Biodegradability of bio-flour filled biodegradable poly(butylene succinate) bio-composites in natural and compost soil

This study investigated the biodegradability of PBS and bio-flour, which is a poly(butylene succinate) (PBS) bio-composite filled with rice-husk flour (RHF) reinforcing, in natural and aerobic compost soil. The percentage weight loss and the reduction in mechanical properties of PBS and the bio-composites in the compost soil burial test were significantly greater than those in the natural soil burial test. These results were supported by degraded surface of PBS and bio-composites observed through morphological study and the total colony count of natural soil was lower than that of compost soil. The biodegradability of the bio-composites was enhanced with increasing bio-flour content because the bio-flour is easily attacked by microorganisms. As the biodegradability test progressed over time up to 80 days, the molecular weight of PBS decreased in the soil burial test. We confirmed by attenuated total reflectance (FTIR-ATR) analyser that the chemical structures of PBS and the bio-composites were changed after the compost burial test. The glass transition temperature (T_g), melting temperature (T_m), crystallization temperature (T_c), heat of fusion (ΔH_f) and heat of crystallization (ΔH_c) of the natural and composted soil tested PBS were investigated using differential scanning calorimetry (DSC). From the results, we concluded that use of these bio-composites will reduce the environmental problems associated with waste pollution and the study findings support the predicted application of bio-composites as “green-composites” or “eco-materials”.     

Effect of electron beam irradiation on the structural properties of poly(vinyl alcohol) formulations with triphenyl tetrazolium chloride dye (TTC)

Films of poly(vinyl alcohol) (PVA) composites with triphenyl tetrazolium chloride (TTC) dye were prepared and exposed to various radiation doses delivered by accelerated electrons. The results showed that at a low dose of 50 kGy, the colour difference (ΔE^*) of PVA/TTC films was increased by ∼10 times of the initial value. However, the change in colour differences did not go systematically with increasing the TTC content, in which the composite with 1.5 wt% displayed higher value than that with 3.5 wt%. The differential scanning calorimetry (DSC) showed that the presence of the TTC dye caused a depression in the melting point (T_m) and heat of fusion (ΔH_f) of the PVA bulk polymer. However, the thermogravimetric analysis (TGA) showed that the presence of the TTC dye improved the thermal stability of PVA. Also, the tensile strength at break of PVA/TTC composites was improved after electron beam irradiation.     

Synthesis and characterization of poly(L‐lactic acid)–poly(ε‐caprolactone) multiblock copolymers by melt polycondensation

An Erratum has been published for this article in J. Polym. Sci. Part A: Polym. Chem. (2004) 42(22) 5845 New multiblock copolymers derived from poly(L‐lactic acid) (PLLA) and poly(ε‐caprolactone) (PCL) were prepared with the coupling reaction between PLLA and PCL oligomers with ? NCO terminals. Fourier transform infrared (FTIR), ¹³C NMR, and differential scanning calorimetry (DSC) were used to characterize the copolymers and the results showed that PLLA and PCL were coupled by the reaction between ? NCO groups at the end of the PCL and ? OH (or ? COOH) groups at the end of the PLLA. DSC data indicated that the different compositions of PLLA and PCL had an influence on the thermal and crystallization properties including the glass‐transition temperature (T_g), melting temperature (T_M), crystallizing temperature (T_c), melting enthalpy (ΔH_m), crystallizing enthalpy (ΔH_c), and crystallinity. Gel permeation chromatography (GPC) was employed to study the effect of the composition of PLLA and PCL and reaction time on the molecular weight and the molecular weight distribution of the copolymers. The weight‐average molecular weight of PLLA–PCL multiblock copolymers was up to 180,000 at a composition of 60% PLLA and 40% PCL, whereas that of the homopolymer of PLLA was only 14,000. A polarized optical microscope was used to observe the crystalline morphology of copolymers; the results showed that all polymers exhibited a spherulitic morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5045–5053, 2004     

Crystallization and melting behaviors of polystyrene-b-poly(ethylene-co-butene) block copolymers

