Series Of Latexes Research Articles

Preparation of styrene–butyl acrylic latex films with impact resistance properties and their applications as water-based damping coating

Water-based damping coatings to achieve both low-frequency damping and high-frequency impact protection must be developed. Herein, a series of latexes containing a styrene–butyl acrylate chemical crosslinking framework and a dynamic crosslinking impact hardening polymer are synthesized to fabricate water-based damping coatings. Long-chain-based lauryl methacrylate is used to improve the compatibility of styrene–butyl acrylate and impact hardening polymer (IHP) to prepare a composite film (BSL–IHP). The BSL–IHP film exhibits an excellent low-frequency damping ability. The loss factor (tanδ) of the prepared film is up to 1.54, and the effective damping temperature range can be extended to 80 °C. Further, it exhibits excellent impact-resistance properties at high frequencies. The impact energy absorption efficiency of the BSL–IHP film raises to 76.8 % under high-speed impact. In addition, stress response and superior self-healing properties (efficiency = 93.1 %) can be endowed to the film to realize the combination of low-frequency damping and high-frequency impact protection of water-based damping coating which possesses a wide and bright scope in the future.

Dual role of methyl-β-cyclodextrin in the emulsion polymerization of highly hydrophobic plant oil-based monomers with various unsaturations

Although series of latexes from plant oil-based acrylic monomers (POBMs) were recently synthesized in emulsion, two factors—allylic termination (the chain transfer reaction to the fatty acid double bonds) and the poor aqueous solubility of POBMs—lead to the lower total monomer conversion and molecular weight of the resulting latex polymers.In this study, amphiphilic oligosaccharide, methyl-β-cyclodextrin (M-β-CD), was used to improve the polymerizability of monomers from high oleic soybean (HO-SBM) and linseed (LSM) oil in copolymerization with styrene. Using X-ray diffractometry and differential scanning calorimetry, interactions between the monomers and M-β-CD were confirmed, while the formation of 1:1 complex from oligosaccharide and each monomer molecules was demonstrated by mass spectrometry.In the presence of “host-guest” complexes, polymer yield increases as the coagulum amount drops during the emulsion polymerization of both plant oil-based monomers with styrene indicating their enhanced aqueous solubility. Remarkably, latex polymers with a consistently higher molecular weight were obtained in the presence of M-β-CD. The complex formation and incorporation of monomer molecules into the oligosaccharide cavities protect the fatty acid moieties and diminishes chain transfer. The latter assumption was quantitatively confirmed in 1H NMR spectroscopy by determining the number of protons of the alkyl carbon−carbon double bonds (–CH = CH–) and the bisallylic hydrogen atoms (–CH = CH–CH2–CH = CH–) in the unsaturated fatty acid moieties of the latex copolymers. The observed effect is more pronounced for more unsaturated monomer from linseed oil.Based on the obtained results, M-β-CD plays a dual role in both enhancing POBM polymerizability as well as protecting against allylic termination chain transfer.

Versatile Platform for Controlling Properties of Plant Oil-Based Latex Polymer Networks

A series of latexes from acrylic monomers (made from olive, soybean, linseed, and hydrogenated soybean oils), significantly different in terms of fatty acid unsaturation, were synthesized using miniemulsion copolymerization with styrene. The number-average molecular weight and the glass transition temperature of the resulting copolymers with high levels of biobased content (up to approximately 60 wt %) depend essentially on the amount of unsaturation (the number of double bonds in triglyceride fatty acid fragments of plant oil-based monomers) in the reaction feed. When plant oil-based latex films are oxidatively cured, the linear dependence of the cross-link density on reaction feed unsaturation is observed. Dynamic mechanical and pendulum hardness measurements indicate that the properties of the resulting plant oil-based polymer network are mainly determined by cross-link density. On the basis of the linear dependence of the cross-link density on monomer feed unsaturation, it can be concluded that the la...

