Properties Of Latex Research Articles

Thermal, mechanical, and electrical properties of rubber latex with TiO2 nanoparticles

Due to the accumulation of the generated heat, the electrical wire insulator is melt and causes the fire. To decrease the accumulated heat, therefore, the heat transfer enhancement from the electrical wire insulator can be achieved by increasing the thermal conductivity of the electrical wire insulator. However, the electrical resistivity and mechanical properties are optimized too. In this study, the effects of nanoparticles content of 0, 0.1–1.0, 10, and 20 phr on the thermal, electrical, and mechanical properties of the natural rubber are presented. It can be found that the TiO2 nanoparticles have a significant effect on the increasing thermal conductivity while the electrical resistivity tends to decrease with increasing nanoparticle content. However, the tensile stress of the rubber compound tends to increase. The results obtained from this study disclose different properties that influence the strength, thermal and electrical resistance of latex rubber based composites reinforced by surface unmodified and modified nanoparticles, which is helpful not only for the understanding of performance of nanoparticle-reinforced flexible elastomer composites, but also for the design of novel flexible composites with matching strength and thermal and electrical resistance.

Fabrication of fluorescent polymer latexes based on rhodamine B derivatives and their reusable films for Fe3+ detection

The stimulus-responsive P(MMA-co-BA-co-RhBUEA) latexes were prepared by miniemulsion polymerization of butyl acrylate (BA), methyl methacrylate (MMA), and a rhodamine-based probe RhBUEA. Their chemical composition and structures were characterized by FTIR and UV–Vis spectral analysis. Meanwhile, the effects of AIBN, SDS, and RhBUEA content on the miniemulsion polymerization and the morphology of latex particles were investigated. Based on the recipe of 30 mM SDS to the volume of water, 2 wt% AIBN and 5 wt% RhBUEA to the total monomers, the sensing properties of the resultant latex and its film were studied. Both the latex and the latex film displayed the noticeable color change, high sensitivity, superior selectivity, and anti-interference properties towards Fe3+ over other metal ions in aqueous solution. The detection limits of the latex and the latex film were 0.122 and 0.208 μM, respectively. Furthermore, the film sensor exhibited good recyclability thanks to the off-on switch, possessing the potential as a portable and reversible chemosensor for the naked-eye detection of Fe3+.

Application of diluted methanol to allow the production of latex modified asphalt mixture with lower energy consumption

The modification of asphalt mixtures using latex has gained popularity in the asphalt industry as it improves the durability of road pavement. However, the elastomeric properties of latex stiffen the binder, resulting in more energy consumption during the asphalt mixture production. It would consequently cause a higher emission of greenhouse gases, which is undesirable for the human health and environment. This study aims to assess the applicability of diluted methanol as a foaming agent in asphalt mixture incorporating latex produced at a lower temperature. In this study, two designated amounts of diluted methanol (1% and 3% of the weight of asphalt binder) were successively injected with 6% latex into pre-heated asphalt binder at 135 °C in the preparation of foamed binders, while the control and latex modified asphalt mixtures were prepared at 160 °C. Tests of rotational viscosity, expansion rate, and torsional recovery were conducted to study the rheological properties of the mixtures. Service characteristics were evaluated through the indices of workability, compaction energy, and coatability. Moreover, mixture performance tests were carried out to identify the tolerance of the mixtures towards moisture damage, shear force, and permanent deformation. Through the rotational viscosity test, diluted methanol was found to reduce the viscosity of the asphalt binders, which is vital in the production processes at intermediate temperatures. The enhancement in viscosity using 3% diluted methanol had facilitated in higher workability, lower compaction energy, and better aggregate coating, which are the crucial criteria for a better mixing and compaction process. Whereby, a superior foaming quality was exhibited from the 3% diluted methanol application through the assessments of expansion ratio, half-life and foaming index. The moisture and shear resistances of the diluted methanol foamed asphalt mixtures are comparable to the control mixtures even though they were prepared at a lower temperature. Finally, the 3% diluted methanol foamed asphalt mixture promoted a better rutting resistance due to its ability to recover to the initial form which was demonstrated through its torsional recovery.

