Film formation of nano‐sized hard latex (PS) in soft polymer matrix (PBA): An excimer study

This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)‐labeled nano‐sized polystyrene (PS) and poly(n‐butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (T_g) of polystyerene. Monomer (I_P) and excimer (I_E) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both I_E/I_P and I_tr curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (I_E/I_P) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50–100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:1611–1619, 2010. © 2009 Society of Plastics Engineers     

UV‐curable coatings with nano‐TiO2

Nano‐TiO₂ particles were first milled into butyl acetate or trimethylolpropane triacrylate (TMPTA) to obtain TSB and TST slurries, then embedded into epoxy acrylate to obtain UV‐curable coating. The influence of nano‐TiO₂ particles on the photopolymerization kinetics, tack free time, thermal and optical properties of UV‐curable coatings was investigated. It was found that TST‐based coating had a decreasing but TSB‐based coating had an increasing UV cured rate in comparison with the pristine epoxy acrylate. Nevertheless, the TST‐based coating occupied shorter tack free time, good thermal property and UV absorbance than their corresponding TSB‐based coating. POLYM. ENG. SCI. 46:1402–1410, 2006. © 2006 Society of Plastics Engineers.     

Nano‐sized TiO2‐reinforced natural rubber composites prepared by latex compounding method

This paper addresses nano‐sized titanium dioxide (TiO₂) reinforced natural rubber composites. Micro‐sized TiO₂ is simultaneously prepared to make a comparison with the composites containing nano‐sized TiO₂. To improve the dispersion of TiO₂, this study also suggests a new method of incorporating TiO₂. Aqueous dispersions of micro‐ and nano‐sized TiO₂ at the loadings of 0, 2, 4, 6, and 8 parts by weight per hundred parts of resin were dispersed in natural rubber latex, and then the resulting compounds were dried prior to mixing it with other ingredients on a two‐roll mill. By applying this technique, the homogeneity of the compound is significantly improved. This can be clearly seen from the enhancement of tensile properties and morphological characteristics where the optimum loading was found at 6 parts by weight per hundred parts of resin of micro‐ and nano‐sized TiO₂. Adding TiO₂ results in delayed scorch times and curing times wherein the curing process of filled compounds is shorter than the unfilled compound. J. VINYL ADDIT. TECHNOL., 23:200–209, 2017. © 2015 Society of Plastics Engineers     

Film formation from latex dispersions

The dominant, capillary forces operative in film formation of latex dispersions, and how theoretical models have dealt with them over the years are addressed. The force by the receding water surface is the dominant driving force. Capillary liquid bridge forces are less effective. Environmental relative humidity (RH) virtually does not influence these forces. With a light transmission technique, the effect of temperature and humidity on the film formation of a surfactant-free butyl acrylate latex was studied. Film formation is successful at temperatures higher than a value slightly below T_g. RH only slightly promotes film formation, presumably because water acts as a solvent. Also, the film promoting action of normal cosolvents as a function of concentration was clearly demonstrated. Presented at the 26th International Waterborne, High-Solids, and Powder Coatings Symposium, on February 10–12, 1999, New Orleans, LA and at the Forum de la Connaissance, on November 26–27, 1998, Paris, France. Dept. of Polymer Chemistry and Coatings Technology, Post Box 513, NL-5600 MB, Eindhoven, The Netherlands.     

Study of film formation from PS latex/TiO2 nanocomposites; Effect of latex size and TiO2 content

In this work, we investigated the film formation from polystyrene (PS) latex/TiO₂ nanocomposites using the steady state fluorescence (SSF) and UV–vis (UVV) techniques depending on PS particle size and TiO₂ content. The structural properties of films were characterized by scanning electron microscope (SEM). The films were prepared from pyrene (P)‐labeled PS particles (SmPS:203 nm; LgPS:382 nm) by covering them with different layers of TiO₂ by dip‐coating method and then annealed at elevated temperatures. Two film series (SmPS/TiO₂ and LgPS/TiO₂) were prepared and seven different films were studied in various TiO₂ contents for each series. Scattered (I_sc), fluorescence (I_P), and transmitted (I_tr) light intensities were measured after each annealing step to monitor the stages of film formation. Results showed that, SmPS/TiO₂ films undergo complete film formation independent of TiO₂ content. However, no film formation occurs above a certain TiO₂ content in LgPS/TiO₂ films. SEM images showed that SmPS/TiO₂ films have highly well‐ordered microporous structures with increasing TiO₂ content after extraction of PS polymer whereas LgPS/TiO2 composites show no porous structure for high TiO₂ content. Our experiments also showed that porous TiO₂ films with different sizes could be successfully prepared using this technique. POLYM. COMPOS., 35:2376–2389, 2014. © 2014 Society of Plastics Engineers     

