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.     

Photostabilization of polypropylene by surface modified rutile‐type TiO2 nanorods

Rutile‐type titanium dioxide (TiO₂) nanorods were prepared, superficially modified and tested for the protection of polypropylene (PP) from the UVB and UVC irradiations. The silica coating blocked the active sites on the nanorods and the following calcination further reduced the amount of surface hydroxyl groups and thus, made the TiO₂ nanorods more efficient against the photodegradation. Compared with spherical TiO₂ nanoparticles, the calcined silica‐coated TiO₂ nanorods demonstrated good photostabilization efficiency due to the excellent shielding effect and the improved dispersion of the nanoparticles in PP matrix. When used in combination with the conventional hindered amine light stabilizer (HALS), CHIMASSORB^® 944, the surface modified TiO₂ nanorods revealed strong synergistic effect during the photo‐oxidation of the PP composites. The capacity of photostabilization was much higher than the combination with the commercial spherical TiO₂ nanoparticles and even higher than the typical HALS photostabilization system containing hindered phenol TINUVIN^® 328. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40601.     

Role of reactive compatibilization in preparation of nanosilica/polypropylene composites

The effect of reactive compatibilization on the mechanical properties of nanosilica filled polypropylene (PP) composites was studied in this work. First, the nanoparticles were grafted with poly(glycidyl methacrylate) (PGMA) by solution free‐radical polymerization, and then melt blended together with PP matrix and aminated PP (PP‐g‐NH₂) that acts as reactive compatibilizer. The reaction between epoxide groups of the grafted PGMA on the nanoparticles and amine groups of PP‐g‐NH₂ during compounding greatly improved interfacial interaction in the composites. As a result, tensile strength, Young's modulus, and notch impact strength of PP composites were increased at rather low filler content. The experimental results indicated that the reinforcing and toughening effects were controlled by flexibility of the grafted polymer as well as processing methods. POLYM. ENG. SCI., 47:499–509, 2007. © 2007 Society of Plastics Engineers.     

Isothermal crystallization and melting behaviors of nano TiO2‐modified polypropylene/polyamide 6 blends

Titanium dioxide (TiO₂) nanoparticles were functionalized with toluene‐2,4‐diisocyanate and then polypropylene/polyamide 6/(PP/PA6) blends containing functionalized‐TiO₂ were prepared using a twin screw extruder. Isothermal crystallization and melting behavior of the as‐prepared composites were investigated using differential scanning calorimetry and wide‐angle X‐ray diffraction. Isothermal crystallization analysis shows that the TiO₂ nanoparticles have two effects on PP/PA6 blends, i.e., it can favor the improvement of crystallization ability and decrease the crystallization rate of PP/PA6 blends. The improvement of crystallization ability is superior over decreasement of crystallization rate of PA6 chains caused by TiO₂, therefore PA6 in PP/PA6/TiO₂ nanocomposites have higher crystallization rate than that of PA6 in pure PP/PA6 blends, which indicated TiO₂ nanoparticles favored the crystallization of PA6. The TiO₂ nanoparticles show no effects on the equilibrium melting temperature (T) values of PP phase but decreases the T values of PA6 phase. In addition, the TiO₂ nanoparticles did not change the crystalline polymorph of PP/PA6 blends basically; however, favored the formation of β‐PP. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Hybridizing MWCNT with nano metal oxides and TiO2 in epoxy composites: Influence on mechanical and thermal performances

In this study, the effects of multi‐walled carbon nanotubes (MWCNT), and its hybrids with iron oxide (Fe₂O₃) and copper oxide (CuO) nanoparticles on mechanical characteristics and thermal properties of epoxy binder was evaluated. Furthermore, simultaneous effects of using MWCNT with TiO₂ as pigment and CaCO₃ as filler for epoxy composites were determined. To investigate effects of nano‐ and micro‐particles on epoxy matrix, the samples were evaluated by TGA and DTA. It was found that the hybrid of MWCNT with nano metal oxides caused considerable increment in the tensile and flexural properties of epoxy samples in comparison to the single MWCNT containing samples at the same filler contents. Significant improvement in the thermal conductivity of epoxy samples was obtained by using TiO₂ pigment along with MWCNT. The TiO₂ pigment also caused considerable improvement in mechanical properties of the epoxy matrix and the MWCNT containing nanocomposite. The best mechanical and thermal properties of epoxy nanocomposites were obtained at 1.5 wt % of MWCNT and 7 wt % of TiO₂ that it should be attributed to particle network forming of the particles which cause better nano/micro dispersion and properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43834.     

Study of PET/PP/TiO2 microfibrillar‐structured composites,Part 2: Morphology and mechanical properties

Uncompatibilized and compatibilized (polypropylene grafted maleic anhydride as compatibilizer) polyethylene terephthalate (PET)/polypropylene (PP)/TiO₂ microfibrillar composites (MFC) were prepared by injection molding of the pelletized PET/PP/TiO₂ drawn strands. The morphology of PET fibrils and the distribution of TiO₂ particles in the composites were examined. After injection molding the preferential location of TiO₂ particles is still preserved. Because of the reinforcement effect of PET fibrils, the tensile properties and impact strength of the PET/PP MFC are improved compared with the pure PP. Incorporation of TiO₂ particles results in decrease of both tensile strength and impact strength of the composites. However, the compatibilized PET/PP/TiO₂ MFC demonstrate better mechanical properties compared with the uncompatibilized ones. DMA analysis shows that the glass transition temperature (T_g) of PET in the uncompatibilized PET/PP/TiO₂ MFC and the T_g of PP in the compatibilized PET/PP/TiO₂ MFC are elevated by about 2°C. The elevation of T_g is attributed to the preferential location of TiO₂ particles in the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Low‐temperature synthesis of Mg(OH)2 nanoparticles from MgO as halogen‐free flame retardant for polypropylene

Mg(OH)₂ (MH) nanoparticles were synthesized by hydration of the light‐burned MgO at low temperature (70°C). Effects of additives, such as magnesium nitrate and magnesium acetate, on the size, morphology and agglomeration of MH particles were investigated. MH nanoparticles have platelet‐like structure and approximately 20–40 nm in thicknesses. The supersaturation degree plays an important role in magnesia hydration and is defined. When magnesium acetate was used as the additive, the hydroxyl ion can be homogeneously introduced into the solution. The size and morphology of MH nanoparticles are more homogeneous. Modified by titanate coupling agent, MH nanoparticles were used as the flame retardant for polypropylene (PP). The combustibility, mechanical properties and thermal behaviors of the PP/MH composites were characterized. The mechanical properties of PP/MH composites are not seriously deteriorated with increasing MH content. When the amount of MH fraction reached 65, the limiting oxygen index (LOI) value and UL 94 testing result of MH65 are 33.8 and V‐0 grading, respectively. The onset temperature (T_10%) and the maximum thermal decomposition temperature (T_max) of MH65 separately increased by approximately 100°C and 77°C than those of neat PP. Copyright © 2012 John Wiley & Sons, Ltd.     

Interfacial agent effect on rheological response and crystallite characteristics in germicidal polypropylene/titanium dioxide nanocomposites

Germicidal nanocomposites based on metallocene isotactic polypropylene (iPP) and titanium dioxide (TiO₂) nanoparticles have been prepared at a constant TiO₂ content of 2 wt%. Different quantities of a polypropylene wax partially grafted with maleic anhydride (PP‐g‐MAH) are employed to improve the polymer‐nanoparticle compatibility. Remarkable biocidal capabilities of these TiO₂ nanocomposites have been found and their crystalline structure and thermal and rheological responses explored. Several very interesting features have been found in these germicidal nanocomposites. On the one hand, rheological parameters do not change significantly with respect to those exhibited by pure iPP. This is extremely advantageous for the processing of these compounds since they can be transformed under similar conditions to those employed for iPP. On the other hand, the existence of two polymorphs is observed independent of the amount of compatibilizer used. The enhancement in polymer‐nanoparticle interactions by effect of the interfacial (PP‐g‐MAH) component is appraised looking at dynamical mechanical relaxations as a function of temperature and at crystallization processes of the various nanocomposites. Copyright © 2012 Society of Chemical Industry     

Structural and ultraviolet‐protective properties of nano‐TiO2‐doped polypropylene filaments

Textiles, with appropriate light absorbers and suitable finishing methods, can be used as ultraviolet (UV) protection materials. In this study, we investigated the effects of nano‐TiO₂ particles on the UV‐protective and structural properties of polypropylene (PP) textile filaments. Master batches of PP/TiO₂ nanoparticles were prepared by melt compounding before spinning, and filaments incorporating 0.3, 1, and 3% TiO₂ nanoparticles were spun in a pilot melt‐spinning machine. The structural properties of the nanocomposite fibers were analyzed with scanning electron microscopy, X‐ray diffractometry, differential scanning calorimetry, and tensile tests. The UV‐protection factor was determined to evaluate the UV‐protective properties of the filaments. In conclusion, although the structure and mechanical properties of the nanocomposite filaments were slightly affected by the addition of nano‐TiO₂, the UV‐protective properties of the PP filaments improved after treatment with nano‐TiO₂, and the nanocomposite filaments exhibited excellent UV protection. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

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     

Mechanical enhancement of amine‐functionalized TiO2 reinforced polyimine composites

Polyimine vitrimers are known for their malleability, which endows these materials with properties such as self‐healing, recycling, and reshaping. To enhance the mechanical properties of the polyimine vitrimers, composites were fabricated by incorporating amine‐functionalized TiO₂ microspheres (amTiO₂MS) into polyimine matrix. The pure polyimine matrix and polyimine composites hybridized with TiO₂ microspheres (TiO₂MS) without surface modification were also obtained and examined as the controls in characterization. X‐ray powder diffraction, scanning electron microscopy, and energy dispersive X‐ray spectroscopy were employed to demonstrate the presence and distribution of amTiO₂MS and TiO₂MS in the polyimine matrices. The investigation of mechanical properties of the amTiO₂MS enhanced polyimine composites and control samples indicated that incorporation of amTiO₂MS and TiO₂MS exhibited different characteristic distribution, which strongly affected the performance of the composites. The optimal filling concentration of amTiO₂MS was found to be 3%, with which the microspheres were uniformly distributed in the polyimine matrix. The self‐healing behavior of the polyimine‐amTiO₂‐X was also studied. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46446.     

Effects of carbon‐coated titanium dioxide nanoparticles as a photostabilizer on the photodegradation of rigid poly(vinyl chloride)

In this study, nanocomposites of rigid poly(vinyl chloride) (UPVC) using the synthesized carbon‐coated titanium dioxide (TiO₂) nanoparticles and commercial powder of titanium dioxide (with rutile structure) were prepared by melt blending. The presence of carbon‐coated TiO₂ nanoparticles with rutile structure in UPVC matrix led to an improvement in photo stability of UPVC nanocomposites in comparison with commercial UPVC. The photocatalytic degradation behavior of nanocomposites was investigated by measuring their structural changes, surface tension, and mechanical and morphological properties before and after UV exposure for 700 h. It was found that mechanical and physical properties of UPVC nanocomposites are not considerably reduced after UV exposure in the presence of carbon‐coated TiO₂ nanoparticles even in small percentage of nanoparticles in comparison with the presence of commercial TiO₂ particles. Therefore, it can be concluded that UPVC/TiO₂ nanocomposite with low content of carbon‐coated TiO₂ nanoparticles(0.25 wt %) illustrated high stability under light exposure. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40228.     

Dispersion of TiO2 Particles in PET/PP/TiO2 and PET/PP/PP‐g‐MA/TiO2 Composites Prepared with Different Blending Procedures

2 vol.‐% TiO₂ particles were incorporated into PET/PP blends with and without MA‐grafted PP compatibilizer. During extrusion of the PET/PP/TiO₂ composites the TiO₂ particles migrated from the PP matrix to the PET‐dispersed phase irrespective of the blending route. For the PET/PP/PP‐g‐MA/TiO₂ composites, however, the location of TiO₂ depended on the blending sequence. The preferred location of the TiO₂ nanoparticles was confirmed by SEM pictures taken from the chemically etched surface of the blends. The observed migration behavior was traced to differences in the interfacial tensions between TiO₂ and PET and TiO₂ and PP, and to TiO₂ encapsulation in one of the blend components during the related blending procedure.

     

Nanocomposites of polypropylene/titanate nanotubes: morphology,nucleation effects of nanoparticles and properties

High-quality titanate nanotubes (TiNT) were mixed with modified polypropylene (PP*) by a batch melt-mixing procedure. To improve compatibility between the nanofiller and the matrix, polypropylene (PP) was modified by electron beam irradiation. Effects of TiNT nanoparticles on crystallization, mechanical, thermal and rheological properties of the modified polypropylene were studied and compared with the analogous systems filled with commercial micro- (mTiO₂) and nano- (nTiO₂) titanium dioxide particles. Nucleation effects of the TiO₂-based fillers on PP* crystallization were investigated in detail. The microstructure of the PP*/TiNT nanocomposites shows well-dispersed TiNT sparse aggregates (clouds), penetrated by the polymer. A large-scale structure in the nanocomposite melts confirmed also rheology. In comparison to the matrix characteristics, the stiffness and microhardness of the TiNT nanocomposites increase by 27 and 33 %, respectively. The enhancement in mechanical properties demonstrates that the quality titanate nanotubes can be used as an efficient filler in non-polar polymers using the polymers modified by irradiation. In the case of the nanocomposites containing nTiO₂-anatase particles, the increase in these mechanical characteristics is lower. The investigated changes in the rate of crystallization indicate a marked nucleation effect of the nanotubes. The crystallization kinetics data, processed by the Avrami equation, suggest 3-dimensional crystal growth in the polypropylene matrix. The observed improvement in mechanical properties of the TiNT nanocomposites is induced not only by the nanofiller reinforcement but also by the changes of supermolecular structure of the polymer matrix due to nucleated crystallization.     

A simple approach to prepare PMA/TiO2 composite: The homogeneous dispersion of nano TiO2 in maleic anhydride polymer matrix

This contribution reports a simple approach for preparing PMA/TiO₂ composite. In this method, nano TiO₂ powders are previously treated by a combined modification process, namely, the alkali‐treatment followed by oleic acid surface‐grafting. Before polymerization, the modified TiO₂ nanoparticles are dispersed into the maleic anhydride (MA) solution to form stable homogeneous gel. When the reaction temperature is raised to 150°C, the modified nano TiO₂ can initiate the in situ anionic polymerization of MA. Finally, the PMA/TiO₂ composites are obtained, in which all the TiO₂ are fully coated by MA polymer (PMA). Therefore, it is not needed to reclaim the nano initiators because they are blended into the prepared polymers as the nano fillers. TEM and SEM experiment results can strongly demonstrate that the TiO₂ nanoparticles are homogeneously dispersed in PMA matrix. This approach is easy‐to‐operate and applicable to the preparation of other nano composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Plasticized poly(vinyl chloride) composites: Influence of different nanofillers as antimigration agents

In this study, plasticized poly(vinyl chloride) (PVC) composites with different nanofillers, including single‐walled carbon nanotubes (SWCNTs), organoclay, TiO₂, and ZnO nanoparticles, were prepared, and their effects on plasticizer migration were investigated. Scanning electron micrographs revealed the dispersion quality of the nanofillers in the polymer matrix. It had a significant influence on the performance of the nanofillers in the process of plasticizer migration. Migration and exudation tests showed that the nanofillers could efficiently hinder plasticizer migration. On the basis of these results, we concluded that carbon nanotubes were the best antimigration agent in the plasticized system. This was ascribed to the high aspect ratio of the SWCNTs and the good interactions between them and the plasticizer. Also, TiO₂ nanoparticles showed a better performance compared to the ZnO nanoparticles. This was due to the more homogeneous dispersion of the TiO₂ in the polymer matrix and the higher surface area of the particles. The differential scanning calorimetry thermograms were in good agreement with the migration tests. The lowest change in the glass‐transition temperature was observed for the composite filled with SWCNTs. This indicated that a lower amount of the plasticizer migrated from PVC. The thermogravimetric analysis curves showed that the incorporation of the nanofillers improved the thermal stability of the PVC. The results could be useful for determining the efficiency of plasticized PVC in applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42559.     

Synthesis and Characterization of TiN‐coated Cubic Boron Nitride Powders

Titanium nitride‐coated cubic boron nitride (TiN/cBN) composite powders were prepared by nitridizing TiO₂/cBN powders in a NH₃ flow at 950°C. The TiO₂/cBN powders were synthesized via a sol‐gel process using tetra‐butyl titanate and concentrated‐HNO₃‐treated BN powders as starting materials. The techniques of XRD, SEM, TEM, FT‐IR, and TG‐DTA were used to characterize the products and their intermediates. The cBN powders were uniformly coated with TiN nanoparticles. During the nitridization, the morphology of the TiO₂/cBN powders is unchanged. The TiN/cBN powders can be used as starting materials to prepare polycrystalline cBN compacts, or as reinforcements to strengthen metal‐matrix composites.     

Melt-spinning and thermal stability behavior of TiO<Subscript>2</Subscript> nanoparticle/polypropylene nanocomposite fibers

The elongational flow properties of TiO₂ nanoparticle/polypropylene (PP) nanocomposite fibers were studied via melt spinning. The diameter, tension, and flow rate of fibers were directly measured and used to calculate the apparent elongational viscosity and apparent elongational strain rate using Cogswell’s theory. Thermal gravimetric analysis (TGA) was used to demonstrate that the TiO₂ nanoparticles improved the thermal stability of the PP fibers. With a 1–3 wt % loading of the TiO₂ nanoparticles, the PP fiber decomposition temperatures ranged from 338 °C for the pristine polymer to 342, 349, and 367 °C; the decomposition was accompamied by an initial 95 wt % weight loss. In addition, the well-distributed morphology of the TiO₂ nanoparticles on the side surface of the PP matrix was observed using atomic force microscopy (AFM). At 1 wt % loading of the TiO₂ nanoparticles, the surfaces of the PP nanofibers contained mono-disperse nanoparticles with sizes of 20–50 nm. Furthermore, the TiO₂ nanoparticle/PP nanocomposite fibers were shown to be thermally stable and are suitable for application as an antibacterial polymer.     

Microwave absorption properties of double‐layer nanocomposites based on polypyrrole/natural rubber

Thin flexible double‐layer microwave absorbers have been fabricated based on polypyrrole (PP)/natural rubber (NR) nanocomposites and their reflection loss characteristics were studied in the range of 8–18 GHz. The PP‐NR matrix was prepared from PP and NR in the ratio of 15:85. The polymers used in this work not only serve as the matrix but also improve the microwave absorption properties. The first layer or impedance matching layer which is comprised of graphite, Fe₃O₄, and TiO₂ nanoparticles in PP‐NR transmits the electromagnetic (EM) wave without reflection. The second layer which is made up of PP‐NR filled with Fe₃O₄ disperses the EM wave energy. The design of a double‐layer nanocomposite is a method to match the wave impedance, enhance wave absorption ability, and broaden the absorption frequencies. In order to achieve high absorption properties, the EM parameters such as permittivity, permeability, and thickness were controlled precisely according to quarter‐wave plate. The morphology, absorption properties, scattering parameters, thermal and wetting characteristics of double‐layer nanocomposites were investigated. The minimum reflection loss (R_L) was ?32 dB at 12.1 GHz and the absorbing bandwidth in which the R_L < ?10 dB was 9 GHz for optimum specimen with 2 mm thickness. For this specimen, the contact angle was equal to 118.7° with water as the liquid. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46565.     

Compatibilization of polyhedral oligomeric silsesquioxane for polypropylene–titanium dioxide composites and effect of the processing temperature

Polyhedral oligomeric silsesquioxanes (POSSs), with inorganic cores, offer excellent mechanical properties and have external organic substituents. On the basis of their hybrid organic?inorganic characteristics, which allow for a tunable reaction or miscibility with various materials, in this study, we introduced a bifunctional POSS as a novel rigid compatibilizer for polypropylene (PP)–titanium dioxide (TiO₂) composites and evaluated its compatibilizing effects at different processing temperatures. The results show that the attached hydroxyl and isobutyl groups allowed for the reaction with TiO₂ and miscibility with the PP matrix. However, at lower processing temperatures, POSS existed in the form of solid particles, and its interfacial absorption was too poor for sufficient coverage of the TiO₂ surface; this resulted in a weak compatibilization effect on the PP–TiO₂ composite. When the processing temperature was increased to 240 °C, the solid POSS turned into a liquid and thus had strong mobility; this was favorable for the diffusion of TiO₂ onto the surface and the construction of a strong interfacial phase. Because the rigid characteristic of POSS made a positive contribution to the performances of the composites, the PP–TiO₂ composites prepared at higher processing temperatures exhibited better mechanical properties, with the maximum increases occurring in the compositions containing 5 wt % POSS. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44766