Aging and Rheological Properties of Latex and Crumb Rubber Modified Bitumen Using Dynamic Shear Rheometer

Rubberized bitumen technology has been applied for a long time to enhance the performance of the asphalt pavement. In this research, the influence of natural rubber (NR) latex and crumb rubber (CR) on the conventional and rheological characteristics of 80/100 penetration grade bitumen before and after aging was compared. Conventional tests of penetration, ring and ball temperature, and ductility were conducted to evaluate the consistency of base bitumen and rubberized bitumen. A dynamic shear rheometer (DSR) test was carried out to evaluate the viscoelastic characteristics of the base and rubberized bitumen. The results showed that the addition of NR latex and CR reduced the penetration grade and increased the ring and ball temperature and ductility of the rubberized bitumen. This indicates that promising enhancement of the bitumen properties can be expected with the addition of NR latex and CR. The rheological properties analysis results showed that addition of CR up to 8% and NR latex up to 4% improved the complex modulus and rutting resistance of the rubberized bitumen compared to conventional bitumen. This indicates that the application of NR latex and CR in bitumen modification is expected to improve the durability of asphalt pavement.

Chitosan and Natural Rubber Latex Biocomposite Prepared by Incorporating Negatively Charged Chitosan Dispersion.

Generally, natural rubber/chitosan (NR/CT) biocomposites could be prepared by either mixing natural rubber latex (NRL) with CT acid solution or mixing dry NR with CT powder on mixing equipment. In the present work, a new mixing method has been proposed and properties of the obtained NR/CT biocomposites are investigated. CT particles were prepared to have a negative charge that could be dispersed in water by using a ball mill before mixing with NRL. The effects of CT loading varied from 0 to 8 phr on latex properties and physical properties of NR/CT biocomposite films were focused. The results showed that the viscosity of NRL increased with increasing CT loading. With increasing CT loading from 0 to 8 phr, 300% modulus of the NR/CT biocomposite film increased, whereas the opposite trend was found for elongation at break. Additionally, the presence of CT in the biocomposite resulted in an increased elastic modulus (E’) in conjunction with enhanced antibacterial activity against Staphylococcus aureus (S. aureus).

Field latex production in Southern Thailand: a study on farmers’ and traders’ practices that may affect the quality of natural rubber latex delivered to the factories

Field latex is an important raw material in Thailand, produced by a large number of smallholders and handled by numerous local traders. This diversity of stakeholders involved along the production and marketing chain could result in the variability of the latex quality delivered to the factories. Latex processing industries need a raw material with consistently specified properties. Therefore, it is crucial to identify the factors that could affect latex properties. However, a complete description of the practices from the farmer to the factory is missing. Thus, a study was conducted to (1) characterise the upstream practices, (2) identify variable practices and (3) analyse farmers’ and traders’ perceptions of field latex quality that are believed to influence their practices. A survey was conducted with 398 field latex producers and 182 field latex traders distributed in eight provinces of Southern Thailand. The results showed that some agronomic practices in the mature plantations presented homogeneity (planting material, weed control, management of the inter-row of the plantations) while others (fertilisation, tapping panel treatment, harvesting practices) presented important diversity. Farmers’ and traders’ post-harvest practices presented limited sources of contamination. Nonetheless, for both stakeholders, an important possible source of variability was the quantity of latex preservative used. Finally, the analysis of the practices and the perception of the stakeholders clearly showed that field latex quality was determined both before and after harvesting. Research is still needed to analyse the impact of some agronomic practices on field latex quality. Latex traders also appeared as key stakeholders dealing with the quality.