Vibration welding of nano‐TiO2 filled polypropylene

Polypropylene (PP)‐based nanocomposites compounded by a twin‐screw extruder and injection molded into plates those were then joined by linear vibration welding. The mechanical performances of the welds and bulk materials were examined. While the incorporation of rigid particles slightly improves the impact strength of the bulk PP, the mechanical properties of the welds decrease with increasing nanoparticle contents. The best weld quality is obtained at low weld pressure without nanoparticles. The fracture surfaces and microstructure of the welds showed that the reduced weld quality is caused by the orientation of nanofillers parallel to the weld plane, the destruction of interphase between fillers and matrix, and the reduction of molten‐film thickness by incorporation of nanoparticles. POLYM. ENG. SCI., 55:243–250, 2015. © 2014 Society of Plastics Engineers     

Reproduction of Jun‐red glazes with nano‐sized copper oxide

Nano sized copper oxide was firstly employed for producing Jun‐red glazes. A series of Jun‐red glazes were prepared by adjusting the copper oxide nanoparticle content and the valance state of elemental copper in the glaze matrix. The coloring and microstructure of each glaze was investigated by spectrophotometer, X‐ray diffraction, scanning electron microscope, X‐ray photoelectron spectrometer, and transmission electron microscope. Under reducing conditions, the red glaze color gradually darkens with increasing CuO content from 0.5 to 1.0 wt%. Interestingly, the coloring of the samples fired under reducing atmosphere turned to be green‐blue, when the content of nanosized CuO was increased to 1.5 wt%. We also found that increased CuO content increases the size of phase separation in the glazes. As comparison, the coloring of samples fired without nanosized CuO are slightly blue under reducing atmosphere, which is attributed to the structural color generated owing to the Rayleigh scattering. Red color of the Jun glazes may arise from elemental copper nanoparticles. The current research utilizing modern nanotechnology provides a new insight into both the “furnace transmutation” and “color regulating” of the ancient Jun‐red glazes.     

Effect of nano‐TiO2 on MP‐25 resin

MP‐25 resin is a chlorine‐containing polymer widely used in coatings. The effects of two types of nano‐TiO₂ (P‐25 and RM301 LP) on MP‐25 were studied with saline immersion, UV irradiation, and electrochemical impedance spectroscopy. UV irradiation was evaluated in terms of gloss change and X‐ray photoelectron spectroscopy (XPS). The results indicate that, compared to pigment R‐930 TiO₂, P‐25 reduced the immersion resistance and accelerated UV aging of the MP‐25 coating, whereas RM301 LP showed the opposite effects. XPS analysis showed that MP‐25 resin degraded under UV irradiation via dechlorination and C? C bond breakage, similarly to poly(vinyl chloride), but RM301 LP could inhibit the aging of MP‐25 to a certain extent. A skin effect of oxygen and chlorine was identified in MP‐25 resin by XPS. RM301 LP could improve the impedance of the MP‐25 coating because of its excellent fill capacity. Hence, rutile nano‐TiO₂ RM301 LP represents an excellent additive for MP‐25 resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation and characterization of bipolar membranes modified using photocatalyst nano‐TiO2 and nano‐ZnO

The nano‐ZnO and nano‐TiO₂ were added into chitosan (CS) anion layer to prepare polyvinyl alcohol (PVA) ‐ sodium alginate (SA)/ TiO₂‐ZnO‐CS (here, PVA:polyvinyl alcohol; SA:sodium alginate) bipolar membrane (BPM), which was characterized using scanning electron microscopy, atomic force microscopy (AFM), thermogravimetric analysis (TG), electric universal testing machine, contact angle measurer, and so on. Experimental results showed that nano‐TiO₂‐ZnO exhibited better photocatalytic property for water splitting at the interlayer of BPM than nano‐TiO₂ or nano‐ZnO. The membrane impedance and voltage drop (IR drop) of the BPM were obviously decreased under the irradiation of high‐pressure mercury lamps. At a current density of 60 mA/cm², the cell voltage of PVA‐SA/TiO₂‐ZnO‐CS BPM‐equipped cell decreased by 1.0 V. And the cell voltages of PVA‐SA/TiO₂‐CS BPM‐equipped cell and PVA‐SA/ZnO‐CS BPM‐equipped cell were only reduced by 0.7 and 0.6 V, respectively. Furthermore, the hydrophilicity, thermal stability, and mechanical properties of the modified BPM were increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of aging on latex film formation from polystrene particles: A photon transmission study

Aging due to the storage time on latex film formation was studied using the photon transmission method. The UV visible technique was used to monitor the evolution of transparency during film formation from two different polystyrene (PS) particles produced by using two different steric stabilizers, i.e., polyvinyl alcohol and polyvinyl pyrrolidone. The latex films were prepared from PS particles at room temperature before and after aging and annealed at elevated temperatures in various time intervals above glass transition (T_g). The increase in the transmitted photon intensity I_tr was attributed to the increase in the number of disappeared particle–particle interfaces. Relative decrease in transparency and delay in film formation were observed in the aged latex films compared to the nonaged ones. The Prager–Tirrell model was employed to interpret the increase in crossing density at the junction surface. The back and forth activation energies (ΔE) were measured and found to be dependent on aging for a diffusing polymer chain across the junction surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2014–2021, 2001     

Preparation and characterization of acrylic latex/nano‐SiO2 composites

Acrylic/nano‐silica composite latexes were prepared by blending via high shear stirring (SS) or ball milling (BM) and in situ polymerization (IS). For comparison, composites filled with micro‐silica were also prepared. The mechanical and optical properties of the polymers formed by the composite latex filled with nano‐ or micro‐silica were investigated using an Instron testing machine, by dynamic mechanical analysis, ultraviolet–visible spectrophotometry and transmission electron micrography. The results showed that SS and BM methods could obtain better nanocomposite latex and polymers than the IS method, characterized by better dispersion of nanoparticles, higher tensile strength and T_g for SS and BM than for IS. The increase in absorbance and reduction in transmittance of UV (290–400 nm wavelength) were observed as nano‐silica content increased, whereas the UV absorbance or transmittance basically were kept unchanged for the composites filled with micro‐silica. © 2002 Society of Chemical Industry     

Asymmetric polyurethane membrane with in situ‐generated nano‐TiO2 as wound dressing

For potential application as an ideal wound dressing, a novel asymmetric polyurethane membrane with in situ‐generated nano‐TiO₂ (PUNT) was successfully prepared via a combination of solvent evaporation, wet phase inversion, and organic–inorganic hybridization. According to this combination method, the PUNT membrane consisted of an integral and dense skin layer supported by a porous sublayer, with nano‐TiO₂ particles dispersed evenly throughout the sample. The skin layer was found to be impermeable to bacteria penetration, and the porous sublayer was designed for absorbing high amounts of exudates. Nitrogen adsorption/desorption experiment proved that extra mesopores were created in the PUNT membrane after organic–inorganic hybridization, which resulted in promoted gas permeability, water vapor transmission rate, and exudate absorption capability. The PUNT membrane, as a consequence, could accelerate gas exchange and also provide an optimal level of moisture over the wound beds without risking dehydration or exudate accumulation. Shake flask testing and cell culture (L929) assay indicated that the PUNT membrane exhibited antibacterial activity against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, whereas showed no cytotoxicity. From in vivo animal studies, the curative effect of PUNT membrane was found to be better than gauze and a commercial polyurethane membrane dressing. These results indicated that the PUNT membrane with multifunctions prepared in this study has potential for application as an ideal wound dressing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Surface modification of nano‐sized silicon nitride with BA‐MAA‐AN tercopolymer

In this work, a macromolecular coupling agent (BA‐MAA‐AN tercopolymer) was used for surface modification of native nano‐sized silicon nitride (Si₃N₄) powder. This modification strategy was designed for preparing nano‐Si₃N₄/NBR composites. The structure and surface properties of modified nano‐Si₃N₄ were systematically investigated by FTIR, XPS, TGA, TEM, Size Distributions Analyzer, and Contact Angle Measurement. It was found that, the optimum loading of BA‐MAA‐AN tercopolymer coated on the surface of nano‐sized Si₃N₄ is 10% of nano‐Si₃N₄. According to the spectra of FTIR, XPS and TGA, it can be inferred that this macromolecular coupling agent covalently bonds on the surface of nano‐sized Si₃N₄ particles and an organic coating layer is formed. The contact angle experiments show that the hydrophobic property of nano‐sized Si₃N₄ modified with macromolecular coupling agent is improved obviously. TEM reveals that modified nano‐Si₃N₄ possesses good dispersibility and the average diameter in NBR is less than 100 nm. It has also been found that the oil resistance of NBR based nanocomposites is improved greatly due to the modified nano‐Si₃N₄. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Spectroscopic study of film formation from polystyrene latex/TiO2 nanocomposites prepared by dip‐coating method

In this study, we investigated the influence of TiO₂ content and thickness of polystyrene (PS) template on film‐formation behavior of PS/TiO₂ composites using fluorescence and ultraviolet–visible techniques in conjunction with scanning electron microscopy. Films were prepared by coating PS templates with various layers of TiO₂ using dip‐coating method. The results showed that PS latexes present complete film formation on top surface of composites. After extraction of PS, a well‐defined interconnected porosity were obtained for thin films when TiO₂ content was increased, whereas thick samples did not present any interconnected porous structures above a certain TiO₂ layer. POLYM. ENG. SCI., 54:288–302, 2014. © 2013 Society of Plastics Engineers     

Film formation from polystyrene–poly(butyl acrylate‐co‐methyl methacrylate) latex blends

We have employed steady sate fluorescence (SSF) and UV‐visible (UVV) techniques to determine the film formation behavior of latex blends. Blend films were prepared from mixtures of a high‐T_g pyrene (P) labeled polystyrene (PS) latex and a low‐T_g copolymer of poly(butyl acrylate‐co‐methyl methacrylate) (BuA/MMA4). Eleven different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass‐transition (T_g) temperature of polystyerene for 10 min. Fluorescence intensity (I_P) from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). A significant change occurs in both I_P and I_tr intensities at a certain critical weight fraction of hard latex (R_c = 0.3). Above R_c, two distinct film formation stages, which are named as void closure and interdiffusion processes, were seen in fluorescence data. Transparency of the films was decreased with decreasing PS content, indicating that a phase separation process occurs between PS and BuA/MMA4 phases by thermal treatment, which results in turbid films. However, below R_c, no change was observed in I_P and I_tr upon annealing, whereas transparency increased overall with increasing BuA/MMA4 ratio. We explained this result as the phase separation process between PS and BuA/MMA4 blends. These results were also confirmed by AFM pictures. Film formation stages above R_c were modeled and related activation energies were calculated. POLYM. COMPOS., 27:431–442, 2006. © 2006 Society of Plastics Engineers     

High‐temperature mechanical behavior of ZrB2‐based composites with micrometer‐ and nano‐sized SiC particles

Using micrometer‐ and nano‐sized SiC particles as reinforcement phase, two ZrB₂‐SiC composites with high strength up to 1600°C were prepared using high‐energy ball milling, followed by hot pressing. The composite microstructure comprised finer equiaxed ZrB₂ and SiC grains and intergranular amorphous phase. The temperature dependency of flexure strength related to the initial particle size of SiC. In the case of micrometer‐sized SiC, the high‐temperature strength was improved up to 1500°C compared to room‐temperature strength, but the strength degraded at 1600°C, with strength values of 600‐770 MPa. In the case of nano‐sized SiC, the enhanced high‐temperature strength was observed up to 1600°C, with strength values of 680‐840 MPa.     