Preparation and Characterization of Enzymatically Degraded Starch-g-Poly(styrene-co-butyl acrylate) Latex for Paper Coating

Graft copolymerization of styrene and n-butyl acrylate onto enzymatically degraded starch was carried out via surfactant-free emulsion polymerization. The cassava starch was degraded by α-amylase before copolymerization, which greatly enhanced the starch content in copolymer. A series of latexes with small particle size, narrow size distribution, and high stability were prepared. The effect of starch degradation on graft copolymerization was investigated. High grafting efficiency was obtained. The application test of the latex showed that the surface strength of coated paper was improved, and all the other properties are very close to those of paper coated with conventional styrene-acrylate latex.

Particle size and shell composition as effective parameters on MFFT for acrylic core–shell particles prepared via seeded emulsion polymerization

Abstract In this study, acrylic-based copolymer particles were prepared with core–shell morphology and the effect of T g of the shell, particle size and their bimodal size distribution on minimum film formation temperature (MFFT) were investigated. The main goal was to optimize conditions to obtain latexes with low MFFT and appropriate mechanical properties. These will develop the applicability of such water-borne binders as paints and coatings at ambient conditions. A series of latexes with core–shell morphology with variable T g of the shell from −56 to 30 °C were prepared and the MFFT, hardness and thermal behavior of the obtained films were studied. Then a series of latexes with particle sizes ranging from 46 to 960 nm were prepared and the effect of particle size on MFFT was studied too. By inducing the formation of secondary nucleation during emulsion polymerization, latexes with bimodal size distribution were obtained and the effect of presence of such particles on film formation was investigated. Results indicate that latexes with appropriate composition and bimodal particle size distribution lead to optimized performance in both mechanical and film formation properties as a proper choice for water-borne coatings.

Morphology Observation of Latex Particles with Scanning Transmission Electron Microscopy by a Hydroxyethyl Cellulose Embedding Combined with RuO4 Staining Method

Imaging of latex particles, especially those with low glass transition temperature (Tg) has been a challenging issue. Different sample preparation methods for characterization of the morphology of a poly(n-butyl acrylate)/polystyrene two-phase latex are discussed and compared in this study. A method via hydroxyethyl cellulose embedding combined with ruthenium tetraoxide (RuO4) staining for scanning transmission electron microscope (STEM) observation is developed. By using this method, the spherical shape of latex particles can be maintained without deformation. The degree of incorporation of RuO4 into latex particles and cellulose matrix is different, which makes latex particles readily identifiable from cellulose matrix under STEM. A series of latexes with different structures such as copolymer latex and organic-inorganic hybrid latex were also successfully investigated by this method. The results indicate this specimen preparation method can be applied to study the morphology of a wide range of latex systems.

Synthesis and characterization of model carboxylated latexes for studies of film formation from latex blends

Poly(n-butyl methacylate-co-n-butyl acylate) (P(BMA/BA)) soft latexes (car- boxylated and noncarboxylated) were synthesized using a semicontinuous emulsion polymerization process that was designed on the basis of a theoretical calculation to determine the suitable surfactant (i.e., sodium dodecyl sulfate (SDS)), monomer, and water feed rates to maintain a constant particle number throughout the polymerization (guaranteeing monodispersity in the particle size), to obtain a homogeneous copolymer composition, and to independently control the particle size and carboxyl group concen- tration. The experimental results support the theoretical calculation. The surface coverage of the carboxyl groups present on the soft latex particles ranges from 7.6 to 21.9% for a series of latexes with particle sizes around 120 nm. In another series of latexes, the particle size was varied over a range from 120 to 450 nm. Monodisperse carboxylated polystyrene hard latexes were synthesized by shot growth (batch) and semicontinuous processes. The shot growth method is somewhat inflexible in providing more choices in surfactant, particle size, and surface carboxyl coverage. A semicontinu- ous process designed using a similar method used for the synthesis of P(BMA/BA) latexes successfully eliminated the drawbacks of the shot growth process. In this way, the changes in the surface carboxyl coverage (varies from 0 to 77.2%) was independent of the particle size, which was precisely controlled by the amount of styrene fed under suitable styrene and SDS feed rates. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 644 - 659, 2000

