Studies on suspension and emulsion. LX. Composite polymer emulsion film with temperature-sensitive properties

The mechanical and optical properties of film cast from poly(ethyl acrylate)/polystyrene composite emulsion prepared by seeded emulsion polymerization were changed drastically by heat treatment. Such temperature-sensitive properties can be controlled by regulating the contents and the glass transition temperature of polymer. It was concluded that such a specific phenomenon is due to phase inversion in the heterogeneous structure of the film derived from the particle morphology determined by the polymerization recipe.     

Preparation of two‐layer film having porous structure by emulsion blend technique

A two‐layer film consisting of a tacky layer (air side) and a porous nontacky layer (release‐paper side) was prepared by casting blend emulsion on a release paper, in which 150‐nm 2‐ethylhexyl acrylate–2‐methoxyethyl acrylate–acrylic acid terpolymer particles having high storage stability and 542‐nm ethyl acrylate–methyl methacrylate copolymer particles having low storage stability were dispersed. Both emulsion particles were produced by emulsifier‐free emulsion copolymerizations. The difference of tackiness between both surfaces increased with increases in the film‐formation time and the concentration of electrolytes in the blend emulsion, and resulted in the two‐layer film. The film had a high water vapor permeability, which is also needed for medical adhesive tape. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2027–2033, 2003     

Preparation of asymmetric film by blending two kinds of polymer emulsions having greatly different storage stabilities

Two kinds of anionic polymer emulsions with different particle sizes were blended and cast on a release-paper at 30°C. One was poly(butyl acrylate) emulsion, and the other was ethyl acrylate–methyl methacrylate (1 : 1, weight ratio) copolymer emulsion. They were produced by emulsifier-free emulsion polymerization. The blend films prepared in an appropriate range of the blend ratio had a great difference in tackiness between both surfaces: The air-side surface exhibited tackiness and the release-paper side showed nontackiness. The forming mechanism is discussed.     

Studies on suspension and emulsion. XLVI. Emulsifier-free emulsion polymerization of styrene in acetone–water

Emulsifier-free emulsion polymerization of styrene in acetone–water medium was carried out using potassium persulfate as initiator. Below acetone content of 40 vol %, stable emulsion was prepared and polymerizations were remarkably fast compared with those in pure water. The particle size decreased from 0.5 to 0.17 μm with an increase in acetone content in the range 0–40 vol %, and the distributions were very sharp. The optimum polymerization for the preparation of the stable emulsion was: styrene, 20 vol %; acetone/water, 40/60 (v/v); KPS, 3.4 × 10^?3 mole/l; temp., 90°C.     

Studies of porous polymer gels. I. One-step suspension technique for preparation of moderately crosslinked methacrylic acid gels

A new method of preparation of carboxyl cation exchangers directly from methacrylic acid and divinylbenzene is described. A suspension technique with a concentrated aqueous calcium chloride solution as the water phase was used. n-Octane and toluene were inert diluents of the monomers. The copolymers obtained have high ion-exchange capacity (9.6–10.6 mequ./g) and porous structure.     

苯丙乳液的最低成膜温度及其影响因素分析

简单介绍聚合物乳液的最低成膜温度及其测定方法,详细讨论了聚合物乳液组成、聚合物极性、单体亲水性、聚合物乳胶粒子性能、乳化剂、增塑剂及成膜助剂等因素对聚合物乳液最低成膜温度的影响。     

Studies of porous polymer gels. III. Swelling behavior of porous poly(methacrylic acid) gels

Further studies of porous suspension copolymers of methacrylic acid and divinylbenzene (DVB) are reported. The qualitative structure model of the copolymers proposed previously is used to interpret the ion-exchange properties, sorption of water and aqueous sodium chloride solution, swelling, and neutralization rate. It is proposed that the close to ideal NON-SOL methacrylic acid–divinylbenzene copolymers are composed of rigid microgels and lightly crosslinked poly(methacrylic acid). The latter swollen in water gives the gel, which tends to occupy the accessible space in the copolymer bead together with macropores detectable in the dry state. For the copolymers studied, the DVB content, 5.0 and 9.1% by weight, affects the rigid portion dimension and the extent of swelling of the whole bead, while the expansion of linear chains is determined by the distance between microgels.     

Formation of porous natural-synthetic polymer composites using emulsion templating and supercritical fluid assisted impregnation

Summary Porous natural-synthetic polymer composites were prepared using an alginate emulsion templating step followed by supercritical carbon dioxide (sc-CO₂) assisted impregnation (and subsequent polymerisation) of synthetic monomer mixtures. In the impregnation step, an initiator and either 2-hydroxyethylmethacrylate (HEMA), butylmethacrylate (BMA), ethyleneglycoldimethacrylate (EGDMA) or trimethylolpropanetrimethacrylate (TRIM) monomers, respectively, were used. After impregnation into the porous alginate foam, the synthetic monomer(s) were polymerised in situ, forming porous composites with increased stiffness. A number of methods were used to assess the effects of the impregnation/polymerisation process including uniaxial compression testing, scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), helium pycnometry and Fourier transform infra-red (FTIR) spectroscopy. Our results suggest that alginate foams impregnated with HEMA show higher weight gains and are stiffer than those impregnated with BMA. Such stiffer porous composites are potentially better suited than the unmodified materials in applications such as tissue engineering (cell-seeded) scaffolds, where mechanical conditioning is desired to stimulate cells for development of neo tissue growth.     

Studies on polymer latex films: I. A study of latex film morphology

Polymer films have been formed from poly (butyl methacrylate) latices prepared by surfactant-free emulsion polymerisation. The latices having also been cleaned by microfiltration constitute model colloid particles and hence form ‘model’ films. A novel freeze fracture replication and transmission electron microscopy technique was employed to study film morphology. It demonstrated the presence of interparticle boundaries between latex particles deformed into dodecahedra and the particle packing order without the need for a staining technique. The time and temperature of film formation and storage was shown to affect the degree of particle coalescence. Solvent cast films were also studied for comparison purposes.     

Tailoring mechanical properties of highly porous polymer foams: Silica particle reinforced polymer foams via emulsion templating

The aim of this work was to synthesise highly open porous low-density polymer foams with superior mechanical properties by the polymerisation of the organic phase of concentrated emulsions. The continuous organic phase of the concentrated emulsion template occupying up to 40 vol% was polymerised leading to polymer foams with much improved mechanical properties. The Young's modulus as well as the crush strength of the foams was further increased dramatically by reinforcing the polymer phase with nanosized silica particles. To ensure that the silica particles were covalently incorporated into the polymer network, methacryloxypropyltrimethoxysilane (MPS) was added to the formulation, which reacts with the silica via hydrolysis reactions. The Young's modulus of silica reinforced foams increased by 280% and the crush strength by 218% in comparison to foams without reinforcement.     

Study on emulsion and suspension in situ polymerization

A novel and simple method of emulsion and suspension in situ polymerization was designed for preparing a composite of polystyrene containing core–shell emulsion particles. The advantage of this method was that it did not need a complex process, such as emulsion breaking, washing, drying, and so on, during transforming from emulsion polymerization to suspension polymerization. First, the core–shell particles of poly(styrene/bisphenol A dimethyl methacrylate)/polystyrene [P(St/BPADA)/PS] with crosslinking structure were synthesized by emulsion polymerization. Then the latex was broken with electrolyte dripping and the emulsion particles became swollen and transformed into the monomer in the suspension polymerization system. Thus the emulsion and suspension in situ polymerization could be carried out successfully. The mechanism of the process was investigated in detail. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 404–412, 2005     

高内相乳液聚合制备多孔整体聚合物的孔结构调控与表征

以苯乙烯、二乙烯基苯为原料,山梨糖醇酐单油酸酯Span80为乳化剂,过氧化苯甲酰(BPO)为引发剂,氯化钙水溶液为分散相,通过高内相W/O乳液体系制备Poly HIPE。探讨了不同油水比、乳化剂用量和二乙烯基苯含量对聚苯乙烯(PS)/二乙烯基苯DVB型Poly HIPE孔结构、密度和比表面积的影响。结果表明,随着油水比的减小,乳液稳定性增强,Poly HIPE孔径变大,贯通孔数量增多;增加乳化剂用量或单体中二乙烯基苯比例,Poly HIPE的孔径变小,贯通孔数量增多。除此之外,研究还发现油水比的减小使得Poly HIPE的表观密度和比表面积降低,而提高乳化剂用量和二乙烯基苯比例可提高Poly HIPE的表观密度和比表面积。     

LiTFSI-乙酰胺熔盐与聚丙烯膜复合的聚合物电解质的研究

二(三氟甲基磺酸酰)亚胺锂LiN(SO2CF3)2,即LiTFSI与乙酰胺形成的新型室温熔盐具有优良的电化学性质和热稳定性。以高强度的聚丙烯多孔薄膜为基体,制备了这种与熔盐体系复合的新型聚合物电解质,测试表明其具有良好热稳定性、电导率高等特点,室温电导率为0.27×10-3S/cm,60℃电导率为1.46×10-3S/cm。     

Thermal conductivity of suspension and emulsion materials

A technique for the prediction of effective thermal conductivity of porous materials previously developed by the authors has been extended to suspension and emulsion systems and its capability is supported by the available experimental data. A nomogram which estimates the effective thermal conductivity for these systems from the knowledge of constituent conductivities and proportions is also provided.     

