Onset Decomposition Temperature Research Articles

Analysis of materials for elaboration of national products

This article analyzes the information about the developed, introduced, industrially mastered domestic composite materials on domestic raw materials according to the developed technologies for their production and application in industry, which allows recommending these developments as import substitution of dishes used by Russian manufacturers with non-stick coating of composite materials. The reducing of the dependence of the imported raw materials and components is not just a slogan. It is the prospect of using PTFE in dispersion-filled coatings due to a number of its unique properties: an abnormally low friction coefficient among structural materials (0.04-0.05 for steel without lubrication); high temperature resistance (decomposition onset temperature 418 ° C); high chemical stability (reacts only with melts of alkali metals, elemental fluorine at high temperatures); possesses excellent insulating properties. Based on the data on the Russian-made fluoroplast containing materials and coatings for various operational purposes created and introduced into production, it can be confidently stated: each of the developments individually and in the complex is import-substituting for technological, technical and quality indicators performed on domestic raw materials.

Poly(lactic acid)/Acrylonitrile Butadiene Styrene Nanocomposites with Hybrid Graphene Nanoplatelet/Organomontmorillonite: Effect of Processing Temperatures

Abstract This work reports the preparation and characterization of poly(lactic) acid/acrylonitrile butadiene styrene/graphene nanoplatelets/Cloisite C20A montmorillonite (PLA/ABS/GnP/C20A) nanocomposites via melt blending. The clay is hybridized with graphene to increase its dispersion in the polymer matrix. The melt processing temperatures play a vital role in the properties of the resulting nanocomposites in dictating the extent of thermal stability and dispersion of the fillers. The hybrid nanocomposites were characterized for stress-strain, thermal, chemical, and morphological properties. The findings were that there was an increase in the mechanical properties in terms of tensile strength and Young's modulus with the PLA/ABS/GnP/C20A at the high-temperature profile having the highest values of 43.1 MPa and 2533 MPa. The elongation at break increases slightly, due to the brittle properties of GnP. It was found that the dispersion of the fillers increased with increasing temperature profiles, as revealed by the morphological analysis by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The void size was also observed to be smaller and more homogenous with increasing temperature. However, in terms of thermal degradation analysis, the addition of fillers increases its thermal stability as the decomposition onset temperature increases by 22.5°C.

Hydrogen storage properties of magnesium borohydride infiltrated in silica aerogel using solvated and pressure methods

Abstract In this work, the polymorphic α-magnesium borohydride form was infiltrated by wet impregnation using tetrahydrofuran (THF) as solvent and subcritical carbon dioxide as innovative drying process. Pressure infiltration at high temperature was also tested as another promising method for confinement. After infiltration, onset decomposition temperature was reduced from 280 °C into 220 °C using high pressure infiltration and down to 100 °C using wet impregnation followed by CO2 drying. Faster kinetics were obtained in both cases due the possible particle size reduction in the precipitation process of the complex hydride and the presence of silica, which could behave as an additive. It is the first time that this complex borohydride is 6.1 wt% H2 reversible performing the rehydrogenation at moderate conditions of 390 °C and 120 bar H2 using silica as support. Different values were obtained after infiltration method due to the different intermediates that were obtained after the first dehydrogenation.

Overcoming the potential drop in conducting polymer artificial muscles through metallization of electrospun nanofibers by electroplating process

Electrochemical actuators made of conducting polymers are one of the major types of artificial muscles that have attracted much attention in recent years. However, these artificial muscles suffer from potential drop along the length, which undermines their performance in applications requiring longer muscles. This study is aimed at enhancing the performance of this type of artificial muscles through overcoming the potential drop along the length. This is implemented using copper electroplating and creating a full-length highly conductive nanofibrous layer. Polyurethane/copper/polypyrrole (PU/Cu/PPy) nanofibrous artificial muscles were fabricated by combining electrospinning, electroplating and electrochemical polymerization. The copper electroplating affected many features of the PU nanofibrous layer including surface morphology of nanofibers, thermal, mechanical and electrical properties. Average diameter of the PU nanofibers was measured as 306 ± 48 nm, which increased significantly by increasing the duration of copper electroplating. By copper electroplating for 20 s, the onset temperature of nanofibers thermal decomposition was increased from 249 to 302 °C. Additionally, using this process, the sample Young’s modulus was increased from 2.20 ± 0.21 to 62.32 ± 5.42 MPa while its elongation at break was decreased from 173.84 ± 14.22 to 94.81 ± 10.96. After copper electroplating for duration as low as 20 s, the electrical conductivity of nanofibers was increased by more than 200 times from 48.90 ± 1.10 to 10 103.06 ± 14.28 S cm−1. Electrochemical polymerization of pyrrole on the surface of metalized nanofibers increased the average diameter of produced nanofibers to 1030 ± 102 nm. Providing an electrical connection along the entire length of artificial muscle resulted in enhanced electroactive property and hence final bending actuation of 88° for a cycle potential between −0.8 V and 0.5 V at a scan rate of 5 mV s−1 was observed. The nanofibrous artificial muscle fabricated by the proposed method has immense potential for use in practical applications.

