange reaction. Then, this organomodified clay was dispersed in the fluid VI monomers at different loading degrees to conduct the in situ polymerization. Polymerization through the interlayer of the clay led to the exfoliated poly(N-vinylimidazole)/montmorillonite nanocomposite formation. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses indicated that the resultant nanocomposites exhibited exfoliated morphologies with homogeneous clay platelet distribution. The PVI/5MMT nanocomposite was selected for the calculation of the decomposition activation energy via the Kissinger method, due to its highest thermal stability. The results showed that activation energy values at both stages for the poly(N-vinylimidazole)/montmorillonite nanocomposite are higher than those of neat poly(N-vinylimidazole), indicating that addition of the clay mineral improves the thermal stability of poly(N-vinylimidazole).

Characterization of Aluminum/Poly(Vinylidene Fluoride) by Thermogravimetric Analysis, Differential Scanning Calorimetry, and Mass Spectrometry

Fluoropolymers have been widely used as oxidizers. In this study, poly(vinylidene fluoride) was employed to oxidize nanoaluminum, and the thermal behavior was investigated by thermogravimetry combined with differential scanning calorimetry and mass spectrometry. The results show that the addition of nanoaluminum significantly decreased the thermal stability of poly(vinylidene fluoride) and that the decomposition of nanoaluminum/poly(vinylidene fluoride) occurred in two temperature ranges. The first from 200 to 280 degree Celsius involved the decomposition of adsorbed water on the nanoaluminum and the reaction of the alumina shell on the surface and dissociative fluoride. The second from 350 to 450 degrees Celsius involved the degradation of poly(vinylidene fluoride) and reaction of nanoaluminum and gas products from the polymer and its matrix. The kinetic process was divided into four steps with apparent activation energies calculated by Kissinger method of 137, 182, 163, and 176 kilojoules per mole, respectively. From evolved gas product analysis, the fluorinated products were identified from the decomposition of poly(vinylidene fluoride) and nanoaluminum/ poly(vinylidene fluoride) composites. However, the intensities of fragments from nanoaluminum/poly(vinylidene fluoride) were lower than those from pure poly(vinylidene fluoride). Other decomposition products included H2, H2O, and OH.

Effects of Halloysite Nanotubes on Mechanical and Thermal Stability of Poly(Ethylene Terephthalate)/Polycarbonate Nanocomposites

The objective of this study is to investigate the effect of halloysite nanotubes (HNTs) loading on mechanical and thermal properties of poly(ethylene terephthalate)/polycarbonate (PET/PC) nanocomposites. Nanocomposites containing 70PET/30PC and 2-8 phr HNTs were prepared by twin screw extruder followed by injection moulding. As the percentage of HNTs increased, the flexural modulus increased. However, the flexural strength decreased with increasing HNTs content. The impact strength also decreased when HNTs increased. Thermogravimetry analysis of PET/PC/HNTs nanocomposites showed higher thermal stability at high HNTs content. However, on further addition of HNTs up to 8 phr, thermal stability of the nanocomposites decreased due to the poor dispersion of HNTs.

Synergistic effects of lanthanum-pentaerythritol alkoxide with zinc stearates and with β-diketone on the thermal stability of poly(vinyl chloride)

Lanthanum-pentaerythritol alkoxide (La-PE) was obtained by the traditional preparation method which was a reaction between La2O3 and pentaerythritol. The synergistic effects of La-PE with zinc stearates (ZnSt2) and with stearoyl benzoyl methane (β-diketone) on the thermal stability of poly(vinyl chloride) (PVC) were evaluated by the conductivity test, thermal aging test, and Ultraviolet–visible (UV-VIS) spectroscopy test. The results showed an improvement on the color stability and the long-term thermal stability of PVC, indicating that there was an obvious synergistic effect between La-PE and ZnSt2. In order to explore the mechanism, the capacity of La-PE to react with HCl was tested. The results showed that La-PE had lower capacity to neutralize HCl (80.30 mg HCl/1 g) than ZnSt2 (92.71 mg HCl/1 g). Furthermore, the thermal stability test of PVC stabilized with La-PE/ZnCl2 showed that the thermal stability of PVC with La-PE/ZnCl2 was similar to that of PVC with La-PE/ZnSt2 but better than PVC with pure La-PE. Thus, a possible synergistic mechanism of La-PE and ZnSt2 could be described where zinc species could catalyze the reaction of La-PE and the labile chlorine atoms in PVC chains. Moreover, the hydroxyl group on La-PE could chelate ZnCl2 to inhibit the “zinc burning” phenomenon. However, there was no synergistic effect observed between La-PE and β-diketone. Discoloration in PVC samples that stabilized with La-PE and β-diketone was noticed as early as in the milling process by the open twin-roller at 180 °C, even though it took 110 min for the reaction to change the color to completely black. The results of UV-VIS spectroscopy showed that a strong peak appeared at 360 nm representing the enol form of β-diketone when the dosage of β-diketone exceeded 1 phr. This indicated that the enol form of β-diketone did the work in the thermal stabilizing process and the dosage of β-diketone needed in the PVC stabilizers was very low.

