Current Applied Polymer Science - Volume 4, Issue 3, 2021

Auxetic materials have high potential due to their exceptional properties resulting from a negative Poisson’s ratio. Recently, several auxetic polymer-based materials have been developed. In fact, several applications are looking for a lightweight material (less material consumed in production and transport) while having high mechanical performances (impact absorption, rigidity, strength, resistance, etc.). So, a balance between density and toughness/strength is highly important, especially for military, sporting, and transport applications. So auxetic materials (especially foams) can provide high impact protection while limiting the material’s weight. This article presents a review of recent advances with a focus on auxetic polymers, with particular emphasis on the auxetic polymer foams in terms of their fabrication methods and processing conditions (depending on the nature of the cellular structure), the effect of the fabrication parameters on their final properties, as well as their models and potential applications.

Self-healing coatings are intended to increase long-term durability and reliability and can be prepared by the use of microcapsules containing a self-healing agent capable of interacting with the matrix and regenerating the system. This review article provides an overview of the state-of-the-art patents published in the field of microcapsule-based self-healing organic coatings since the early 2000s. A discussion regarding coatings for corrosion protection is presented and the different self-healing approaches and mechanisms are also addressed, as well as future challenges and expectations for this kind of coatings.

Background: The demand for novel biomaterials has exponentially increased in the last years as well as the search for new technologies able to produce more efficient products in both drug delivery systems and regenerative medicine.

Objective: The technique that can pretty well encompass the needs for novel and high-end materials with a relatively low-cost and easy operation is the electrospinning of polymer solutions.

Methods: Electrospinning usually produces ultrathin fibers that can be applied in a myriad of biomedical devices, including sustained delivery systems for drugs, proteins, biomolecules, hormones, etc., and in a broad spectrum of applications, ranging from transdermal patches to cancer-related drugs.

Results: Electrospun fibers can be produced to mimic certain tissues of the human body, being an option to create new scaffolds for implants with several advantages.

Conclusion: In this review, we aimed to elaborate the use of electrospun fibers in the field of biomedical devices, more specifically the electrospun nanofibers applications for the production of drug delivery systems and scaffolds for tissue regeneration.

Background: Natural polymers are fascinating category of small chain molecules originating from natural resources, and few examples include Sodium Alginate and Xanthan Gum which are water-soluble in nature; used for mainly food packaging, biomedical and pharmaceutical applications. In the proposed research work, an effort was made to overcome the polymer challenges emerging from the development of polymer blends, as the miscibility between polymers is a vital aspect.

Objective: This work focuses on the miscibility studies of natural origin polymers. In regards to that, Sodium Alginate/ Xanthan Gum blends were prepared in variable concentrations in aqueous medium and it was utilized for viscosity analysis, FTIR, Ultraviolet spectroscopic studies at variable temperatures.

Methods: It was observed that the developed Sodium Alginate / Xanthan Gum blends are miscible with each other at most of the temperatures (at 20°C, 40°C and 60°C) considering their viscosity parameters, FTIR and UV spectral data.

Results: Viscosity studies revealed that the miscibility windows of polymeric ratio increases as the temperature increases whereas FTIR spectral patterns exhibited that the composition having 60:40 ratio of polymers exhibits high intensity stretches and represented to be miscible when compared to other combinations.

Conclusion: The present study has reported the simple and efficient method in exploration of the miscibility windows of Sodium alginate and Xanthan gum blend.

Background: Epoxy resins have been extensively used in fire hazard environments, such as printed circuit boards, electrical isolation materials, adhesives, construction, and transportation due to their economically viable, simple processing. Therefore, the development of thermally stable and flame-retardant epoxy resin systems is essential.

Objective: The aim of the present study was to study the effect of the functionality of organophosphorus flame retardants on DGEBA-based epoxy resin nanocomposites on thermal stability and flame retardancy.

Methods: DGEBA (diglycidyl ether of bisphenol-A)-based epoxy resin nanocomposites having 2.0 wt% phosphorus were prepared with organophosphorus flame retardants with different functionalities by using an in-situ polymerization method. The flame retardant compounds uni-functional 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and bi-functional 2-(6-oxid-6H-dibenz [c, e] [1, 2] oxaphosphorin 6-yl) 1, 4-benzenediol (DOPO-HQ) were prepared. The thermal behavior of composites was studied by TG and DTA techniques. The flammability behavior was investigated by UL-94 and limiting oxygen index (LOI) tests.

Results: The XRD and TEM results showed the mixed dispersion of nanoclay platelets in an epoxy matrix. The thermal stability of the epoxy composite (EPDOPO-HQ) containing bi-functional DOPO-HQ is increased by 16°C in comparison to the epoxy composite (EPDOPO) containing uni-functional DOPO. According to the TG analysis, the addition of nanoclay was observed to be more effective and synergistic with bi-functional DOPO-HQ as the EPDOPO-HQ/NC sample gains more resistance to degradation after around 450°C and also gave rise to a high char yield. Epoxy resin samples containing reactive flame retardants gave UL-94 V-0 rating, but further addition of 2.0 wt% nanoclay lowered the rating from V-0 to V-1.

Conclusions: TG analysis of the epoxy composite samples showed that the addition of nanoclay were observed to be synergistic with bi-functional flame retardant (DOPO-HQ) as the EPDOPO-HQ/NC sample gained more resistance to degradation after around 450°C due to the formation of mixed intercalated and exfoliated structure. The EPDOPO-HQ sample gave a high char yield with increased onset degradation temperature, high thermal stability as well as high flame retardancy.

Background: A polymer as a host in the optical waveguide has many advantages and, when doped with rare-earth (RE) elements, offers an efficient connection, compared to its glass-based counterparts as an amplifier. However, a polymer matrix causes the concentration quenching effect of REs in the polymer matrix, making the fabrication of RE-doped polymer waveguides more complicated as compared to the fabrication of glass-based complements. Moreover, controlling scattering loss at the particle-polymer interface for maintaining the optical clarity of the composite is also a great challenge.

>Objective: The main aim of the present study was to optimize the synthesis of Er2O3 grafted Polymethylmethacrylate (PMMA)-Polystyrene (PS) composite based transparent ternary nanocomposite and its characterization to implement them as a potential material for active core in Polymer Optical Preform (POP).

Methods: Nano Erbium Oxide (Er2O3) was successfully synthesized by the wet-chemical method and encapsulated by a polymerizable surfactant, i.e., 3-Methacyloxypropyltrimethoxy silane (MPS). The encapsulated nanoparticles were further subjected to grafting with PMMA using in-situ polymerization of methyl methacrylate (MMA) followed by blending with PS via solvent mixing technique.

Results: The optical transparency of the ternary composite was achieved by fine-tuning the diameter (15-20 nm) of the PMMA coated Er2O3 . The crystallinity present in Er2O3 was significantly reduced after PMMA coating. The comparatively higher refractive index obtained at 589 nm wavelength for the synthesized material indicated its usability as active core material in the presence of a commercial acrylate cladding tube. A photoluminescence (Pl) study indicated that the technique might be used for a higher level of Er³⁺ doping in polymer matrix without sacrificing its transparency.

>Conclusion: The obtained results indicated that the sample synthesized with the adopted technique gives better Pl intensity compared to the other methods of Er³⁺ incorporation in polymer optical preform (POP).