Enhancement of hydrophobicity of natural rubber latex films using diatomaceous earth

Enhancement of the hydrophobic nature of natural rubber latex (NRL) films will open up a wide range of applications for them. Incorporating hexadecyltrimethoxysilane treated superhydrophobic diatomaceous earth (DE) in NRL, resulted in films with increased hydrophobicity. The nano-scale surface roughness for the superhydrophobic surface was provided by DE and low surface energy was achieved by treating DE with hexadecyltrimethoxysilane (treated DE). Surface wettability and morphology were analyzed by water contact angle (WCA) measurements and scanning electron microscopic analysis, respectively. About 38% wt/wt hexadecyltrimethoxysilane to DE ratio could make superhydrophobic DE with WCAs larger than 150°. A dispersion of treated DE was incorporated into NRL resulting in hydrophobic NRL films possessing WCAs greater than 110° with 41% treated DE particle loading. The resulting NRL films were harder and had smaller tensile strength compared to normal NRL film.     

Contribution of hydrogen and/or covalent bonds on reinforcement of natural rubber latex films with surface modified silica

A macromolecular coupling agent containing hydrophilic and hydrophobic groups is made to react with precipitated silica. Interfacial interactions between  OH groups of silica and  COOH groups of macromolecule are found to be created through either hydrogen bonds alone or through hydrogen bonds and covalent bonds. Aqueous dispersions of unmodified and modified silica are prepared and the colloidal stability and particle size distribution of the dispersions are observed. The dispersions at neutral pH are incorporated into vulcanized/unvulcanized natural rubber latex. The formation of hydrogen bonds and/or covalent bonds is studied via FTIR spectroscopy and their contribution in encouraging filler‐rubber interactions is emphasized through mechanical and swelling properties. Uniform distribution and dispersion of modified filler particles throughout the rubber matrix is confirmed by the microstructures of the latex films cast from filler added natural rubber latex. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40380.     

Nanocapsules embedded in natural rubber latex gloves

To prepare medical gloves containing disinfectant agent, poly(methyl acrylate) (PMA) with _w of 550 K was synthesized via the iniferter technique and then used for encapsulating disinfectant agent, i.e., chlorhexidine digluconate (CHD), droplets. The CHD‐PMA nanocapsules suspended in a sodium dodecyl sulfate aqueous solution having 93% encapsulation efficiency were successfully embedded between the outermost and inner layers of γ‐radiation vulcanized natural rubber (RVNR) latex films by the coagulant dipping process. A RVNR/CHD‐PMA nanocapsules/RVNR three‐layer structure was revealed by the contact angle measurement, ATR‐FTIR and SEM. Both the tensile strength and elongation at break of the three‐layer film were also measured. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comparative study of the elasticity and permeability of vulcanized films made with skim and cream natural rubber latex

The purpose of this study was to gain a clearer picture of the structure and properties of vulcanized films made with skim and cream latex from Hevea brasiliensis. The two properties targeted for this study were the elasticity of the films and their permeability to acetone. Surface characterization by atomic force microscopy revealed that vulcanization substantially modified the structure of the films compared to unvulcanized films. Unlike unvulcanized films, particle identity was retained in the vulcanized films made with cream latex, even after 4 weeks of aging. In addition, skim latex gave vulcanized films with greater elasticity than those obtained with cream latex. On the basis of the structural characterization carried out on the latex and films and information from the literature, the greater elasticity of the skim films arose from more entanglements between polyisoprene chains and associations between proteins. Despite differences in the structure, the acetone permeability was very similar for skim and cream vulcanized films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Preparation of low‐allergen natural rubber latex by transglutaminase catalysis

The technique of enzyme treatment on the water‐soluble proteins and mechanical properties of natural rubber latex (NRL) films was studied. The main aim was to introduce an enzymic catalysis method to tackle the protein allergy problem in NRL product. The suitable pH value, the temperature, and the best proportion of transglutaminase to deal with NRL were found. The protein spillage of modified NRL films was greatly lower than that of unmodified NRL, and the tensile strength and the elongation at break of the modified NRL films almost had been scarcely changed. The compactness of the NRL films was improved simultaneously. These suggest that the modified NRL can be used as a kind of latex with low‐allergy personal barrier products such as surgical gloves. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Natural rubber–styrene butadiene rubber latex blends: Time-dependent rheological behavior and film formation

