Novel preparation method for improving the dispersion of ionic liquid‐modified montmorillonite in poly(ethylene terephthalate)

Thermally stable ionic liquids (ILs) were used to modify clay nanoparticles for use in the preparation of poly(ethylene terephthalate)/clay nanocomposites. Nanoclays with smaller particle size distributions were prepared with a two‐step centrifugation method that removed large particles from commercial montmorillonite (MMT). Scanning electron microscopy of aqueous dispersions of MMT and centrifuged clay (CMMT) illustrated that the average particle size of CMMT in water was much lower than that of MMT in water. Both CMMT and MMT were modified with imidazolium‐ and phosphonium‐based ILs. Fourier transform infrared spectroscopy revealed that the surfactants were associated with the clay surface. Thermal gravimetric analysis results indicated that clays modified with thermally stable ILs degraded above 300°C and could survive PET processing temperatures. Transmission electron microscopy for nanocomposites revealed an improvement in the dispersion of centrifuged nanoclays (modified with both imidazolium and phosphonium ILs) into the polymer matrix compared to non‐centrifuged modified MMT with larger particle sizes. X‐ray diffraction and differential scanning calorimetry data indicated that particle size distributions have a significant effect on the dispersion and rate of crystallization of nanoclays modified with imidazolium surfactants. There was, however, a less important effect of centrifugation on the dispersion of nanoclays modified with phosphonium surfactants. POLYM. COMPOS. 37:1259–1266, 2016. © 2014 Society of Plastics Engineers     

Preparation and characterization of poly(ethylene‐co‐vinyl alcohol) membranes via thermally induced liquid–liquid phase separation

Porous membranes were prepared through the thermally induced phase separation of poly(ethylene‐co‐vinyl alcohol) (EVOH)/glycerol mixtures. The binodal temperature and dynamic crystallization temperature were determined by optical microscopy and differential scanning calorimetry measurements, respectively. It was determined experimentally that the liquid–liquid phase boundaries were shifted to higher temperatures when the ethylene content in EVOH increased. For EVOHs with ethylene contents of 32–44 mol %, liquid–liquid phase separation occurred before crystallization. Cellular pores were formed in these membranes. However, only polymer crystallization (solid–liquid phase separation) occurred for EVOH with a 27 mol % ethylene content, and the membrane morphology was the particulate structure. Scanning electron microscopy showed that the sizes of the cellular pores and crystalline particles in the membranes depended on the ethylene content in EVOH, the polymer concentration, and the cooling rate. Furthermore, the tendency of the pore and particle sizes was examined in terms of the solution thermodynamics of the binary mixture and the crystallization kinetics. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 853–860, 2003     

Effect of coupling agent on structure and properties of micro–nano composite fibers based on PET

Poly(ethylene terephthalate) (PET)/carbon black (CB) micro–nano composite fibers were manufactured by melt spinning method. To achieve good dispersion, nano‐CB particles were modified by coupling agent (CA). The effect of CA on structure and properties of the fibers were investigated via scanning electron microscopy (SEM), tensile testing, differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), sonic orientation, and birefringence, respectively. At 2 wt % CA dosage, CB particles present the optimal dispersion in the fibers, shown in SEM images. Besides, the fibers possess the maximum breaking strength, the lowest crystallization temperature, and the highest crystallinity. After CA modification, the superior interfacial structure between PET and CB is beneficial to improve mechanical properties of the fibers. The well dispersed CB particles provide more heterogeneous nucleation points, resulting in the highest crystallinity. Furthermore, the fibers with 2 wt % CA dosage possess the maximum orientation and shrinkage ratio. According to Viogt–Kelvin model, the thermal shrinkage curves of the fibers can be well fitted using single exponential function. The three‐phase structure model of crystal phase–amorphous phase–CB phase was established to interpret the relationship among shrinkage, orientation, and dispersion of CB particles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43846.     

