Final Melting Temperature Research Articles

The Nucleated Poly(L-lactic acid): The Role of a Phenylacetic Hydrazide Derivative

The melt-crystallization, cold-crystallization, melting behaviors, thermal stability, and optical properties of poly(L-lactic acid) (PLLA) nucleated by a phenylacetic hydrazide derivative (DAPH) were investigated. The melt-crystallization confirmed DAPH’s heterogeneous nucleation role in improving PLLA’s poor crystallization capability, concurrently DAPH loading, cooling rate and final melting temperature were three key factors affecting PLLA’s melt-crystallization behaviors. The results from cold-crystallization indicated that the addition of DAPH could accelerate PLLA’s cold-crystallization via cold-crystallization peak’s shift toward the lower temperature side as DAPH loading increased. Through analysis of PLLA/DAPH’s multiple melting behaviors after melt-crystallization, it was found that DAPH loading, the previous melt-crystallization and heating rate determined PLLA/DAPH’s melting processes after melt-crystallization; and PLLA/DAPH’s melting processes after isothermal crystallization depended on the previous crystallization temperature. A drop in thermal decomposition temperature for 5 wt.% mass loss suggested that pure PLLA has better thermal stability compared with PLLA/DAPH. Additionally, the introduction of DAPH could not improve PLLA’s transparency, in contrast, the haze of PLLA was increased greatly owing to the existence of DAPH.

The Performance Investigation of PLLA/PPAPH: The Influence of PPAPH as Heterogeneous Crystal Nuclei

To overcome PLLA�s poor crystallization capability, using nucleating agent as crystallization improvement strategy was performed in this study. PPAPH as PLLA�s an organic nucleating agent was firstly synthesized, and then PLLA was blended with different PPAPH loading through melting blend method, the resulting influences of PPAPH on PLLA�s performances were investigated using the relevant testing instruments. Melt-crystallization revealed that PPAPH played important role in promoting PLLA�s crystallization through providing effective sites of heterogeneous nucleation, and effect of PPAPH loading on PLLA�s melt-crystallization was very poor, indicating that low PPAPH loading could cause PLLA to possess powerful crystallization capacity. In addition, the relative low final melting temperature was beneficial for PLLA/PPAPH�s crystallization. However, an increase of cooling rate during cooling stage weakened PLLA/PPAPH�s crystallization capacity. PLLA/PPAPH�s cold-crystallization suggested that PPAPH had an inhibition effect on cold-crystallization process to some extent. Melting behaviors depended on heating rate and previous crystallization including melt-crystallization at various cooling rates and isothermal crystallization at various crystallization temperatures. PPAPH enhanced PLLA�s fluidity, tensile modulus and tensile strength. Unfortunately, PLLA�s transmittance was seriously weakened as PPAPH loading increased, as well as the elongation at break continuously decreased.

Effects of NANH as a nucleation agent on the performance of PLLA

In this research, N,N′-bis(nicotinic) 1,4-naphthalenedicarboxylic acid dihydrazide (NANH) as a new synthetic organic nucleating agent was employed to overcome the slow crystallization rate of poly(L-lactide) (PLLA). Melt crystallization showed that the crystallization ability of PLLA was significantly enhanced by NANH, with NANH still being able to accelerate PLLA crystallization at a cooling rate of 50°C/min. Additionally, when the final melting temperature was 170°C, the onset melt-crystallization temperature and melt-crystallization peak temperature of PLLA/3% NANH were up to 160.0 and 155.1°C, respectively. Isothermal crystallization showed that the half-time of the overall crystallization of PLLA/3% NANH was dramatically reduced, from 71.9 min at 135°C for the virgin PLLA to the minimum value of 0.3 min. This advanced nucleation effect was speculated to be due to chemical nucleation through the theoretical analysis of frontier orbital energy. Melting behaviors under different conditions further confirmed the crystallization-accelerating effect of NANH for PLLA crystallization, and the melting processes were affected by the crystallization temperature and heating rate. Although NANH decreased the thermal decomposition temperature of PLLA in air, the thermal decomposition temperatures of all PLLA/NANH blends were higher than 330°C, which could meet daily usage requirements. Finally, the addition of NANH enhanced PLLA fluidity; however, light transmittance was seriously weakened.

