A multi-fluid nonrandom lattice fluid model: General derivation and application to pure fluids

A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems is presented. The multi-fluid nonrandom lattice fluid (MF-NLF) model with the local composition concept was capable of describing properties for complex systems. However, the MF-NLF model has strong temperature dependence of energy parameters and segment numbers of pure systems; thus empirical correlations as functions of temperature were represented for reliable and convenient use in engineering practices. The MF-NLF model without temperature dependence of pure parameters could not predict thermodynamic properties accurately. It was found that the present model with three parameters describes quantitatively the vapor pressure and the saturated density for the pure fluid.     

Synthesis and characterization of in situ polymerized segmented thermoplastic elastomeric polyurethane/layered silicate clay nanocomposites

Nanocomposites based on thermoplastic elastomeric polyurethane (TPU) and layered silicate clay were prepared by in situ synthesis. The properties of nanocomposites of TPU with unmodified clay were compared with that of organically modified clay. The nanocomposites of the TPU and organomodified clay showed better dispersion and exhibited superior properties. Exfoliation of the clay layers was observed at low organoclay contents, whereas an intercalated morphology was observed at higher clay contents. As one of major purposes of this study, the effect of the silicate layers in the nanocomposites on the order–disorder transition temperature (T_ODT) of the TPU was evaluated from the intensity change of the hydrogen‐bonded and free carbonyl stretching peaks and from the peak position change of the N? H bending peak. The presence of the organoclay increased T_ODT by approximately 10°C, which indicated improved stability in the phase‐separated domain structure. The layered silicate clay caused a tremendous improvement in the stiffness of the TPU; meanwhile, a reduction in the ultimate elongation was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3048–3055, 2006     

Synthesis of syndiotacticity‐rich high molecular weight poly(vinyl alcohol) by suspension polymerization of vinyl pivalate and saponification

Vinyl pivalate (VPi) was suspension‐polymerized to synthesize high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with a high conversion above 95% for a precursor of syndiotacticity‐rich HMW poly(vinyl alcohol) (PVA). Also, the effects of the polymerization conditions on the conversion, molecular weight, and degree of branching (DB) of PVPi and PVA prepared by the saponification of PVPi were investigated. Bulk polymerization was slightly superior to suspension polymerization in increasing the molecular weight of PVA. On the other hand, the latter was absolutely superior to the former in increasing the conversion of the polymer, indicating that the suspension polymerization rate of VPi was faster than that of the bulk one. These effects could be explained by a kinetic order of a 2,2′‐azobis(2,4‐dimethylvaleronitrile) concentration calculated by the initial rate method. Suspension polymerization of VPi at 55°C by controlling various polymerization factors proved to be successful in preparing PVA of HMW [number‐average degree of polymerization (P_n): 8200–10,500], high syndiotactic diad content (58%), and very high yield (ultimate conversion of VPi into PVPi: 94–98%). In the case of the bulk polymerization of VPi at the same conditions, the maximum P_n and conversion of 10,700–11,800 and 32–43% were obtained, respectively. The DB was lower and the P_n was higher with PVA prepared from PVPi polymerized at lower initiator concentrations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 832–839, 2003     

Preparation of water‐soluble syndiotacticity‐rich high molecular weight poly(vinyl alcohol) microfibrillar fibers using copolymerization of vinyl pivalate and vinyl acetate and saponification

Water‐soluble high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (s‐PVA) microfibrillar fibers were prepared by the saponification with various conditions such as amount of alkali solution, saponification temperature, and saponification concentration from copoly(vinyl pivalate (VPi)/vinyl acetate (VAc)) copolymerized using various VPi/VAc feed ratios. To produce s‐PVA microbrillar fibers having various water‐soluble temperatures for many industrial applications, the intrinsic viscosities, syndiotactic diad (S‐diad) contents, and degrees of saponification (DS)s of PVAs were finely controlled to 1.2–3.6 dL/g, 56.3–58.3%, and 91.4–98.3%, respectively. Through a series of experiments, it was found that the amount of alkali may alter the structure of the saponified polymers, primarily the DS, and the structural variation changes viscosity. That is, intrinsic viscosity was sharply decreased as the amount of alkali solution was increased. DS was increased with an increase in the amount of alkali solution. S‐diad content was increased with an increase in the VPi content. HMW s‐PVA microfibrillar fibers having S‐diad content of 56.3–58.3% prepared by the saponification of copoly(VPi/VAc) were completely soluble in water at 100°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1482–1487, 2003     

Synthesis and non‐isothermal crystallization behavior of poly(ethylene phthalate‐co‐terephthalate)s

A series of poly(ethylene phthalate‐co‐terephthalate)s were synthesized by melt polycondensation of ethylene glycol (EG) with dimethyl phthalate (DMP) and dimethyl terephthalate (DMT) in various proportions. The DMT‐rich polymers were obtained with reasonably high molecular weights, whereas the DMP‐rich polymers were synthesized with relatively low molecular weights due to steric effects associated with the highly kinked DMP monomer. The compositions and thermal properties of the polymers were determined. The copolymers containing DMP in amounts of ≤ 21 mol% were crystallizable, whereas the other polymers were not. All the polymers exhibited a single glass transition temperature. Analysis of the measured glass transition temperatures and crystal melting temperatures confirmed that the DMT‐rich copolymers are random copolymers. The non‐isothermal crystallization behaviors of the DMT‐rich copolymers were investigated by calorimetry and modified Avrami analysis. The Avrami exponents n were found to range from 2.7 to 3.8, suggesting that the copolymers crystallize via a heterogeneous nucleation and spherulitic growth mechanism; that is, the incorporation of DMP units as the minor component does not change the growth mechanism of the copolymers. In addition, the activation energies of the crystallizations of the copolymers were determined; the copolymers were found to have higher activation energies than the PET homopolymer. Polym. Eng. Sci. 44:1682–1691, 2004. © 2004 Society of Plastics Engineers.     

