In this study, silica-based sol–gel systems were prepared through hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) and (3-Glycidyloxypropyl) trimethoxysilane (GLYMO). The sol–gel systems, combined with a nonionic surfactant, silica dioxide (SiO2) and a waterborne polyurethane (WPU) emulsion, could form RoHS compliant corrosion protection coatings for 55% Al-Zn alloy-coated steel and were developed as alternatives to conventional chromate-based coatings. Gel content, indentation hardness, and salt spray resistance of the polyurethane (PU) coating were greatly enhanced by the addition of the sol–gel systems and the additives. Impact of TEOS to GLYMO ratio, morphology, elemental composition of the coated surface, nanomechanical properties and corrosion resistance of the sol–gel enhanced PU coating were examined. The results indicated that the coatings which combined the advantages of the sol–gel matrix and the PU emulsion outperformed a commercial chromate conversion coating and a commercial chromium-free coating, and could be considered as alternatives for eco-friendly applications.

In this study, a highly conductive poly(3,4-ethylenedioxythiophene)–poly(styrenesulfonic acid) (PEDOT:PSS) dispersion served as a stabilizer for producing conductive PEDOT:PSS–poly(styrene-co-butyl acrylate) (PEDOT:PSS–P(St–BA)) composite latexes by emulsion polymerization. Furthermore, soft latex particles of poly(styrene-co-butyl acrylate), P(St–BA), were synthesized via emulsion polymerization and then mixed with the conductive PEDOT:PSS–P(St–BA), followed by casting on the substrate. After drying, conductive composite films with flexibility and transparency could be obtained. The particle size and morphology of PEDOT:PSS–P(St–BA) were observed by a scanning electron microscope. The film surface resistance, thickness, conductivity and transmittance of the composite films were measured and studied. Bending tests were also conducted to detect the flexibility. According to the results, the composite films showed high transmittance while possessing good conductivity and superior flexibility. The method may serve as a practical approach to fabricate conductive, flexible and transparent films.

Thermally crosslinkable copolymers of N-isopropylacrylamide (NIPAAm) and N-Methylol acrylamide (NMA), a thermal crosslinker, were prepared by redox polymerization. The aqueous solutions of the copolymer were temperature responsive, and they showed phase separation behavior. The corresponding phase transition temperatures were detected by UV–visible spectroscopy and differential scanning calorimetry (DSC). The cloud points increased with increasing content of NMA from 32°C of pure polyNIPAAm to 48°C for poly(NIPAAm-co-NMA) with 30mol% NMA. The crosslinking capability of the resulting polymers with different NMA contents was evaluated by monitoring their gel fractions and swelling ratios after crosslinking. The equilibrium swelling behaviors of the poly(NIPAAm-co-NMA) hydrogels were also investigated as a function of curing time. The results showed the hydrogels cured at shorter times or lower temperatures had lower gel fractions and higher swelling ratios. The introduction of a crosslinking structure into the temperature-responsive polyNIPAAm controlled the swelling capability and the cloud point of the crosslinked hydrogels.

Melt mixed metallocene-catalyzed polyethylene elastomer (mPE)/clay nanocomposites, using a functionalized polyolefin elastomer (mPE-g-silane) as a compatibilizer, with the addition of the commercial clay with different intercalant types (Cloisite 20A and 30B) were prepared to investigate the importance of interfacial interaction. Cloisite 30B gave a relatively higher polarity than Cloisite 20A, but smaller original d-spacing. According to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, Cloisite 20A-filled nanocomposites depicted fairly well-dispersed clay within the mPE matrix, except with higher clay content. By contrast, the clay agglomerates were evident for Cloisite 30B-filled cases. A continuous increase of gel content for Cloisite 20A-filled systems was observed, but only a limited variation for Cloisite 30B-filled systems was found. The roles of the polarity degree of the organically modified clay, original d-spacing, and the compatibilizer, were quite essential. Young's modulus of Cloisite 20A-filled samples increased with increasing clay content, from 23.8 +/- 1.3 MPa [0 parts per hundred resins (phr)] to 34.1 +/- 2.0 MPa (9 phr), whereas modulus of Cloisite 30B-filled samples did not show a significant variation. The tear strength of Cloisite 20A-filled nanocomposites increased up to two-fold with increasing clay content, reaching 9 phr. Only a slight increase in tear strength of Cloisite 30B-filled nanocomposites was observed. For the cutting strength, Cloisite 20A-filled cases also conferred higher values in comparison with Cloisite 30B-filled cases.

Innovative temperature-dependent conductive composite materials, poly(N-isopropylacrylamide-co-N-methylol acrylamide)/acid-treated carbon black, poly(NIPAAm-co-NMA)/CB, were prepared. The copolymer of NIPAAm and NMA was synthesized via a random redox copolymerization, and the poly(NIPAAm-co-NMA) copolymer showed thermo-responsive properties. Here, NMA performed a thermal crosslinking function in the copolymer. Carbon black was acid-treated for good dispersion in an aqueous solution. Poly(NIPAAm-co-NMA)/CB composites were obtained by blending various amounts of acid-treated CB into the poly(NIPAAm-co-NMA) aqueous solution, and the films were then post-cured for thermal crosslinking. The properties of the conductive poly(NIPAAm-co-NMA)/CB films such as thermal crosslinking performance, surface resistance, and morphology of the crosslinked composites were investigated. This study demonstrated that the poly(NIPAAm-co-NMA)/CB composites exhibited both temperature-dependent electric resistance and reproducible thermally responsive characteristics. The composites can potentially be applied as new electrical temperature sensor materials.

Innovative elastic and flexible conductive composite materials PEDOT:PSS/P(BA-St) and PEDOT:PSS-PBA were prepared by two approaches based on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). In the first part, PEDOT:PSS/P(BA-St) was prepared by blending various soft poly(n-butyl acrylate-styrene) (P(BA-St)) latexes into a PEDOT:PSS conductive dispersion. The PEDOT:PSS conductive dispersion was prepared via oxidative polymerization of EDOT, and the soft P(BA-St) latexes were synthesized by emulsion polymerization using various types of surfactants. In the second part, poly(styrenesulfonate) (PSS) served as a surfactant to synthesize poly(styrenesulfonate)-poly(butyl acrylate) (PSS-PBA) soft latex via emulsion polymerization. Then, the PEDOT:PSS-PBA dispersion was prepared by using the PSS-PBA soft latex as a polymeric template to polymerize EDOT. The glass transition temperature (T-g) and particle size of P(BA-St) and PSS-PBA were measured. The optoelectronic properties of the conductive PEDOT:PSS/P(BA-St) and PEDOT:PSS-PBA films such as transmittance, surface resistance, and UV-vis absorbance were investigated. According to the elongation measurement, the fabricated PEDOT:PSS/P(BA-St) elastic film containing a P(BA-St) content as high as 83 wt% showed a high value of 97% elongation, while possessing good film conductivity (63 S cm(-1)) and superior transmittance (93%). On the other hand, the fabricated PEDOT: PSS-PBA flexible film containing 13 wt% PBA showed a low surface resistance increment (R/R-0 < 1.2) after two steps of bending test, while maintaining superior conductivity (300 S cm(-1)) and high light transmittance (>80%).

The Maxwell–Wagner–Sillars relaxation behavior of poly(butylene succinate) during melting and recrystallization at 383K was studied. It was found that the polarization originates from the three-phase structure of the dispersion of spherulites in the crystallizing melt. A model made up of a conductive melt matrix and a dispersion of spherical semicrystalline particles was proposed. The semicrystalline particles were composed of continuous, nonconductive crystals and spherical amorphous inclusions with the conductivity of the melt matrix. The three-phase Bruggeman–Hanai theoretical equations for interfacial polarization were employed and the relaxation behavior were successfully simulated. Three parameters – the melt conductivity, the volume fraction of the semicrystalline particles, and the amorphous fraction within these particles are obtained by fitting the theoretical equations to the experimental data. Their relationships with the morphological development during the recrystallization process were correspondingly discussed.

Dielectric properties of poly(butylene succinate) crystallized under different conditions have been reported in the temperature range of 163–383K and in the frequency range of 0.01–105Hz. Both the dipolar α and β processes have been identified at low temperatures: the α process is associated with the amorphous fraction while the β with the relaxations in both the amorphous and crystalline fractions. The space charge effect dominates the high temperature dielectric spectra. These spectra have been analyzed in the light of an equivalent circuit model. The Maxwell–Wagner–Sillars polarization, electrode polarization and free charge motion are well resolved. At 383K, near the melting temperature (387K), massive melting and subsequent recrystallization have been observed. The peculiar evolution of the spectra is also analyzed using the same equivalent circuit model. The relationship between the fitting parameters and the evolved microstructures is discussed.

The effects of crosslink density and blowing pressure on the cell size of m-POE (metallocene polyolefin elastomer) foams are presented. The crosslink density and the blowing pressure were controlled by varying the loadings of the crosslinking agent and the chemical blowing agent, respectively, in the m-POE foam compounds. The cell size distributions were obtained by optical microscopic observations along with an image analysis software. After comparing the foam piece density before and after high-temperature heating, it was deduced that the foaming of m-POE is a highly elastic process. The equation for the inflation of an elastic spherical cavity was thus adopted in relating the cell size to the blowing pressure and the crosslink density. The average cell size can be roughly scaled by a single parameter: the ratio of blowing pressure to crosslink density.

A combination of Monte Carlo simulation and gel content experiments was used to study the molecular structural evolution of two randomly crosslinked systems: ethylene vinyl acetate copolymer and metallocene polyolefin elastomer in the presence of a triallyl cyanurate polyfunctional monomer (PFM). The molecular weight distributions, crosslinking density and PFM density evolutions are simulated. There exist gaps in the crosslinking density and the bonded PFM density, between the gel and the sol fractions. The density gaps widen as the crosslinking reaction proceeds. Towards the end of the reaction, the gel crosslinking density increases at a rate higher than that for the gel PFM density. The crosslinking level for the PFM molecules in the gel fraction is much higher than that in the sol fraction. The evolved structures for the two polymer systems during the reaction are also discussed.

The reaction kinetics with a diffusion control mechanism, as well as the volumetric change upon curing, of a cresol novolac epoxy/ o -cresol-formaldehyde novolac hardener system were studied. Simple equations to model the change in linear coefficients of thermal expansion with reacting thermosetting system conversion were also derived. Based on the heat of the reaction of monomeric monofunctional model compounds, the true degree of conversion of this crosslinking epoxy system can be obtained. The reaction is then modeled as a reaction of shifting order: it first reacts autocatalytically and later switches into diffusion control. The reaction in the diffusion-controlled region can be modeled by an n-th order kinetic equation with its rate constant described by a WLF-type equation. Both experimental linear coefficients of thermal expansion above and below the glass transition temperature decrease linearly with the degree of conversion, which agrees with the derived equations. The importance of chemical shrinkage upon curing is also discussed.

The effect of the use of an unsaturated reactive plasticizer trimethylopropane trimethacrylate, TMPTMA, on the structure and the creep behavior of poly(vinyl chloride), WC, plastisols has been investigated as part of a program to develop a high-temperature creep-resistant Liner material. The crosslinking reaction was initiated with a peroxide. The effect on the network structure of using a free radical scavenger in the formulation has also been studied. Gel yield and grafted WC content in the gel increase with increased TMPTMA content in the plastisol. However, the residual unsaturation of TMPTMA decreases with increase of TMPTMA content. Introduction of TMPTMA into the plastisol promotes the creep resistance at high temperatures, and the effectiveness increases when there are WC molecules grafted onto TMPTMA networks.

The reaction kinetics of crosslinked low density polyethylene (LDPE) foam systems has been investigated. Dicumyl peroxide (DCP) was used as the crosslinker. The crosslinking reaction of LDPE/DCP system is controlled by a first order decomposition of DCP. The reaction kinetics of a chemical blowing agent, azodicarbon amide (ADCA), and its kicker, zinc oxide (ZnO), was also investigated. The rate of reaction of ADCA is very fast, and a general nth-order reaction kinetics fails to predict its conversion. A model combining a general nth-order reaction kinetics and autocatalytic reaction kinetics was adopted instead. The addition of ZnO into ADCA not only lowered the decomposition temperature, but also accelerated its decomposition. The reaction kinetics of the LDPE/ADCA/ZnO system was also studied, and was found to be similar to those of ADCA/ZnO system. The numerical results in this study serve as a framework for future prediction and simulation of molecular structure changes of a reactive polymeric foam system.

The crystallization kinetics and morphology of glass fiber-reinforced polypropylene (PP/GF) were investigated in this work. Both isothermal and nonisothermal crystallization behaviors of 90PP/10GF, 80PP/20GF, and 70PP/30GF were examined with a DSC instrument. It was found that the addition of glass fiber would increase the crystallization rate of PP and increase the content of beta spherulite, which was most likely formed at temperatures between 390 and 400 K. The morphology of spherulites of PP/GF composites were examined with SEM and a polarized microscope. All experimental observations conformed rather well with the theoretical approach, a dynamic crystallization model, proposed in our previous work. The size of alpha spherulites of PP would decrease at lower crystallization temperature, or at higher cooling rate, or by adding glass fiber in it.