Property improvement of plasticized poly(vinyl chloride) by nano‐TiO2 and poly(methyl methacrylate)–encapsulated nano‐TiO2

To improve the physical properties of plasticized poly(vinyl chloride) (p‐PVC), the p‐PVC nanocomposites filled with four loading levels (3, 5, 7, and 9 parts per hundred of PVC resin) of either nanosized titanium dioxide (nTiO₂) or poly(methyl methacrylate)–encapsulated nTiO₂ (PMMA‐nTiO₂) were prepared by melt mixing on a two‐roll mill, followed by compression molding. The PMMA‐nTiO₂ used in this study was synthesized via in situ differential microemulsion polymerization. The resulting PMMA‐nTiO₂ exhibited core‐shell morphology (nTiO₂ core and PMMA shell) with an average diameter of 42.6 nm. The effects of nTiO₂ and PMMA‐nTiO₂ on the tensile properties, hardness, morphology, and thermal stability of the as‐prepared p‐PVC nanocomposites were then investigated and compared. The inclusion of either nTiO₂ or PMMA‐nTiO₂ nanoparticles increased the tensile strength, Young's modulus, hardness, and thermal stability of the nanocomposites in a dose‐dependent manner and reduced the elongation at break. However, the elongation at break was still higher than that for the neat p‐PVC. Moreover, the PMMA‐nTiO₂ nanocomposites had a higher enhancement of the tensile strength, Young's modulus, hardness, and thermal stability than the nTiO₂ nanocomposites at a similar loading level. Hence, the PMMA grafted on the nTiO₂ surface played an important role in toughening and increasing the thermal stability of the nanocomposites owing to the improved miscibility and interfacial adhesion between the encapsulated nanofiller and PVC matrix. J. VINYL ADDIT. TECHNOL., 22:433–440, 2016. © 2015 Society of Plastics Engineers     

Solid‐state synthesis and characterization of polyaniline/nano‐TiO2 composite

Polyaniline/nano‐TiO₂ composites with the content of nano‐TiO₂ varying from 6.2 wt % to 24.1 wt % were prepared by using solid‐state synthesis method at room temperature. The structure and morphology of the composites were characterized by the Fourier transform infrared (FTIR) spectra, ultraviolet‐visible (UV–vis) absorption spectra, X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The electrochemical performances of the composites were investigated by galvanostatic charge–discharge measurement, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The results from FTIR and UV–vis spectra showed that the composites displayed higher oxidation and doping degree than pure PANI. The XRD and morphological studies revealed that the inclusion of nano‐TiO₂ particles hampered the crystallization of PANI chains in composites, and the composites exhibited mixed particles from free PANI particles and the nano‐TiO₂ entrapped PANI particles. The galvanostatic charge–discharge measurements indicated that the PANI/nano‐TiO₂ composites had higher specific capacitances than PANI. The composite with 6.2 wt % TiO₂ had the highest specific capacitance among the composites. The further electrochemical tests on the composite electrode with 6.2 wt % TiO₂ showed that the composite displayed an ideal capacitive behavior and good rate ability. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of nano‐TiO2 surface modification on polarization characteristics and corona aging performance of polyimide nano‐composites

Using coupling agent isocyanatopropyltriethoxysilane (ICTOS) to modified nano‐TiO_2, the polyimide (PI) with different titanium dioxide (TiO₂) contents (0, 1, 2, 3, 4, and 5 wt %) doped nano‐composites were prepared by sol–gel method (PI/TiO_{2 ICTOS} composites). The effect of ICTOS modification on polarization and time‐to‐breakdown properties of composites were investigated by thermally stimulated depolarization current (TSDC) method, dielectric, and Corona aging measurements. The TSDC spectra show that ICTOS modification enhanced α‐peak intensity and make β‐peak disappear in composites. Relevant trap parameters were calculated by an approximate model, and the results indicate that introduction of ICTOS is effective for the charge carrier traps, activation energy distribution in composites. Corona aging measurement show corona resistance was also sufficient improved in PI/TiO_{2 ICTOS} composites. The changes of activation energy and intensity of traps in composites may be responsible for the corona resistance. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45101.