Thermal degradation behaviors of phosphorus–silicon synergistic flame‐retardant copolyester

A novel phosphorus‐containing poly (ethylene terephthalate) (PET) copolyester/nano‐SiO₂ composite (PET‐co‐DDP/SiO₂) was synthesized by in situ polycondensation of terephthalic acid (TPA), ethylene glycol (EG), [(6‐oxide‐6H‐dibenz[c,e] [1,2]oxaphosphorin‐6‐yl)‐methyl]‐butanedioic acid (DDP), and nano‐SiO₂. The morphology of PET nanocomposites was observed by using transmission electron microscope and scanning electron microscope. It was found that the SiO₂ nanoparticles were dispersed uniformly at nanoscale in the copolyesters with content 2 wt %. The thermal degradation behavior of PET nanocomposites was investigated by thermogravimetric analysis performed with air and nitrogen ambience. The activation energies of thermal degradation were determined using Kissinger and Flynn–Wall–Ozawa methods, respectively. The results obtained from Kissinger method showed that the activation energy was increased with the introduction of SiO₂. Moreover, the activation energy is decreased for PET‐co‐DDP system in nitrogen and air. The results also indicated that the SiO₂ and DDP had synergic effect on the early decomposition and the late charring in air. Furthermore, in the PET‐co‐DDP/SiO₂ system, the activation energy increased when the DDP component increased. However, the opposite results were obtained when the Flynn–Wall–Ozawa method was used. That was because the Doyle approximation stands correct as the conversion degree is from 5% to 20%. The effects of SiO₂ and DDP on the PET thermal degradation were lower in nitrogen than in air. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of novel nano/submicrofiber catalyst containing nano‐TiO2 particles

A novel Nano/submicrofiber catalyst was prepared via electrospinning technology from poly (vinyl pyrrolidone) (PVP) and nano‐TiO₂. First, nano‐TiO₂ particles were added into the mixture of ethanol and deionized water, the mass ratio of ethanol and deionized water was 1 : 1, the TiO₂ suspension was obtained after 1 h with ultrasonic treatment and centrifugal effect, Then PVP was added into the above‐mentioned suspension and the content of PVP in the sol was 28%. The TiO₂/PVP solution was electrospun with different voltage. The effects of the content of TiO₂ and electrospinning voltage on diameter of nano/submicrofiber were studied. The nano/submicrofiber catalyst was characterized by scanning electron microscopy, transmission electron microcopy, X‐ray diffraction, and Fourier transform infrared. The results show that the diameter of nano/submicrofiber increases with an increase of the content of nano‐TiO₂ and decreases with the increase of electrospinning voltage. The analytical result showed that the nano‐TiO₂ particles were well dispersed in the matrix of PVP, moreover, the crystal type of nano‐TiO₂ was a mixture of anatase and rutile and the diameter of nano‐TiO₂ particles in the nano/submicrofiber is in the range of 20–60 nm and the nano‐TiO₂ particle was monodisperse, and the nano‐TiO₂ particle and PVP molecule was connected by a hydrogen bonding. This nano/submicrofiber catalyst has a high efficiency on degradation on CH₂O. 56.8 percent of CH₂O was degraded under ultraviolet radiation in 80 min when the content of nano‐TiO₂ is 20% in nano/submicrofibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation of PET/clay nanocomposites via in situ polymerization in the presence of monomer‐activated organoclay

Various polyethylene terephthalate (PET)/clay nanocomposites containing a commercial organoclay (organophilic montmorillonite nanoclay [OMMT]) and a monomer‐activated OMMT (remodified OMMT) were prepared via in situ interlayer polycondensation of dimethyl terephthalate and ethylene glycol. In order to remodify the commercial OMMT nanoparticles, a diacid chloride monomer was applied. The prepared nanocomposites were characterized by diverse methods, including X‐ray diffraction, differential scanning calorimetry, thermogravimetric analysis, and intrinsic viscosity measurements. The results of the study revealed that the PET/(remodified OMMT) nanocomposites possess a better state of clay dispersion as well as significantly better thermal properties as compared with the PET/OMMT nanocomposites. Moreover, the PET/(remodified OMMT) nanocomposites showed higher crystallization temperature, degree of crystallinity, maximum degradation temperature, and lower half‐time of crystallization than that of the PET/OMMT nanocomposites. It was found that the remodification process for OMMT led to less of a foaming problem during in situ polymerization. J. VINYL ADDIT. TECHNOL., 21:70–78, 2015. © 2014 Society of Plastics Engineers     

Preparation and characterization of poly(styrene‐b‐butadiene‐b‐styrene)/montmorillonite nanocomposites

With some polymerizable small molecules grafting onto the montmorillonite surface, we disposed the clay through in‐situ emulsion polymerization, and the structure of the modified montmorillonites were studied through Fourier transform infrared spectroscopy (FTIR) and X‐ray diffraction (XRD). The nanocomposites of poly(styrene‐b‐butadiene‐b‐styrene) (SBS)/montmorillonite with excellent mechanical properties were prepared by mixing SBS and the modified montmorillonite on the double rollers at 150°C. The exfoliation of the layered silicates was confirmed by XRD analysis and transmission electron microscopy (TEM) observation. After mechanical kneading of the molten nanocomposites, the exfoliation structure of the silicates is still stable for polystyrene macromolecules grafting onto the silicates. Upon the addition of the modified montmorillonite, the tensile strength, elongation at break and tear strength of the nanocomposites increased from 22.6 MPa to 31.1 MPa, from 608% to 948%, from 45.32 N/mm to 55.27 N/mm, respectively. The low‐temperature point of glass‐transition temperature (T_g) of the products was about −77°C, almost constant, but the high‐temperature point increased from 97°C to 106°C. In addition, the nanocomposites of SBS and modified montmorillonites showed good resistance to thermal oxidation and aging. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Facile preparation of superhydrophobic polyester surfaces with fluoropolymer/SiO2 nanocomposites based on vinyl nanosilica hydrosols

A facile method to prepare superhydrophobic fluoropolymer/SiO₂ nanocomposites coating on polyester (PET) fabrics was presented. The vinyl nanosilica (V? SiO₂) hydrosols were prepared via one‐step water‐based sol‐gel reaction with vinyl trimethoxy silane as the precursors in the presence of the base catalyst and composite surfactant. Based on the V? SiO₂ hydrosol, a fluorinated acrylic polymer/silica (FAP/SiO₂) nanocomposite was prepared by emulsion polymerization. The FAP/SiO₂ nanocomposites were coated onto the polyester fabrics by one‐step process to achieve superhydrophobic surfaces. The results showed that silica nanoparticles were successfully incorporated into the FAP/SiO₂ nanocomposites, and a specific surface topography and a low surface free energy were simultaneously introduced onto PET fibers. The prepared PET fabric showed excellent superhydrophobicity with a water contact angle of 151.5° for a 5 μL water droplet and a water shedding angle of 12° for a 15 μL. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40340.     

Comprehensive high‐performance epoxy nanocomposites co‐reinforced by organo‐montmorillonite and nano‐SiO2

Comprehensive high‐performance epoxy nanocomposites were successfully prepared by co‐incorporating organo‐montmorillonite (o‐MMT) and nano‐SiO₂ into epoxy matrix. Because of the strong interaction between nanoscale particles, the MMT layers were highly exfoliated, and the exfoliated nanoscale MMT monoplatelets took an interlacing arrangement with the nano‐SiO₂ particles in the epoxy matrix, as evidenced by X‐ray diffraction measurement and transmission electron microscopy inspection. Mechanical tests and thermal analyses showed that the resulting epoxy/o‐MMT/nano‐SiO₂ nanocomposites improved substantially over pure epoxy and epoxy/o‐MMT nanocomposites in tensile modulus, tensile strength, flexural modulus, flexural strength, notch impact strength, glass transition temperature, and thermal decomposition temperature. This study suggests that co‐incorporating two properly selected nanoscale particles into polymer is one pathway to success in preparing comprehensive high‐performance polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Organic‐acid‐catalyzed sol–gel route for preparing poly(methyl methacrylate)–silica hybrid materials

In this study, a series of organic–inorganic hybrid sol–gel materials consisting of a poly(methyl methacrylate) (PMMA) matrix and dispersed silica (SiO₂) particles were successfully prepared through an organic‐acid‐catalyzed sol–gel route with N‐methyl‐2‐pyrrolidone as the mixing solvent. The as‐synthesized PMMA–SiO₂ nanocomposites were subsequently characterized with Fourier transform infrared spectroscopy and transmission electron microscopy. The solid phase of organic camphor sulfonic acid was employed to catalyze the hydrolysis and condensation (i.e., sol–gel reactions) of tetraethyl orthosilicate in the PMMA matrix. The formation of the hybrid membranes was beneficial for the physical properties at low SiO₂ loadings, especially for enhanced mechanical strength and gas barrier properties, in comparison with the neat PMMA. The effects of material composition on the thermal stability, thermal conductivity, mechanical strength, molecular permeability, optical clarity, and surface morphology of the as‐prepared hybrid PMMA–SiO₂ nanocomposites in the form of membranes were investigated with thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, gas permeability analysis, ultraviolet–visible transmission spectroscopy, and atomic force microscopy, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of photodegradable polypropylene/clay composites based on nanoscaled TiO2 immobilized organoclay

Photodegradable polypropylene (PP) composites were prepared via melting blending using PP and titanium dioxide (TiO₂) immobilized organically modified montmorillonite (organoclay). TiO₂ immobilized organoclay (TiO₂‐OMT) was synthesized by immobilizing anatase TiO₂ nanoparticles on organically modified clay via sol–gel method. The structure and morphology of TiO₂‐OMT were characterized by XRD and scanning electron microscope (SEM), which showed that anatase TiO₂ nanoparticles with the size range of 8–12 nm were uniformly immobilized on the surface of organoclay layers. Diffuse reflection UV–vis spectra revealed TiO₂‐OMT had similar absorbance characters to that of commercial photocatalyst, Degussa P25. The solid‐phase photocatalytic degradation of PP/TiO₂‐OMT composites was investigated by FTIR, DSC, GPC and SEM. The results indicated that TiO₂‐OMT enhanced the photodegradation rate of PP under UV irradiation. This was due to that immobilization of TiO₂ nanoparticles on organoclay effectively avoided the formation of aggregation, and thereby increased the interface between PP and TiO₂ nanoparticles. After 300 h irradiation, the average molecular weight was reduced by two orders of magnitude. This work presented a promising method for preparation of environment‐friendly polymer nanocomposites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.     

Phosphonium‐based layered silicate—Poly(ethylene terephthalate) nanocomposites: Stability,thermal and mechanical properties

PET‐clay nanocomposites were prepared using alkyl quaternary ammonium and phosphonium modified clays by melt‐mixing at 280°C using a micro twin screw extruder. The latter clays were prepared by synthesizing phosphonium surfactants using a simple one‐step method followed by a cation exchange reaction. The onset temperature of decomposition (T_onset) for phosphonium clays (>300°C) was found to be significantly higher than that of ammonium clays (around 240°C). The clay modified with a lower concentration (0.8 meq) of phosphonium surfactant showed a higher T_onset as compared to the clay modified with a higher concentration (1.5 meq) of surfactants. Nanocomposites prepared with octadecyltriphenyl phosphonium (C18P) modified clay showed a higher extent of polymer intercalation as compared with benzyltriphenylphosphonium (BTP) and dodecyltriphenylphosphonium (C12P) modified clays. The nanocomposites prepared with ammonium clays showed a significant decrease in the molecular weight of PET during processing due to thermal degradation of ammonium surfactants. This resulted in a substantial decrease in the mechanical properties. The molecular weight of PET was not considerably reduced during processing upon addition of phosphonium clay. The nanocomposites prepared using phosphonium clays showed an improvement in thermal properties as compared with ammonium clay‐based nanocomposites. T_onset increased significantly in the phosphonium clay‐based nanocomposites and was higher for nanocomposites which contained clay modified with lower amount of surfactant. The tensile strength decreased slightly; however, the modulus showed a significant improvement upon addition of phosphonium clays, as compared with PET. Elongation at break decreased sharply with clay. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Fumed SiO2 nanoparticle reinforced biopolymer blend nanocomposites with high dielectric constant and low dielectric loss for flexible organic electronics

In the present study, fumed silica (SiO₂) nanoparticle reinforced poly(vinyl alcohol) (PVA) and poly(vinylpyrrolidone) (PVP) blend nanocomposite films were prepared via a simple solution‐blending technique. Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–vis), X‐ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to elucidate the successful incorporation of SiO₂ nanoparticles in the PVA/PVP blend matrix. A thermogravimetric analyzer was used to evaluate the thermal stability of the nanocomposites. The dielectric properties such as dielectric constant (?) and dielectric loss (tan δ) of the PVA/PVP/SiO₂ nanocomposite films were evaluated in the broadband frequency range of 10^?2 Hz to 20 MHz and for temperatures in the range 40–150 °C. The FTIR and UV–vis spectroscopy results implied the presence of hydrogen bonding interaction between SiO₂ and the PVA/PVP blend matrix. The XRD and SEM results revealed that SiO₂ nanoparticles were uniformly dispersed in the PVA/PVP blend matrix. The dielectric property analysis revealed that the dielectric constant values of the nanocomposites are higher than those of PVA/PVP blends. The maximum dielectric constant and the dielectric loss were 125 (10^?2 Hz, 150 °C) and 1.1 (10^?2 Hz, 70 °C), respectively, for PVA/PVP/SiO₂ nanocomposites with 25 wt % SiO₂ content. These results enable the preparation of dielectric nanocomposites using a facile solution‐casting method that exhibit the desirable dielectric performance for flexible organic electronics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44427.     

Study of the preparation and properties of UV‐blocking fabrics of a PET/TiO2 nanocomposite prepared by in situ polycondensation

Poly(ethylene phthalate) (PET)/nano‐TiO₂ composites prepared via in situ polymerization were spun into fiber by the melt‐spinning process. The dispersion of nanosized rutile TiO₂ in the PET was studied using transmission electron microscopy (TEM) and scanning probe microscopy (SPM) techniques. The mechanical properties and the properties of ultraviolet (UV) protection were investigated. The results showed that rutile TiO₂ can be dispersed uniformly by the in situ polycondensation process. The mechanical properties of PET/TiO₂ fiber were slightly affected by adding nano‐TiO₂. The UV‐ray transmittance of PET/nano‐TiO₂ fabrics was below 10% in the UV‐A band and below 1% in the UV‐B band. And the ultraviolet protection factor (UPF) of PET/nano‐TiO₂ fabrics was greater than 50. All these PET/TiO₂ nanocomposite fabrics exhibited excellent UV‐blocking properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1588–1593, 2006     

Morphology enhancement of TiO2/PVP composite nanofibers based on solution viscosity and processing parameters of electrospinning method

In this work, different sol solutions with various titanium tetraisopropoxide (TIP)/glacial acetic acid ratios in 2‐propanol with 5 wt % poly(vinyl pyrrolidone) (PVP) (M_w = 360,000 g/mol) were prepared and electrospun. Composition of the prepared sols and as‐spun TiO₂/PVP nanofibers were determined by Fourier transform infrared and Raman spectroscopy methods. Morphology of the electrospun TiO₂/PVP nanofibers was studied by scanning electron microscopy and transmission electron microscopy (TEM) techniques. Rheometry measurements of the sol solutions showed decrease of viscosity upon the addition of TIP to the polymer solutions with constant polymer and acid concentrations. The sol solution having the lowest viscosity (at shear rate 10 s^?1) but the highest TIP/glacial acetic acid ratio showed beaded nanofibers morphology when electrospun under 10 and 12 kV applied voltage while injection rate, needle tip to collector distance, and needle gauge were kept constant. However, smooth electrospun TiO₂/PVP composite nanofibers with the average nanofibers diameters (148 ± 79 nm) were achieved under the same condition when applied voltage increased to 15 kV. TEM micrographs of the electrospun TiO₂/PVP nanofiber showed that the TiO₂ particles with continuous structure are formed at the middle of the nanofiber and distributed along its axis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46337.     

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     

Poly(L‐lactic acid)/silicone dioxide nanocomposites prepared via in situ melt polycondensation of L‐lactic acid in the presence of acidic silica sol: Dispersion stability of nanoparticles during dehydration/oligomerization

In this work, the stability of nanoparticles during the dehydration/oligomerization (D/O) stage in situ melt polycondensation of L ‐lactic acid to prepare poly(L ‐lactic acid) (PLLA)/SiO₂ nanocomposite was studied. The change in the appearance of the reaction mixture was tracked, and the resultant oligo(L ‐lactic acid) (OLLA)/SiO₂ and PLLA/SiO₂ nanocomposites were characterized by transmission electron microscopy, ¹H‐NMR, and light transmittance. The electric double layer and the grafted OLLA chains provided static and steric stabilities during the early and late phases, respectively. However, there existed an intermediate transitional phase with weak stability when the static stability was weakened, but sufficient steric stability had not yet been established; this led to soft or hard aggregation, depending on the SiO₂ loading and agitation conditions. At low or moderate SiO₂ loading (<5–10%), the soft aggregation could be depressed with appropriate agitation conditions and redispersed with the aid of gradually established steric interaction energy. Consequently, well‐dispersed PLLA/SiO₂ nanocomposites with SiO₂ loadings of 5 and 10% were successfully prepared by in situ melt polycondensation with an arc stirrer at 400 and 600 rpm, respectively, during the D/O stage. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Retracted: Effect of surface‐treated TiO2 on non‐isothermal crystallization behavior of poly trimethylene terephthalate nanocomposites

The study of the non‐isothermal crystallization behavior of poly(trimethylene terephthalate) (PTT)/TiO₂ nanocomposites using untreated and surface‐treated TiO₂ has been carried out with different theoretical models. The PTT/untreated TiO₂ and surface‐treated TiO₂ nanocomposites were prepared employing batch mixing technique with an aim to investigate the influence of the TiO₂ dispersion on the crystallization behavior. The nucleation efficiency of the TiO₂ nanoparticles has been demonstrated with the use of Avrami and Jeziorny models. Test results indicated that the PTT matrix with surface‐treated TiO₂ particles has higher crystallization temperature and melting point than those with untreated PTT/TiO₂ nanocomposites. Unlike untreated TiO₂, surface‐treated TiO₂ particles also showed less effect on the degree of crystallization of the PTT matrix. The TiO₂ nanoparticles act as a nucleating agent in the PTT matrix by reducing the t_½ of the crystallization time, thus making it easy to form crystals. © 2012 Society of Plastics Engineers     

Preparation and thermo-oxidative degradation of poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)/poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid)-grafted SiO<Subscript>2</Subscript> nanocomposites

Poly(l-lactic acid)/poly(l-lactic acid)-grafted SiO₂ nanocomposites were prepared by in situ melt polycondensation, in which “free” poly(l-lactic acid) and poly(l-lactic acid)-grafted SiO₂ nanoparticles were formed simultaneously. The maximum values of grafting ratio and grafting efficiency of poly(l-lactic acid) were up to 37.67% and 26.60%, respectively. In the polycondensation system, SiO₂ content was a critical parameter of getting nanocomposites with uniformly dispersed SiO₂ nanoparticles. At lower SiO₂ content, Mn of grafted poly(l-lactic acid) was close to that of “free” poly(l-lactic acid), and poly(l-lactic acid)-grafted SiO₂ nanoparticles could be well dispersed in poly(l-lactic acid) matrix. While at higher SiO₂ content, Mn of “free” poly(l-lactic acid) and grafted poly(l-lactic acid) decreased seriously, especially GPC curves of “free” poly(l-lactic acid) exhibited two peaks due to the aggregation of SiO₂ nanoparticles during the polycondensation process. The grafting ratio and SiO₂ content exhibited a clear effect on the thermo-oxidative degradation of nanocomposites. The existence of poly(l-lactic acid)-grafted SiO₂ nanoparticles dramatically improved the thermo-oxidative stability of poly(l-lactic acid). Compared with that of pure poly(l-lactic acid), T _g, T _c, and T _m of nanocomposites varied slightly.     

Preparation and performance of high‐impact polystyrene (HIPS)/nano‐TiO2 nanocomposites

High‐impact polystyrene (HIPS)/nano‐TiO₂ nanocomposites were prepared by surface pretreatment of nano‐TiO₂ with special structure dispersing agent (TAS) and master batch manufacturing technology. The results show that when the nano‐TiO₂ content is 2%, the notched impact strength, tensile strength, and elastic modulus of HIPS/nano‐TiO₂ nanocomposites increased to a maximum. This result indicates that nano‐TiO₂ has both toughening and reinforcing effects on HIPS. The heat‐deflection temperature and flame‐retardance of HIPS/nano‐TiO₂ nanocomposites are also obviously improved as the nano‐TiO₂ content is increased. The nanocomposites manufactured by the two‐step method have better mechanical properties than that made by a one‐step method. HIPS/nano‐TiO₂ nanocomposites are also non‐Newtonian and pseudoplastic fluids. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 381–385, 2003     

Transport Properties of Modified Montmorillonite‐Poly(ε‐caprolactone) Nanocomposites

A series of montmorillonite‐poly(ε‐caprolactone) nanocomposites were prepared according to a two‐stage procedure. In the first step Na‐type silicate clay was cation exchanged with protonated 12‐aminolauric acid. In the second step ε‐caprolactone was intercalated in the modified clay and ring‐opening polymerized. The clay content was varied regularly from 0 to 44 wt.‐%, with exfoliation of the silicate layers being detected by X‐ray diffraction in the nanocomposites dispersing up to at least 16 wt.‐% clay. Crystallization of poly(ε‐caprolactone) was not prevented in the nanocomposites, although it proceeded to a lower extent/order than in a homopolymer sample. The transport properties were investigated using water or dichloromethane as vapor permeants. In each case, a dual sorption behavior was observed as a function of the vapor activity because of the occurrence of different sorption mechanisms. The permeability of the nanocomposites to either permeant decreased with increasing clay content. In particular, the permeability behavior to water was largely dominated by the diffusion parameter.     

Preparation of poly(methyl methacrylate‐co‐maleic anhydride)/SiO2?TiO2 hybrid materials and their thermo‐ and photodegradation behaviors

The optically transparent poly(methyl methacrylate‐co‐maleic anhydride) P(MMA‐co‐MA)/SiO₂? TiO₂ hybrid materials were prepared using 3‐aminopropyl triethoxysilane as a coupling agent for organic and inorganic components. Real‐time FTIR was used to monitor the curing process of hybrid sol, indicating that imide group formation decreased with increasing titania content. scanning electron microscopy, atomic force microscopy, and differential scanning calorimetry results confirmed their homogeneous inorganic/organic network structures. TGA analysis showed that incorporated titania greatly prohibits the thermodegradation of hybrid films, especially at the content of 5.3 wt %, showing an increase of about 32.6°C at 5% loss temperature in air. The UV degradation behavior of P(MMA‐co‐MA) studied by quasi‐real‐time FTIR showed that TiO₂ incorporated in the hybrid network provides a photocatalytic effect rather than a UV‐shielding effect. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1714–1724, 2005     

Isothermal crystallization behavior of poly(L‐lactic acid)/organo‐montmorillonite nanocomposites

The isothermal crystallization behavior of poly(L ‐lactic acid)/organo‐montmorillonite nanocomposites (PLLA/OMMT) with different content of OMMT, using a kind of twice‐functionalized organoclay (TFC), prepared by melt intercalation process has been investigated by optical depolarizer. In isothermal crystallization from melt, the induction periods (t_i) and half times for overall PLLA crystallization (100°C ≤ T_c ≤ 120°C) were affected by the temperature and the content of TFC in nanocomposites. The kinetic of isothermal crystallization of PLLA/TFC nanocomposites was studied by Avrami theory. Also, polarized optical photomicrographs supplied a direct way to know the role of TFC in PLLA isothermal crystallization process. Wide angle X‐ray diffraction (WAXD) patterns showed the nanostructure of PLLA/TFC material, and the PLLA crystalline integrality was changed as the presence of TFC. Adding TFC led to the decrease of equilibrium melting point of nanocomposites, indicating that the layered structure of clay restricted the full formation of crystalline structure of polymer. The specific interaction between PLLA and TFC was characterized by the Flory‐Huggins interaction parameter (B), which was determined by the equilibrium melting point depression of nanocomposites. The final values of B showed that PLLA was more compatible with TFC than normal OMMT. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers