Key Engineering Materials Vol. 748

Abstract: A rigid polyurethane (PU) flame retardant composite foam was prepared by the compounding of polyols and diisocyanates with a modified intumescent flame retardant (MIFR). The MIFR was based on the three components of intumescent flame retardant normally used and was modified in a surfactant TX-10 solution. The flame retardancy of the PU flame retardant composite foams were evaluated by using the limiting oxygen index (LOI), the UL-94 (vertical flame) test and scanning electron microscopy (SEM). When MIFR was fixed at 20.0 wt% in PU/MIFR composite foams, the MIFR could enhance the flame retardancy and pass V-0 rating of UL-94 test. The microstructures observed by SEM demonstrate that a suitable amount of MIFR can promote formation of compact intumescent charred layers in PU foams.

Abstract: Fiber reinforced composite material is used widely in oil fields for its high specific strength and resistance to corrosion. Glass reinforced plastics (GRP) and Glass reinforced epoxy (GRE) pipe samples were investigated under oil field conditions. The samples were subjected to ultraviolet radiation, moisture and elevated temperature using accelerating weathering machine and then aged in different environments encountered in oil well streams and characterized by using Scanning Electron Microscopy (SEM). The surface morphology was analyzed and the images produced from wet crude and effluent water has shown different degree of deformation of the glass fiber and debonding with the polymer matrix. The tensile and modulus properties were also evaluated and effect of ageing found to be more pronounced in the case of wet crude especially for the GRE. The study revealed some tendency of GRP samples to reform the polymer matrix interface with the glass fiber after weathering. The assessment of physical properties provided information about the structural stability of composite pipes under harsh environments, which in turn can impact their overall performance and service life.

Abstract: This paper presents flexural properties related to vibration behavior of jute reinforced polyester composite. The goal of the research is to seek green composite material that exhibits good strength and flexural properties along with good damping property designed for wind turbine blades. The material for reinforcement in the present study is jute fiber. The material for matrix is polyester resin. Glass and carbon fiber are used for hybridization. Specimens were fabricated by vacuum infusion technique. Laminates were constructed by stacking jute fiber clothes. Hybrid laminates were fabricated by stacking jute clothes covered by one ply glass cloth and jute clothes covered by one ply carbon cloth. Static flexural and free vibration tests were carried out to obtain the elastic modulus and vibration behavior of specimens, respectively. The result shows that the configuration of jute fiber cloth and glass fiber hybridized laminates possesses compromised properties between flexural properties and damping ratio.

Abstract: The paper investigates the novelty of application of end chills in fabricating Aluminum alloy metal matrix composites. An effort has also been made to evaluate the effect of chill material on the soundness of the castings obtained. The required composites were prepared using LM-25 Aluminum alloy as matrix material in which different weight percent of Borosilicate glass particles were added ranging from 3 wt.% to 12 wt.%. The variation in weight percent was brought about in steps of 3%. The fabrication of the composites was carried out in sand molds by incorporating two metallic (copper and Steel) and two non-metallic (Graphite and Silicon carbide) end chills. The specimens for strength and hardness tests were prepared as per ASTM standards and the specimens were drawn from near chill-end as well as from farther away from chill end. The microstructure of the specimens reveal a refined grain structure proving the sound quality of the castings. The result analysis also leads to the conclusion that metallic chills are more beneficial as compared to non-metallic chills for obtaining a good quality composites. Copper chill with a high volumetric heat capacity proved to be the best chill material amongst the others.

Abstract: Poly (trimethylene terephthalate) (PTT)/graphene oxide (GO) nanocomposites were prepared by melt mixing. The effect of GO on non-isothermal melt crystallization kinetics of PTT with different amounts of GO were investigated by differential scanning calorimetry (DSC). The Avrami, Ozawa and Mo were used to analyze the non-isothermal crystallization process. The results of Avrami analysis showed that adding GO into PTT matrix changed the crystallization nucleation of PTT. Ozawa analysis could not be used for the non-isothermal crystallization of PTT/GO nanocomposites. According to the results of Mo analysis, a higher cooling rate would be needed in order to obtain a higher degree of crystallinity at unit crystallization time.