Studies on Hydrophilicity and Thermal Stability of Poly(isoalkyl lactate methacrylate)s

Isopropyl and isobutyl lactates were reacted with methacrylic acid to obtain corresponding methacrylates through the azeotropic distillation method and their formation was confirmed by mass spectroscopy. Homopolymers were prepared by the solution polymerization method. Both monomers and homopolymers were characterized by FT-IR and NMR spectroscopic techniques. Hydrophilicity of polymers followed the Fickian process and moisture absorption was in the range of 10–24% (w/w). Glass transition temperature decreased with an increase in isoalkyl chain length of polymers. Thermal stability of polymers was explained on the basis of average molecular interchain spacing value, which was calculated using 2θ value of amorphous halo of polymers.

Polymer-Nanoparticle Composites Composed of Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and Coated Silver Nanoparticles

The effects of addition of synthesized organic-suspension silver nanoparticles on the crystallization and thermal stability of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) were studied by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (XRD), UV-Vis absorption spectroscopy, polarized optical microscopy (POM), and thermal gravimetric analysis (TGA). The TEM images showed the average primary size of the as-synthesized silver nanoparticles, coated with a monolayer of the surfactants consisting of oleic acid and an alkylamine, was about 5 nm with narrow distribution, and that they were uniformly dispersed in n-heptane. PHBV/silver nanocomposites were prepared by melt mixing in an internal mixer and then injection molded into rectangle-shaped specimens by a labscale injection molding device. The coated silver nanoparticles showed a homogenuous dispersion in the PHBV matrix when the content of coated silver nanoparticles was about 1%. Both the DSC and POM data showed the efficient heterogeneous nucleation by the coated silver nanoparticles for facilitating PHBV crystallization. The thermal stability of the PHBV/silver nanocomposites improved with the increase in the content of the coated silver nanoparticles.

폴리염화비닐(PVC)의 열안정성에 제올라이트가 미치는 영향

The effects of zeolite on the thermal stability of poly(vinyl chloride) (PVC) were investigated by the static thermal stability test, pyrolysis experiment and ultraviolet spectrum. The results showed that the porous zeolite could absorb hydrogen chloride (HCl), which suppressed the catalysis of HCl on thermal degradation of PVC, thus improved the thermal stability of PVC. The oxidizing acid which was loaded on zeolite had oxidated on the double bond that formed during the dehydrochlorination of PVC. This process could prohibit the growth of the conjugated polyene and improved the color of PVC. Hence, zeolite might be possible to come up with a high performance thermal stabilizer.

Structures of LDHs Intercalated with Ammonia and the Thermal Stability for Poly(vinyl chloride)

MgAl-NH3 LDHs (layered double hydroxides), ZnAl-LDHs and ZnAl-NH3 LDHs with different molar ratio of Al/ammonia were synthesized by co-precipitation method. The synthetic LDHs samples were characterized by XRD, FT-IR, TGA-DTG and SEM techniques and tested by Congo red method. In addition, after PVC (Poly vinyl chloride) and DOP (Dioctylphthalate) were added to LDHs, the thermal stability for PVC was characterized by TGA-DTG. The results indicated that LDHs intercalated with ammonia improved thermal stability for PVC significantly, MgAl-NH3 LDHs (Mg2+:Al3+: NH3·H2O = 3:1:0.5) and ZnAl-NH3 LDHs (Zn2+:Al3+:NH3·H2O=2:1:1.5) showed the best thermal stability for PVC, interlayered space of LDHs became larger by intercalating ammonia.

