Improvement of ageing properties of rubber films prepared from radiation-vulcanized natural rubber latex

Radiation-vulcanization of natural rubber latex (NRL) with n-butyl acrylate gives a higher tensile strength for films obtained after casting. The ageing properties of radiation-vulcanized natural rubber in the presence of various antioxidants have been investigated. In order to find out suitable antioxidants for radiation-vulcanized natural rubber latex (RVNRL) films, extraction of the gel fraction was carried out in xylene with 1 wt.-% antioxidant and air bubbling. Antioxidants which give less reduction in gel fraction due to oxidative degradation during extraction are effective for ageing tests of RVNRL films. It was found that tris(nonylated phenyl) phosphite (Nonflex TNP) and 2,5-di-tert-amylhydroquinone (Antage DAH), among 12 different antioxidants tested, were the most effective antioxidants for RVNRL films.     

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     

Effect of surface modification of microcrystalline cellulose with ionic liquids on natural latex composites

As an environmentally friendly biomacromolecular material, microcrystalline cellulose (MCC) enhances the performance of natural rubber latex (NRL) composites. However, MCC has strong polarity, which weakens the interfacial interaction between MCC and the non-polar NRL matrix and reduces the reinforcing performance due to the many hydroxyl groups on its surface. In this paper, the ionic liquid (IL) modified MCC/IL material was prepared, and AIR-FTIR, x-ray diffraction, and XPS photoelectron spectroscopy were performed to detect it from the perspective of environmental protection. And natural latex/microcrystalline cellulose/ionic liquid (NRL/MCC/IL) composites with excellent properties were prepared by latex blending. The activation energy, vulcanization characteristics, basic mechanical properties, dynamic mechanical properties, and filler-rubber interfacial interactions of NRL/MCC/IL composites were investigated. The results showed that the vulcanization rate constant of NRL/MCC/IL composites increase, the activation energy decreases and the mechanical properties were significantly improved. At the same time, the matrix interface interaction of composites was quantitatively calculated using Ayala parameters. The results showed that the interfacial interaction force of the composite was stronger after an appropriate amount of IL pretreatment. The whole process is not only conformed to the concept of green development, but also broadens the application of MCC in rubber materials.     

Low-temperature exfoliated graphene oxide incorporated with different types of natural rubber latex: Electrical and morphological properties and its capacitance performance

A simple with cost-effective method in the production and fabrication of graphene-based rubber nanocomposites as electrode materials is still remain a global challenge. In this work, we proposed one- and two-step approaches to fabricate an exfoliated graphene oxide (GO) as nanofiller in three different types of rubber latex polymer, namely, low ammonia natural rubber latex (NRL), radiation vulcanized NRL (RVNRL), and epoxy NRL 25 (ENRL 25). The electrical conductivity and capacitive behavior of nanocomposite samples were investigated under a four-point probe and cyclic voltammetry measurements, respectively. Meanwhile, the morphological properties were observed using field emission scanning electron microscopy, energy dispersive X-ray, optical polarization microscope, high-resolution transmission electron microscopy, Fourier-transform infrared spectroscopy, micro-Raman spectroscopy, and X-ray diffraction. The thermal stabilities of the nanocomposites were also investigated by thermogravimetric analysis. Among all, the GO/RVNRL polymer nanocomposite samples performed a better homogeneity with an improved electrical conductivity (~8.6 × 10⁻⁴ Scm⁻¹) as compared with the GO/ENRL 25 (~3.1 × 10⁻⁴ Scm⁻¹) and GO/NRL (~2.6 × 10⁻⁴ Scm⁻¹) polymer nanocomposite samples. In addition, the GO/RVNRL polymer nanocomposite electrodes showed acceptable specific capacitance (5 Fg^-1). The successfully fabricated conductive GO-based rubber nanocomposites are suitable for new supercapacitor electrodes.     

