Microwave Absorption Properties of Polyaniline/Titanium Dioxide (PAni/TiO2 ) Doped with Different Types of Fullerenes

In this work, Polyaniline/titanium dioxide (PAni/TiO 2 ) nanocomposites without and with addition of fullerene such as pristine fullerene (C 60 ) and small gap fullerene (S.G.F) were prepared through template-free method by using hexanoic acid (HA) as a dopant. FTIR and UV-Vis spectra confirmed the chemical structure of conjugated PAni and indicated that the resulted PAni is in conducting state. The existence of fillers in PAni nanocomposites were confirmed by the characteristic peaks of TiO 2 and fullerene in XRD pattern. Based on FESEM images obtained, nanocomposites formulated with C 60 (PAni/HA/TiO 2 /C 60 ) formed the nanorods/nanotubes and microrods/microtubes with the biggest diameter (240 nm), followed by PAni with S.G.F (PAni/HA/TiO 2 /S.G.F) and PAni without the addition of fullerene (PAni/HA/TiO 2 ) with diameter of 180 nm and 160 nm, respectively. Besides, PAni/HA/TiO 2 /C 60 also possessed the highest electrical conductivity of 1.708 × 10 −1 S/cm as compared to PAni/HA/TiO 2 /S.G.F and PAni/HA/TiO 2 (4.531 × 10 −3 S/cm to 1.439 × 10 −2 S/cm). Microwave absorption studies of PAni nanocomposites were carried out by using Microwave Vector Network Analyzer (MVNA) in the frequency range of 0.5–18.0 GHz. Among all nanocomposites, PAni/HA/TiO 2 /C 60 exhibited a narrow and the highest reflection loss (RL) peak of −61.3 dB at 9 GHz due to the highest conductivity (1.708 × 10 −1 S/cm), dielectric permittivity (0.46) and heterogeneity of PAni (larger amount of nanorods/nanotubes and microrods/microtubes) that have induced more disordered motion of charge carrier along the backbone of PAni. Thus, it eventually enhanced the molecular polarization such as greater space charge relaxation and hopping of confined charges

Acrylated Epoxidized Soybean Oil as a Green Alternative Healant in Development of Autonomous Self-Healing Materials

Progresses in the development of self-healing materials have resulted in transition from repairing damaged materials via external interference to autonomous internal healing process. This paper explores reaction between acrylated expoxidized soybean oil (AESO) with pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) hardener, followed by microencapsulation of AESO for its potential use in a novel self-healing system. Self-healing reaction involving AESO and PETMP is considered more environmentally friendly than most of the reported self-healing reactions not only because AESO is derived from renewable resources, but also due to the fact that the reaction does not rely on any heavy metal catalyst. Such catalysts are usually introduced in a self-healing system to speed up the intended healing process and it could be very harmful to the environment and also to the end users. It was found that AESO and PETMP are able to crosslink with each other and solidify at room temperature within 15 min of mixing. The reaction occurs readily at room temperature without any external interference, suggesting the viability of the reaction to be utilized in an autonomous self-healing system. This paper follows through with microencapsulation of AESO in melamine-urea-formaldehyde, and result of the characterizations reveal that the microcapsules obtained are spherical with average diameter of around 150 µm, free-flowing, thermally stable at temperature up to 200 °C, and the calculated % of microencapsulation reached as high as 86.4%. © 2018, Springer Science+Business Media, LLC, part of Springer Nature

Novel natural rubber-based epoxy coating

The use of renewable resources in development of polymeric products is becoming more relevant in the current times, braced by the scarcity of fossil resources and threat from global warming. The manuscript describes the preparation of epoxy resin from epoxidized natural rubber (ENR) via ultraviolet (UV) treatment, followed by investigation on the film properties of the coating produced by blending the natural rubber-based epoxy resin with pentaerythritol tetrakis(3-mercaptopropionate), PETMP as the hardener. The UV treatment involved is responsible to break down the natural rubber into smaller molecular weight fractions so that it becomes more compatible with common solvents and chemicals, and at the same time improves the solubility and viscosity of the resin. The results obtained are very encouraging, with significant reduction in the molecular weight of the rubber observed after 6 hours of UV treatment, and spectroscopic characterization suggests that substantial amount of epoxide group in the ENR was effectively preserved during the treatment for subsequent reaction with PETMP. The epoxide group in the UV-degraded ENR was found to react with the –SH group of PETMP after the two were blended, applied into film, and heated at 80 °C. The properties of the coatings produced were investigated via pencil hardness test, crosshatch adhesion tape test, thermal stability test, water, and chemical resistance test. Most of the coating formulations produced film with excellent hardness, adhesion and chemical resistance. Coating B and C are among the best coating formulations, with both recorded pencil hardness grade ≥ 4H, zero film removal in the adhesion test, no film defect observed during saltwater, acid and alkaline resistance test, and reasonably good thermal stability with onset of degradation above 200 °C

