Onset Temperature Of Thermal Degradation Research Articles

Mechanical and thermal properties of EVA blended with biodegradable ethyl cellulose

AbstractIn this study, biodegradable blend of Poly (Ethylene‐co‐Vinyl Acetate) (EVA) and Ethyl Cellulose (EC) were prepared. Ethylene vinyl alcohol (EVOH) copolymer was used as an interfacial compatibilizer to enhance adhesion between EVA and EC. The melt blended compatibilized biocomposites were examined for mechanical and thermal properties as per the ASTM standards. It has been found that the EC has a reinforcing effect on EVA leading to enhanced tensile strength and also impart biodegradability. Thus, a high loading of 50% EC could be added without compromising much on the mechanical properties. Analysis of the tensile data using predictive theories showed an enhanced interaction of the dispersed phase (EC) and the matrix (EVA). The compatibilizing effects of EVOH on these blends were confirmed by the significant improvement in the mechanical properties comparable with neat EVA as also observed by SEM microscopy. The TGA thermograms exhibits two‐stage degradation and as EC content increases, the onset temperature for thermal degradation reduces. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Influences of organic-modified Fe-montmorillonite on structure, morphology and properties of polyacrylonitrile nanocomposite fibers

The Fe-montmorillonite (Fe-MMT) combined catalysis effects of Fe ion with barrier effects of silicate clays, was firstly synthesized by hydrothermal method, and then was modified by cetyltrimethyl ammonium bromide (CTAB). The organic-modified Fe-montmorillonite (Fe-OMT) was dispersed in the N, N-dimethyl formamide (DMF) and then compounded with polyacrylonitrile (PAN) solution which was dissolved in DMF. The composite solutions were electrospun to form PAN/Fe-OMT nanocomposite fibers. The influences of the Fe-OMT on the structure, morphology, thermal, flammability and mechanical properties of PAN nanocomposite fibers were respectively characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), Scanning electron microscopy (SEM), Thermogravimetric analyses (TGA), Micro Combustion Calorimeter (MCC) and Electronic Single Yarn Strength Tester. It was found from XRD curves that there was not observable diffraction peak of silicate clay, indicating that the silicate clay layers were well dispersed within the PAN nanofibers. The HRTEM image indicated that the multilayer stacks of nanoclays could be found within the nanofibers and were aligned almost along the axis of the nanofibers. The SEM images showed that the diameters of nanocomposite fibers were decreased with the loading of the Fe-OMT. The TGA analyses revealed that the onset temperature of thermal degradation and charred residue at 700°C of PAN nanocomposite fibers were notably increased compared with the pure PAN nanofibers, contributing to the improved thermal stability properties. It was also observed from MCC analyses that the decreased peak of heat release rate (PHRR) of the PAN nanocomposite fibers reduced the flammability properties. The loadings of Fe-OMT increased the tensile strength of PAN nanocomposite fibers, but the elongation at break of PAN nanocomposite fibers was lower than that of the PAN nanofibers.

Thermal and Mechanical Analysis of Cross-Linked Optical Fiber Coatings

A convenient route to enhancing the thermal degradation on-set temperature of existing commercial optical fiber coatings is presented. UV curable acrylate coatings were modified through the addition of a multi-functional cross-linking agent and are shown to increase their degradation temperature by 65degC without any degradation in the mechanical or optical properties of the resultant fiber. Such enhanced thermal robustness in coatings is important for optical fiber applications in high energy laser (HEL) systems and selected higher temperature sensing environments.

Supercritical carbon dioxide-assisted solid-phase free radical grafting of butyl acrylate onto PP

AbstractFree radical grafting copolymerization of butyl acrylate (BA) onto polypropylene (PP) matrix was investigated using supercritical CO2 as a swelling agent and carrier solvent. The monomer BA and initiator AIBN were first dissolved in supercritical CO2, and then these small molecules were diffused into the grafting zones of PP matrix. As grafting reaction temperature (about 80 °C) was far below the melting point, PP was modified in the solid phase. The effects of different experimental conditions such as soaking time and temperature, supercritical CO2 pressure; monomer and initiator concentration; PP particle diameter; solid phase grafting reaction time and temperature on grafting percentage were studied. Fourier transform infrared spectroscopy (FTIR) results and gel content experiment prove that the monomers were indeed grafted onto PP chains. Scanning electron microscope (SEM) analysis of the grafted sample indicates that the grafting branches PBA were homogeneously distributed onto the surfaces and micropores of PP particles. Thermal gravimetric analysis (TGA) results show that the grafted samples had a higher onset thermal degradation temperature and a lower weight loss at a particular temperature than pure PP. The water contact angle of PP-g-BA decreased from 98° to 72°, indicating the polarity and hydrophilicity of PP were improved effectively. The melt flow rate (MFR) and mechanical analysis results show that the grafting sample remained its versatile physical properties though introducing the grafting BA branch chain. This is prominent when it was compared with normal solid grafting product.