Carbon dots: Fluorescence active, covalently conjugated and strong reinforcing nanofiller for polymer latex

This paper reports a unique approach to the synthesis of rubber nanocomposites in which functionalized carbon dots (cdots) are covalently bonded to functionalized rubber latex. In this approach, the cdots are functionalized with amine (-NH2) groups that are capable of chemically binding with the carboxylated styrene butadiene rubber (XSBR) latex possessing acid (-COOH) groups. Pristine cdots are characterized using powder X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), fluorescence spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy and high resolution transmission electron microscopy (HRTEM). The -COOH groups of XSBR latex has been covalently appended with the -NH2 groups of cdots using N-hydroxysuccinimide (NHS) and 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide (EDC) mediated amide coupling. FTIR spectroscopy and XPS endorse the covalent conjugation of cdots with XSBR latex. Remarkable increase in the maximum tensile stress and elongation at break of XSBR has been observed by addition of very less amount cdots. XSBR containing 0.8 parts per hundred of rubber (phr) of cdots shows a maximum tensile stress value which is around 235% higher in comparison to neat XSBR. Dynamic mechanical analysis (DMA) shows the reduction in the tan δ peak height and increase in the tan δ peak temperature of XSBR by incorporation of cdots. Also, XSBR containing 0.8 phr of cdots shows an elastic modulus (E’) value which is around 70% higher in comparison to neat XSBR. The maximum degradation temperature (Tmax) and the onset of degradation temperature (Ti) of XSBR containing 1 phr of cdots is around 10 °C and 8 °C higher when compared to neat XSBR. The prominent improvement in the overall properties of XSBR latex by addition of cdots has been attributed to the enhanced cross-linking introduced by the covalently conjugated cdots in XSBR matrix. XSBR-cdots nanocomposite has also been found display good photoluminescence properties due to the presence of cdots, which are confirmed by UV–Vis spectroscopy and fluorescence spectroscopy studies. Morphology of XSBR-cdots nanocomposites has been studied using HRTEM and atomic force microscopy (AFM).

Antileishmanial activities of leaf latex and compound isolated from <i> Aloe ghibensis</i> Sebsebe & Friis

Aloe ghibensis Sebsebe & Friis is traditionally used in Ethiopia for the treatment of various ailments including skin problem, wounds and malaria. Phytochemical constituents and antileshimanial properties of the leaf latex of A. ghibensis have not been reported. The objective of this study was, therefore, to determine the phytochemical constituents and in vitro antileishmanial activities of the leaf latex of A. ghibensis and its major compounds against two Leishmania species. Preparative TLC was used to isolate compounds from the leaf latex of A. ghibensis and spectroscopic techniques including 1D- and 2D-NMR as well as ESI-MS were employed to elucidate structures of the isolated compounds. In vitro antileishmanial activity was performed against promastigotes and axenically cultured amastigotes of Leishmania aethiopica and Leishmania donovani clinical isolates using Alamar Blue assay. Phytochemical investigation led to the isolation of two major anthrones, identified as aloin A/B and 7-hydroxyaloin A/B. Both the leaf latex of A. ghibensis and isolated compounds showed antileishmanial activity with IC50 values ranging from 1.6 ± 0.43 to 3.64 ± 0.09 µg/ml and 1.87 ± 0.21 to 3.72 ± 0.12 against promastigotes and axenically cultured amastigotes of L. aethopica and L. donovani, respectively. Moreover, the test substances were found to be less toxic (LC50 = 145 ± 0.72 to 156 ± 0.08 µg/ml) than amphotericin B (LC50 = 12.11 ± 0.51 µg/ml) towards human monocytic cell line (THP-1). The present study revealed that the latex and pure compounds possess genuine antileishmanial activity with high selectivity indices (SIs). Therefore, the isolated compounds can be used as a scaffold for the development of effective drugs for leishmaniasis.