Formation of microheterogeneous film from composite polymer emulsion prepared by the stepwise heterocoagulation method

Blend emulsion of 2 kinds of particles, in which composite polymer particles were prepared by utilizing the stepwise heterocoagulation method proposed by the authors in 1990, was cast to prepare a microheterogeneous film. In the film, a discontinuous phase consisted of large anionic hard polymer particles and a continuous one consisted of small cationic soft polymer particles with the content of 30 wt % as film-forming additives. The storage stabilities of the blend emulsions after the stepwise heterocoagulation were examined under various conditions. The morphology of the film prepared was estimated from attenuated total reflectance Fourier transform infrared spectroscopic and dynamic mechanical spectroscopic measurements. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2221–2228, 1998     

Studies on solvent evaporation and polymer precipitation pertinent to the formation of asymmetric polyetherimide membranes

The characteristics of solvent evaporation and polymer precipitation during the formation of asymmetric aromatic polyetherimide (PEI) membranes via the dry/wet phase inversion method are studied and the results are discussed with reference to membrane preparation. It is shown that the solvent evaporation from the surface of freshly cast films in early evaporation stages can be quantified by an empirical equation with two parameters. Analysis of the evaporation parameters partially explains the interaction effect of membrane preparation variables on membrane performance. The phase separation data for systems PEI/DMAc/H₂O and PEI/NMP/H₂O with and without LiNO₃ additive are determined using the turbidimetric titration method. The kinetic data on solvent–nonsolvent exchange and additive leaching during polymer precipitation in nonsolvent water are measured. The results presented here offer a qualitative basis for the development of asymmetric PEI membranes. © 1995 John Wiley & Sons, Inc.     

Preparation and optical properties of polymer films having lamellar structure and cylindrical air bubbles

Polymer films displaying lustrous, iridescent colors were obtained by irradiation of poly(methyl methacrylate) films containing 1,4-benzoquinone with a medium pressure mercury lamp followed by solvent treatment. The colors were not produced by visible light-absorbing species in the polymer films because the color seen in reflection was complementary to that seen in transmission. It was found from optical and scanning electron microscopic studies of the polymer films that they have two characteristic optical structures; a great number of microcylindrical air bubbles oriented perpendicularly to the film surface and periodic lamellas with planes parallel to the film surface. The colors of the polymer films were thought to be produced by this periodic lamellar structure which would act as a three dimensional optical reflection grating. Continuous color change on tilting the sample could also be explained by the Bragg equation.     

Emulsion of polyurethane having thermosetting properties. II. Relation between the mechanical properties of film and the polyurethane structure

A self-emulsifiable polyurethane emulsion having thermosetting property was prepared by the following procedure: the polyurethane–urea–amine was first prepared by the reaction of diethylene–triamine with a prepolymer containing terminal isocyanate groups in a ketone solvent, and then the primary amino group in the polyurethane–urea–amine was reacted with epichlorohydrin. The mixture was neutralized with an aqueous acid, and finally the ketone solvent was removed by distillation in vacuo. In the polyurethane, polytetramethylene glycol (PTMG) was the base polymer functioning as the soft segment. The present paper reports the effects of the following variables on the mechanical properties of the film prepared from the polyurethane emulsion, i.e., the M _n of PTMG, the molar ratio of diethylene–triamine (DTA) to prepolymer containing terminal isocyanate groups, the structure of the isocyanate end group and the molar ratio of tolylene diisocyanate (TDI) with PTMG. The best elastomer property was realized when M_n of PTMG was 2000, TDI/PTMG molar ratio was 2.0, and prepolymer/DTA molar ratio was 0.85.     

Preparation of core-shell emulsion polymer and optimization of shell composition with respect to opacity of paint film

A series of core-shell latexes comprising a poly(n-butyl acrylate-co-methyl methacrylate-co-methacrylic acid) (PBA/MMA/MAA) core and a poly(styrene-co-acrylonitrile) (PS/AN), poly(butyl acrylate-co-methyl methacrylate) (PBA/MMA) shell were prepared at different shell composition ratios. These core-shell binders were used for preparation of decorative coatings. The latexes were synthesized by a semi-continuous sequential emulsion polymerization and characterized by using transmission electron microscopy (TEM), particle size analyser, viscometry and opacity of paint film. The core-shell emulsion with styrene/acrylonitrile ratio 60/40 as shell composition shows the best optical properties.