Latex Films Research Articles

Knotty Tear Phenomena and Effect of Maturation Time on Knotty Tear in Filled Natural Rubber Latex Films

Knotty tearing is a phenomena normally observed in reinforced black-filled natural rubber (NR) vulcanizate but not in gum NR vulcanizate. Unfortunately the underlying cause of knotty tear is still not fully understood and need to be unraveled. Many factors contribute to knotty tear behavior which include suppression of strain-induce crystallization, protein content of latex, vulcanization temperature and pre-vulcanization and post-vulcanization of latex. In this study, we concentrate on varying the maturation time during compounding process in filled NR latex (NRL) to study knotty tear behavior. The maturation time were varied in the range (0 – 72) hrs; and the tear deviation were measured to determine the extent of knotty tear phenomena. It was found that at the optimum maturation time of 24 hrs samples show highest tearing energy and show knotty tear phenomena with the least angle of tear deviation.

Preparation and properties of long chain based polyacrylate latex

The long carbon chain monomer modified polyacrylate latex was successfully prepared by semi-continuous seeded emulsion polymerization. In this work, methyl methacrylate and butyl acrylate were used as main monomers; stearyl acrylate was used as functional monomer, which were emulsified with the novel mixed surfactants of disodium laureth sulfosuccinate (AEMES) and alkylphenol ethoxylates (OP-10) and initiated with 2,2′-azobis (2-methyl propion- amidine) dihydrochloride initiator. The structure of the resultant latex was characterized by Fourier transform infrared spectroscopy. The differential scanning calorimetry, thermogravimetric analysis and contact angle were used to test the properties of the latex film. The particle size of the latex was measured by the Zetatrac dynamic light scattering detector. Factors, which have an influence on the properties of the latex and its film, have been investigated in detail. Results show that the optimal condition of synthesizing the latex is as follows: the amount of emulsifiers is 4%; the mass ratio of AEMES to OP-10 is 3:1; the amount of initiator is 0.7%; the content of SA is 6%.

Stretchable Polymer Composite with a 3D Segregated Structure of PEDOT:PSS for Multifunctional Touchless Sensing.

Soft electronics with the capability of perceiving surrounding objects and acquiring information without direct touch have become increasingly important for applications in remote safety and healthcare monitoring, artificial prosthetics, and augmented reality. So far, materials that are inherently stretchable and can exhibit distinct touchless sensing capability are still scarce. Here, we report that constructing a three-dimensional (3D) segregated structure in the carboxylated styrene-butadiene latex film using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) can lead to a highly stretchable polymer composite with high sensitivity toward various touchless stimuli. Consequently, the resultant composite can be directly used for touchless sensing. Control experiments reveal that the unique 3D segregated structure is essential to achieve high-performance touchless sensing. We further show that the composite can be assembled into capacitors to precisely identify surrounding objects via capacitive proximity sensing. Moreover, an intelligent prosthetic hand is fabricated by integrating piezoresistive and capacitive sensing modes together, demonstrating that the newly developed polymer composite holds great potential for practical touchless sensing by simultaneously perceiving the location and the temperature of the target.

Influence of Varied Fluorine Contents on Long-Term Storage Stability of Polyacrylate Nanoparticles and Film Properties

Polyacrylate nanoparticles are widely applied and typically prepared by many polymerization methods. However, poor long-term storage stability of nanoparticles limited their use, so some methods are carried out to overcome it. In this paper, we investigated a series of fluorinated polyacrylate nanoparticles to improve the long-term storage stability of polyacrylate nanoparticles. We found that increasing fluorine content resists the aggregation of nanoparticles during long-term storage. Furthermore, a higher content of fluorine can improve the hydrophobicity of latex polyacrylate film and increase the refractive index of latex polyacrylate film. The properties of the polyacrylate nanoparticles and latex film can thus be controlled by changing fluorine contents, which in turn provides key insights into the design of functional polymer material.

