Thermal Performances and Fluidity of Biodegradable Poly(L-lactic acid) Filled with N, N'-Oxalyl Bis(piperonylic acid) Dihydrazide as a Nucleating Agent

N, N'-oxalyl bis(piperonylic acid) dihydrazide (PAOD) was obtained through the amination of piperonylic acid chloride and its structure was characterized by Fourier transform infrared spectrometer and nuclear magnetic resonance. Melting blend technology was used to prepare the modified poly(L-lactic acid) (PLLA) containing the various loading PAOD as a new organic nucleating agent. The thermal performances including crystallization, melting behavior and thermal decomposition process, as well as the fluidity of PAOD-nucleated PLLA were investigated via a series of tests. The DSC results showed that, in comparison to DSC curve of the virgin PLLA, the DSC curves of all PLLA/PAOD appeared the sharp melt-crystallization peak, and a higher PAOD concentration caused the melt-crystallization to occur in the higher temperature region and reduced the negative effect of the high cooling rate on the melt-crystallization process. However, with increasing of PAOD concentration, the cold-crystallization enthalpy decreased from 24.4 J/g to 16.7 J/g. The melting peak after melt-crystallization depended on the heating rate and the PAOD concentration; and the double melting peaks appeared after isothermal crystallization in low temperature region was thought to be due to the melting-recrystallization. The addition of PAOD decreased the onset decomposition temperature of PLLA, but the onset decomposition temperature was determined by the PAOD concentration and the intermolecular interaction of PLLA and PAOD. Additionally, the PAOD could considerably improve the fluidity of PLLA.

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.

The effect of pumice powder on mechanical and thermal properties of polypropylene

Pumice stone (P), which is as a cheap material, can be a good candidate for filling material for polymers because of its high thermal resistance. Its effect on properties of polypropylene (PP) has not been studied in detail up to now. The mechanical, viscoelastic, thermal, morphological, crystallographic, and thermomechanical behaviors of PP filled with P powder were studied. The composites were produced by adding different weight fractions of P powder (0–40 wt%) into PP using a high-speed thermo kinetic mixer and compression molding. The highest tensile and flexural strength values, 26.5 and 46.4 MPa, respectively, were obtained when 10 wt% of P powder was filled into PP. Besides, the storage and loss modulus of PP was increased with the addition of P powder. The onset decomposition temperature of PP increased by 39°C with P powder loading into PP. The addition of P powder into PP led to a significant increase on the crystallinity of PP. It is interesting to report that thermal conductivity of PP was increased with increasing weight fraction of P powder.

Synthesis and characterization of the pentazolate anion cyclo-N5ˉ in (N5)6(H3O)3(NH4)4Cl

Pentazole (HN5), an unstable molecular ring comprising five nitrogen atoms, has been of great interest to researchers for the better part of a century. We report the synthesis and characterization of the pentazolate anion stabilized in a (N5)6(H3O)3(NH4)4Cl salt. The anion was generated by direct cleavage of the C–N bond in a multisubstituted arylpentazole using m-chloroperbenzoic acid and ferrous bisglycinate. The structure was confirmed by single-crystal x-ray diffraction analysis, which highlighted stabilization of the cyclo-N5ˉ ring by chloride, ammonium, and hydronium. Thermal analysis indicated the stability of the salt below 117°C on the basis of thermogravimetry-measured onset decomposition temperature.

Improved Dehydriding Properties of NaMgH3 Perovskite Hydride by Addition of Graphitic Carbon Nitride

NaMgH3 perovskite hydride and graphitic carbon nitride (g-C3N4) powder with multi-layer structure have been synthesized by high-energy ball-milling and heating-decomposition method respectively. In comparison with pristine NaMgH3 hydride, the as–milled NaMgH3+5wt.% g-C3N4 (NMH-5CN) composite presents better dehydriding kinetic properties and lower onset decomposition temperature. The onset decomposition temperature of NMH-5CN composite can be decreased about 87K, the hydrogen-desorbed amount is about 3.2 wt. % within 40min, and 1.4 wt. % within 10min at 638K, and the Kissinger analysis demonstrated that the activation energy (ΔE) of the first and second dehydrogenation step for NMH-5CN can be reduced about 40 kJ mol-1 and 22.4 kJ mol-1, respectively. The results suggest that g-C3N4 is an effective catalyst for the improvement of dehydriding properties of NaMgH3 perovskite hydride.

Characterization and Preparation of Polyamide 66/OV-POSS Nanocomposite Fibre

Poly hexamethylene adipamide (PA66) nanocomposite fibers were prepared by using PA66 and polyhedral oligomeric silsesquioxanc (POSS). Rheological behavior, mechanical and thermal properties were characterized. Rheological study showed that a small amount of POSS can improve the flowing property and reduce PA66 viscosity. The onset decomposition temperature was improved with the addition of POSS as indicated by TGA analysis. Nearly all the mechanical properties were found to be increased with the adding of POSS. However, it was seen that higher POSS loading would not improve fiber performance due to serious of agglomeration.

Influence of Zinc Oxide Contents on Mechanical, Rheological and Thermal Properties of Thermoplastic Natural Rubber

The influence of ZnO contents on properties of the natural rubber/polypropylene thermoplastic vulcanizates (NR/PP TPVs) is investigated. The NR/PP TPVs with ZnO obviously show improvement of mechanical, rheological and thermal properties comparing to the TPV without ZnO addition. The ZnO content does not much affect on mechanical and rheological properties of the TPVs. However, it strongly influences on thermal property especially decomposition temperatures at 5 and 50 %wt loss of polymer (Td5 and Td50) and onset decomposition temperature of rubber phase (Tronset).

The Structure and Properties of HDPE/EAA-Hydrotalcite Master Batch Nanocomposites

The High-density polyethylene (HDPE) / the ethylene acrylic acid (EAA) - layered double hydroxide (LDH) nanocomposites were prepared by melt blending with EAA)/ LDH master batch; and the structure and properties of this nanocomposite were studied. The results showed that the EAA acted as an effective compatibilizer for the nanocomposites can enhance the interfacial adhesion between LDH and HDPE obviously, promote the dispersion of LDH in the matrix, increase both the tensile strength and toughness of nanocomposites, and improve the thermal stability and delay the onset decomposition temperature of nanocomposites.

High Temperature Clay Filled Epoxy Composites

The primary objective of this study is to improve the thermal stability of clay and clay filled composite. An epoxy-clay composite has been prepared by dispersing 1-hexadecyl-3-(6-hydroxyhexyl)-2-methylimidazolium modified clay in an epoxy resin and cured with metaphenylene diamine (m-PDA) at 110.0 °C for 7 h and post cured at 140°C for 4 h. The thermal stability of the modified clay and clay filled epoxy composite was characterized via thermogravimetric analysis (TGA). The onset decomposition temperature of the imidazolium functionalized clay was 360°C. Transmission Electron Microscopy (TEM) of the composite showed mixed morphology with predominant fraction of intercalated clay platelets in the epoxy matrix. The onset decomposition temperature of the modified clay filled epoxy composite was found to be higher than that of pristine epoxy.