Nucleating Agents to Enhance Poly(L-lactide) Crystallization and Melting Behavior of Modified Poly(L-lactide)

Melt processing poly(L-lactide) (PLLA) with a nucleating agent has been thought to be one of the most effective route to enhance PLLA s crystallization and heat resistance. In the current work, a newly-developed organic nucleating agent named N, N -bis(2-picolinyl) 1, 4-naphthalenedicarboxylic acid dihydrazide (NCAPH) was synthesized to investigate its effects on PLLA�s crystallization and melting behaviors. It is proved that NCAPH as an organic crystallization nucleating agent could provide large number of crystallization nucleation sites to improve PLLA�s crystallization, as observed from DSC and POM measurements. The result from melt-crystallization processes further showed that the final melting temperature and cooling rate were two important factors for affecting PLLA�s melt-crystallization behaviors in cooling, and the theoretical calculation result of frontier orbital energy indicated there existed probable intermolecular interaction between N-H of NCAPH and C=O of PLLA, which was proposed as nucleation mechanism of NCAPH for promoting PLLA�s crystallization. The melting behaviors of PLLA/NCAPH after non-isothermal crystallization or isothermal crystallization further confirmed the positive effects of NCAPH and NCAPH�s loading for the crystallization of PLLA, meantime, the melting behaviors depended on the heating rate, crystallization temperature, crystallization time, etc.

Fluid Charging and Paleo‐pressure Evolution in the Ledong Slope Zone of the Yinggehai Basin, South China Sea

AbstractLarge numbers of gas reservoirs have been discovered in overpressure basins. Fluid charging has a close relationship with paleo‐pressure evolution, affecting the migration of gas reservoirs. To study fluid charging and the related pressure system, we analyzed burial histories and fluid inclusion (PVTx) simulations and conducted basin modeling of the Ledong Slope Zone in the Yinggehai Basin as an example. On the basis of fluid‐inclusion assemblages (FIAs), homogenization temperature (Th), final melting temperature (Tm, ice) and Raman spectroscopy in fluid inclusions, there are three stages of fluid charging: during the first and second stage, methane‐dominated fluid was charged at 2.2–1.7 Ma and 1.7–0.9 Ma, respectively. In the third stage, CO2‐rich hydrothermal fluid was charged since 0.9 Ma. It could be concluded from the well‐logging data that the disequilibrium compaction in the Yinggehai Fm., along with the fluid expansion and clay diagenesis in the Huangliu and Meishan formations, resulted in the overpressure in the Ledong slope zone. The evolution of paleo‐pressure was affected by the sedimentation rate of the Yinggehai Fm., as well as the hydrocarbon generation rate. Additionally, the Ledong Slope Zone is less affected by diapir activity than the nearby diapir area. Based on fluid inclusions, paleo‐pressure, basin modeling and geological background, the gas migration history of the Ledong Slope Zone can be divided into four stages: in the first stage, excess pressure was formed around 5 Ma; from 2.2 to 1.7 Ma, there was a reduction in the charging of hydrocarbon fluid and steadily increasing excess pressure; during the 1.7–0.9 Ma period a large amount of hydrocarbon was generated, excess pressure increasing significantly and hydraulic fractures forming in mudstones, With gas reservoirs developing in structural highs; since 0.9 Ma, CO2‐rich hydrothermal fluid accumulated in reservoirs adjacent to faults and the pressure coefficient remained stable. The research results are helpful in the study of fluid migration and accumulation mechanisms in overpressure basins.

The Application of N, N -bis(Isonicotinic Acid) 1, 4-Naphthalenedicarboxylic Acid Dihydrazide in Biodegradable Poly(L-lactide): Crystalline Nucleation, Melting Behavior, Thermal Stability and Mechanical Properties

Improving the crystallization performance of poly(L-lactide) (PLLA) is necessary to adapt for various applications. In the current work, N, N -bis(isonicotinic acid) 1, 4-naphthalenedicarboxylic acid dihydrazide (NAIAH) was synthesized to be firstly aimed at promoting the crystallization of PLLA, and the NAIAH-nucleated PLLA materials were prepared using PLLA as a matrix material and NAIAH as a nucleating agent, and the crystalline nucleation, melting behavior, thermal decomposition and mechanical properties of PLLA/NAIAH samples were investigated by the relevant testing instruments. The results from the non-isothermal melt-crystallization from the melt of 190oC indicated that the NAIHA could significantly accelerate PLLA�s crystallization, and played an efficient heterogeneous nucleation in PLLA�s crystallization. The effect of different final melting temperatures on PLLA�s melt-crystallization behavior showed that a relatively low final melting temperature was beneficial for the crystallization of PLLA, and the 170oC was the optimum final melting temperature in this study. An increase of cooling rate could weaken PLLA/NAIAH�s crystallization ability, but the NAIAH was still able to promote PLLA�s crystallization upon the fast cooling at 50oC/min, showing a powerful crystallization accelerating effect of NAIAH. PLLA/NAIAH�s melting behaviors after different crystallization conditions were affected by heating rate and crystallization temperature, and the double melting peaks appeared in melting DSC curves were assigned to melting-recrystallization. Thermal decomposition processes in air showed that the NAIAH decreased PLLA�s thermal stability, but the interaction of PLLA with NAIAH had an inhibition for a drop in onset decomposition temperature. Additionally, the introduction of NAIAH dramatically reduced PLLA�s tensile modulus and elongation at break.

Physical-chemical properties of InSb+Mg3Sb2 eutectic systems: synthesis, characterization, and applications

InSb+Mg3Sb2 systems are synthesized by the vertical Bridgman–Stockbarger method. InSb and Mg3Sb2, a form of lamellar eutectic. XRD analysis and microstructural study of InSb+Mg3Sb2 composites show that Mg3Sb2 lamellar are uniformly distributed in the InSb matrices. The initial and final melting temperatures for InSb+Mg3Sb2 eutectic alloys are 770K and 772K, respectively.

Machine learning discovery of a new cobalt free multi-principal-element alloy with excellent mechanical properties

In the present study, the machine learning (ML) method was utilized to construct a composition–structure–property model incorporating physical features. To enhance the predictive accuracy, the volume fraction of the two phase microstructure was merged into the dataset serving as the physical constraint for the input variables. The physical features, the chemical composition and the temperature difference between the initial and final melting temperatures were selected as the input and output variables, respectively. To deal with the small sample data, the generalized regression neural network (GRNN) was selected and applied with optimization algorithms e.g., fruit fly optimization algorithm (FOA) and particle swarm optimization (PSO). The performance of the GRNN, FOA-GRNN and PSO-GRNN models were compared. As a result, the PSO-GRNN model was the most promising model and could be utilized to search for new multi-principal elements alloy (MPEAs) with targeted properties. Based on the ML results, a novel Fe2.5Ni2.5CrAl MPEA was designed and synthesized for experimental characterization. The DSC analysis shows that the developed alloy possesses narrower melting range and the predicted value is in excellent agreement with experiments with a relative error below 10%. The designed alloy possesses a typical dual-phase structure (FCC+BCC/B2) and exhibits exceptional mechanical properties with superior plasticity at the cast condition. This property improvement is due to solid solution strengthening and nanoparticles strengthening effects. Our proposed alloy can be a promising choice for selected high performance applications.

Melt and nucleation reinforcement for stereocomplex crystallites in poly(ʟ-lactide)/lignin-grafted-poly(ᴅ-lactide) blend

Lignin-grafted-poly (ᴅ-lactide) (LGPD) with two different poly (ᴅ-lactide) (PDLA) block lengths (1100 and 2000 Da), denoted as LGPDL and LGPDH respectively, were synthesized by ring opening polymerization using dodecylated lignin as initiator. They were then blended with poly(ʟ-lactide) (PLLA) to improve its crystallization, mechanical properties and UV-absorbance properties. It was found that stereocomplex (SC) crystallites could be formed in both PLLA/LGPD blends, and the crystallization rate of PLLA/LGPDH was faster than that of PLLA/LGPDL because of the longer PDLA block length. Both in the non-isothermal and isothermal crystallization process, the crystallization of PLLA in the PLLA/LGPDH blend was the fastest when the ratio of LGPDH was 3%. SC crystallites in the PLLA/LGPDH blends also showed broader melting ranges and higher final melting temperatures comparing to the blends of PLLA and 4-armed PDLA (4a-PDLA), whose number of PDLA arms and molecular weight was similar to LGPDH. These results proved that the lignin structure grafted by the PDLA arms could affect the state of SC crystallites and their acceleration effect on the crystallization of PLLA in the blend. The degradation behavior showed that the degradation rate of the LGPDH-5% blend in the final stage of degradation (about 24 h) was the slowest comparing to other blends. Besides, the PLLA/LGPD blends had better tensile strength and UV-absorbance properties than neat PLLA.