COPOLYMERIZATION OF FURFURYL GLYCIDYL ETHER AND CARBON DIOXIDE

To explore the non-petroleum route for carbon dioxide copolymers,furfuryl glycidyl ether oxirane with 99.7% purity was prepared from furfuryl alcohol and epichlorohydrin employing sodium hydroxide and tert-butylammonium sulfate as catalysts,where furfuryl alcohol was a hydrogenation product of furfural from pentose-rich agricultural residues like rice hulls,bagasse,corn cob,et al.,and epichlorohydrin could be produced from glycerine which was a byproduct in bio-diesel production.Copolymerization of carbon dioxide and furfuryl glycidyl ether was carried out in a 500 mL autoclave with carbon dioxide pressure of 4 MPa at elevated temperatures,using Y(CCl_3COO)_3-glycerine-ZnEt_2 coordination catalyst and 1,4-dioxane as solvent.Aliphatic polycarbonate with pendant furfuryl methyl ether was obtained with number average molecular weight as high as 13.0×104.The glass transition temperature(T_g)of the resultant copolymer was around-30℃,which was 65℃ lower than that of poly(propylene carbonate)(PPC),providing possibility for solving the brittleness of PPC,and the application window of PPC was therefore enlarged to lower temperature range.Compared with common PPC,this new polycarbonate showed significant improvement in thermal stability,the onset thermal degradation temperature(T_d)of the copolymer was 231℃,approximately 60℃ higher than that of PPC.

Thermal degradation behaviour of multi‐walled carbon nanotube‐reinforced poly(L‐lactide) nanocomposites

AbstractBACKGROUND: Polymer/multi‐walled carbon nanotube (MWCNT) composites are one of the most promising alternatives to conventional polymer composites filled with micrometre‐sized fillers. This approach can also be applied for the improvement of mechanical properties and thermal stability of biodegradable aliphatic polyesters, such as poly(L‐lactide) (PLLA), which have been receiving increasing attention due to environmental concerns. Thermal degradation behaviour provides useful information for the determination of the optimum processing conditions and for identification of potential applications of final products.RESULTS: The PLLA/MWCNT composites investigated showed a higher thermal degradation peak temperature and onset temperature of degradation along with a higher amount of residue at the completion of degradation than neat PLLA. Moreover, PLLA/MWCNT composites with a greater MWCNT content showed higher activation energy of thermal degradation than those with a lower MWCNT loading, which confirmed the positive effect of MWCNT incorporation on the enhancement of PLLA thermal stability.CONCLUSION: This study explored the thermal degradation behaviour of PLLA/MWCNT composites by observing the weight loss, molecular weight and mechanical properties during non‐isothermal and isothermal degradation. The incorporation of MWCNTs into the PLLA matrix enhanced considerably the mechanical properties and thermal stability. Copyright © 2009 Society of Chemical Industry

Waterborne Polyurethane Coating and its New Applications in Plush Finishing

In this paper the anionic waterborne polyurethane (WPU) was prepared from poly(propylene) glycol, 4,4′-diphenylmethane diisocyanate, dimethylol propionic acid, and butanediol. Triethylamine was used as a neutralization agent. The chemical structure of the WPU was characterized by Fourier transform infrared spectrometry (FTIR), which demonstrated that the sample with expected structure had been synthesized. The thermal properties of the WPU were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC results demonstrate that the glass transition temperature of the WPU is much lower than that of the commercially used acrylate resin (PA). TGA results show that the onset temperature of thermal degradation for the WPU is 265°C. The dispersion was used as a coating material for plush finishing. The adhesive properties of the WPU to the plush were evaluated by scanning electron microscopic (SEM) observation and depilation ratio test. The results indicate that the adhesion and handle of the WPU to the plush is much better than that of the PA emulsion.