Significantly Strengthening Epoxy by Incorporating Carbon Nanotubes/Graphitic Carbon Nitride Hybrid Nanofillers

AbstractNovel hybrid nanofillers consist of carbon nanotubes (CNTs) and graphitic carbon nitride (g‐C3N4) are prepared for the enhanced mechanical properties of epoxy by improving the dispersion of CNTs. 2D planar structure, large surface area, and plentiful of surface reactive groups of g‐C3N4 efficiently resist the microcrack propagation, impede the thermal transfer, and provide chemical bonding with epoxy chains. The well‐dispersed CNTs by anchoring on g‐C3N4 surface promotes the efficient transfers of stress, and supply the stronger mechanical interlocking for interfacial bonding. The significantly enhanced mechanical properties of epoxy containing hybrid nanofillers are based on the synergistic effects between CNTs and g‐C3N4. Compared with neat epoxy, the tensile strength, tensile modulus, and storage modulus of epoxy containing 0.5 wt% hybrid nanofillers (CNTs: g‐C3N4 = 1: 9, w/w) below glass transition temperature (Tg) are increased by 37.65%, 29.36%, and 32.92%, respectively. Meanwhile, the Tg, onset decomposition temperature and char residue are also obviously raised.

Effect of Composite Emulsifiers on Thermal Decomposition Characteristics and Detonation Velocity of HANFO Emulsion Matrices

AbstractTo study the effect of composite emulsifiers on the thermal decomposition characteristics and detonation velocity of heavy ammonium nitrate‐fuel oil (HANFO) emulsion matrices, the thermal decomposition process of the emulsion matrices prepared by five different composite emulsifiers was studied by thermogravimetry−differential thermogravimetry (TG‐DTG) under four heating rates. The thermodynamic parameters such as activation energy and pre‐exponential factor of the five emulsion matrices were calculated by the Ozawa method and the Kissinger method, and the mechanism function was solved by the Šatava‐Šesták method. The detonation velocity of HANFO emulsion matrices was measured using a discrete‐point electric method. The results showed that the decomposition onset temperature of the HANFO emulsion matrix first increased and then decreased with the addition of emulsifier T152. The emulsion matrix with a Span80 : T152 ratio of 1 : 2 exhibited the highest decomposition onset temperature of 171 °C. Among the five samples, sample 4 had the highest activation energy (108.71 kJ mol−1), indicating that the thermal stability of sample 4 was greater than those of the other four samples. The detonation velocity test results revealed that the composite emulsifier strongly affected the detonation performance of HANFO. The sample with a Span‐80 : T‐152 ratio of 1 : 2 had a higher detonation velocity than the other four samples.

Synthesis, Characterization, and Crystal Structures of Two New Manganese Aceto EMIM Ionic Compounds with Chains of Mn2+ Ions Coordinated Exclusively by Acetate.

We synthesized and determined crystal structures of two manganese(II) aceto EMIM coordination compounds with simplified empirical formulas Mn4(OAc)10[EMIM]2 and Mn4(OAc)10[EMIM]2·2H2O. Both compounds feature extended chains of Mn2+ octahedrally coordinated exclusively by acetate anions, which has been observed for the first time. The EMIM moieties and water molecules participate in hydrogen bonding with acetate anions but do not directly interact with the metal cation. Both compounds have melting temperatures around 120 °C and can be considered as (non-room-temperature) ionic liquids. The structural arrangement represented by the two title compounds is robust in terms of accommodating other types of cations and allows for tuning of physical properties of the ionic liquid by means of cation substitution. Thermal analysis results obtained using TGA–DSC and VT IR suggest melting phase transitions around 120 °C, followed by structural rearrangement in the molten state taking place around 140–160 °C. Compounds I and II have a higher thermal stability range compared to [EMIM][OAc] ionic liquid, with an onset decomposition temperature above 260 °C.

