Decomposition Of Polymers Research Articles

Fabrication of High Specific Electrical Conductivity and High Ampacity Carbon Nanotube/Copper Composite Wires

AbstractA challenge is to integrate Cu with carbon nanotubes (CNTs) and form a free‐standing composite wire. This is achieved by first making a CNT filament using high concentration (20 g L−1 ) CNT dispersion, an acid‐free wet spinning process and then by replacing the polymer with copper using heat based polymer decomposition and periodic pulse reverse electroplating. It is demonstrated that indeed the specific conductivity and the current‐carrying capability (or ampacity) are increased manifold. The multiwalled CNT (MWCNT)/Cu composite wires developed in this paper have electrical conductivity σ ≈ 5.5 × 10 5 S cm−1. These MWCNT/Cu wires are 2/3rd the weight of bulk Cu wires. Their specific electrical conductivity is σρ ≈ 9.38 ×10 4 S cm2 g−1 which is 45% higher than International Annealed Copper Standard Cu. These composite wires have an ampacity of A ≈ 20 × 105 and 4 × 105 A cm−2 for 1.5 and 17 mm gauge length wires, respectively, which is four to six times higher than pure Cu depending on the wire lengths. MWCNTs volume percentage in the MWCNT/Cu wire is about 40%.

Electrocatalytic activity enhancement of N,P-doped carbon nanosheets derived from polymerizable ionic liquids

A facile preparation method was developed to obtain two-dimensional (2D) metal-free N, P-co-doped carbon nanosheets with sp2/sp3 interface derived from polymerizable ionic liquids (PIL) and ammonium nitrate (NH4NO3), exhibiting better electrocatalytic activity than that of the commercial Pt/C toward oxygen reduction reaction (ORR). The introduction of NH4NO3 can benefit the formation of carbon nanosheets structure and hierarchical porous structure due to decomposition and carbonization of polymer and gases emission resulting from ammonia nitrate, which can be confirmed by the SEM, TEM and BET results. The sp3 carbon and doping effect of heteroatoms of N, P can be investigated with the XPS, Raman and NEXAFS spectroscopy. The present work developed a facile method to prepare heteroatom-co-doped carbon as metal-free catalyst toward ORR with superior catalytic performance. Two-dimensional carbon nanosheets doped with N, P atoms can be successfully prepared via pyrolysis process of the polymerizable ionic liquids ([Hvim]DHP) and NH4NO3, demonstrating superior electrocatalytic performance toward oxygen reduction in alkaline media.

Thermal and evolved gas analyses on Michael addition oligomers of acrylic acid

Michael addition reaction of acrylic acid has caused thermal runaway of acrylic acid, thereby causing many explosion and fire accidents in the chemical industries. The aim of the present study is to gain a better understanding of the reaction mechanisms of Michael addition oligomers of acrylic acid (MAO) during a runaway polymerization on the basis of thermal and evolved gas analysis. The Michael addition reaction of acrylic acid occurs at a temperature lower than the temperature at which thermal polymerization occurs, triggering the initiation of thermal polymerization and the associated thermal runaway, and after the thermal runaway, the pressure generated by the reaction with the product, MAO, can cause tank rupture. We discussed the reaction mechanisms of MAO including thermal polymerization and thermal decomposition on the basis of high-sensitivity reaction calorimetry and evolved gas analysis of MAO and its thermal polymer. From the results of the thermal analysis using Calvet-type calorimeter and thermogravimetry–differential scanning calorimetry-mass spectrometry-infrared spectrometry (TG-DSC-MS-IR), MAO can be polymerized exothermically at more than 180 °C, and its thermal polymer decomposes to propanoic acid, carbon dioxide, ethylene and low-molecular hydrocarbons such as methane, ethane, and cyclopropane at more than 195 °C. Michael addition oligomerization of acrylic acid was found to not only thermally initiate free radical polymerization due to its heat generation but also increase the possibility of the tank explosion after runaway polymerization due to the large pressure generation induced by thermal decomposition of MAO polymer.

