Effect of surfactant systems on the water sensitivity of latex films

The effects of three different types of surfactant systems (ionic, polymeric, and electrosteric stabilizers) on the water sensitivity of poly(butyl acrylate‐co‐methyl methacrylate) latex films was examined. The water sensitivity was found to be strongly dependent on the surfactant system used in their preparation. A number of factors, such as the surfactant mobility and crystallinity and surfactant/polymer polarity appeared to affect the water uptake of the films. Highly mobile and crystallizable surfactants yielded high water sensitivity for films containing ionic surfactants, whereas the surfactant polarity had a greater effect on latices stabilized by polymeric surfactants, with the more hydrophilic systems providing greater water uptake. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1813–1823, 2004     

Desorption of the surfactant from the particle surface during latex film formation

Properties of latex films are very dependent on the distribution of the surfactants in the film. It has been recognized that distribution itself depends on the desorption characteristics of the surfactant from the particle-water interface during film formation. This article deals with this problem of surfactant desorption in the particular situation of latex film formation. First, FTIR spectroscopic evidence is presented for desorption of hexadecyl pyridinium chloride (HPCI) in poly(2-ethyl hexyl methacrylate) (P2EHMA) latex films. Some consequences of desorption or non-desorption of various surfactants on the structure and properties of P2EHMA latex films are then presented. This concerns the crystallization of cationic surfactants, HPCI and hexadecyl trimethylammonium bromide (HTAB), in the films and the mechanical properties of films containing ethoxylated nonyl phenol with 10 ethoxy segments (NP10) or sodium dodecyl sulphate (SDS). In the last part, the determination of the fraction of SDS desorbing from the particle–water interface in a model poly(styrene–butyl acrylate–methacrylic acid) latex coalescing in water is described. Other methods for studying desorption are proposed.     

Physical and mechanical properties of nanocomposite barrier film containing encapsulated nanoclay

Waterborne poly(styrene‐co‐butyl acrylate) was prepared via miniemulsion polymerization in which nanoclay (Cloisite® 30B, modified natural MMT) in different concentrations was encapsulated. Scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy confirmed the encapsulation and intercalated‐exfoliated structure of Cloisite® 30B within poly(styrene‐co‐butyl acrylate). The effect of nanoclay content on water vapor permeability, water uptake, oxygen permeability, thermal, and mechanical properties of thin films containing 1.5, 2.56, 3.5, and 5.3 wt % encapsulated Cloisite® 30B in poly(styrene‐co‐butyl acrylate) was investigated. The presence of encapsulated Cloisite® 30B within the polymer matrix improved tensile strength, Young's modulus, and toughness of the nanocomposites depending on the nanoclay content. Water vapor transmission rate, oxygen barrier properties, and thermal stability were also improved. The results indicated that the incorporation of Cloisite® 30B in the form of encapsulated platelets improved physicomechanical properties of the nanoclay‐polymer composite barrier films. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Adhesion of latex films. Part III. Surfactant effects at various peel rates

In order to study the effect of surfactants on the adhesion of latex films, peel energy versus surfactant concentration curves were established at various peel rates. The main latex polymer was a methyl methacrylate (MMA)/ethyl acrylate (EA) copolymer synthesized in the presence of a hydrophilic polyester. Another polymer, less extensively studied, a styrene/butyl acrylate/methacrylic acid terpolymer, was also used for comparison purposes. The surfactants were either sodium dodecyl sulfate (SDS) or ethoxylated nonyl phenol containing 30 segments of ethylene oxide (NP30). The substrates were glass plates or poly(ethylene terephthalate) films. It was found that with SDS-containing films, whatever the substrate or the polymer, the curves went through a maximum, whereas with NP30 they went through a minimum, at medium or high peel rates. When the peel rate was decreased, the curves flattened out and at zero peel rate (extrapolated values), they became horizontal. The peel energies at zero peel rate were three to four times higher than the reversible works of adhesion. Qualitative interpretations are proposed for these results.     

Surface and interfacial FTIR spectroscopic studies of latexes. V. The effects of copolymer composition on surfactant exudation

The influence of copolymer structure on the magnitude of surfactant enrichment to the film—air and film—substrate interfaces of latex films prepared on a polytetrafluoroethylene (PTFE) substrate is investigated. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR FTIR) is used to elucidate the surfactant enrichment by the comparison of butyl acrylate/methyl methacrylate/methacrylic acid (BA/MMA/MAA) and ethyl acrylate/methacrylic acid (EA/MAA) latex systems prepared with various anionic surfactants. It is found that, in all cases, the magnitude of exudation of the sulfonate-containing surfactants manifested by the presence of S—O bending and scissors modes is reduced in the case of the BA/MMA/MAA latex. Similar behavior is observed when the spectra of films prepared on a liquid mercury substrate are compared. It is believed that this behavior results from the longer aliphatic n-butyl groups present in this copolymer that enhances compatibility by providing a greater opportunity for hydrophobic surfactant—copolymer interactions. The butyl groups may also reduce excess interfacial free energy by orienting themselves toward the film interfaces, which, in turn, will reduce the surface tension-induced driving force for surfactant exudation. © 1993 John Wiley & Sons, Inc.     