Preparation and crystallization of poly(ethylene terephthalate)/SiO2 nanocomposites by in‐situ polymerization

Poly(ethylene terephthalate) (PET)/SiO₂ nanocomposites were prepared by in situ polymerization. The dispersion and crystallization behaviors of PET/SiO₂ nanocomposites were characterized by means of transmission electron microscope (TEM), differential scanning calorimeter (DSC), and polarizing light microscope (PLM). TEM measurements show that SiO₂ nanoparticles were well dispersed in the PET matrix at a size of 10–20 nm. The results of DSC and PLM, such as melt‐crystalline temperature, half‐time of crystallization and crystallization kinetic constant, suggest that SiO₂ nanoparticles exhibited strong nucleating effects. It was found that SiO₂ nanoparticles could effectively promote the nucleation and crystallization of PET, which may be due to reducing the specific surface free energy for nuclei formation during crystallization and consequently increase the crystallization rate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 655–662, 2006     

Surface modification of a calcium fluoride filler and the effect on the nonisothermal crystallization behavior of poly(ethylene terephthalate)

Two different types of calcium fluoride particles (～325 nm), one of them surface modified using a long‐chain organophosphorous reagent, were incorporated into a poly(ethylene terephthalate) (PET) matrix. The CaF₂ particles were synthesized by a simple chemical precipitation method. To modify the particles surface, a heat treatment using Cyanex^® 921 [tri‐n‐octylphosphine oxide (TOPO)] dissolved in isopropanol, was carried out. Therefore, unlike the as‐synthesized particles, the modified particles contained an amount of TOPO. The composite materials were prepared by melt‐blending PET and particles at different filler loadings. The influence of the particles surface modification on the nonisothermal crystallization behavior of PET was investigated by using differential scanning calorimetry and field emission scanning electron microscopy. The Jeziorny‐modified Avrami equation was applied to describe the crystallization kinetics and several parameters were analyzed (half‐crystallization time, Avrami exponent, and rate constant). According to the results, the fluorite particles act as nucleating agents, accelerating the PET crystallization rate. However, the effect on the polymer crystallization rate was more noticeable with the addition of the nonmodified particles where the surface might play an important role for epitaxial crystallization, while the addition of the particles, with an organic coating layer on the surface, resulted in a crystallization behavior more similar to the observed for neat PET. POLYM. ENG. SCI., 54:2938–2946, 2014. © 2014 Society of Plastics Engineers     

Preparation and characterization of poly(ethylene terephthalate) powder‐filled high‐density polyethylene in the presence of silane coupling agents

Micron‐size crystalline particles of Poly(ethylene terephthalate) (PET), obtained from PET bottles by crystallization and grinding, were used as a filler in high‐density polyethylene (HDPE). The composite of PET particle‐filled HDPE was prepared by melt mixing at 190°C, which was well below the melting temperature of PET. Silane coupling agents (SCAs) were used to enhance the interaction between PET and HDPE in the composite. A chain extender (CE) and maleic anhydride (MA) were also used to provide further interaction with SCAs between these two materials. The ultimate tensile strength, especially at highest content 40% PET‐filled HDPE, and the impact strength of SCAs‐treated PET‐filled HDPE was found to be highly improved compared to untreated PET filling into HDPE. Dynamic mechanical analyses (DMA) demonstrated that T_g of the main matrix polyethylene was depressed from 3 to 10°C. Scanning electron microscopy (SEM) studies indicated a strong interaction between PET powder and HDPE when SCAs were present in the system. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 827–835, 2001     

Morphology and properties of poly(ethylene terephthalate) and thermoplastic polyester elastomer blends modified in the melt by a diisocyanate chain extender and filled with a short glass fiber

The structural features and rheological, mechanical, and relaxation properties of poly(ethylene terephthalate) (PET) blends with 7–50 wt % polyester thermoplastic polyester elastomer (TPEE), a block copolymer of poly(butylene terephthalate) and poly(tetramethylene oxide), chemically modified by a diisocyanate chain extender (CE) and reinforced with 30% glass fibers (GF) were studied. The composites were obtained by reactive extrusion with a twin‐screw reactor–mixer with a unidirectional rotation of screws. The molecular–structural changes in the materials were judged against data provided by differential scanning calorimetry, scanning electron microscopy, relaxation spectrometry, and rheological analysis of the melts. Regardless of the TPEE concentration in the blends with GF‐reinforced PET, the addition of CE resulted in the growth of the indices of the mechanical properties at straining, bending, and impact loading and an increase in the melt viscosity. In addition, an increase in the average length of short GFs in the composites and an intensification of interphase adhesion in the polyester binder–GF surface system were observed. The introduction of CE promoted a slowdown in PET crystallization in the composites and intensified the interphase adhesion in the binder–GF system at temperatures higher and lower than the PET glass‐transition temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45711.     