Mechanical and Thermal Properties of Biocomposites Based on Polyethylene from Renewable Resources Modified with Ionic Liquids

Biocomposites based on polyethylene from renewable resources derived from sugar cane as raw material were modified with phosphonium ionic liquids. Mechanical properties and thermal behavior of modified biocomposites in air atmosphere were studied. The influence of ionic liquids (IL) on thermal degradation of biocomposites based on polyethylene from renewable resources was studied by thermogravimetric analysis (TGA). Three phosphonium ionic liquids containing phosphorus both in cation and anion segments were used. Biocomposites were filled with 10 wt% and 20 wt% hemp fiber. In general, modification of biocomposites reinforced with 20 wt% hemp fiber with phosphonium ionic liquids resulted in improvement of tensile properties, i.e. tensile strength, as well as impact strength and hardness, whereas Young’s modulus decreased compared to unmodified biocomposites. Thermal degradation of biocomposites modified with phosphonium ILs containing phosphate anion proceeds in two steps corresponding to overlapping processes of degradation of polymer matrix and decomposition of hemp fibers components. Conversely, biocomposites modified with ionic liquid based on phosphinate anion exhibit more complex degradation behaviour, as well as slightly enhanced thermal stability. It may indicate that anion segment of ionic liquids influences the thermal behavior of ILs modified biocomposites.

Особливості термодеструкції вторинної полімерної сировини

The analysis of modern chemical ideas about thermal destruction of secondary polymers (SP) as a source of valuable energy components, which are formed after their decomposition: gas component, synthesis oil and pyrocarbon has been carried out. It is shown that regardless of the composition of the secondary polymeric materials, thermal destruction takes place by the classical radical chain mechanism with the formation of a gas mixture of hydrocarbons, alkane-alkene mixture of different hydrocarbons (monomers and oligomers of SP) and pyrocarbon, which includes condensed aromatic structures. The dependence of the formation of monomers as products of thermal destruction of secondary polymers on their cohesion energy density (Ecog, kJ/mol) has been shown. In a number of works the methods of thermal-oxidative and thermal destruction of polymers of different composition and structure have been considered, however, only a small number of works are devoted to the study of chemical transformations of secondary polymers, and even less to their mixtures. It is stated that the resistance of polymers (including secondary) to heat and the rate of their thermal decomposition depends on the chemical structure of the polymer or mixtures thereof. Completion of thermal processes of decomposition of secondary polymers takes place by recombination of formed radicals or their disproportionation with the formation of double bonds at the ends of macromolecules, as well as changes in fractional composition and formation of branched and spatial structures. It is stated that in the case of thermal destruction of secondary polymers that contain one (PVC) or several (PTFE) halogen atoms, there is almost quantitative release of hydrogen halides (HHal), which require additional disposal. Attention is also paid to the fact that the use of catalysts of different chemical nature in the thermal destruction of secondary polymers leads to a significant difference in the yield of gaseous and liquid products of radical-chain transformations.

Development of compositions from waste of polypropylene and polyethylene terephthalate and research of their technological and thermal properties

The article presents the results of determining the melting point and the melt flow rate, Vicat heat resistance of a composition made of polypropylene waste from the study of polyethylene terephthalate. It has been established that with an increase in the content of polyethylene terephthalate, the melting point and heat resistance according to Vicat increase, and the melt flow rate of the compositions decreases. The Hildebrand solubility parameters and the packing density of macromolecules are calculated using the increment method. The thermal characteristics of the compositions were investigated by the derivatography method. Their decomposition onset temperature, decomposition rate, and the amount of energy consumed for the decomposition of polymers and polymer compositions were determined. It was revealed that the compositions of polyethylene terephthalate with secondary polypropylene are more thermostable than compositions of polyethylene terephthalate with primary polypropylene.

Utilizing Fused Filament Fabrication for Printing Iron Cores for Electrical Devices.