Structural effects of diamines on synthesis, polymerization, and properties of benzoxazines based on o-allylphenol

Two allyl-containing bifunctional benzoxazines (oAP-hda and oAP-dds) were synthesized from o-allylphenol, formaldehyde, and two diamines [1,6-hexamethylenediamine (HDA) and 4,4′-diaminodiphenyl sulfone (DDS)]. The chemical structures of oAP-hda and oAP-dds were confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. The reactivity of HDA is higher than that of DDS in the synthetic reaction of benzoxazines, and the polymerization temperature of oAP-hda is lower than that of oAP-dds. The structure changes from benzoxazines to their corresponding polybenzoxazines [Poly(oAP-hda) and Poly(oAP-dds)] were studied by FTIR and solid state 13C NMR. The dynamic mechanical properties and thermal stabilities of Poly(oAP-hda) and Poly(oAP-dds) were studied by dynamic mechanical analysis and thermogravimetry, respectively. The storage moduli in the glassy state are 1.44 and 3.18 GPa for Poly(oAP-hda) and Poly(oAP-dds), respectively, and the glass transition temperatures are 87 and 193 °C, respectively. The thermal stability of Poly(oAP-dds) is much higher than that of Poly(oAP-hda).

Effect of zinc maleate/zinc oxide complex on thermal stability of poly(vinyl chloride)

ABSTRACTIn this study, zinc maleate (ZnMA) and zinc oxide (ZnO) complex (ZnMA/ZnO) was prepared by two methods, namely, by the reaction of maleic acid (MAH) with excess ZnO in aqueous solution and by direct mixing of ZnMA and ZnO at 180°C. The chemical structure of the complex was analyzed by X‐ray diffraction, thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy. The thermal stabilizing effect of the complex on poly(vinyl chloride) (PVC) was evaluated through static and dynamic stability methods. Compared to calcium and zinc soaps and ZnMA alone, the complex exhibited better thermal stabilizing effect on PVC. The stabilization mechanism was also investigated by ultraviolet–visible spectrometer, FTIR, TGA, and gel content analysis. The results indicated that the complex which involved the replacement of labile chlorine atoms hindered the formation of conjugated double bonds in PVC chains via Diels–Alder reaction, and ZnMA/ZnO complex also exhibited the ability to absorb hydrogen chloride. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41464.

Effect of allantoin on the stabilization efficiency of Ca–Zn thermal stabilizers for poly(vinyl chloride)

The influence of allantoin (ALL) combined with zinc stearate (ZnSt2), calcium stearate (CaSt2), and ZnSt2–CaSt2 (1:1), respectively, in different mass ratios on thermal stability of poly(vinyl chloride) (PVC) was investigated by Congo red test, discoloration test, and thermogravimetric analysis. The results indicated that ALL behaved as a good long-term thermal stabilizer for PVC, which was attributed to its ability to absorb hydrogen chloride released from the degradation of PVC. Moreover, ALL was able to extend the stabilization time of PVC containing ZnSt2–CaSt2 and postpone “zinc burning.” Fourier transform infrared spectra confirmed that ALL can react with ZnCl2 to produce an inert complex, which is responsible for postponing “zinc burning.”

Synergetic effect of LaB6 and ITO nanoparticles on optical properties and thermal stability of poly(vinylbutyral) nanocomposite films

In this work, different compositions of lanthanum hexaboride (LaB6) and tin-doped indium oxide (ITO) nanoparticles were doped into poly(vinylbutyral) (PVB) matrix to prepare PVB/LaB6–ITO nanocomposite (PLINC) films by a solution casting method. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, thermogravimetric analysis (TGA) and ultraviolet–visible–near infrared spectroscopy (UV–vis–NIR) were employed to characterize the PLINCs. The TGA and UV–vis–NIR results reveal that the nanocomposite films possessed outstanding thermal stability. The temperature where 5 % weight loss of the PVB matrix was improved after the addition of LaB6 and ITO particles and the property for blocking near infrared light was also enhanced as compared with the case of pure PVB film.

Biodegradable Plastics Prepared from Poly(lactic acid), Poly(butylene succinate) and Microcrystalline Cellulose Extracted from Waste-Cotton Fabric with a Chain Extender

This study aimed to improve the brittleness and thermal stability of poly(lactic acid) (PLA) by inclusion of poly(butylene succinate) (PBS) and microcrystalline cellulose (MCC). Of the three PLA/PBS blends (10, 30 and 50 wt% PBS) evaluated, the 70/30 wt% blend exhibited the highest impact strength and elongation at break, but a lower thermal stability compared to that of the pure PLA. Scanning electron microscopy analysis confirmed the better compatibility of this 70/30 PLA/PBS blend. This blend was further filled with MCC. Based on thermogravimetric analysis, the thermal stability of the 70/30 PLA/PBS blend was improved by the addition of MCC [optimal at five parts by weight per hundred (phr)] and further still by the addition of the chain extender, Joncryl™, at 0.5 phr. The 70/30/5/0.5 PLA/PBS/MCC/Joncryl™ composite exhibited the highest impact strength, while the elongation at break was acceptable.

Thermal stability of modified end‐capped poly(lactic acid)

ABSTRACTThe influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41105.