This article focuses mainly on the effect of maturation time on the rheological behavior of unvulcanized natural rubber (NR)–styrene butadiene rubber (SBR) latex blends. Viscosity shows a composition-dependent behavior with maturation time. It was found that there is a marginal decrease in viscosity for all the systems with maturation time except for the 70/30 NR–SBR blend. In this blend, there is a sharp decrease in viscosity with maturation time. This is associated with the exchange of stabilizers with one another until an equilibrium is reached; that is, all the particles of the blend are stabilized with random mixture of stabilizers. The structural build up observed in 70/30 NR–SBR blend was found to be diminished as the maturation time increases. At equilibrium, there is no further exchange of stabilizers. The behavior of this blend has been explained with the help of a schematic model. The effects of blend ratio and surface active agents on the viscosity were also studied. In addition, the time-dependent flow behavior of prevulcanized latex blends was evaluated as a function of vulcanizing systems and prevulcanization time. There is a regular increase in viscosity with prevulcanization time. However, after 3 h, the viscosity of almost all blends levels off, indicating that the curing reaction is complete within this time. Finally, the morphological changes occurred during film formation of the blends were studied using scanning electron microscopy. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1473–1483, 1998     

Effect of magnesium and phosphate ions on the stability of concentrated natural rubber latex and the properties of natural rubber latex–dipped products

The presence of Mg²⁺ ions was found to be a major cause of destabilization of natural rubber (NR) latex. On the other hand, the addition of excess PO ions to remove Mg²⁺ ions could adversely affect the physical properties of dipped products made of NR latex. A series of concentrated latex samples were treated with varying amounts of Mg²⁺ and PO ions. Changes with time in the characteristics of the treated latex samples such as mechanical stability time, volatile fatty acid number, and chemical stability time and in the physical properties of the dipped products such as aged and unaged tensile properties were monitored. The latex batch with a PO ion concentration of 30 ppm was found to produce the best‐quality latex and dipped products. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3120–3124, 2006     

Studies on polymer latex films: IV. Comparison of the permeability of latex and solvent-cast films

Latex and solvent-cast films have been prepared from poly(butyl methacrylate) surfactant-free latices and their permeabilities to water vapour and an aqueous organic solute (p-nitrophenol) have been studied. Latex films show considerable ageing effects and their performance is very dependent upon the conditions of film formation but their barrier properties are not necessarily inferior. A greater dependence on film orientation is evident for latex films.     

Half‐submerged cultivation method for the microbial desulfurization of waste latex rubber

The common method for microbial desulfurization is the submerged cultivation method. However, its cost is high because of the high consumption of the medium. To cut costs and improve the desulfurization effect, the new half‐submerged cultivation method was used in the microbial desulfurization of waste latex rubber (WLR) by Sphingomonas species With this method, much more WLR was added per unit volume of the culture medium to be desulfurized, and the desulfurization process was done without stirring. The technical conditions, such as the addition of WLR, the addition of polysorbate 80 (Tween 80), and the desulfurization time, for the half‐submerged cultivation method were studied, and its desulfurization effect was compared with that of the traditional submerged cultivation method. The results show that the optimum conditions for the half‐submerged cultivation method were the addition of 40% w/v WLR in the medium without Tween 80 and desulfurization for 10 days. The X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy results demonstrate that the decreases in the content of sulfur, S? C bonds, and S? S bonds on the surface of WLR after desulfurization by the half‐submerged cultivation method were greater than those after desulfurization by the submerged cultivation method. The composite of waste latex rubber desulfurized by the submerged cultivation method (SDWLR) and styrene–butadiene rubber (SBR) had better mechanical properties than the composite of waste latex rubber desulfurized by the half‐submerged cultivation method (HDWLR) and SBR. Scanning electron microscopy photographs showed that the combinations of HDWLR and the matrix were better than those of SDWLR and the matrix. Compared with the submerged cultivation method, the half‐submerged cultivation method not only reduced the cost of desulfurization but also improved the desulfurization effect. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41039.     

Novel cross‐linked sericin films: Characterization and properties

In the present study, an attempt has been made to convert sericin into film form and further make it insoluble by forming sericin–aluminum metal complex using alum salt, which may lead to some extent of cross‐linking. After complex formation sericin becomes insoluble in warm water as well as thermal stability and tensile strength improves significantly with increasing alum content. Metal complexed sericin films show good antimicrobial property and both the pure and alum modified sericin (AM‐Sericin) films show a very good oil barrier property. But after complex formation moisture content and swelling percentage of sericin film decreases quite significantly with increasing aluminum concentration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41400.     