Antinucleating action of polystyrene on the isothermal cold crystallization of poly(ethylene terephthalate)

The effect of polystyrene (PS) on the kinetics of the cold crystallization of poly(ethylene terephthalate) (PET) was thoroughly investigated. The PET/PS blends were essentially immiscible, as observed by dynamic mechanical thermal analysis, which showed two distinct glass‐transition temperatures, and by scanning electron microscopy. The neat PET and its blends were isothermally cold‐crystallized at various temperatures, and the kinetic parameters were determined with the Avrami approach. PET and its blends presented values of the Avrami exponent close to 2, and the kinetic constant increased with the crystallization temperature increasing. For all the crystallization temperatures studied, the presence of only 1 wt % PS significantly reduced the rate of cold crystallization of PET. A further increase in the PS concentration did not show any significant influence. The blends presented higher values of the activation energy for cold crystallization, which was estimated from Arrhenius plots. The equilibrium melting temperature of neat PET was determined on the basis of the linear Hoffman–Weeks extrapolative method to be ～ 255°C. This value decreased in the presence of PS, and this suggested limited solubility between PET and PS. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter was obtained, and it was shown to be higher for the neat PET than for the blends. Moreover, a transition of regimes (I → II) was observed in both PET and its blends. From the investigations conducted here, it is clear that PS in small amounts causes a reduction in the rate of PET crystallization, acting as an antinucleating agent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nonisothermal crystallization kinetics and morphology of poly(ethylene terephthalate) modified with poly(lactic acid)

The nonisothermal crystallization kinetics of poly(ethylene terephthalate) (PET) copolymers modified with poly(lactic acid) (PLA) were investigated with differential scanning calorimetry, and a crystal morphology of the samples was observed with scanning electron microscopy. Waste PET (P100) obtained from postconsumer water bottles was modified with a low‐molecular‐weight PLA. The PET/PLA weight ratio was 90/10 (P90) or 50/50 (P50) in the modified samples. The nonisothermal melt‐crystallization kinetics of the modified samples were compared with those of P100. The segmented block copolymer structure (PET‐b‐PLA‐b‐PET) of the modified samples formed by a transesterification reaction between the PLA and PET units in solution and the length of the aliphatic and aromatic blocks were found to have a great effect on the nucleation mechanism and overall crystallization rate. On the basis of the results of the crystallization kinetics determined by several models (Ozawa, Avrami, Jeziorny, and Liu–Mo) and morphological observations, the crystallization rate of the samples decreased in the order of P50 > P90 > P100, depending on the amount of PLA in the copolymer structure. However, the apparent crystallization activation energies of the samples decreased in the order of P90 > P100 > P50. It was concluded that the nucleation rate and mechanism were affected significantly by the incorporation of PLA into the copolymer structure and that these also had an effect on the overall crystallization energy barrier. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Morphology and crystallization behavior of the PP/PET nanocomposites

Nanocomposites containing polypropylene (PP), PET, and montmorillonite were prepared in a twin‐screw extruder. X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, polarized optical microscopy, and differential scanning calorimetry were used to characterize the samples. Intercalated and exfoliated morphology were observed in the nanocomposites. The PET domains usually presented spherical shapes and they were the start point to PP crystallization. The average diameter and number of PET domains was evaluated. The influence of addition of PP‐MA as compatibilizer on PP/PET was investigated. The interconnected morphology was observed in the nanocomposite containing PP‐MA. The clay located predominantly in the interphase and in the PET phase. The crystallization process was monitored and the PET crystallization rate was slower in the nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Nucleation and crystallization of PET droplets dispersed in an amorphous PC matrix

The present work compares the nucleation and crystallization process of poly(ethylene terephthalate) (PET) in bulk and when it is finely dispersed in a polycarbonate (PC) matrix. Two types of 80/20 PC/PET immiscible blends were prepared by twin-screw extrusion at different screw rotation rates in order to produce fine dispersions of PET. The results indicate that the finer the dispersion, the greater the inhibition of the crystallization of the PET droplets. These results are explained by demonstrating (through self-nucleation experiments) that a fractionated crystallization process was developed in the dispersed PET, since the number of PET particles was much greater than the number of heterogeneities originally present in the bulk polymer. The dispersion of PET into droplets also affects its crystallization rate during isothermal crystallization at high temperatures and its reorganization capacity during heating. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 1725–1735, 1998     

