Advances in Polymer Technology

In recent years, there has been a growing awareness and demand for global sustainability, as well as a mandate for the use of renewable and environmentally sustainable materials and processes. Due to which, massive efforts are being made to develop and nurture the next generation of composite materials that are energy efficient, environmentally friendly, and biodegradable. Light weight, lower coefficient of thermal expansion, and comparable tensile strength exhibited by natural fibers render them the choice for use in several industrial products and applications over the last decade. Natural fibers as the reinforcing entity are pitted against their synthetic variants primarily because of the superior aspects like biodegradability and excellent strength-to-weight ratio. This article presents the review on various nonconventional natural fibers such as tamarind seed and shell, Luffa cylindrica, groundnut shell, coconut coir, papaya bast, okra, and Ashoka tree seed. The flow of the chapter includes the introduction, extraction methodologies, and fabrication, and investigations of mechanical properties, applications, and sustainability are dealt in detail for nontraditional natural fibers. The okra fibers possess greater tensile strength of up to 262.8 MPa in comparison with other fibers, while the Ashoka tree seed fibers are known to possess a maximum flexural strength of up to 125 MPa. Further, these fibers are used as reinforcements in potential applications in interiors and automobile and aircraft panels and wood-based particle board composites owing to the increase in tensile and flexural strengths of composites.

In order to improve the flame retardancy of poly(ethylene terephthalate) (PET) and maintain its excellent foamability, nanosilica (nano-SiO₂), and zinc diethyl hypophosphite (ZDP) were selected as synergistic flame retardants, and pyromellitic dianhydride (PMDA) was used as a chain extender to carry out flame retardant and chain extension modification of PET simultaneously. The flame retardancy and flame-retardant mechanism of modified PET were characterized by limiting oxygen index, vertical combustion test, thermogravimetric analysis, and SEM. Dynamic rheological test and DSC were used to analyze the rheological and thermal properties. The foaming ability was also studied by batch foaming experiments. The test results indicated that nano-SiO₂ and ZDP had a synergistic effect, which could significantly improve flame retardancy of PET. The vertical combustible grade of modified PET reached V-0 grade, and the limiting oxygen index increased from 21% to about 30%. The role of nano-SiO₂ on the flame retardancy of PET was mainly to increase compactness and strength of the carbon layer, which could block combustible gas produced by the pyrolysis of PET and resist dripping behavior. At the same time, the addition of nano-SiO₂ increased the crystallization temperature and crystallinity of PET. Otherwise, nano-SiO₂ could act as a bubble-nucleating agent and improve the foaming ability of modified PET. When the addition amount was 1 wt%, not only did the maximum foaming ratio increase but the foaming temperature zone was also widened from 225°C-235°C to 225°C-250°C. Finally, a flame-retardant PET system with good foaming property was proposed.

In the emerging modern technology of additive manufacturing, the need for optimization can be found in literature in many places. Additive manufacturing (AM) is making an object layer by layer directly from digital data. Previous works of literature have classified additive manufacturing processes into seven types. However, there is a lack of comprehensive review describing the optimization challenges and opportunities in the material extrusion process (polymer technology) and also the need for FDM polymer materials application in impeller making. In this review paper, a specific optimization method called multicriteria decision-making (MCDM) from the mathematical programming technique used in additive manufacturing polymer technology (AMPT) is discussed. The other topics such as different types of optimization techniques, applications of different MCDM tools and their applications in different fields including AM, and the optimization challenges and opportunities in AMPT particularly impeller application are discussed.

In this work, polyphenylene sulfide (PPS) containing carboxyl group was synthesized and used to prepare PPS-2COOH/LGF/AlN and composites with high-temperature resistance, corrosion resistance, low dielectric constant, and low dielectric loss were prepared with boron nitride/aluminum nitride (BN/AlN) and glass fiber (LGF). The results showed that the introduction of carboxyl groups did not affect the structure and thermal properties of PPS. The composites exhibited good mechanical properties with a tensile strength of 65 MPa~97 MPa and flexural strength of 112 MPa~154 MPa. The TGA results showed that the composites had good thermal stability, and the T_5% of PPS-2COOH/LGF/AlN (20) and PPS-2COOH/LGF/BN (20) reached up to 511.6°C and 506.3°C, respectively. They were insoluble in some organic solvents, such as NMP and DMF at room temperature, and they exhibited excellent chemical resistance. The dielectric performance results showed that with the increase of frequency, the dielectric constant and dielectric loss gradually decreased, the dielectric constant of PPS-2COOH/LGF/BN (15) was 3.9, and the dielectric loss of PPS-2COOH/LGF/BN (15) was 0.01. From the above results, it can be concluded that the composite materials PPS-2COOH/LGF/AlN and PPS-2COOH/LGF/BN have potential application prospects in the field of 5G high thermal conductivity materials.

Pipes are manufactured primarily through the extrusion process. One of the material extrusion processes in recent digital manufacturing is additive manufacturing’s fusion deposition modeling. Pipes are made from various materials such as metal and plastic/polymers, and the main challenge has been in selecting the pipe material for the customized application. For the creation of water-passing tubes, this research has chosen appropriate carbon-reinforced polymers that can be used with filament made of polyether ether ketone (PEEK) and polyethylene terephthalate glycol (PETG). For this goal, the analytical hierarchy process, also known as the AHP, is used to choose the best material based on factors such as cost, temperature resistance, printing speed, and mechanical properties of the material. The results revealed that PEEK-CF is a better material for the customized impeller application than PETG-CF. The PEEK-CF obtains the higher priority value of 0.6363, and the PETG-CF obtains 0.2791. This decision-making technique can be used to select other comparable customized applications.

This study is aimed at producing a biofoam cup made from sugarcane bagasse with tempeh mold (Rhizopus oligosporus). Soybean flour (SF) was added to promote the growth of mycelia, which could bind the bagasse fiber matrix. The main materials were whole bagasse (B) and depithed bagasse (DB). The SF weight ratios to bagasse were 1 : 1 (SF1) and 1.5 : 1 (SF1.5). Therefore, the studied specimens were labeled B-SF1, DB-SF1, B-SF1.5, and DB-SF1.5. All biofoam cups were analyzed for their physical properties (water absorption and porosity), mechanical properties (puncture and compressive strengths), biodegradability, and thermal properties (thermogravimetric analysis). The lowest water absorption rates were obtained from the B biofoam cups () and the SF1.5 biofoam cups (). Both B-SF1 and B-SF1.5 had lower porosity ( and , respectively) than the DB biofoam cups. Moreover, the B biofoam cups had smoother biofoam surfaces, smaller voids, and lower porosity compared with the DB samples. However, the DB biofoam cups showed the highest puncture strength ( kg cm⁻²) among all samples. Nevertheless, the B-SF1.5 biofoam cup had the highest compressive strength ( MPa) and the DB-SF1.5 exhibited the slowest degradation rate () after 14 days of soil burial. The highest thermal stability was obtained from B-SF1.5, which had a thermal degradation temperature of 264°C. Overall, B-SF1.5 had the smoothest surface, good thermal stability, and high compressive strength.