Differential Scanning Calorimetry Characterization Research Articles

DSC characterisation of chemically reduced electrolytic manganese dioxide

The thermal decomposition of electrolytic manganese dioxide (EMD), in an inert atmosphere, and the effect of chemical reduction on EMD, using 2-propanol under reflux (82°C), was investigated by differential scanning calorimetry (DSC). This study is an extension of a study investigating the thermal decomposition of EMD and reduced EMD by TG-MS (J. Therm. Anal. Cal., 80 (2005)625)). The DSC characterisation was carried out up to 600°C encompassing the water loss region up to 390°C and the first thermal reduction step. Water removal was observed in two distinct endothermic peaks (which were not deconvolved in the TG-MS) associated with the removal of bound water. For the lower degrees of chemical reduction, thermal reduction resulted in the formation of Mn2O3; for higher degrees of chemical reduction, the thermal reduction resulted in Mn3O4 at 600°C. In the DSC the thermal reduction of the EMD and chemically reduced specimen was observed to be endothermic. The reduced specimens, however, also showed an exothermic structural reorganisation.

Differential scanning calorimetry characterization of the cure of phenol-formaldehyde adhesive in the presence of copper-based preservative treated wood

The interference of copper based preservative treated southern yellow pine (SYP) on the cure of phenol-formaldehyde adhesives was investigated by using differential scanning calorimetry (DSC). Copper preservatives used in this study include copper azole (NS), alkali copper quat (ACQ)-type C (NW). Three commercial phenol-formaldehyde (PF) adhesives used for oriented strand board (OSB) face area, core area and a plywood adhesive were studied. The curing peak temperature and peak time of OSB core and face PF resin shifted to higher temperature and duration in the presence of CCA, NS, and NW-treated SYP compared to that in untreated SYP. The above treatments interfere with the cure of OSB core and face PF resin. Untreated SYP showed a curing accelerating effect on the cure of plywood adhesive, but the accelerating effect of copper-treated SYP on the cure of plywood resin was not significant.

Water flux, DSC, and cytotoxicity characterization of membranes of cellulose acetate produced from sugar cane bagasse, using PEG 600

In this article, cellulose acetate produced through the homogeneous acetylation of sugar cane bagasse cellulose was used to produce membranes, using poly(ethyleneglycol) 600 (PEG 600) as an admixture. The membranes were characterized using water flux measurements (Payne’s cup), differential scanning calorimetry (DSC) and neutral red uptake (cytotoxicity). The results showed that PEG 600 acts as a crystallinity inductor and/or pore former in the cellulose acetate matrix. The induction of crystallinity is important for this system since it had not been reported on the literature yet. The results also demonstrated that the studied membranes present a nontoxic behavior.

Compatibility of HDPE/postconsumer HDPE blends using compatibilizing agents

AbstractMechanical properties, molecular weight, X‐ray diffraction, and differential scanning calorimetry (DSC) characterization of blends of virgin high‐density polyethylene (HDPE) with two types of recycled material were investigated. The recycled came from urban plastic waste; one kind was only washed and grounded and the other was extruded and pelletized to remove most of contaminant particles. Starting with the 30/70 virgin/grounded recycled and 50/50 virgin/pelletized recycled blends the recycled content was increased in both blends and compatibilizing agents were used to increase the blend performance. A mixture of phenolic antioxidants and phosphite costabilizers under the name of Recycloblend™, ethylene vinyl acetate (EVA) copolymer, low‐density polyethylene (LDPE), and linear low density polyethylene (LLDPE) were used as compatibilizers. The effect of these additives and the recycled content on the performance of extrusion blow‐molded bottles was determined. The results suggest that blends of virgin/grounded recycled and virgin/pelletized recycled HDPE, in general, were not significantly different among each other and both had a quite similar behavior than the virgin HDPE when compatibilizing agents were used. The addition of compatibilizing agents yielded a material with properties similar to those for the virgin HDPE, helping to reduce the effect of polymers degradation on the rheological and mechanical behavior, with Recycloblend and LLDPE being the most effective for the blends with grounded recycled material, and LLDPE y EVA, for the blends with pelletized recycled. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3696–3706, 2006

DSC characterization of ion beam modifications in ion conducting PEO–salt polymers

Ion conducting polymer films have been prepared by complexing non-conducting poly-(ethylene-oxide), PEO, with x fraction of NH4ClO4 salt. Since its electrical conductivity showed a maximum at x somewhere between 0.18 and 0.19, such polymer films having 17 and 19wt% salt, have been chosen and irradiated by 160MeV Ne6+ beam. The films have been investigated by differential scanning calorimetry (DSC) and ac impedance spectroscopy before and after the irradiations. Irradiation-induced shift of an endotherm in our DSC indicates a rise in the melting temperature from 54.6°C to 57.9°C for the 19% film. Cross-linking by the Ne-irradiation making the polymer structure more rigid can explain this as well as our other observation of a decrease in electrical conductivity.

Differential scanning calorimetry characterization of urea–formaldehyde resin curing behavior as affected by less desirable wood material and catalyst content

AbstractDifferential scanning calorimetry was applied to investigate the curing behavior of urea–formaldehyde (UF) resin as affected by the catalyst content and several less desirable wood materials (e.g., wood barks, tops, and commercial thinnings). The results indicate that the reaction enthalpy of UF resin increased with increasing catalyst content. The activation energy and peak temperature of the curing UF resin generally decreased with increasing catalyst content at lower levels of catalyst content. However, with further increases in catalyst content, the changes in the activation energy and peak temperature were very limited to nonexistent. The hydrolysis reaction of the cured UF resin occurred during the latter stages of the curing process at both lower level (<0.2%) and higher level (>0.7%) catalyst contents. This indicates that there existed an optimal range of catalyst content for the UF resin. The curing enthalpy of the UF resin decreased with increasing wood raw materials present due to the effect of diffusion induced by the wood materials and the changes in the phase of the curing systems. This suggests that the curing reactions reached a lower final degree of conversion for the wood–resin mixtures than for the UF resin alone. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2027–2032, 2005

DSC study of cure kinetics of DGEBA-based epoxy resin with poly(oxypropylene) diamine

A kinetic study of cure kinetics of epoxy resin based on a diglycidyl ether of bisphenol A (DGEBA), with poly(oxypropylene) diamine (Jeffamine D230) as a curing agent, was performed by means of differential scanning calorimetry (DSC). Isothermal and dynamic DSC characterizations of stoichiometric and sub-stoichiometric mixtures were performed. The kinetics of cure was described successfully by empirical models in wide temperature range. System with sub-stoichiometric content of amine showed evidence of two separate reactions, second of which was presumed to be etherification reaction. Catalytic influence of hydroxyl groups formed by epoxy-amine addition was determined.

Criteria dilemma of phase behavior in ternary blends comprising polystyrene, poly(alpha-methyl styrene), and poly(4-methyl styrene)

A ternary blend system of polystyrene (aPS), poly(α-methyl styrene) (PαMS), and poly(4-methyl styrene) (P4MS) (blends of three styrenic homopolymers of similar molecular structures) was investigated by using differential scanning calorimetry (DSC), polarized-light optical microscopy (POM), scanning electron microscopy (SEM), and solid-state 13C cross-polarization/magic angle spinning nuclear magnetic resonance (CP/MAS NMR). This ternary system of aPS/PαMS/P4MS exhibits a small miscibility loop only at relatively high percentages of PαMS (≥80%), while most of the aPS/PαMS/P4MS compositions exhibit two coexisting aPS/PαMS and aPS/P4MS phases in the immiscibility loop. In the immiscible loop, SEM measurements revealed evidence in contrasting with DSC for criteria of miscibility. DSC characterization revealed a single T g for most ternary blend compositions; however, SEM graphs apparently indicated sub-micron phase domains, except for several PαMS-rich compositions (>80%). The T 1 H and T 1 ρ H techniques using NMR were found to resolve the dilemma between the conventional thermal analysis and microscopy results, and indeed supported that the ternary blends at above 80% PαMS are completely homogeneous on the molecular level. Attempts have been made to resolve the seemingly contradictory interpretations on the complex ternary phase structures and domains from the DSC, and microscopy results.