Toward replacement of methyl methacrylate by sustainable bio-based isobornyl methacrylate in latex pressure sensitive adhesive

Sustainable bio-based monomer isobornyl methacrylate (IBOMA) was evaluated as an alternative to traditional petroleum-based methyl methacrylate (MMA) as hard monomer in the application of acrylic latex pressure sensitive adhesive (PSA). The influence of bio-based IBOMA on the viscosity and particle size of the latexes and the gel content, sol molecular weight (Mw, Mn) and adhesive properties (loop tack, peel strength and shear strength) of the PSA copolymers were investigated. In addition, transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), contact angle analysis, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) were used to characterize the structure and properties of latexes and corresponding films. Results were compared with those obtained when using traditional petroleum-based hard monomer MMA. Some interesting phenomena and results were indeed obtained in this work. This article will not only enrich the application of bio-based monomer IBOMA in the field of acrylic emulsion PSA, but also provide sustainable methods for the preparation of high performance acrylic emulsion PSAs (e.g. high water resistance and high cohesion emulsion PSAs).

Environmentally Friendly Water-Based Self-Crosslinking Acrylate Dispersion Containing Magnesium Nanoparticles and Their Films Exhibiting Antimicrobial Properties

A water-based polymeric acrylate dispersion (latex) containing MgO nanoparticles, which had been added at a concentration of 1.5% (with respect to the monomers) during the preparation procedure, was investigated as an environmentally friendly binder for sanitary interior paints. The properties of this new latex were compared to those of a reference system free of the magnesium nanoparticles, synthesized by the same route, i.e., by semi-continuous emulsion polymerization. Tests were made in order to ascertain the mechanical and chemical properties, flash corrosion resistance and antimicrobial effect of the latex films. The results revealed that the new latex containing magnesium nanoparticles provided solvent-resistant coating films having pronounced antimicrobial activity against all the tested bacterial and fungal strains. The desirable antimicrobial properties can be ascribed to the sharp-edged character of magnesium nanoparticles, the peroxidation of lipids and the formation of reactive oxygen species. Moreover, no flash corrosion was formed beneath coating films containing magnesium nanoparticles, which can be attributed to the alkaline action due to the dissolution of a fraction of MgO in latex medium. The results of all of the tests provided evidence of the superiority of the polymeric dispersion with the magnesium nanoparticles to the reference system containing no nanoparticles.

Strength and Durability of Styrene Butadiene Latex Modified Concrete with Silica Fume

This paper discussed the properties of styrene butadiene rubber (SBR) latex modified concrete. The latex modified concrete using SBR latex were prepared with various polymer-binderratios and tested for compressive strength, flexure strength, elastic modulus and rapid chloride penetration test. Latex contents were varied as 5, 10 and 15 percentages by mass of binder (cement and silica fume). The effect of the polymer-binder ratio on the properties of latex modified concrete was examined. It was concluded from the test results that the compressive strength and elastic modulus decrease with polymer binder ratio and flexural strength increasing with polymer binder ratio. Addition of latex reduces the chloride ion penetration due to latex film formation..

Physical Characterization of Latex from <i>Artocarpus heterophyllus </i>Lam. (Jackfruit) and Four Related <i>Artocarpus </i>spp.

This study focused on the physical properties of latex extracted from five species of Artocarpus J.R.Forster & G.Forster, namely: A. altilis (Parkinson) Fosberg, A. blancoi Merr, A. camansi Blanco, A. heterophyllus Lam., and A. ovatus Blanco as potential natural adhesives. Surface morphology showed that all five Artocarpus spp. have no specific forms, but otherwise flexible and viscoelastic. Contact angle measurements showed that all samples of Artocarpus spp. were hydrophilic with low contact angle values owing to the contents of natural source of the latex. FTIR analysis matched all Artocarpus latex samples to that of Polyvinyl acetate. Highest resin content was found on A. ovatus with all the species containing natural resin. It was also confirmed that out of the three stress strain analyses, A. camansi had the highest values for tensile strength, A. ovatus had the highest values for Young’s modulus of elasticity and the highest percentage elongation values belonged to A. heterophyllus. Adhesive shear strengths with maximum force values were highest in A. ovatus. Through cluster analysis, out of the eight variables tested A. heterophyllus was the outgroup being attributed to its latex gum-like property. All the above tests and analyses suggested that latex of all five Artocarpus spp. were similar in characteristics to polymer adhesive. Among which A. camansi and A. ovatus exhibited high results on adhesive strength tests.