Abstract: Zinc oxide (ZnO) nanograins are synthesized by precipitation method filled epoxidized natural rubber compared to conventional ZnO. The synthesized ZnO nanograins are characterized by X-ray diffraction and transmission electron microscopy and found that average primary size of ZnO synthesized around 40 nm and the specific surface area of 28.72 m² g^-1. Furthermore, the cure characteristics, rubber mechanical properties and permanent set were investigated. The obtained results are found that the ZnO nanograins significantly affected to cure characteristics, rubber mechanical properties and permanent set. This is due to small grain size and large specific surface area.

Abstract: This study investigated a novel crosslinking agent for epoxidized natural rubber (ENR). The result showed that it was possible to thermally crosslink ENR with maleic anhydride (MA). No additional catalyst was needed. FT-IR spectra revealed that after heating the ENR mixed with MA, there was the formation of the ester linkages. The crosslinking of ENR via these newly formed linkages was confirmed by the formation of gel once the heated rubber sample was immersed in toluene. The rheographs indicated that the crosslinking can take place at 80 °C and the curing rate and degree of crosslinking were dependent of the MA content. The cured ENR with MA showed higher decomposition temperature and better tensile strength than the uncured one.

Abstract: In this paper, the emission spectra of the atmospheric N₂ and N₂/CO₂ DBD plasma being processed by PP sample are analyzed. The results indicate the spectrum lines of oxygen atoms ion (O⁺) in the region of 382.1 nm - 389.3 nm and 412.1 nm - 421.3 nm are observed in N₂ plasma. However, the spectrum lines of O⁺ has absolutely disappeared, furthermore the γ spectrum band of NO in the region of 270nm-325nm has appeared in N₂/CO₂ plasma because the metastable nitrogen molecules () are quenched by CO₂ molecules. This causes that the collision of the metastable nitrogen molecules () and PP sample surface were reduced and ultimately leads to a reduction in the treatment effect of the N₂/CO₂ plasma on the surface of the PP sample. Therefore, this indicates the metastable nitrogen molecules () in the plasma region plays a key role in improving the characteristics of the PP surface.

Abstract: Novel biocompatible tough hydrogels were prepared through free radical micellar polymerization of N-isopropylacrylamide (NIPAM) with ammonium persulphate (APS) as initiator, in which hydrophobic monomer stearyl acrylate (C18) underwent micellar polymerization in the presence of gelatin as emulsifier. FT-IR and DSC demonstrated the formation of co-polymer of NIPAM and C18. Swelling results indicated that hydrophobic polymer domains derived from C18 in aqueous medium acted as the physical crosslinking points by hydrophobic association. Uniaxial tensile test demonstrated the mechanical properties of hydrogels increased with increasing C18 and gelatin contents. The hydrogel exhibited low toxicity and promoted cell proliferation. The desirable toughness, low toxicity and the promoting effect of cell proliferation made the present hydrogels good candidates for tissue regeneration materials.

Abstract: Developing sensitive, reliable and simple methods for detection of protein biomarkers in complex biological matrixes is a major challenge in recent years. In most cases, immunoassays are performed in muti-well-plates in well-equipped labs, which is time consuming and expensive. There is great interest in transitioning immunoanalysis from the lab so the analytical capabilities of immunoanalysis can be employed to diagnose disease at the point-of-care and monitor the environment in the field. In immunoassay applications, antibodies are immobilized onto biointerface to capture specific biomarkers. To improve the sensitivity and reduce the size of immunosensor, immobilizing antibody at high density is essential. Here, we developed an easier method to conjugate the antibodies within the chitosan composite film and remove the non-specific binding with electrical field.