Study of cure kinetics of epoxy-silica organic–inorganic hybrid materials

Cure kinetics of organic–inorganic hybrids based on epoxy resin was investigated, using differential scanning calorimetry (DSC). Thermoset hybrid materials were prepared from diglycidyl ether of bisphenol A (DGEBA) as organic precursor, and 3-glycidyloxypropyltrimethoxysilane (GLYMO) as inorganic precursor. Precursors were polymerised simultaneously using poly(oxypropylene)diamine (Jeffamine D230) as a curing agent. Isothermal DSC characterisation of DGEBA/Jeffamine system and two hybrid DGEBA/GLYMO/Jeffamine systems, with DGEBA and GLYMO mixed in mass ratios of 2:1 and 1:1, respectively, was performed at different temperatures. Applicability of empirical models, commonly used to describe the curing kinetics of thermosets, to hybrid systems was investigated, and the resulting parameters were tested on dynamic DSC scans. Additionally, prepared materials were studied by FTIR and the extraction in tetrahydrofuran. The presence of inorganic phase was found to hinder complete cross-linking of organic phase and influence the kinetics of cure.

Changes in polymer foils used in food packaging tested by using differential scanning calorimetry

This work is an experimental study of the differential scanning calorimetry characterisation of polymer materials used in food packaging materials, such as polypropylene (0.03 mm), polyethylene (0.1 and 0.03 mm), poly(D-(-)-Β-hydroxybutyrate) (powder), two-layered polypropylene (0.064 mm), and two-layered polypropylene with poly-vinylidene-chloride (0.012/0.021). The polymer stability was checked by simulation of conditions during food preparation in microwave ovens, sterilisation or rapid freezing.The materials were tested in the temperature range from 40 to 200‡C at different scan rates from 2 to 30°C min−1 during heating or cooling. The enthalpies show a high correlation coefficient (0.964) with scan rate. All samples undergo phase change in the temperature range from 107 to 173°C during heating and enthalpies are in the range from 31.8 to 71.1Jg−1. Upon subsequent cooling from 200°C, the temperature range of phase changes is shifted to lower temperatures from 86 to 102°C with enthalpies ranging from 30.4 to 57.8 J g−1.Experiments with exposure of polymers to microwave radiation and freezing prove that the phase change considering the temperature range is very similar in all experiments.

Novel polymer electrolyte composed of poly(ethylene oxide), lithium triflate, and benzimidazole

AbstractThis work has demonstrated that the incorporation of benzimidazole derivatives, 2,2′‐p‐phenylene‐bisindole (PPBI), enhances the ionic conductivity of a poly(ethylene oxide) (PEO)–based electrolyte by 20 times more than the plain system. Specific interactions among amino group, ethyl oxide, and lithium cation were investigated using differential scanning calorimetry (DSC), FTIR, and alternating current impedance. The DSC characterization confirms that the initial addition of PPBI is able to enhance the PEO crystallinity attributed to the interaction between the negative charge from the amino group and the lithium cation. Three types of complexes are present: complex I is present in the PEO phase, complex II resides at interphase, and complex III is located within the PPBI domain. Complex II plays the key role in stabilizing these two microstructure phases. FTIR spectra confirm that because of the presence of PPBI one is able to dissolve lithium salts more easily than in the plain electrolyte system and thus increase the fraction of free ions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 719–725, 2004

STUDY ON THE GRAFT REACTION OF MALEIC ANHYDRIDE ONTO METALLOCENE-BASED POLYETHYLENE–OCTENE ELASTOMER

Grafting of maleic anhydride (MAH) onto metallocene based polyethylene–octene elastomer (POE) was studied in this article. By the results of Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and differential scanning calorimetry (DSC), it was confirmed that POE was grafted with MAH but the crosslinking reaction was accompanied by the predominant graft reaction due to a competition of POE macro-radical and excited MAH. Effects of various parameters such as monomer loading, initiator loading, and reaction time on grafting percentage and gel yield were also investigated. It was also found that the grafting percentage and the gel yield, at equilibrium, were both higher for POE containing lower degree of comonomer content. From the result of DSC characterization, it was shown that the change of crystallinity is slight for POE-g-MAH copolymer when the gel was removed from the copolymer. So one thought that the effect of gel formation on the properties of POE-g-MAH can be neglected due to the low gel yield. It was also proved that strength and elongation at break are both decreased while the grafting percentage was increased. Finally, the method proposed in this research can produce POE-g-MAH copolymer with low gel.