Recyclable polymer functionalization via end-group modification and block/random copolymerization

Recyclable polymers offer a great opportunity to address the environmental issues of plastics. Herein, functionalization of recyclable polymers, poly ((R)-3,4-trans six-membered ring-fused GBL) (P ((R)-M)), were reported via end-group modifications and block/random copolymerizations. Di-n-butylmagnesium was selected to catalyze ring-opening polymerization (ROP) of (R)-M in the presence of a series of functional alcohols as the initiators. Block/random copolymerizations of (R)-M and ε-caprolactone (ε-CL), l-lactide (L-LA) and trimethylene carbonate (TMC) were performed to control the onset decomposition temperature (Td), melting temperature (Tm) and glass transition temperature (Tg). These functionalized recyclable polymers would find broad applications as the sustainable plastics.

Encapsulation of Bioactive Compounds from Aloe Vera Agrowastes in Electrospun Poly (Ethylene Oxide) Nanofibers.

Aloe Vera is an ancient medicinal plant especially known for its beneficial properties for human health, due to its bioactive compounds. In this study, nanofibers with antioxidant activity were successfully obtained by electrospinning technique with the addition of a natural Aloe Vera skin extract (AVE) (at 0, 5, 10 and 20 wt% loadings) in poly(ethylene oxide) (PEO) solutions. The successful incorporation of AVE into PEO was evidenced by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis (TGA) and antioxidant activity by 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging (ABTS) and ferric reducing power (FRAP) assays. The incorporation of AVE introduced some changes in the PEO/AVE nanofibers morphology showing bimodal diameter distributions for AVE contents in the range 10-20 wt%. Some decrease in thermal stability with AVE addition, in terms of decomposition onset temperature, was also observed and it was more evident at high loading AVE contents (10 and 20 wt%). High encapsulation efficiencies of 92%, 76% and 105% according to DPPH, FRAP and ABTS assays, respectively, were obtained at 5 wt% AVE content, retaining AVE its antioxidant capacity in the PEO/AVE electrospun nanofibers. The results suggested that the obtained nanofibers could be promising materials for their application in active food packaging to decrease oxidation of packaged food during storage.

Comparison of thermal and fire properties of carbon/epoxy laminate composites manufactured using two forming processes

AbstractCarbon/epoxy composites have been widely used in the aviation industry. However, the flammability of epoxy resins is of great concern within the industry. Currently, vacuum bag and autoclave forming processes are the most commonly used processes for composites. To compare the thermal and fire properties of carbon/epoxy laminate composites manufactured using these two forming processes, a comprehensive experimental investigation and theoretical analysis was carried out in this work. The glass transition temperatures and epoxy resin matrix content in composites were determined. Several thermal and fire properties were quantitatively evaluated, including onset decomposition temperature, time to ignition, mass loss rate (MLR), and heat release rate (HR). The morphologies of specimens before combustion were also observed. For vacuum bag (VB)‐C/ELC and A‐C/ELC, the critical heat flux (14.48 and 20.56 kW m−2), thermal response parameter (165.56 and 204.49 kW s1/2 m−2), heat of gasification (9.13 and 20.10 MJ kg−1), and theoretical heat of combustion (33.27 and 43.82 MJ kg−1) were calculated and compared using the thermal behavior model, MLR model, and heat release rate model, respectively. It has been found that the forming process can significantly affect the fire properties of carbon/epoxy laminate composites. More specifically, the carbon/epoxy laminate composites formed using autoclave forming processes have more combustion resistance and thus have improved fire properties.

Thermal Analysis of Healthy and Ecological Friendly Flame Retardants for Textiles

Flame Retardants (FR) are a group of anthropogenic environmental contaminants used at a relatively high concentration in many applications. Currently, the largest marked group of FRs is halogenated FR, and many of them are considered toxic, persistent and bio accumulative. Non-halogenated alternatives are a possible solution for the problem, but there is a lack of knowledge concerning environmental impact, health risks during the production process and final use. The main objective of the LIFE-FLAREX project that supports this work, is the mitigation of the environmental and human health impact of flame retardants used in textiles, looking for new efficient more ecological and healthy alternatives, able to replace the most common FR’s that include toxic compounds like halogens, formaldehyde and antimony. The aim of this work is to determine the effect of conventional and ecological flame retardants on cotton and polyester fabrics by the application of differential scanning calorimetry DSC and thermogravimetric analysis TGA. Results have been compared with those given by the best FR applied to cotton/polyester blended fabric. The application of DSC up to 550°Cand TGA up to 600°C in N2 and O2 atmospheres give results that are in accordance with those yielded by the micro-scale combustion calorimeter. Onset temperatures of decomposition, steps of loss of mass by temperature and final residues, enable to evaluate the thermal efficiency of the different flame retardants. Results have been compared with those given by the application of ammonium polyphosphate and guanidine phosphate on cotton/polyester 50/50 blend.
 Keywords: Thermal Analysis, Flame retardant, Cotton, Polyester

Potential sustainable biomaterials derived from cover crops

Plant-derived biopolymers are renewable and readily available, thus making viable alternatives to synthetic polymers. The present study examined properties of biopolymers from cover crops such as rye, oat, clover, vetch, and barley, which were grown organically in a greenhouse. The yields of cellulose, hemicellulose, and lignin of the cover crops were calculated based on the dry weight. Structural variations and thermal properties of the isolated cellulose were characterized and compared with commercial cellulose using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and Thermogravimetric analysis (TGA). The average yield percentages of cellulose, hemicellulose, and lignin were 19 to 27%, 9 to 25%, and 1.42 to 4.86%, respectively. The FTIR and Raman spectral analysis indicated that the isolated cellulose had similar peaks and patterns to commercial cellulose, and confirmed the removal of non-cellulosic constituents. The onset decomposition temperature occurred at 270 °C in all samples. Interestingly, the maximum degradation temperature beyond 370 °C in cellulose was isolated from black oat, which was higher than commercial cellulose (350 °C). The findings of this research suggest that cellulose isolated from cover crops may be a benefit to the polymer industry in the development of bio-based materials such as biofuels, bio-composites, and biomedical devices.

Influence of thermal aging on decomposition behavior and kinetic mechanism of commercial proton exchange membranes

The aim of this work is to examine the pyrolysis and thermal properties of new and aged membranes. The results showed that the physical/chemical properties of membranes were changed after thermal aging. The onset decomposition temperature of the aged membrane was higher than that of the new one, whereas the maximum mass loss rate was reversed. The predicted thermogravimetric data by the ANN model, coincided well with the experimental data for both new and aged membranes. The average activation energy of the new membrane estimated by isoconversional methods was relatively higher than that of the aged one. A two-stage reaction modeling was employed to describe the degradation of new and aged membranes. The reaction mechanism of each stage was determined by the generalized master-plots method. The significant difference in reaction model between new and aged membranes was observed. Besides, the aged membrane released pyrolysis products later and less but faster than the new one. The burning results indicated that the aged membrane exhibited lower flammability and less heat release compared with the new one. The variation of pyrolysis and thermal behaviors between new and aged membranes was due to the changes of chemical component, molecular structure, and composition proportion.

A polymer blend from Gum Arabic and Sodium Alginate - preparation and characterization

An environmental friendly biopolymer blend has been fabricated with Gum Arabic (GA) and Sodium Alginate (SA). Three compositions of GA and SA blends coded GASA1 (GA:SA at 1:1), GASA2 (GA:SA at 2:1) and GASA3 (GA:SA at 1:2) has been synthesized. The two polymer phases form completely miscible, thermally stable amorphous multicomponent system which can be used as thermally stable polymeric material in electronic devices. The blends of GA and SA is casted to obtain thin films. Fourier Transform Infrared spectra (FTIR) confirms the formation of blend. The structural analysis and morphology of the synthesized blends has been studied with X- ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. XRD analysis shows that GA has amorphous and SA has semi crystalline nature. The diffraction pattern of the blends indicates that the semi crystalline nature of SA has been disturbed and an amorphous nature is obtained for the blend. SA has a spherical bead like structure and GA forms aggregates of high irregularity in the SEM image. Complete miscibility of the two polymers are seen in the SEM micrograph of the blends. Thermogravimetric-differential thermal analysis (TG-DTA) and differential thermal analysis (DSC) have been performed to study the thermal behavior of the prepared blends. From the TG-DTA analysis, higher onset decomposition temperature is reported for GASA2 which is 8% more than that for pure SA. The exothermic behavior of the blend has been discussed in details.

Insight on the effect of a piperonylic acid derivative on the crystallization process, melting behavior, thermal stability, optical and mechanical properties of poly(l-lactic acid)

Abstract A new piperonylic acid derivative (BPASD) was synthesized and evaluated as an organic nucleating agent for poly(l-lactic acid) (PLLA) via melt-crystallization; the other behaviors including cold-crystallization, melting process after crystallization, thermal stability in air atmosphere, and optical and mechanical properties of PLLA/BPASD samples were also investigated. The results of the melt-crystallization investigation showed that, in comparison to virgin PLLA, the BPASD could induce PLLA to crystallize in higher temperature region or at a faster cooling rate, suggesting that the BPASD as a heterogeneous nucleating agent could promote the crystallization of PLLA, but the melt-crystallization depended on the cooling rate, BPASD concentration, and the final melting temperature. With increasing of BPASD concentration, a shift to the lower temperature of cold-crystallization peak and decrease of crystallization enthalpy indicated that BPASD had an inhibition for the cold-crystallization of PLLA to some extent. The heating rate, crystallization temperature, the BPASD, and its concentration were critical factors to the melting process, and double-melting peaks appeared in heating were assigned to melting–recrystallization. Thermal decomposition behavior revealed that the addition of BPASD reduced the thermal stability of PLLA, but the interaction of PLLA and BPASD could prevent the decrease of the onset decomposition temperature. Further, the BPASD also decreased the light transmittance and elongation at the break of PLLA, but the tensile modulus and tensile strength of PLLA were enhanced.

Термическая стабильность полиуретанового покрытия, полученного с использованием дифенилолпропана

Thermal stability of polyurethane varnish coating prepared by using diphenylolpropane, polyetherpolyol and polyisocyanate with an equimolar ratio of isocyanate and hydroxyl groups was assessed in the air. The polyurethane weight loss thermogram shows three temperature regions: I – (217-275)°С, II – (275-380)°С, and III – above 380°С. For interpreting thermogram of the polyurethane under study the model substances simulating the urethane groups of a polymer were synthesized. The substance containing the urethane group formed by phenolic hydroxyl of diphenylolpropane was shown to demonstrate relatively low thermal stability and gets broken down into isocyanate and bisphenol. Decomposition of the substance containing the urethane group formed by alcoholic hydroxyl occurs at the higher temperature. The data obtained allow interpreting the occurrence of thermal decomposition step I in TGA curve by structural changes in the blocks formed by diphenylolpropane and polyisocyanate being the least stable when exposed to elevated temperatures. The next step can be attributed to decomposition of more thermostable urethane groups formed by functional groups of oligooxypropylenetriol and polyisocyanate. Transition to the step III accompanied by severe sample weight loss due to decomposition of urethane groups is explained by thermal oxidation of oligoether units of polymer. Based on the data obtained the conclusion was made that the presence of urethane groups formed by phenolic hydroxyl of diphenylolpropane in polymer structure results in the decreased thermooxidative decomposition onset temperature of polymer. At the same time, a deceleration of thermooxidative processes due to the stabilizing effect of diphenylolpropane released at the beginning of thermal decomposition of polyurethane is observed in a high-temperature region. The proposed polyurethane coating is inferior to commercial counterparts in thermal decomposition onset temperature but superior to them in the temperature corresponding to a 50% polymer weight loss.

Structural, thermal and optical characteristics of laser-exposed Pd/PVA nanocomposite

Nanocomposite of polyvinyl alcohol (PVA) and nanosize palladium (Pd) were fabricated by ex situ casting technique. The fabricated Pd/PVA nanocomposite film has been exposed to infrared pulsated laser with fluences in the range 2–20 J/cm2. The effect of the laser radiation on the structural, thermal and optical properties of Pd/PVA has been investigated using XRD, TGA and UV–Vis spectroscopy. Exposure of IR laser radiation raises the refractive index from 1.84 to 3.38 at 700 nm which confirms the predominance of crosslinking process in the Pd/PVA nanocomposite. Furthermore, the reduction in the optical energy gap from 1.87 to 1.72 eV could be attributed to the increase in the structural disorder resulting from the coordination reaction between OH of PVA and Pd nanoparticles. The attained results reveal that the IR laser radiation enhances the dispersion of Pd nanoparticles in the PVA matrix resulting in more compact structure of Pd/PVA nanocomposite. Consequently, the onset temperature of decomposition increased upon laser irradiation. Commission Internationale de E’Claire (CIE units x, y and z) methodology was employed to describe the color of the studied samples. The color difference between the exposed nanocomposite films and the non-exposed one was raised from 5.63 to 12.01 as the laser fluence increases up to 20 J/cm2. Thus, the present study suggests that the IR laser radiation affects the microstructure of the Pd/PVA nanocomposite which in turn assists in tailoring the thermal and optical properties of such nanocomposite for usage in optoelectronics applications.

Synthesis and characterization of renewable polyesters based on vanillic acid

AbstractVanillic acid, potentially derived from biosourced feedstocks, was used as starting material in the synthesis of novel polyesters. A diester obtained by esterification and etherification of vanillic acid served as first monomer, in combination with resorcinol bis(2‐hydroxyethyl) ether, hydroquinone bis(2‐hydroxyethyl) ether, or aliphatic diols with different carbon chain lengths as second monomers, and antimony trioxide as catalyst to synthesize a series of polyesters by melt polymerization. The materials obtained had polystyrene‐equivalent M n = 10,000–19,500 g/mol and M w = 19,300–39,500 g/mol. Thermal analysis yielded melting temperatures of 76–114°C and onset decomposition temperatures T5% = 321–360°C. Dynamic mechanical and tensile testing confirmed that polyesters derived from vanillic acid have properties superior to poly(ethylene terephthalate) (PET). Aqueous degradation experiments with bulk polyester samples at different pH over 16 weeks led to intrinsic viscosity decreases of 9–23% under neutral conditions (pH 7), 10–26% under acidic conditions (pH 3), and 7–19% under alkaline conditions (pH 12). The results obtained show that the good thermal stability and degradability of vanillic acid‐based polyesters, and the tunability of the properties of these materials through selection of the diol monomer used in their synthesis, make them excellent biosourced replacements for commercial polyesters such as PET.

New nitrogen-rich flame retardant based on conductive poly(aniline-co-melamine)

In the present work, a new copolymer was synthesized using aniline and melamine as a comonomer in order to increase the content of nitrogen in the final copolymer. The copolymer was synthesized via chemical oxidative polymerization of aniline and melamine, at different ratios, in the presence of ammonium peroxydisulfate (APS) as an oxidant. The obtained copolymers were characterized by Fourier-Transform Infrared spectroscopy (FTIR), Ultraviolet-visible (UV–Vis) spectroscopy, and Energy-dispersive X-ray (EDX). The solubility of the prepared copolymers was tested in various common organic solvents and the results showed that their solubility was better than polyaniline (PANI) in polar aprotic solvents. The elemental analysis revealed high content of nitrogen, around 72 wt% in one copolymer, against 34.6 wt% in the case of polyaniline homopolymer. The average conductivity of the PANI was 1.02 × 10−1 S/cm while it was between 6.1 × 10−4 S/cm and 2.9 × 10−2 S/cm for copolymers. Thermal degradation and flammability were investigated using Thermogravimetric analysis (TGA) and Pyrolysis Combustion Flow Calorimeter (PCFC), respectively. TGA results showed that the onset temperature of decomposition was significantly increased for all copolymers in respect to polyaniline. Moreover, PCFC tests revealed very low flammability character of the synthesized copolymers demonstrated by the Total Heat Release (THR) between 3 and 5 kJ/g. The elemental analysis of the remained char residue at the end of TGA showed that even at 900 °C, the high amount of nitrogen remained in the condensed phase for two copolymers.

Modified PLLA: effect of BPADD on properties

Poly(l-lactic acid) (PLLA) modified by a new organic nucleating agent, N,N′-dodecanedioic bis(piperonylic acid) dihydrazide (BPADD), was fabricated, and its crystallization, melting behavior, thermal stability, fluidity and mechanical properties were investigated. The melt-crystallization behavior proved that BPADD could bring about a fast nucleation rate to promote the crystallization of PLLA; 2 wt% BPADD exhibited the best crystallization accelerating effect due to having the highest crystallization onset temperature and the highest melt-crystallization temperature. However, PLLA/3% BPADD had the largest melt-crystallization enthalpy. In addition, the frontier orbital energy indicated that the nucleation effect of BPADD on PLLA might be attributed to intermolecular interaction. The melt crystallization also depended on two critical factors, the cooling rate and final melting temperature. An increase in BPADD content led to greater inhibition of crystal growth during cold crystallization. The differences in the melting behavior of PLLA/BPADD samples reflected the previous crystallization process, the heating rate and BPADD content. BPADD was harmful to maintaining the thermal stability of PLLA; however, the intermolecular interaction could prevent the decomposition onset temperature from continuously decreasing. The usage of BPADD resulted in better fluidity and higher tensile strength; the tensile modulus and elongation at break were associated with BPADD content.