Effect of pH on the properties of barium titanate slurries with an aniomic dispersant

The colloidal stability of barium titanate (BT) aqueous suspensions with poly(acrylamide/4‐carboxylamino‐4‐oxo‐2‐butenate) (PAAM/COB) at pH 7, 9, and 12 has been investigated by means of ζ potential, adsorption, sedimentation, and particle size measurements. The isoelectric point of BT powder is at pH 4.6 and the value of ζ potential decreases as the pH of suspensions increases. The adsorption of PAAM/COB onto BT particles follows the Langmuir adsorption isotherm. The saturated amount of adsorbed polymer decreases with increasing pH. In general, BT particles in basic solutions with PAAM/COB are more stabilized, and less agglomerated than those without any dispersant present. As pH is increased, the resulting ζ potential becomes more negative, although lower polymer concentration is required for monolayer coverage of particle surface. Consequently, the resulting suspensions become more stabilized, and contain powder with smaller particle size. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1082–1088, 2006     

Effects of amphoteric copolymer structure on the properties of barium titanate suspensions

The effect of the molecular structure of an amphoteric copolymer, i.e., poly[acrylamide/(α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl)ammonium ethanate)] (PAD) on the interactions with BaTiO₃ (BT) particles in water and on the stability of BT suspensions was examined by means of adsorption, ζ potential, sedimentation, and viscosity measurements. The results indicate that the adsorption of PAD onto BT particles follows the Langmuir adsorption isotherm. As the added PAD containing greater ionic group fraction, both the saturated amount of adsorbed polymer and the amount of the polymer required to reach the minimal ζ potential decrease. Whatever the ionic group fraction in PAD, BT suspensions become stable and less viscous when saturated amount of the polymer was adsorbed on particle surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Amphibious water‐soluble copolymer. I. Its synthesis and dispersing ability on barium titanate

An amphibious water‐soluble copolymer, polyacrylamide/(α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate (PAAM/DAAE), was synthesized and used as a dispersion agent for BaTiO₃ particles. PAAM/DAAE was prepared from acrylamide and (α‐N,N‐dimethyl‐N‐acryloyloxyethyl) ammonium ethanate under basic conditions through a free‐radical polymerization. The structure of this copolymer was verified with IR and ¹H‐NMR spectra. The dispersing effects of PAAM/DAAE were examined through the measurement of the viscosity and sedimentation of BaTiO₃ suspensions and the green density. The results indicated that this copolymer could uniformly disperse the particles, reduce the viscosity, stabilize the suspensions, and produce high‐density green compacts. In comparison with a commercial dispersant, the ammonium salt of poly(methylacrylic acid), PAAM/DAAE was clearly more effective. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2232–2239, 2004     

Water‐soluble copolymers. V. Synthesis of low molecular weight amphoteric polyacrylamide by foamed copolymerization

Amphoteric polyacrylamide of acrylamide, acryloyloxyethyl trimethylammonium chloride, sodium acrylate, and acrylic acid was synthesized by foamed copolymerization. The effects of monomer concentration and composition, initiator concentration and composition, sodium bicarbonate and stabilizer content on the polymer intrinsic viscosity and monomer conversion were examined. The monomer conversion increased with increasing initiator concentration, sodium bicarbonate and stabilizer content. The polymer intrinsic viscosity decreased with increasing initiator concentration. The structure and low molecular weight of the amphoteric polymer were identified by fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC), respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Amphoteric water‐soluble copolymer for barium titanate slurries. I. Synthesis and dispersing ability