Solid-state electrolyte nanocomposites based on poly(ethylene oxide), poly(oxypropylene) diamine, mineral clay and lithium perchlorate

This work has demonstrated that the addition of specific amount of poly(oxypropylene) diamine (d2000) and mineral clay in the PEO-based electrolyte system can form the high conductivity film at room temperature. Specific interactions among silicate layer, d2000, ether oxygen, and lithium cation have been investigated using differential scanning calorimetry (DSC), alternating current impedance (AC impedance) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the addition of 25 wt[percnt] d2000 is able to produce low T g and fully amorphous (PEO) 8LiClO 4/d2000 electrolyte system which produce the good environment for ionic transfer. Additionally, the incorporation of the mineral clay into the (PEO) 8LiClO 4/d2000 electrolyte system can sustain the polymeric mechanical property by its huge surface area and enhance the conductivity due to the specific interaction between silicate layers and lithium cation. FT-IR spectra confirm that the incorporation of the clay is able to dissolve the lithium salts more effectively and resulting to the higher fraction of free anions due to the strong interaction between negative charges of the silicate layers and lithium cations of the lithium salt.

DSC and DMTA characterization of ternary blends

The phase behavior of ternary blends made of poly(epichlorohydrin) (PECH), poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). DMTA measurements have been shown to be more sensitive than DSC for the detection of a second phase, for the determination of the composition of each phase, and the distribution of PECH in each of them. About 70% PECH was required to obtain a single narrow Tg in the ternary system, which suggests a single homogeneous phase in the limit of sensitivity of DMTA. This study also emphasizes the importance of the composition of the immiscible polymer pair (i.e. the PVAc/PMMA pair in the PECH/PVAc/PMMA system), in addition to the thermodynamic interaction parameters, for controling the phase behavior of ternary systems.

DSC study on simultaneous interpenetrating polymer network formation of epoxy resin and unsaturated polyester

AbstractA kinetic study on simultaneous interpenetrating polymer network formation of epoxy resin based on diglycidyl ether of Bisphenol A (DGEBA) and unsaturated polyester (UP) was performed by means of differential scanning calorimetry (DSC). Isothermal DSC characterizations of neat resins and their mixture (in a weight ratio of 50/50) were performed at different temperatures. Dynamic DSC characterization of the systems were performed at three different heating rates. A lower total heat of reaction developed during simultaneous polymerization in dynamic DSC tests was found, compared to the total heats developed during pure resins network formation. This phenomenon can be interpreted as an effect of network interlock that could not be compensated for completely by an increase in curing temperature. The kinetics of the reactions was described by empirical models. The DGEBA, in a 50/50 UP/DGEBA blend, indicated a higher rate constant than the pure DGEBA. The obtained results suggests that the hydroxyl end group of UP in the blend provided a favorably catalytic environment for the DGEBA cure. The results are in good agreement with the literature data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2689–2698, 2002

The novel polymer electrolyte nanocomposite composed of poly(ethylene oxide), lithium triflate and mineral clay

This work has demonstrated that the addition of optimum content of D-2000 modified montmorillonite enhances the ionic conductivity of the poly(ethyl oxide) (PEO) based electrolyte by nearly sixteen times more than the plain system. Specific interactions among silicate layer, ethyl oxide and lithium cation have been investigated using alternating current impedance (A.C. impedance), differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the initial addition of clay is able to enhance the PEO crystallinity due to the interaction between the negative charge from the clay and the lithium cation. Three types of complexes are present; complex I is present in the PEO phase, complex II resides at the interphase, and complex III is located within the clay domain. Complex II plays the key role in stabilizing these two microstructure phases. FT-IR spectra confirm that the existence of clay is able to dissolve the lithium salts, easier than the plain electrolyte system and thus increases the fraction of free ions.

Synthesis and characterization of amphiphilic graft copolymers based on poly(styrene-co-maleic anhydride) with oligo(oxyethylene) side chains and their GPC behavior

A series of amphiphilic graft copolymers were synthesized based on poly(styrene-co-maleic anhydride) (SMAs) (backbone copolymers) and methoxypolyethylene glycols (MPEGs) (grafts) in this study. Selection of proper reaction conditions using p-toluenesulfonic acid (PTSA) as catalyst and toluene as solvent in the present research can prevent crosslinking reactions which may occur due to the presence of di-functional polyethylene glycol in the commercial MPEGs. The structures and compositions of the graft copolymers were determined by gel permeation chromatography (GPC) and 1H NMR analysis. It is noteworthy that the GPC behavior of these graft copolymers follows the rule of thumb for GPC, i.e. the higher molecular weight copolymers have lower retention volumes. This is very different from the GPC behavior of similar graft copolymers reported previously in the literature. Also, differential scanning calorimetry (DSC) characterization shows that there are two transition temperatures for some of these amphiphilic copolymers owing to the existence of another aggregation phase of MPEG grafts.