Synthesis and evaluation of poly(isoprene-co-acrylonitrile) as synthetic rubber with enhanced oil resistance

Increasing demand for durable rubber and rapid advancement in the automotive sector has made oil-resistant rubber an increasingly important material. Among them, nitrile rubber (NBR) is the most iconic due to its extraordinary oil resistance contributed by the polar nitrile pendant groups. Synthesis of NBR, however, is highly hazardous due to the explosive nature of the gaseous monomer butadiene. In this work, poly(isoprene-co-acrylonitrile) (NIR) was synthesized using free radical emulsion polymerization, with liquid monomer isoprene as the diene in the rubber formulation. The spectroscopic analysis confirmed the formation of NIR and indicated that the polymerized isoprene in the rubber is predominantly of 1,4-microstructure. A series of rubbers with different contents of acrylonitrile were produced and the mechanical, thermal, as well as oil resistant property of the resultant rubber films were evaluated. Vulcanized NIR films displayed glass transition temperatures from –9.4 to 20.2 °C, suggesting that the polymers are rubbery at ambient and higher temperatures. The NIR rubber films exhibited excellent oil resistance with less than 2% swelling in mineral oil, good thermal stability with onset degradation temperature in the range of 361.3 to 369.9 °C, and adequate mechanical strength from 1.61 to 8.23 MPa. The synthesized NIR rubber has the potential to serve as an alternative to NBR which had been traditionally used for oil resistance applications

Bio-Based Materials Riding the Wave of Sustainability: Common Misconceptions, Opportunities, Challenges and the Way Forward

Solid waste disposal, particularly of plastic and rubber, significantly impacts the environment and human health; thus, encouraging consumers to u sustainable alternatives is essential to ensure a resilient future. In recent decades, bio-based material research has primarily focused on bioplastics and, accordingly, current knowledge of alternative sustainable materials (such as biorubber) is fragmented, with consumer misconceptions posing a key challenge. This paper provides a comprehensive overview of the fundamentals of bio-based materials, in addition to common misconceptions about them. The findings of a public survey that aimed to assess consumers’ attitudes towards, as well as their awareness and perceptions of, conventional and sustainable alternative materials, particularly oxo-biodegradable rubbers, are also reported in this paper. Despite their unfamiliarity with the terms ‘bio-based’ and ‘oxo-biodegradable’, most respondents had a positive view of bio-based products and expressed an interest in reducing their use of conventional products in favour of sustainable alternatives. The results also revealed that consumers are willing to spend more on sustainable alternatives because they are aware of the environmental issues associated with solid waste. This study provides new insights into knowledge gaps and challenges that must be addressed to promote the prudent use of sustainable materials in a fast-changing world

Physiochemical and in vitro cytotoxicity properties of biocompatible palm fatty acid-based polyesters

With the sharp rise in global interest in sustainability and environmental concerns, there is a growing demand in replacing petroleum-derived raw materials with renewable plant-based raw materials in the production of polymers. In this study, two palm fatty acid polyesters were synthesized from palmitic and stearic acids. Their chemical structures were identified by FTIR and 1H-NMR analysis. Both polyesters showed a moderately high conversion rate from the acid value determination. DSC analysis showed that the palmitic acid polyester (PAP) had a lower Tg than that of stearic acid polyester (SAP), where PAP had a Tg of 1.8 °C, while SAP had a Tg of 31.9 °C. TGA demonstrated that thermal decomposition of both polyesters took place via two-stage processes, which occurred above 200 °C. GPC analysis showed that PAP (1031 g/mol) had a higher Mn value than SAP (972 g/mol). MTT assays were performed to determine the cytotoxicity of these polyesters against human keratinocytes (HaCaT), mouse fibroblasts (3T3), mouse hepatocytes (H2.35), and canine kidney cells (MDCK) in both dose- and time-dependent manners, with SDS serving as the experimental benchmark. Comparative cytotoxicity test showed that both PAP and SAP were biocompatibility and non-cytotoxic with the cell viability well above 80%, except SAP demonstrated a moderately low cytotoxicity on fibroblasts with cell viability remaining as 50.4% following 72 h exposure at 100 μg/mL of concentration. These findings suggest that the natural-sourced palm fatty acid polyesters have high potential to be used in pharmaceutical and nutraceutical applications