Decrease In Melting Enthalpy Research Articles

Bifonazole: a missing case of polymorphism

AbstractBifonazole, an imidazole-based antifungal drug, can be easily amorphized and crystallizes upon reheating at moderate scanning rate. Driven by recent results in literature reporting for this compound the appearance of polymorphism under different thermal histories, the present study presents an extensive calorimetric characterization of bifonazole in its crystalline and amorphous state. A rich scenario in crystallization behaviour has been found, implying that the behaviour observed on reheating scans can strongly depend on the previous thermal history and on the distribution in number and size of crystalline regions. In particular, the decrease in melting enthalpy during reheating, related to the increase of the heating rate, can be stated to be the result of a partial crystallization of the sample. Additionally, the temperature intervals more favourable to crystal nucleation and growth, respectively, have been determined, thanks to the choice of ad hoc time–temperature profiles. Finally, also the nucleation occurrence in time at high temperature has been investigated using a suitable DSC protocol. The overall results show how complex can be the cold-crystallization behaviour of a molecular liquid.

Thermophysical Properties of POLWAX LTP ST Paraffin Doped with or without Carbon Nanotubes or Silver Nanowires and Passive Cooling of a High-Power LED Panel

Commercially available paraffin wax LTP ST, manufactured in Poland by POLWAX, was used as a phase change material (PCM) for passive cooling of an LED panel containing 28 high power light emitting diodes (LEDs). Paraffin wax LTP ST of density ρ = 930 kg·m−3 at room temperature (RT) was chosen over other POLWAX waxes (LUXOLINA, LUXOLINA-ST, and LTP 56-20) because of its melting point range (44.5–55.4 °C), relatively high latent heat of fusion ΔH = 218.8 J·g−1, high specific heat Cp = 2.11 J·g−1K−1 and thermal conductivity k = 0.233 Wm−1K−1 at 0 °C. The thermophysical properties were studied in samples of pure LTP ST paraffin and doped with multi-walled carbon nanotubes (1.99, 3.49, 5.35, and 10.49 wt%, MWCNTs) or silver nanowires (0.26, 0.32, 1.06, 2.10, and 7.35 wt%, SNWs). Analysis of the thermal effects of doped samples showed a relative increase in the degree of subcooling, averaging 100% for MWCNT and 46% for SNW, a relative 15÷25% decrease in enthalpy of melting for MWCNT and 14÷16% for SNW. A 44% increase in thermal conductivity was found for the sample containing 5.35 wt% MWCNTs and a 91% increase for 1.06 wt% SNW. The results of cooling efficiency tests for three types of developed heat sinks fabricated of AW-2017A aluminum alloy are presented, i.e., (a) full system without PCM filling, (b) system with PCM chamber without intracellular ribs, (c) and system with PCM chamber with intracellular fins.

Fortification of chocolate with microencapsulated fish oil: Effect of protein wall material on physicochemical properties of microcapsules and chocolate matrix

Protein stabilized fish oil microcapsules were incorporated into chocolates in order to design fortified product which could bear the nutritional claim “source of or high omega-3 fatty acids”. Protein wall material (soy, whey and potato) influenced microcapsules and chocolate performance. Soy protein resulted in the smallest microcapsules with the lowest content of surface oil. Peroxide values were low even after 14 days of microcapsules storage. Incorporation of microcapsules into chocolate led to increase in Casson viscosity and breaking force as well as decrease in melting enthalpy, due to prevalence of particle–particle over fat-fat interactions. Increase in microcapsules concentration resulted in chocolate with poorer snap and higher tendency to fat bloom formation. Whey protein microcapsules, having the largest diameter, resulted in chocolate with the lowest breaking force and melting enthalpy and the highest whitening index. In general, microcapsules addition did not require chocolate production modification and led to sensory acceptable product.

