Key Engineering Materials Vol. 659

Abstract: Rubber processing oil based on modified epoxidized vegetable oils (m-EVO) was prepared by a reaction of epoxidized palm oil EPO) or epoxidized soybean oil (ESBO) with N-Phenyl-ρ-phenylenediamine (PPD) at a mole ratio of 1:0.5. The comparison of m-EVO with aromatic oil (Treated distillate aromatic extract, TDAE) on extrusion process behaviors (output rate, extrusion rate, screw efficiency, heat generation, die swell, extrudate appearance) of carbon black (N330) filled natural rubber (NR) compound was made. It was found that the mooney viscosity of m-EVO based natural rubber compounds are slightly higher than that of the TDAE based natural rubber compound (ML(1+4)100°C: m-ESBO 65.5±0.7; m-EPO 59.7±0.2; TDAE 56.5±1.0), which probably due to the poorer filler dispersion in the compounds. The extrusion process behaviors for output rate (g/min: m-ESBO 191.0±0.6; m-EPO 191.2±0.4; TDAE 195.5±0.6), extrusion rate (cm³/min: m-ESBO 179.6±0.6; m-EPO 183.2±0.4; TDAE 186.4±0.6) and screw efficiency (%: m-ESBO 30.8±0.6; m-EPO 31.4±0.4; TDAE 32.0±0.6). All the three compounds show similar extrusion process behaviors in which the TDAE based compounds shows a marginal higher values than the m-EVO as its lower mooney viscosity lead to a better flow. The m-EPO and m-ESBO based natural rubber compounds show very similar extrusion process behaviors. The heat generation (°C: m-ESBO 61.0±0.8; m-EPO 62.1±0.4; TDAE 63.1±1.0) and die swell (%: m-ESBO 11.0±0.7; m-EPO 11.0±0.5; TDAE 12.7±0.3) of the m-EVO based natural rubber compounds are slightly lower than those of the TDAE based natural rubber compound. As there are no significant differences in the extrusion process behaviors, with respect to extrusion process, m-EVO can be used to replace TDAE oil.

Abstract: This research was aimed to study the possibility of in-situ reinforcement of PLA by elongated Nylon 6 in PLA/Nylon 6 blend during elongating of PLA/Nylon extrusion. PLA was melt blending with Nylon 6 in a twin screw extruder with various compositions i.e. 5, 10, 15 and 20 % of Nylon 6. The extrudate was drawn after leaving extrusion orifice die of 3 mm in diameter, with the pulling speed of 12 cycles per minute. The extrudate gauge length 15 cm were used to perform tension test in order to investigate tensile properties. The blending between PLA and Nylon 6 with 11 phr of benzene sulfonamide (BSA), based on Nylon 6, as a plasticizer was also investigated at the same PLA/Nylon 6 blend ratios. The extrusion used conditions were also the same. Tension was also performed onto the extrudates with the gauge length 15 cm. Thermal degradation was also investigated. The SEM micrographs of blends in the longitudinal direction of PLA/Nylon 6 extrudate showed elongated of Nylon 6 in PLA matrix phase. The elongated of Nylon 6 phase in PLA matrix phase was found very clear in the plasticized blends. This phenomenon clearly occurred for the blends composition of both 95/5 and 90/10, with and without plasticizer. The results also showed that Young’s modulus of the blends with 5 % Nylon 6 was increased about 10 % whereas at 10 % nylon 6, the modulus was not significantly different from neat PLA. With the addition of plasticizer, nylon 6 was elongated more than that in the blend with un-plasticized Nylon 6. Due to the lack in interfacial adhesion, shown by SEM micrograph, tensile strength was found to be decreased. As expected, the elongation at break under tension was increased with the content of nylon 6. This was due to the toughening effect of elongated Nylon 6. Thermal stability, notified by degradation temperature of PLA, T_d, was found to be improved. This was due to the high thermal stability of nylon 6. The results from the research can inform that the elongated nylon 6 phase in PLA matrix can perform as fibrous reinforcement. At high content of nylon 6, i.e. 15 and 20 %, the elongation of nylon 6 was rather difficult due to the less matrix phase and low shearing between PLA and nylon 6. Phase compatibility improvement could be the factor to improve the in-situ reinforcement.

Abstract: This research aims to investigate synthesis parameters for modification of chitosan with enrofloxacin. Most modifications of chitosan are focused on amino group. There are many methods for modification of chitosan, for example, conjugation of amino group with carboxylic group by coupling agents. 1-Ethyl-3-(3-(dimethylamino) propyl) carbodiimide hydrochloride (WSC) and N-hydroxysuccinimide (NHS) are widely used coupling agents for amide formation under mild conditions. Those two coupling agents were applied in this study. Optimum amount and ratio of coupling agents, amount of enrofloxacin and reaction times were investigated. The chemical structures were characterized by Fourier transform infrared spectroscopy (FT-IR). The optimum synthesis conditions were determined from the absorbance ratios. Chitosan-enrofloxacin has antibacterial activity against both S. aureus and E. coli.

Abstract: Hemp fiber reinforced composites was prepared using high density polyethylene (HDPE). Hemp fiber is a cellulosic fiber. It is used as reinforcement in thermoplastic matrix composite requires knowledge of their morphology and structure. In this paper, mechanical properties of chemically treated fiber reinforced HDPE composites were investigated over range of fiber content (0-50 wt%). The hemp fiber was alkali treated with 1-10 wt% to remove waxes and non-cellulosic surface components and triethoxyvinyl silane treated with 0.5-3 wt% to improve a better fiber-matrix interface. Fiber/matrix adhesion was assured by the use of use of polyethylene-graft-maleic anhydride (PE-g-MA) as a compatibilizer. Scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), Differential scanning calorimetry (DSC), X-Ray Diffraction (XRD) and tensile tests were carried out for hemp fibers high density polyethylene composite. Findings indicate that a 5 wt% NaOH treatment effectively improved the fiber-matrix interface resulting in improved mechanical properties. All 40 wt% alkali treated fiber reinforced HDPE composites displayed higher young’s modulus and lower elongation at break as compared to neat HDPE, compatibilization with PE-g-MA resulted in an increased young modulus of the composites as consequence of an improved fiber-matrix interfacial adhesion.

Abstract: In this work, the mechanical and thermal properties of pineapple leaf fiber (PALF)/poly (lactic acid) (PLA) composites were studied. Pineapple leaf fibers were pretreated with 4 %wt sodium hydroxide solution followed by various silane solutions i.e. γ-(aminopropyl) trimethoxy silane (APS), γ-methacrylate propyl trimethoxy (A174) and bis [3-(triethoxysilyl) propyl] tetrasulfide (Si69). FTIR results show a significant functional groups of C=O and C=C of methacrylic group, NH₂ group and Si-O which are the characteristic of these silane coupling agents. SEM micrographs of pretreated PALF showed a rough surface while untreated and silane treated PALF revealed less roughness. It was found that the tensile strength at break of PLA is 56 MPa and tensile strength of composites decreased when fiber content increased. The tensile modulus of silane treated PALF composites were higher than PLA, whereas their impact strength were similar to PLA. Si69 treated PALF showed lower impact strength compared to the others silanes treated fiber which indicates more phase separation between fiber and matrix. This is related to high percentage of crystallinity of composite from Si69 treated fiber. It was also found that the addition of PALF did not change the glass transition temperature and melting temperature of PLA while the percentage of crystallinity increases as the fiber content increased. In addition WAXS study of composite from Si69 treated fiber reveals sharp crystalline peaks of PLA while the others silane treatments show amorphous characteristic of PLA.

Abstract: Pineapple leaf microfibers were firstly prepared using steam explosion, and all-cellulose composites were subsequently prepared using a surface selective dissolution process with the solvent of lithium chloride and N,N-dimethylacetamide (LiCl/DMAc). Mechanical properties and surface morphology of all-cellulose composites with immersion times of pineapple leaf microfibers in the solvent of LiCl/DMAc were investigated using tensile testing and scanning electron microscopy, respectively. The tensile strength of the all-cellulose composites with 120 min-immersion time was approximately 28 times higher than that of the pineapple leaf microfiber mats. These biocomposites made from pineapple leaf microfibers could be one of the potential alternatives to replace glass fiber reinforced composites.

Abstract: Natural rubber (NR) latex collected from Hevea brasiliensis rubber tree exists as a colloidal suspension with 30% dry rubber content (DRC). For convenient use and transportation, the latex is concentrated by centrifugation process. Through this process, the 60% DRC concentrated NR latex and 5% DRC skim latex as a by-product were produced. After using acid coagulation of skim latex, the skim rubber is obtained to use as a low-grade application due to high amount of non-rubber components as impurities. The water portion remaining after the coagulation of skim rubber consists of various water-soluble materials such as sugars, lipids, proteins and minerals, which can cause the water pollution if serum is directly discharged into the environment without proper treatment. However, 1.5% of L-quebrachitol was found in skim latex. It can be used in many applications such as a starting material for the synthesis of bioactive materials and inositol pharmacy. Thus, this work is an attempt to investigate the most effective extraction method of L-quebrachitol from skim latex. It was found that the appropriate solvent for extraction L-quebrachitol at high temperature and for recrystallization at low temperature is ethanol. The yield of L-quebrachitol about 2-3% by weight of solid serum was obtained. Moreover, a sweetness and antibacterial activity were also studied for its further applications. It was found that the sweetness of L-quebrachitol was twice than that of sucrose. No antibacterial activity of L-quebrachitol against Staphylococcus aureus and Streptococcus mutans was found.