Phase rearrangement in two-stage emulsion polymers of butyl acrylate and styrene: Mechanical properties

The mechanical and thermal properties of films from a series of two-stage emulsion polymers were investigated. The emulsion polymers were made by polymerizng styrene in the presence of a preformed poly(butyl acrylate-co-divinyl benzene) seed latex. The effects of seed particle size, seed particle crosslinking via the amount of divinyl benzene, styrene/butyl acrylate ratio, and thermal history on the film properties were studied. Latex particles were characterized by light scattering and film formation behavior. Dried films were characterized by differential scanning calorimetry, dynamic mechanical analysis, and stress-strain behavior. Although evidence was obtained for nearly complete phase separation between the polystyrene (PS) and poly(butyl acrylate) (PBA) phases, the site of styrene polymerization and thus the PS phase morphology is influenced by seed particle size, seed crosslinking, and S/BA ratio. The morphology of as-dried films consists of finely dispersed PS domains in a continuous PBA matrix. Thermal annealing above the PS T_g causes coalescence of the PS domains, resulting in significantly improved mechanical properties. The extent of PS phase coalescence is also influenced by the level of seed crosslinking.     

Preparation of surfactant-free vinyl polymers by conventional emulsion polymerization using hydrolysable emulsifiers

Emulsion polymerizations of several vinyl monomers, styrene, methyl methacrylate, butyl methacrylate, butyl acrylate, and vinyl acetate, in water using alkali–hydrolysable cationic surfactants with a betaine ester group (1-alkoxycarbonylmethyl)trimethylammonium chlorides, as emulsifiers were carried out and properties of the resulting latices and the polymers recovered by hydrolysis and salting out were investigated. There were little influences of the surfactants and monomers used here on the polymerizations, forming stable and monodisperse latices with a mean diameter of ca. 70 nm and giving a high molecular weight of polymers at high yields. All polymers were precipitated and recovered by adding a small amount of sodium hydroxide into the latex solutions contained little amount of ionic species. Solvent-cast films of the polymers were found to have surfaces as hydrophobic as those for the corresponding pure polymers prepared by bulk polymerization.     

Reactive surfactants in heterophase polymerization. XVI. Emulsion copolymerization of styrene–butyl acrylate–acrylic acid in the presence of simple maleate reactive surfactants

This study deals with the influence of a copolymerizable surfactant on the stability of lattices. Two main reactive surfactants, one anionic and one nonionic, both containing a reactive part issued from maleic anhydride, were engaged in seeded emulsion polymerizations of styrene‐co‐butyl acrylate‐co‐acrylic acid. The importance of the polymerization conditions clearly appears through the incorporation yield of the surfmers: When good conditions are used, this yield can be as high as 80%. Once stable lattices are synthesized, with a great incorporation of the surfactant, the stability of the colloid (against freeze–thawing cycles or in the presence of concentrated divalent electrolyte solutions) is then largely improved. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2768–2776, 2000     

Surfactants in heterophase polymerization: A study of film formation using force microscopy

Film formation of three different latices was studied using atomic force microscopy. The latices were made from a mixture of butyl acrylate, styrene, and acrylic acid using either a polymerizable or an unreactive anionic surfactant as an emulsifier. Sodium 11-crotonoyloxyundecan-1-ylsulfate and sodium 3-(sulfopropyl)tetradecylmaleate were used as a reactive surfactant and the unreactive surfactant was sodium dodecylsulfate (SDS). The conventional surfactant was found to migrate to the surface of the latex film to a much greater extent than did the reactive surfactants; however, also, the latter were incompletely anchored to the particle. The maleate surfactant was bound to a higher degree than was the crotonate, a finding which is in line with the relative reactivities of the two surfactants. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 187–198, 1997     

Inifer surfactants in emulsion polymerization

Thiol-ended non-ionic surfactants, used in combination with t-butyl hydroperoxide are components of a redox system able to initiate the emulsion polymerization of styrene, as well as control the molecular weight by transfer. Most of the surfactants remain as side products in the water phase, while multimodal molecular weight distributions of polymer are observed depending on the structure of the surfactant, the conversion of the monomer and the process used for feeding the reactor. The maximum incorporation yield of these reactive surfactants in the polymer is around 40%.     