Encapsulation of polyethylene glycol as a phase change material using alginate microbeads to prevent temperature fluctuation- Case study: Fish packaging

Encapsulated PCM (phase change materials) has been developed to provide a thermal buffering system for food packaging. In this study, polyethylene glycol 400 (PEG) as a PCM was encapsulated in alginate in concentrations of 30, 40 and 50% (W/V) using calcium chloride (CaCl 2 ) in concentrations of 0.5, 1, 1.5%. Crystallization temperature, melting temperature and melting enthalpy of PCM decreased after encapsulation. The optimum encapsulated PEG (50% of PEG and 0.5% CaCl 2 ) had a diameter of 2.21 ± 0.54 μm. FTIR analysis of encapsulated microcapsules indicated characteristic peaks of alginate and pure PEG. TGA analysis showed more thermal stability for encapsulated PCM than pure PCM. After 100 thermal cyclic test microencapsulated beads showed some decrease in melting enthalpy, while other features of encapsulated PCM were almost intact. Encapsulated PCM was used for fish packaging to determine its effectiveness in controlling temperature fluctuation. When the packages were removed from the freezer, fish samples with the package containing encapsulated PCM and control package reached to 0 °C after 6500s and 3000s, 5 °C after 9030s and 4040s, 10 °C after 11520s and 5053s, and 25 °C after 19000s and 8200s, respectively. The data showed that using encapsulated PEG in fish packaging had a positive effect on preserving pH, water holding capacity, total volatile basic nitrogen, and thiobarbituric acid value. The results demonstrated that alginate could effectively encapsulate PEG, and the produced encapsulated PCM can be used for increasing of shelf life of perishable food during temperature fluctuations. • Novel food packaging materials were developed using alginate based PCM microcapsules. • The efficiency to maintain the cold temperature in packaged fish increased. • The shelf-life of product emproved by application of encapsulated PEG in packages.

Role of C2 methylation and anion type on the physicochemical and thermal properties of imidazolium-based ionic liquids

This study focused on the effects of methylation and different anions (Br − and Cl − ) on the physicochemical and thermal properties of [C 16 MIM]X and [C 16 MMIM]X, belonging to the imidazolium-based ionic liquid (IL) family. The effect of methylation on the transmittance in the fingerprint region of the Fourier transform infrared (FT-IR) spectrum was observed as a blue shift, and a new peak associated with the C-N stretching bond was obtained. In contrast, in the functional group region, the frequency shift was related to the change in the vibrational mode from C2-H-X to C2-methyl-X. In general, methylation resulted in an increase in decomposition temperature, an increase in melting temperature, and a decrease in melting enthalpy, leading to a reduction in entropy. The trends observed for the decomposition temperature, melting temperature, and melting enthalpy with different anions depended on the strength of the Brønsted acids and hydrogen bonds of the Br − and Cl − based anions. The thermal conductivity of the methylated ILs increased with an increase in temperature. In contrast, for the non-methylated (protonated) ILs, the thermal conductivity of [C 16 MIM]Br decreased with an increase in temperature, while the opposite trend was observed for [C 16 MIM]Cl. The data were compared with those of the short alkyl chain and weakly coordinating anion of NTf 2 . The analysis was performed considering different phases, the prominent role and different behaviour in the hydrogen bonding at the C2 position of the imidazolium ring upon methylation, and the significant change in viscosity, which can influence the IL structure.