Influence of metallurgical slag additives on proppants synthesis processes based on drilling muds

The slags formed during the smelting of ferrous alloys consist of more than 75% oxides of calcium, iron and silicon that predetermines broad prospects for their use as an alternative to natural raw materials. Considering the significant amount of alkaline earth oxides (calcium and magnesium) in the metallurgical slag, it seems promising to use it as a fluxing additive in highalumina aluminosilicate materials, one of which is proppants – granular aluminosilicate materials designed to enhance oil production by hydraulic fracturing. The aim of this work is to study the effect of metallurgical slag additives on the processes of proppant synthesis based on drill slurry. The composition of the initial drill slurry from the Morozovskoye deposit and the fluxing additive of metallurgical slag of JCS “TagMet” was studied. Based on the composition of the metallurgical slag, an assumption was made about its fluxing activity in the synthesis of silicate materials, which is due to a large amount of alkaline earth metal oxides, a low intensity of the crystalline phase and the presence of preliminary heat treatment. Five compositions of raw mixtures for the production of proppants were developed with the addition of two types of fluxing additives: metallurgical slag and sodium hydroxide. Qualitative (texture and color) and quantitative (density and sintering coefficient) parameters of the degree of sintering and melting of mixtures were determined. It was shown that both additives have a fluxing effect on drill slurry. It was found that the introduction of metallurgical slag leads to a change in texture to a more sintered one, as well as an increase in density and sintering coefficient. The introduction of sodium hydroxide has a more active effect on drill slurry, which leads to glass formation of the surface and further melting of the material. Physicochemical processes under the fluxing effect of the selected additives were considered, which is explained by the formation of more low-melting silicates, which reduce the final melting temperature of the mixture. The work was performed at YuRGPU (NPI) with the financial support of the Russian Science Foundation under the Agreement No. 20-79-10142 “Development of an effective technology for synthesis of aluminosilicate proppants using waste of drilling oil and gas wells of the Southern Federal District” (head – A. A. Tretyak).

Geological and geochemical characterization of the Nanlia and Makorongo gold prospects, Mozambique Belt, northeastern Mozambique

Northern Mozambique hosts numerous occurrences of gold mineralization in metamorphic terranes, which are little known because of the insufficient studies. In this work, we describe the main geological and geochemical characteristics of the Nanlia and Makorongo gold prospects located in the Namuno district, northeastern Mozambique. We report the mode of occurrence of gold, petrography and mineralogy of the host rocks and ores, fluid inclusion characteristics and stable isotope data, to understand the genesis of gold mineralization in the study area. The gold mineralization in the Nanlia and Makorongo prospects is hosted by the Neoproterozoic Xixano Metamorphic Complex in the Mozambique Belt, which is composed of mafic granulite, amphibolite, paragneiss and marble. The host rock amphibolite consists mainly of amphibole, plagioclase, biotite and minor quartz, titanite and sulfides. The gold mineralization is associated with E-W to ENE-WSW trending quartz veins, oriented parallel to low angle to the foliation of the host rock amphibolite. The ore mineralogy consists of pyrite, pyrrhotite, chalcopyrite, magnetite, galena and sphalerite, with minor tellurides, xilingolite, electrum and native gold. Mineralized quartz veins in the Nanlia and Makorongo prospects host two types of fluid inclusions which locally coexist in the same assemblage: type 1, one-phase CO2 inclusions with final melting temperature between −58 and −52 °C; and type 2, two-phase H2O + NaCl (±CO2 ± N2 ± CH4) inclusions with homogenization temperature ranging from 246 to 370 °C and 239 to 382 °C in the Nanlia and Makorongo prospects, respectively, and salinity of 12–21 wt% NaCl eq. Pressure and temperature (P-T) conditions of ore-formation were estimated from fluid inclusions and sphalerite geobarometry at 420–620 °C and 160–280 MPa, and 330–440 °C and 150–200 MPa in the Nanlia and Makorongo prospects, respectively. The Nanlia and Makorongo gold prospects are classified as orogenic-type gold deposits. We suggest that gold mineralization was caused by an aqueous-carbonic fluid with low-moderate salinity originated by devolatilization during prograde metamorphism of underlying rocks. The gold mineralization post-dates the peak of metamorphism of the host rocks, thus formed during the retrograde metamorphism of the host rocks. The precipitation of gold in the Nanlia and Makorongo prospects was caused by fluid phase separation induced by pressure drop as the mineralizing fluid migrated to shallower depths.

Physical Properties of Biodegradable Poly(L-lactide) Induced by N, N -Bis(Benzoyl) 1, 3-Cyclohexanedicarboxylic Acid Dihydrazide as Crystallinity Additive

This work is aimed at synthesizing an organic compound N, N -bis(benzoyl) 1,3-cyclohexane-dicarboxylic acid dihydrazide (CABH) to focus on its effect on the non-isothermal crystallization of poly(L-lactide) (PLLA), meanwhile the melting behavior, thermal decomposition process and optical property of PLLA/CABH samples in different CABH concentrations were also investigated. It was found that CABH acted as efficient heterogeneous nucleating agent for inducing PLLA�s crystallization through comparative analysis of melt-crystallization process of the virgin PLLA with PLLA/CABH samples, and a high amount of CABH played a much more significant role in promoting PLLA�s crystallization. Additionally, the melt-crystallization processes also showed that both the cooling rate and the final melting temperature affected the crystallization behavior of PLLA, an increase of cooling rate could weaken the crystallization ability of PLLA/CABH samples, and the final melting temperature of 180�C made PLLA/CABH exhibit the best crystallization ability. For the cold-crystallization process, the cold-crystallization peak became flatter and shifted toward the lower temperature with increasing of CABH concentration, but an increase of heating rate could prevent the cold-crystallization peak from moving to low temperature because of the thermal inertia. The melting behaviors of PLLA/CABH depended on the previous crystallization and heating rate in heating, and the difference in melting behavior of PLLA/CABH samples effectively reflected the nucleation role of CABH, as well as the double melting peaks behavior of PLLA/CABH was thought to due to the melting-recrystallization. The introduction of CABH led to a drop in light transmittance, moreover, this negative effect were more obvious with an increase of CABH loading. In contrast, the fluidity of PLLA was significantly enhanced due to the existence of CABH.

Thermal and mechanical properties of poly(L-lactic acid) nucleated with N,N’-bis(phenyl) 1,4-naphthalenedicarboxylic acid dihydrazide

The modified poly(L-lactic acid) (PLLA) with different contents (0.5−3 wt %) of N,N’-bis(phenyl) 1,4-naphthalenedicarboxylic acid dihydrazide (NAPH) were prepared to evaluate effects of NAPH on melt-crystallization behavior (DSC), thermal degradation (TGA) and mechanical properties of PLLA. The melt-crystallization results demonstrated that NAPH as a heterogeneous organic nucleating agent enhanced crystallization ability of PLLA in cooling, and PLLA/1%NAPH had the best crystallization ability because of the highest onset crystallization temperature and the sharpest melt-crystallization peak. However, melt-crystallization behavior also depended on the cooling rate and final melting temperature, overall, a relative slow cooling rate and low final melting temperature were beneficial for crystallization of PLLA. The cold-crystallization results indicated that NAPH had an inhibition for cold-crystallization process of PLLA, and the cold-crystallization peak shifted towards lower temperature and became wider with an increase of NAPH concentration. The different melting behaviors ofPLLA/NAPH after melt-crystallization and isothermal-crystallization efficiently reflected the accelerating role of NAPH for PLLA crystallization; the double melting peaks formed in heating were thought to result from melting-recrystallization, as well as that a higher crystallization temperature could cause melting peak to appear in higher temperature regions and possess larger melting enthalpy. A comparative analysis on thermal degradation in air illustrated that the addition of NAPH accelerated decomposition of PLLA, but a decrease of onset decomposition temperature was inhibited by the probable interaction of PLLA with NAPH. Moreover, the tensile test showed that NAPH decreased tensile modulus and elongation at break of PLLA, whereas PLLA with low concentration of NAPH had higher tensile strength than pure PLLA.

