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1.
Effect of heating rate, Pd content, and synthesis method on the thermal stability of the ex situ and in situ Palladium/polycarbonate (Pd/PC) nanocomposites was investigated. TEM images revealed discrete Pd nanoclusters of about 5 and 15 nm sizes for 1 and 2 vol % ex situ nanocomposites, respectively. However, agglomerated Pd nanoclusters were noticed in the in situ samples, irrespective of the Pd content. The ex situ Pd/PC nanocomposites showed high onset temperature (Ti) for thermal degradation of PC than the in situ and pure PC samples. Pd content and heating rates were found to have a positive influence on the Ti and Tm (temperature at the maximum degradation rate occurs) of the Pd/PC nanocomposites. Thermal degradation of the PC was found to follow the first‐order kinetics in the Pd/PC nanocomposites. The activation energies associated with the degradation were determined by using the Kissinger method. These activation energies are used to construct the Master decomposition curve (MDC) and weight–time–temperature (α–tT) plots that describe the time‐temperature dependence of the PC pyrolysis in the Pd/PC nanocomposites. These constructed α–tT plots were validated with the data from isothermal measurements. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

2.
Polycarbonate (PC)/nanosilica (nSiO2) nanocomposites were prepared by melt‐blending technique, in which surfactants are used to enhance the interfacial adhesion between nSiO2 and polymer matrix. Mechanical properties demonstrate increased Young's modulus and yield strength of modified PC/nSiO2 nanocomposites when compared with PC. Increased compatibility further indicates an effective increase in thermal stability as observed from thermogravimetric analysis. Dynamic mechanical analysis point out a reduction in Tg value with increased storage modulus. The flammability characteristics of PC/nSiO2 nanocomposites were evaluated using limiting oxygen index, whereas the morphological properties are characterized by wide‐angle X‐ray diffraction and scanning electron microscopy. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers  相似文献   

3.
The present work focuses on the morphology and properties of polycarbonate (PC)/clay nanocomposites prepared through melt blending and solution blending at two different loadings of organoclay (0.5 and 1 phr). The oraganoclay was prepared by incorporating thermally 2‐oxopropyl triphenyl phosphonium ion (OTPP) into the clay gallery with an intention to preserve the optical transparency of PC in the PC/clay nanocomposites. An increase in gallery height from 1.24 to 1.86 nm along with the extraordinary thermal stability (∼1.34% wt loss at 280°C, after 20 min) of the OTPP modified montmorillonite (OTPP‐MMT) made it suitable for retention of optical transparency of PC and delamination of the clay platelets in the nanocomposites. The morphological analysis revealed that the clay platelets were randomly dispersed into the PC matrix. An increase in glass transition temperature (Tg) as well as thermal stability of the PC in the nanocomposites was evident from thermal analysis. The strength and modulus of PC increased extensively with increase in OTPP‐MMT loading in the nanocomposites. The nanocomposites were found to retain optical transparency of PC without generation of any color in both the blending technique. POLYM. COMPOS., 199–212, 2016. © 2014 Society of Plastics Engineers  相似文献   

4.
In the present research, poly(acrylonitrile‐butadiene‐styrene)/polycarbonate (ABS/PC) blends were prepared in a twin screw extruder. An attempt to reinforce and promote compatibility of the above systems was made by the incorporation of organically modified montmorillonite (OMMT, Cloisite 30B), as well as by the addition of compatibilizer (ABS grafted with maleic anhydride, ABS‐g‐MAH), and the effect of those treatments on the morphology, thermal transitions, rheological, and mechanical properties of the above blends was evaluated. The addition of compatibilizer in ABS/PC blends does not significantly affect the glass transition temperature (Tg) of SAN and PC phases, whereas the incorporation of Cloisite 30B decreases slightly the Tg values of SAN and, more significantly, that of PC in compatibilized and uncompatibilized blends. The Tg of PB phase remains almost unaffected in all the examined systems. The obtained results suggest partial dissolution of the polymeric components of the blend and, therefore, a modified Fox equation was used to assess the amount of PC dissolved in the SAN phase of ABS and vice versa.Reinforcing with OMMT enhances the miscibility of ABS and PC phases in ABS/PC blends and gives the best performance in terms of tensile strength, modulus of elasticity, and storage modulus, especially in 50/50 (w/w) ABS/PC blends. The addition of ABS‐g‐MAH compatibilizer, despite the improvement of intercalation process in organoclay/ABS/PC nanocomposites, did not seem to have any substantial effect on the mechanical properties of the examined blends. POLYM. COMPOS., 35:1395–1407, 2014. © 2013 Society of Plastics Engineers  相似文献   

