Authored by Pighinelli L*
Abstract
The use of natural polymers as substitutes for synthetic polymers in the development of aggregating materials for the pentaerythritol tetranitrate (PETN), explosive is a poorly explored area, but with the ability to enable the development of new sustainable, more chemical friendly and economically, using as an alternative a renewable material like chitosan and its derivatives. Chitin, a natural polymer that makes up the exoskeleton of crustaceans, insects, and the fungal cell wall, along with their derivatives, such as chitosan, offer attractive chemical, physical, and biological properties. It is noteworthy that chitin is found in high abundance in nature, and allows obtaining materials capable of offering interesting characteristics, such as chelating capacity, biocompatibility, biodegradability, nontoxic [3]. In this review, is possible to see the possibility to use a natural polymers as a potential materials to use as na aggregate polymer in PETN, as well as the increasing trend of the use of renewable natural polymers to develop creation of materials with high technological grade for mant areas of application. The aim of this study is to show the potential of using chitosan as an aggregator polymer for PETN crystals.
Introduction
Pentaerythritol tetranitrate (PETN) is an explosive that exhibits the functionality of the ester nitrate group. The explosive capacity and high chemical stability led to large-scale production of PETN, which could only be achieved after pentaerythritol production, that is the raw material for its production. PETN was the first explosive to be prepared by pentaerythritol nitration in 1894. Its commercial production was achieved after the consolidation of the synthetic routes of formaldehyde and acetaldehyde, precursor compounds for the synthesis of pentaerythritol [1]. This explosive has military, industrial, medical and civil applications due to its high energy density, which is strongly linked to particle size and structure morphology, such as crystal lattice defects, surface area and structural phases [2,3]. During applications, formulations containing PETN are stabilized by additives that increase handling safety. In the case of plastic explosives, such as those in the C-4 family, for example, it is common for petroleum-derived synthetic polymers to be used for this purpose [3-5]. A natural polymer that comes to the attention of researchers is chitosan and its derivatives, which is obtained by the deacetylation of chitin, which came from fishing industry waste. It is a linear, cationic polysaccharide with protonation (addition of protons) of the amino group NH3+ (NAIR, R.S.,2019). Due to its characteristic of presenting free amino groups, chitosan has the capacity to react with several molecules, making the biopolymer with greater availability of groups pending cites chitosan among the most studied natural polymers [37]. Due to the increasing employability of natural polymers to obtain materials with high technological grade, which can be easily used in different areas, such military, engineering and health for example. The focus of this review is to evaluate the possibility of using chitosan and its derivatives as an aggregating polymer for PETN crystals, increasing the high technological grade for many diverse areas of application
Structure and Properties of Pentaeritritol Tetranitrate (Petn)
Pentaerythritol tetranitrate, also known as erythrin tetranitrate or simply called PETN (C5H8N4O12) is one of the most popular explosives in the world due to its military application, use in mining, construction and medicine. PETN has a relative effectiveness factor, defined as the relative mass of trinitrotoluene (TNT) to which an explosive is equivalent, 1.66. It is more sensitive to shock or friction than TNT. Its use is basically as a potentiator, that is, PETN is commonly used in conjunction with other compounds in explosive charges. As an example, we can mention Semtex, an explosive plastic based on PETN and RDX [4,6,7]. The chemical structure of PETN (Figure 1).
It use as mentioned, is present in several areas, such as development of explosives for military use, in mining to provide mine detonation for the extraction of mineral resources, in medicine, where it can act as a vasodilator and in civil construction for destruction of structures [4,8]. Pentaerythritol tetranitrate is an organic ester nitrate, and as such its synthesis takes place from an alcohol or polyol, and when obtained it is solid in the form of crystals and has an irritating smell. Its characteristics generally resemble TNT [5,9].
Summary of pentaeritritol tetranitrate
There are two routes for PETN synthesis: sulfonitric and nitrated. The mixture of nitric and sulfuric acids makes up the most common and most economically viable agent used in the nitrated route. This route generates many byproducts because sulfuric acid is not characterized as a good solvent for many organic substrates. Despite the generation of byproducts, this route plays an important role in the direct action in the production of nitrate esters, at both industrial and laboratory levels. With respect to nitric acid used as a reagent in esterification (or nitration) reactions, this is the essential mechanism for obtaining parental alcohol, which is considered a good solvent for organic substrates, besides having a high solubility in polyols [6,10,11].
Solid polyols such as pentaerythritol, erythritol and mannitol are commonly nitrated with nitric acid. The procedure of bubbling dry air through nitric acid to remove nitrogen oxides that may be present in the mixture is present, followed by the addition of a trace of urea to remove nitrous acid that may have been formed throughout. of the process. The mixture is cooled to approximately 0°C and excess acid is added, keeping the system stirring for a short time. Thereafter, the solution is poured into excess water and subsequently the nitrate ester is extracted or filtered, yielding a good yield in the end. In such cases, the use of excess nitric acid is essential to ensure complete nitration of the substrate. The yield obtained from the method described is close to 95% [6,12]. Figure 2, shown below, shows the synthesis reaction of PETN (Figure 2).
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