An amphoteric water‐soluble copolymer, polyacrylamide/[α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl] ammonium ethanate (PAM/DAE) was synthesized and used as a dispersion agent for BaTiO₃ particles. PAM/DAE was prepared from acrylamide and [α‐N,N‐dimethyl‐N‐(3‐(β‐carboxylate)acrylamino)propyl] ammonium ethanate in a basic condition through a free‐radical polymerization. The structure of this copolymer was verified by IR and ¹H‐NMR spectra. The dispersing effects of PAM/DAE were examined by measuring the viscosity and sedimentation of BaTiO₃ suspensions, and by analyzing the particle size. The results indicate that this copolymer could uniformly disperse the particles, and the resulting suspensions were less viscous, more stabilized, and contained powder with smaller particle size. The dispersing/stabilizing ability of PAM/DAE is close to, or slightly better than, that of a commercial dispersant, ammonium salt of poly(methacrylic acid). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1443–1450, 2005     

Synthesis and application of an anionic water‐soluble copolymer as a dispersant for barium titanate slurries

An anionic water‐soluble copolymer, poly(acrylamide/4‐carboxylamino‐4‐oxo‐2‐butenate) (PAAM/COB), was synthesized and used as a dispersion agent for BaTiO₃ particles. PAAM/COB was prepared from acrylamide and 4‐carboxylamino‐4‐oxo‐2‐butenate in basic conditions through free‐radical polymerization. The structure of this copolymer was verified by IR and ¹H‐NMR spectra. We examined the dispersion effects of PAAM/COB by measuring the viscosity and sedimentation of BaTiO₃ suspensions and by analyzing the particle sizes. The results indicate that this copolymer was indeed effective in dispersing the particles, for the resulting suspensions were less viscous, more stabilized, and contained powder with smaller particle sizes. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 109–115, 2005     

Effect of molecular weight of an anionic dispersant on the properties of BaTi4O9 slurries

The colloidal stability of BaTi₄O₉ (BT₄) aqueous suspensions with poly(acrylamide‐co‐4‐carboxylamino‐4‐oxo‐2‐butenate) (PAC) of different molecular weights at pH 9 has been investigated by means of zeta potential, adsorption, sedimentation, and particle size measurements. The results indicate that PAC could improve the dispersion of the particles from agglomeration. The resulting suspensions became more stabilized, and contained powder with smaller particle size. Consequently, the compacts with PAC exhibited better properties in terms of density and dielectric constant than those without any polymer present. The performance of PAC increased with decreasing polymer molecular weight. Clearly, PAC1 (M_w = 1.8 × 10⁴) was most effective in dispersing the BT₄ particles, and stabilizing the ceramic suspensions. This is attributed to the highest adsorption of this polymer onto BT₄ powder, and causes strongest electrostatic repulsions among solid particles. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

A water‐soluble acrylate/sulfonate copolymer. I. Its synthesis and dispersing ability on cement

A new water‐soluble methacrylate/2‐acrylamido‐2‐methylpropane sulfonate copolymer (PMAMP) was synthesized and evaluated as a dispersion agent for cement particles. PMAMP was prepared from methacrylic acid and 2‐acrylamido‐2‐methylpropane sulfonic acid (AMP). The structure of the prepared polymer was verified by its NMR and IR spectra. The dispersing properties of PMAMP were evaluated by a minislump test on cement pastes. The test results indicated that this copolymer could disperse the cement particles and improve the minislump of cement pastes. Compared with a commercial superplasticizer (sulfonated naphthalene formaldehyde condensates), PMAMP performed better in enhancing the fluidity of the cement pastes. The polymer with about 40–50% AMP and a weight‐average molecular weight of about 5 × 10⁴ was most effective in dispersing cement particles and promoting the fluidity of cement pastes. Nevertheless, PMAMP with a higher AMP content or a higher molecular weight appeared to cause less slump loss. This was related to the interaction of this admixture with the cement particles and its adsorption behavior onto the cement particles. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2490–2496, 2006     

Water‐soluble sulfonated phenolic resins. III. Effects of degree of sulfonation and molecular weight on concrete workability

The effects of the degree of sulfonation (DS) and molecular weight (MW) of sulfonated phenolic resins (SPF) on the flow properties of cementitious materials were investigated. SPF resin was prepared from phenol, formaldehyde, and sodium bisulfite through a four‐step reaction. It was found that an increase in either DS or MW would enhance the dispersion effects in the system. The results indicate that the fluidity of cement pastes and the workability of concrete increased with higher DS until the resin was fully sulfonated. For resins with sufficient sulfonation, the performance of cementitious materials would increase with increasing MW. Apparently, resins with MW of about 3 × 10⁴ are most effective in promoting concrete properties in terms of workability and compressive strength. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1762–1766, 2000     