5.
Impact behaviours, tensile properties and fracture performance of polycarbonate (PC)/styrene ethylene-butylene-styrene-grafted-maleic anhydride (SEBS-g-MA) copolymer blends at SEBS-g-MA volume fraction Φd = 0–0.39 are evaluated. In presence of rubber a significant augmentation in notched Izod impact strength was observed while tensile modulus and strength decreased. Morphological studies reveal good interaction between the PC and the rubber particles showing homogeneous dispersion of SEBS-g-MA in the polycarbonate matrix. Interparticle distance of the dispersed phase evaluated from the morphology studies by scanning electron microscopy (SEM) and the impact strength dependence on the concentration of the blending rubber were analysed. The essential work of fracture approach is applied to study fracture properties of the blends. With increasing SEBS-g-MA concentration nonessential or plastic work increased which explained the enhancement of impact strength of blends.  相似文献   

6.
A series of crysnanoclay-loaded thermoplastic polyurethane (TPU) elastomer/polycarbonate (PC) nanocomposites have been prepared using twin screw extruders. The physicomechanical properties such as tensile behaviors, flexural properties and impact strength of the composites have been reported. Significant improvement in tensile modulus and flexural modulus were noticed for nanocomposites. The thermal characteristics of nanocomposites have been determined by thermogravimetric analysis (TGA) techniques. Thermal degradation kinetic parameters such as energy of activation (Ea) have been calculated from TGA thermograms for the nanocomposites using three mathematical models namely; Coats–Redfern, Horowitz – Metzger and Broido's methods and the results are compared. The effect of crysnanoclay on the storage modulus (E′), loss modulus (E″), and damping factor (tan δ) as a function of temperature have been measured by dynamic mechanical analysis (DMA). The storage moduli of nanocomposites have been increased after incorporating crysnanoclay in polymer matrix.  相似文献   

7.
Film formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (Tg) temperature of polystyrene. Scattered light (Is) and fluorescence intensity (IP) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T0, and healing temperatures, Th, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers  相似文献   

8.
Polyimide/multi‐walled carbon nanotube (PI‐MWNT) nanocomposites were fabricated by an in situ polymerization process. Chemical compatibility between the PI matrix and MWNTs is achieved by pretreatment of the carbon nanotubes in a mixture of sulfuric acid and nitric acid. The dispersion of MWNTs in the PI matrix was found to be enhanced significantly after acid modification. The glass transition (Tg) and decomposition (Td) temperature of PI‐MWNT nanocomposites were improved as the MWNT content increased from 0.5 to 15 wt%. The storage modulus of the PI/MWNT nanocomposites is nine times higher than that of pristine PI at room temperature. The tensile strength of PI doubles when 7 wt% MWNTs is added. The dielectric constant of the PI‐MWNT nanocomposites increased from 3.5 to 80 (1 kHz) as the MWNT content increased to 15 wt%. The present study demonstrates that enhanced mechanical properties can be obtained through a simple in‐situ polymerization process. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers  相似文献   

9.
Blends of polycarbonate (PC) and poly(alkylene terephthalate) (PAT) such as poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) were investigated. It was learned that processes of phase separation in blends consisting of PC and PAT can cause variations in properties of both the amorphous and crystalline phases. In PC/PBT blends the DSC technique did not detect crystalline portion of PBT with its concentrations up to 20 wt %. For PBT = 40 wt %, it forms a continuous phase, and blend's crystallinity is close to the additive values. The glass transition temperature (Tg) shifts to the lower temperature region. The relaxation spectrometry revealed strong adhesion between phases in the blends over the temperature range from the completion of β‐transition to TgPAT. This interaction becomes weaker between TgPAT and TgPC. Temperature‐dependent variations in the molecular mobility and interphases interactions in the blends affect their impact strength. Over the temperature range where interphases interactions occur and the two components are in the glassy state, the blend is not impact resistant. Over the temperature range between TgPAT and TgPC the blends become impact‐resistant materials. This is because energy of crack propagation in the PAT amorphous phase—being in a high‐elastic state—dissipates. It is postulated that the effect of improving the impact strength of PC/PAT blends, which was found for temperatures between the glass transition temperatures of the mixed components, is also valid for other binary blends. © 2002 Wiley Perioodicals, Inc. J Appl Polym Sci 84: 1277–1285, 2002; DOI 10.1002/app.10472  相似文献   