Influence of shearing on crystallization of polyoxymethylene/high density polyethylene blend

The influence of rotating shear on morphology, crystallization behavior, and crystalline structure of polyoxymethylene (POM) and high density polyethylene (HDPE) blend was investigated by polarized light microscopy (PLM) connected with a CSS450 shearing hot‐stage, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X‐ray diffraction. The experimental results showed that the crystalline and dispersion morphology of POM/HDPE (50/50) blend were strongly affected by shearing, while the crystallization temperature and rate of crystallization of POM in the sheared blend increased with no significant change in the crystalline structure of the blend. In the unsheared blend, phase separation appeared between POM and HDPE which crystallized separately and the bicontinuous phase morphology was formed. But for the sheared blend, a large number of compact and regular shish‐kebabs emerged in POM phase and the phase domains of HDPE oriented along the direction of shear flow separating from one another so that the shearing aggravated the phase separation. There is no special interaction between POM and HDPE and these two polymers crystallized individually, differing from that of POM/PEO blend. J. VINYL ADDIT. TECHNOL., 24:147–153, 2018. © 2016 Society of Plastics Engineers     

Plasma treatment‐induced fluorine‐functionalized multi‐walled carbon nanotubes to modify poly(ethylene terephthalate) obtained via in situ polymerization

The introduction of carbon nanotubes in a polymer matrix can markedly improve its mechanical properties and electrical conductivity, and much effort has been devoted to achieve homogeneous dispersions of carbon nanotubes in various polymers. Our group previously performed successfully fluorine‐grafted modification on the sidewalls of multi‐walled carbon nanotubes (MWCNTs), using homemade equipment for CF₄ plasma irradiation. As a continuation of our previous work, in the present study CF₄ plasma‐treated MWCNTs (F‐MWCNTs) were used as a nanofiller with poly(ethylene terephthalate) (PET), which is a practical example of the application of such F‐MWCNTs to prepare polyester/MWCNTs nanocomposites with ideal nanoscale structure and excellent properties. As confirmed from scanning electron microscopy observations, the F‐MWCNTs could easily be homogeneously dispersed in the PET matrix during the in situ polymerization preparation process. It was found that a very low content of F‐MWCNTs dramatically altered the crystallization behavior and mechanical properties of the nanocomposites. For example, a 15 °C increase in crystallization temperature was achieved by adding only 0.01 wt% F‐MWCNTs, implying that the well‐dispersed F‐MWCNTs act as highly effective nucleating agents to initiate PET crystallization at high temperature. Meanwhile, an abnormal phenomenon was found in that the melt point of the nanocomposites is lower than that of the pure PET. The mechanism of the tailoring of the properties of PET resin by incorporation of F‐MWCNTs is discussed, based on structure–property relationships. The good dispersion of the F‐MWCNTs and strong interfacial interaction between matrix and nanofiller are responsible for the improvement in mechanical properties and high nucleating efficiency. The abnormal melting behavior is attributed to the recrystallization transition of PET occurring at the early stage of crystal melting being retarded on incorporation of F‐MWCNTs. Copyright © 2009 Society of Chemical Industry     

PET/ZnO纳米复合材料的制备及结晶性能

通过纳米ZnO存在下的对苯二甲酸／乙二醇(TPA／EG)酯化和缩聚反应制备聚对苯二甲酸乙二醇酯(PET)／ZnO纳米复合材料，研究了纳米ZnO用量及其分散方式对PET粘均摩尔质量、纳米ZnO在复合物中的分散及聚乙二醇(PEG)结晶性能的影响。发现纳米ZnO及分散改性剂(PEG)的加入，对合成PET的粘均摩尔质量均有一定影响；纳米ZnO在EG中直接分散再缩聚形成的复合物中，纳米ZnO团聚严重、分散性差，PET的结晶度和结晶速率降低；在纳米ZnO分散过程中加入PEG可以降低纳米ZnO在复合物中的团聚，提高分散性，PET的结晶度和结晶速率提高。     

