Non-isothermal crystallization kinetics of TiO2 nanoparticle-filled poly(ethylene terephthalate) with structural and chemical properties

The present research work includes non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET)–titanium dioxide (TiO₂) nanocomposites as well as structural and chemical properties of these nanocomposites. The average grain size of chemically synthesized TiO₂ nanoparticles has been calculated 19.31 nm by TEM and XRD. The morphology and structural analysis of PET–TiO₂ nanocomposites, prepared via solution casting method, has been investigated using SEM and XRD, respectively. The nature of chemical bonds has been discussed on the basis of FTIR spectra. The effect of TiO₂ nanoparticles and cooling rates on non-isothermal crystallization kinetics of PET was examined by differential scanning calorimetry at various heating and cooling rates. It has been observed that TiO₂ nanoparticles accelerate the heterogeneous nucleation in PET matrix. The crystallization kinetics could be explained through Avrami–Ozawa combined theory. TiO₂ nanoparticles cause to make molecular chains of PET easier to crystallize and accelerate the crystallization rates during non-isothermal crystallization process; this conclusion has also been verified by Kissinger model for crystallization activation energy.     

Fabrication of a New Polyimide/Titania (TiO2) Nanocomposite Thin Film by the Sol-Gel Route

Polyimide/titania nanocomposite (PI/TiO₂ NC) was successfully fabricated through the in situ formation of TiO₂ within a PI matrix by the sol-gel process. FT-IR and XRD results confirmed the formations of the TiO₂ in the PI matrix. Transmission electron microscopy of the NC10% showed that the TiO₂ phase was well dispersed in the polymer matrix. The mechanical properties of the NC films were increased and elongation at break decreased with increasing TiO₂ content. Thermogravimetric analysis results revealed that the decomposition temperature of hybrid materials was increased with an increase in the content of TiO₂ nanoparticles within the NC films.     

Polymer structure and morphology of low density polyethylene filled with silica nanoparticles

The effect of silica nanoparticles on structure and morphology of low density polyethylene (LDPE) was investigated. To prepare the nanocomposites, SiO₂ nanoparticles were dispersed in a LDPE with cryogenic high‐energy ball milling (HEBM). Films of these nanocomposites with different loads (0%, 1.8%, 2.3%, 3.3%, 7.9%, 16.5% wt/wt) were obtained by hot pressing. Differential scanning calorimetry (DSC) was used to study the nonisothermal melting and crystallization of the films. The morphological characterization was done by atomic force microscopy (AFM). To determine the most representative periodical spacing associated to the LDPE crystallites, a new approach based on the first moment of the frequency distribution obtained from the fast Fourier transform of the AFM phase contrast images was used. Ultracryomicrotomed surfaces of the nanocomposites revealed an efficient dispersion of the nanoparticles throughout the polymer bulk. Although HEBM promotes the formation of the metastable monoclinic phase in the LDPE, nanocomposites in the form of films did not show important differences in their thermal and morphological characteristics, suggesting that there are not high interactions between the polar nanoparticles and the nonpolar polymer and that thermal treatment is enough to eliminate the specific microstructure induced by HEBM. POLYM. COMPOS., 33:2009–2021, 2012. © 2012 Society of Plastics Engineers     

Effect of calcination temperature of TiO2 on the crystallinity and the permittivity of PVDF‐TrFE/TiO2 composites

Composite membranes of poly(vinylidene‐trifluoroethylene)/titanium dioxide (PVDF‐TrFE/TiO₂) were prepared by the solution cast method. The crystallization behavior and dielectric properties of the composites with TiO₂ calcined at different temperatures were studied. Transmission electron microscopy and X‐ray diffraction (XRD) results showed that the TiO₂ nanoparticles calcined at different temperatures were well dispersed in the polymer matrix and did not affect the structure of the PVDF‐TrFE matrix. XRD and differential scanning calorimeter measurements showed that the crystallinity of PVDF‐TrFE/TiO₂ composites increased as the addition of TiO₂ with different calcination temperatures. The dielectric property testing showed that the permittivity of PVDF‐TrFE/TiO₂ membrane increased rapidly with the increase of TiO₂ content and the calcination temperature of TiO₂ at constant TiO₂ content, but the dielectric loss did not change much. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of high energy ball milling on mechanical and interfacial properties of PBT/nano-Sb2O3 composites