10.
New clay‐reinforced polymer nanocomposites based on poly(carbonate of bisphenol A) (PC)/poly(caprolactone) (PCL) blends have been obtained by mixing PC with minor amounts of PCL in which a widely dispersed organically modified montmorillonite (OMMT) was present. Upon the addition of PCL/OMMT, the Tg of the matrix and the viscosity of the nanocomposites decreased and therefore processability increased. This was attributed to both the presence of PCL and the migration of some surfactant to the polymeric matrix. The intercalation level observed by X‐Ray diffraction was similar to that obtained in PC nanocomposites, and the dispersion level was at least similar, as observed directly by transmission electron microscopy and indirectly by modulus measurements. However, the benefits of both clay and PCL were present together in the nanocomposites, besides the improved processability and the expected improvement of barrier properties. This led to increases in modulus of elasticity, yield strength, and although slight, mostly in ductility. POLYM. ENG. SCI., 46:864–873, 2006. © 2006 Society of Plastics Engineers  相似文献   

11.
Polylactide (PLA) nanocomposite was prepared by melt blending of PLA and transition metal ion (TMI) adsorbed montmorillonite (MMT). PLA nanocomposite was characterized for mechanical performance, and the results revealed that the tensile modulus, flexural modulus, and impact strength were increased marginally. The nanocomposite was optimized at 5 wt% of TMI‐modified MMT (TMI‐MMT) loading. Thermogravimetric analysis displayed increase in onset of degradation temperature, and differential scanning calorimetry showed marginal increase in glass transition temperature (Tg) and melting temperature (Tm) in case of PLA nanocomposites, when compared with virgin PLA. The flammability testing of nanocomposites indicated good fire retardance characters. X‐ray diffraction patterns of TMI‐MMT and the corresponding nanocomposites indicated an intercalation of the metal ions into the clay interlayer. Fourier transform infrared spectroscopy analysis indicate formation of [Zn(EDA)2]2+ and [Cu(EDA)2]2+ complexes in the MMT interlayer. Dynamic mechanical analysis shows increase in glass transition temperature (Tg) and storage modulus (E′) in case of PLA nanocomposites reinforced with 5 wt% modified MMT. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers  相似文献   

12.
Three types of polypropylene‐grafted silica (PGS‐2 K, PGS‐8 K and PGS‐30 K) with different grafting chain lengths were prepared. After melt‐blending PGS with polypropylene (PP), we studied the PP/PGS interface properties and the influence of PP/PGS interfaces on mechanical properties of nanocomposites. The strong matrix/particle interface was observed in PP/PGS‐30 K nanocomposites with 5 wt % particle loading as evidenced by 2.5 °C increased glass transition temperature (Tg) compared with neat PP, whereas the weak matrix/particle interface was observed in PP/PGS‐2 K nanocomposites with decreased Tg. The variations in the matrix/particle interfacial strength lead to a transition in the yield stress of nanocomposites. Compared with the unfilled PP, the yield stress of the PP/PGS‐2 K nanocomposites is decreased by 0.7 MPa, and the yield stress of the PP/PGS‐30 K nanocomposites is enhanced by 1.4 MPa. In addition, benefiting from good dispersion, the PP/PGS‐masterbatch nanocomposites with a strong matrix/particle interface not only exhibit increased Young's modulus and yield stress, but also the strain at break remains in line with the unfilled PP, which is in contrast to the conventional wisdom that the gain in modulus and strength must be at the expense of the decreased break strain. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45887.  相似文献   

13.
In contrast to polymeric composites, the role of interface/interphase has been widely acknowledged to govern their overall properties and performance. Environmental temperature has substantial effects on the interfacial durability of polymer nanocomposites. In this regard, present investigation has been carried out to study the mechanical performance of pristine (UCNT) and carboxylic functionalized CNT (FCNT) embedded epoxy nanocomposites under different elevated temperatures. Higher flexural strength and modulus of FCNT‐EP nanocomposite were recorded over UCNT‐EP and neat epoxy at room temperature environment. Flexural testing at elevated temperatures revealed a higher rate of strength degradation in polymer nanocomposites over neat epoxy. Postfailure analysis of specimens has been conducted to understand the alteration in failure micro‐mechanisms upon UCNTs and FCNTs addition in epoxy. Variation in viscoelastic properties with temperature has been studied from dynamic mechanical thermal analysis and significant reduction in glass transition temperature (Tg) is observed for nanocomposites. In the studied temperature and stress combinations, FCNT‐EP nanocomposites exhibited better creep resistance over UCNT‐EP and neat epoxy. Room temperature strengthening, elevated temperature strength degradations, improved creep resistance and reduction in Tg in nanocomposites over neat polymer have been discussed in terms of dynamic nature and gradient structure of CNT/epoxy interphase. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44851.  相似文献   

14.
The effects of boiling water on the mechanical and thermal properties and morphologies of polycarbonate (PC), PC/acrylonitrile–butadiene–styrene resin (PC/ABS), and PC/low‐density polyester (PC/LDPE) blends (compositions of PC/ABS and PC/LDPE blends were 80/20) were studied. PC and the PC/ABS blend had a transition from ductile to brittle materials after boiling water aging. The PC/LDPE blend was more resistant to boiling water aging than PC and the PC/ABS blend. The thermal properties of glass‐transition temperature (Tg) and melting temperature (Tm) in PC and the blends were measured by DSC. The Tg of PC and PC in the PC/ABS and PC/LDPE blends decreased after aging. The Tg of the ABS component in the PC/ABS blend did not change after aging. The supersaturated water in PC clustered around impurities or air bubbles leading to the formation of microcracks, which was the primary reason for the ductile–brittle transition in PC, and the microcracks could not recover after PC was treated at 160°C for 6 h. The PC/ABS blend showed slightly higher resistance to boiling water than did PC. The highest resistance to boiling water of the PC/LDPE blend may be attributed to its special structural morphology. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 589–595, 2003  相似文献   

15.
The phase diagram of blends of liquid crystalline polymer (LCP) and polycarbonate (PC) was constructed. The effect of temperature on morphological development in melt‐blended samples was examined with a polarized light microscope, in conjunction with a heating stage. Phase separation in the blend was observed as the temperature was increased. For a particular LCP/PC blend composition, two‐phase separation temperatures (Tsp1 and Tsp2) were determined. Consequently, the corresponding phase diagram relating to phase separation was constructed. It was divided into three regions. No phase separation occurred when the blend was below Tsp1. However, a slight phase separation was detected when the temperature was between Tsp1 and Tsp2. Moreover, pronounced phase separation was observed when the blend was at a temperature above Tsp2. The phase‐separated structure varied according to the initial composition of the blends. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

16.
The thermal degradation of two polyhedral oligomeric silsesquioxane/polystyrene (POSS/PS) nanocomposites of formula R8(SiO1.5)8 POSS/PS and R′1R7(SiO1.5)8 POSS/PS (where R′ = Phenyl and R = Cyclopentyl), at 5% of POSS concentration, was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Compounds were prepared by the polymerization of styrene in the presence of POSS. Degradations were carried out into a thermobalance, in the scanning mode, at various heating rates, and the obtained thermogravimetric (TG) curves were discussed and interpreted. The initial decomposition temperature (Ti), the temperature at 5% mass loss (T5%), the glass transition temperature (Tg), and the activation energy (Ea) of degradation of nanocomposites were determined and compared with each other and with those of unfilled PS. The Ti, T5%, and degradation Ea values of nanocomposites were higher than those of neat PS, thus indicating a better heat resistance and lower degradation rate, and then a better overall thermal stability. The use of POSS with a symmetric structure, in the synthesis of PS based nanocomposite, showed a decrease of Tg value not only in respect to asymmetric POSS/PS nanocomposite but also in respect to neat polymer, thus suggesting an influence of filler structure in the thermal properties of the materials. POLYM. COMPOS., 33:1903–1910, 2012. © 2012 Society of Plastics Engineers  相似文献   