Effects of surface functional groups on film formation and tensile strength development in reactive latex systems

AbstractThe effect of surface functional groups on chain interdiffusion at the interfacial zone of reactive latexes was investigated. A series of latexes with different surface functionalities was prepared by batch or shot‐growth emulsion polymerizations. The particle surface properties were varied by changing the number density of functional groups. The rate of tensile strength development decreases with the increasing number density of surface functional groups, which indicated that inter‐particle crosslinking restricted the interdiffusion of polymer chains during film formation and annealing. The average diffusion coefficient D of polymer chains across particle interfaces was obtained from dynamic mechanical analysis and compared well with the results from the rate of tensile strength development. The magnitude of D of the reactive latex film was lower than that of the homopolymer film. The lower chain mobility of reactive latexes prevented mechanical strength development.

Dielectric spectroscopy for characterization of the microstructure of copolymers

Thermally stimulated current spectroscopy has been applied to the characterization of amorphous phases in multiphasic polymers. A preliminary study of the homopolymer has shown that the compensation diagram can be used for defining the structure of an amorphous phase. In synthetic copolymers, the compensation diagram gives phase segregation. Data obtained on a series of latexes are reported as an example. The same methodology can be used in natural copolymers. In the collagen investigated, despite its complex chemical structure, simple behavior of the biphasic copolymers has been found. >

Caractérisation des copolymères amorphes par spectroscopie diélectrique TSC/RMA

Thermally Stimulated Current, TSC/RMA spectroscopy has been applied to the characterization of amorphous phases in multiphasic polymers. The particularity of this technics is to allow to get experimentaly the relaxation map of the transitions.A preliminary study of homopolymer has shown that the compensation diagram can be used for defining the “structure” of an amorphous phase. In amorphous copolymers, the compensation diagram gives phase segregation. Data obtained on a series of latex have been reported, as example.

N-Substituted Acrylamide-Styrene Copolymer Latices II. Polymerization Behavior and Thermosensitive Stability of Latices

Two kinds of N-substituted acrylamides having different hydrophilicity were copolymerized with styrene in soap-free aqueous media. The polymerization behavior of acryl-amides depended on their hydrophilicity. The resulting latices were stable at low temperature and low electrolyte concentration but they flocculated above a critical temperature and a critical electrolyte concentration. The critical conditions were decided by the components on particle surface and a series of latices having the critical temperature between 5 and 50°C could be prepared. Reversible transition between dispersion and flocculation by changing temperature was observed in some latices.

The formation of small scale granularities in latex particles

A series of latices were synthesized using emulsifier-free emulsion copolymerization of styrene and sodium styrene sulfonic acid. The final latex particles display an internal granular structure which can be ascribed to the primary particles present in the early stages of particle growth. In these systems, the primary particles appear to have maintained their integrity during the swelling and growth stage.

The State of Polydispersion of Hevea Latex. II.

Abstract The influence of the degree of dispersion in latex on the composition and properties of the rubber was studied in detail by means of a series of latices, the mean particle size of which ranged from 1.1 to 0.15µ in diameter. These fractions were first obtained by centrifugation of preserved latex, and the degree of distribution was measured by photomicrographic analysis and by sedimentation. This method of fractionation yields latices and rubbers with compositions which differ widely. With decrease in the size of the particles, their surface area per unit of rubber increases, and the percentage of nonrubber components which is adsorbed irreversibly or which is dissolved in the serum increases greatly. On the contrary, the degree of polymerization decreases with decrease in the diameter of the particles. This may be explained by the fact that, in the beginning, the polymerization of the globules is relatively low, and that it progresses under the influence of a catalyst present in the serum. In brief, then, systematic dispersoidal analysis of Hevea latex is of prime importance in the plantation rubber industry.