Acetoacetoxy functionalized natural rubber latex capable of forming cross-linkable film under ambient conditions

This work demonstrates that natural rubber (NR) latex particles containing acetoacetoxy (AcAc) groups are able to undergo cross-linking upon film formation at ambient temperature by reaction with glutaraldehyde (GTA). Natural rubber latex grafted with poly(acetoacetoxyethyl methacrylate) (NR-g-PAAEM) was synthesized by seeded emulsion polymerization, using benzoyl peroxide (BPO) as an initiator in free radical polymerization. The degree of grafting of PAAEM in the graft copolymers was evaluated by ¹H NMR technique. Transmission electron microscope (TEM) was used for investigation the particle morphology of the grafted NR latex. Since the AcAc groups are intentionally attached to the NR particles providing sites of cross-linking at ambient temperature, the cross-linking ability of these sites by reaction with GTA was then investigated. The results revealed that the latex film of NR-g-PAAEM with the addition of GTA had a much higher tensile strength in comparison with the film without GTA. The surface morphology of the NR-g-PAAEM latex film formed in the absence and presence of the GTA cross-linker was also investigated using atomic force microscopy (AFM). By GTA addition into the NR-g-PAAEM latex before film formation, an increase in the root-mean-square (RMS) roughness of the surface of the latex film was observed. Moreover, it was also observed that the NR-g-PAAEM films with the addition of GTA had higher activation energy for thermal degradation than that without the cross-linker. This confirms that the cross-linking reaction took place in the NR-g-PAAEM latex film as a result of its reaction with the GTA.     

Study on the Properties of Blend Rubber Between Grafted Rubber Latex and Natural Rubber Latex by Gamma Radiation

Blend rubber films were prepared by mixing styrene grafted rubber latex and natural rubber latex (NRL) with varying proportions by gamma radiation from Co-60 source at room temperature. Tensile strength, modulus at 500% elongation, elongation at break, permanent set, and swelling ratio were measured. Tensile strength and modulus at 500% elongation attain maximum at 8 kGy radiation dose for blend rubber films. The increase in tensile strength is insignificant, but modulus increases from 5.61 to 7.46 MPa with increased proportion of grafted rubber latex from 40 to 70% in the blend at this radiation dose. Elongation at break, permanent set, and swelling ratio of blend rubber decreases with increase in radiation dose as well as proportion of grafted rubber.     

Heterogeneous latices as binders in porous particle structures

Heterogeneous carboxylated styrene-butadiene (S/Bu) latices were prepared by a two-stage polymerization process, using three seeds of polystyrene with different molecular weights. The second-stage polymer was a copolymer with a fixed S/Bu-ratio of 1 and a methacrylic acid (MAA) content of either 1 or 10 wt %. It has been found that the morphology of the films made from these latices influenced the modulus in the rubbery region of these films. The heterogeneous latices were used as binders in porous structures based on micron-sized kaolin particles. Such structures are typically employed as paper coatings. Polyester substrates were coated with aqueous suspensions containing the kaolin particles and the heterogeneous latex. The coatings were dried at room temperature, which corresponds to the rubbery region of the latex films. It was found that a higher modulus (which is determined here by the morphology of the latex film) in the rubbery region of the films was associated with coating layers with higher porosity, greater light scattering ability, and higher coating gloss. This is interpreted as being the result of a retarded shrinkage of the coating layers during the drying of these structures due to the increase in modulus of the latex films. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 661–670, 1997     

Water‐induced mechanically adaptive behavior of carboxylated acrylonitrile‐butadiene rubber reinforced by bacterial cellulose whiskers

Water‐induced mechanically adaptive rubber nanocomposites were prepared by mixing bacterial cellulose whiskers (BCWs) suspension with carboxylated acerlonitrile‐butadiene rubber (XNBR) latex, followed by latex blending method. The introduction of BCWs into XNBR enhanced the tensile storage modulus (E') significantly, which originated from the formation of a rigid 3D filler network within matrix as well as the interfacial interaction between filler and matrix. The water uptake ratio of nanocomposite films increased with BCWs content, from 5.5% for neat XNBR to 54% for nanocomposite with 20 phr (parts per hundred rubber) BCWs. Upon submersed in water, the nanocomposite films showed dramatic decrease in E′, especially for which filled with high BCWs loadings. For example, E′ of nanocomposite with 20 phr BCWs was decreased by 98.04% after equilibrium swelling compared with only 52.02% for nanocomposite with 3 phr BCWs. The remarkable water‐triggered modulus changes are attributed to the disentanglement of BCWs network after swelling. The prepared XNBR–BCWs nanocomposites with mechanically adaptive properties could contribute to develop the new type of rubber‐based smart materials. POLYM. ENG. SCI., 59:58–65, 2019. © 2018 Society of Plastics Engineers     