Carbohydrate/monomer complexes in aqueous polymerizations: methylated-beta-cyclodextrin mediated aqueous polymerization of hydrophobic methacrylic monomers.

Hydrophobic methacrylic monomers were polymerized in aqueous media using methylated (1.8)-beta-cyclodextrin (MeCD) additives. Hydrophobic monomers tert-butyl methacrylate (tBuMA), cyclohexyl methacrylate (CMA), and 2-ethylhexyl methacrylate (2EHMA) were each dissolved in chloroform with MeCD. Chloroform was then evaporated to yield solid monomer/cyclodextrin complexes. Complexes were shown by 1H NMR and thermogravimetric analysis (TGA) to have molar ratios of monomer to MeCD as high as 0.72/1.00. The water-soluble complexes were readily polymerized in aqueous media using free radical initiation. During polymerization, hydrophobic methacrylic polymers precipitated and the majority of MeCD remained in solution. Poly(alkyl methacrylates) synthesized via this method exhibited number-average molecular weights ranging from 50,000 to 150,000 with polydispersities from 3.2 to 5.5 depending on monomer structure, and isolated yields were as high as 86%. Additionally, corresponding methacrylic/carbohydrate films were prepared and examined. High molecular weight poly(tBuMA), poly(CMA), and poly(2EHMA) were blended with MeCD to produce optically clear films with as high as 20 wt % MeCD. Differential scanning calorimetry (DSC) characterization indicated that the glass transition temperatures of these novel carbohydrate blends were controllable over a 20 degrees C range depending on the relative concentration of each component.

Novel fabrication technique of TiNi shape memory alloy film using separate Ti and Ni targets

This paper proposes a novel fabrication technique of TiNi shape memory alloy (SMA) film and verifies the validity by showing the actual fabrication process and the final results. Special attention is paid to the characterization of differential scanning calorimetry (DSC). An essential part of the fabrication process is the co-sputtering from separate pure Ti and Ni targets. Co-sputtering is carried out using a multi-target sputtering system where RF power for each target can be controlled independently. As-sputtered film is vacuum-annealed. The phase transformation behavior of the fabricated film is investigated by DSC and temperature-controlled X-ray diffractometry (XRD). Finally, shape recovery behavior is observed. The proposed novel fabrication technique is validated by these results.

Interactions between hydroxypropylcelluloses and vapour/liquid water

Understanding of the uptake of water vapour or liquid water by cellulose-based polymers is important because of the influence of these processes on many of the biologically or technologically relevant properties of these polymers. In this work we studied these processes in the cases of twelve hydroxypropylcelluloses with low or medium-high degrees of substitution (L-HPCs and HPCs, respectively), characterization of which showed significant differences in structural and physical parameters (substitution pattern, crystallinity, particle size, specific surface area, and intraparticular porosity). Water vapour sorption–desorption isotherms determined to characterize the uptake of water vapour were fitted well by the Young–Nelson model, the optimized parameters of which indicated that at all relative humidities the capacity to bind water vapour as a surface monolayer is greater for HPCs than L-HPCs, but the capacity to absorb water vapour internally is greater for L-HPCs than HPCs. Guggenheim–Anderson–deBoer (GAB) models fitted the sorption–desorption isotherms less well. Differential scanning calorimetry (DSC) experiments showed all sorbed water vapour to be held as non-freezing water. Isoperibol microcalorimetry experiments carried out to investigate interactions with liquid water showed enthalpies of hydration/dissolution of between −62.86 and −71.35 J g −1 for L-HPCs and between −82.95 and −99.80 J g −1 for HPCs, and DSC showed average numbers of non-freezing water molecules per polymer repeat unit of 2.65–4.19 for L-HPCs and 18.10–22.42 for HPCs. DSC characterization of the kinetics of the water uptake by 10 mg compacts obtained by direct compression of hydroxypropylcelluloses showed faster uptake by L-HPC compacts than by HPC compacts, among which there were significant differences in capacity for diffusive uptake. The explanations of the above differences in terms of the different substituent contents, particle sizes and porosities of the HPCs is supported by multiple linear regression analyses.