Morphological and rheological characterization of multi-walled carbon nanotube/PLA/PBAT blend nanocomposites

Biodegradable poly (lactic acid) (PLA)/poly (butyleneadipate-co-butyleneterephthalate) (PBAT)/multi-walled carbon nanotube (MWNT) polymer blend nanocomposites were prepared by using a laboratory-scale twin-screw extruder. Fractured surface morphology of the polymer blend/MWNT nanocomposites were examined via SEM. Furthermore, cross sectioned samples obtained using an ultramicrotome was observed via TEM. In addition, effects of both MWNT reinforcement and phase affinity of MWNT on thermal and rheological properties of the PLA/PBAT blends were investigated by TGA and rotational rheometer. Immiscible PLA/PBAT blend with MWNT nanocomposites showed two-step thermal degradation. The onset temperature of thermal degradation started in the PLA much earlier than in the PBAT. Nonetheless, based on TGA data, it was found that the MWNT enhanced thermal property of the PLA/PBAT blend/MWNT nanocomposites. Rheological properties revealed that both shear and complex viscosities showed unique shear thinning behavior due to selectively localized MWNT dispersion state.

Comparison Between Structures and Properties of ABS Nanocomposites Derived from Two Different Kinds of OMT

In the present work, the hexadecyl triphenyl phosphonium bromide (P16) and cetyl pyridium chloride (CPC) were used to modify montmorillonite (MMT) based on the structural characteristic of the engineering thermoplastic acrylonitrile-butadiene-styrene copolymer (ABS) and the principle of “like dissolves like”, and then used to prepare the ABS/organic-modified montmorillonite (OMT) nanocomposites by melt-intercalation method. The influences of two different kinds of OMT on the structures and properties of the ABS nanocomposites were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HREM), thermogravimetric analyses (TGA), Cone calorimetry and dynamic mechanical analyses (DMA), respectively. The increased basal spacing showed that ABS intercalated into the gallery of the OMT. The morphology indicated that the OMT dispersed well in the ABS resin and the intercalated structure for ABS/OMT-P16 nanocomposites and intercalated-exfoliated structure for ABS/OMT-CPC nanocomposites were respectively formed. The TGA results revealed that onset temperature of thermal degradation and charred residue at 700 °C of the ABS nanocomposites was remarkably enhanced compared to the pure ABS. It was also found from the Cone calorimetry tests that the peak of heat release rate (PHRR) decreased significantly, contributing to the reduced flammability. The DMA measurements indicated that the loading of silicate clays improved the storage modulus of the ABS resin. The partial exfoliation of the OMT-CPC within ABS nanocomposites was advantageous to increasing thermal stability properties, decreasing flammability properties, and improving mechanical properties.

Comparison Between Effects of Two Different Cationic Surfactants on Structure and Properties of HIPS/OMT Nanocomposites

The high impact polystyrene (HIPS)/organophilic montmorillonite (OMT) nanocomposites were prepared by melt-mixing. The hexadecyl triphenyl phosphonium bromide (P16) and cetyl pyridium chloride (CPC) were used to modify montmorillonite (MMT). The structure and thermal stability property of the OMT were respectively characterized by Fourier transfer infrared (FTIR) spectra, X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results indicated that the cationic surfactants intercalated into the gallery of the MMT and the OMT had higher thermal stability. The influences of two different OMT on the structures and properties of the HIPS nanocomposites were characterized by XRD, TGA, Cone calorimeter and dynamic mechanical analysis (DMA), respectively. The increased basal spacing showed that HIPS intercalated into the gallery of the OMT. The TGA showed that onset temperature of thermal degradation, temperature of maximal weight loss and char residue at 700°C of the HIPS nanocomposites had remarkable enhancements compared to pure HIPS. The Cone calorimeter tests showed that the peak of heat release rate (PHRR) decreased significantly. The DMA indicated that the loading of silicate clays improved the storage modulus of HIPS.

Relationship between processing conditions, defects and thermal degradation of poly(vinylidene fluoride) in the β-phase

Poly(vinylidene fluoride), PVDF, in its β-phase is an electroactive polymer with many technological applications. There are two main ways to prepare this polymer in its electroactive β-phase: by high temperature stretching from the α-phase and directly from solution. In this paper, the influence of the processing methods in the thermal stability of the samples was studied by UV–VIS spectroscopy and thermogravimetric analysis. The number of chain defects was measured by 1H NMR. The results obtained were compared to a commercial β-PVDF sample. The number of head to head defects in the different samples is found to be between 6% and 9%. The onset temperature for thermal degradation and the average activation energy (∼76.5 kJ mol −1) of the process are approximately equal for the α-phase sample and the β-phase obtained from it. Larger values of the onset temperature and average activation energy (∼100 kJ mol −1) are found for the β-phase sample directly obtained from the solution and for the commercial β-phase sample. The thermal degradation of the samples occurs in two steps, independently of the phase of the sample, the degree of crystallinity and the processing method.