Synthesis of polystyrene/poly(butyl acrylate) core–shell latex and its surface morphology

A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The T_g's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003     

Preparation and characterization of maleic anhydride‐g‐polypropylene/diamine‐modified clay nanocomposites

Polypropylene (PP)/montmorillonite (MMT) nanocomposites were prepared by compounding maleic anhydride‐g‐polypropylene (MAPP) with MMT modified with α,ω‐diaminododecane. Structural characterization confirmed the formation of characteristic amide linkages and the intercalation of MAPP between the silicate layers. In particular, X‐ray diffraction patterns of the modified clay and MAPP/MMT composites showed 001 basal spacing enlargement as much as 1.49 nm. Thermogravimetric analysis revealed that the thermal decomposition of the composite took place at a slightly higher temperature than that of MAPP. The heat of fusion of the MAPP phase decreased, indicating that the crystallization of MAPP was suppressed by the clay layers. PP/MAPP/MMT composites showed a 20–35% higher tensile modulus and tensile strength compared to those corresponding to PP/MAPP. However, the elongation at break decreased drastically, even when the content of MMT was as low as 1.25–5 wt %. The relatively short chain length and loop structure of MAPP bound to the clay layers made the penetration of MAPP molecules into the PP homopolymer phase implausible and is thought to be responsible for the decreased elongation at break. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 307–311, 2005     

Durable antimicrobial treatment of cotton fabrics using N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride and polycarboxylic acids

N‐(2‐hydroxy)propyl‐3‐trimethylammonium chitosan chloride (HTCC), a water‐soluble chitosan quaternary ammonium derivative, was used as an antimicrobial agent for cotton fabrics. HTCC has a lower minimum inhibition concentration (MIC) against Staphylococcus aureus, Klebsiella pneumoniae, and Escherichia coli compared to that of chitosan; however, the imparted antimicrobial activity is lost on laundering. Thus crosslinking agents were utilized to obtain a durable antimicrobial treatment by immobilizing HTCC. Several crosslinkers such as dimethyloldihydroxyethylene urea (DMDHEU), butanetetracarboxylic acid (BTCA), and citric acid (CA) were used with HTCC to improve the laundering durability of HTCC treatment by covalent bond formation between the crosslinker, HTCC and cellulose. The polycarboxylic acid treatment was superior to the DMDHEU treatment in terms of prolonged antimicrobial activity of the treated cotton after successive laundering. Also, the cotton treated with HTCC and BTCA showed improved durable press properties without excessive deterioration in mechanical strength or whiteness when compared to the citric acid treatment. With the addition of only 0.1% HTCC to BTCA solutions, the treated fabrics showed durable antimicrobial activity up to 20 laundering cycles. The wrinkle recovery angle and strength retention of the treated fabrics were not adversely affected with the addition of HTCC. Therefore, BTCA can be used with HTCC in one bath to impart durability of antimicrobial activity along with durable press properties to cotton fabric. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1567–1572, 2003     

Oil absorbents based on styrene–butadiene rubber

Four oil absorbents based on styrene–butadiene (SBR)—pure SBR (PS), 4‐tert‐butylstyrene–SBR (PBS), EPDM–SBR network (PES), and 4‐tert‐butylstyrene‐EPDM‐SBR (PBES)—were produced from crosslinking polymerization of uncured styrene–butadiene rubber (SBR), 4‐tert‐butylstyrene (tBS), and ethylene–propylene–diene terpolymer (EPDM). The reaction took place in toluene using benzoyl peroxide (BPO) as an initiator. Uncured SBR was used as both a prepolymer and a crosslink agent in this work, and the crosslinked polymer was identified by IR spectroscopy. The oil absorbency of the crosslinked polymer was evaluated with ASTM method F726‐81. The order of maximum oil absorbency was PBES > PBS > PES > PS. The maximum values of oil absorbency of PBES and PBS were 74.0 and 69.5 g/g, respectively. Gel fractions and swelling kinetic constants, however, had opposite sequences. The swelling kinetic constant of PS evaluated by an experimental equation was 49.97 × 10^?2 h^?1. The gel strength parameter, S, the relaxation exponent, n, and the fractal dimension, d_f, of the crosslinked polymer at the pseudo‐critical gel state were determined from oscillatory shear measurements by a dynamic rheometer. The morphologies and light resistance properties of the crosslinked polymers were observed, respectively, with a scanning electron microscope (SEM) and a color difference meter.     

Sensorless control for hysteresis compensation of AFM scanner by modified Rayleigh model

A novel modified Rayleigh model was developed for compensating hysteresis problem of an atomic force microscope (AFM) scanner. In high driving fields, piezoelectric actuators that integrated a scanner have severe hysteresis, which can cause serious displacement errors. Piezoelectric hysteresis is from various origins including movement of defects, grain boundary effects, and displacement of interfaces. Furthermore, because its characteristic is stochastic, it is almost impossible to predict the piezoelectric hysteresis analytically. Therefore, it was predicted phenomenologically, which means that the relationship between inputs and outputs is formulated. The typical phenomenological approach is the Rayleigh model. However, the model has the discrepancy with experiment result as the fields increase. To overcome the demerit of the Rayleigh model, a modified Rayleigh model was proposed. In the modified Rayleigh model, each coefficient should be defined differently according to the field direction due to the increase of the asymmetry in the high fields. By applying an inverse form of this modified Rayleigh model to an AFM scanner, it is proved that hysteresis can be compensated to a position error of less than 5%. This model has the merits of reducing complicated fitting procedures and saving computation time compared with the Preisach model.