Ekachai Wimolmala

Wood sawdust fibres as a secondary filler in carbon black filled NR vulcanizates

Studies into the properties of polymer-wood composites (PWC) are mostly focused on thermoplastics as the matrix phase and wood flour as a reinforcing phase. This article aims to identify the optimum contents of wood sawdust fibre and silane coupling agent to be introduced into natural rubber (NR) compounded with carbon black (CB). The authors have considered a wide range of composite properties, including cure characteristics, % bound rubber, crosslink density, sorption and desorption behaviour, tensile modulus, elongation at break, tensile and tear strengths, hardness, and morphological properties. The results suggest that the overall mechanical properties of the NR composites improved with increasing CB content, but deteriorated sharply with sawdust content up to 40 phr. Addition of further sawdust was recommended as an economical benefit to industries as the properties of the NR/CB composites remained unchanged with increasing sawdust content above 40 phr sawdust fibre. Addition of N-(βaminoethyl)-γ-aminopropyl-trimethoxy silane coupling agent to the NR vulcanisates, containing 40 phr of wood sawdust fibres and 45 phr carbon black at 0.5-1.0 %wt of wood sawdust, improved the mechanical properties. The explanations for the results given in this paper are unique in that they refer to bound rubber, crosslink density and rubber-filler phase continuity in the composites, and to a change in composite rigidity.

Effects of Coir Fiber and Maleic Anhydride Modification on the Properties of Thermoplastic Starch/PLA Composite Laminates

Coir fiber reinforced composite laminates made of poly(lactic acid) (PLA) with a thermoplastic starch (TPS) were fabricated. Modified thermoplastic starch (MTPS) was prepared by reactive blending of TPS with maleic anhydride (MA). The effect of coir fibers was of our main interest. The tensile properties, water absorption, and morphological properties of the fabricated composite laminates were investigated. The composite laminates between PLA and starch TPS were prepared using coir fiber as reinforcing core, and the physical, mechanical, and morphological properties were studied. The results suggested that the optimum fiber contents for maximum tensile strength for TPS/PLA and MTPS/PLA composites were 20 and 30 wt%, respectively. Using MA for chemical modification of TPS for PLA composites could reduce the PLA content of about 10 wt%, and improve the tensile about 20%. The volume swelling for the MTPS/PLA composites was much lower than that for the TPS/PLA composites, and the swelling reduced with increasing coir fiber content. Based on compressive strength, the pallets produced using MTPS/PLA composites showed a high potential to replace the commercial urea-formaldehyde/PLA composites. It clearly appeared that MA modification to TPS not only improve the mechanical properties of fiber reinforced PLA composites, but also made the PLA composites bio-degrade more quickly.

Effects of solution and solid forms of 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate on antibacterial, physical and mechanical properties of polypropylene sheeting

Two forms of an inorganic antibacterial agent, 2-hydroxypropyl-3-piperazinyl-quinoline carboxylic acid methacrylate (HPQM), were added into polypropylene sheet. The polypropylene sheet antibacterial, physical, and mechanical performance was assessed before and after exposure to ultraviolet light at different ultraviolet aging times. Water-based HPQM (HPQM-solution) and HPQM in magnesium aluminometasilicate or Neusilin (HPQM-Neusilin) were supplied in liquid and solid powder forms, respectively. Halo test and dynamic shake flask method, together with plate count agar technique, were used for quantitative antibacterial performance analysis; the results were reported as radius of inhibition zone and bacterial reduction. The results suggested that the HPQM-Neusilin samples exhibited more effective antibacterial performance than the HPQM-Solution samples. Adding HPQM-Neusilin considerably changed the polypropylene sheet lightness (L*). Introducing HPQM-solution into polypropylene did not change the polypropylene sheet physical and mechanical properties. Both HPQM forms showed very effective antibacterial performance against E. coli, but not against B. cereus. The minimum HPQM concentration to achieve 99.9% bacterial reduction for HPQM-solution and HPQM-Neusilin samples were 750 and 500 ppm, respectively. The antibacterial efficacies of polypropylene supplemented with HPQM disappeared after 24-h ultraviolet aging.

Use of synthetic fibers as co-reinforcing agents in wood/PVC hybrid composites: effect on tribological properties

Uses of natural wood/PVC composite products are increasing in various fields of construction and in building materials applications. This present work aimed to develop wood/PVC hybrid composite materials by incorporating synthetic fibers, namely E-glass, S-glass, and carbon fibers. Three different wood flours were also considered, including Xylia kerrii Craib & Hutch, Hevea brasiliensis, and Mangifera indica Linn. The mechanical, morphological, and wear properties were of interest. The results suggested that the addition of synthetic fibers significantly improved the flexural properties of wood/PVC composites, but only slightly affected their specific wear rate values, this effect being most pronounced with the incorporation of carbon fiber and when tested at longer sliding distance. The influence of different wood types showed no definite trend on the specific wear rates of the wood/PVC hybrid composites. Among different counterface materials used, a sandpaper counterface resulted in the highest specific wear rate, which involved a two-body abrasion mechanism. The results of this work indicated that S-glass fiber and XK wood were most suitable for co-reinforcing the wood/PVC composites in terms of wear-resistant applications.

Relationship on research publications and productivity-export volumes for natural rubber

This article investigated contributions of natural rubber (NR) research through research articles and patents in Science Citation Index Expanded (SCI-Expanded) and SCOPUS databases and related the results with productivity-export volumes during 2002–2006. 1,771 research papers and 5,686 patents on “natural rubber” were retrieved from the databases. The results revealed that the top five countries produced the NR raw material by the order of productivity volumes were Thailand, Indonesia, Malaysia, Vietnam and China whereas those produced the synthetic rubber were the United States, China, Japan, Russia and Germany. Among the top three countries for NR production, Malaysia became a NR producer for its own use, whereas Thailand and Indonesia still had higher export volumes. Research articles and patents on natural rubber had contribution shares of about 20.9% and 47.5% of all rubber publications, respectively. The patents on natural rubber were found to increase with time while the research articles remained unchanged. Journal of Applied Polymer Science was the most preferable for publishing the research papers on rubbers. Eight countries ranked in the top countries for contributing the research articles on natural rubber were the United States, India, Malaysia, France, Germany, Thailand, Japan and China, similar country distributions being also found for research articles on synthetic styrene-butadiene rubber except for Thailand and Malaysia. No linear relationship between the productivity-export volume and research publication number was observed, but the results implied that the growth rate for commercializing the rubber was greater than that for research and development of natural rubber. Most NR research works focused on neat NR, which was contributed the most by USA while NR blend and NR composite papers were mainly published by Indian researchers.

Antibacterial Efficacy and Mechanical Properties of Silica Reinforced Natural Rubber (NR) with HPQM Based Neusilin

This work studied the antibacterial performance and mechanical properties of natural rubber (NR) compound reinforced with commercial silica at various silica loadings form 0, 20, 40 and 60 parts per hundred rubber (phr). 2-Hydroxypropyl-3-Piperazinyl-Quinoline carboxylic acid Methacrylate (HPQM) based Neusilin at loadings of 0, 3 and 5 phr were used as anti-bacterial agent against Escherichaia coli (E.coli) ATCC 25923 and Staphylococcus aureus (S.aureus) ATCC 25922. The antibacterial performance was reported as a clear zone radius by diffusion test and a percentage reduction of bacteria by Plate-Count-Agar (PCA) method. The results suggested that the increasing silica loading in the NR vulcanizates improved the tensile modulus and hardness, but decreased elongation which had optimal tensile strength at 20 phr of silica. Additionally, the HPQM based Neusilin did not affect the mechanical properties of the rubber vulcanizates. The antibacterial results showed that the inhibition zone radius and the percentage reduction increased with increasing HPQM based Neusilin, but decreased with silica filler content. The antibacterial efficacy was inversely related to the reinforcement level of the NR vulcanizates by the silica. The percentage reduction of bacteria of NR compound filled with 5 phr of HPQM based Neusilin achieved 99.9%.

Antibacterial Ability of HPQM Base Neusilin/Natural Rubber Reinforced with Carbon Black

This work studied antibacterial ability of natural rubber (NR) reinforced carbon black N330 at loadings 0, 20, 40 and 60 parts per hundred rubber (phr) and 2-Hydroxypropyl-3-Piperazinyl-Quinoline carboxylic acid Methacrylate (HPQM) based Neusilin at loadings 0 , 3 and 5 phr were used against Escherichia coli (E.coli) ATCC 25923 and Staphylococcus aureus (S.aureus) ATCC 25922. The Inhibition zone (Disk diffusion) and Plate Count Agar (PCA) methods were employed to assess the ability of the anti-bacterial performance, cure characteristics and mechanical properties such as tensile modulus, tensile strength, elongation at break and hardness. The results suggested that increasing HPQM in appearance of inhibition zone and 99.9 percent reduction of E.coli. The antibacterial ability HPQM base Neusilin at loadings 5 phr and carbon black at loadings 20 phr were better. The antibacterial ability of NR vulcanizates depends on the level of reinforcement. The tensile strength with using 40 phr of carbon black loading was suggested in this work.

Potential use of fly ash and bagasse ash as secondary abrasives in phenolic composites for eco-friendly brake pads applications

Brake pad is the essential component of disk brake in automotive applications that is made of phenolic-based composites. The alumina and silica are often used as primary abrasives in brake pads. In this study, we investigated the hardness, compressive, friction and wear properties under room temperature and elevated temperatures (100°C and 150°C) of phenolic-based composites containing the natural ashes of fly ash and bagasse ash as secondary abrasives, which ranged from 0 to 12 wt%, for replacing primary abrasives. The results suggested that 4 wt% secondary abrasives was recommended for optimization of the overall properties of the composites. It was found that all composites exhibited the abrasive wear behavior evidenced by wear debris between the counterfaces acting as third-body abrasives. The phenolic-based composites at 100°C and 150°C had higher coefficient of friction and lower wear resistance than those at room temperature. The incorporation of bagasse ash resulted in more compression for a given load than that of fly ash. In summary, the fly ash and bagasse ash, which were natural ashes, showed a potential use as secondary abrasives in the phenolic-based composites for eco-friendly brake pads.

Material Formulations for AR/PMMA and AR-TiO2/PMMA Blends and Effects of UV Radiation and Tio2 Loading on Mechanical and Antibacterial Performances

ABSTRACT Polymer blends of poly(methyl methacrylate)(PMMA) and acrylic rubber(AR) were manufactured with the addition of titanium dioxide (TiO2). TiO2 was initially added to the AR phase in AR/PMMA blends. The impact strength of PMMA improved with AR loading. The addition of TiO2 appeared to decrease the tensile properties of the blends with AR of 10-30 wt% of AR, but increased with AR of 40-50 wt%, this being related to distribution level of TiO2. UV radiation deteriorated the overall mechanical properties, where TiO2 could retain the properties. To achieve acceptable antibacterial performance, AR loadings of 40 and 50 wt% in AR-TiO2/PMMA blends are recommended, together with TiO2 loadings of 1.5 pph and 0.5 pph, respectively. GRAPHICAL ABSTRACT

Tribological properties of carbon nanotube as co-reinforcing additive in carbon black/acrylonitrile butadiene rubber composites for hydraulic seal applications

This work investigated the cure characteristic, physical mechanical properties, and tribology behavior of carbon black filled acrylonitrile butadiene rubber composites using multi-walled carbon nanotubes as co-reinforcing additive in various contents from 0, 3, 6, 9, and 15 parts per hundred rubbers. The physical and tribological behavior was also observed in large-scale piston driven hydraulic apparatus which was specially designed for seal applications. The results suggested that the modulus and hardness were found to increase after adding multi-walled carbon nanotube whereas the tensile and tear strength were not significantly affected. Adding multi-walled carbon nanotube was found to increase the bound rubber and crosslink density. For ball-on-disc tribo-testing, it was found that the coefficient of friction of the rubber composites decreased with multi-walled carbon nanotube content and the applied loads whereas the specific wear rate was more influenced by the applied loads used. Finally, under the large-scale piston driven hydraulic test apparatus in comparison with commercial grade rubber seals, it was found that the weight loss for the acrylonitrile butadiene rubber composites with multi-walled carbon nanotube was much lower than that without multi-walled carbon nanotube. The carbon black/acrylonitrile butadiene rubber composites with 9–12 parts per hundred rubbers multi-walled carbon nanotube were recommended as the most suitable for hydraulic seal applications.