Preparation and characterization of conductive poly(vinyl alcohol)/polyaniline doped by dodecyl benzene sulfonic acid (PVA/PANDB) blend films

AbstractIn this study a solution‐blend method is adopted to prepare conductive poly(vinyl alcohol)/polyaniline doped by dodecyl benzene sulfonic acid (PVA/PANDB) blend films. Emeraldine base (EB)‐type polyaniline (PANI) is dissolved in N‐methyl‐2‐pyrrolidinone (NMP) and then blended with PVA/dodecyl benzene sulfonic acid (DBSA) solution by various amounts. It is found that the electrical conductivity and the thermal degradation onset temperature of the PVA/PANDB blend film are increased as the amount of EB‐type PANI solution is increased. Fourier transform infrared (FTIR) spectra show that the intensity of the characteristic peak of the functional groups in the blend film is significantly changed as the amount of EB‐type PANI is changed. From optical microscopy examination, it indicates that the amount and size of green particles are increased with increasing the amount of EB‐type PANI solution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3415–3422, 2007

Influence of Fe‐MMT on crosslinking and thermal degradation in silicone rubber/clay nanocomposites

AbstractIn this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd.

Poly(4-nitrophenyl)quinoxalines

Via the reaction of 4,4-bis(4-nitrophenylglyoxalyl)diphenyl ether with different bis(o-phenylenediamine)s, new poly(4-nitrophenyl)quinoxalines were synthesized, which are of interest as precursors for polymers containing protogenic groups. Some properties of the obtained polymers were studied. It was shown that the solubility of poly(4-nitrophenyl)quinoxalines in organic solvents and their viscosity characteristics are comparable with the parameters of polyphenylquinoxalines that do not bear nitro groups. A study of the thermal properties of the polymers showed that the introduction of nitro groups into polyphenylquinoxalines is accompanied by some increase in the glass transition temperature and a decrease in the onset temperature of runaway thermal degradation.

Study on mechanical properties, thermal stability and crystallization behavior of PET/MMT nanocomposites

PET/montmorillonite (MMT) nanocomposites were prepared via melt-blending and its nano-dispersion morphology was confirmed by X-ray diffraction and transmission electron microscopy. Its non-isothermal crystallization behavior was studied by DSC. It is found that the crystallization rate of PET nanocomposite was increased significantly. The Avrami equation parameters related to crystallization, such as n, Z c and t 1/2, were calculated and analyzed. The thermal property and mechanical property of the composite were studied. When the MMT content was 1%, the composite has a desired comprehensive property. At this composition, the thermal degradation onset temperature and the thermal deformation temperature of PET were increased by 12 and 35 °C, respectively, and the tensile strength of the PET was increased by 25% with slightly increase of the notched impact strength.

Synthesis of Degradable Polymer Exhibiting LCST-type Phase Separation by Radical Copolymerization of Sorbic Esters and Molecular Oxygen

Abstract We synthesized water-soluble polyperoxides (PP) by radical copolymerization of hydrophilic sorbic esters with oxygen. A phase separation with a lower critical solution temperature (LCST) was observed under the onset temperature of thermal degradation for the aqueous solutions of PP containing a tetra(ethylene oxide) unit in the side chain. A critical temperature for the LCST-type phase separation depended on the composition of the hydrophilic and hydrophobic esters of PP.

Effects of microscale calcium carbonate and nanoscale calcium carbonate on the fusion, thermal, and mechanical characterizations of rigid poly(vinyl chloride)/calcium carbonate composites

AbstractA Haake torque rheometer equipped with an internal mixer has been used to study the influence of microscale calcium carbonate (micro‐CaCO3) and nanoscale calcium carbonate (nano‐CaCO3) on the fusion, thermal, and mechanical characteristics of rigid poly(vinyl chloride) (PVC)/micro‐CaCO3 and PVC/nano‐CaCO3 composites, respectively. The fusion characteristics discussed in this article include the fusion time, fusion temperature, fusion torque, and fusion percolation threshold (FPT). The fusion time, fusion temperature, and FPT of rigid PVC/calcium carbonate (CaCO3) composites increase with an increase in the addition of micro‐CaCO3 or nano‐CaCO3. In contrast, the fusion torque of rigid PVC/CaCO3 composites decreases with an increase in the addition of micro‐CaCO3 or nano‐CaCO3. The results of thermal analysis show that the first thermal degradation onset temperature (Tonset) of rigid PVC/micro‐CaCO3 is 7.5 °C lower than that of PVC. Meanwhile, the glass‐transition temperature (Tg) of rigid PVC/micro‐CaCO3 is similar to that of PVC. However, Tonset and Tg of PVC/nano‐CaCO3 composites can be increased by up to 30 and 4.4%, respectively, via blending with 10 phr nano‐CaCO3. Mechanical testing results for PVC/micro‐CaCO3 composites with the addition of 5–15 phr micro‐CaCO3 and PVC/nano‐CaCO3 composites with the addition of 5–20 phr nano‐CaCO3 are better than those of PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 451–460, 2006

Fusion, electrical conductivity, thermal, and mechanical properties of rigid poly(vinyl chloride) (PVC)/carbon black (CB) composites

AbstractRigid and conductive poly(vinyl chloride) (PVC)/carbon black (CB) composites were prepared in a Haake torque rheometer. The results illustrate that the fusion torque of the PVC/CB composite is increased as the amount of CB is increased. Both the fusion percolation threshold and the fusion time of PVC/CB composites are decreased when the amount of CB is increased. Two major weight loss stages are observed in the TGA curve of PVC/CB composite. The first thermal degradation onset temperature (Tonset1) of PVC/CB composite is decreased as the amount of CB is increased. Both the first and second weight loss stages (ΔY1 and ΔY2) of PVC/CB composites are decreased as the amount of CB is increased. The surface resistivity of PVC/CB composite remains almost constant up to 6 parts per hundred unit weight of resin (phr) CB. When the amount of CB in PVC/CB composite is increased from 6 to 15 phr, the surface resistivity of PVC/CB composite is dramatically decreased from 1010 Ω/sq to 104 Ω/sq. Because of the addition of CB, the rigidity of PVC/CB composite is increased and thus the mechanical properties, such as yield strength, tensile strength, and the Young's modulus, are improved. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006

Preparation of polystyrene/montmorillonite nanocomposites using a new radical initiator-montmorillonite hybrid via in situ intercalative polymerization

Polystyrene/montmorillonite (PS/MMT) nanocomposites were prepared by in situ free radical intercalative polymerization, using 1, 3 and 5 wt% of a new cationic radical initiator-MMT hybrid. The corresponding nanocomposites were designated as PS/MMT-1, PS/MMT-3 and PS/MMT-5, respectively. The silicate layers were well exfoliated and randomly dispersed in the PS/MMT-1 and PS/MMT-3, but were less exfoliated in the PS/MMT-5, due to the predominant extra-gallery polymerization over the intra-gallery polymerization. The unique properties of nanocomposites resulted from the strong interactions between the nano-sized silicate layer surfaces and the polymer chains. The onset temperature of thermal degradation, and the glass transition temperature, increased with increasing hybrid content, up to 3 wt%. The molecular weights of the PS in the PS/MMT-1 and PS/MMT-3 were less than those calculated theoretically, due to the predominant intra-gallery polymerization.

Deacetylation of β‐chitin. I. Influence of the deacetylation conditions

AbstractThe influences of the deacetylation temperature, deacetylation time, and NaOH concentration on the degree of deacetylation (DD) of deacetylated products prepared from β‐chitin are discussed. The DD values of deacetylated products are related to the ratio of the signal intensities of methyl on acetyl groups and the first anomeric carbon, which are obtained from 13C‐NMR spectra. The results show that the DD values of deacetylated product increase as the NaOH concentration, deacetylation time, or deacetylation temperature increases. The thermal properties, chemical structures, and crystalline characteristic of deacetylated products are significantly related to their DD values. Differential scanning calorimetry shows that the peak temperature is slightly increased as the DD values of deacetylated products of β‐chitin increase. Thermogravimetric analysis shows that the thermal degradation onset temperature of deacetylated products decreases as the DD values increase. Fourier transform infrared spectra show that the intensity of a specific absorption peak of NH2 in deacetylated products significantly increases as DD increases. X‐ray diffraction patterns of deacetylated products with DD values of 17.5 and 44.7% have three significant diffraction peaks. However, there are only two diffraction peaks found in products with higher DD values of 76.5 and 94.7%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2416–2422, 2004