Energy dissipation in natural rubber latex films: The effect of stabilizers,leaching and acetone-treatment

Natural rubber (NR) is a versatile material possessing outstanding mechanical properties, which can be used in multiple applications including the rapidly developing dielectric elastomer generators (DEGs). One of the drawbacks of the existing DEGs is their low efficiency, which can be improved by lowering the dielectric and mechanical losses originating from the material. Therefore, the present research was focusing on assessing the ways to minimize the dielectric and mechanical losses of NR films rather than developing a DEG. In this article, the effect of natural proteins and the rubber stabilizers on energy dissipation of NR films was evaluated. Moreover, the effect of sample posttreatment (with water and acetone), curing and time after cure was discussed. As a result, deproteinized NR stabilized by ammonium caseinate outperformed unmodified NR due to reduced dielectric losses, mechanical hysteresis and stress relaxation. Moreover, the posttreatment methods were found to moderately reduce the material-relates losses.     

Structure and adhesive properties of the RFL‐coated continuous basalt fiber cord/rubber interface

The relationships between the structure of the resorcinol‐formaldehyde‐latex (RFL) layer, static adhesion, and interfacial fatigue properties between the RFL‐coated continuous basalt fiber (CBF) cord and a rubber matrix were studied using films prepared from RFL systems with various formulas and H samples prepared with RFL‐coated CBF cord and NR/SBR matrix. Thermomechanical analysis and tensile testing of the RFL films were carried out using a dynamic mechanical analyzer (DMA). The H pull‐out force and fatigue properties were tested using a universal testing machine and an MTS, respectively. The interfacial fatigue life of the RFL‐coated CBF cord/rubber samples exhibited different variation regularity from the variation of the H pull‐out force as F/R and L/RF changed. The static adhesion reflected the connection strength between the cord and the rubber matrix, whereas the characteristics and the properties of the RFL layer played a decisive role in determining the damage rate of the adhesion. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44353.     

Morphology and mechanical properties of natural rubber latex films modified by exfoliated Na‐montmorillonite/polyethyleneimine‐g‐poly (methyl methacrylate) nanocomposites

Na‐montmorillonite/polyethyleneimine‐g‐poly(methyl methacrylate) (Na‐MMT/PEI‐g‐PMMA) nanocomposite latexes were prepared by soap‐free emulsion polymerization in the aqueous suspension of Na‐MMT. The exfoliated morphology of the nanocomposites was confirmed by XRD and TEM. With the aim of improving morphology and mechanical properties of natural rubber latex (NRL) films, the synthesized Na‐MMT/PEI‐g‐PMMA nanocomposites were mixed with NRL by latex compounding technology. The results of SEM and AFM analysis showed that the surface of NRL/Na‐MMT/PEI‐g‐PMMA film was smoother and denser than that of pristine NRL film while Na‐MMT was dispersed uniformly on the fracture surface of the modified films, which suggested the good compatibility between NRL and Na‐MMT/PEI‐g‐PMMA. The tensile strength of NRL/Na‐MMT/PEI‐g‐PMMA films was increased greatly by 85% with 10 phr Na‐MMT/PEI‐g‐PMMA when Na‐MMT content was 3 wt % and the elongation at break also increased from 930% to 1073% at the same time. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43961.     

乳液法氢化丁苯橡胶的表征及其性能

用傅里叶变换红外光谱表征了由丁苯胶乳加氢制备的氢化丁苯橡胶(HSBR),测定了其生胶力学性能。以过氧化二异丙苯为硫化剂,研究了氢化度98%的HSBR的静态、动态力学性能及耐老化和耐化学品性能。结果表明,氢化度98%的HSBR的各种碳碳双键基本饱和,是一种典型的热塑性弹性体,具有较好的力学性能和优异的耐老化性能。硫化胶的拉伸强度可达27.6 MPa,扯断伸长率为300%,撕裂强度44 kN/m;阿克隆磨耗量0.03 cm3,动态压缩永久变形3.75%,动态生热33℃。经过150℃×72 h老化后,其拉伸强度和撕裂强度不变;硫化胶对酸、碱、醇及丙酮有很好的抗耐性,但在甲苯中溶胀严重。     

A comparative study of short nylon fiber—Natural rubber composites prepared from dry rubber and latex masterbatch