Crystallization,properties, and crystal and nanoscale morphology of PET–clay nanocomposites

The crystallization process and crystal morphology of poly(ethylene terephathalate) (PET)–clay nanoscale composites prepared by intercalation, followed by in‐situ polymerization, have been investigated by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic scanning calorimetry (DSC), and X‐ray techniques, together with mechanical methods. Results of the nonisothermal crystallization dynamics show that the nanocomposites of PET (Nano‐PET) have 3 times greater crystallization rate than that of pure PET. The thermal properties of Nano‐PET showed heat distortion temperature (HDT) 20–50°C higher than the pure PET, while with a clay content of 5%, the modulus of Nano‐PET is as much as 3 times that of pure PET. Statistical results of particle distribution show that the average nanoscale size ranges from 10 to 100 nm. The particles are homogenously distributed with their size percentages in normal distribution. The agglomerated particles are 4% or so with some particles size in the micrometer scale. The morphology of exfoliated clay particles are in a diordered state, in which the morphology of the PET spherulitics are not easy to detect in most of microdomains compared with the pure PET. The molecular chains intercalated in the interlamellae of clay are confined to some extent, which will explain the narrow distribution of the Nano‐PET molecular weight. The stripe‐belt morphology of the intercalated clay show that polymer PET molecular chains are intercalated into the enlarged interlamellar space. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1139–1146, 1999     

Supermolecular morphology of polypropylene filled with nanosized silica

The supermolecular morphology of injection‐molded SiO₂/polypropylene (PP) nanocomposites was investigated via thin sections analyzed under polarized light and the systematic development of an appropriate etching technique, which allowed the study of the supermolecular morphologies with light microscopy (LM) and high‐resolution field emission scanning electron microscopy (FESEM). In parallel, information regarding the dispersion, distribution state, and morphology of SiO₂ particles was investigated via transmission electron microscopy (TEM) and scanning electron microscopy (SEM) of the ion‐polished and fractured surfaces of SiO₂‐filled PP. The TEM/SEM results demonstrated an almost homogeneous dispersion and distribution of SiO₂ particle agglomerates in the PP matrix. With polarized transmitting LM, reflecting LM, and FESEM, the spherulitic structure of the nanocomposites could be visualized to obtain information on the nanoparticle influence on the crystallization and structural behavior. The size and size distribution of the spherulites analyzed with transmitting light (thin sections) and reflecting light (etched specimens) showed an excellent correlation. With increasing filler loading, the mean size of the spherulites decrease as did the degree of crystallinity. This was a clear indication that the particles acted as nucleation agents and, on the other hand, hindered the arrangement of the molecules during the crystallization. As a result, the particles were most likely located in three areas: the center of the spherulites, the areas between the highly crystalline branches, and the spherulite boundaries. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39655.     

Reaction and miscibility of two diepoxides with poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) was melt‐blended at 270°C with two epoxy monomers, diglycidyl ether of bisphenol A (DGEBA) and 3,4‐epoxycyclohexyl‐methyl‐3,4‐epoxycyclohexyl carboxylate (ECY). Intermediate proportions of the epoxy in the range of 20–0.5 wt % were used. If the epoxy monomers were added in a high proportion (10–20%), a large fraction did not react with PET. Calorimetric experiments showed that the unreacted fractions of both epoxies were miscible with the amorphous phase of the polyester. Only one glass‐transition temperature was detected. It was depressed as the epoxy content was increased. The transition was broad when the PET component was crystalline, and it was narrow when the PET component was made amorphous by quenching of the blend. These features were confirmed by dynamic thermal mechanical analysis. As is often the case for crystalline blends, the crystallization and melting temperatures decreased when the proportion of the epoxy was increased. Concerning the reactivity of the epoxy with PET, the behavior differed according to the nature of the epoxy. The DGEBA monomer showed a low reactivity. It was not effective for the chain extension of PET, and no increase in the intrinsic viscosity was observed under the experimental conditions. However, some functionalization of the chain ends may be possible at a high concentration of the epoxy. ECY was more reactive, and the molecular weight of the processed PET increased, although the value of the commercial untreated polyester was not attained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1995–2003, 2003     

A Comprehensive Study on Physical,Mechanical, and Thermal Properties of Poly(Ethylene Terephthalate) Filled by Micro‐ and Nanoglass Flakes