Effect of serum components on styrene/butyl acrylate latex film formation: An in situ examination by ultramicroscopy

Film formation by a surfactant‐stabilized, peroxide‐initiated styrene/butyl acrylate latex was followed in situ by ultramicroscopy. The effects of latex serum components on film formation were observed first by the subjection of the latex to extensive dialysis and then by the separate addition of salt and surfactants. Domains of different particle concentrations were observed in the latex dispersion during liquid evaporation, and their positions were related to those of defects in the dry film. Films obtained with the dialyzed latex showed macroscopic defects, which were not seen in the as‐prepared latex. Partially reconstituted latex (dialyzed, with the later addition of salt but not surfactant) behaved like the as‐prepared latex. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 159–167, 2003     

N-羟甲基丙烯酰胺改性核壳型丙烯酸酯乳液的制备与表征

采用甲基丙烯酸甲酯、丙烯酸丁酯和丙烯酸为反应单体,以N-羟甲基丙烯酰胺(NMA)为功能单体,通过预乳化半连续种子乳液聚合工艺制备了NMA改性核壳型丙烯酸酯乳液,讨论了NMA用量对乳液的凝胶率及离心稳定性和贮存稳定性的影响,并对乳胶膜的吸水性、力学性能及耐热性进行了表征。结果表明:当NMA的用量为1.5%(wt)时,乳液的凝胶率仅为0.23%(wt),具有良好的离心稳定性和贮存稳定性,乳胶膜的吸水性由6.0%(wt)下降至4.5%(wt),铅笔硬度和冲击强度分别由1 H和52 cm提高至2 H和55 cm以上,弯曲强度、附着力及耐热性俱佳。     

Ab initio reversible addition–fragmentation chain transfer emulsion polymerization of styrene/butyl acrylate mediated by poly(acrylic acid)‐block‐polystyrene trithiocarbonate

Ab initio reversible addition–fragmentation chain transfer (RAFT) emulsion polymerization of styrene/butyl acrylate was investigated with the trithiocarbonate macro‐RAFT agent poly(acrylic acid)‐block‐polystyrene (PAA‐b‐PS) as a stabilizer and a RAFT agent. Influences of the amount of ammonium persulfate (APS), the amount of PAA‐b‐PS and the mass ratio of monomers on emulsion polymerization and film properties are discussed. The particle morphology exhibited spherical‐like structure with particles of about 90 nm in diameter and relatively narrow particle size distribution characterized using transmission electron microscopy and dynamic laser scattering. Fourier transform infrared and ¹H NMR spectra showed that the styrene/butyl acrylate emulsion was successfully synthesized. The monomer conversion increased initially with increasing amount of APS, from 0.4 up to 0.8 wt%, and then decreased. The particle size increased and its distribution decreased gradually with increasing amount of APS. The monomer conversion increased from 76.83 to 94.21% as the amount of PAA‐b‐PS increased from 3 to 4 wt%, and then decreased with further increase of PAA‐b‐PS. The particle size decreased and its distribution increased with increasing amount of PAA‐b‐PS. The water resistance and solvent resistance of the polymer films initially increased and then decreased with decreasing mass ratio of butyl acrylate to styrene. © 2014 Society of Chemical Industry     

Effect of cationic surfactant addition on the drag reduction behaviour of anionic polymer solutions

Although extensive research work has been carried out on the drag reduction (DR) behaviour of polymers and surfactants alone, little progress has been made on the synergistic effects of combined polymers and surfactants. In this work, the interactions between drag‐reducing anionic polymer (copolymer of acrylamide and sodium acrylate, referred to as PAM) and drag‐reducing cationic surfactant (octadecyltrimethylammonium chloride, OTAC) are studied. Solutions are prepared using both deionised (DI) water and tap water. The measurement of the physical properties such as electrical conductivity and viscosity are used to determine the surfactant–polymer interactions. The addition of surfactant to the polymer solution has a significant effect on the properties of the system. The critical micelle concentration (CMC) of the mixed surfactant–polymer system is found to be different from that of the surfactant alone. With the addition of surfactant to a polymer solution, a substantial decrease in the viscosity occurs. The observed changes in the viscosity of mixed polymer–surfactant system are explained in terms of the changes in the extension of polymeric chains, resulting from polymer–surfactant interactions. The anionic PAM chains tend to collapse upon the addition of cationic OTAC. The pipeline flow behaviour of PAM/OTAC mixtures is found to be consistent with the bench scale results. The DR ability of PAM is reduced upon the addition of OTAC. At low concentrations of PAM, the effect of OTAC on the DR behaviour is more pronounced. The DR behaviour of polymer solutions is strongly influenced by the nature of water (DI or tap). © 2011 Canadian Society for Chemical Engineering     

Modeling of “living” free‐radical polymerization processes. I. Batch,semibatch, and continuous tank reactors