Non-isothermal and isothermal crystallization behaviors of polystyrene-b-poly(ethylene-co-butene) (PSt-b-PEB) block copolymers with different compositions and chain lengths were investigated by differential scanning calorimetry (DSC). The results show that crystallization of PEB block is strongly dependent on the composition. Crystallization temperature (T_c), melting temperature (T_m) and fusion enthalpy (ΔH_f) increase rapidly with PEB volume fraction (V_E) for block copolymers with V_E below 50%, but there is little change when PEB block becomes the major component. Glass transition temperature (T_g) of the PSt block and order-disorder transition temperature (T_ODT) of block copolymers also have a weak effect. The isothermal crystallization kinetics results show that Avrami exponent (n) was strongly dependent on the composition and crystallization temperature. For the block copolymers with V_E below 38.7 vol%, the values of n vary between 0.9 and 1.3, indicating that crystallization is confined. For the PSt-b-PEB block copolymers with V_E higher than 50%, fractionated crystallization behavior is usually observed. A two-step isothermal crystallization procedure is applied to these block copolymers. It is found that breakout crystallization occurs at higher T_c, but confined at lower T_c. Two overlapped melting peaks are observed for the block copolymers with fractionated crystallization behavior after two-step crystallization, and only the higher melting peak corresponding to breakout crystallization can be used to derive equilibrium melting temperature.     

Structural investigation of polystyrene grafted and sulfonated poly(tetrafluoroethylene) membranes

Structural investigation of polystyrene grafted and sulfonated poly(tetrafluoroethylene) (PTFE) membranes prepared by radiation-induced grafting of styrene onto commercial PTFE films and subsequent sulfonation was carried out by differential scanning calorimetry and X-ray diffraction. The effect of the structural changes taking place in the membranes during the preparation procedure (grafting and sulfonation) and the variation of the degree of grafting on melting temperature (T_m), glass transition temperature (T_g), heat of melting (ΔH_m), and degree of crystallinity was studied. The melting temperature (T_m) was found to be independent of the degree of grafting unlike glass transition temperature (T_g), which was found to be a function of the degree of grafting. Moreover, the degree of crystallinity of the membranes was found to decrease with the increase in the degree of grafting. The results of this work suggest that grafting takes place in the entire amorphous region without any significant disruption in the crystalline structure of PTFE film and the decrease in the degree of crystallinity is mainly attributed to the dilution effect.     

Complex thermal evaluation for 2,2′-azobis(isobutyronitrile) by non-isothermal and isothermal kinetic analysis methods

Azo compounds are widely used in dyes, pigments, blowing agents, and initiators. Unfortunately, these compounds contain the bivalent –N–N– composition which might be cleavaged readily even under high ambient temperature. The self-accelerating decomposition might cause a runaway reaction and lead to a fire or explosion when the cooling system fails or other upsets occur. To investigate the thermal stability parameters of 2,2′-azobis(isobutyronitrile) with thermal hazard and mechanism, differential scanning calorimetry and thermal activity monitor III were applied with non-isothermal method and isothermal method to obtain onset temperature (T ₀), maximum temperature (T _max), and heat of decomposition (ΔH _d). Thermal stability parameters play a pivotal role in thermal analysis, leading particularly to complex evaluation of the inherently safer design during preparation, processing, transport, or storage. The results provide sufficient thermokinetic parameters for process safety in terms of proactive loss prevention program.     

Isothermal crystallization of concentrated amorphous starch systems measured by modulated differential scanning calorimetry

The slow isothermal crystallization of concentrated amorphous starch systems is measured by Modulated Differential Scanning Calorimetry (MDSC). It can be followed continuously by the evolution (stepwise decrease) of the MDSC heat capacity signal (Cp), as confirmed with data from X-ray diffractometry, Dynamic Mechanical Analysis, Raman spectroscopy, and conventional Differential Scanning Calorimetry. Isothermal MDSC measurements enable a systematic study of the slow crystallization process of a concentrated starch system, such as a pregelatinized waxy corn starch with 24 wt % water and 76 wt % starch. After isothermal crystallization, a broad melting endotherm with a bimodal distribution is observed, starting about 10°C beyond the crystallization temperature. The bulk glass transition temperature (T_g) decreases about 15°C during crystallization. The isothermal crystallization rate goes through a maximum as a function of crystallization time. The maximum rate is characterized by the time at the local extreme in the derivative of Cp (t_max), or by the time to reach half the decrease in Cp (t_1/2). Both t_max and t_1/2 show a bell-shaped curve as a function of crystallization temperature. The temperature of maximum crystallization rate, for the system studied, lies as high as 75°C. This is approximately 65°C above the initial value of T_g. Normalized Cp curves indicate the temperature dependence of the starch crystallization mechanism. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2881–2892, 1999     