Abstract: The effects of polypropylene-graft-maleic anhydride (PP-g-MA) compatibilizers on the morphology and mechanical properties of polyoxymethylene (POM)/acrylonitrile-butadiene-styrene (ABS) blends were investigated. Two types of compatibilizers, PP-g-MA with maleic anhydride 0.50 wt% (PP-g-MA1) and PP-g-MA with maleic anhydride 1.31 wt% (PP-g-MA2) were used to study the interfacial adhesion of POM and ABS. POM/ABS blends with and without PP-g-MA compatibilizer were prepared by an internal mixer and molded by compression molding. Scanning electron microscope (SEM) was used to investigate the morphology of ABS phase in POM matrix. The results found that POM/ABS blends clearly demonstrated a two phase separation of dispersed ABS phase and the POM matrix phase, and ABS phase dispersed as spherical domains in POM matrix in a range of ABS 10-30 wt% and the blends containing ABS more than 30 wt% showed the elongated structure of ABS phase. The addition of PP-g-MA could improve the interfacial adhesion of POM/ABS blends due to the domain size of ABS phase decreased after adding PP-g-MA. The mechanical properties showed that the impact strength of POM/ABS blends decreased in a range of 10-20 wt% and did not change after 20 wt%. The addition of PP-g-MA did not change the impact strength of POM/ABS blends. The Young’s modulus of POM/ABS blends increased up to 30 wt% of ABS and then decreased. While the blends showed the decrease of tensile strength and percent strain at break with increasing ABS content. The addition of PP-g-MA increased the tensile strength of POM/ABS blends in a range of 30-40 wt% of ABS. The above results indicated that the morphology had an effect on the mechanical properties of polymer blends.

Abstract: The objective of this research was to examine the synergistic effect of organomodified nanoclay and fire retardants on the thermal decomposition, glass transition temperature and fire retardation behaviour of nanoclay/Poly vinyl ester composites. The two nanoclays such as Cloisite-15A and Cloisite-Na are used along with two fire retardants as Aluminium Tri Hydroxide (ATH) and Magnesium Hydroxide (MH) in the present study. The nanoclay/fire retardants were dispersed in poly vinyl ester using twin screw extrusion. TEM and AFM of nanoclay/Poly vinyl ester specimens revealed that 4 wt% Cloisite-15A/Poly vinyl ester exhibited exfoliation and distribution of nanoclay which were superior to that of Cloisite-Na/Poly vinyl ester. The synergistic effect of Cloisite-15A and 30 % ATH increased glass transition temperature by 18 % and reduced thermal degradation by 47 % and Limiting Oxygen Index (LOI) by 52 % when compared with that of Poly vinyl ester after the curing process in all the cases.

Abstract: Titanium dioxide (TiO₂) is normally added into the rubber compounds as a white pigment and inorganic filler for an improvement of thermal property. TiO₂ is also known to have an outstanding photocatalytic activity. This work investigates the properties of natural rubber (NR) compounds filled with 5 phr of nanoTiO₂ (n-TiO₂). Since the direct incorporation of n-TiO₂ into NR encounters incompatibility problem, therefore two types of coupling agent (i.e. bis-(3-triethoxysilylpropyl) tetrasulfide (TESPT) and isopropyl trioleyl titanate (ITT)) are used. The coupling agent loading is varied in a range of 0-20 wt% relative to the n-TiO₂. Mooney viscosities and minimum cure torque (M_L) of the compounds increase with increasing coupling agent content and the ones with ITT show higher viscosity than the mixes with TESPT. The use of TESPT leads to shorter optimum cure time and higher torque difference compared to the use of ITT. The addition of n-TiO₂ results in the improved modulus, reinforcing index and tensile strength compared to the unfilled vulcanizate. The presence of both TESPT and ITT significantly reduces a photodegradation efficiency. The difference in the properties and photocatalytic activity of n-TiO₂ filled NR having TESPT and ITT as coupling agent indicates their possible different level of dispersion and interactions at the interphases.