Effects of post-gamma irradiation on swelling and mechanical properties of gamma vulcanized natural rubber latex (GVNRL) films

Gamma vulcanized natural rubber latex (GVNRL) films have shown promising properties for various applications that require less hazardous chemicals used or released during manufacturing and/or utilization. Examples of potential applications include the uses as chemical-free latex gloves in medical or food-related facilities and as stretchable latex covers for food and agricultural products. However, due to possible degradation on swelling and mechanical properties of these films from post-gamma irradiation used for sterilization, thorough investigations are required in order to fully understand their possible changes and/or degradations in properties of interest. As a result, this work investigated on effects of post-gamma irradiation on swelling and mechanical properties of natural rubber latex (NRL) films, which were pre-vulcanized using 12-kGy and 24-kGy gamma irradiation. The properties of interest in this work included tensile modulus at 300% elongation, tensile strength, and elongation at break, as well as other related physical properties such as swelling ratios and crosslink densities. The results showed that, for samples before post-gamma irradiation, the GVNRL films with 24-kGy vulcanizing dose had higher tensile modulus, tensile strength, and crosslink density, but lower elongation at break and swelling ratio, than the films with 12-kGy vulcanizing dose. However, after post-gamma irradiation at the accumulated dose of 24 kGy, the films with 12-kGy vulcanizing dose showed significant improvements in the values of tensile modulus, tensile strength, and crosslink density, whereas the films with 24-kGy vulcanizing dose showed noticeably degradation in these properties. Hence, the overall results suggested that, while higher gamma vulcanizing doses could initially produce NRL films with higher mechanical strength, they were more negatively affected by post-gamma irradiation such that mechanical degradation could be observed.

Effect of Nano-Silica on the Physical, Mechanical and Thermal Properties of the Natural Rubber Latex Modified Concrete

The preparation and properties of latex modified concrete (LMC), nano silica modified concrete (nSMC) and silica-latex modified concrete (SLMC) have been investigated in this study. Properties like compressive strength, tensile strength, flexural strength, thermal characteristics and water absorption have been evaluated. The 7-day compressive strength has increased 37% (30.15 N/mm2) after the inclusion of nano silica and latex. The composite has showed considerable improvements in splitting tensile strength (3.24 N/mm2), flexural strength (6.05 N/mm2) and thermal conductivity, while it lowered the water absorption rate. The property increase has been attributed to the pore filling and pozzolanic activity of nano silica and densification of matrix by natural rubber latex and nano silica. The results of this study have suggested that the addition of nano silica and latex could be a relevant technique toward conventional concrete as a key material along with energy efficient construction and building technology.

Shodhana (processing) of Rakta-Snuhi (Euphorbia caducifolia Haines.) latex with Chincha (Tamarindus indica L.) leaf juice: A pharmaceutical analysis.

