Preparation and Characterization of Natural Rubber-, Polyethylene- And Natural Rubber/Polyethylene-Clay Nanocomposites

The present research aims at studying the influence of organoclay on the properties of natural rubber (NR), low density polyethylene (LDPE) and NR/LDPE blend. Two types of clays, namely montmorillonite, (MMT) (cationic clay) and layered double hydroxide (LDH) (anionic clay) were used in this study. Secondly, to identify the influence of the organoclay on the thermal and mechanical properties effectively, a thoroughly investigation of the NR-clay and LDPE-clay single-phase and NR/LDPEclay blend were performed. These nanocomposites were evaluated by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and mechanical properties. The organo-montmorillonite (OMMT) and organo-LDH (OLDH) samples were prepared via ion exchange reaction using organic surfactants; cetyltrimethylammonium (CTA), n-dodecyl trimethylammonium (DDT), protonated octadecylamines (ODA) and dodecylamines (DDA) as well as dodecylsulphate (DS). The characterization of organoclay were carried out by the Fourier Transform Infrared spectroscopy (FTIR) and the Carbon, Hydrogen, Nitrogen and Sulphur (CHNS) elemental analysis, Scanning Electron Microscopy (SEM) as well as Surface Area and Porosity Analysis (ASAP). The preparation of a NR nanocomposite may be accomplished either by solvent method or by melt-blending technique. However, the melt-blending technique was applied in this study which is the industrially preferred process. The expansion of the interlayer spacing of the clay indicates the formation of intercalated as well as exfoliated types of nanocomposites which supported by TEM images and XRD diffractograms. Both the tensile strength and the modulus of the nanocomposite increased while elongation at break decreased with the addition of the clay. The Dynamic Mechanical Analysis (DMA) of nanocomposites exhibited enhancement of the storage modulus indicated that the elastic responses of pure NR towards deformation were strongly influenced by the presence of nanodispersed nano-layered material. The thermogravimetric analysis that showed the presence of clay layers in NR matrix gave insignificant improvement in thermal stability of NR-clay nanocomposites. LDPE-clay nanocomposites were prepared by in-situ grafting-intercalating in melt. The organoclay was first modified with maleic anhydride (MAH). It was then blended with LDPE in melt. The grafting MAH onto LDPE chain favors the exfoliation and intercalation of the organoclay, hence resulting better dispersion of clay layers in the LDPE matrix. Tensile properties revealed that the tensile strength increased up to 3 parts per hundred polymer by weight (php) while elongation at break decreased with the addition of the clay. Enhancement in storage modulus observed were the characteristic of reinforcing fillers. Thermally stable LDPE-clay nanocomposites were obtained with the increase of the clay content at higher temperature ( 400 oC). Polymer blends with ratio 70/30 amount of LDPE and NR with N, N-mphenylenebismaleimide (HVA-2) as a compatibilizer was developed. The introduction of cross-links into the elastomer phase has contributed to the improvement of the tensile properties of dynamically vulcanized LDPE/NR blends. These results are supported by scanning electron microscopy (SEM) and Atomic Force Microscopy (AFM) images of extracted surfaces of the blends. Finally, NR/LDPE-clay nanocomposites were successfully prepared by melt intercalation technique. XRD results revealed the formation of both intercalated and exfoliated nanocomposites. The tensile properties enhanced resulted from melt compounding of NR/LDPE with 3 php or less modified organoclay. All nanocomposites formed in this investigation showed enhancement in the mechanical properties which are the characteristic of reinforcing fillers. The TEM micrograph revealed the clay layers was dominantly distributed in NR domain and manifested by insignificant improvement in thermal stability of the nanocomposites

Effect of hydrolysis time on antioxidant and antimicrobial properties of Jack Bean (Canavalia ensiformis) protein hydrolysate

Jack Bean or Kacang Koro (Canavalia ensiformis) is one of the under-exploited tropical dry beans. This study was aimed to determine the effect of hydrolysis time on physicochemical properties, antioxidative and antimicrobial activity of Jack Bean protein hydrolysate (JBPH). The physicochemical properties of JBPH were evaluated based on protein content, WHC, OHC, degree of hydrolysis, foam stability and foaming capacity. The antioxidative activity of JBPH was measured using DPPH, hydroxyl radical scavenging, superoxide radical scavenging and FRAP. Well diffusion method was used to study antimicrobial activity of JBPH. The highest protein content (33.16±0.03%) obtained in JBPH that hydrolysed for 150 min. The degree of hydrolysis was showed for JBPH highest at 120 min (51.79±0.28%). The size of the microstructure of JBPH analysed using SEM were decrease with hydrolysis time. FTIR analysis confirmed that JBPH comprised of three major components (Region I, II and III). Water holding capacity of JBPH was the highest for the sample hydrolysed for 60 min (63.87±0.72%) while oil holding capacity depicts the highest by it at 180 min (57.17±1.19%). Foaming capacity and foam stability decreased with hydrolysis time. JBPH produced at 120 min hydrolysis time showed the highest inhibition toward DPPH (42.44%) and hydroxyl radicals (20.01%). FRAP and superoxide radical scavenging, JBPH at 90 min showed the highest inhibition (91.15±0.05 µM and 64.33%). JBPH also showed antimicrobial properties by inhibits the growth of P. aeruginosa. The best hydrolysis time to produce JBPH with the highest physicochemical properties was found at 120 min

Preparation and properties of natural rubber/layered double hydroxide nanocomposites

Nanocomposites of natural rubber (NR)/organo ZnAl layered double hydroxide (ZnAl LDH-DS) were successfully synthesized and characterized. A hydrophilic Zn-Al layered double hydroxide (ZnAl LDH-NO3-) was converted into the organophilic form by replacing the nitrate ion in between the ZnAl LDH-NO3- with dodecylsulfate ion (DS) to form ZnAl LDH-DS. The melt intercalation technique followed by vulcanization process was adopted to synthesize the nanocomposites of NR/ZnAl LDH-DS. Intercalation of DS ion into the interlayer of ZnAl LDH-NO3- increased the surface area and the porosity of the LDH. X-Ray diffractogram of the organophilic ZnAl LDH-DS shows that the basal spacing of the ZnAl LDH-NO3- expands from 0.89 to 2.53 nm due to the accommodation of DS ion in the intergallery. After the compounding process with the NR, the basal spacing of ZnAl LDH-DS in the composites is increased to 3.90 and 3.27 nm when the ZnAl LDH-DS contents were 1 and 15 phr, respectively. Transmission electron microscope image revealed that the ZnAl LDH-DS was distributed in the NR matrix in such a way of exfoliated and different grade of intercalated. The tensile strength values of NR/ ZnAl LDH-DS (nanocomposites) were found to be higher than that of the NR/ZnAl LDH-NO3- (macrocomposites)

Removal of methyl orange dye by manganese/aluminium- layered double hydroxide

As textile production flourishes nowadays, the amount of dyed wastewater entering the water body has also increased. Dyes could have serious negative impacts to the environment and also the human health, hence, they need to be removed from the water body. In this study, layered double hydroxide (LDH) of manganese/aluminium (MnAl) was synthesised to be used as a potential adsorbent to remove methyl orange (MO) dye due to its unique lamellar structure which provides LDH with high anion adsorption and exchange ability. MnAl was synthesized by using co-precipitation method and characterized by powder X-ray diffraction (PXRD), Fourier-Transform Infrared Spectroscopy (FTIR), Inductively coupled plasma atomic emission spectroscopy (ICP-AES) and Carbon, Hydrogen, Nitrogen, Sulphur (CHNS) elemental analysers, and Accelerated Surface Area and Porosity Analyzer (ASAP). Adsorption studies were conducted at different contact times and dosages of MnAl to evaluate the performance of MnAl in removing MO from water. Kinetic and isotherm models were tested using pseudo-first order, pseudo-second order, Langmuir isotherm and Freundlich isotherm. MnAl LDH was found to be perfectly fitted into pseudo-second order and Langmuir isotherm

Preparation and characterization of natural rubber/layered double hydroxide nanocomposites

Nanocomposites of organo Zn‐Al layered double hydroxide (LDH) with natural rubber (SMR CV60) were successfully synthesized and characterized. To prepare the nanocomposites, a hydrophilic Zn‐Al layer double hydroxide (ZnAl LDH ‐NO3−) was first converted into the organophilic form by using dodecylsulphate ion (DS) as a guest in Zn‐Al layer double hydroxide (ZnAl LDH‐DS). Intercalation of dodecylsulphate anion into the interlayer of LDH increased the surface area and the porosity of LDH. Nanocomposites of NR / ZnAl LDH‐DS was then prepared by melt intercalation method using Haake internal mixer. The resulting compounds were then vulcanizated using the conventional method. X‐Ray diffractogram the organophilic ZnAl‐DS LDH shows the basal spacing of the ZnAl‐LDH expands from 0.89 nm with nitrate as the intergallery anions to 2.53 nm due to the accommodation of DS surfactant anions. After the compounding with the natural rubber, the basal spacing of ZnAl LDH‐DS in the composites is increased to 3.90 and 3.66 nm when the Zn‐Al‐LDH‐DS contents are 1 phr and 15 phr respectively. TEM revealed the layered double hydroxide generally uniformly distributed in the rubber matrix. Further characterization indicates that the tensile strength of NR/ Zn‐Al LDH‐DS (nanocomposites) is higher than that of the NR/Zn‐Al LDH‐NO3− (macrocomposites)

Preparation of Layered Double Hydroxides with Different Divalent Metals for the Adsorption of Methyl Orange Dye from Aqueous Solutions

In this study, layered double hydroxides (LDHs) with different divalent metal cations were prepared and then utilized as adsorbent for the removal of dye from aqueous solutions. LDHs are positively charged lamellar solids consisting of divalent and trivalent metallic cations and exchangeable interlayer anions. The potential combinatorial series of M/aluminum (M=Ca, Mn and Zn) LDHs for the removal of methyl orange (MO) dye from aqueous solutions were investigated.  LDHs were synthesized via a co-precipitation method and characterized using powder X-Ray diffraction (PXRD) and Fourier-transform infrared spectrophotometer (FTIR). The LDHs were then used as adsorbent for the removal of MO dye at different LDH dosages. As the LDH dosage increased, the removal percentage of MO dye also increased. CaAl, MnAl and ZnAl LDHs were able to adsorb up to 96.6%, 97.9% and 99.8% of MO dye, respectively, after being put in contact with the LDHs for 24h. Their adsorption ability was further analyzed by using Langmuir and Freundlich isotherm models in which the adsorption mechanism was determined. Adsorption of MO by CaAl, and ZnAl LDHs was governed by the Langmuir isotherm model while the adsorption data for MnAl LDH was found to fit well with the Freundlich isotherm model

Biomedical PEVA Nanocomposite with Dual Clay Nanofiller: Cytotoxicity, Mechanical Properties, and Biostability

Poly(ethylene-vinyl acetate) (PEVA) nanocomposite incorporating dual clay nanofiller (DCN) of surface modified montmorillonite (S-MMT) and bentonite (Bent) was studied for biomedical applications. In order to overcome agglomeration of the DCN, the S-MMT and Bent were subjected to a physical treatment prior to being mixed with the copolymer to form nanocomposite material. The S-MMT and Bent were physically treated to become S-MMT(P) and Bent(pH-s), respectively, that could be more readily dispersed in the copolymer matrix due to increments in their basal spacing and loosening of their tactoid structure. The biocompatibility of both nanofillers was assessed through a fibroblast cell cytotoxicity assay. The mechanical properties of the neat PEVA, PEVA nanocomposites, and PEVA-DCN nanocomposites were evaluated using a tensile test for determining the best S-MMT(P):Bent(pH-s) ratio. The results were supported by morphological studies by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Biostability evaluation of the samples was conducted by comparing the ambient tensile test data with the in vitro tensile test data (after being immersed in simulated body fluid at 37 °C for 3 months). The results were supported by surface degradation analysis. Our results indicate that the cytotoxicity level of both nanofillers reduced upon the physical treatment process, making them safe to be used in low concentration as dual nanofillers in the PEVA-DCN nanocomposite. The results of tensile testing, SEM, and TEM proved that the ratio of 4:1 (S-MMT(P):Bent(pH-s)) provides a greater enhancement in the mechanical properties of the PEVA matrix. The biostability assessment indicated that the PEVA-DCN nanocomposite can achieve much better retention in tensile strength after being subjected to the simulated physiological fluid for 3 months with less surface degradation effect. These findings signify the potential of the S-MMT(P)/Bent(pH-s) as a reinforcing DCN, with simultaneous function as biostabilizing agent to the PEVA copolymer for implant application