Synthesis and properties of composites of starch and chemically modified natural rubber

A means is developed for forming polysaccharide-based composites with useful material properties through use of unmodified and chemically modified natural rubber latex (NRL). Starch was used as a model for polysaccharides. The NRL was modified by grafting with dimethylaminoethyl methacrylate (DMAEMA) to form a latex with cationic water-soluble polymeric ‘hairs’ of polyDMAEMA, which should form hydrogen bonds with starch. Starch solutions, containing 20% glycerol as a film-forming aid, and the modified NRL were mixed and films allowed to form. The unmodified latex acted only as filler in the starch films, but with modified NRL, the mechanical properties of the films were significantly altered. The elastic modulus was greatly decreased and strain at break greatly increased. The glass transition temperature increased from −48 °C to −32 °C, suggesting significant compatibilization. Freeze-fracture TEM micrographs indicate strong interactions between the surface of the modified NRL and starch. The polyDMAEMA chains are more hydrophilic than the starch, and the addition of grafted latex results in a 20° drop of the water contact angle of the formed film, and a 25% increase of the water absorption compared to the native starch; with unmodified NRL, the opposite effect was observed.     

Photo-reactive particle prepared from natural rubber and 3-acryloyloxy-2-hydroxypropyl methacrylate

Photo-reactive particle was prepared by graft-copolymerization of 3-acryloyloxy-2-hydroxypropyl methacrylate (AHM) as a bi-functional monomer onto natural rubber (NR) in latex stage with potassium persulfate (KPS) as an initiator, after deproteinization with urea in the presence of surfactant. A terminal vinyl group of AHM was used for the graft-copolymerization, while the other remained in the resulting graft-copolymer, due to different reactivities of vinyl groups in the end of the bi-functional monomer. After graft-copolymerization, the resulting latex was UV-crosslinked to make chemical linkages between the residual pendant vinyl groups of grafted polymers linking up to the rubber particle. The resulting products were characterized by ¹H NMR and ¹³C NMR measurements. Effects of amount of rubber, monomer concentration and reaction time on conversion, grafting efficiency and amount of residual carbon-carbon double bond after graft-copolymerization were investigated. Under the optimum condition, high conversion of monomer and high amount of residual carbon-carbon double bond after graft-copolymerization were achieved without side reaction. A dramatic increase in modulus after UV-irradiation was associated with the connection of the functional polymer linking up to NR particle.     

Effect of nanosized calcium carbonate on the mechanical properties of latex films

An acrylic dispersed nanosized calcium carbonate filler was added to a prevulcanized latex compound in different amounts. The effect of filler content on the curing time, modulus, tensile strength, elongation at break (Eb) before and after ageing, and the morphology of the films was investigated. Results showed that the curing time decreased with filler loading because of the increased interaction between the filler and rubber matrix, as reflected by the decrease in the apparent swelling index. Modulus at 100% elongation and modulus at 300% elongation increased with filler loading. Tensile strength and Eb increased up to 10 phr of filler loading and then decreased again. Aged films showed improved mechanical properties compared to those of unaged films. Micrographs showed that agglomeration occurred as the filler content was increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1550–1556, 2005     

Formation of transparent conducting films based on core‐shell latices: Influence of the polypyrrole shell thickness

Transparent conducting latex films have been prepared from core‐shell latices. The latex particles have a poly(butyl methacrylate) (PBMA) core of about 700 nm and a very thin polypyrrole (PPy) shell. We have studied the film formation of latices with 1, 2, and 4 wt % PPy and compared this with the film formation of the pure PBMA latex. The film formation process was studied by transparency measurements, atomic force microscopy surface flattening, and transmission electron microscopy on ultrathin sections of films after various annealing times at 120°C. It is demonstrated that highly transparent (>90%) and antistatic films can be produced using these latices. The presence of a polypyrrole shell around the PBMA latex particle seriously hinders the deformation of the particles. The amount of polypyrrole, and thus the shell thickness, is the determining factor for the speed of film formation. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 900–909, 2001     