Ultrafine calcium carbonate-filled natural rubber latex film: mechanical and post-processing properties

This study aims to improve the dispersion of treated calcium carbonate (CaCO3) in natural rubber latex (NRL) films. Ball mill and ultrasonic methods were used to break down the particle size of CaCO3, and the combined effect of ball mill/ultrasonic and ultrasonic/ball mill methods with their optimum processing times was applied to re-agglomerate and further break down the particle size of CaCO3. The particle size and dispersibility of treated CaCO3 were characterized by particle-size analysis, transmission electron microscopy (TEM), and Zeta-potential measurement. The particle-size analysis and TEM results revealed that the particle size of CaCO3 reduced down to 1.4 µm with less agglomeration using ultrasonic for 120 min and ball mill for 72 h. Zeta--potential measurement also indicated that the ultrafine-treated CaCO3 with a broad particle-size distribution was compatible with NRL particles. The treated CaCO3 loadings from 5 to 20 phr were filled in the NRL compounds. NRL/CaCO3compounds showed decrease in viscosity and cross-link density, but increase in swelling index. It was found that tensile strength, modulus at 100% elongation, elongation-at-break, swelling index, and cross-link density of the films were improved with addition of 10 phr of CaCO3. At 20 phr of filler loading, the increment rate of tensile strength of NRL/CaCO3 films was 44% after leaching, and their retention percentage was 62% after heat aging. Therefore, ultrafine CaCO3-incorporated NRL can withstand under accelerated heat-aging condition.

Film Formation of High Tg Latex Using Hydroplasticization: Explanations from NMR Relaxometry.

The film formation of acrylic latex dispersions, containing different amounts of carboxylic acid functional groups by the incorporation of methacrylic acid (MAA), was studied with GARField 1H NMR at various relative humidities (RH). Polymer particles with glass-transition temperatures in the range from 26 to 50 °C formed films at room temperature because of hydroplasticization. It was found that with an increased drying rate due to lower RH, the evaporation flux of water was limited by the latex polymer. Only in the second stage of drying this phenomenon was more obvious with increasing MAA content. 1H NMR relaxometry was used to study the change of hydrogen mobilities during film formation and hardening of the films. This showed that the drying rate itself had no impact on the hydrogen mobility in the latex films as measured via the T2 relaxation time. Hydrogen mobilities of water and the mobile polymer phase only significantly decrease after most water has evaporated. This implies that the rigidity of the polymers increases with the evaporation of water that otherwise plasticizes the polymer through hydrogen bonding with the carboxylic acid groups. This hardening of the polymer phase is essential for applications in a coating. The hydrogen mobilities were affected by the MAA concentration. Densities of mobile hydrogens increase with increasing MAA content. This is expected if the mobile protons are contained in the MAA groups. The result thus confirms the role of carboxylic acid groups in hydrogen bonding and plasticization of the copolymers. Hydrogen mobilities, however, decrease with increasing MAA content, which is hypothesized to be caused by the formation of dimers of carboxylic acid groups that still hold water. They still enable short-range polymer hydrogen mobility due to hydroplasticization but limit long-range polymer mobility due to interaction between the carboxylic acid groups.

Modification of Adhesive and Latex Properties for Starch Nanoparticle‐Based Pressure Sensitive Adhesives

AbstractStarch nanoparticle (SNP)‐based pressure sensitive adhesives (PSAs) with core‐shell particle morphology (starch nanoparticle core/acrylic polymer shell) are produced via seeded, semi‐batch emulsion polymerization at 15 wt% SNP loading (relative to total polymer weight) and 40 wt% latex solids. Crosslinker and chain transfer agent (CTA) are introduced to the acrylic shell polymer formulation at a range of concentrations according to a 32 factorial design to tailor the latex and adhesive properties of SNP‐based latexes. The crosslinker and CTA show no significant effect on polymerization kinetics, particle size, and viscosity. Latex gel content is predicted using an empirical model, which is a function of crosslinker and CTA concentration. Both the gel content and glass transition temperature strongly affect the adhesive properties (tack, peel strength, and shear strength) of the SNP‐based latex films. 3D response surfaces for the adhesive properties are constructed to facilitate the design of SNP‐based PSAs with desired properties.