Effect of amphoteric dispersant on the dispersion properties of nano‐SiO2 particles

An amphoteric polycarboxylate dispersant (APC) was synthesized by copolymerization of acrylic acid (AA), methacryloxyethyltrimethyl ammonium chloride (DMC), and isopentenol polyoxyethylene ether (IPEG). The molecular structure of APC was characterized by FT‐IR, ¹H‐NMR, and GPC. Effect of the dosage of APC on the rheological performance of nano‐SiO₂ suspension was investigated by measurements of the plastic viscosity. The results indicated that the best dispersion effect of APC was obtained when the dosage of APC was about 10 wt % (by the weight percent of nano‐SiO₂), which can maintain the dispersion of nano‐SiO₂ suspension uniformly for 4 h without settlement. Meanwhile, the zeta potential value on the surface of nano‐SiO₂ particles shows that the better dispersion performance of APC was attributed to the solvation water film formed by the polyoxyethylene side chains and the electrostatic repulsion formed by positively groups (C?N⁺) on the APC structure combined with ‐SiO^– groups on the surface of nano‐SiO₂ particles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45075.     

Interactions of active carbon with low‐ and high‐molecular weight polyethylene glycol and polyethylene oxide

Composites of active carbon in a polymeric matrix composed of polyethylene oxide (PEO) and polyethylene glycol (PEG) having different molecular weight distributions were obtained by melt mixing. Characterization of the amount of bound polymer in the whole range of composition for the polymeric matrix has been performed after dissolution of the matrix in water. Size exclusion chromatography of the solution has been used to determine the composition of the polymeric bound layer. It has been shown that in these conditions of mixing, the amount of bound polymer slightly decreases from a pure PEG to a pure PEO matrix. Furthermore, PEO is preferentially bound to the active carbon. A simple model is used to show that bonding occurs preferentially by monomeric units rather than by chain ends. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3490–3497, 2006     

Effect of aluminoxane on molecular weight and molecular weight distribution of polyethylene prepared by an iron‐based catalyst

A series of aluminoxanes, tetraethylaluminoxane (TEAO), tetraalkylaluminoxane (TAAO), Et₂AlOB(4 ? F ? C₆H₄)OAlEt₂ (BTEAO) and ethyl‐iso‐butylaluminoxane modified with p‐fluorophenylboric acid (BEBAO), were prepared and their effects on molecular weight (MW) and molecular weight distribution (MWD) of polyethylene prepared by the iron‐based catalyst [(ArN?C(Me))₂C₅H₃N]FeCl₂ (Ar?2,6‐dimethylphenyl) ( 1 ) were investigated. It was found that TEAO and BTEAO were highly efficient activators for iron‐based catalysts and introducing the branched bulky group (eg iso‐Bu) into the aluminoxane activator could improve the MW of the resulting polyethylene. The MW of polyethylene produced by activators modified by p‐fluorophenylboric acid was higher than for other aluminoxane activators. The TEAO‐ and TAAO‐based polyethylene exhibited attractive bimodal MWD, and the lower MW fraction of bimodal MWD was shown to be produced in the early stage of polymerization due to chain transfer to the aluminium activator. Copyright © 2004 Society of Chemical Industry     

Effect of molecular weight of epoxidized‐natural rubber on viscosity and tack of pressure‐sensitive adhesives