Preparation and characterization of polysiloxane–polyacrylates composite latices and their film properties

Gamma‐ray induced seeded emulsion polymerization of methyl methacrylate and butyl acrylate was carried out in the presence of a polymerizable polysiloxane seed latex, obtained by ring‐opening copolymerization of octamethyl cyclotetrasiloxane (D₄) and tetramethyl tetravinyl cyclotetrasiloxane (VD₄), catalyzed by dodecylbenzene sulfonic acid (DBSA). A series of polysiloxane seed latices with different molecular weights, vinyl contents and particle sizes was used. The conversion–time curve showed that the polymerization rate was accelerated significantly by the seed latex. The obtained composite latices also showed good storage stability, mechanical stability and high electrolyte resistance ability. By using transmission electron microscopy (TEM), the morphology of the composite latex particles was found to display a quite uniform fine structure. The graft polymerization reactions between the polymerizable polysiloxane and the acrylates were confirmed by Fourier‐transform infrared spectroscopy (FT‐IR) and the graft efficiencies were also studied. The influence of seed content, molecular weight, vinyl content of the polysiloxane and seed latex particles size on the mechanical performance, water absorption ratio, surface properties and transparency of the latex films was also investigated. It was found that the seed content and particles size greatly affect the mechanical performance, water absorption ratio and transparency of the latex films. Copyright © 2005 Society of Chemical Industry     

Studies on the curing behaviour and mechanical properties of styrene/methyl methacrylate grafted deproteinized natural rubber latex

The graft copolymerization of styrene/methyl methacrylate (MMA) onto deproteinized natural rubber (DPNR) latex was carried out using ammonium peroxy disulfate (N₂H₈O₈S₂) as the initiator. The presence of the grafted polystyrene (PS) and polymethyl methacrylate (PMMA) on the rubber backbone was confirmed by FTIR spectroscopy. The effects of monomer concentrations on curing characteristics and mechanical properties were studied. It was found that the cure time and scorch time were increased with increasing monomer concentration whereas the torque_max–min value was slightly decreased. It was also noted that the increase in the monomer concentration resulted in stiffer rubber with increased modulus and reduced elongation at break.     

Degradability testing of radiation-vulcanized natural rubber latex films

The degradability under various conditions of five kinds of radiation-vulcanized natural rubber latex (RVNRL) films was studied. The treatments were leaching in methanol, leaching in 1% ammonia solution, mixing with tris(nonylated phenyl)phosphite (TNP) antioxidant, blending with poly(methyl methacrylate) (PMMA), and grafting with PMMA, Comparisons were made with sulfur-vulcanized natural rubber latex (SVNRL) film. RVNRL films SVNRL film can be kept for a long time when indirectly exposed to sunlight at room temperature. However, the former degraded much more rapidly than did the latter. TNP was found to be very suitable as an antioxidant to prolong the life of RVNRL films under dry conditions. PMMA, either blended or grafted with RVNRL, was ineffective in the prevention of deterioration of RVNRL films. The rapid degradation of RVNRL products could be an advantage over SVNRL products in environmental and wildlife conservation. © 1994 John Wiley & Sons, Inc.     

The influence of latex blend composition on crosslinking and mechanical properties

Model reactive latices were synthesized by semicontinuous emulsion copolymerization of n‐butyl methacrylate and acetoacetoxyethyl methacrylate or dimethylaminoethyl methacrylate. The two functional latices were then blended in various ratios to study the influence of blend composition on crosslinking and mechanical properties of the resulting films. Crosslinking was quantified through swelling measurements. It was found that the crosslink density increased with increasing amounts of acetoacetoxy‐functional polymer. In addition, the crosslink density exhibited two maxima, at 30/70 and 70/30 (acetoacetoxy‐functional latex/amino‐functional latex) blend compositions. The mechanical properties of the films were quantified by dynamic mechanical analysis (DMA). It was shown that optimal mechanical properties occurred when the particles packed most efficiently at the 30/70 and 70/30 blend compositions. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3774–3779, 2007     

Complexation of poly(dimethylsiloxane)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) latex with poly(dimethylsiloxane)/poly(vinyl acetate‐co‐butyl acrylate) latex

Two latices—the poly(dimethylsiloxane) (PDMS)/poly(methyl methacrylate‐co‐butyl acrylate‐co‐methacrylic acid) system (PA latex) and the PDMS/poly(vinyl acetate‐co‐butyl acrylate) system (PB latex)—were prepared by seeded emulsion polymerization, and PA/PB complex latices were obtained through the interparticle complexation of the PA latex with the PB latex. In addition, for the further study of the interparticle complexation of the PA latex with the PB latex, copolymer latices [PDMS/methyl methacrylate‐co‐butyl acrylate‐co‐vinyl acetate‐co‐methacrylic acid) (PC)] were prepared according to the monomer recipe of the complex latices and the polymerization process of the component latices. The properties of the obtained polymer latices and complex latices were investigated with surface‐tension, contact‐angle, and viscosity measurements. The mechanical properties of the coatings obtained from the latices were investigated with tensile‐strength measurements. The results showed that, in comparison with the two component latices (PA latex and PB latex) and the corresponding copolymer latices (PC latices), the PA/PB complex latices had lower surface tension, lower viscosities, and better wettability to different substrates. The tensile strengths of the coatings obtained from the complex latices were higher than the tensile strengths of the coatings from the two component latices and copolymer latices. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2522–2527, 2004     

Surface structure and properties of water‐based polymer coating materials prepared by the complexation of two polymer latices with chemically complementary structures

In this study, water‐based polymer coating materials used for the surface coating of substrates with lower surface energies were prepared by the complexation of two‐component polymer latices containing polydimethylsiloxane (PDMS) and having chemically complementary structures. The film‐forming performance of the polymer latices and the surface structures and properties of the coatings formed by the polymer latices were studied by means of scanning electron microscopy and by the measurement of mechanical strength, thermal performance, water absorbability, and contact angle. When the two‐component polymer latices [the poly(methyl methacrylate‐co‐butyl acrylate‐co‐methyl acrylic acid)/polydimethylsiloxane system (PA latex) and the poly(methyl methacrylate‐co‐butyl acrylate‐co‐pyrrolidone)/polydimethylsiloxane system (PB latex)] were compared, the complex polymer latex formed by the complexation of the PA latex with the PB latex had the best film‐forming performance, with formed coatings that were more smooth and had fewer less cracks. Also, compared to the two coatings formed by the two‐component polymer latices, the coatings formed by the complex polymer latex had a unique structure, a higher mechanical strength and elongation, a higher decomposing temperature, and better water resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1748–1754, 2003     

Improving blood compatibility of natural rubber by UV‐induced graft polymerization of hydrophilic monomers

Natural rubber (NR) latex films surface‐grafted with hydrophilic monomers, poly(ethylene glycol) methacrylate (PEGMA), N‐vinylpyrrolidone (VPy), and 2‐methacryloyloxyethyl phosphorylcholine (MPC), were prepared by UV‐induced graft polymerization using benzophenone as a photosensitizer. The grafting yield increases of vulcanized NR latex films as a function of time and monomer concentration were of lesser magnitude than those of the unvulcanized NR latex films. This can be explained as a result of the crosslinked network generated during vulcanization acting as a barrier to the permeation of the photosensitizer and the monomer. The appearance of a characteristic carbonyl stretching in the attenuated total reflectance‐Fourier transform infrared spectroscopy (ATR‐FTIR) spectra of NR latex films after the surface grafting of PEGMA and MPC indicates that the modification has proceeded at least to the sampling depth of ATR‐FTIR (∼ 1–2 μm). According to the water contact angle of the modified NR latex films, the surface grafting density became higher as the grafting time and monomer concentration increased. The complete absence of plasma protein adsorption and platelet adhesion on the surface‐modified NR latex films having grafting yield above 1 wt % is a strong indication of improved blood compatibility. Results from tensile tests suggest that graft polymerization does not cause adverse effects on the mechanical properties of vulcanized NR latex films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of organoclay‐rubber nanocomposites via a new route with skim natural rubber latex

Skim natural rubber latex (SNRL) is a protein rich by‐product obtained during the centrifugal concentration of natural rubber (NR) latex. A new method to recover rubber hydrocarbon and to obtain nanocomposites with organoclay (OC) was investigated. The approach involved treatment of SNRL with alkali and surfactant, leading to creaming of skim latex and removal of clear aqueous phase before addition of OC dispersion. Clay mixed latex was then coagulated to a consolidated mass by formic acid, followed by drying and vulcanization like a conventional rubber vulcanizate. X‐ray diffraction (XRD) studies revealed that NR nanocomposites exhibited a highly intercalated structure up to a loading of 15 phr (parts per hundred rubber) of OC. Transmission electron microscopy studies showed a highly exfoliated and intercalated structure for the NR nanocomposites at loadings of 3–5 phr organically modified montmorillonite (OMMT). The presence of clay resulted in a faster onset of cure and higher rheometric torque. The rubber recovered from skim latex had a high gum strength, and a low amount of OC (5 phr) improved the modulus and tensile strength of NR. The high tensile strength was supported by the tensile fractography from scanning electron microscopy. Thermal ageing at 70°C for 6 days resulted in an improvement in the modulus of the samples; the effect was greater for unfilled NR vulcanizate. The maximum degradation temperature was found to be independent of the presence and concentration of OC. The increased restriction to swelling with the loading of OC suggested a higher level of crosslinking and reinforcement in its presence. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3277–3285, 2006     

Physical and mechanical properties of highly plasticized pectin/starch films

Blends of citrus pectin and high amylose starch plasticized with glycerine were investigated to determine the effect of compositional variables on film properties. Several films with representative compositions were made from sugar beet and almond pectin, and tested for comparison. The films were cast from water onto glass plates, dried, and removed. Mechanical analysis was done using a Rheometrics RSA II solids analyzer. Increasing the glycerine concentration led to decreases in static modulus, dynamic modulus, and tensile strength, but to increases in elongation. Increasing levels of starch in the blend lowered the effect of glycerine on mechanical properties. Oxygen permeability of the films was extremely low. Sugar-beet pectin and almond pectin gave films with mechanical properties comparable to those made with citrus pectin. © 1994 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Glass fiber-reinforced epoxy composites

Glass fiber-reinforced epoxy composites were prepared from the matrix resins tetraglycidyl diaminodiphenylmethane

1 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-diaminodiphenylmethane.

(TGDDM) and tetraglycidyl bis(o-toluidino)-methane

2 Systematic name: N,N,N′,N′-Tetrakis(2,3-epoxypropyl)-4,4′-bis(o-toluidino)methane.

(TGMBT) using various amines like 4,4′-diaminodiphenylmethane (DDM), 4,4′-diaminodiphenylsulfone (DDS) and diethylene triamine (DETA) as curing agents. The fabricated laminates were evaluated for their mechanical and dielectrical properties and chemical resistance. The composites prepared using an epoxy fortifier (20 phr) showed significant improvement in the mechanical properties.     

Skin and layer formation in films prepared from carbohydrates,poly(ethylene-co-acrylic acid), and polyethylene

Cornstarch, a canary dextrin, and a maltodextrin were compared in films blown from carbohydrates compounded with poly(ethylene-co-acrylic acid) (EAA), low-density polyethylene (LDPE), and aqueous ammonium hydroxide plasticizer. Dextrins or maltodextrins having dextrose equivalent values of one and greater caused dark-colored films with caramel odors, probably due to Maillard reactions. Blown films with hydrophobic skins and water sensitive cores were produced with the dextrinized carbohydrates, but not from natural cornstarch. Water sensitivity of films containing the dextrinized carbohydrate was reduced by recycling the films through the blown film die. A mechanism for development of the skins is proposed, as is a method for preparing thin semipermeable membranes. © 1993 John Wiley & Sons, Inc.

1 This article is a US Government work and, as such, is in the public domain in the United States of America.

     

Hydrolyzable‐emulsifier‐containing polymer latices as dispersants and binders for waterborne carbon black paint

Poly(styrene‐co‐butyl methacrylate) and poly(styrene‐co‐butyl acrylate) latices were prepared by emulsion polymerization with alkali‐hydrolyzable and nonhydrolyzable cationic emulsifiers and were used as a dispersant and binder for waterborne carbon black (CB) paint. CB was dispersed in the latex solutions and then coated on filter paper pretreated with dilute aqueous Na₂CO₃ under mild conditions. The styrene (St)‐rich rigid copolymer latices easily dispersed the CB but fixed a little amount of the pigment on the paper surface. In contrast, the methacrylate‐ and acrylate‐rich soft latices tended to increase the adhesibility on it. We also demonstrated that the hydrolyzable‐emulsifier‐containing latices always had a higher adhesibility than the nonhydrolyzable‐emulsifier‐containing ones. Thus, the hydrolyzable‐emulsifier‐containing latices with an appropriate St content had the highest paintability, rapid adhesion, quick drying, reduced fading, superior fastness, and so on. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3869–3873, 2013