This work details a polyolefin-elastomer-based binder system to prepare fused filament fabrication (FFF) filaments and print cores for coils for electrical engines. The processability, homogeneity, and thermal properties of the polyolefin-elastomer-based filaments are explored. A two-step debinding and sintering process was established for manufacturing dense iron parts. Results indicate the developed filaments possess superior printing and sintering (at 900°C) performance, yielding only 20% weight loss by polymer decomposition and 14 vol.% shrinkage. This indicates that the FFF technique potentially enables printing of innovative electric motor designs. The designed FFF filaments could be loaded with 80 wt.% Fe powder while keeping a decent melt-viscosity for the printing process. Due to the high metal loading, dense iron parts could be sintered without bending or deformation.

Current Status of Pseudomonas putida Engineering for Lignin Valorization

Lignin, a complex aromatic polymer, is a structural component of plant biomass. It decomposes with difficulty because of its rigidity properties, however, lignin valorization is essential for the economics of lignocellulosic biorefineries. Pseudomonas putida has been extensively investigated as a promising host strain for lignin valorizations due to intrinsic traits, such as low nutritional requirement, high tolerance to toxicity, and metabolic versatility with a wide spectrum of substrates, such as aromatic compounds. Although a naturally occurring, lignin-utilizing P. putida strain has been reported, it is necessary to engineer the genome of P. putida for efficient lignin utilization. For biological lignin valorization, the decomposition of lignin polymer to low-molecular weight compounds and transformation of lignin-derived aromatic compounds to value-added chemicals is essential. Various tools of synthetic biology have been developed for the genome engineering of P. putida; efforts in metabolic engineering have been made to expand aromatic substrate specificity and to improve productivity of value-added chemicals. Development of high-performance bio-parts and biosensors for lignin valorization has also been done. In this review, we present recent research on genome engineering tools developed for P. putida and metabolic engineering employed in P. putida to improve lignin valorization.

Interstitial Bimetallic Doping into Carbon Nanofibers By Electrospinning Technique: Electrochemical Supercapacitors

Last decade, the supercapacitors (SCs) are well-recognized as promising energy storage devices because of their high-power density, long cyclic life, fast charge and discharge rates, and facile operational mechanism. Carbon materials such as active carbon, carbon nanotubes (CNTs), mesoporous carbon, graphene, etc. are highly suited electrode materials for supercapacitors owing to their high specific surface area, high electronic conductivity, and chemical stability against the corrosive electrolytes. In recent years, the mono or bimetallic transition metal doping into carbon materials has received immense attention because they significantly enhance the mechanical strength, electrochemical and physicochemical properties. Therefore, it is expected that the bimetallic doping into carbon nanofibers (CNFs) can be an innovative electrode for supercapacitors as they might improve the electrocatalytic and corrosive properties. In this work, the nickel (Ni) - copper (Cu) doping into the CNFs were prepared by a facile and controlled cost-effective electrospinning technique followed by stabilization of electrospun nanofibers. The prepared Ni-Cu doped CNFs were carbonized in the furnace for the partial decomposition of the polymer and irregular decomposition of the metallic acetate to complete NiCu in CNFs. By analyzing morphological characterizations, the NiCu was interstitially doped into CNFs. The surface analysis results revealed that NiCu doped CNFs exhibited a highly porous structure with a specific surface area of 244 m2/g and a large pore volume. The prepared NiCu doped CNFs were applied as the electrode and demonstrated exemplary electrochemical property with a reasonable specific capacitance of 337.5 F/g at 10 mV/s in aqueous 1M Na2SO4 electrolyte.

Characteristics of Aerosol Formation and Emissions During Corn Stalk Pyrolysis

The inevitable emission of aerosols during pyrolysis can negatively affect the downstream process and even pollute the environment. In this work, the characteristics of aerosols were investigated during corn stalk pyrolysis at 400–900 °C. The effects of other operation conditions on the aerosol emissions were also probed with online and offline instruments. Results show the yield of aerosol presents a regular change with temperature in a wide range ratio of 3.4–8.7 wt.%. The aerosol size distribution reveals a unimodal form mainly in the 1.1–2.1 μm accumulation range and the maximum emission achieved is about 35 mg/g for SR and SP at 500 °C. Nevertheless, SL gives about 34 mg/g at 600 °C. High temperature promotes the decomposition of polymers into partciles with small diameter (less than PM1.0). The microtopography of aerosol presents spherical droplets, elongated-like liquid and solid particles that form heterogenous or homogeneous aggregations, that also happen on account of collisions. Aerosols contain mostly organic matter, a small amount of salt and over 50% of volatile organic carbon molecules (VOCs) in the total organic carbon (OC). Proper gas flow, high vapor concentration and longer path way boost the yield of bio-oil and reduce the emission of aerosols. The direct contact is beneficial for adequate extraction, but also causes additional solvent emissions.