Background:Latex of Euphorbia caducifolia Haines. (Euphorbiaceae), botanical source of Rakta Snuhi, a caustic irritant, is being used in different Ayurvedic therapeutics, after proper processing (Shodhana) in some specific media. Shodhana of Snuhi latex with Chincha-Patra Swarasa (juice of tamarind leaves) using Raudra Yantra (instrument/pot kept under sunlight for drying) has been recommended in Ayurveda texts. Snuhi is one of the Upavisha (sub toxic group of herbal drugs) and a well-known plant in the Indian system of medicine. It is used in pharmaceutical procedures like preparation and processing of drugs.Aim:The aim of the study was to carry out Shodhana of E. caducifolia latex with Chincha-Patra Swarasa.Material and methods:Fresh latex of Snuhi was collected from the Sapada area of Jamnagar, Gujarat and fresh leaves of Tamarindus indica L. were collected from the herbal garden of the university and Swarasa was extracted by traditional expression technique. Shodhana of Snuhi Kshira was done under sunlight dried and shade dried method by mixing it with leaf juice of Tamarindus indica L. in a glass bowl in different ratio i.e. Kshira: leaf juice was 8:4, 8:2, 8:1 respectively.Results:This study reveals certain changes in physico-chemical parameters (pH) and organoleptic characters of processed E. caducifolia latex by Tamarind leaf juice both in shade-dried and sunlight-dried samples. Under HPTLC, Shodhana of E. caducifolia latex with Tamarind leaf juice alters the number of spots both sunlight-dried and shade-dried samples. In sun-dried sample, the number of spots increased when the concentration of Tamarind leaf juice is decreased in HPTLC study. The study reveals that in case of shade-dried Shodhita (processed) Snuhi latex sample, the concentration of lupeol increases with the increasing quantity of Tamarind leaf juice.Conclusion:Shodhana with Tamarind leaf juice changes both qualitative and quantitative property of Snuhi latex.

Assessment and selection based on girth and yield performance of new <em>Hevea genotypes</em> generated from controlled hybridization

The objective of this study was to evaluate the girth and yield performance of new Hevea genotypes obtained from the 1998 hand pollination (HP) program. Sixty-five new genotypes were assessed along with the control clones viz. RRIC 121, RRIC 130 and RRISL 205. Dry rubber yield for six years, annual girth at the 14th year and girth increment, percentage of tappable trees, survival trees and tapping panel dryness affected trees and latex properties of selected genotypes were evaluated. Considering the results, 63% of the genotypes were recorded as significantly higher or similar average yield compared to control clones. The genotypes, 98-80 and 98-219 were the top-rankers with average yields of 53.7 g and 52.0 g per tree per tapping, respectively. Moreover, the progeny generated from 1998 hand pollination consisted of good yielders similar to the yield of the clone RRIC 121 and could be considered as potential candidates for future clonal selection programmes to develop elite clones. Eighty-two percent of the genotypes showed significantly higher or similar mean girth compared to controls. Genotypes, 98-276 and 98-68 were ranked at number one and two, which have obtained respective girth values of 80.6 cm and 76.5 cm. Eighteen percent of genotypes recorded more than 70 cm of mean girth, which was an indicator of the development of vigorous timber clones in the future. Moreover, these genotypes possess high yield potential. Almost all the genotypes had significantly high girth increment during the immature phase than the post tapping phase. Genotypes 98-80 and 98-219 had performed well based on the dry rubber content (DRC), sucrose and inorganic phosphorus values. In conclusion, the 1998 HP programmes has generated a valuable pool of genotypes that have paved the path to producing outstanding Hevea clones.

Effect of organoclay reinforced acrylate latex particles on the cement paste performance

In this study, to investigate the effects of organoclay nanoparticles on the properties of latexes as a cement additive, two kinds of acrylate latexes, poly(styrene-co-butyl acrylate-co-metacrylic acid) (PSBAMA) and poly(styrene-co-2ethylhexyl acrylate-co-metacrylic acid) (PSEHAMA), and their nano composites with organoclay nanoparticles, Cloisite 15A, were synthesized via in-situ emulsion polymerization. Obtained results from laser light scattering (LLS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and mechanical test showed good dispersion of Cloisite15A (C15A) nanoparticles in the polymer matrix. Afterward, synthesized latexes with various amounts of organoclay nanoparticles were added to cement paste to investigate its performance. The mechanical test results showed that although neat latexes improved the flexural strength of the hydrated cement paste (up to 28.89%), existence of the organoclay nanoparticles in the structure of the latexes improved the flexural strength further (up to 47%). Furthermore, despite the reduction in compressive strength of the cement paste by adding neat latexes, existence of organoclay nanoparticles in the structure of latex almost eliminated this drawback of using latexes in cement paste. In addition, the results showed that the incorporation of 5 wt% emulsion particles containing 1 wt% Cloisite15A (C15A) considerably decreased the water absorption of the paste. Studies by X-ray diffractometry (XRD) and Fourier transform infrared (FTIR) spectroscopy indicated that the degree of hydration of the paste was increased in the presence of emulsion particles. Existence of neat and composite latex particles also changed the morphology of the cement, which was confirmed by scanning electron microscopy (SEM) results.

