Viscosity Of Latex Research Articles

Analysis of reduced and oxidized antioxidants in Hevea brasiliensis latex reveals new insights into the regulation of antioxidants in response to harvesting stress and tapping panel dryness

Latex diagnosis (LD) is applied to optimize the natural rubber production and prevent tapping panel dryness (TPD), a physiological syndrome affecting latex production in Hevea brasiliensis. The reduced thiol content (RSH) is one of the biochemical parameters associated with the risk of TPD. However, RSH is difficult to interpret because of the influence of the environment. In order to better understand the regulation of antioxidants and to better interpret RSH, a key parameter of LD, this study analysed in latex both oxidised and reduced forms of ascorbic acid (AsA) and glutathione, and their cofactors as well as other latex diagnosis parameters in response to harvesting stress (tapping and ethephon stimulation) and TPD occurrence. The content of antioxidants in latex had a high variability among five rubber clones. The concentration in AsA was about ten times higher than GSH in laticifer, GSH accounting for about 50% of RSH. For short-term harvesting stress, RSH increased with tapping frequency and ethephon stimulation. TPD is associated with high latex viscosity and bursting of lysosomal particles called lutoids, as well as for several rubber clones with lower RSH and GSH contents. These results suggest that a high level of RSH shows the capacity of laticifer metabolism to cope with harvesting stress, while a drop in RSH is the sign of long stress related to lower metabolic activity and TPD occurrence. RSH remains an essential physiological parameter to prevent TPD when associated with reference data under low and high harvesting stress. This study paves the way to understand the role of AsA and GSH, and carry out genetic studies of antioxidants.

Experimental assessments of methanol-based foaming agent in latex modified foamed binders and warm asphalt mixtures

Latex is one of the natural rubbers that is used to enhance the performance of asphalt pavement for the last few decades. The presence of latex, which is categorized as an elastomer, helps to improve pavement performance and durability. Conversely, higher viscosity of latex modified asphalt binder increases the production-temperatures of asphalt mixture, thus consuming higher energy during asphalt mixture’s production stage. In this study, the effectiveness of methanol as an energy-efficient foaming agent was assessed to reduce the viscosity and enhance the workability of the modified asphalt binder. The basic and rheological properties of the asphalt binders were determined through multiple laboratory tests including expansion ratio and half-life, rotational viscosity, softening point, torsional recovery, and dynamic shear rheometer. The properties of asphalt mixtures were assessed through the service characteristics, mechanical performance, and moisture resistance criteria. It was found that the presence of latex results in an approximately twofold higher expansion ratio and a lower half-life of the asphalt binder at about the same ratio. Through the rotational viscosity test, the application of methanol into asphalt binder decreased the viscosity and led to better workability, despite the addition of latex as an asphalt modifier. The application of methanol into asphalt binder improved the workability of mixture samples and lowered the compaction energy of the compaction process, which are the crucial criteria for a better mixing and compaction process. Methanol foamed asphalt mixtures with latex show much higher resistance to moisture damage and stiffness than control sample even though they were prepared at a lower temperature.

The use of lignin in emulsion-based pressure-sensitive adhesives

Pressure sensitive adhesive (PSA) films were produced by in situ seeded semi-batch emulsion polymerization of butyl acrylate (BA) and methyl methacrylate (MMA) in the presence of varying amounts of lignin. Two types of Kraft lignin, water-soluble and non-water soluble, were used in this study. Lignin was modified using acrylation (methacryloyl chloride), maleation (maleic anhydride) and acetylation (acetyl bromide and acetic acid) to promote its miscibility with the BA and MMA monomers and encourage its incorporation into the polymer matrix. For the case of the maleated lignin, maximum incorporation of 10 wt% was achieved whereas, for the acrylated lignin case, a maximum of 5 wt% was attained. Lignin was shown to decrease latex viscosity in all cases. At a lignin loading of 1 wt% (relative to the amount of monomer) a tack and shear strength of the PSA films increased significantly while the peel strength remained constant. Thus, maleated lignin was shown to be an effective, renewable modifier for emulsion-based PSA properties.

Synthesis of poly(isobutyl acrylate/n‐butyl acrylate/methyl methacrylate)/CNC nanocomposites for adhesive applications via in situ semi‐batch emulsion polymerization

Pressure sensitive adhesive (PSA) films were prepared from in situ semi‐batch emulsion polymerizations using isobutyl acrylate, n‐butyl acrylate, and methyl methacrylate in the presence of cellulose nanocrystals (CNCs). The CNCs at loadings of up to 1 wt% with respect to monomer resulted in significant and simultaneous improvement in tack, peel strength and shear strength for the PSA films. While most latex properties were unchanged, the CNCs also led to increased latex viscosity. A range of compositions were used to test the limits of the application. Microscopy was used to demonstrate that the CNCs were dispersed throughout the latex but outside of the polymer particles. Comparison to latex/CNC blends showed that the in situ technique provided higher shear strength PSA films. POLYM. COMPOS., 40:1365–1377, 2019. © 2018 Society of Plastics Engineers

Synthesis of polymer hybrid latex poly(methyl methacrylate-co-butyl acrylate) with organo montmorillonite via miniemulsion polymerization method for barrier paper

Hybrid polymer latex based on combination of organic-inorganic materials, poly(methyl methacrylate-co-butyl acrylate) (PMMBA) and organo-montmorillonite (OMMT) were synthesized via miniemulsion polymerization technique. Modification of montmorillonite (MMT) through the incorporation of myristyltrimethylammonium bromide (MTAB) into the clay’s interlayer spaces were investigated by Small-Angle X-ray Scattering (SAXS), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric Analysis (TGA) and Transmission Electron Microscopy (TEM). Barrier property and thermal stability of polymer latex film sample were investigated through its Water Vapor Transmission Rate (WVTR) and Thermogravimetric Analysis (TGA). The results indicated that addition of OMMT as filler in PMMBA increased the barrier property and thermal stability of the latex film. Addition of 8.0% (wt) OMMT increased the barrier property and thermal stability. Miniemusion polymerization process with higher addition (>8.0 wt%) of OMMT resulting in high latex viscosity, particle size, and high amount of coagulum. The utilization of this hybrid polymer could benefits paper and board industries to produce high quality barrier paper for food packaging.

EFFECT OF FURFURAL ON THE PROPERTIES OF NATURAL LATEX: POSSIBILITY FOR ADHESIVE APPLICATION

ABSTRACT Normally, the properties of natural latex are not stable, for example, viscosity and volatile fatty acids, due to the nonrubber components that affect the quality of the latex. The objective here was to develop and compare the adhesive properties of natural latex by using furfural at different ratios. Concentrated natural latex (60% rubber) with a high ammonia rate was used, and two types of furfural were used: synthetic furfural and natural furfural from sugarcane bagasse. The phenolic resin was also compared as a tackifier resin. We found that increasing the furfural concentration in natural latex increased the viscosity of the latex. However, for a given concentration, furfural and phenolic resin gave similar adhesion properties in natural latex. Furfural at 10 parts per hundred of rubber gave the best adhesive property of natural latex. Beyond this furfural concentration, the natural latex became solid. There were no significance differences in adhesion properties between synthetic and natural furfurals in the natural latex. The relationship between viscosity and adhesive properties of the natural latex with furfural is proposed. This research shows the potential to develop an eco-friendly natural adhesive with furfural that has good quality and no dangerous solvent.

Synthesis of Poly(n‐butyl acrylate/methyl methacrylate)/CNC Latex Nanocomposites via In Situ Emulsion Polymerization

AbstractCellulose nanocrystals (CNCs) are renewable, nontoxic and naturally available organic nanoparticles derived from cellulosic resources such as cotton and wood pulp. Poly(n‐butyl acrylate‐co‐methyl methacrylate)/CNC latexes are successfully synthesized via in situ emulsion polymerization. The effect of CNC loading on overall conversion, polymer particle size, glass transition temperature (Tg), gel content, latex viscosity, and storage and loss moduli of dried latex are studied. While the effect of CNC content on overall conversion, polymer particle size, and Tg of the resulting latexes is negligible, significant increase in gel content, latex viscosity, and storage and loss moduli are observed. image

Degree of Vulcanization of Rubber Latex by Capillary Viscometer

The degree of vulcanization of latex compound was determined by capillary viscometer with controlled temperature to study effect of time and temperature on vulcanization process. The standard equilibrium swelling test was also conducted to assess the degree of vulcanization. A latex compound for medical glove was investigated. The latex viscosity was observed to increase over time at above room temperature condition. On the other hand, the viscosity fluctuated around mean value at room temperature. This is partly consistent with the swell ratio measurement which complete vulcanization was observed at curing temperature of 60 °C.