Preparation of composites of natural rubber latex–Portland cement for moulds

The aim of this study was to prepare polymeric moulds using natural rubber latex (NRL)–Portland cement (PC) composites based on a delayed-action mechanism. Factors affecting the preparation process, such as concentration, mixing percentage, additives and their effects on what is regarded as a delayed-action coacervant combination were studied. Composites of NRL–PC for moulds were prepared as two separate parts. The stabilized NRL (100 parts) with hydroxyethyl cellulose (HEC) 2 parts per 100 parts of latex (phr) as stabilizer and a delayed-action coacervant (sodium metasilicate as a delay agent) 5 parts per 100 parts of latex on the one hand and the dry blend of cement, 65 parts soluble in water, as a paste on the other hand, were mixed thoroughly on the site. HEC was added to the rubber latex to prevent coagulation with the electrolyte (sodium metasilicate) present in the mixture. Some physical properties of the rubber–cement mould prepared, such as shrinkage, water uptake and mechanical properties were studied. Radiation and ageing effects under different environmental conditions (such as under soil, under water and in the presence and absence of UV radiation) on the mechanical stability of the rubber–cement composites were investigated. The mechanical stability improved when the samples were kept under soil and under water, but deterioration was observed for samples kept in the presence of UV radiation (sunlight). The possibility of using the rubber–cement moulds prepared in the field of construction as crack filling material, expansion joint fillers and for soil injection is suggested. © 1998 SCI.     

表面活性剂对天然胶乳蛋白质含量影响的研究

采用表面活性剂直接处理鲜胶乳离心浓缩法制备浓缩胶乳,先用尿素预处理新鲜胶乳后加入表面活性剂处理,再离心浓缩法制备浓缩胶乳。研究表面活性剂种类、尿素预处理时间和预处理温度及新鲜胶乳的pH值对处理所得浓缩胶乳蛋白质含量的影响。同时用傅立叶红外吸收光谱对2种处理方法制备的浓缩胶乳胶膜进行了表征。实验结果表明,鲜胶乳先经尿素预处理一定时间后加入阴离子表面活性剂处理,再离心浓缩制备浓缩胶乳,蛋白质含量显著降低。适宜条件下,浓缩胶乳的氮含量从质量分数0．430％下降至0．089％。红外光谱分析表明,先用尿素预处理新鲜胶乳,然后加入阴离子表面活性剂处理,再离心浓缩制备浓缩胶乳,胶膜在1546cm。处蛋白质的酰胺Ⅱ谱带几乎消失,在3295cm。处N—H的伸缩振动峰明显减弱。     

不同割龄橡胶树RRIM600胶乳组份及性能的研究

本论文研究了割龄3年、割龄13年、割龄20年、割龄24年和割龄28年5种不同割龄的RRIM600天然胶乳的性能。主要研究了天然胶乳粒径,生胶性能,混炼胶的硫化特性以及硫化胶的力学性能。结果表明,割龄28年胶树所得天然胶乳平均粒径最小,胶粒的分布范围较窄,分散性较好;割龄20年橡胶树生胶的P₀和门尼黏度较大,割龄为20年和28年橡胶树所得天然橡胶拉伸强度和撕裂强度较大。     

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

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

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

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

Development of biodegradable natural rubber latex composites by employing corn derivative bio-fillers

This study aims to investigate the viability of employing corn-based fillers (powdered corn grain [CG], corn flour [CF] and cornstarch [CS]) to improve the biodegradability of natural rubber latex (NRL) composites by varying filler loading from 0 to 50 phr. Notable variation in both physical and mechanical properties were observed for the different filler types, with CG-filled NRL demonstrating the better adhesion with NRL. Thus, CG-filled composites were selected for investigation of biodegradability. Increased CG loading in NRL compounds enhanced biodegradation; with over 70% degradation observed for 50 phr CG loading upon 15 weeks of soil burial. However, the trade-off between mechanical properties and biodegradability limits the CG loading in the NRL matrix to 20 phr for manufacturing NRL-based products. It was observed that NRL with CG filler loading of 20 phr conforms to the ASTM D3578 standard for manufacturing rubber gloves; with 50% biodegradation upon 15 weeks of soil burial.     

