Wood density and types of shrinkage were examined in two rubberwood latex timber clones of rubber (Hevea brasiliensis) namely RRIM 2020 and RRIM 2025, planted at densities of 500, 1000, 1500, and 2000 trees/ha, within a trial plot. The mean wood density showed a low descending trend towards high planting densities in both clones. Wood density was significantly and negatively correlated with planting density. The strength of correlation was moderate. The mean longitudinal shrinkage in both clones and tangential shrinkages in clone RRIM 2020 showed no significant difference among planting densities. The tangential (in RRIM 2025), radial and volumetric shrinkages in both clones decreased from low to high planting densities and the differences were more pronounced between densities of 500 trees/ha and 2000 trees/ha. The magnitudes of correlation between these shrinkages and planting density were low. The regression models indicated that wood density could be more ascribed by planting density followed by volumetric shrinkage. This study exhibited low variations in wood density and shrinkages among clones and the respective planting densities; however, RRIM 2025 was more stable than RRIM 2020.
Streptomyces sp. strain CFMR 7, which naturally degrades rubber, was isolated from a rubber plantation. Whole genome sequencing and assembly resulted in 2 contigs with total genome size of 8.248 Mb. Two latex clearing protein (lcp) genes which are responsible for rubber degrading activities were identified.
Rubber materials have greatly contributed to human civilization. However, being a polymeric material does not decompose easily, it has caused huge environmental problems. On the other hand, only few bacteria are known to degrade rubber, with studies pertaining them being intensively focusing on the mechanism involved in microbial rubber degradation. The Streptomyces sp. strain CFMR 7, which was previously confirmed to possess rubber-degrading ability, was subjected to whole genome sequencing using the single molecule sequencing technology of the PacBio® RS II system. The genome was further analyzed and compared with previously reported rubber-degrading bacteria in order to identify the potential genes involved in rubber degradation. This led to the interesting discovery of three homologues of latex-clearing protein (Lcp) on the chromosome of this strain, which are probably responsible for rubber degrading activities. Genes encoding oxidoreductase α-subunit (oxiA) and oxidoreductase β-subunit (oxiB) were also found downstream of two lcp genes which are located adjacent to each other. In silico analysis reveals genes that have been identified to be involved in the microbial degradation of rubber in the Streptomyces sp. strain CFMR 7. This is the first whole genome sequence of a clear-zone-forming natural rubber- degrading Streptomyces sp., which harbours three Lcp homologous genes with the presence of oxiA and oxiB genes compared to the previously reported Gordonia polyisoprenivorans strain VH2 (with two Lcp homologous genes) and Nocardia nova SH22a (with only one Lcp gene).
Hevea brasiliensis is one of the popular industrial crops in Malaysia better known as rubber tree belongs to the family Euphorbiaceace. From more than 12 species of Hevea, only Hevea brasiliensis is economically exploited because the milky latex extracted from the tree is the primary source of natural rubber. As in other crops, various plant physiological conditions and pathogenic diseases influence rubber production. Brown bast is one of the most serious threats to natural rubber production. In general, high-yielding clones of rubber tree are often considered to be more susceptible to this physiological disorder also commonly termed Tapping Panel Dryness (TPD). It is estimated that brown bast leads to approximately 15-20% decrease in yield. There is no known cure for brown bast yet. However, many plantation practices manage brown bast in rubber by giving tapping rest and changing tapping panel. Hence, this review condenses the causal of brown bast, symptoms of diseases and also control of brown bast affected Hevea tree.
Sulfur has been highly sought by many industries everywhere around the world for various applications. This exceptionally useful element has been largely manufactured especially in powder form each year reflecting its increase in demand in line with technological advancement and uses for various product applications. The manufacturing processes include mining as well as chemical reactions in Claus Process. Rubber industries normally use abundance of sulfur in their latex compound to introduce vulcanization. The geneal concern of sulfur for rubber vulcanization is dispersibility in the rubber matrix due to improper optimization of its preparation process prior to latex compounding. Another crucial issue is crystallization of soluble sulfur from its insoluble origin, either during or post-rubber vulcanization that constitutes to formation of sulfur bloom that grows on the surface of the rubber articles. It is known that both issues are related to the process conditions and compounding recipe that could not be fully solved. Various studies have been conducted to minimize such occurences – from process optimization to sulfur chemistry itself – and of continuous improvement and innovation to solve various threats in sulfur applications. This paper reviews on detailed description on elemental sulfur, of respective industrial applications, and most importantly highlights on sulfur trends and issues normally encountered.
A safety evaluation test on human for latex films made from Radiation Prevulcanized Natural Rubber Latex (RVNRL) with sulfur-containing antioxidant was studied. Sulfur test has confirmed that there was sulfur compound presence in RVNRL derived from antioxidant used in this study. Two types of safety evaluation test were being adopted which are Patch Test and Modified Draize-95 test and this test proved that there is no clinical evidence on the presence of sulfur compound in RVNRL that may induce Type IV allergy in the unsensitized general user population. Both clinical test shows that the highest score value produced by test subjects is 1 and not exceed the allowable limit.
Hevea brasiliensis, a member of the Euphorbiaceae family, is the major commercial source of natural rubber (NR). NR is a latex polymer with high elasticity, flexibility, and resilience that has played a critical role in the world economy since 1876.
Potato starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of potato starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was cast into film by solvent evaporation method. The composite samples were successfully prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex. The morphology of the nanocomposite prepared was analyzed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM analysis revealed the size and shape of the crystal and their homogeneous dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with filler content. The mechanical properties of the nanocomposites such as stress-strain behavior, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties.
The slow-release mechanism of copper into soil followed by soil biodegradation was studied using the chitosan (CTS)/epoxidized natural rubber (ENR) biocomposite. The biocomposite was prepared by homogenizing CTS in ENR50 (ENR with about 50% epoxy content) latex in the presence of curing agents and acetic acid. It was found that the adsorption property of the biocomposite was very much influenced by chitosan loading, where 20phrCTS-t-ENR biocomposite can absorb 76.31% of Cu(II) ions. The desorption study indicates that the copper (II) ion can be released at a very slow and control phase as proven by the kinetic study using zero-order, first-order, Higuchi, and Korsmeyer Peppas equations. The slow-release studies comply with the Higuchi square-root equation, indicating that the release process is diffusion-controlled. Results of desorption and biodegradation process suggest that this biocomposite has the potential use of being a slow-release matrix in the field of agriculture.
This study aimed at investigating the biohydrogen and biomethane potential of co-digestion from palm oil mill effluent (POME) and concentrated latex wastewater (CLW) in a two-stage anaerobic digestion (AD) process under thermophilic (55 ± 3 °C) and at an ambient temperature (30 ± 3 °C) conditions, respectively. The batch experiments of POME:CLW mixing ratios of 100:0, 70:30, 50:50, 30:70, and 0:100 was investigated with the initial loadings at 10 g-VS/L. The highest hydrogen yield of 115.57 mLH2/g-VS was obtained from the POME: CLW mixing ratio of 100:0 with 29.0 of C/N ratio. While, the highest subsequent methane production yield of 558.01 mLCH4/g-VS was achieved from hydrogen effluent from POME:CLW mixing ratio of 70:30 0 with 21.8 of C/N ratio. This mixing ratio revealed the highest synergisms of about 9.21% and received maximum total energy of 19.70 kJ/g-VS. Additionally, continuous hydrogen and methane production were subsequently performed in a series of continuous stirred tank reactor (CSTR) and up-flow anaerobic sludge blanket reactor (UASB) to treat the co-substate. The results indicated that the highest hydrogen yield of POME:CLW mixing ratio at 70:30 of 95.45 mL-H2/g-VS was generated at 7-day HRT, while methane production was obtained from HRT 15 days with a yield of 204.52 mL-CH4/g-VS. Thus, the study indicated that biogas production yield of CLW could be enhanced by co-digesting with POME. In addition, the two-stage AD model under anaerobic digestion model no. 1 (ADM-1) framework was established, 9.10% and 2.43% of error fitting of hydrogen and methane gas between model simulation data and experimental data were found. Hence, this research work presents a novel approach for optimization and feasibility for co-digestion of POME with CLW to generate mixed gaseous biofuel potentially.
The National Blood Center, Kuala Lumpur interprets laboratory results for the von Willebrand factor (vWF) profile based on guidelines provided by the U.S. National Heart, Lung, and Blood Institute, which were established based on the Caucasian population [1-2]. The vWF profiles among the Malay population has not yet been established.
The goals of this study were to determine the vWF profiles of the different ABO blood types among Malays and to evaluate their association with demographic characteristics and smoking habits.
One hundred and forty Malay donors participated in this study. Factor VIII (FVIII), vWF antigen, and ristocetin cofactor (RiCof) levels and collagen binding activity (CBA) were measured by coagulometric clot detection, latex agglutination, and enzyme-linked immunosorbent assay.