Phase evolution, microstructure and dielectric properties of electrospun Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3

Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 or simply BZT-0.5BCT has attracted increasing attention due to its excellent ferroelectric properties and lack of lead. BZT-0.5BCT nanofibers were fabricated by sol–gel assisted electrospinning and post-calcination process. Different types of analysis were utilized to study phase evolutions and characterization of calcined fibers. TGA indicated three stages of polymer decomposition at temperatures below 500 °C. FTIR spectroscopy revealed the presence of acetate salts of inorganic precursors in electrospun fibers. Also, it was determined that the formation of oxides started at temperatures around 300 °C and intensified with a rise in temperature. In keeping with DSC and FTIR results, XRD analysis revealed a low crystallization temperature of 550 °C for the perovskite phase. The room-temperature Raman spectroscopy demonstrated the coexistence of both orthorhombic and tetragonal phases at 900 °C and higher temperatures. SEM images illustrated the stability of fibrous morphology up to 1000 °C. High-temperature XRD showed that the curie temperature of nanofibers is between 120 and 150 °C. The dielectric constant of calcined fibers at 900 °C was measured to be 2283.

Physicochemical Comparison of Chitin Extracted from Horseshoe Crab (Limulus polyphemus) Exoskeleton and Exuviae

AbstractIn this paper, horseshoe crab exoskeleton and exuviae were collected on the coasts of Yucatan and physicochemical studies were carried out. Samples from different sections of the exoskeleton were taken to evaluate chitin content and properties in order to be compared with exuviae. The isolation of chitin was realized by chemical processes involving deproteinization, demineralization and discoloration. Physicochemical properties of chitin extracted from both sources were compared in terms of characterization analysis in particular achieved under EDX, FTIR and calorimetric techniques (DSC and TGA). In such comparative analysis lies the importance to establish differences or similitudes in chitin contents, structure, etc. Scanning Electron Microcopy was conducted on exuviae and exoskeleton selected parts in order to identify horseshoe crab structure and surface morphology. Differential scanning calorimetry was focused on changes in physical and chemical structures at different samples showing two endothermic peaks related to the complete elimination of hydroxyl groups attached to polysaccharide rings. TGA thermograms were characterized by endo and exotherms corresponding to water evaporation and decomposition of polymer respectively. Exoskeleton SEM images shown a tubular network and porous surface while exuviae exhibited irregular surface and diatom unicellular microalgae embedded. Calorimetric measurements confirmed that exuviae is richer in chitin than exoskeleton and that the main allotropic crystal structure corresponds to α‐chitin. FTIR analysis supported these results by exhibiting different absorption bands corresponding to α‐chitin.

Mechanically durable and self-healing super-hydrophobic coating with hierarchically structured KH570 modified SiO2-decorated aligned carbon nanotube bundles

We prepared stably and hierarchically structured particles (ACNTB-SiO2-KH570) composed of silane coupling agent 3-methacryloxypropyltrimethoxysilane (KH570) modified nano-SiO2 and aligned carbon nanotube bundles (ACNTB), and developed a mechanically durable super-hydrophobic composite coating from epoxy (EP) adhesive precursor and ACNTB-SiO2-KH570 by dripping method, without using any fluoro-containing compounds. The results show that ACNTB-SiO2-KH570 particle film possesses excellent super-hydrophobicity because of the complicated nanotexture of ACNTB-SiO2-KH570. The composite coating with a very small content (4.3%) of ACNTB-SiO2-KH570 can show excellent super-hydrophobicity owing to the formation of rough surface with micro/nanoscale hierarchical structure. The water contact angle (CA) and sliding angle (SA) of the composite coating can reach 158.8 ± 2.5° and 2.5 ± 0.5°, respectively. Moreover, the composite coating not only displays good antifouling and self-cleaning performance, but also retains super-hydrophobicity after sand falling test, water jet impact and sandpaper abrasion cycles. The excellent mechanical durability of the composite coating is attributed to the synergistic effects of high strength and toughness ACNTB-SiO2-KH570 and the good interface interaction of the different components in coating. The composite coating can show good adhesions to various substrate and exhibit super-hydrophobicity. Furthermore, the damaged composite coating can recover its super-hydrophobicity after being heated to 300 °C, owing to the combination of the decomposition of partial EP polymers and the migration of SiO2 to the coating surface.

