A novel natural rubber‐graft‐cassava starch foam for oil/gasohol absorption

The objective of this work was to study a novel foam prepared from natural rubber grafted with cassava starch (NR‐graft‐CSt) with the addition of super cell (SC) as a blowing agent. The effects of the blowing agent and grafting versus non‐grafting of the starch and the natural rubber on the properties of the foam were investigated. The results show that the optimum curing time decreases with increasing SC loading as observed using a moving die rheometer. The porosity, the number of cells per unit volume and the cell size of the NR/CSt blend increase as a function of the SC loading in the foam. A more open cell structure is produced by higher loadings of SC. The greatest number of cells per unit volume is found at 2 and 6 phr SC for NR‐graft‐CSt and NR/CSt blend, respectively. The foam produced was used as an absorbent for oil. The NR‐graft‐CSt foam shows a maximum percentage oil absorption of around 7 g g^?1. The NR‐graft‐CSt foam is able to be reused as an oil absorbent for a maximum number of over 30 times. The NR‐graft‐CSt foam shows better toluene resistance than the NR/CSt blend. © 2016 Society of Chemical Industry     

Novel composite biopolymers of sodium alginate/natural rubber/coconut waste for adsorption of Pb(II) ions

A novel composite adsorbent in the form of beads for removal of Pb²⁺ from wastewater was prepared by blending a sodium alginate (NaAlg) solution, natural rubber (NR) latex, and coconut waste (cofiber). After being crosslinked by calcium chloride, the beads were highly stable, flexible, and easily used in the environment. The optimum composition of the beads with an average size of 1.1–1.2 mm was 4% NaAlg:NR latex (60% dry rubber content):cofiber at 50:1:0.72 and a 2%w/w CaCl₂ solution used for cross linking. The physico‐chemical properties of the beads were examined by the swelling ratio measurement, ATR‐FTIR, and SEM. The effects of the amount of cofiber, NR, and initial Pb²⁺ ions, the pH of the medium, the bead content, and the contact time, on the adsorption of Pb²⁺ were investigated. NR improved the water resistance and, hence, the stability of the beads. The cofiber increased the porosity and contact area and, hence, the efficiency of the composite beads to adsorb the Pb²⁺ up to 99.6%. The prepared beads are promising material to use for the effective and economical removal of Pb²⁺ from water. POLYM. COMPOS., 35:1013–1021, 2014. © 2013 Society of Plastics Engineers     

Controlled degradation of cured natural rubber by encapsulated benzophenone as a photosensitizer

The photodegradation of raw natural rubber and natural rubber compound film were studied using an artificial solar energy simulator. The properties of degraded rubber sheets containing benzophenone (BP) were determined by solution viscosity, ¹H‐NMR, and FTIR analyses. In the case of rubber compounds containing BP, the changes of tensile strength and crosslinking density were determined. It was found that BP could amply accelerate the photodegradation of rubber. To control the release rate of BP, it was necessary to encapsulate BP with urea–formaldehyde as a matrix. The encapsulated BP or capsule was formed by an interfacial polycondensation reaction between formaldehyde and urea. The kinetic of release rate of BP from urea–formaldehyde capsule was markedly observed within 15 days of release time; after that the rate of BP released from urea–formaldehyde microcapsule was very slow. At the same concentration of BP, the degradation rate of rubber compound by adding BP directly was faster than that of the rubber containing encapsulated BP. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 297–305, 2003     

Characterization of biodegradable semi‐interpenetrating polymer based on poly(vinyl alcohol) and sodium alginate containing natural neem (Azadirachta indica) for controlled release application

A biodegradable novel semi‐interpenetrating polymer network based on poly(vinyl alcohol) (PVA) and sodium alginate containing neem (Azadirachta indica) in the presence of azadirachtin‐A (neem Aza‐A) as well as glutaraldehyde as a crosslinking agent was prepared for use in the controlled released of neem Aza‐A. This is necessary because neem Aza‐A is not stable in the environment. The neem Aza‐A‐containing beads were prepared using various experimental parameters, such as the extent of crosslinking and the amount of loading, in order to optimize the process variables. The chemical structure of the capsule wall was evaluated through X‐ray diffraction. In addition, the swelling behaviour of the capsules and their thermal stability were investigated. The strength of the capsule wall depended on the PVA in the matrix and the crosslinking density. Scanning electron microscopy, electron probe microanalysis and atomic force microscopy data indicated that the structure of the bead walls is rough and nonporous. Swelling results indicated that swelling of the polymeric beads decreases with increasing exposure time to the crosslinking agent. At particular intervals, the remaining concentration of neem Aza‐A was analysed using high‐performance liquid chromatography. The release data were fitted to an empirical equation to estimate the kinetic parameters. The degree of release of neem Aza‐A was controlled by the parameter conditions. Copyright © 2010 Society of Chemical Industry     

Cationic cyclization of purified natural rubber in latex form with a trimethylsilyl triflate as a novel catalyst

Cyclization of deproteinized natural rubber (DPNR) or purified natural rubber latex was effectively performed in latex phase by using trimethylsilyl‐trifluoromethane sulfonate or trimethylsilyl triflate (TMSOTF) as a novel catalyst, which is still not reported in the case of natural rubber latex. Various cyclization conditions affecting the degree of cyclization were studied, such as dry rubber contents, temperature, TMSOTF concentrations, and time. The cyclized products were characterized by FTIR, Raman, ¹H‐, and ¹³C‐NMR spectroscopies, as well as DSC and TGA. The degree of cyclization was estimated by ¹H‐NMR spectrum. It was found that the degree of cyclization in NR was a function of cyclization conditions. The thermal stability of cyclized DPNR increased with the degree of cyclization. Solubility of the obtained rubber was good in chloroform, toluene, cyclohexanone, and cyclohexane, and bad in tetrahydrofuran. The average number molecular weight of cyclized DPNR with 76% degree of cyclization was about 4.2 × 10⁴ g/mol. On the basis of FTIR, Raman, ¹H‐, and ¹³C‐NMR, the C?C of cyclized DPNR dramatically decreased after prolonged reaction time. In addition, the topology of cyclization DPNR particles was rough on its rubber particle as analyzed by TEM. The mechanism for this reaction will also be discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007.     

Development of a controlled release neem capsule with a sodium alginate matrix,crosslinked by glutaraldehyde and coated with natural rubber

At present, the use of huge quantities of synthetic pesticides in conventional agriculture has lead to some major environmental problems. Natural pesticide are now being developed to avoid such problems. Neem (Azadirachtin A) seed oil hereafter designated as neem Aza-A, is one such natural pesticide known to be a powerful insect antifeedant and growth-regulating substance yet limited in application because of its rapid degradation in the environment. Therefore, encapsulation of neem Aza-A within membranes to control its release and improve its stability in the environment may improve its effectiveness. Controlling the release of the pesticide was achieved by utilization of glutaraldehyde–alginate gel capsules modified by coating with a natural rubber (NR) layer. The optimization of the properties of the neem Aza-A containing beads was achieved by changing variables such as the extent of crosslinking, the amount of loading and NR layer. The SEM data indicated that the walls of the beads are smooth and nonporous. The swelling results indicated that swelling of the polymeric beads decreased with increasing exposure time to glutaraldehyde and reduced the rate of release of the pesticide. The data on the rate of release of neem Aza-A from the differently prepared capsules into an aqueous environment was analyzed by HPLC and fitted into an empirical equation to estimate the kinetic parameter. The degree of release of neem Aza-A from capsules was controlled by their condition of formation.     

Synthesis and properties of a novel epoxidised natural rubber-g-cassava starch polymer and its use as an impact strengthening agent

The polarity of epoxidised natural rubber (ENR) was improved by grafting it with cassava starch (CSt). A graft copolymer between ENR and CSt (ENR-g-CSt) was synthesised from CSt solution and ENR latex by using K₂S₂O₈ as an initiator. The highest percentage efficiency of grafting was obtained with 10 parts per hundred (phr) CSt. The swelling ratio of the ENR-g-CSt particles also decreased as a function of the CSt in the sample due to the polarity of the incorporated CSt. After synthesis, it was used as an impact strengthening agent for a polymer blend. Chemically modified NR polymers can form the basis of many value-added NR products that are environmentally friendly and cost effective for use as biopolymers in the future.     

Synthesis of superhydrophobic core–shell mesoporous silica nanoparticles

Mesoporous silica nanoparticles (MSNPs) have been used in variety of applications due to their morphology and porous structure. This work reports the one-pot synthesis of ultrahydrophobic MSNPs using N-cetyl-n,n,n trimethyl ammonium bromide as a cationic surfactant template and ethanol (EtOH) as a cosolvent to form mesopores in the MSNPs. The effects of EtOH on the size and the pore structure of the MSNPs were studied by scanning electron microscopy and transmission electron microscopy. The results show that an addition of EtOH led to an enlargement of the MSNPs and a change in pore structure from a lamellar structure to a radially oriented structure. Co-condensation with two different types of fluoroalkyl silanes; trimethyl(fluoromethyl)silane, and trichloro(1H,1H,2H,2H-perfluorooctyl)silane provided low surface energy MSNPs with a core–shell structure. An assembly on the surface of these F-MSNPs generated nanostructure surface roughness rendering an improvement in surface wettability with water contact angle of 158.6°, which is a characteristic of oleophobic and ultrahydrophobic material.     

Green preparation and physical properties of maleated sulfur-prevulcanized natural rubber

The maleated sulfur-prevulcanized natural rubber (M-SPNR) was prepared from grafting maleic anhydride (MA) onto SPNR latex particle by using benzoyl peroxide as an initiator. Natural rubber latex particle was vulcanized first, and then it was maleated to M-SPNR. The average particle size of M-SPNR was greater than that of SPNR possibly due to the formation of aggregate after addition of MA. The symmetric (strong) and asymmetric (weak) carbonyl stretching vibrations of succinic anhydride rings were confirmed by ATR–FTIR at 1,780–1,784 and 1,854?cm^?1, respectively. The swelling ratios of M-SPNR latex film decreased with increasing MA contents. The tensile strength, modulus, hardness, and elongation at break of SPNR latex film dramatically increased after grafting with MA. Due to the reduction of double bond, the thermal stability of M-SPNR film was better than that of SPNR. The environmental friendly M-SPNR would be further applied as a compatibilizer between NR and biopolymer.