Effect of coalescents on properties of protective styrene-acrylate latex coatings of oriented particle chipboards

It is necessary to note that in the production of finishing and protective materials for the surfaces of oriented chipboards, the most effective film former today is considered to be styrene-acrylate latex. However, the known styrene-acrylate dispersions have a minimum film formation temperature within 14–20 ° C, which doesn’t satisfy mass construction works. In order to obtain high-quality films in a wide range of temperatures, it is necessary to use special additives - coalescents. It was decided to use methoxypropanol, ethylene glycol and butyl glycol as coalescents. Their main selection criterion was the homogeneity of the resulting film and the absence of external defects. Based on the studies conducted, it was determined that the butyl glycol additive in the composition leads to the reduction in the elastic modulus of film coatings, which, in its turn, invariably leads to the increase in the relative elongation at break. The butyl glycol additive also enhances the film-forming and adhesive properties of styrene-acrylate latexes. According to the results of the experiments a composition with 4% wt. butyl glycol content as a coalescent was selected for further research.

Manipulation of chain transfer agent and cross-linker concentration to modify the performance of fluorinated acrylate latex pressure sensitive adhesive

n-Dodecyl mercaptan (DDM) chain transfer agent and 1,6-hexanediol diacrylate (HDDA) cross-linker were used to manipulate latex properties in a monomer-starved seeded semi-continuous emulsion polymerization of butyl acrylate (BA), fluorine monomer dodecafluoroheptyl methacrylate (DFMA) together with acrylic acid (AA) and 2-hydroxyethyl acrylate (HEA). The influences of both DDM and HDDA on the particle size of the latex, as well as on the gel content, thermostability (differential scanning calorimeter and thermal gravimetric analysis), surface properties (X-ray photoelectron spectra (XPS), contact angle analysis and atomic force microscopy), and viscoelasticity (N,N-dimethylacrylamide) of the polymer films were investigated. The results showed that the introduction of DDM and HDDA has no significant effects on the final particle size of the fluorinated pressure-sensitive adhesives (PSA) latexes. XPS analysis indicated that the fluoroalkyl groups had the tendency to enrich on the surface of the film. However, this enrichment of fluorine on the film surface was reduced after the introduction of HDDA, while increased with the addition of DDM. It was also found that the gel content, glass transition temperature (Tg), thermal stability, surface roughness, and modulus (G′, Gʺ) of the fluorinated latex PSA were all increased with the introduction of HDDA. Nevertheless, opposite trends were observed for the latex after the addition of DDM. Finally, the effects of DDM and HDDA on the adhesive properties (i.e. loop tack, peel strength and shear strength) of the fluorinated latex PSA were also evaluated.

Total Solid Content and Compound Properties from Different Collection Time of Hevea brasiliensis Latex

Abstract This study compared the total solid content and compound properties of Hevea rubber latex produced from material collected during different periods. Samples were collected from five trees, with the collection replicated three times with tapping task as replication. Observed parameters included total solid content, vulcanization characteristics, technical and physical properties. The results exhibited that the longer latex flowed, the more total solid content tended to decrease. Results indicate that compound of latex collected 20 minutes (C20), 60 minutes (C60), and 300 minutes (C300) after tapping qualified for SIR 20. Other parameters did not show a significant difference among the three tested compounds. Considering the products requiring high dry rubber content, it is suggested not to blend the late collection with main collected latex.