IR spectroscopy and X-ray diffraction analysis of industrial polyvinyl chloride suspension

In terms of the contemporary plastic industry, world production of polyvinyl chloride is second only to polyolefins. Recyclable by almost all known methods, polyvinyl chloride offers high strength, good insulating properties, as well as resistance to acids, oxidising agents and solvents. At the same time, the ability to process polyvinyl chloride into products is limited by its lack of stability at high melt viscosity temperatures, since hydrogen chloride released during its heating catalyses further process of polymer decomposition. Thus, due to the softening temperature of polyvinyl chloride being higher than its decomposition temperature, it cannot be processed in its pure form. Consequently, functional polyvinyl chloride-based materials tend to be composites. By varying the composition of mixtures, plastic masses characterised by either very soft (plastic compounds) or hard (vinyl plastics) structures can be obtained. The properties of polyvinyl chloride-based polymer products are largely determined by the structure and morphology of the polymer. In the present work, the properties of industrial suspension polyvinyl chloride (Sayanskkhimplast JSC, Irkutsk Oblast) were studied in detail for the first time. The molecular weight of the polymer determined by the viscometric method was 1.0 · 106. Thermogravimetric analysis showed that polyvinyl chloride mass loss started to occur at 160 °C. Following the complete IR band assignment of the polymer, the polyvinyl chloride under study was established to contain no foreign substances (impurities of stabilisers, emulsifiers and additives). The diffraction curve of the polymer was established to be qualitatively similar to equivalent partially crystalline polymers. Two amorphous halos were detected at 2θ of 24° 30′ and 39° 30′ below a group of crystalline peaks. The crystallinity degree of polyvinyl chloride was determined and mechanisms for the formation of its regular and irregular structure were proposed.

Synthesis, characterization and applications of poly(vinyl chloride) nanocomposites loaded with metal oxide nanoparticles

Metal oxide (i.e., Fe2O3, ZnO and TiO2) nanoparticles (NPs) have been prepared and investigated by various techniques with the objective of synthesis of nanocomposites thin films based on poly(vinyl chloride) (PVC) as a matrix. Different loadings of metal oxide NPs (i.e., 2.0, 5.0, 10.0 and 15.0 wt%) were incorporated in PVC followed by solution casting. The prepared film samples were characterized by X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), dynamic mechanical analysis (DMA), thermal and electrical measurements. Also, the antibacterial activity was tested against Gram-positive (i.e., Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (i.e., Escherichia coli and Pseudomonas aeruginosa). The results were discussed in relation to metal oxide NPs content and type. XRD of the prepared nanocomposite films was almost the same as that of mixed ZnO metal oxide NPs with an amorphous region of PVC. Raman spectra suggested that ZnO NPs were just physically inserted into PVC matrix. SEM revealed a homogeneous distribution of the NPs on using 10 wt% in PVC matrix, while the NPs agglomerations at higher content (i.e., 15 wt%) were formed. The dynamic mechanical results, as a function in temperature, indicated an increase in the storage and loss moduli and a decrease in loss factor tan δ with shifting to higher glass transition temperature, with increasing metal oxide NPs content up to 10 wt%. Thermal gravimetric analysis revealed that utilizing Fe2O3 and TiO2NPs in PVC matrix improved thermal stability of PVC in comparison with ZnO NPs with catalytic behavior and polymer decomposition acceleration. Metal oxide Nps increased the electrical conductivity of PVC, the electrical conductivity values were found to be in the order of 10−13 for ZnO, while it is in the order of 10−11 for Fe2O3 and TiO2. This finding is highly recommended such composites to be used in antistatic applications as the needed range for such application is 10−9–10−14Ω−1 cm−1. Metal oxide nanocomposites improved the antibacterial activity of PVC toward both types of bacteria and can be used as an effective antibacterial agent in biomedical healthy applications.