Physicochemical Properties of Milkfish Gelatin-Natural Starch Composite

Halal gelatin sourced from fish can be improved in quality through mixing with other polymers so that it can be an alternative as food, pharmaceutical, and cosmetic ingredient. The purpose of this study was to determine the characteristics of milkfish scale gelatin after the formation of a composite with corn, potato, and cassava starch to be used as a pharmaceutical and food excipient.
 The gelatin composite (FMG) of milkfish scales with corn, potato, and cassava starch (GM, GS, and GC) was made by casting method, using a ratio of gelatin and starch (4,5:0,5). Characteristic assessment includes organoleptic, viscosity, swelling index, FT-IR spectroscopy, and Calorimetry (DSC). Data analysis used a non-parametric One Way ANOVA statistical method (p<0.05).
 The composites produced from mixing FMG with corn starch (GM), potato (GS) and cassava (GC) showed hygroscopic properties, increased viscosity values and decreased swelling index in GM (7.89 cP & 25.0%), GS (8 .36 cP & 21.0%), and GC (8.64 cP & 12.7%), compared to FMG (0.11 cP & 75%) at p < 0.05. The behavior of the composite FT-IR spectrum follows the FMG spectrum pattern with a shift in wavenumber in the typical bands (Amide A, Amide B, Amide I, Amide II, and Amide III) in the gelatin spectrum. There was a shift of Tg to higher values in GM and GS, Tm increased in GM and GC, and all composites showed a decrease in melting enthalpy.
 The spectral pattern of the composite follows the typical spectral pattern of FMG. GM, GS, and GC composites showed increased viscosity, water retention, and thermal stability compared to FMG. GM and GS may be used as pharmaceutical and food excipients.

Degradation of Fatty Acid Phase-Change Materials (PCM): New Approach for Its Characterization

The use of adequate thermal energy storage (TES) systems is an efficient way to achieve thermal comfort in buildings reducing the cooling and heating demand. Besides, deploy phase change materials (PCM) to meet and enhance the TES needs is highly effective and widely studied. In this paper, a study of the degradation of two fatty acids is presented, capric and myristic acids, in order to evaluate whether their thermo-physical properties are affected throughout time during service. This was carried out by means of two different types of thermal treatments: degradation at constant temperature (thermal stability test), 60 °C during 100 h and 500 h, and degradation with heating and cooling cycling (thermal cycling stability), between a temperature range from 15 °C to 70 °C with 0.5 °C/min ramp during 500 and 1000 cycles. Despite no significant changes were measured for myristic acid, experimental results revealed a decrease of melting enthalpy of 6.6% in capric acid thermally treated for 500 h. Evidences of chemical degradation were found that might explain the decrease in thermophysical properties during use.

Thermostability of rat sarcoma M1 procollagen solutions, procollagen fibers and whole tissues

In close to equilibrium conditions (1° per 400 min), the DSC measurements demonstrated that the melting parameters of white rat sarcoma M1 procollagen equaled to Tm = 34.4 °C and ΔTm = 2.7°, and the same parameters of fibers reconstructed from those solutions of procollagen were Tm = 38.5 °C and ΔT = 3.1°. These values were by 1.0° lower and 0.8° wider, and by 1.7° lower and 0.7° wider in comparison with the parameters of procollagen and fibers of healthy rat tissue, accordingly. The simultaneous increase in melting temperature and melting width, and a weak decrease in melting enthalpy demonstrated that sarcoma M1 procollagen had some defects. The considerable decrease by 7° in melting temperature and decrease in thermostability of procollagen fibrils in case of sarcoma M1 in comparison to the healthy norm gives a good prospective potential of using this approach as a quick DSC test to detect various sarcomas, including human sarcomas, by comparing the biopsy material or postsurgical tissues with the normal samples.

Fully biobased biodegradable poly(l‐lactide)‐b‐poly(ethylene brassylate)‐b‐poly(l‐lactide) triblock copolymers: synthesis and investigation of relationship between crystallization morphology and thermal properties

AbstractWell‐defined poly(l‐lactide‐b‐ethylene brassylate‐b‐l‐lactide) (PLLA‐b‐PEB‐b‐PLLA) triblock copolymer was synthesized by using double hydroxyl‐terminated PEBs with different molecular weights. Gel permeation chromatography and NMR characterization were employed to confirm the structure and composition of the triblock copolymers. DSC, wide‐angle X‐ray diffraction, TGA and polarized optical microscopy were also employed to demonstrate the relationship between the composition and properties. According to the DSC curves, the cold crystallization peak vanished gradually with decrease of the PLLA block, illustrating that the relatively smaller content of PLLA may lead to the formation of a deficient PLLA type crystal, leading to a decrease of melting enthalpy and melting temperature. Multi‐step thermal decompositions were determined by TGA, and the PEB unit exhibited much better thermal stability than the PLLA unit. Polarized optical microscopy images of all the triblock samples showed that spherulites which develop radially and with an extinction pattern in the form of a Maltese cross exhibit no ring bond. The growth rate of the spherulites of all triblock samples was investigated. The crystallization capacity of PLLA improved with incorporation of PLLA, which accords with the DSC and wide‐angle X‐ray diffraction results. © 2019 Society of Chemical Industry

