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Thermal properties and the decomposition path of more environmentally friendly polymers in both atmospheres: inert and oxidizing have been studied with a use of simultaneous TG/FTIR/QMS and DSC methods. The polymeric materials in the UV-polymerization process of cyclohexyl methacrylate and methacrylate monomer obtained from natural terpene alcohol: citronellol, using different compositions of monomers were prepared. The glass transition temperature (Tg) and thermal stability of these high solvent and chemical resistant materials were dependent on the composition and increased with increasing cyclic monomer content in the compositions. The Tg changed from 9.8˚C to 47.5˚C and a thermal stability from 195˚C to 222˚C (inert atmosphere) and from 160˚C to 217˚C (oxidizing atmosphere). The TG/FTIR/QMS analysis proved the emission of cyclohexyl methacrylate, citronellyl methacrylate and their lower molecular mass decomposition fragments, e.g., propene, cyclohexane, citronellol, citronellal, formic acid, methacrylic acid and CO, CO2 during heating of these materials in helium and air atmospheres. It indicated the same radical mechanism of their decomposition in both atmospheres which meant that the presence of oxygen did not affect the course of decomposition but reduced the initial decomposition temperature of the copolymers. [ABSTRACT FROM AUTHOR]

We have developed an analytical method to quantitatively analyze differential scanning calorimetry (DSC) experimental data. This method provides accurate determination of thermal properties such as equilibrium melting temperature, latent heat, change of heat capacity which can be performed automatically without intervention of a DSC operator. DSC is one of the best techniques to determine the thermal properties of materials. However, the accuracy of the transition temperature and enthalpy change can be affected by artifacts caused by the instrumentation, sampling, and the DSC analysis methods which are based on graphical constructions. In the present study, an analytical function (DSCN(T)) has been developed based on an assumed Arrhenius crystal size distribution together with instrumental and sample-related peak broadening. The DSCN(T) function was successfully applied to fit the experimental data of a substantial number of calibration and new unknown samples, including samples with an obvious asymmetry of the melting peak, yielding the thermal characteristics such as melting and glass transition temperature, and enthalpy and heat capacity change. It also allows very accurate analysis of binary systems with two distinct but severely overlapping peaks and samples that include a cold crystallization before melting. [ABSTRACT FROM AUTHOR]

The manufacture of flexible devices is of immense interest due to their eco-friendliness, economic prospects and wide range of applications in biocompatible devices. Therefore, this paper reports the characterization and properties of chlorinated natural rubber (Cl-NR)/polyindole (PIN) blend with different contents of nickel oxide (NiO) nanoparticles. The formation of blend nanocomposites was analysed by FT-IR, UV spectroscopy, XRD, FE-SEM, DSC and TGA. The FT-IR and UV spectra proved the effective interfacial interaction between nanoparticles and the blend matrix, with a shift in UV peak intensity with the attachment of NiO at 433 cm−1. The XRD pattern revealed the regular arrangement of the blend matrix due to the presence of nanofiller, resulting in the semicrystalline structure of the composite system. The SEM micrographs revealed a homogeneous distribution of NiO in the blend matrix. The increased degradation temperature in the TGA demonstrated the enhanced thermal stability of the NiO-filled Cl-NR/PIN blend. DSC results showed that the glass transition temperature of the composite increased with NiO content in the blend matrix. The dielectric properties and AC electrical conductivity increased significantly with increasing temperatures, as well as with the addition of nanoparticles up to 5 mass % loading. The inclusion of NiO improved the tensile strength and hardness while reducing the elongation-at-break of nanocomposites. The blend nanocomposite with enhanced thermal stability, glass transition temperature, tensile strength, AC conductivity and dielectric properties enables them to be used in highly flexible electronic applications where traditional elastomeric materials fall short. [ABSTRACT FROM AUTHOR]

In this work, the effect of uniaxial stretching on the crystallization and melting behaviors, miscibility, crystal structure, and mechanical properties of neat poly(L-lactide) (PLLA) and miscible PLLA/poly(vinyl acetate) (PVAc) blends was investigated. Stretching process could generate remarkable influence on thermal properties of neat PLLA and PLLA/PVAc blend. With stretching ratio increasing, macromolecular chains orientation and crystallization were promoted, resulting in a decrease in cold crystallization temperature and an increase in glass transition temperature, and a significant increase in crystallinity. In addition, after stretching process PVAc still inhibited the crystallization of PLLA. PLLA/PVAc blends were completely miscible blend system which had only one glass transition temperature before and after stretching process, and phase separation did not occur after stretching process. When stretch ratio increased, amorphous PVAc had greater influence on the tanδ transition peak and storage modulus increased markedly, which was benefit to the improvement of heat resistance. The α′ crystal form was produced in blends after stretching process. Stretching process with moderate stretch ratio can be utilized to improve the mechanical properties of PLLA with simultaneous enhancement of tensile strength, fracture strain and stiffness. The findings in this work provide an insightful understanding of the effect of stretching process on miscible PLLA blend and the improvement of toughness, which will facilitate the large-scale practical application of PLLA. [ABSTRACT FROM AUTHOR]

Present embodiment is an account of work done on impregnation of thermoplastic polyether imide (PEI) [ULTEM 1000] into high-temperature biphenyl-based phthalonitrile (PN) thermosetting resin to form a semi-interpenetrating network (s-IPN) in order to find an optimum composition with little compromise on glass transition temperature (Tg) and thermal stability of base resin system. The PEI has been cured with PN resin in varied ratios of 5–30 mass% in arithmetic progression to study its effect on thermal and physical properties. Fourier transform infrared spectroscopy, differential scanning calorimetry and thermos-gravimetric (TG) measurements of the s-IPN compositions were carried out to assess the extent of curing, curing enthalpy, glass transition (Tg), thermal stability and char yield, respectively. The dynamic mechanical analysis (DMA), measurements were done to ascertain the effect of PEI component in PN system on its storage modulus, Tg under dynamic load with respect to temperature. PN95 composition having PN/PEI ratio in 95:05 stoichiometry has demonstrated the best desirable properties with respect to PEI content with least compromise in Tg temperature. More than 5 mass% PEI has resulted in drastic change in Tg of s-IPN from > 673 K to 525 K in case of 10 mass% PEI as evaluated by DMA. The morphological analysis of 30% PEI-containing s-IPN showed interesting cross-linked patterns probably formed by the fibrillar orientation of the thermoplastic resin in the PN matrix. [ABSTRACT FROM AUTHOR]

The aim of this work was to improve mechanical properties of a biocomposite of polylactic acid (PLA) reinforcing with fibrillated methacrylate-silanized hemp fibre. The effect of hemp fibre on photo-oxidation and hydrolytic degradation of PLA was evaluated through a QUV accelerated weathering test. Incorporation of 20 mass% fibre filler into neat PLA matrix resulted in increased tensile and flexural modulus for 150% and 200%, respectively. The outdoor degradation of neat PLA and PLA biocomposites was simulated in a 30 days of QUV accelerated weathering test in accordance with ISO 11507 method B. Glass transition temperature (Tg) was periodically recorded to measure the rate of degradation. Differential scanning calorimetry (DSC) analysis indicated that the degradation rate of the PLA matrix of the biocomposites tended to decrease proportionally to exposure time. The statistical regression method revealed a linear relationship between ln(Mn) and lnTg (R2 = 0.96). The 20 mass% hemp/PLA biocomposite was mostly destroyed over neat PLA after 30 days. The rate of degradation tended to have a linear proportion with hemp content. The results of FTIR 13C-NMR analysis confirmed that the substantial degradation of hemp/PLA biocomposites was due to the lignin content of the hemp fibre. The sensitivity of the PLA biocomposite to UVB light and moisture absorption accelerated photo-oxidation and hydrolytic degradation to the lowest molecular weight of PLA. [ABSTRACT FROM AUTHOR]

Natural brightness of epoxy adhesives can be reduced by adding cork. Besides, when cork was magnetized, it was possible to move them depending on the properties required in each section of the adhesive bond (PAT354/2019). The main objective of this work was to study possible changes in the thermal properties of the adhesive due to the addition of magnetic cork particles. If changes were significant, the use of magnetic cork particles would be compromised. To this end, natural cork particles and magnetic cork particles, with two different particle size (53–38 and 250–125 μm) and percentage (1 and 5 v/v%), were compared as reinforcement material. Magnetic cork was obtained by co-precipitated coating, according to patent number WO2019025651. The thermal properties studied by Differential Scanning Calorimetry were activation energy of curing reaction, glass transition temperature (Tg) and thermal conductivity. Two different hardeners were studied and a factorial design (2k with k = 4) was carried out. It allowed to determine which variable or combination of variables had most impact on thermal properties. Results showed that the main parameter affecting thermal properties was the hardener, regardless of the kind of particle used. However, the presence of magnetic cork highlights further the differences found between hardeners. The conclusion of this study was that magnetic cork particles can be used as fillers in epoxy resin to make graded joints, since they do not affect the thermal properties of the resin. [ABSTRACT FROM AUTHOR]

The structural and thermal properties of sodium niobium phosphate glass are studied to analyse its suitability for immobilizing long-lived radioactive waste from nuclear reprocessing plants. Two series of sodium niobium phosphate glasses such as (A) xNb2O5–(50−x)Na2O–50P2O5 and (B) xNb2O5–(50−x/2)Na2O–(50−x/2) P2O5 (x = 0, 10, 20, 30, 40 mol.%) are prepared by the conventional melt–quenching technique. The influence of the incremental addition of Nb2O5 on the structural and thermal properties of the above two series is investigated. The FTIR and Raman spectra of these glasses revealed that the number of [NbO6] octahedral chain increases with Nb content and dominates as the major structural unit over the number of PO4 tetrahedra unit. The glass transition temperature (Tg), crystallization temperature (Tc) and melting temperature (Tm) are measured by using a differential scanning calorimeter (DSC). Other thermal stability parameters such as Hruby (KH), Angell (KA), Saad–Poulain (KSP) and Weinberg (KW), the total relaxation time of transformation and fragility are evaluated and compared between different composition of glasses. For both series A and B, the glass transition temperature increases with Nb content, suggesting the formation of a larger number of P–O–Nb or Nb–O–Nb linkages compared to the PO4 tetrahedra, resulting in a more rigid network. This is confirmed by Raman spectra which show an increase in the number of Nb–O–Nb bonds with Nb content. The major crystalline phases formed by devitrifying these glasses are identified by XRD and are found to be mainly NaPO3, NbOPO4, Na2Nb6P4O26 and Na4Nb8P4O32. [ABSTRACT FROM AUTHOR]

The study of the P3HT synthesis was carried out to investigate the effect of reaction time on thermal, optical, electronic, and morphological properties. It has been demonstrated that the variation in polymerization time over 30 min did not significantly affect the optoelectronic properties of polymers. Regarding the thermal properties, the P3HT synthesized in the shortest time presented a decomposition temperature of 20 K higher than the others. There was no difference in glass transition temperature or melting temperature, while both crystallization temperature and crystallinity content have slightly increased with polymerization time. The regioregularity of all polymers was 98%. The advantage is that a short reaction time is possible to obtain a polymer with suitable properties and, consequently, savings in the process. P3HT-30 was evaluated in a PSC active layer with the configuration of ITO/PEDOT: PSS/rrP3HT:PC71BM/Ca/Al, and PCE was 1.94%. [ABSTRACT FROM AUTHOR]

Epoxy asphalt bond coat (EABC) is one of the thermosetting polymer-modified asphalts, which has been widely employed as a strong waterproof bonding layer between the asphalt concrete and the orthotropic steel bridge deck. In the present work, the influences of asphalt content on the phase separation, viscosity, thermal stability, viscoelastic behavior, mechanical performance, pull-off strength, and adhesive performance of EABCs were characterized by various instruments. Laser scanning confocal microscopy observations showed that phase separation occurring in EABCs depended on the curing time. The asphalt merged to form large spherical particles in the continuous epoxy phase during the cure reaction. The size of asphalt particles increased in the asphalt content. Viscosities of EABCs were higher than that of the pure epoxy and increased with the asphalt content in the initial curing stage. However, the opposite trend was observed in the latter curing stage. The presence of asphalt slightly improved the glass transition temperature and the damping properties of the pristine epoxy. For EABCs, the damping behaviors slightly increased with the asphalt content. The thermal stability of the pristine epoxy was enhanced by the incorporation of asphalt. The addition of asphalt decreased the mechanical, adhesive properties, and pull-off strength of the pristine epoxy. What's more, these properties of EABCs decreased in the asphalt content. [ABSTRACT FROM AUTHOR]

The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was used to prepare biocompatible composites modified by the hemp fibers. The aim of the study was to assess the structure and selected thermal and mechanical properties of the obtained biocomposites. The morphology of samples was analyzed using a scanning electron microscope and a computed tomography analysis. The phase transitions of composites and polymer matrix were investigated using differential scanning calorimetry. Moreover, the non-equilibrium and equilibrium thermal parameters of composites and the unfilled PHBV were established based on the thermal history. Knowing equilibrium parameters, i.e., the heat of fusion for the fully crystalline materials, ΔHf (100%), and the change of heat capacity at glass transition temperature (Tg) for the fully amorphous, ΔCp (100%), composites, the degree of crystallinity, mobile, and rigid amorphous fractions were estimated. The addition of hemp fibers to the PHBV matrix caused around a two-time increase in the degree of crystallinity in reference to the unfilled PHBV. It was also observed that the addition of hemp fibers caused a decrease in heat capacity for fully amorphous material for all the biocomposites obtained. A similar relationship was observed in case of values of the heat of fusion for fully crystalline material. Simultaneously, the decrease in amorphous phase contents was noted. It was also noted that the rigid amorphous fraction exists only for the unfilled polymer matrix. Some mechanical properties of investigated materials were also measured and presented. [ABSTRACT FROM AUTHOR]