17.
In this study, the effect of maleic anhydride grafted styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) content on mechanical, thermal, and morphological properties of polyethylene terephthalate/polycarbonate/halloysite nanotubes (PET/PC/HNTs) nanocomposites has been investigated. Nanocomposites of PET/PC (70 : 30) with 2 phr of HNTs were compounded using the counter rotating twin screw extruder. A series of formulations were prepared by adding 5–20 phr SEBS‐g‐MA to the composites. Incorporation of 5 phr SEBS‐g‐MA into the nanocomposites resulted in the highest tensile and flexural strength. Maximum improvement in the impact strength which is 245% was achieved at 10 phr SEBS‐g‐MA content. The elongation at break increased proportionately with the SEBS‐g‐MA content. However, the tensile and flexural moduli decreased with increasing SEBS‐g‐MA content. Scanning electron microscopy revealed a transition from a brittle fracture to ductile fracture morphology with increasing amount of SEBS‐g‐MA. Transmission electron microscopy showed that the addition of SEBS‐g‐MA into the nanocomposites promoted a better dispersion of HNTs in the matrix. A single glass transition temperature was observed from the differential scanning calorimetry test for compatibilized nanocomposites. Thermogravimetric analysis of PET/PC/HNTs nanocomposites showed high thermal stability at 15 phr SEBS‐g‐MA content. However, on further addition of SEBS‐g‐MA up to 20 phr, thermal stability of the nanocomposites decreased due to the excess amount of SEBS‐g‐MA. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42608.  相似文献   

18.
Although organically modified montmorillonite (OMMT) has been incorporated into unsaturated polyester (UP) resin to enhance properties, the aggregation often leads to defects which directly affect the properties of nanocomposites. In this work, OMMT slurry modified by a new allyl surfactant with carbon–carbon double bond, hexadecyl allyl dimethyl ammonium chloride (C16‐DMAAC), was employed to prepare nanocomposites by in situ polymerization. The results illustrated that the existence of OMMT slurry helped monomers enter the OMMT galleries, leading to well‐dispersed OMMT in the UP matrix. The mechanical properties and thermal properties of OMMT nanocomposites were improved. With OMMT loading of 5 wt %, the tensile strength and flexural strength can be improved by 22% and 38%, respectively. Meanwhile, the onset thermal decomposition temperature (T–10) value was ameliorated from 310.6 °C to 330.6 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45251.  相似文献   

19.
Polyether block amide (PEBA) elastomer‐organoclay nanocomposites were prepared by a melt mixing technique. The X‐ray diffraction and transmission electron microscope analysis indicated that the nanocomposite formed a partially exfoliated nanostructure in which the organoclay was dispersed uniformly throughout the matrix at the nanometer scale. The effect of organoclay on the melting temperature (Tm), glass transition temperature (Tg), crystallization temperature (Tc), and heat of fusion (ΔHm) of the PEBA was determined by differential scanning calorimetry. Enhanced mechanical properties of the nanocomposites were observed from tensile and dynamic mechanical analysis. Thermal gravimetric analysis showed that the clay nanoparticles caused an increase in the thermal stability of the PEBA. Measurement of oxygen permeability and the degree of swelling in ASTM #3 oil indicated that the gas barrier properties and solvent resistance were greatly improved by the clay nanoparticles. Melt rheological studies revealed that the nanocomposites exhibited strong shear thinning behavior and a percolated network of the clay particles was formed. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers  相似文献   

20.
A comparative study concerning the thermal stability of polystyrene (PS) and three polyhedral oligomeric silsesquioxane/polystyrene (POSS/PS) nanocomposites of formula R7R′(SiO1.5)8/PS (where R = isobutyl and R′ = phenyl), at various (3, 5, and 10%) POSS concentration was carried out in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of POSS and the experimental filler concentration in the obtained compounds, determined by 1H NMR spectroscopy, was in all cases slightly higher than that in the reactant mixtures. Inherent viscosity (ηinh) determinations indicated that the average molar mass of polymer in the nanocomposites was practically the same than neat PS and were in agreement with calorimetric glass transition temperature (Tg) measurements. The temperature at 5% mass loss (T5%) and the activation energy (Ea) of degradation process of synthesized nanocomposites were determined and compared with each other and with those of unfilled PS. On the basis of the results from thermal and IR spectroscopy characterizations, nanocomposite with 5% of molecular filler appears the most thermally stable. The results were also compared with literature data on similar PS‐based nanocomposites. POLYM. COMPOS., 2013 © 2013 Society of Plastics Engineers  相似文献   

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