The effect of molecular weight of rubber on viscosity and loop tack of rubber‐adhesives were studied using two grades of epoxidized‐natural rubber, i.e., ENR 25 and ENR 50. Coumarone–indene resin, gum rosin, and petro resin were used as tackifiers. Toluene was used as the solvent throughout the experiment. The adhesive was coated on polyethylene terephthalate (PET) substrate using a SHEEN hand coater. Viscosity was determined by a HAAKE Rotary Viscometer, whereas loop tack was measured by a Llyod Adhesion Tester operating at 10 cm/min. Results show that viscosity increases gradually upto a critical molecular weight of 6.8 × 10⁴ and 3.9 × 10⁴ for ENR 25 and ENR 50, respectively, before a rapid increase in viscosity is observed. Loop tack indicates maximum value at the respective critical molecular weights for the three tackifiers investigated suggesting the culmination of wettability. For both rubbers, loop tack increases with coating thickness due to the concentration effect of adhesive. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mathematical modeling of molecular weight distribution in miniemulsion polymerization with oil‐soluble initiator

A mathematical model for the study of reaction kinetics and molecular weight distributions in miniemulsion polymerization systems with oil‐soluble initiators is presented. The mathematical model allows the computation of the evolution of the complete molecular weight distribution with chain lengths of up to 10⁵ mers in miniemulsion polymerization by direct integration in reasonable computational time. Also, no restriction in the kinetic regime is needed, as the model is able to represent both compartmentalized and pseud‐bulk systems. The model was validated with experimental results for methyl methacrylate and styrene homopolymerizations, with two different oil‐soluble initiators, and adequately represented both the kinetics and molecular weight distributions of these systems. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2128–2140, 2017     

Modeling of molecular weight distribution of gas‐phase polymerization of butadiene

A mathematical model of the molecular weight distribution (MWD) based on a multilayer model and an improved intrinsic kinetics model was proposed to simulate the MWD of the gas‐phase polymerization of butadiene with a heterogeneous catalyst. Intrinsic kinetics and heat and mass‐transfer resistances based on the multilayer model of a polymeric particle were considered in the modeling of the MWD. The effects of the reaction conditions, catalyst particle size, mass‐transfer resistance, deactivation of active sites, and transfer of the polymer chain on the molecular weight and MWD were simulated. The results show that the effects of the deactivation of active sites and transfer of the polymer chain on the average molecular weight are significant and that the effect of the catalyst particle size on the MWD is not significant. The simulation results of the molecular weight and MWD are compared with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 88–103, 2003     

相对分子质量变化对杜仲橡胶应力-应变行为的影响

研究了相对分子质量分布较宽的一组杜仲橡胶分级样品的应力 应变关系 ,揭示了杜仲橡胶随相对分子质量变化而出现脆性 塑性 韧性转变 ,确认了杜仲橡胶脆性 塑性转变的相对分子质量区域。试验结果表明 ,脆性 塑性转变过渡区内 ,杜仲橡胶力学性能不稳定 ;随着相对分子质量增大 ,拉伸强度和扯断伸长率表现为先增大 ,达到最大值后逐渐减小。     

Effects of molecular weight,stereo configuration of PLA,and processing on the dispersion of multiwalled carbon nanotubes and properties of corresponding nanocomposites

Multiwalled carbon nanotubes (MWCNTs) were dispersed and distributed via a co-rotating twin-screw extruder (TSE) in high (h)- and low (l)-molecular-weight amorphous and semicrystalline polylactides (PLAs) (aPLA and scPLA, respectively). Effects of PLA molecular weight and D-lactic acid equivalents content (D-content), as well as processing parameters, were examined on the MWCNT dispersion quality in PLA. The effectiveness of the MWCNT dispersion in various PLA matrices was investigated using scanning electron microscopy (SEM) and small-amplitude oscillatory and transient shear flow rheometry in the molten state. The results showed a better dispersion of MWCNTs in the low-molecular-weight PLA grades (aPLAl and scPLAl). In addition, better MWCNT dispersion was observed in aPLA grades when processed at a higher temperature of 190°C than at 150°C. At 150°C, while MWCNT bundles in aPLAl could be broken down, a good dispersion could not be achieved in aPLAh due to the lower molecular mobility at such a temperature. The electrical conductivity of the samples was also shown to increase as the MWCNT dispersion was improved. The existence of crystallites in scPLA-based nanocomposites, however, disrupted the connectivity of the MWCNTs and decreased the final electrical conductivity. The lower molecular weight aPLAl prepared at 190°C showed the highest electrical conductivity (~10⁻⁵ S/m) at a low loading of 0.5 wt.% MWCNTs.     