Polyethylene terephthalate (PET) composites containing micro‐ and nanoglass flakes were prepared by melt blending. The percentage of nanoglass flakes was varied from 0.5, 1, 2, and 3 wt% and the concentration of microglass flakes was 1, 3, and 5 wt%. The effect of glass flake on morphology, physical, mechanical, and thermal properties of PET was studied using scanning electron microscopy (SEM), energy‐dispersive X‐ray analysis (EDXA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), X‐ray diffraction (XRD), and tensile test. The observations showed that both types of particles were dispersed in PET, homogeneously, though microglass flakes had better dispersion compared with their nanosized counterparts. According to DSC thermogram, the crystallization rate and temperature of PET increased with incorporation of both types of glass flakes. The crystallization rate of PET was increased from 31.41% to 34.25% with the addition of 1 wt% of nanoglass flakes. Moreover, the onset of thermal degradation increased more than 9°C with the addition of micro‐ and nanoglass flakes. Based on the mechanical viewpoint, the Young's modulus of PET was improved by the addition of both micro‐ and nanoglass flakes. On the other hand, the tensile strength of PET was decreased from 45.4 MPa to 31.3 MPa using 1 wt% of nanoglass flakes. According to X‐ray diffractometry, using of micro‐ and nanoglass flakes resulted in the decrement of PET crystallites. Whereas, the size of crystallites was lower than microglass flakes, in the case of using nanoglass flakes. J. VINYL ADDIT. TECHNOL., 26:380–389, 2020. © 2019 Society of Plastics Engineers     

Effect of thermal history on the morphology of thermotropic liquid crystalline copolyesters based on PET and PHB

Morphological studies were carried out on thermotropic liquid crystalline copolyesters based on poly(ethylene terephthalate) (PET) and para-hydroxybenzoic acid (PHB), where PHB content varied from 30 mole percent up to 80 mole percent. The technique of chemical etching, using n-propylamine as the etchant, coupled with scanning electron microscopy was utilized to obtain structural information. Scanning electron microscopy results on chemically etched, compression moulded films show that selective chemical etching of the PET rich regions occur. This indicates that the morphology of the copolymers is hetergeneous in nature. Further support regarding a hetergeneous morphology was obtained by transmission electron microscopy. A morphological model has been proposed based on these results. The observance of non-equilibrium behaviour associated with amorphous PET regions (as seen from d.s.c. measurements) also strongly indicates the presence of a phase rich in PET and thus supports the non-homogeneous morphological model. Thermal analysis of these copolyesters suggests that the chain structure is non-random and this is an agreement with results published by Wunderlich et al. The glass transition temperature typically associated with PET is present and remains constant in all copolymers compositions where PET is the continuous phase. Further, the melting temperatures obtained experimentally are higher than the values predicted by theory for random copolymers and the melting endotherms are relatively narrow. These observations also indicate a non-random chain structure. Structural studies conducted on films compression molded at different temperatures show that morphological rearrangement occurs at higher temperatures with the formation of domains of the order of 10 microns.     

Thermal degradation and crystallization behavior of blend‐based nanocomposites: Role of clay network formation

The main goal of this study is to explicate the exact role of nanoclay particles on thermal degradation mechanism and crystallization behavior of blend‐based nanocomposites. Thermoplastic olefin (TPO) nanocomposites, as a simple model, were prepared via melt mixing in an internal batch mixer. X‐ray diffractometry (XRD) and transmission electron microscopy tests show that a relatively good dispersion of silicate layers was obtained in the system. On the addition of nanoclay, a remarkable reduction in rubber domain size was observed through scanning electron microscopy (SEM). Thermogravimetric analysis shows that nanoclay particles can retard thermal decomposition process. Thermal degradation kinetic studies, using Flynn–Wall–Ozawa method, reveal that addition of nanoclay contents higher than 1 wt % changes the mechanism of thermal degradation. A mechanism was proposed to explain this phenomenon based on SEM images of char residues. Non‐isothermal crystallization behavior of samples was investigated using differential scanning calorimeter. The unexpected reduction in crystallinity of TPO nanocomposites containing 5 wt % nanoclay was explained using rheometry analysis and attributed to the formation of stable percolated clay networks in this sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012