Effect of 1,4-Naphthalenedicarboxylic Acid Derivative on Crystallization and Performances of Poly(L-lactide)

In this work, biodegradable Poly(L-lactide) (PLLA) was modified through adding a new organic additive N, N -bis(benzoyl) 1, 4-naphthalenedicarboxylic acid dihydrazide (NABH). A comparison on crystallization of the pure PLLA and PLLA/NABH revealed that the NABH as effective heterogeneous nucleation sites enhanced PLLA𠏋 crystallization, and an increase of NABH loading was able to further accelerate crystallization rate of PLLA; whereas a faster cooling rate was not conducive to PLLA𠏋 crystallization, but the appearance of obvious crystallization peak upon cooling at 30şC/min confirmed the advanced enhancing role of NABH for PLLA crystallization again. The investigation on influence of the final melting temperature on the crystallization behavior of PLLA showed that the 170 şC was optimum final melting temperature for enhancing crystallization, even the onset crystallization temperature of PLLA/NABH were higher than 150şC. The melting processes of PLLA/NABH after different crystallization not only could reflect the previous crystallization, but also depended on crystallization temperature and heating rate. Thermal decomposition results showed that the existence of NABH slightly weakened thermal stability of PLLA, and the maximum difference in onset thermal decomposition temperature was only 9.4şC comparing with the pure PLLA. However, the presence of NABH in PLLA matrix seriously weakened optical property.

Crystallization and properties of nucleated poly(l-lactic acid): Effect of cyclopentanecarboxylic acid derivative as a new nucleating agent

In this study, the potential effects of N, N’-dodecanedioic bis(cyclopentanecarboxylic acid) dihydrazide (BCADD) as a new additive in poly(L-lactic acid) (PLLA) was estimated. The comparative study on the melt-crystallization showed that the BCADD as heterogeneous nuclei facilitated crystallization of PLLA in cooling, which indicated by the obvious crystallization exotherms and sharp melt-crystallization peak. Unfortunately, with increasing of BCADD from 0.5 wt% to 3 wt%, it is unexpected that the melt-crystallization peak of the BCADD-nucleated PLLA shifted toward the lower temperature and became flatter, evidencing the importance of BCADD loading for PLLA’s crystallization. Additionally, the cooling rate and the final melting temperature were also proved to be important influence factors during PLLA’s melt-crystallization process, but in contrast with the effect of the final melting temperature on the melt-crystallization, a higher cooling rate could more seriously weaken crystallization ability of the BCADD-nucleated PLLA. The chemical nucleation mechanism was proposed to explain the promoting effect of BCADD on the crystallization of PLLA via the analysis of frontier orbital energy. The melting behaviors after crystallization further confirmed the crystallization accelerating role of BCADD, and the melting behaviors were affected by the heating rate, crystallization temperature and BCADD loading. Although the onset thermal decomposition of the BCADD-nucleated PLLA occurred at lower temperature comparing with the pure PLLA, the intermolecular interaction of PLLA with BCADD attempted to prevent the decrease of thermal stability. Overall, the addition of BCADD resulted in the complicated effect on the tensile modulus and tensile strength of PLLA, but the elongation at break continuously decreased when increasing BCADD loading.

Petrology and geochemistry of South Mid-Atlantic Ridge (19°S) lava flows: Implications for magmatic processes and possible plume-ridge interactions

The South Mid-Atlantic Ridge (SMAR) 19°S segment, approximately located along the line of Saint Helena volcanic chain (created by Saint Helena mantle plume), is an ideal place to investigate the issue whether the ridge-hotpot interaction process affected the whole MAR. In this study, we present major and trace elemental compositions and Sr-Nd-Pb isotopic ratios of twenty fresh lava samples concentrated in a relatively small area in the SMAR 19°S segment. Major oxides compositions show that all samples are tholeiite. Low contents of compatible trace elements (e.g., Ni ​= ​239–594 ​ppm and Cr ​= ​456–1010 ​ppm) and low Fe/Mn (54–67) and Ce/Yb (0.65–1.5) ratios of these lavas show that their parental magmas are partially melted by a spinel lherzolite mantle source. Using software PRIMELT3, this study obtained mantle potential temperatures (Tp) beneath the segment of 1321–1348 ​°C, which is lower relative to those ridges influenced by mantle plumes. The asthenospheric mantle beneath the SMAR 19°S segment starts melting at a depth of ~63 ​km and ceases melting at ~43 ​km with a final melting temperature of ~1265 ​°C. The extent of partial melting is up to 16%–17.6% with an average adiabatic decompression value of 2.6%/kbar. The correlations of major oxides (CaO/Al2O3) and trace elements (Cr, Co, V) with MgO and Zr show that the parental magma experienced olivine and plagioclase fractional crystallization during its ascent to the surface.87Sr/86Sr (0.702398–0.702996), 143Nd/144Nd (0.513017–0.513177) and 206Pb/204Pb (18.444–19.477) ratios of these lavas indicate the mantle source beneath the SMAR 19°S segment is composed of a three-component mixture of depleted MORB mantle, PREMA mantle, and HIMU mantle materials. The simple, binary mixing results among components from plume-free SMAR MORB, Saint Helena plume and Tristan plume show that asthenospheric mantle beneath the SMAR 19°S segment may be polluted by both Saint Helena and Tristan plume enriched materials. The abovementioned mantle potential temperatures, together with the low Saint Helena (<10%) and Tristan (<5%) components remaining in the asthenospheric mantle at present, show that the physically ridge-hotspot interactions at SMAR 19°S segment may have ceased. However, the trace element and Sr-Nd-Pb isotopically binary mixing calculation results imply that these lavas tapped some enriched pockets left when Saint Helena and/or Tristan plume were once on the SMAR during earlier Atlantic rifted history.

Non-isothermal Crystallization, Melting Behavior, Thermal Decomposition, Fluidity and Mechanical Properties of Melt Processed Poly(L-lactic acid) Nucleated by N,N'-Adipic Bis(piperonylic acid) Dihydrazide

Enhancing on the crystallization ability of poly(L-lactic acid) (PLLA) during practical processing is one of the most effective way to overcome the poor heat resistance. In this work, N,N '-adipic bis(piperonylic acid)dihydrazide (PAAH) was synthesized to be firstly used as a heterogeneous nucleating agent to evaluate its influence on the performances, including the crystallization, melting behavior, thermal stability, fluidity and mechanical property, of PLLA. The nucleation effect of PAAH was determined via the melt-crystallization of PLLA with various PAAH concentrations from 0.5 to 3 wt % at different cooling rates, as well as the different final melting temperature Tf . The results revealed that the PAAH could significantly accelerate the crystallization of PLLA in cooling, and the melt-crystallization peak shifted toward the higher temperature with increasing of PAAH concentration, resulting from an increase of nucleation density in PLLA matrix. Additionally, both the cooling rate and Tf were two critical factors to crystallization, a higher cooling rate could weaken the crystallization ability of PLLA/PAAH, and the 200°C was the optimum melting process temperature. For cold-crystallization, PAAH had an inhibition for the cold-crystallization of PLLA, but the cold-crystallization peak moved toward the higher temperature with increasing of heating rate because of thermal inertia. There existed only a single melting peak after melt-crystallization at cooling of 1°C, which further confirmed the advanced nucleation effect of PAAH, but the double-melting peaks appeared after isothermal crystallization at 110°C, which was attributed to the melt-recrystallization. The other measurements showed that, compared to the neat PLLA, the addition of PAAH decreased the thermal stability and tensile modulus of PLLA, but PLLA/PAAH samples had the better fluidity, the higher tensile strength and the longer elongation at break.

Thermal performances and optical property of poly(L-lactic acid) under the influence of N,N'-dodecanedioic bis(3-phenylpropionic acid) dihydrazide as a crys­tal­lization promoter

Poly(L-lactic acid) (PLLA) as an important biodegradable polymer suffers from slow crystallization rate and poor heat resistance. An organic compound N,N’-dodecanedioic bis(3-phenylpropionic acid) dihydrazide (BHADD) was synthesized to evaluate its general influences on the physical properties of PLLA. The melt-crystallization process indicated that BHADD could serve as a heterogeneous nucleating agent for improving the crystallization of PLLA, and PLLA/1%BHADD exhibited the sharpest melt-crystallization peak located at the highest temperature, as well as an increase of cooling rate weakened the crystallization ability of BHADD-nucleated PLLA. And the final melting temperature also displayed the significant effect on the crystallization process of PLLA. For the cold-crystallization process, both BHADD concentration and heating rate affected the cold-crystallization behavior of PLLA/BHADD, the increasing of BHADD concentration caused the cold-crystallization peak to shift to the lower temperature; in contrast, a higher heating rate during heating leaded to the peak’s shift toward the higher temperature because of the thermal inertia. The melting behavior of PLLA/BHADD depended on the crystallization temperatures and heating rates, and the double melting peaks were attributed to the melting-recrystallization. Thermal decomposition experiment showed all PLLA/BHADD samples as the pure PLLA only exhibited one thermal decomposition stage, but PLLA/BHADD had a lower thermal stability than the pure PLLA. Additionally, the addition of BHADD seriously decreased the light transmittance of PLLA.

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.

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.