Conjugated Linoleic Acid/Styrene/Butyl Acrylate Bulk and Emulsion Polymerization for Adhesive Applications

SummaryThe incorporation of conjugated linoleic acid (CLA) into pressure sensitive adhesive (PSA) formulations was evaluated. First, a series of free radical bulk copolymerizations of CLA/styrene (Sty) and CLA/butyl acrylate (BA) were run for reactivity ratio estimation. This was followed by CLA/Sty/BA bulk terpolymerizations. Pseudo‐kinetic models were developed and validated with the copolymerization data and extended and validated for the CLA/Sty/BA terpolymerization case. The pseudo‐kinetic models incorporated the electron trapping effect of oleic acid, a common impurity found in CLA. A series of emulsion terpolymerizations of CLA/Sty/BA were then designed to investigate the influence of terpolymer composition, molecular weight, chain transfer agent concentration, cross‐linker concentration, latex viscosity and particle size on PSA performance (tack, peel strength and shear strength). Empirical PSA performance models were developed and expressed as 3D response surfaces for optimization of the PSA formulation. All experiments were performed at 80°C and monitored with attenuated total reflectance Fourier transform infrared (ATR‐FTIR) spectroscopy both off‐line (bulk experiments) and in‐line (emulsion experiments). Ultimately, the incorporation of 30 wt.% CLA into a practical PSA application suitable for removable adhesives was achieved.

Effect of N,N-dimethylacrylamide (DMA) on the comprehensive properties of acrylic latex pressure sensitive adhesives

Acrylic pressure sensitive adhesive (PSA) latexes were synthesized via a monomer-starved seeded semi-continuous emulsion polymerization process with butyl acrylate (BA), methyl methacrylate (MMA), N,N-dimethylacrylamide (DMA), acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA) as monomers. Impacts of DMA on the resultant latex and PSA properties were comprehensively investigated. Results indicated that latex particle size was independent of the amount of DMA in the pre-emulsion feed with excessive and constant surfactant concentration. Latex viscosity increased with DMA concentration. It was also found that water resistance of acrylic latex PSA became worse by the presence of DMA, confirmed by water contact angle measurements. Besides, DSC results showed that as the amount of DMA increased, glass transition temperatures (Tg) of the polymers were elevated significantly. TGA results showed that thermal stability of PSA was improved with DMA as a co-monomer. Furthermore, as DMA amount increased, gel content slightly increased, while sol molecular weight (Mw, Mn) of the polymer decreased. Finally, with respect to the adhesive properties of the PSA, it was observed that loop tack initially increased and then decreased with the addition of DMA from 0 to 4wt%, and the maximum value appeared at 1wt%. Peel strength reduced, while shear strength improved with increased DMA concentration.

Influences of maleic reactive surfactants with different EO chain lengths on the properties of the acrylate latices

Three maleic reactive surfactants with different oxyethylene (EO) units (5, 9 and 15) were synthesized and used to prepare the soap-free acrylate latices with methyl methacrylate, butyl acrylate, and hydroxypropyl acrylate as monomers through the polymerization of pre-emulsifying seed emulsion and semi-continuous dropping process. Effects of EO chain lengths on the properties of the latices and their films were investigated. The results showed the polymerization using maleic reactive surfactant with 9 EO units could achieve the highest monomer conversion and the copolymers with highest M w were obtained. The viscosity of latices decreased and their chemical stabilities and particle sizes increased with the increase of EO chain lengths. The EO chain lengths slightly influenced the pencil hardness and adhesion of the latex films, but the shorter the EO chain lengths were, the better were these properties. The amount of maleic reactive surfactants had effects on the properties of the acrylate latices as well. In addition, the results from TEM showed that the latex particles were irregular and there were some “caves” in the particles. It was considered that the particles were formed due to the coil and entanglement of the growing polymer chains in the aqueous phase.

Preparation of starch-based styrene acrylate emulsion used as surface-treatment agent for decorative base paper

Abstract A series of cationic starch (CS-8)-based styrene (St) acrylate latex preparations was prepared by the core-shell emulsion polymerization method. The latex was used in the surface-treatment of decorative base papers, for good printability and absorbability. CS-8, which has a low relative viscosity, was used as the emulsifier and dispersant. The influencing factors (dosage of CS-8 as well as the kinds and dosages of functional monomers) were studied and the optimal conditions were achieved. Then, the products were characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR), laser particle size analysis and particle charge detection. The results showed that the excellent performance and good surface-treatment effects of the St acrylate emulsion (SAE) were achieved when the reaction conditions were as follows: 10 wt% starch, 2 wt% methacryloyloxyethyltrimethyl ammonium chloride (DMC) as the cationic monomer and 20 wt% ethyl acrylate (EA) as the acrylate monomer. Under the optimal conditions, the latex particle size was around 160 nm, the latex viscosity was 10 mPa·s and the latex charge density was 0.60 mmol·l-1. The printability of the decorative base paper was significantly improved and the absorbability of the paper sheet was maintained. The surface-treatment effect of the cationic starch-based SAE was superior to that of commercial polyurethane (PU).

Evaluation of Apparent Viscosity of Para Rubber Latex by Diffuse Reflection Near-Infrared Spectroscopy

Near-infrared spectroscopy in diffuse reflection mode was used to evaluate the apparent viscosity of Para rubber field latex and concentrated latex over the wavelength range of 1100 to 2500 nm, using partial least square regression (PLSR). The model with ten principal components (PCs) developed using the raw spectra accurately predicted the apparent viscosity with correlation coefficient (r), standard error of prediction (SEP), and bias of 0.974, 8.6 cP, and -0.4 cP, respectively. The ratio of the SEP to the standard deviation (RPD) and the ratio of the SEP to the range (RER) for the prediction were 4.4 and 16.7, respectively. Therefore, the model can be used for measurement of the apparent viscosity of field latex and concentrated latex in quality assurance and process control in the factory.

16S rRNA gene sequences analysis of Ficus elastica rubber latex degrading thermophilic Bacillus strain ASU7 isolated from Egypt

A thermophilic Bacillus strain ASU7 was isolated from soil sample collected from Assiut governorate in Upper Egypt on latex rubber-containing medium at 45°C. Genetically, the 16S bacterial ribosomal RNA gene of the strain ASU7 was amplified by the polymerase chain reaction (PCR) and sequenced. The sequence of the PCR product was compared with known 16S rRNA gene sequences in the GenBank database. Based on phylogenetic analyses, strain ASU7 was identified as Bacillus amyloliquefaciens. The strain was able to utilize Ficus elastica rubber latex as a sole source for carbon and energy. The ability for degradation was determined by measuring the increase in protein content of bacterium (mg/g dry wt), reduction in molecular weight (g/mol), and inherent viscosity (dl/g) of the latex. Moreover, the degradation was also confirmed by observing the growth of bacterium and formation of aldehyde or keto group using scanning electron microscopy (SEM) and shiff's reagent, respectively.

Nanometre fluorinated acrylate latex prepared with gemini surfactant

The nanometre fluorinated acrylate latex was prepared via semi-continuous seeded emulsion polymerisation of butyl acrylate, methyl methacrylate and hexafluorobutyl acrylate in water phase when gemini surfactant and 2,2′-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride are used to be emulsifier and initiator, respectively. The resultant latex is characterised by Fourier transform infrared (FTIR) spectrometry, contact angle measurements, dynamic light scattering and differential scanning calorimetry (DSC). FTIR spectrum identifies the formation of terpolymer. DSC confirms that the latex is a kind of random terpolymer and the consistency among the chain segment is fairly good. The average particle size of latex is decreased with the increase of the amount of gemini surfactant. The particle size of resultant latex is 22.4 nm and is further confirmed by transmission electron microscope when the amount of gemini surfactant is 3%. However, the viscosity of latex is increased with the increase of the amount of gemini surfactant. In comparison with the nanometre fluorinated acrylate latex, the hydrophobic property of the resultant latex is improved.

Influence of the Hydrophile-Lipophile Property of Cross-Linker on the Properties of Acrylate Latex and its Film

A series of acrylate latexes for pigment printing binder were prepared by semi-continuous pre-emulsifying emulsion polymerization, using lipophilic glycidyl meth-acrylate (GMA), ethylene glycol dimethyl acrylate (EGDMA) and hydrophilic HA (containing hydroxyl, acylamino), N-methylol acrylamide (NMA) as cross-linking monomer. The influences of cross-linker type on the particle size, viscosity and film-forming rate of latex, cross-linking degree and tensile properties of latex film were studied. It was found that the latex particle size, viscosity and film-forming rate were closely related with the hydrophile-lipophile property of cross linkers. The acrylate latex synthesized with hydrophilic cross-linkers always exhibits the characteristics of larger particle size, lower film-forming rate, higher viscosity and pseudoplastic fluid. The cross-linking degree and tensile properties of latex film generally depend on the crosslinking groups of cross-linkers and their reactivity.