A comprehensive mathematical model is developed for “living” free‐radical polymerization carried out in tank reactors and provides a tool for the study of process development and design issues. The model is validated using experimental data for nitroxide‐mediated styrene polymerization and atom transfer radical copolymerization of styrene and n‐butyl acrylate. Simulations show that the presence of reversible capping reactions between growing and dormant polymer chains should boost initiation efficiency when using free nitroxide in conjunction with conventional initiator and also increase the effectiveness of thermal initiation. A study shows the effects of the value of the capping equilibrium constant and capping reaction rate constants for both nitroxide‐mediated styrene polymerization (using alkoxyamine as polymer chain seeds) and atom transfer radical polymerization of n‐butyl acrylate (using methyl 2‐bromopropionate as chain extension seeds). Also the effect of introducing additional conventional initiator into atom transfer radical polymerization of n‐butyl acrylate is studied. It is found that the characteristics of long chain growth are determined by the fast exchange of radicals between growing and dormant polymer chains. Polymerization results in batch, semibatch, and a series of continuous tank reactors are analyzed. The simulations also show that a semibatch reactor is most flexible for the preparation of polymers with controlled architecture. For continuous tank reactors, the residence time distribution has a significant effect on the development of chain architecture. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1630–1662, 2002     

Synthesis of poly(butyl acrylate)‐poly(methyl methacrylate) core–shell nanomaterials of anti‐crease‐whitening properties

Core–shell nanomaterials of poly(butyl acrylate)‐poly(methyl methacrylate) were synthesized using a differential microemulsion polymerization method for being used as polyacrylate‐based optical materials, which meet the requirement of anti‐crease‐whitening and proper mechanical strength. The effects of reaction temperature and surfactant amount on the particle sizes, as well as the effect of reaction temperature on the conversion and solid content were investigated to reveal the dependence of the application properties on the reaction conditions. The spherical morphology of core–shell nanoparticles was also studied via transmission electron microscopy. The resulting polymers with a core–shell monomer ratio of butyl acrylate/methyl methacrylate at 32/10 (vol/vol) demonstrated the optimal balanced properties in the anti‐crease‐whitening and mechanical property, confirmed by the visible light transmittance measurement and the dynamic analysis of the viscoelastic properties of the synthesized core–shell nanomaterials. The smaller the particle size, the better the transparency of the resulting polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39991.     

Film formation and mechanical properties of the alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex prepared by miniemulsion copolymerization

Alkoxysilane-functionalized poly (styrene-co-butyl acrylate) latex was prepared via miniemulsion copolymerization of γ-methacryloxypropyltrimethoxysilane (MPS), styrene and butyl acrylate using AIBN at neutral condition. The effects of initiator types, pH values, and MPS contents on the premature cross-linking of the latex particles and the mechanical properties of the films were investigated by the swelling experiments and dynamic mechanical analysis. It was found that the storage modulus of the latex films and the glass transition temperature (T_g) increased with increasing MPS content. The acidification of latex prior to film formation and annealing the latex films could improve the mechanical properties of the films.     

保护胶带用高剥离强度乳液压敏胶的研究

以丙烯酸丁酯(BA)、丙烯酸异辛酯(2-EHA)、甲基丙烯酸甲酯(MMA)、苯乙烯(St)、丙烯酸(AA)、丙烯酸羟丙酯(HPA)为原料进行乳液共聚,合成了保护膜用丙烯酸酯乳液压敏胶。讨论了乳化剂种类及用量、引发剂及缓冲剂用量、聚合温度、聚合时间、种子乳液用量对压敏胶性能的影响。结果表明,合成的压敏胶具有较高的剥离强度和初粘性,同时具有较好的耐高温高湿老化性能。     

苯丙型水性光油乳液的研制

以丙烯酸丁酯、苯乙烯为软硬单体,以丙烯酸、丙烯酰胺等为交联单体,采用单体预乳化、半连续乳液聚合法,制得了一种水性苯丙乳液,适用于配制纸质印刷品上光油。重点探讨了单体比例、乳化剂用量、引发剂用量及加入方法、反应温度等因素对乳液性能的影响。     

Waterborne Polyurethane-Acrylate Containing Different Polyether Polyols: Preparation and Properties

The waterborne polyurethane–acrylate (PUA) was prepared based on isophorone diisocyanate, polyether polyol, dimethylol propionic acid, hydroxyethyl methyl acrylate, butyl acrylate (BA) and styrene (St). Fourier transform infrared spectrometry (FT-IR), Ultraviolet-visible spectrophotometry (UV-Vis) and Differential scanning calorimetry (DSC) were employed to investigate the structures, optical transparency and thermal properties. Some physical properties of the aqueous dispersions such as viscosity, particle size and surface tension were measured. Some mechanical performances and solvent resistance of films were investigated. When the ratio of the BA/St was 30/70, the films had excellent water and alkali resistances. The obtained PUA composites have great potential application such as coatings, leather finishing, adhesives, sealants, plastic coatings and wood finishes.