Adhesives serve many functions in daily life, starting from sticking envelopes to rejoining broken
materials. Adhesives are usually developed for a specific purpose and the performances can vary
according to their specific end-use. Most of the commercially available adhesives comprised nonrenewable or petroleum derived raw materials. Thus, in order to mitigate negative impact of using nonrenewable material as the raw material for adhesives, a new type of adhesive containing epoxidised
natural rubber (NR) latex is developed. Epoxidised NR latex adhesive was initially prepared and pigment
was subsequently added to produce desired colours of the adhesive. Hence, the newly developed adhesive
can serve as adhesive and also as paint for art. The adhesives were characterised and the results indicated
that they were free from heavy metal contents and volatile organic compounds (VOCs). The adhesives
exhibited comparable odour concentration to commercial synthetic-based adhesive. In terms of toxicity
level, the adhesive developed exhibited low acute oral toxicity. Peel adhesion test of A4 and drawing
papers on stainless steel and glass substrates, opacity and glossiness were also investigated in the present
study. This coloured adhesive is deemed to support the STEM (science, technology, engineering and
mathematics) learning by indirectly imparting polymer science and technology in art education and
further promotes creative learning among school children. The adhesive is also derived from renewable
material rendering it more environmentally friendly.
Enterotoxigenic Bacillus cereus was detected in cooked foods (17), rice noodles (3), wet wheat noodles (2), dry wheat noodles (10), spices (8), grains (4), legumes (11) and legume products (3). One hundred ninety-four (42.3%), 70 (15.3%) and 23 (5.2%) of the 459 presumptive B. cereus colonies isolated from PEMBA agar were identified as B. cereus, Bacillus thuringiensis and B. mycoides, respectively. B. cereus isolates were examined for growth temperature, pH profile and enterotoxin production using both TECRA-VIA and BCET-RPLA kits. One hundred seventy-eight (91.8%) and 164 (84%) of the strains were enterotoxigenic as determined using TECRA-VIA and BCET-RPLA, respectively. Eighty-two (50%) of the enterotoxigenic strains were capable of growing at 5 degrees C, and 142 (86.6%) grew at 7 degrees C within 7 days of incubation. The enterotoxigenic strains did not grow at pH 4.0 but 69 (42.0%) of the strains were able to grow at pH 4.5 within 7 days at 37 degrees C. The isolates were resistant to ampicillin (98.8%), cloxallin (100%) and tetracycline (61.0%), and susceptible to chloroamphenicol (87%), erythromycin (77.4%), gentamycin (100%) and streptomycin (98.7%).
Latex, a milky substance found in a variety of plants which is a natural source of biologically active compounds. In this study, Latex was collected from raw Carica papaya and was characterized using UV-Vis, FTIR and GC-MS analyses. Super Paramagnetic Iron Oxide Nanoparticles (SPIONs) were synthesized, coated with C. papaya latex (PL-Sp) and characterized using UV-Vis, FT-IR, SEM-EDX, XRD, VSM and Zeta potential analyses. SPIONs and latex coated SPIONs (PL-Sp) were used in batch adsorption study for effective removal of Methylene blue (MB) dye, where (PL-Sp) removed MB dye effectively. Further the PL-Sp was used to produce a nanoconjugate loaded with curcumin and it was characterized using UV-Vis spectrophotometer, FT-IR, SEM-EDX, XRD, VSM and Zeta potential. It showed a sustained drug release pattern and also found to have good antibacterial and anticancer activity.
As synthetic antioxidants that are widely used in foods are known to cause detrimental health effects, studies on natural additives as potential antioxidants are becoming increasingly important. In this work, the total phenolic content (TPC) and antioxidant activity of Ficus carica Linn latex from 18 cultivars were investigated. The TPC of latex was calculated using the Folin-Ciocalteu assay. 1,1-Diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and ferric ion reducing antioxidant power (FRAP) were used for antioxidant activity assessment. The bioactive compounds from F. carica latex were extracted via maceration and ultrasound-assisted extraction (UAE) with 75% ethanol as solvent. Under the same extraction conditions, the latex of cultivar 'White Genoa' showed the highest antioxidant activity of 65.91% ± 1.73% and 61.07% ± 1.65% in DPPH, 98.96% ± 1.06% and 83.04% ± 2.16% in ABTS, and 27.08 ± 0.34 and 24.94 ± 0.84 mg TE/g latex in FRAP assay via maceration and UAE, respectively. The TPC of 'White Genoa' was 315.26 ± 6.14 and 298.52 ± 9.20 µg GAE/mL via the two extraction methods, respectively. The overall results of this work showed that F. carica latex is a potential natural source of antioxidants. This finding is useful for further advancements in the fields of food supplements, food additives and drug synthesis in the future.
Health care workers have been reported to constitute one of the few high-risk groups related to IgE-mediated hypersensitivity associated with the use of latex products. This paper describes the first ever study of prevalence carried out in Malaysia among these workers. One hundred and thirty health care personnel from Hospital Kuala Lumpur were skin tested. Extracts used were prepared from seven different brands of natural rubber latex gloves with varying levels of extractable protein (EPRRIM). Out of the 130 volunteers, 4 (3.1%) had positive skin test to latex with extracts with high levels of EPRRIM (> 0.7 mg/g). The prevalence among the Malaysian health care workers can be considered to be low in comparison to that of some consumer countries as the USA which reported a prevalence of as high as 16.9%.
Determination of Streptococcus pneumoniae serotypes is essential for epidemiological surveillance. Therefore accurate, reliable and cost effective serotyping method is crucial. In this study, we determined the serotypes of 41 pneumococcal isolates recovered from human anterior nares by multiplex Polymerase Chain Reaction (PCR) utilizing published primers. The data was then compared with conventional serology using latex agglutination (LA) and the Quellung reaction. Based on the PCR-approach, 8 different serogroups/serotypes were detected with one isolate classified as non-typeable (cpsA-negative). In reference to the serology-based data, the results were in agreement except for one isolate. For the latter isolate, the LA and Quellung tests failed to show a reaction but the PCR-approach and sequencing identified the isolate as serogroup 15B/C. Based on this experimental setting, we found that the PCR-approach for pneumococcal serotypes determination is reliable to serve as the alternative for determining the pneumococcal serotyping.
Peroxide pre-vulcanized natural rubber latex prepared by using gamma irradiation technique is an alternative over the conventionally prepared peroxide pre-vulcanized that used activator to promote the peroxide decomposition in natural rubber latex. Through this technique the problems aroused by some activators such as tends to darken the natural rubber latex film during the drying process can also be overcome. For this preliminary study, data obtained from crosslink density and mechanical measurements were used to evaluate the effectiveness of gamma irradiation in the vulcanization process. Increasing the quantity of tert-butyl hydroperoxide (t-BHPO) from 0.1 pphr to 0.3 pphr while the irradiation dose maintain at 12 kGy has successfully delivered peroxide vulcanized natural rubber latex films with average tensile strength, modulus @ 500% and modulus @ 700% around 15.33, 1.01 and 3.42 MPa, respectively. The effective pre-vulcanization irradiation dose with respect to maximum crosslinking density (85.8 %) was observed on film prepared at 0.1 pphr t-BHPO.
Radiation pre-vulcanised natural rubber latex (RVNRL) prepared by using gamma irradiation technique has many advantages over the conventionally prepared sulphur pre-vulcanised natural rubber latex (SPVL). Despite the fact that many potential latex dipped products can be made from RVNRL, little effort was made to fully commercialise the products because of the inferior strength of RVNRL products compared to SPVL products. An attempt was made to improve the tensile strength of RVNRL by combining both radiation and peroxide vulcanisation in order to ensure that the products will not tear or fail, and has sufficient stretch. Hexanediol diacrylate (HDDA) plays the main role as sensitizer during radiation vulcanisation and tert-butyl hydroperoxide (t-BHPO) as the co-sensitizer in peroxide vulcanisation. Pre-vulcanised natural rubber latex dipped films via hybrid radiation and peroxidation vulcanisations obtained showed tensile strength of 26.7 MPa, an increment of more than 15% compared to controlled film (22.5 MPa). Besides, the crosslink percentage of the rubber films also showed around 5% increment from 90.7% to 95.6%.
Synthetic adhesives used in the production of plywood are a matter of concern because of the emission of carcinogenic gas formaldehyde, increased environmental pollution, and the depletion of fossil fuels. In this study, a bioadhesive composed of natural rubber latex (NRL) and rice starch was developed. However, rice starch has low moisture resistance, resulting in low adhesion. Thus, to enhance the effectiveness of NRL-blended rice starch-based bioadhesive, rice starch was cross-linked with polymeric 4,4″-diphenylmethane diisocyanate (pMDI) resin, which is an environment-friendly, formaldehyde free, and moisture resistant that is highly compatible with starch. The chemical interaction, viscosity, solid content, and gel time of the developed NRL-isocyanate cross-linked rice starch-based bioadhesive was investigated. The efficacy of the formulated bioadhesive was demonstrated by the fabrication of plywood. The presence of isocyanate and urethane capabilities in the bioadhesive formulations was confirmed by Fourier transform infrared spectroscopy (FTIR). The bioadhesive type Iso-A was discovered to have the highest viscosity of 8270 mPa.s, whereas Iso-B has the shortest gel time of 3.46 min and the highest solid content of 44%; the higher solid content accelerates the gel time. In terms of physical and mechanical properties of plywood, Iso-B has the lowest thickness swelling (TS) value of 13%, lowest water absorption (WA) value of 52% and shear strength value of 1.92 MPa, which corresponds to the ISO 12466-2-2007 standard requirements. Based on the results, NRL-blended isocyanate starch-based bioadhesive could be a good potential raw material for eco-friendly plywood industries with adequate accuracy.