Glass‐transition temperature of a polyacrylate latex film and its water whitening resistance

ABSTRACTPolyacrylate latex materials have become a hot area recently in China due to its environmental friendliness. However, the water whitening resistance of the polyacrylate latex products in the market is largely unsatisfactory, which seriously affects the appearance and performance of the latex products. In this work, the effect of glass‐transition temperature (Tg) of a polyacrylate latex film on its water whitening resistance was investigated. The light transmittance measurement showed that the higher the Tg of the latex film, the better the water whitening resistance. Atomic force microscope, surface element analysis, static water contact angle measurement, and attenuated total reflection–Fourier transform infrared were used to characterize the accumulation of the emulsifier on the surface of the latex film. It was found that the amount of emulsifier migrated to the surface of the latex film increased with the increase of the Tg of the latex film, that is, the amount of emulsifier remained inside the latex film decreased, thereby reducing its affinity to water. In addition, the higher the Tg of the latex film, the lower the water absorption, also reducing the affinity of the latex film to water. Both work together to improve the water whitening resistance of polyacrylate latex film with higher Tg. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48361.

Ecofriendly latex films from cassava starch-filled radiation pre-vulcanized natural rubber latex

ABSTRACTThe demands of the usage of hazardous ingredients for sulfur curing system in latex industries decrease with an increase in health-conscious and environmental awareness. This work demonstrates the incorporation of cassava starch (CS) as biodegradable fillers with natural rubber latex (NRL) through a sulfur-free crosslinking technique using radiation pre-vulcanization natural rubber latex (RVNRL) in comparison to sulfur pre-vulcanized natural rubber latex (PvNRL). The 20% CS dispersion was prepared, and 5–25 phr of dispersed CS content were compounded with NRL and formed into films by the coagulant dipping method. Microstructures and crystallinity of the films were analyzed by scanning electron microscopy (SEM) and X-ray diffraction, and their mechanical properties of NRL/CS films were characterized by tensile and tear tests. The result revealed that the crystallinity of RVNRL films was lower than PvNRL films. The total bond of S−C from PvNRL contributes to high tensile strength compared to C−C intermolecular rubber bond from radiation vulcanization system. The trend of decrement of tensile properties from sulfur crosslinking was larger than radiation crosslinking, and both systems gave similar tensile behavior at 25 phr of CS content. This attributed to the better dispersion of CS in RVNRL as confirmed by SEM micrographs. It was found that the optimum tear strength of RVNRL/CS and PvNRL/CS films was obtained at 10 and 5 phr of filler content, respectively. The result presented in this study may facilitate a contribution to the current literature on the development of latex film by radiation pre-vulcanization for rubber industry in the future.

Pre‐Vulcanization of Large and Small Natural Rubber Latex Particles: Film‐Forming Behavior and Mechanical Properties

AbstractThe pre‐vulcanized large rubber particle (LRP) and small rubber particle (SRP) latices are independently prepared to investigate their film‐forming process and mechanical properties after being cast into films. The surface morphologies and roughness of both LRP and SRP films are found to be dependent on crosslink densities. The networks inside each rubber particle (RP) restrict particle deformation resulting in residual contour of RP within the film surface. For highly crosslinked RP, the collapse of the top surface of the RPs in the LRP films appears to create many “crater‐like” structures within the film surfaces, while they present only protruding particles within the SRP and blend films. This seems to indicate that LRPs are easier to coalesce and form film than SRPs. Additionally, dynamic and mechanical properties and strain‐induced crystallization (SIC) behaviors of the latex films, are effectively enhanced after pre‐vulcanization. The pre‐vulcanized LRP films perform better tensile properties and SIC than the SRP can.

Waterborne acrylic-melamine latexes with controlled film microstructure

Crosslinkable latexes aim to improve the physical properties of coalesced latex films, over levels attainable with thermoplastic latexes, which lack thermal, mechanical and solvent resistance. This work investigated the synthesis by miniemulsion polymerization of waterborne acrylic-melamine nanocomposites with the aim of obtaining high solid-content latexes (50%) with controlled crosslinkable capability. Changes in both the acrylic polymer microstructure (i.e., content of hydroxyl groups and molecular weight) and the amount of melamine (a commercial iso-butylated melamine-formaldehyde resin) showed a significant influence on the crosslinking degree, and consequently on the final properties of cured films at high temperature. It was observed that reducing molecular weight of acrylic polymer allowed a good chain inter-diffusion during the course of film preparation, increasing crosslinking occurrence. Also, the content of hydroxyl groups and melamine could promote the enhancement of final film properties.

BIO-CACO3 FROM RAW EGGSHELL AS ADDITIVE IN NATURAL RUBBER LATEX GLOVE FILMS

ABSTRACT Raw hen eggshell powder, a calcium carbonate source, was used as a biofiller in the natural rubber latex compound and latex glove film formation via dipping process. The powder was anticipated to improve the physical (smoothness and thickness of film) and mechanical properties (tensile strength and elongation at break) of latex film and to reduce the extractable protein content on film surface. Eggshell powder ground by a rapid mill was fine particles of approximately 37.48 μm in diameter, suitable for homogeneous and compatible addition into the natural rubber latex compound. Dipping hand mold into the natural rubber latex compound with 50 wt% eggshell added was the best formula to obtain a smooth, clear, thin film surface, with the tensile strength of 23.24 ± 0.745 MPa and the highest elongation at break of 723.99 ± 14.60%, along with a low protein content, a dense film without water leakage, and with a good contact angle. The natural rubber latex glove film possessed good physical-mechanical properties and a low protein content as the results of the raw eggshell powder added as a biofiller.

THE Effect of Azido-Starch as Filler on Tensile and Tear Properties of Natural Rubber Latex Films

The azido starch/Natural Rubber (azo-starch/NR) latex films were prepared with control (0), 0.5, 1.0, 1.5 and 2.0 phr of azido-starch loadings. The azido starch functional groups were characterized by Fourier Transform Infra- Red (FTIR) analysis to observe the presence of significant peaks of azide (N3).The control and azido starch-filled NR films were subjected to tensile test and tear test in order to investigate the effect of the addition of azido-starch on the mechanical properties of azo-starch/NR latex films. The tensile strength of azo-starch/NR latex films was increased with increasing azido-starch loading and slightly decreased after 1.0 phr loading. The optimum tensile strength of azo-starch/NR latex films is obtained at 1.0 phr loading. The moduli (M100 and M300) and tear strength also increased with increasing azido-starch loading. However, the elongation at break (EB) was almost similar with increasing azido-starch loading. The swelling test was done to determine the swelling index, crosslink density and rubber-filler interaction of azo-starch/NR films. The swelling index was decreased but the crosslink density increased with increasing azido-starch loading indicating the formation of crosslinks between azido-starch and rubber macromolecules.

The potential use of immobilized Bacillus cereus ATCC 14579 for biodegradation of natural rubber latex film added with Metroxylon Sagu pith form

The previous study reported that Bacillus cereus ATCC 14579 able to degrade natural rubber latex films added with Metroxylon Sagu pith waste form (MSPW/NR) and natural rubber (NR) latex films as main source of carbon and energy. Some attempts have been made to degrade them in the newly batch systems rather than disposing of them in landfill. Immobilization technique was performed to adsorb Bacillus cereus onto modified activated carbon. This work aims to study the potential of immobilized Bacillus cereus for biodegradation of MSPW/NR. The results revealed that 30% nitric acid for 2 hours impregnation time showed significant influence on Bacillus cereus adsorption. The highest adsorption capacity of Bacillus cereus was found to be 72.8% under its optimum conditions. The weight loss of MSPW/NR by 12.843 % were obtained after 14th days biodegradation period. Thus, immobilization of Bacillus cereus ATCC 14579 has potency to provide a biotechnological solution to the waste rubber and latex disposal problem.

Radiation dose required for the vulcanization of natural rubber latex via hybrid gamma radiation and peroxide vulcanizations

To enhance the crosslinking of prevulcanized natural rubber latex, combination of Irradiation and peroxide vulcanizations were used. Through this method, hexanediol diacrylate (HDDA) from irradiation vulcanization acted as the main sensitizer, while cumene hydroperoxide (CHPO) from peroxide vulcanization would act as the co-sensitizer. The effects of irradiation doses on the mechanical properties of latex film were investigated. 16 kGy irradiation dose, 2.5 parts perhundred rubber (pphr) of HDDA, 0.1 pphr of CHPO and 2.5 phr of Aquanox LP antioxidant were found to be the optimum conditions for compounding formulation. The rubber film obtained had tensile strength, modulus at 500% and modulus at 700% of 27.7, 3.5 and 12.4 MPa respectively, which is more than 21% increment compared to control film. Besides, the crosslink percentage of the rubber film showed 7 % increment from 90.7% to 97.7%.

Divinyl‐terminated polysiloxane as an effective polyacrylates modifier for pigment printing: A study with different molecular weights and quantities

ABSTRACTPolyacrylates binder is used as an environmental approach for pigment printing. However, the poor water resistance and abrasive resistance of it makes this technique limited. In this study, divinyl‐terminated polysiloxane (Divi‐PDMS) had been used to modify polyacrylates by miniemulsion polymerization. The conversion and coagulation of miniemulsion polymerization were evaluated by gravimetry method, the colloid properties of prepared latexes were obtained and the structures were confirmed by Fourier transformed infrared spectroscopy and NMR. Surface properties of latex films were investigated in terms of dynamic water contact angle, water absorption, and mechanical tensile properties. The results show that the polymerization has good stability, and the product has good phase separation of polysiloxane, which results in increased hydrophobicity and toughness of the film. The film with low‐molecular weight and 8% dosage of Divi‐PDMS has better hydrophobicity and toughness. The product is applied to pigment printing with better wet rubbing fastness and soft handle compared with the unmodified binder. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47961.

A low-voltage graphene/Ag-based phase transition-controlled force actuator

A phase transition-controlled force actuator based on graphene/Ag/SR (silicone rubber) has been designed and fabricated. This actuator is based on the principles of phase transition. The actuator with an enclosed cavity, which consisted of a latex film and a graphene/Ag/SR-based electrothermal substrate, and then injecting ethanol into the cavity. The actuator can operate at a low voltage (6 V), and the magnitude of the feedback force can be controlled by applying a square wave signal which the duty cycle is adjustable. The minimal change in feedback force is 0.02 N. Owing to its simple fabrication, easy operation, lightweight (1.4 g), low driving voltage, large deformation and controllable force, manipulator, auto-injector and bionic fish have been made. Summarizing aforementioned experimental results, the manipulator can grip objects of different weights, and the auto-injector can inject a liquid and act as an injector. Furthermore, bionic fish can float and sink in the water. These devices showing that the phase transition actuator is expected to be widely used in soft robots, bionic devices design, and medical field. Also, this category of phase transition actuator could provide ideas for developing flexible actuator.

Room-Temperature Synthesis of Size-Uniform Polystyrene Latex and Characterization of Its Properties: Third-Year Undergraduate Teaching Lab

Teaching emulsion polymerization is an important benchmark in undergraduate polymer courses. However, the introduction of hands-on experiments in undergraduate polymer laboratories is challenging: experimental time, reagents, and equipment involved are the primary restraints. We report a practical emulsion polymerization laboratory experiment for undergraduate students that includes the synthesis of polystyrene (PS) latex and exposure to multiple methods of characterization. Using a room-temperature redox initiation system of ascorbic acid (vitamin C) and hydrogen peroxide, and scaling the reaction down to ca. 10 mL, simplifies stirring and degassing and alleviates the aforementioned challenges. To prepare latex samples with different sizes and low size dispersity, students explore an effect of a steric stabilizer (polyvinylpyrrolidone, PVP). For effective time management, students perform characterization of previously prepared latex, while qualitatively and quantitatively monitoring particle growth during polymerization stages. Latex characterization performed by students includes measurements of average particle size and zeta potential, estimating conversion and preparation of latex films with determination of glass transition temperature (Tg). Other characterization methods that can be incorporated in the extended experiments include electron microscopy, atomic force microscopy, and other techniques of colloidal and polymer characterization. Additionally, the prepared latex is able to form colloidal photonic crystal films, enabling size evaluation by color or UV–vis measurements, where selective reflection of blue, green, and red corresponds to latex with particle diameters of 185, 240, and 300 nm, respectively. On the basis of the lab evaluation survey, students performing the experiment have an overall positive learning experience with 94% satisfaction rate.

Synthesis and Characterization of Novel Poly (VAC-VeoVa-HFMA-BZMA) Latex via Semicontinuous Seeded Emulsion Polymerization

The novel poly (VAC-VeoVa-HFMA-BZMA) latex was successfully prepared via semicontinuous seeded emulsion polymerization which vinyl acetate (VAc) and vinyl ester of neodecanoic acid (VeoVa10) were main monomer, hexafluorobutyl methacrylate (HFMA) and benzyl methacrylate (BZMA) were used as functional monomer. Dodecyl benzene sulfonic acid sodium (SDBS), octylphenol polyoxyethylene ether (OP-10) and potassium persulfate (KPS) were used to be mixed emulsifier and initiator, respectively. The structure of the resultant latex is determined by Fourier transform infrared spectroscopy spectrum (FTIR). The thermal performances of latex film are studied via the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The average particle size of the latex is characterized by the dynamic light scattering(DLS).Water contact angle (WCA) is used to test the wetting property of the novel poly (VAC-VeoVa-HFMA-BZMA) latex film. The condition of synthesizing the latex was studied in detail. The optimum condition of preparing the novel latex is that the amount of emulsifier is 8.0% (wt %) and the mass ratio of SDBS to OP-10 is 2 : 1 and the mass ratio of main monomer VAc to VeoVa10 is 3 : 1. The amount of initiator is 0.8% and the amounts of HFMA and BZMA are 6.0 and 8.0% (wt %), respectively. Results indicate that the water resistance of the latex film and thermal stability are improved when the fluorine and BZMA monomers are added.

Plant oil-derived copolymers with remarkable post-polymerization induced mechanical enhancement for high performance coating applications

Polymer coatings have been heavily utilized in many industrial and civil applications where a protective thermoset material with enhanced properties such as chemical and physical resistance, thermal stability, and tailorable mechanical properties is desired. Plant oils are a class of promising biomass toward sustainable polymers, but have yet to be fully harnessed in tailorable thermoset coatings due to the challenging functionalization and extensive crosslinking processes required to achieve desirable thermomechanical properties. In this work, we demonstrated that soybean methacrylate (SBMA) from high oleic soybean oil (HOSO) can be utilized to produce bio-based acrylic thermoset copolymers through an industrially viable semi-batch emulsion polymerization process with various commonly used co-monomers such as methyl methacrylate, styrene, and butyl acrylate. A wide range of monomer feed ratios with SBMA from 0 to 50 wt% was easily achieved with minimal modifications allowing for good tunability of thermal and mechanical properties in the prepared latexes. More importantly, a simple and effective auto-oxidative crosslinking of the latex films provided extreme mechanical enhancements making these thermosets good candidates in ultra-strong, ultra-tough, and high Tg coating applications.