Retardation of Crystallization through the Addition of Dairy Phospholipids

AbstractThe objective of this work was to identify the effects that milk phospholipids (PL) have on crystallization of anhydrous milk fat (AMF). Three mixtures were prepared by adding 0%, 0.01%, and 0.1% PL to AMF. Each mixture was crystallized for 90 min at 24, 26, and 28 °C. The solid fat content was measured as a function of time and fitted to the Avrami equation. Melting point, thermal behavior, viscoelastic properties, and crystal morphology were all measured at 90 min. All assays were repeated, as well as hardness, after being stored at 5 °C for 48 hours. Samples containing PL showed slower crystallization as concentration increased especially at higher temperatures (26 and 28 °C). The addition of PL caused a difference in crystal morphology resulting in visibly larger crystals at 90 min. The elasticity and hardness at 90 min were influenced by the addition of PL at 24 °C with lower values obtained in samples with PL compared to the AMF alone. No differences in hardness nor in elasticity was observed for samples crystallized at 26 and 28 °C. A decrease in melting enthalpy was observed in samples with PL indicating a reduction in crystallization at all temperatures, which was supported by crystal morphology.

The Influence of Conditions of Secondary Propylene Recycling in the Presence of Vegetable Fillers on Thermal Properties of Polymer Composites

This article discusses the influence of conditions of secondary polypropylene recycling in the presence of vegetable fillers on thermal properties of polymer composites. Secondary polypropylene was recycled by the following methods: extrusion using two-screw extruder, agitation in mixing chamber of laboratory station (plastograph), die casting. Polymer composites on the basis of secondary polypropylene in the presence of vegetable fillers (wood dust, rice hulls, buckwheat hulls, and chaff) were produced by extrusion. Thermal properties of polymer composites were determined by thermogravimetric analysis and differential scanning calorimetry. It is established that recycling of secondary polypropylene by various methods does not change melting and crystallization points of polymer phase but is accompanied with decrease in melting enthalpy (by 9-11%) and crystallinity (by 5.6-6.5 %). The polypropylene samples obtained by recycling are characterized by lower thermal stability in air in comparison with initial polypropylene. Addition of vegetable filler to polymer composite on the basis of secondary polypropylene significantly decreases (by 1.13-1.48 times) melting enthalpy and crystallization of polymer phase. The compounds are characterized by relatively high thermal stability: their initial destruction points are close to parameters of initial polymer.

Cycling stability of d-mannitol when used as phase change material for thermal storage applications

d-Mannitol is a potential phase change material to store thermal energy for process heat applications between 120 °C and 200 °C. This study presents thermal cycling stability tests of d-mannitol and its effect on melting enthalpy. Short-term cycling tests were carried out in differential scanning calorimeter in combination with air and nitrogen/vacuum as atmosphere. Results show that melting enthalpy decreases in contact with oxygen, decreases less in vacuum and stays almost constant in nitrogen atmosphere over the performed cycles. Afterwards, a long-term cycling test in nitrogen atmosphere was performed. Here melting enthalpy decreases about 9% during 500 cycles. If this effect cannot be overcome, the material is unsuitable for most applications. Fourier-transform infrared spectroscopy was carried out to evaluate chemical stability after the cycling tests. A possible hypothesis for a degradation mechanism of d-mannitol is presented. It assumes that degradation products might be produced during thermal treatment. By additional oxidation the production of further degradation products might be triggered. It is likely that more degradation products were produced in the long-term cycling test than in the short-term cycling test in nitrogen leading to a decrease of melting enthalpy.

Effects of low molecular sugars on the retrogradation of tapioca starch gels during storage.

The effects of low molecular sugars (sucrose, glucose and trehalose) on the retrogradation of tapioca starch (TS) gels stored at 4°C for different periods were examined with different methods. Decrease in melting enthalpy (ΔHmelt) were obtained through differential scanning calorimetry analysis. Analysis of decrease in crystallization rate constant (k) and increase in semi-crystallization time (τ1/2) results obtained from retrogradation kinetics indicated that low molecular sugars could retard the retrogradation of TS gels and further revealed trehalose as the best inhibitor among the sugars used in this study. Fourier transform infrared (FTIR) analysis indicated that the intensity ratio of 1047 to 1022 cm−1 was increased with the addition of sugars in the order of trehalose > sucrose > glucose. Decrease in hardness parameters and increase in springiness parameters obtained from texture profile analysis (TPA) analysis also indicated that low molecular sugars could retard the retrogradation of TS gels. The results of FTIR and TPA showed a consistent sugar effect on starch retrogradation with those of DSC and retrogradation kinetics analysis.

Effect of sweetener combination and storage temperature on physicochemical properties of sucrose free white chocolate.

The influence of a combination of sweeteners (Stevia (St) and sucralose (Su)) and storage temperature on thermal properties, microstructure, water content, texture and Bloom of sucrose free white chocolate was investigated. A strong relationship between the microstructure and the highest percentage of Bloom was observed. The samples with 100%Su and 50%S+50%Su presented microstructures with channels through which solids and fat could more easily spread to the surface, increasing the fat and sugar Bloom formation. However, 50%St+50%Su and 75%St+25%Su samples showed a minimum Bloom formation, probably due to its dense microstructure with no void spaces. The differential scanning calorimetry studies demonstrated that the samples containing 100%St and 75%St+25%Su showed the smallest decrease of melting enthalpy with increasing temperature. Besides, non-isothermal crystallization kinetics was studied by applying Avrami model. The sample 75%St+25%Su presented the highest values of activation energy showing the greatest stability in the temperature range studied (7°C-30°C).

Melting and crystallization DSC profiles of different types of meat

The aim of this study was to test the influence of scanning rate and meat type on the thermo-physical properties of meat and content of the freezable water in frozen meat, using differential scanning calorimetry (DSC). In this study, three types of meat were investigated: beef (M. Longissimus dorsi), pork (M. Longissimus dorsi), and chicken meat (Pectoralis major). The cooling rate affected the onset (Tcon), peak (Tc) and end (Tcend) temperatures of crystallization process of beef meat (p < 0.05). Decreasing cooling rate from 20 to 2?C/min resulted in significant (p < 0.05) change of the crystallization enthalpy (?Hc) of beef meat, from -220.17 to -168.20 J/g, respectively. Reduction of the heating rate caused significant (p < 0.05) decrease in enthalpy of melting (?Hm) for beef meat, from 228.87 to 161.13 J/g. The heating rate affected the peak (Tm) and end temperatures (Tmend) of melting process of beef meat (p < 0.05). The type of meat did not have effect on ?Hc and ?Hm as well as temperature of crystallization (Tcon, Tc and Tcend) and temperature of melting (Tm and Tmend) in meat. Significant (p < 0.05) change in freezable water content were recorded between heating rate 20 ?C/min and other heating rates, for all three meat types.

Liquid–crystal equilibrium application for 2,3-DNT initial thermal decomposition analysis

2,3-Dinitrotoluene (2,3-DNT) thermal decomposition and its products were studied. Main attention was paid on the initial stage of decomposition, because the degradation of even a few percent of high energetic compound may cause significant hazard. Partial decomposition of 2,3-DNT was performed conditioning at the temperature range of 457–568 K. Impurities production at the initial stage of decomposition was determined by the analysis of melting enthalpy decrease with cryometric method. Mean self-aggregation number of the initial substance was defined and determined to estimate the molecular mass of products of 2,3-DNT thermal conditioning. MALDI TOF method was used for independent molecular mass verification. 2,3-DNT is thermally stable substance. Heating of its sample from the ambient temperature to 486 K with the heating rate of 2 K min−1 does not cause thermal decomposition. Very good reproducibility of melting process performed on the same sample was obtained. Only prolonged conditioning at raised temperature leads to initial substance loss. Two competitive reactions, aggregation and decomposition, were run during 2,3-DNT thermal conditioning. Heating with low heating rate leads to products with higher molecular masses. Two different results prove that: MALDI TOF analysis and the melting enthalpy decrease which is higher than the increase in impurities content determined with cryometric method. Mass spectrum of the thermally conditioned 2,3-DNT samples includes strong signals with (among others) following m/z values: 551, 687, 1062, 1137, 1211. Formed macromolecular compounds were stable until the temperature of 500 K.

Temporal behavior of DNA thermal stability in the presence of platinum compounds. Role of monofunctional and bifunctional adducts

Penetrating into cell nuclei, antitumor drug cisplatin sequentially forms various intermediate and final adducts destroying local DNA structure. The demonstrated disappearance of the fine structure of melting curve of long DNAs along with a strong decrease in melting enthalpy conforms to the structural impact. However, the negative thermal effect (δTm) caused by cisplatin is relatively small if neutral medium is used in melting experiments. Cisplatin's inactive analogs transplatin and diethylenetriaminechloroplatinum {Pt[(dien)Cl]Cl} also distort DNA structure but their thermal effect is even positive. We have found that the use of alkaline medium in melting experiments strengthens the negative thermal effect for cisplatin. For transplatin and Pt[(dien)Cl]Cl, the thermal effect becomes negative that makes it qualitatively consistent with structural distortions. Those changes are explained by elimination of nonspecific electrostatic stabilization of DNA under platination. Additionally, alkaline medium fixes intermediate states of DNA platination and makes them stable against heating. These results allowed us to monitor δTm under binding of platinum compounds to DNA and their further transformation. The kinetic and thermal characteristics of monofunctional and bifunctional adducts were evaluated. It has been demonstrated that monofunctional adducts of cisplatin, transplatin and Pt[(dien)Cl]Cl produce approximately the same thermal destabilization. Cisplatin intrastrand crosslinks cause a two-fold stronger thermal destabilization than its monofunctional adducts. The value of δTm for cisplatin's final adducts is ten times larger than for transplatin. This difference mainly comes from the much stronger thermal destabilizing power of cisplatin's intrastrand crosslinks, which are responsible for antitumor activity of this compound.

Effect of high‐pressure microfluidization on the structure of cassava starch granule

AbstractMicrofluidization has been applied to modify starch granules. The study was conducted to investigate the effect of microfluidization on the structure and thermal properties of cassava starch–water suspension (20% w/w). The means of optical microscopy, SEM, FTIR spectroscopy, XRD, and DSC were applied to analyze the changes in microstructure, crystallinity, and thermal property. Microscopy observations revealed that native starch granules were oval, round, and truncated in shape. After the microfluidization treatment, a bigger starch granule was partially gelatinized, and a gel‐like structure was formed on a granular surface. No significant difference in XRD patterns of the samples were observed and all samples exhibited A‐type allomorph. Crystallinity decreased with the pressure. Sample treated at 150 MPa contains 17.1% crystalline glucan polymer, lower than that of native granules which have crystallinity of about 25.8%. A lower crystallinity means poor order of crystalline glucan polymer structure in starch granules. The disruption of crystalline order within the granule was also observed by FTIR measurement. Thermal analysis using DSC indicated that the microfluidization treatment brought about a significant decrease of melting enthalpy. The gelatinization enthalpy was 12.0 and 3.0 J/g for the native sample and samples treated under the 150 MPa, respectively. The results indicate that high‐pressure microfluidization process induced the gelatinization of cassava starch, which is evaluated by a percentage of the degree of gelatinization, due to a pronounced decrease with increasing microfluidizing pressure.

PHYSICOCHEMICAL CHARACTERISTICS OF BINARY MIXTURES OF HYDROGENATED PALM KERNEL OIL AND GOAT MILK FAT

ABSTRACT The changes in physicochemical characteristics of fat blends containing hydrogenated palm kernel oil (HPKO) and goat milk fat (GMF), before and after chemical interesterification using sodium methoxide as catalyst, was evaluated. HPKO : GMF blends were prepared in six ratios: 100:0, 80:20, 60:40, 40:60, 20:80 and 0:100 (w/w). Melting characteristics were studied by differential scanning calorimetry. Peak melting temperatures (Tp) of noninteresterified blends decreased as the percentage of GMF increased. Generally, the interesterified blends showed lower Tpvalues compared to the noninteresterified blends at their respective blending ratios. Decrease in melting enthalpy (Ep) occurred with the increase in percentage GMF in the blends for both the noninteresterified and interesterified blends. Interesterified blends had greater Epvalues than those of the noninteresterified blends at respective ratios. Results from X‐ray diffraction analysis showed that all blends possessed a β′ polymorph. HPKO : GMF (0:100) was the only blend in which the presence of both β′ and β polymorphs was detected. Chemical interesterification had no effect on polymorphic crystal behavior. Based on solid fat content (SFC) results, eutectic effect did not occur in all HPKO : GMF blends studied. It was shown that the percentage of SFC decreased as percentage of GMF increased. Decrease in percentage SFC of blends was brought about by interesterification. The HPKO : GMF (100:0) blend had the highest percentage of free fatty acid followed by HPKO : GMF (0:100). Interesterification caused a 2‐ to 3‐fold increase in the percentage of free fatty acids compared to noninteresterified blends. Iodine values of the blends increased with an increase in GMF proportion. A rapid increase in iodine was observed in blends containing 0–20% GMF. Interesterification did not have any effect on the iodine value of fat blends.

Calorimetric study of fluorinated methacrylic and vinyl polymer blends: part 2: correlation between miscibility, chemical structure and χ12 interaction parameter in binary systems

The miscibility of poly(methylmethacrylate) (PMMA) and (trifluoroethyl methacrylic ester–MMA) copolymers (MMA–MATRIFE) with poly(vinylidene fluoride) (PVDF) and VDF copolymers was studied by differential scanning calorimetry (DSC) as a function of the fluorinated copolymer crystallinity and fluoroalkyl methacrylic ester content in the methacrylic copolymer. Miscibility limits were found identical whatever be the blend preparation technique, although solution mixing induced some polymer fractionation, thus giving slightly higher blend glass transition temperature. The miscibility domain widths are reduced when using MMA–MATRIFE copolymers as compared to PMMA-containing blends and miscibility limits are dependent on the MATRIFE content in the methacrylic copolymer. Moreover, PVDF or VDF copolymer melting enthalpy decrease is associated to a partial dissolution of the semi-crystalline polymer in PMMA or MMA–MATRIFE copolymer above the total miscibility limit. The evolution of dynamic moduli as a function of blends composition confirms the miscibility limits determined by DSC. The Flory–Huggins interaction parameters were determined through the melting point depression analysis and compared to correlate the intensity of inter- or intra-molecular interactions between the polymers to the postulated ‘acidity’ of hydrogen atoms in various VDF-containing polymers. The interaction parameter χ12 increases with the fluoroalkyl methacrylic ester content, corresponding to a prevalence of intra-molecular on inter-molecular interactions in these blends. Similarly, PVDF offers higher χ12 values as compared to VDF–TFE or particularly to VDF–TrFE copolymers. These results highlight the importance of the nature of fluorinated polymers and of the inter- or intra-molecular character of dipolar interactions on both, copolymer miscibility and interaction parameter values.