In this work, the poly(butylene terephthalate) (PBT) nanocomposites containing modified nano-Sb₂O₃ particles were dispersed by two different dispersing techniques, including high speed rotating to disperse (HSR) and high energy ball milling to disperse (HEBM). The dispersion, interfacial interaction and mechanical properties of nanocomposites were investigated. The results showed that the dispersion and compatibility of nanocomposites dispersed by HEBM were better than that of HSR. From the analysis of interfacial interactions between nano-Sb₂O₃ particles and PBT matrix, the interfacial adhesion (B) and tensile strength of interfacial (σ_i) were decreased with the increase of nano-Sb₂O₃ particles content. The value of parameters B and σ_i of HEBM nanocomposites was higher than that of HSR, which indicated that the nanocomposites dispersed by HEBM had stronger interfacial interaction than that of HSR. As a result, the nanocomposites dispersed by HEBM had better mechanical properties than that of HSR.     

Nucleation effect of surface treated TiO2 on Poly(trimethylene terephthalate) (PTT) nanocomposites

A study of the nucleation effect of TiO₂ in poly(trimethylene terephthalate)/TiO₂ nanocomposite has been carried out using different theoretical models. The models were applied and developed with the aim to describe and better understand the influence of the TiO₂ dispersion on crystallization characteristics of PTT. The PTT/TiO₂ nanocomposites with untreated and surface‐treated TiO₂ were prepared by the melt mixing method. The nucleation efficiency of the TiO₂ nanoparticles has been analyzed with the use of the Avrami model and Mo's method. It was found that the PTT matrix incorporated with surface‐treated TiO₂ particles has a higher crystallization temperature and melting point than that incorporated with untreated TiO₂ particles. As per the models, unlike untreated TiO₂, surface‐treated TiO₂ particles had a lesser effect on the degree of crystallization of the PTT matrix. The TiO₂ nanoparticles act as a nucleating agent in the PTT matrix thereby reducing t_½ of the crystallization and leading to easier crystallization of the polymer. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal properties and crystallization behavior of bamboo fiber/high‐density polyethylene composites: Nano‐TiO2 effects

In this study, bamboo fiber/high‐density polyethylene (HDPE) composites were prepared, and the effects of nano‐TiO₂ on their thermal properties and crystallization behavior were investigated via thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results show that the addition of nano‐TiO₂ improved the thermal stability and had a dual function in the crystallization behavior of the composites. On one hand, it functioned as a nucleating agent. The addition of 2 wt % nano‐TiO₂ promoted the crystallization, which caused the increase of the crystallization rate and crystallinity degree, as well as the micronization of the crystalline grain. On the other hand, intermolecular hydrogen bonds and covalent bonds were formed between nano‐TiO₂ and the polymer matrix, which hindered the crystallization of the composites. When the content of nano‐TiO₂ was continually increased, the inhibitory effect of the crystallization was gradually enhanced, which resulted in a decrease in the crystallization rate and crystallinity degree of the composites. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39846.     

Biodegradable Polycaprolactone-Titania Nanocomposites: Preparation,Characterization and Antimicrobial Properties

Nanocomposites obtained from the incorporation of synthesized TiO₂ nanoparticles (≈10 nm average primary particle size) in different amounts, ranging from 0.5 to 5 wt.%, into a biodegradable polycaprolactone matrix are achieved via a straightforward and commercial melting processing. The resulting nanocomposites have been structurally and thermally characterized by transmission electron microscopy (TEM), wide/small angle X-ray diffraction (WAXS/SAXS, respectively) and differential scanning calorimetry (DSC). TEM evaluation provides evidence of an excellent nanometric dispersion of the oxide component in the polymeric matrix, with aggregates having an average size well below 100 nm. Presence of these TiO₂ nanoparticles induces a nucleant effect during polymer crystallization. Moreover, the antimicrobial activity of nanocomposites has been tested using both UV and visible light against Gram-negative Escherichia coli bacteria and Gram-positive Staphylococcus aureus. The bactericidal behavior has been explained through the analysis of the material optical properties, with a key role played by the creation of new electronic states within the polymer-based nanocomposites.     

Preparation and characterization of nano‐Sb2O3/poly(butylene terephthalate) composite powders based on high‐energy ball milling

In this work, a kind of composite powders with good dispersion and distribution of nano‐Sb₂O₃ particles in poly(butylene terephthalate) (PBT) was prepared by the high‐energy ball milling (HEBM). The effects of the milling time on the structure, morphology, particle size distribution, and thermal behavior of the nano‐Sb₂O₃/PBT composite powders were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, laser diffraction particle size analyzer, and thermal analysis (TGA, DTG and DSC) techniques. The results showed that the regular shape of PBT powders was converted into flakes and the nano‐Sb₂O₃ particles were well deagglomerated and better dispersed in the PBT matrix during the HEBM process. The mechanochemical activation that was provided by the HEBM process caused a reduction in the molecular weight of PBT, which result in favoring the first step of thermal degradation. Furthermore, two T_g’s were obtained in the case of the nanocomposite powders when the milling time was over 3 h, one of them being slightly higher than that of the pure PBT, which indicated that there was a special interaction between PBT and nano‐Sb₂O₃ particles. However, the HEBM process leaded to a decreasing of the PBT crystallinity. J. VINYL ADDIT. TECHNOL., 25:91–97, 2019. © 2018 Society of Plastics Engineers     

The effect of high-energy ball milling on the electromechanical strain properties of Bi-based lead-free relaxor matrix ferroelectric composite ceramics

The crystal structure, ferroelectric, and electric-field-induced strain (EFIS) properties of Bi-based lead-free ferroelectric/relaxor composite materials are investigated. Bi_1/2(Na_0.82K_0.18)_1/2TiO₃ as a ferroelectric material and 0.98Bi_1/2(Na_0.78K_0.22)_1/2TiO₃‒0.02LaFeO₃ as a relaxor were synthesized via conventional ceramic processing routes while the relaxor (matrix phase) was prepared via high-energy ball milling (HEBM) after calcination. The average particle size was decreased via HEBM treatment. As a result, a high d₃₃^* value of over 600 pm/V was obtained at 4 kV/mm for 30-min HEBM-treated composites. This demonstrates that HEBM treatment is effective in enhancing the strain properties of lead‒free piezoelectric composite materials.     

Synthesis and structural characterization of novel bionanocomposite poly(ester-imide)s containing TiO2 nanoparticles, S-valine, and l-tyrosine amino acids moieties

The incorporation of different percents of titanium dioxide (TiO₂) nanoparticles into optically active poly(ester-imide) (PEI), afforded an opportunity to prepare several novel PEI/TiO₂ bionanocomposites (BNC)s. To this point, firstly PEI was synthesized via direct polyesterification of chiral diacid monomer and an optically active phenolic diol using tosyl chloride/pyridine/N,N-dimethylformamide system as a condensing agent. Novel BNC polymers containing TiO₂ nanoparticles were synthesized through ultrasonic irradiation method. With the aim of γ-amidopropyl-triethoxylsilicane as a coupling agent, the surface of nanoscale TiO₂ was modified to decrease aggregation of nanoparticles in polymer matrix. The obtained PEI/TiO₂ BNCs were characterized with FT-IR, thermogravimetric analysis (TGA), scanning electron microscopy, X-ray diffraction, and transmission electron microscopy (TEM) techniques. Consequently, TEM image showed that the nanoparticles of smaller than 50 nm in diameter were uniformly dispersed in the polymer matrix. TGA data demonstrated that new synthesized PEI/TiO₂ BNCs are more thermally stable in compare to pure PEI.     

Preparation and characterization of TiO2 and polymer nanocomposite films with high refractive index

Novel nanocomposite films of TiO₂ nanoparticles and hydrophobic polymers having polar groups, poly (bisphenol‐A and epichlorohydrin) or copolymer of styrene and maleic anhydride, with high refractive indices, high transparency, no color, solvent‐resistance, good thermal stability, and mechanical properties were prepared by incorporating surface‐modified TiO₂ nanoparticles into polymer matrices. In the process of preparing colloidal solution of TiO₂ nanoparticles, severe aggregation of particles can be reduced by surface modification using carboxylic acids and long‐chain alkyl amines. These TiO₂ nanoparticles dispersed in solvents were found not to aggregate after mixing with polymer solutions. Transparent colorless free‐standing films were obtained by drying a mixture of TiO₂ nanoparticles colloidal solution and polymer solutions in vacuum. Transmission electronic microscopic studies of the films suggest that the TiO₂ nanoparticles of 3–6 nm in diameter were dispersed in polymer matrices while maintaining their original size. Thermogravimetric analysis results indicate that the nanocomposite film has good thermal stability and the weight fraction of observed TiO₂ nanoparticles in the film is in good accordance with that of theoretical calculations. The refractive index of nanocomposite films of TiO₂ and poly(bisphenol‐A and epichlorohydrin) was in the range of 1.58–1.81 at 589 nm, which linearly increased with the content of TiO₂ nanoparticles from 0 to 80 wt %. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Isothermal crystallization of high density polyethylene and nanoscale calcium carbonate composites

High density polyethylene (HDPE) and calcium carbonate (CaCO₃) nanocomposites with maleic anhydride grafted HDPE (manPE) as a compatibilizer were prepared via compounding in a twin‐screw extruder. The CaCO₃ are well dispersed in the HDPE matrix from the observation of transmission electron microscope. The isothermal crystallization kinetics was studied by differential scanning calorimetry and simulated by Avrami and Tobin models. The nucleation constants and fold surface free energy were estimated from Lauritzen–Hoffman relation. The results indicate that both manPE and well‐dispersed CaCO₃ particles would act as nuclei to induce heterogeneous nucleation and enhance crystallization rate. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of hydrothermally synthesized titanium nanotubes on the behaviour of polypropylene for antimicrobial applications

TiO₂ nanotubes (TiO₂‐Ntbs) synthesized by a hydrothermal method were used as filler to prepare polypropylene (PP) composites by melt blending. Their structural properties as well as their biocidal potential were studied. Nanotubes were used either as‐synthesized or organically modified with hexadecyltrimethoxysilane (Mod‐TiO₂). These nanoparticles form secondary structures with sizes around 100 nm that are well dispersed in the polymer matrix, but not homogeneously because agglomerates larger than 1 µm are also seen by transmission electron microscopy. Regarding the properties of the composites, the incorporation of the nanoparticles increased the polymer's crystallinity and thermal stability. The maximum decomposition temperature of the matrix increased by ca 13 °C compared to virgin PP. The nanotubes further increase the spherulite nucleation density, and therefore a reduction in the diameter of spherulites and an increase in their number were observed. Despite the above, the addition of TiO₂ nanoparticles did not modify the mechanical properties of PP. The PP/TiO₂‐Ntb nanocomposites exposed to UVA radiation showed a biocidal behaviour, reducing a colony of Escherichia coli by 81%. © 2015 Society of Chemical Industry     

Impact of particle morphology on structure,crystallization kinetics,and properties of PCL composites with TiO<Subscript>2</Subscript>-based particles

Crystallization kinetics of polycaprolactone (PCL) filled with TiO₂-based particles (TiX) was shown to depend on the TiX particle type and concentration, which were associated with a slight polymer matrix degradation. The partially degraded, shorter, and more mobile polymer chains increased the overall crystallization rate at the initial stage of crystallization, while at the later stages, the non-nucleating TiX particles acted as a sterical hindrance, slowing down the crystallization process. The PCL/TiX composites were prepared by melt-mixing and contained 2.5 and 5 wt% of the filler. The investigated TiX particles included isometric anatase microparticles (mTiO₂) and titanate nanotubes with high-aspect ratio (TiNT). Light and electron microscopy showed very homogeneous dispersion of the mTiO₂ particles in the PCL matrix, while the TiNT formed large agglomerates. In situ polarized light microscopy displayed faster isothermal crystallization of all PCL/TiX composites, but the micrographs indicated that the TiX particles did not act as nucleation centres. Isothermal DSC experiments, evaluated in terms of Avrami theory, confirmed the PLM results and showed that the overall rate of isothermal crystallization increased in the following order: PCL <PCL/TiNT <PCL/mTiO₂. Non-isothermal DSC and rheological measurements revealed the correlation between the crystallization rate and the polymer matrix degradation—the well-dispersed mTiO₂ particles with high specific surface caused the highest PCL degradation and, consequently, the earliest start of non-isothermal crystallization as well as the fastest isothermal crystallization. Microindentation hardness measurements confirmed that the partial degradation of the polymer matrix did not have a significant impact on the mechanical performance of PCL/mTiO₂ composites.     

Mechanical properties and nonisothermal crystallization kinetics of polyamide 6/functionalized TiO2 nanocomposites

Titanium dioxide (TiO₂) nanoparticles were pretreated with excessive toluene‐2,4‐diisocyanate (TDI) to synthesize TDI‐functionalized TiO₂ (TiO₂‐NCO), and then polymeric nanocomposites consisting of polyamide 6 (PA6) and functionalized‐TiO₂ nanoparticles were prepared via a melt compounding method. The interfacial interaction between TiO₂ nanoparticles and polymeric matrix has been greatly improved due to the isocyanate ( NCO) groups at the surface of the functionalized‐TiO₂ nanoparticles reacted with amino groups ( NH₂) or carboxyl ( COOH) groups of PA6 during the melt compounding and resulted in higher tensile and impact strength than that of pure PA6. The nonisothermal crystallization kinetics of PA6/functionalized TiO₂ nanocomposites was investigated by differential scanning calorimetry (DSC). The nonisothermal crystallization DSC data were analyzed by the modified‐Avrami (Jeziorny) methods. The results showed that the functionalized‐TiO₂ nanoparticles in the PA6 matrix acted as effective nucleation agents. The crystallization rate of the nanocomposites obtained was faster than that of the pure PA6. Thus, the presence of functionalized‐TiO₂ nanoparticles influenced the mechanism of nucleation and accelerated the growth of PA6 crystallites. POLYM. COMPOS., 35:294–300, 2014. © 2013 Society of Plastics Engineers     

Non-isothermal crystallization kinetics of poly(ethylene terephthalate)/mica composites

The non-isothermal crystallization kinetics of pure poly(ethylene terephthalate) (PET), PET/mica and PET/TiO₂-coated mica composites were investigated by differential scanning calorimetry with different theoretical models, including the modified Avrami method, Ozawa method and Mo method. The activation energies of non-isothermal crystallization were calculated by Kissinger method and Flynn–Wall–Ozawa method. The results show that the modified Avrami equation and Ozawa theory fail to describe the non-isothermal crystallization behavior of all composites, while the Mo model fits the experiment data fair well. It is also found that the mica and TiO₂-coated mica could act as heterogeneous nucleating agent and accelerate the crystallization rates of PET, and the effect of TiO₂-coated mica is stronger than that of mica. The result is further reinforced by calculating the effective activation energy of the non-isothermal crystallization process for all composites using the Kissinger method and the Flynn–Wall–Ozawa method.     

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     

Polyimide/nano-TiO2 hybrid films having benzoxazole pendent groups: In situ sol–gel preparation and evaluation of properties

Polyimide/titania (PI/TiO₂) nanocomposite films have been successfully fabricated through the in situ formation of TiO₂ within a PI matrix via sol–gel method. Poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by mixing pyromellitic dianhydride (PMDA), with equimolar amount of a diamine monomer having a pendent benzoxazole unit and two flexible ether linkages in N,N-dimethylformamide (DMF) solvent. Tetraethyl orthotitanate [Ti(OEt)₄] and acetylacetone were then added to the resulted PAA. After imidization at high temperature, PI/TiO₂ hybrid films were formed. The structure and morphology of the hybrid nanocomposites with different titania contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results indicate that the TiO₂ nanoparticles were homogeneously dispersed in the hybrid films. The thermogravimetric analysis of nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. Transmission electron microscopy showed that the nanoparticles with an average diameter of 25–40 nm were dispersed in the polymer matrix.     

Crystallization behavior of poly(ϵ‐caprolactone)/Tio2 nanocomposites obtained by in situ polymerization

Poly(?‐caprolactone) (PCL)/titanium dioxide (TiO₂) nanocomposites were prepared by in situ polymerization of ?‐caprolactone in the presence of modified‐TiO₂ nanoparticles as initiators. The molecular weight of PCL matrix was dependent on the amount of the TiO₂ fillers. The incorporation of TiO₂ did not significantly affect the crystalline structure of PCL. Moreover, a tendency of the nanoparticles to form aggregates was observed, especially at higher fillers contents. The analysis of the crystallization process showed that the addition of TiO₂ nanoparticles accelerated the crystallization rate of PCL, and the crystallization rates increased by increasing the filler content. The crystallization activation energy dependence on the filler content observed here is probably the consequence of the two competing factors. The tendency of activation energy obtained by nonisothermal crystallization is similar to that of isothermal crystallization. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers