Mouldable Conductive Plastic with Optimised Mechanical Properties.

This paper investigates making an injection mouldable conductive plastic formulation that aims for conductivity into the electromagnetic interference (EMI) shielding range, with good mechanical properties (i.e., stiffness, strength, and impact resistance). While conductivity in the range (electrostatic charge dissipation) and EMI shielding have been attained by incorporating conductive fillers such as carbon black, metals powders, and new materials, such as carbon nanotubes (CNTs), this often occurs with a drop in tensile strength, elongation-to-break resistance, and impact resistance. It is most often the case that the incorporation of high modulus fillers leads to an increase in modulus but a drop in strength and impact resistance. In this work, we have used short carbon fibres as the conductive filler and selected a 50/50 PBT/rPET (recycled PET) for the plastic matrix. Carbon fibres are cheaper than CNTs and graphenes. The PBT/rPET has low melt viscosity and crystallises sufficiently fast during injection moulding. To improve impact resistance, a styrene-ethylene-butadiene-styrene (SEBS) rubber toughening agent was added to the plastic. The PBT/rPET had very low-impact resistance and the SEBS provided rubber toughening to it; however, the rubber caused a drop in the tensile modulus and strength. The short carbon fibre restored the modulus and strength, which reached higher value than the PBT/rPET while providing the conductivity. Scanning electron microscope pictures showed quite good bonding of the current filler (CF) to the PBT/rPET. An injection mouldable conductive plastic with high conductivity and raised modulus, strength, and impact resistance could be made.

Studies on the Effect of the Addition of Nano-Spherical Particles of Aluminum on the Thermal, Mechanical, and Morphological Properties of PBT-PET Blend Composites.

In previous works, we had found that the addition of micron-sized, irregular-shaped aluminum (Al) powder, or Al nano platelets (flakes), improved the mechanical properties of polyesters, and that, additionally, the flakes led to an increase in electrical conductivity. The aim of this work was to examine the effect of nano-spherical particles of aluminum in a 60/40 PBT/PET polyester blend. A blend was used because it can help with the formation of a segregated network of metal particles that allows electrical conductivity at low loading. The notched Izod impact of Al nano-spherical composites increased with nano Al content up to an addition level of 2 vol.%. However, the tensile strength and flexural strength decreased gradually with increasing filler loading. Thus, the spherical shape and nano size of the Al particle caused it to be less effective than the micron-sized, irregular-shaped Al powder, or the Al flakes. The reason for this is that, while nano spherical particles have high surface area for bonding with the matrix, the Al-Al aggregation stands in the way of wetting by the polymer melt, whereas aggregation in flakes does not cause as much of a problem. The segregated network structure to enhance electrical conductivity did not form in this blend system with nano spherical particles. The nano-spherical Al acted as a nucleating agent but did not cause transesterification between the two polyesters or make it more susceptible to degradation.

Studies on Polybenzimidazole and Methanesulfonate Protic-Ionic-Liquids-Based Composite Polymer Electrolyte Membranes.

In the present work, different methanesulfonate-based protic ionic liquids (PILs) were synthesized and their structural characterization was performed using FTIR, 1H, and 13C NMR spectroscopy. Their thermal behavior and stability were studied using DSC and TGA, respectively, and EIS was used to study the ionic conductivity of these PILs. The PIL, which was diethanolammonium-methanesulfonate-based due to its compatibility with polybenzimidazole (PBI) to form composite membranes, was used to prepare proton-conducting polymer electrolyte membranes (PEMs) for prospective high-temperature fuel cell application. The prepared PEMs were further characterized using FTIR, DSC, TGA, SEM, and EIS. The FTIR results indicated good interaction among the PEM components and the DSC results suggested good miscibility and a plasticizing effect of the incorporated PIL in the PBI polymer matrix. All the PEMs showed good thermal stability and good proton conductivity for prospective high-temperature fuel cell application.

Effect of Mixing Time on Properties of Whole Wheat Flour-Based Cookie Doughs and Cookies.

This study investigated if whole wheat flour-based cookie dough's physical properties were affected by mixing time (1 to 10 min). The cookie dough quality was assessed using texture (spreadability and stress relaxation), moisture content, and impedance analysis. The distributed components were better organized in dough mixed for 3 min when compared with the other times. The segmentation analysis of the dough micrographs suggested that higher mixing time resulted in the formation of water agglomeration. The infrared spectrum of the samples was analyzed based on the water populations, amide I region, and starch crystallinity. The analysis of the amide I region (1700-1600 cm-1) suggested that ß-turns and ß-sheets were the dominating protein secondary structures in the dough matrix. Conversely, most samples' secondary structures (α-helices and random coil) were negligible or absent. MT3 dough exhibited the lowest impedance in the impedance tests. Test baking of the cookies from doughs mixed at different times was performed. There was no discernible change in appearance due to the change in the mixing time. Surface cracking was noticeable on all cookies, a trait often associated with cookies made with wheat flour that contributed to the impression of an uneven surface. There was not much variation in cookie size attributes. Cookies ranged in moisture content from 11 to 13.5%. MT5 (mixing time of 5 min) cookies demonstrated the strongest hydrogen bonding. Overall, it was observed that the cookies hardened as mixing time rose. The texture attributes of the MT5 cookies were more reproducible than the other cookie samples. In summary, it can be concluded that the whole wheat flour cookies prepared with a creaming time and mixing time of 5 min each resulted in good quality cookies. Therefore, this study evaluated the effect of mixing time on the physical and structural properties of the dough and, eventually, its impact on the baked product.

The Influence of Emulsifiers on the Physiochemical Behavior of Soy Wax/Rice Bran Oil-Based Oleogels and Their Application in Nutraceutical Delivery.

This research evaluated the influence of stearic acid, sunflower lecithin, and sorbitan monooleate on soy wax (SYW)/rice bran oil (RBO)-based oleogels. The physiochemical behavior of oleogel samples was evaluated using colorimetry, microscopy, FTIR, mechanical, crystallization kinetics, X-ray diffraction, and a drug release investigation. The prepared oleogels were light yellow, and adding emulsifiers did not change their appearance. All oleogels showed an oil binding capacity of >98%, independent of emulsifier treatment. The surface topography revealed that emulsifiers smoothed the surface of the oleogels. Bright-field and polarized micrographs showed the presence of wax grains and needles. FTIR spectra indicated that oleogel samples had the same functional group diversity as the raw materials. The oleogel samples lacked a hydrogen-bonding peak. Hence, we postulated that non-covalent interactions were involved in the oleogel preparation. According to stress relaxation studies, the firmness and elastic component of oleogels were unaffected by emulsifiers. However, EML3 (oleogel containing sorbitan monooleate) showed lower relaxing characteristics than the others. EML3 exhibited the slowest crystallization profile. Due to its low d-spacing, EML3 was found to have densely packed crystal molecules and the largest crystallite size. The in vitro drug release studies showed that emulsifier-containing oleogels dramatically affected curcumin release. These results may help customize oleogels properties to adjust bioactive component release in the food and pharmaceutical industries.

Effect of Accelerated Weathering on the Thermal, Tensile, and Morphological Characteristics of Polypropylene/Date Nanofiller Composites.

The aging of polypropylene (PP) composites reinforced with date palm nanofiber (DNF) was investigated in this study in order to predict their long-term performance. To produce composites, date palm nanofibers in the range of 1-5 wt% loading were dry-melt-blended with polypropylene. These biocomposites were then subjected to UV exposure (Xenon arch source) for accelerated weathering for 250 and 500 h according to a standard method. The change in thermal properties before and after accelerated weathering was investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). TGA analysis shows that the maximum degradation temperature for sample at 1 wt% loading was 382.7 °C, which slightly decreased to 379.9 °C after 250 h and to 367.7 °C after 500 h of weathering. DSC analysis also revealed lower crystallinity of the same samples after exposure to accelerated weathering. Mechanical properties were also studied to identify the damage induced by accelerated weathering. The tensile strength of the highest loading (5 wt%) of the sample was found to occur at 34.83 MPa, which was slightly lowered to 31.64 after 500 h treatment. A minimal decrease in tensile strength, deterioration, and weathering-induced oxidation indicates the excellent stability of these composites. Therefore, our study provides insight into the aging behavior of such composites, which may be useful in dry conditions, as well as nonstructural automotive and other parts for which minimum tensile strength (~25 MPa) is specified.

Effect of Compatibilizer on the Persistent Luminescence of Polypropylene/Strontium Aluminate Composites.

There is a demand for long afterglow composites due to their potential applications in nighttime signal boards, sensors, and biomedical areas. In this study, Polypropylene (PP)/strontium aluminate-based composites [SrAl2O4:Eu2+/Dy3+ (SAO1) and Sr4Al14O25: Eu+2, Dy+3 (SAO2)] with maleic anhydride grafted PP compatibilizer (PRIEX) were prepared, and their auto-glowing properties were examined. After UV excitation at 320 nm, the PP/5PRIEX/SAO1 composites showed green emission at 520 nm, and blue emission was observed for PP/5PRIEX/SAO2 around 495 nm. The intensity of phosphorescence emission and phosphorescence decay was found to be proportional to the filler content (SAO1 and SAO2). The FTIR analysis excluded the copolymerization reaction between the SAO1 and SAO2 fillers and the PP matrix during the high-temperature melt mixing process. The SAO1 and SAO2 fillers decreased the overall crystallinity of the composites without affecting the Tm and Tc (melting and crystallization temperature) values. The thermal stability of the composites was slightly improved with the SAO1 and SAO2 fillers, as seen from the TGA curve. Due to the plasticizing effect of the compatibilizer and the agglomeration of the SAO1 and SAO2 fillers, the tensile modulus, tensile strength, and storage modulus of the composites was found to be decreased with an increase in the SAO1 and SAO2 content. The decreasing effect was more pronounced, especially with the bulk-sized SAO2 filler.

Conductive Plastics from Al Platelets in a PBT-PET Polyester Blend Having Co-Continuous Morphology.

Conductive plastics are made by placing conductive fillers in polymer matrices. It is known that a conductive filler in a binary polymer blend with a co-continuous morphology is more effective than in a single polymer, because it aids the formation of a 'segregated conductive network'. We embedded a relatively low-cost conductive filler, aluminium nano platelets, in a 60/40 PBT/PET polymer blend. While 25 vol.% of the Al nanoplatelets when placed in a single polymer (PET) gave a material with the resistivity of an insulator (1014 Ωcm), the same Al nano platelets in the 60/40 PBT/PET blend reduced the resistivity to 7.2 × 107 Ωcm, which is in the category of an electrostatic charge dissipation material. While PET tends to give amorphous articles, the 60/40 PBT/PET blends crystallised in the time scale of the injection moulding and hence the conductive articles had dimensional stability above the Tg of PET.

Synthesis and Characterization of Cellulose Triacetate Obtained from Date Palm (Phoenix dactylifera L.) Trunk Mesh-Derived Cellulose.

Cellulosic polysaccharides have increasingly been recognized as a viable substitute for the depleting petro-based feedstock due to numerous modification options for obtaining a plethora of bio-based materials. In this study, cellulose triacetate was synthesized from pure cellulose obtained from the waste lignocellulosic part of date palm (Phoenix dactylifera L.). To achieve a degree of substitution (DS) of the hydroxyl group of 2.9, a heterogeneous acetylation reaction was carried out with acetic anhydride as an acetyl donor. The obtained cellulose ester was compared with a commercially available derivative and characterized using various analytical methods. This cellulose triacetate contains approximately 43.9% acetyl and has a molecular weight of 205,102 g·mol-1. The maximum thermal decomposition temperature of acetate was found to be 380 °C, similar to that of a reference sample. Thus, the synthesized ester derivate can be suitable for fabricating biodegradable and "all cellulose" biocomposite systems.

Amorphous Poly(ethylene terephthalate) Composites with High-Aspect Ratio Aluminium Nano Platelets.

Previously, we reported that amorphous poly(ethylene terephthalate) (PET) filled with irregular nodular aluminium (Al) particles gave simultaneous increases in tensile modulus, tensile strength, and impact resistance, which is unusual for materials. Here, we investigated the effect of the particle shape and size by using nano-platelet Al. The Al nano-platelets had a thickness higher than graphenes and clays, but lower than mica and talc, and due to their large widths, they had high aspect ratios. Due to the ductility of Al, the platelets maintained the high aspect ratio and did not snap during injection moulding. In addition to avoiding the usual drop in tensile strength and impact, the composites with nano Al platelets gave an unusually high flexural modulus (8 GPa), which was almost double that attained practically with talc, mica, and graphene. This was because of the high tendency of the Al nano platelets to become oriented during moulding. The Al-PET composite would be a more cost-and-performance effective combination for making conductive composites. The Al is a cheaper material than graphene, surface treatment for adhesion (to PET) is unnecessary, and dispersion issues, such as exfoliation and de-aggregation, are not a problem.

Long Persistent Luminescent HDPE Composites with Strontium Aluminate and Their Phosphorescence, Thermal, Mechanical, and Rheological Characteristics.

In this work, HDPE/strontium aluminate-based auto glowing composites (SrAl2O4: Eu, Dy (AG1) and Sr4Al14O25: Eu, Dy (AG2)) were prepared, and their phosphorescence studies were conducted. In HDPE/AG1 composites, the green emission was observed at ~500 nm after the UV excitation at 320 nm. The HDPE/AG2 has a blue emission at ~490 nm and, in both cases, the intensity of emission is proportional to the AG1 and AG2 content. The DSC data show that the total crystallinity of both the composites was decreased but with a more decreasing effect with the bulky AG2 filler. The melting and crystallization temperatures were intact, which shows the absence of any chemical modification during high shear and temperature processing. This observation is further supported by the ATR-FTIR studies where no new peaks appeared or disappeared from the HDPE peaks. The tensile strength and modulus of HDPE, HDPE/AG1, and HDPE/AG2 composites were improved with the AG1 and AG2 fillers. The rheological studies show the improvement in the complex viscosity and accordingly the storage modulus of the studied phosphorescent HDPE composites. The SEM images indicate better filler dispersion and filler-matrix adhesion, which improves the mechanical characteristics of the studied HDPE composites. The ageing studies in the glowing composites show that there is a decrease in the intensity of phosphorescence emission on exposure to drastic atmospheric conditions for a longer period and the composites become more brittle.

Isolation and Characterization of Alpha and Nanocrystalline Cellulose from Date Palm (Phoenix dactylifera L.) Trunk Mesh.

Highly pure cellulosic polymers obtained from waste lignocellulose offer great potential for designing novel materials in the concept of biorefinery. In this work, alpha-cellulose and nanocrystalline cellulose were isolated from the date palm trunk mesh (DPTM) through a series of physicochemical treatments. Supercritical carbon dioxide treatment was used to remove soluble extractives, and concentrated alkali pretreatment was used to eliminate the lignin portion selectively to obtain alpha-cellulose in approximately 94% yield. Further treatments of this cellulose yielded nanocrystalline cellulose. The structure-property relationship studies were carried out by characterizing the obtained polymers by various standard methods and analytical techniques such as Fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), energy dispersive X-ray diffraction (EDX-XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Almost 65% yield of pure cellulose was achieved, out of which 94% is the alpha-cellulose. This cellulose shows good thermal stability and crystallinity. The microscopic analysis of the nanocellulose showed a heterogeneous mix of irregular-shaped particles with a size range of 20-60 nm. The percentage crystallinity of alpha-cellulose and nanocellulose was found to be 68.9 and 71.8, respectively. Thus, this study shows that, this DPTM-based low-cost waste biomass can be a potential source to obtain cellulose and nano-cellulose.

Strontium Aluminate-Based Long Afterglow PP Composites: Phosphorescence, Thermal, and Mechanical Characteristics.

A tremendous potential has been observed in the designing of long afterglow materials for sensing, bioimaging, and encryption applications. In this study, two different strontium aluminate-based luminescent materials; SrAl2O4: Eu, Dy (S1), and Sr4Al14O25: Eu, Dy (S2) were melt-mixed with polypropylene (PP) matrix, and the phosphorescence properties were evaluated. After excitation at 320 nm, the PP/S1 composite exhibited a green emission and the PP/S2 generated a blue emission at 520 nm and 495 nm, respectively. The emission spectra intensity increased by increasing the content of these luminescent fillers. The attenuated total reflection-Fourier transform infrared (ATR-FTIR) experiments show that no chemical reaction occurred during the melt-mixing process. The differential scanning calorimetry (DSC) results revealed that the total crystallinity of the composites reduced by increasing the amount of the fillers; however, no changes in the temperature of melting (Tm) and crystallization (Tc) of PP were observed. Both fillers improved the impact strength of the composites, but the tensile strength (TS) and modulus (TM) decreased. Poly (ethylene glycol) dimethyl ether (P) plasticizer was used to improve the filler-matrix interaction and its dispersion; nevertheless, it adversely affected the intensity of the luminescence emissions.