Use of sodium and potassium butyl xanthate as accelerator for room temperature prevulcanization of natural rubber latex

Sodium and potassium butyl xanthates (Nabxt and Kbxt) were prepared in the laboratory. Characterization of these xanthates were done using Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (¹H NMR) spectroscopy, thermogravimetric analysis (TGA), and differential thermal analysis (DTA) techniques. These xanthates were used as accelerators for the prevulcanization of natural rubber latex (NRL) at room temperature. Optimization of prevulcanization time was done. Films were casted from these prevulcanized NRL. Tensile properties of latex vulcanisates were measured and potassium butyl xanthate gave superior properties to the NRL films compared with sodium butyl xanthate. Effect of thermal ageing on tensile properties of these prevulcanized NRL films was also investigated and these properties were found to be improved after thermal ageing. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

HEMA接枝改性天然胶乳的制备及其粘接性能研究

以甲基丙烯酸羟乙酯(HEMA)作为天然胶乳(NRL)的接枝改性剂,采用乳液聚合法制备了NR-g-HEMA[HEMA接枝NR(天然橡胶)]胶乳;然后以此为基体,并以水溶性松香树脂为增黏树脂、邻苯二甲酸二丁酯(DBP)为增塑剂等,制备相应的NR-g-HEMA胶粘剂;最后,用该胶粘剂压制胶合板,并对胶合板的粘接性能进行了测定。结果表明:采用单因素试验法优选出制备NR-g-HEMA胶乳的最佳工艺条件为m(干态单体)∶m(NRL)∶m(引发剂)∶m(活化剂)∶m(交联剂)=20∶100∶0.2∶0.2∶0.1、反应时间为8 h和反应温度为16℃,此时相应胶合板的剪切强度(1.88 MPa)符合Ⅲ类胶合板的指标要求。     

硫脲修饰交联壳聚糖对天然胶乳蛋白质含量影响的研究

以三聚氯氰为活化剂制备硫脲修饰戊二醛交联壳聚糖，用傅立叶红外吸收光谱对产物进行了初步表征；研究了壳聚糖及其衍生物处理对天然胶乳蛋白质含量的影响．以及处理时间、处理温度和鲜胶乳氨含量对硫脲修饰戊二醛交联壳聚糖处理鲜胶乳后所得浓缩天然胶乳蛋白质含量的影响。结果表明：硫脲修饰戊二醛交联壳聚糖处理鲜胶乳再经离心机浓缩处理可显著降低天然胶乳的蛋白质含量。在适宜的条件下，胶乳胶膜的氮质量分数从未处理的0．430％降至0．132％。鲜胶乳氨含量和处理时间对胶乳的蛋白质含量有较大影响．而处理温度则影响不显著。红外谱图分析表明．硫脲修饰戊二醛交联壳聚糖主要通过与蛋白质形成氢键的形式吸附胶乳中的蛋白质。     

Improvement of Physicochemical Properties of Rubber Blends Between Nonirradiated and Irradiated Rubber Latexes by Radiation Vulcanization

Abstract

Nonirradiated natural rubber latex (NRL) and irradiated (12 kGy) rubber latex were blended in ratios of 100:0, 85:15, 65:35, 50:50, 35:65, 15:85, and 0:100 (v/v) to improve properties of the rubber latex. The blends were irradiated using different irradiation doses (0–20 kGy) in the presence of a radiation vulcanization accelerator (RVA), normal butyl acrylate (n-BA). The physicochemical properties of the nonirradiated latex, irradiated latex, and blend films were determined after leaching with distilled water. It was observed that the tensile strengths of the blend films increases with an increase in the content of the irradiated proportion and radiation doses. The composition of the blends and the doses of radiation were optimized. The maximum tensile strength (31.41 MPa) was found for the 50:50 composition of the blend with a 5 kGy radiation dose. The 100:0 blends, when irradiated, give the highest tensile strength (27.69 MPa) with 12 kGy but a 15:85 nonirradiated blend gives the tensile strength of 26.18 MPa.     