Influence of molecular weight of poly(ortho‐ethoxyaniline) on the corrosion inhibition efficiency of mild steel in acidic media

The present work revealed that the chemical polymerization of ortho‐ethoxyaniline yields two types of polymers not only with different spectroscopic properties but also with different molecular weights: (1) a green form, which corresponds to the high molecular weight fraction of the polymer with a molecular weight of 800,000 g mol^?1 based on the polystyrene calibration. It is mainly composed of quinoid and benzoid structures, which is an indication of a half‐oxidized polymer (emeraldine). This form of the polymer is insoluble in water‐miscible solvents like ethanol and methanol and thus cannot be tested in terms of corrosion inhibition efficiency; (2) a red form, which corresponds to the low molecular weight fraction of the polymer with a molecular weight of 44,000 g mol^?1. It is composed mostly of quinoid structures and exhibits an oxidation state similar to that of the completely oxidized polymer (pernigraniline). In our case, the polymer fraction, which is soluble in alcohol, was first tested as a corrosion inhibitor for mild steel in acidic media, not only at conventional molecular weight (44,000 g mol^?1) but also at different molecular weights. These different molecular weights of the polymer were obtained by adding varying amounts of neutral salt to the synthesis environment. Next, the effect of the molecular weight of the red form of the polymer on the corrosion inhibition efficiency of mild steel in hydrochloric acid solutions was investigated. The obtained results showed that the adsorption of the polymer alcoholic form obeys a Temkin adsorption isotherm with no significant change as function of inhibition efficiencies for a series of molecular weights ranging from13,000 to 124,000 g mol^?1. The effect of temperature on the corrosion behavior of mild steel in 1M HCl with addition of 100 ppm of the alcoholic form of poly(ortho‐ethoxyaniline) was studied in the temperature range 25–60°C. The associated activation corrosion energy was determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1275–1284, 2004     

Effect of immobilized neutral protease on the preparation and physicochemical properties of low molecular weight chitosan and chito‐oligomers

Neutral protease was immobilized on glutaraldehyde‐pretreated N‐succinyl chitosan hydrogel beads and the biocatalyst obtained was used for the preparation of low molecular weight chitosan and chito‐oligomers with molecular weight of 1.9–23.5 kDa from commercial chitosan. Factors affecting the chitinolytic hydrolysis were described. The degradation was monitored by gel permeation chromatography. The structure of degraded chitosan was characterized by Fourier transform infrared, X‐ray diffraction and liquid chromatography‐mass spectrometry. Immobilized neutral protease showed optimal depolymerization at pH 5.7 and 50°C. The degree of deacetylation of the hydrolysates did not change compared to that of the initial chitosan. The decrease of molecular weight led to transformation of crystal structure but the chemical structures of residues were not modified. The degree of polymerization of chito‐oligomers was mainly from 3 to 8. The method allows cyclic procedures of immobilized enzyme and N‐succinyl chitosan support utilization, and is suitable for a large‐scale production of the low molecular weight chitosan and chito‐oligomers free of protein admixtures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4185–4193, 2006     

Study on gel‐spinning process of ultra‐high molecular weight polyethylene

An ultra‐high molecular weight polyethylene (UHMW‐PE) fiber was prepared by gel spinning using general kerosene as the solvent and gasoline as the extraction solvent. The process of the phase separation of gel as‐spun, spun under various spinning conditions, was investigated. Its extracting and drying process were also studied. The results reveal that the gel as‐spun, spun under a lower spin draft and a lower spin quenching temperature, extracted in times and dried under free‐shrinkage, exhibits a good afterdrawability that eventually endows the fiber with excellent mechanical behaviors. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 670–675, 1999