A novel method for the preparation of short nylon fiber–natural rubber composites was developed in which short fibers chopped to approximately 6 mm were incorporated in the latex stage and processed into sheet form. By this method, mixing cycle time was reduced without compromising the fiber dispersion. Fiber breakage during mixing was reduced. The new composites when compounded with a dry bonding system based on hexamethylenetetramine, resorcinol and hydrated silica (HRH) showed improved modulus, tensile strength and abrasion resistance compared to conventional composites. Tear strength, resilience, and compression set were similar to the conventional composites. SEM analysis indicated better interaction between matrix and fibers in the case of latex master batch. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Nanofiber films of chloroacetated natural rubber/poly(vinyl alcohol) by electrospinning technique: Silica effects on biodegradation

Green electrospinning technique was employed to prepare chloroacetated natural rubber (CNR)/poly(vinyl alcohol) (PVA) nanofiber films by varying the addition of PVA in the range 2.5–55 wt % followed by encapsulation of 2.5 wt % fumed silica (FS). In this study, the risk of using organic solvents was eliminated using CNR in latex. The encapsulated electrospun fiber mats showed a fairly homogenous composition with enhanced water absorption ability of 703.54% ± 33.95%. The FS improved the interfacial adhesion and contributed to enhancing the intermolecular interaction between the two polymers. The mean diameter of the nanofibers decreased from 64.0 ± 19.0 to 41.0 ± 13.0 nm and significant improvement in the hydrolytic and enzymatic degradation rate was observed implying that FS can facilitate the degradation rate. Furthermore, loading of PVA and encapsulation of FS resulted in an improved stiffness of CNR at room temperature and storage modulus increased to 2.48 and 2.12 MPa, respectively. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46432.     

热裂解气相色谱法测定天然胶乳中的干胶含量

研究热裂解气相色谱法测定天然胶乳中的干胶含量。试验结果表明,干胶含量与裂解主要产物峰面积呈现良好的线性关系,采用标准曲线法测定天然胶乳中的干胶含量,重复测定的相对标准偏差为0.14%,与国标法的平均相对误差为1.51%,定量分析结果准确,操作简便。     

Natural rubber latex: Development and in vitro characterization of a future transdermal patch for enuresis treatment

Enuresis affects up to 20% of children of 5 years old, enuretic children present arginine vasopressin secretion deficiency, compared to normal children. To keep the level of antidiuretic hormone in the body, the aim of this work was to develop natural rubber latex membranes loaded with desmopressin peptide and characterize its in vitro release. Results demonstrated that 60% of desmopressin incorporated in natural latex was released up to 96?h. Furthermore, hemolysis tests showed no detectable disturbance of the red blood cell membranes. Based on the results, it was possible to conclude that natural latex membranes are able to load desmopressin.     

天然胶乳/羧基丁苯胶乳共混制自黏胶乳

在天然胶乳中加入防老剂A和防老剂D及羧基丁苯胶乳(丙烯酸酯压敏胶乳或丙烯酸酯共聚乳液)等,制备了自黏胶乳。结果表明,使用质量分数为1．2％的防老剂A与D的复合防老剂,天然胶乳剥离强度的保持效果较好;添加砂磨轻质CaCO3对天然胶乳自黏性影响较大;将不同牌号的羧基丁苯胶乳与天然胶乳并用,TR-258效果较好,能部分取代天然胶乳,而TR～163和TR-376因自固化作用强．对试样自黏性产生了不利影响。     

Physicochemical and antimicrobial properties of natural rubber latex films in the presence of vegetable oil microemulsions

A series of vegetable oil microemulsions are formulated and incorporated into NR latex to study the potent antimicrobial activity of vegetable oil‐plasticized NR latex film against the adherent bacteria on the treated film. The particle size of latex incorporated with 2.50 phr of oil has attained up to 424 nm after incubated at 35 ± 2 °C for 24 h. The tensile stress of all NR latex films are relatively low, ranged 0.289 to 0.511 MPa. All emulsions are found compatible with NR and the low contact angles (<90°) corresponded to no oil blooming onto the surfaces of NR latex films. The crosslink densities are in good correlation with tensile strengths. The potent antimicrobial properties of the NR latex films are investigated from the viability assessment of the adherent tested Escherichia coli ATCC 25922 (E. coli ATCC 25922) and Staphylococcus aureus ATCC 25923 (S. aureus ATCC 25923). Results shows that NR latex film incorporated with palm kernel oil/soybean oil blend, NR‐E(P/S = 7/3), has significantly killed the adherent S. aureus with 92.5% reduction but showed no significant log reduction in E. coli. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44788.