Synthesis and Characterization of Core-shell Acrylic/polyurethane Emulsion with Unsaturated Macromolecule Monomer Method

Acrylic/polyurethane(PUA) hybrid emulsion has been prepared by water-borne polyurethane(WPU) modified with acrylic resin.A method for adding different mass fraction of acrylic(AC) into polyurethane(PU) polymers is proposed and verified through designed experiments.With increasing the polyacrylate(PA) mass fraction in the copolymer,the appearance of the emulsion changes from transparent to opacity,in the meantime,the particle size is increased.The TEM result reveals that PUA latex particles present clear core-shell structure and regular shape,and the size distribution is within the range of 60~120 nm.The results of FTIR indicate that the hydrogen bonding effect of PU hard segment first increased and then decreased,while the ordering of hard segment decreased with increasing the AC mass fraction.Compatibility and degree of mixing were developed under 75%AC added in copolymers.With increasing PA mass fraction,one glass transition temperature existed in the copolymers before the content of AC arrived 75%.Thermogravimetric analysis(TGA) shows that the temperatures for the maximal thermal mass-loss rate rose from 363 ℃ to 412 ℃,and water absorption for samples decreased from 11.3% to 5.7% with the increase of AC fraction.Additionally,the elasticity modulus of PUA was raised from 16.4 to 47.6 MPa,while the tensile strength was increased from 9.0 to 23.7 MPa,and the elongation at break changed from 365% to 408%.Furthermore,the composite latex viscosity is decresed,and the drying time is shortened,while glue film adhesion force becomes better.

PVAc Microspheres via Semicontinuous Emulsion Polymerization: Synthesis, Characterization, Kinetic, and Surface Morphology Studies

Poly (vinyl acetate) (PVAc) latexes are economically important products with many desirable features. They are used as adhesives for porous materials in various processing stages of industries. Synthesis parameters have an important role on the physico-chemical properties of PVAc latexes such as: viscosity, average molecular weight, degree of polymerization, and surface morphology. In this work, PVAc was prepared via semicontinous emulsion polymerization (delayed monomer and initiator addition process) in the presence of ammonium persulfate (APS) as conventional anionic initiator, poly (vinyl alcohol) (PVA) as stabilizer, and sodium lauryl sulfate (SLS) as anionic emulsifier. The surface morphology of PVAc microspheres was, examined using a scanning electron microscope (SEM) and atomic force microscope (AFM). It is evident from the SEM photographs that all the particles became microspheres and are uniform in shape. The use of AFM for imaging of polyvinyl acetate confirms a typical sphere polymer. The effect of changes in the different parameters such as concentration of emulsifier, initiator concentration, and presence or absence of buffer on the vinyl acetate (VAc) conversion, the steady state polymerization rate, the viscosity-average molecular weight, and the final latex viscosity of synthesized PVAc were investigated. The effects of anionic emulsifier on the synthesized PVAc are also compared with those obtained by the nonionic emulsifier. The comparison indicated that the VAc monomer conversion and the final latex viscosity of the anionic system were higher than for the nonionic system but the viscosity-average polymer molecular weight of the anionic system was lower than that of the nonionic system. The adhesive strength of the synthesized PVAc latex was examined and the load and deflection data were reported.

Rheological Behaviour of Layered Silicate–Natural Rubber Latex Nanocomposites

The rheological behaviour of prevulcanised natural rubber (NR) latex nanocomposites based on layered silicates such as sodium bentonite and sodium fluorohectorite was studied. A typical commercial clay (non-layered version) was chosen as the reference. The effect of layered silicates on flow properties was analysed by investigating latex viscosity as a function of shear rate, temperature, and filler loading. In the presence of layered silicates, latex compounds show enhanced viscosity, probably owing to a network formation of silicate layers in the latex phase. The shear thinning behaviour exhibited by the nanocomposites at high temperature may be due to the network breakdown of silicate layers. Latex–layered silicate systems show pseudoplastic behaviour and increased zero shear viscosity and yield stress.

Effects of Disturbing Parameters on the Stability of Latex and Resorcinol Formaldehyde Latex Based Adhesives

Synthetic cords may be coated with resorcinol formaldehyde latex (RFL)-based adhesives to adhere the cord to the rubber in industrial goods such as tires and conveyor belts. The stability of the adhesive and the stability of its component latex are crucial, both for ideal adhesion and for the homogeneity of the cord surface. Latex is a colloidal polymeric dispersion, which may lose its stability upon mechanical stress or upon interaction with some chemicals that lead to the formation of coagulated polymeric particles. This article reports on the influences of both external mechanical stresses and chemical interactions on RFL adhesives and latex stability, adhesion, and viscosity. High speed mixing, treatment with excess RF, and temperature variations were applied as disrupting parameters.