Influence of weathering effect in natural environment on thermal properties hybrid kenaf blast/glass fibre and unsaturated polyester composite M Mohammed, A R Rozyanty, B O Beta et al. (10, 20, 30, 40,and 80 wt.%) using mechanical blending method. The blends were cured at room temperature using methyl ethyl ketone peroxide (MEKP) (4 wt.%) as catalyst initiator without the presence of catalystaccelerator. The effect of vinyl ester composition on theenhancement of mechanical and thermal properties of unsaturated polyester/vinyl ester blends was investigated.The polymer blends were characterized by Fourier Transform Infra Red (FTIR)spectroscopy, tensile testing, hardness testing, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). IR spectra showed UP and VE peaks. The curing copolymerization reactionoccurred at vinyl (C=C) bonds. The addition of vinyl esters enhanced mechanical and thermal properties. The UP/VE blends showed homogeneous morphology, transparent and copolymer thermoset blend.Keywords: unsaturated polyester, vinyl ester, polymer blend, thermal properties IntroductionUnsaturated polyester is a widely used thermosetting resin. Unsaturated polyester has a reactive vinyl (carbon-carbon double) bond. Styrene is added to unsaturated polyester as asolvent and acrosslinking agent for curing reaction. The organic peroxide is used to initiatethe reaction. Organic salt isadded to accelerate the reaction. The polymer is achieved as a result of random condensation copolymerization reaction between styrene and unsaturated vinyl double bonds by free radical mechanismforming crosslinked network structure [1,2]. Unsaturated polyester is a resin (prepolymer) with low price, light weight, easy processing and water resistance. Unsaturated polyester commonly used in laminating resin, composites, coating, adhesive, microelectronic, aerospace, building, automotive, and shipbuilding. However, unsaturated polyester shows limited mechanical and thermal properties. It is necessary to enhance the properties of unsaturated polyester.The properties of unsaturated polyester have been enhanced by theadditionof carbon fiber , fly ash, carbon nanotube, and polyamide [3][4][5][6]. Vinyl ester is an attractivehigh-performance thermoset polymer. Vinylester has reactive double bonds with rigid epoxy structure. Vinyl ester is synthesized by the reaction of epoxy with methacrylic

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The Cu-Sn composite is one of material for frangible bullet application. Frangible bullet are designed to disintegrate on impact against rigid surfaces to avoid ricochet hazards in shooting ranges or law enforcement training facilities. The manufacturing process of CuSn is based on powder metallurgy with variation of weight percent of Sn and compacting pressure. Sintering is performed at temperature of 260°C within 30 minutes period with nitrogen gas atmosphere. The secondary phase (Cu3Sn and Cu6Sn5) was identified. The highest density and hardness are 7,446 g/cm3, 83 HRF for Cu-5 wt% Sn at 500 MPa. The pressure strength and modulus of elasticity are 275,72 MPa and 59,43 GPa.

A videoconferencing system to communicate synchronously is an indispensable tool for educators, teachers, students, parents, and administrators in online courses. One of the effective online learning platforms that can increase student engagement and motivation in online courses is Microsoft Teams. This research aimed to explore English as a Foreign Language (EFL) students’ views of enacting Microsoft Teams videoconferencing. This study employed a mixed-method design complemented by observation, open-ended questionnaires, as well as in-depth interviews for qualitative analysis in capturing and exploring their experience of synchronous learning using the Microsoft Teams in the post-pandemic. Furthermore, close-ended questionnaires were also distributed as quantitative data. The results revealed that Microsoft Teams helped the learners to be more involved in debates with both faculty and students as a result of their participation in discussion forums. They also gained a better comprehension and knowledge of language learning. It was clear that they were highly motivated and enjoyed the online course due to its ease of use and fun features, and they appreciated direct feedback in the synchronous online meeting. Thus, the learners with strong motivation can develop their learning autonomy. They can monitor and evaluate their self-progress in learning. Further research is highly recommended for exploiting Microsoft Teams to create innovations in a virtual classroom.