Improving the Processing Ability and Mechanical Strength of Starch/Poly(vinyl alcohol) Blends through Plasma and Acid Modification

Summary: In this study, maleic anhydride (MA), and citric acid (CA) used as the processing additive and plasma treatment to improve the processing ability and mechanical strength of biodegradable starch/poly (vinyl alcohol) (PVA) blends were studied. The melt flow index (MFI) of starch/ glycerol/PVA (300g/60g/80g) blend was increased from 2.3g/10min to 32.7g/10min by adding 3g of MA and to 130 g/10min by adding MA and plasma treatment. The tensile strength of starch/glycerol/PVA blend increased from 3.48 to 6.21 MPa by adding 1.5g of MA and 1.5g of CA, while it increased to 6.26 MPa by plasma treatment. Esterification reaction which was evidenced by FTIR has been showed to improve the compatibility between starch and PVA when MA was dissolved into glycerol and glycerol grafted onto plasma pretreatment PVA. Thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) imaging were used to study the morphology of extruded blends.     

Linear unsaturated polyester + poly(?-caprolactone) blends: Calorimetric behaviour and morphology

Blends of a linear unsaturated polyester (LUP, commercially named Al100) with poly(?-caprolactone) (PCL) of different molecular weights have been studied. The miscibility and crystallinity have been analyzed through FT-IR spectroscopy, differential scanning calorimetry (DSC) and environmental scanning electronic microscopy (ESEM). All the blends were subjected to the same heat treatment consisting of crystallizing during 45 min at constant temperature (10, 20, 30 or 40 °C). The glass transition temperature, T_g, and fusion temperature, T_fus, have been determined in the whole composition range for each blend. The T_g-composition dependence and the high degree of crystallinity detected at intermediate blend compositions denote an anomalous behaviour that could indicate the lack of homogeneity (phase separation) in the different blends studied. The ESEM measurements confirm the lack of homogeneity of the amorphous region in blends with high content of LUP. The results have been discussed as a function of the crystallization temperature and the molecular weight of PCL.     

Formation of interpenetrated spherulites based on miscible crystalline polymer blends

The morphology and formation process of interpenetrated spherulites of poly(butylene succinate)/poly(vinylidene choloride‐co‐vinyl chloride) (PBSU/PVDCVC) blends were investigated by confocal laser scanning microscopy (CLSM). CLSM images showed that the dense fibrils of PBSU spherulites penetrated into the sparse PVDCVC spherulites. For a blend with PBSU content 50% and crystallization temperature T_c = 368 K, the simultaneous growth of PBSU and PVDCVC spherulites was observed. After PBSU fibrils collided with PVDCVC spherulites, they kept growing through PVDCVC spherulites. For a blend with PBSU content 30% and T_c = 363 K, PBSU started to nucleate after PVDCVC spherulites filled the whole space.     

A new route of manipulation of poly(L‐lactic acid) crystallization by self‐assembly of p‐tert‐butylcalix[8]arene and toluene

A novel nucleating agent (TBC8‐t), self‐assembled with p‐tert‐butylcalix[8]arene (TBC8) and toluene, was used to manipulate the crystallization behavior of poly(L ‐lactic acid) (PLLA). Toluene molecules were used to adjust the crystallization structure of TBC8. Differential scanning calorimetry results show that the crystallization peak temperature (T_c) and crystallization rate (ΔH_c/time) of PLLA nucleated with TBC8‐t are 132.3 °C and 0.24 J/gs, respectively, which are much higher than that with conventional nucleating agent‐talc (T_c = 119.3 °C, ΔH_c/time = 0.13 J/gs). The results of polarized optical microscopy demonstrate that TBC8‐t could greatly enhance the crystallization rate of PLLA by increasing the nucleation rate rather than crystal growth rate. Along with an improvement of the crystallization rate, the crystalline morphology of PLLA is also affected by TBC8‐t. The addition of TBC8‐t transforms most of the original spherulite crystals into sheaf‐like crystals. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1235–1243, 2010     

Studies on the thermal properties of caprolactam/long chain lactam copolymer

The thermal properties of caprolactam/long chain lactam copolymer were studied with a Perkin-Elmer DSC 7. The melting point (T _m), heat of fusion (δH _m), crystalline degree (X _c), crystallization temperature (T _c) and glass transition temperature (T _g) of the copolymers increase with decrease of the content of the log chain lactam. From the changes in the mechanical properties with corresponding changes in the thermal properties, it is clear that the copolymers are thermal plastic and elastic. In addition, it is found that the results at a heating rate of 10 deg·min^?1 are almost the same as that at 20 deg·min^?1 after thermal history is erased.     

Miscibility and thermal stability of poly(vinyl alcohol)/chitosan mixtures

The miscibility and the thermal behaviour of chitosan acetate (ChA) with poly(vinyl alcohol) (PVA) have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Chitosan is blended with poly(vinyl alcohol) in acetic acid solution and this solution is cast to prepare the blend film. From thermal curves the thermal transitions: T_g, T_m and characteristic temperatures of decomposition: T_di, T_max have been determined and compared. The influence of the degree of PVA hydrolysis on the thermal properties of blend systems has been discussed.Based upon the observation on the DSC analysis, the melting point of PVA is decreased when the amount of ChA in the blend film is increased. Though some broadening of the transition curves could be noticed (DSC, TGA and DMA), the obtained results suggest that in the solid ChA/PVA blends the components are poorly miscible. Only PVA sample with relatively low DH = 88% and hence low degree of crystallinity shows partial miscibility with ChA of relatively low molecular weight.     

Effects of mixing metal ions for the thermal runaway reaction of TMCH

1,1-bis(tert-Butylperoxy)-3,3,5-trimethylcyclohexane (TMCH) is commonly used as a crosslinking agent or an initiator of the heat-curing agent for polybutadiene rubber. Metal ions that remain in the pipelines or containers of manufacturing processes may affect the thermal stability of the organic peroxides. Moreover, pipelines or metal containers may contain some metal ions because of inner corrosive chemicals or surface deterioration, which may induce a chemical reaction, while TMCH is mixed with them. To avoid these unexpected chemical reactions, we focused on the thermal hazard analysis of TMCH mixed with metal ions, such as nickel(II) bromide or copper(II) bromide. The experiments can determine thermokinetic parameters, including exothermic onset temperature (T ₀), maximum temperature (T _max), and heat of decomposition (ΔH _d), under non-isothermal conditions by differential scanning calorimetry. Non-isothermal experimental results combined with isoconversional kinetic analysis can acquire further safety parameters, such as apparent activation energy (E _a) and time to maximum heating rate. The results of this study could be used as a proactive case for the storage of TMCH mixed with metal ions.     

Preparation and characterization of poly(2‐methyl‐1,5‐pentamethylene oxamide) (PM52) polymer

Poly(2‐methyl‐1,5‐pentaneoxamide) ( PM52) with relative viscosity up to 3.3 were synthesized using 2‐methyl‐1,5‐pentanediamine (M52) and dibutyl oxalate via spray/melt polycondensation. The obtained polyoxamide was characterized by FTIR, ¹H‐NMR, WAXD, DSC, and TGA. The T_m of PM52 was 200°C with a heat of fusion (ΔH_f) of 59.7 J·g−¹, crystallization temperature of 125°C, and a crystallization enthalpy (ΔH_c) of 42.6 J·g⁻¹. Isothermal crystallization studies revealed a 2‐dimensional crystallization phenomenon which didn't vary with change in crystallization temperature. TGA analysis revealed that the thermal stability of PM52 compared well with commercial PA6, and XRD studies revealed an α form of crystal structure and that the polymers possessed good crystallinity. Saturated water absorption of 4.6 wt% was recorded for the new polyoxamide synthesized as compared with 10.6 wt% for commercial PA6; such properties are good for applications in the food industry, plastics, and electronics industry where dimensional stability is a key requirement.     

Preparation and Characterization of Blend Films of Poly(Vinyl Alcohol) and Sodium Alginate

Blend films of poly(vinyl alcohol) (PVA) and sodium alginate (NaAlg) were prepared by casting from aqueous solutions. This blend films were characterized by tensile strength test, Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The miscibility in the blends of PVA and NaAlg was established on the basis of the thermal analysis results. DSC showed that the blends possessed single, composition‐dependent glass transition temperatures (T_gs), indicating that the blends are miscible. FT‐IR studies indicate that there is the intermolecular hydrogen bonding interactions, i.e. –OH…^?OOC– in PVA/NaAlg blends. The blend films also exhibited the higher thermal stability and their mechanical properties improved compared to those of homopolymers.     

Thermal hazard evaluation for methyl ethyl ketone peroxide mixedwith inorganic acids

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO₃, H₃PO₄ and H₂SO₄) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T ₀), heat of reaction (ΔH _d), time to maximum rate (TMR), maximum self heat rate (dT/dt)_max, adiabatic temperature rise (ΔT _ad), maximum pressure of decomposition (P _max) and so on. Mixing MEKPO with hydrochloric acid resulted in the lowest T ₀ among inorganic acids. Nitric acid not only lowered the T ₀ but also delivered the highest heat releasing rate or self heat rate (dT/dt), which was concluded to be the worst case in terms of contamination hazards during storage or transportation of MEKPO.     

Syntheses,Crystal Structures,and Thermal Properties of Energetic Semicarbazide Salt,Manganese(II) Salt,and Coordination Compound of 3,5‐Dinitrobenzoic Acid

Nitro compounds have been actively researched as driven by their potential to be high‐performing energetic materials. Herein, three new nitro compounds including semicarbazide 3,5‐dinitrobenzoate, (SCZ)(DNBA), manganese 3,5‐dinitrobenzoate dihydrate, [Mn(DNBA)₂(H₂O)₂]_n, and bis(semicarbazide) manganese(II) 3,5‐dinitrobenzoate, Mn(SCZ)₂(DNBA)₂, were synthesized and characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction analysis. The results indicated that the above mentioned compounds are ionic, polymeric, and molecular in nature, respectively. Moreover, their thermal decomposition properties were assessed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Their non‐isothermal reaction kinetics parameters, critical temperature of thermal explosion (T_bp), entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠), and free energy of activation (ΔG^≠) of the exothermic decomposition process were also calculated. Results suggest that there was a relationship between the structure and thermal stability.     

Evaluating the Thermal Hazard of Double-Base Propellant SQ-2 by Using Microcalorimetry Method

The thermal decomposition behavior of double‐base rocket propellant SQ‐2 was studied by a Calvet microcalorimeter at four different heating rates. The kinetic and thermodynamic parameters were obtained from the analysis of the heat flow curves. The critical temperature of thermal explosion (T_b), the self acceleration decomposition temperature (T_SADT), the adiabatic decomposition temperature rise (ΔT_ad), the time‐to‐explosion of adiabatic system (t), critical temperature of hot‐spot initiation (T_cr), critical thermal explosion ambient temperature (T_acr), safety degree (SD) and thermal explosive probability (P_TE) were presented to evaluate the thermal hazard of SQ‐2.     

Thermal characterization and kinetic analysis of nano‐ and micro‐Al/NiO thermites: Combined experimental and molecular dynamics simulation study

In the experimental part of this study, thermal properties of the Al and NiO composites in micro‐ and nano‐sized Al are investigated. Differential scanning calorimetry (DSC) analysis of the onset temperatures of ignition, activation energy (E_a), frequency factor (A), rate constant (k), critical ignition temperature of thermal explosion (T_b), and self‐accelerating decomposition temperature (T_SADT), as well as the thermodynamic parameters (ΔS^≠ , ΔH^≠ , and ΔG^≠ ) are used to explore the thermal behavior and analyze the kinetics. Thermal analysis suggests that the mechanism is based on solid–solid diffusion and liquid–gas for the nano‐ and micro‐Al/NiO composite, respectively. Our results indicate that the incorporation of nano‐Al particles can significantly reduce the ignition temperature, E_a, A, k, T_b, and T_SADT. In the second part of this work, molecular dynamics (MD) simulation is used to investigate the behavior of Al/NiO thermite reaction using the Reaxff force field to evaluate the experimental results. Theoretically, MD results show 1,154 K as the reaction ignition temperature, which is in reasonably good agreement with experimental temperature of 893°C (1,166 K). The radial distribution function (RDF) shows that no reaction occurs at 500 K but it is complete at 1,200 K.