Change in The Structure of Polyme Polyacetylene When Irradiated by Low-Energy X-Ray Taken by Tem

Plastics or synthetic plastics are products that are not naturally available, but are made by humans. They have a long decomposition time, can last up to hundreds, thousands of years (plastic bottles, plastic straws and plastic bags take 10 years to 1000 years to decompose). Plastic waste is the plastic products after being used and are discharged into the environment such as plastic bags, plastic bottles, plastic straws, synthetic plastics. Here polymer being studied is polyacetylene, polyacetylene is a plastic film, polyacetylene is projected by low-energy x-rays with different projection doses, thereby analyzing the structural change of the polyacetylene. The changing structure leads to a change in polymer decomposition time, which can reduce environmental pollution.

Porosity and oxygen vacancy engineering of mesoporous WO3 nanofibers for fast and sensitive low-temperature NO2 sensing

A facile electrospinning technique combined with varied heating rates was developed to tune the porosity and oxygen vacancy of mesoporous WO3 nanofibers. The porosity of WO3 increased as the heating rate increased gradually up to 10 °C/min, but decreased after that value because of the destruction of WO3 fiber-like structure. WO3 nanofibers with a heating rate of 10 °C/min (WO3-10) thus exhibited the largest pore size and the highest surface area. Simultaneously, as the heating rate increased, the oxygen vacancy concentration increased visibly because of locally lower oxygen partial pressure during the rapider decomposition of organic polymer at higher heating rate. Consequently, the low-temperature NO2 sensing performances of WO3 were modulated by the heating rate. The best sensing performances were found for the WO3-10 nanofibers, displaying the highest response of 101.3 and the shortest response time (125 s)/recovery time (231 s) toward 3 ppm NO2 at 90 °C. These excellent sensing characteristics were attributed to the high gas diffusion coefficient and strong absorbing capability for surface O2− species and NO2 gas molecules, originating from the high porosity, high oxygen vacancy concentration, and high surface area of the WO3-10 nanofibers.

High-effective preparation of 3D hierarchical nanoporous interpenetrating network structure carbon membranes as flexible free-standing anodes for stable lithium and sodium storage

Ideal lithium/sodium storage requires a simple and effective design of carbon-based anodes with appropriate morphologies/microstructures and excellent flexibility. Herein, an advanced flexible interpenetrating network carbon membrane with 3D hierarchical nanopore structure is designed and fabricated inspired by porous membrane technology via nonsolvent induced phase separation (NIPS) and carbonization. The interpenetrating network structure in the carbon membrane is generated by the NIPS membrane formation process, while the 3D hierarchical nano-porous structure is obtained from polymer decomposition during carbonization. The unique synergistic effect between the even interpenetrating network structure and the developed 3D hierarchical porous structure not only ensured structural integrity of the anodes and provided a high-volume ion transmission reservoir, but also endowed carbon membranes with multiple active sites for energy storage. As flexible anodes, the resulting carbon membranes achieved enhanced electrochemical properties by showing maximum reversible capacitance of 351.8 mA h g−1 in lithium storage and 237.4 mA h g−1 in SIBs at a current density of 50 mA g−1. In both LIBs and SIBs, the carbon membranes exhibit outstanding rate performance even at a high current density of 2000 mA g−1. They also show excellent long-term cycling stability with the coulomb efficiency maintained nearly 100 % after the first few cycles. Therefore, this work provides a simple and high-effective cross-disciplinary approach through membrane technology and carbon materials for the production of high-performance, low-cost carbon membranes for large-scale application anodes.

