Advanced Materials Research Vol. 1024

Abstract: In this work, a type of hydrogel from waste linear low density polyethylene (LLDPE), acrylic acid (AA), and starch was prepared using N, N-methylenebisacrylamide (MBA) as the crosslinker, and benzoyl peroxide as the initiator. The hydrogel was characterized by Fourier transform infrared spectroscope (FTIR), scanning electron micrograph (SEM), and X-ray diffraction (XRD). The results confirmed the incorporation of acrylic acid and starch in the LLDPE chain. SEM results show that the prepared hydrogel has a porous structure. Product showed maximum water absorbency of 180 g/g in distilled water.

Abstract: This paper presents results from a series of experiments in which two combinations of polymer-dye film were exposed to ionizing radiation (electron beam). These experiments were performed for the purpose of investigating the possibility of polyethylene (PE) and polyvinyl chloride (PVC) with and without the addition of malachite green (MG) dye for radiation indication in the form of colour transition. MG dye was also inspected whether it has experienced the photodarkening from the exposure to ionizing radiation. The experiments were carried out using samples in the form of film. From this study, it was proven that the polymers and dye do not work alone to give the change. Halogen-containing polymer was found positive in stimulating the acid-sensitive dye for the transition of colour. The colour transition of the combination of PVC/MG without pH adjustment was consistently increasing with irradiation level. The transition is observed even at 100 kGy of the radiation exposure. Samples with the addition of basic solution have a rapid change in terms of colour but the limit of sensitivity was decreased to only 20 kGy of radiation exposure.

Abstract: Non-woven kenaf fiber mats were prepared from untreated and alkali treated fibers by using a carding machine followed by needle punching. The alkali treatment was carried out by immersing the fiber mats in 6% NaOH solution for 0, 1, 2, 3, 4, and 5 h at room temperature. The untreated and alkali treated fiber mats were impregnated with unsaturated polyester resin via a resin transfer molding technique to form composites. Maximum improvements of flexural strength and flexural modulus of the composites were observed when the fiber mat was alkali treated for 3 h. The improved of both properties can be attributed to better fiber-matrix adhesion between the alkali treated kenaf fiber and the unsaturated polyester matrix most probably via mechanical interlocking. Water absorption tests were conducted by immersing the composite samples in distilled water at room temperature. The water absorption patterns of all the composites were found to follow Fickian behavior. The tendency of the composites to absorb water decreased when the alkali treated fiber mats were used.

Abstract: Since the introduction of the so-called Green Tyre concept, in the early 90ies, the use of silica as reinforcing fillers has spread and grown worldwide. The general advantages of silica as reinforcing filler over carbon black filler are better rolling resistance by achieving at least equal wet traction while tread wear should not be adversely affected. One way to obtain both low rolling resistance and high wet traction is indeed, to use precipitated silica together with solution polymers in tyre treads. The benefits of reinforcement by silane coupled silicas, in certain blends of solution styrene –butadiene rubber (SBR) and butadiene rubber (BR), were recognized by major tyre manufacturer. However, the use of silica compounds entails considerable disadvantages in terms of raw material costs and processability (before vulcanization). These difficulties include higher compound Mooney Viscosity (ML1+4) that increases upon storage, short scorch time and environmental problems related to alcohol evolution. The high viscosity and poor processability in silica filled rubber compounds are believed to be associated with silica reaggregation (self aggregation) after rubber compounding. The study has been made of the effect of increased mixing stage and dispersion agent in rubber on uncured properties of the Silica Filled Epoxidised Natural Rubber Compounds. In this experiment, two orders of mixing were considered (1) Two Stages Mixing and (2) Three Stages Mixing. Results showed that filler dispersion, Mooney Viscosity and Payne Effect was influenced by the degree of mixing. The incorporation of dispersion agents in the compounds also resultant in the similar manner. It is believed that the dispersion agent could coat the silica surfaces as they are being broken down during the mixing and then stabilize the dispersed structure by stearically preventing silica reagglomeration.

Abstract: Poly (L-lactic) Acid (PLLA) is one type of degradable polymer which mostly used for bioplastic. PLLA has strength and modulus comparable with another commercial polymer and not degrade in general environment, however PLLA exhibits brittle fracture. In the present study, blending between PLLA with other polymers was carried out to improve the brittleness of PLLA resin. Polymers that been used in the blending process are synthetic rubber, waste rubber, acrylonitrile butadiene styrene (ABS) and polylactic acid microsphere. Blend ratio (98/2) was considered in the study . The tensile properties and morphology was investigated using tensile testing and field emission scanning electron microscope (FE-SEM). It was found that the addition of PLA microsphere shows the highest tensile strength and elongation at break and good Youngs modulus. While waste rubber and synthetic rubber exhibit the lowest tensile properties. In general, it is found that the toughness of PLLA can be improved by blending method.

Abstract: The addition of starch in natural rubber (NR) latex films tends to decrease the mechanical properties of NR latex films due to poor dispersion of the fillers. As an alternative, starch was gelatinized before being added into NR latex compounds. The dispersion of 10% starch was mechanically prepared through ball milling together with dispersing agent. The other dispersion of 10% starch was gelatinized using alkali. The influenced of ball milled starch and alkali gelatinized starch filled NR latex films were studied through scanning electron microscopy, tensile properties, tear strength, and swelling properties. The rough freeze fracture surface with less agglomeration of fillers was observed on the alkali gelatinized starch NR latex films. The NR latex films filled with alkali gelatinized starch showed improvement in tensile properties, tear strength, and swelling resistance compared to the ball milled starch NR latex films. It can be concluded that the alkali gelatinization improved the dispersion of starch in NR matrix thus enhanced the mechanical properties of NR latex films.

Abstract: Mould cleaning process is the process of removal build-up deposited or residue material on the mould surface after repeated cycles of production. The currently used mould cleaning process is sand blasting (abrasive process) and dry rubber mould cleaning compounds (depends on the skill of the operators during rubber compounding). Latex laminated compounds will be beneficial as a new substitute for mould cleaning because of its excellent strength properties and the lamination process to increase its thickness. The main focus of this research is to investigate the effect of lamination process on mechanical properties and mould cleaning efficiency of laminated Nitrile Butadiene Rubber (NBR) latex composites. Laminated NBR latex films with cleaning agent and waste latex compound was prepared by arranging half-cured latex sheets with various thicknesses of outer layer (NBR latex films with cleaning agent) and core layer (waste NBR latex film). The core and outer layers are prepared through casting method with different thickness. The laminated films were subjected to compression moulding using hot press at 120°C. Reinforcement of the core layer gives laminated latex composite with better mechanical properties, but excessive of core layer portion reduced the mechanical properties of laminated films. The efficiency of mould cleaning of laminated NBR latex films were depends on the flow ability and adhesion properties of the fresh latex layer with mould cleaning agent (outer layer).

Abstract: The molecular weight of natural rubber (NR) can be reduced via depolymerization reaction to produce liquid natural rubber (LNR) with a molecular weight less than 50 000 g/mol. In the reaction, hydrogen peroxide and sodium nitrite were added to natural rubber latex to initiate a redox type reaction which then breaks the NR chain. Low permeation of reagents into latex particles allows the degradation to occur greater at the latex particle surface relative to the inner core contributes to high molecular weight distribution (MWD) or polydispersity of the LNR obtained. In this recent works, the reaction was carried out in a biphasic medium consisting of water and toluene phases. Toluene swells latex particles as indicated by the SEM micrographs showing changes in the size of latex particles. This occurrence is suggested to increase the influx of reagents into the latex particles. Consequently, with higher permeation of reagents into the latex particles resulted in the decrease of molecular weight and lower polydispersity of the LNR obtained. Chemical structure analysize showed that the LNRs obtained were attached with hydroxyl and carbonyl groups.

Abstract: Palm oil is one of the main raw materials available in the country. Hence, the diversification ofpalm oil derivatives into new products has been given priority. The development of new radiation curable materials for applications in radiation ultraviolet (UV) or electron beam (EB) curing technology is an important research area. The hyperbranched curable polyurethane acrylate (HBPUA) from oleic acid of palm oil has been synthesized through a three-step reaction. Dipentaerythritol was initially reacted with 2, 2-bis (hydroxymethyl) propionic acid in a solution medium aided by p-toluene sulfonic acid as a catalyst to form hyperbranched polyol polyester first generation (HBP-1). HBP-1 then used as the core and reacted with palm oil oleic acid to form the hyperbranched polyol polyester second generation (HBP-2). HBPUA was prepared by reacting HBP-2 resin with diisocyanate and hydroxyl-containing acrylate monomer with the presence of 0.1-2 wt% dibutyltin dilaurate as a catalyst. The reaction was confirmed by several analytical data namely hydroxyl value (OHV), fourier transform infrared (FTIR), gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) analyses. The HBPUA was easily curable when subjected to EB radiation. The thermal decomposition of HBPUA showed good thermal stability up to 450 oC.

Abstract: This paper reports on the compatibility of waste rubber binder combined with conventional binder, paraffin wax and local binder, palm stearin for M2 High Speed Steel injection molding in order to obtain the better properties. The feedstock was prepared at a powder loading of 65 vol.% using 22um M2 High Speed Steel powder and the binders consisting of 55wt.% paraffin wax/palm stearin, 21wt.% polyethylene, 14wt.% waste rubber and 10wt.% stearic acid. The specimens were then sintered in vacuum atmosphere within a temperature range from 1200°C to 1260°C. The results shown even the best properties is obtain from the conventional binders, paraffin wax, thus the properties of local binders palm stearin is still comparable and good. The maximum density of paraffin wax binder was 8.095g/cm³ achieved at temperature 1250°C and palm stearin binder was 8.111g/cm³ achieved at temperature 1240°C. Therefore, in term the best strength of paraffin wax was 2351Mpa whilst palm stearin was 2210MPa, both recorded at temperature 1230°C.