CaCO3/natural rubber latex nanometer composite and its properties

Calcium carbonate/natural rubber (NR) latex nanometer composites were prepared by adding nanometer CaCO₃ whose surface had been treated to natural rubber latex (NRL) before sulfuration. The physical, thermooxidative aging, and thermal degradation properties and the ultra‐microstructure were analyzed with a multipurpose material testing meter, a thermal analysis meter and a Philips XL‐30 SEM, respectively. The results showed that the structures and properties of nanometer composites could be clearly improved by NRL mixed with surface‐treated nanometer CaCO₃. The physical properties of the nanometer composites were best when the content of surface treatment agent was 2.5% (to nanometer CaCO₃), the nanometer CaCO₃/NRL content was 3:100, and the stirring time for treating the surface of the nanometer CaCO₃ was 20 min. Simultaneously, the thermooxidative aging resistance of the nanometer composites also was significantly improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3442–3447, 2006     

Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free‐standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI‐EB (emeraldine base) dissolved in N‐methyl‐2‐pyrrolidone (NMP) to the latex (NRL), (2) adding PANI‐EB dissolved in m‐cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress–strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1498–1503, 2005     

Effect of reynolds number on the dispersion of carbon black in natural rubber latex and filler–rubber interfacial interaction in high‐speed jet flow field

A novel strategy of high‐speed impinging jet processing technique was developed to prepare rubber composites by directly mixing natural rubber latex (NRL) with carbon black (CB). The results showed that CB could be more evenly dispersed into natural rubber by jet compounding technique, compared with the traditional dry process. The dispersion of carbon black was improved at higher Reynolds number because of more intensive shear force. Furthermore, a high performance of natural rubber latex/CB composite was gained by jet compounding technique. When compared to the traditional dry process, the mechanical properties and abrasion resistance of the composite prepared by the jet compounding technique were greatly improved because of the improved filler–rubber interaction at higher Reynolds number. POLYM. COMPOS., 34:1071–1075, 2013. © 2013 Society of Plastics Engineers     

Imparting antimicrobial properties to natural rubber latex foam via green synthesized silver nanoparticles

The green synthesis of silver nanoparticles (AgNPs) in centrifuged natural rubber latex (NRL) by in situ reduction of silver nitrate by NRL is described. The synthesis of AgNP within NRL was successfully carried out without the addition of any reducing agent or stabilizers. The modified AgNP incorporated with centrifuged NRL (GAgNP_NRL) was used to make NRL foam (NRLF) by the Dunlop production method. An ultraviolet–visible (UV‐Vis) spectrophotometer analysis, Zeta potential analysis data and transmission electron micrograph analysis proved that the modified centrifuged NRL consisted of stable nanometer‐sized silver particles. A scanning electron microscopic (SEM)/energy‐dispersive X‐ray spectroscopy (EDX) analysis and UV‐Vis analysis of a latex film made out of the modified GAgNP_NRL compound showed nano‐sized silver particles inside the rubber matrix. The final product of the NRLF (GAgNP_NRLF) made out of the GAgNP_NRL compound was tested for antimicrobial properties against gram‐negative Escherichia coli, gram‐positive Staphylococcus aureus and Staphylococcus epidermidis. The resultant GAgNP_NRLF strongly inhibited the bacteria. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40155.     

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.     

Preparation,characterization and application of gamma irradiated some water soluble polymers/natural rubber latex blends

This work mainly depends on the assumption or hypothesis which exploits the tendency of natural rubber latex (NRL) to cross-link under irradiation in the presence of Alginate and CMC biopolymer and form (ALG/NRL and CMC/NRL) films containing polar/charged functional groups which offer them hydrophilicity, and consequently water absorption capacity. CMC/NRL and ALG/NRL (v/v) blend films prepared first by latex compounding followed by casting technique. The prepared ALG/NRL and CMC/NRL blend films characterized then, by various techniques such as IR, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Equilibrium swelling properties and gel percent GF% of prepared films also studied in details. GF% studies revealed that the GF% increased with increasing both NRL content and irradiation dose for both ALG/NRL and CMC/NRL. Thermal analysis shows the increased thermal stability of the irradiated samples due cross-linking effect of NRL. The improved gel content percentage obtained paved the way for the application of various films in the removal of toxic dyes such as acidic, direct, and basic dyes from waste water where in this study, the films exhibited high affinity toward basic blue dye.