Di-tert-butylphosphate Derived Thermolabile Calcium Organophosphates: Precursors for Ca(H2PO4)2, Ca(HPO4), α-/β-Ca(PO3)2, and Nanocrystalline Ca10(PO4)6(OH)2.

Thermally and hydrolytically unstable di-tert-butyl phosphate (dtbp-H) has been used as synthon to prepare discrete and polymeric calcium phosphates that are convenient single-source precursors for a range of calcium phosphate ceramic biomaterials. The reactivity of dtbp-H toward two different calcium sources has been found to vary significantly, e.g., the reaction of Ca(OMe)2 with dtbp-H in a 1:6 molar ratio in petroleum ether forms a mononuclear calcium hexa-phosphate complex [Ca(dtbp)2(dtbp-H)4] (1), whereas the change of calcium source to CaH2, in a 1:2 molar ratio under otherwise similar reaction conditions, yields the calcium phosphate polymer, [Ca(μ-dtbp)2(H2O)2·H2O]n(2). Compounds 1 and 2 have been extensively characterized by various spectroscopic and analytical techniques. The solid-state structures of both 1 and 2 have been determined by single-crystal X-ray diffraction studies. In discrete molecule 1, the central calcium ion is surrounded by two anionic dtbp and four neutral dtbp-H ligands in an octahedral coordination environment. Compound 2 is a one-dimensional polymer in which adjacent calcium ions are connected through double dtbp bridges. Solid-state thermolysis of bulk 1 in air leads to the exclusive formation of calcium metaphosphate β-Ca(PO3)2 in the entire temperature range of 400-800 °C. Thermal decomposition of polymer 2, however, can be fine-tuned to produce either α-Ca(PO3)2 or β-Ca(PO3)2 depending on the thermolysis conditions employed. Although the sample sintered at 600 °C produces exclusively α-form of Ca(PO3)2, the sample annealed at 800 °C or above produces β-form. Both α- and β-forms can also be successively formed one after other by a slow heating of a freshly prepared 2 on the powder diffractometer sample holder. Additional forms of ceramic phosphates have been prepared by solvothermal conditions because of the highly labile nature of the tert-butoxy groups of dtbp in 1 and 2. Solution decomposition of either 1 or 2 in boiling toluene at 140 °C in a sealed tube produces calcium dihydrogen phosphate [Ca(H2PO4)2·H2O] as the only product in the form of single crystals. Solution thermolysis of 2 in protic solvents such as water and methanol can be biased to produce other calcium phosphate biomaterials such as hydroxyapatite [Ca10(PO4)6(OH)2]and calcium monohydrogen phosphate [Ca(HPO4)] in the presence of additional calcium precursors such as CaO and Ca(OMe)2, respectively.

Features of some Polymer Building Materials Behavior at Heating

The problems of reducing combustibility and increasing fire resistance of some polymer building materials are considered. And the toxicity of the gaseous products of their thermal degradation was evaluated both individually and in various combinations with each other. The features of thermal degradation and the loss of mechanical properties under the influence of a flame of polymer building materials were studied. The following samples were used: water pipes based on polyethylene; Tarkett linoleum, Ondex roofing products, Rolvaplast PVC profile panels; structural panels of the company "Polygal"; facing tile based on phenol-formaldehyde oligomers. The processes occurring during pyrolysis and combustion are considered, the results of a study of the combustibility and mechanical properties of polymer building materials based on polyethylene, polyvinyl chloride, polycarbonate, phenol-formaldehyde and epoxy oligomers under the influence of a flame are presented. For the studied building polymer materials, the products of pyrolysis and combustion were studied; their ignition and self-ignition temperatures, and also the flame propagation velocity were measured. The data on the toxicity of the products of their combustion, both individually and under combined action, are summarized. Also, for the studied polymer building materials, the losses of heat resistance, toughness, and flexural strength under the influence of a flame were studied. Thermogravimetric analysis of Rolvaplast PVC panels and Poligal polycarbonate panels allowed us to determine the maximum temperatures and activation energies of the polymer decomposition process. It was concluded that if the material is recognized as non-combustible or slow-burning, it will not always be fire resistant, since its strength and thermal properties can sharply decrease already in the first seconds of flame exposure.