Synthesis and physical properties of H12MDI-based polyurethane resins

This paper described the synthesis of four types of polyurethanes by using diisocyanato dicyclohexylmethane (H₁₂MDI) as the hard segment and poly hexamethylene carbonate diol, polybutylene adipate diol, poly(hexamethylene diol/neopentyl glycol)-based copolyester diol, or poly hexamethylene diol/hexamethylene carbonate)-based copolyester/carbonate diol as the corresponding soft segment. The spectral analysis, thermal studies (differential scanning calorimetry and dynamic mechanical analysis), tensile strength-elongation relationship, and water vapor permeability of these samples were investigated. The results of these studies showed that the phase separation extent of the four types of polyurethanes displayed the following order: ESBA (polybutylene adipate-based polyurethane) > ECHH (co-polyester / carbonate-based polyurethane) > ESHN (copolyester diol-based polyurethane) > CAHC (polyhexamethylene carbonate-based polyurethane). The water vapor permeability of the cast films increased with the increase of the phase separation extent, in which the polyester-based polyurethane (sample ESBA) displayed the highest water vapor permeability. In terms of tensile strength-elongation property, the polycarbonate diol based polyurethane displayed higher tensile strength but lower elongation than polyester-based polyurethanes.     

水蒸气透过率、透过量与透过系数的应用

详细介绍了3项透湿性参数——水蒸气透过率、透过量和透过系数的定义、应用范围以及相互之间的差异和换算关系,同时对于目前国际国内标准中定义不清晰的情况给予了说明。     

Effect of addition of polyethylene glycol on the moisture transfer and waterproof properties of foam-finished nylon fabrics

The effects of the addition of polyethylene glycol (PEG) within the coated film on the water vapor permeability and waterproof properties of the foam-coated fabrics were investigated. Foaming solutions added with PEG had lower surface tension than those without, and the viscosity and stability of the foaming solution varied with PEG of different molecular weight. When PEG is of 1,000 daltons (PEG 1000), the viscosity and stability of the foaming solution was the highest among molecular weights ranging from 400 to 16,000, whereas the surface tension was the lowest. The stability would rise proportionally with viscosity if the viscosity of the foaming solution is between 13,610 cps and 13,960 cps. When PEG 1000 was added, the particle size of the foaming solution was smaller, followed by PEG 600. But when PEG 4000 or ethylene glycol (EG) was added, the particle size was bigger. The introduction of PEG 1000 to the foaming solution produced better water vapor permeability and waterproof properties. Fabrics coated with foaming solution, to which PEG 1000 was added, had smaller and more micropores in the coated film. Coated film without the addition of PEG had less micropores, and that with the addition of EG or PEG 4000 had large pores with non-homogenous pore sizes. These results were confirmed by SEM observation.     

Edible starch sodium octenyl succinate film formation and its physical properties

Edible starch sodium octenyl succinate (SSOS) films, with or without glycerol as plasticizer, were prepared by solution‐casting method. The effect of SSOS concentration, degree of substitution (DS) of octenyl group, as well as glycerol content, on the properties of SSOS films was studied including tensile strength, water vapor permeability (WVP), and oil permeability (OP). The results indicated that the tensile strength of SSOS film was up to 39.4 ± 1.9 MPa when the concentration of SSOS was 0.05 g/mL and DS was 0.05. The increase of glycerol content resulted in a decrease of film tensile strength. WVP of SSOS films was relatively low. Meanwhile, study in OP showed that SSOS films were oilproof. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Barrier and mechanical properties of carrot puree films

The edible films based on carrot puree, carboxylmethyl cellulose (CMC), corn starch and gelatin were developed. Glycerol was added as plasticizer. Hydrocolloids and plasticizer content effects on film properties were investigated. CMC and gelatin contents did not significantly affect film %elongation (%E), oxygen permeability (OP) and water vapor permeability (WVP) but significantly enhanced film tensile strength (TS). Corn starch content significantly enhanced film TS and WVP but not significantly affected film %E and OP. Increasing glycerol content decreased film TS and increased film %E (p < 0.05), OP and WVP. Moreover, the L, a and b values of carrot films increased with the increase of the glycerol and decreased with the increase of the corn starch.     

Influence of preparation conditions on the physical properties of zein films

Zein is a hydrophobic protein produced from maize. Biodegradable zein films without additional reagents were prepared using various controlled drying conditions. The zein films were transparent. Mechanical properties (tensile strength and puncture strength), gas permeability, and water vapor permeability (WVP) of the zein films were measured. The tensile strengths of the zein films were between 7 and 30 MPa and the puncture strengths between 37 and 191 MPa. The zein films had higher oxygen permeability than carbon dioxide permeability. The lowest WVP of the zein film was 0.012×10⁻⁹ g·m/m²·s·Pa. We found differences in the WVP between the sides of the zein films; i.e., the air side of the zein film had a higher WVP than the basal side of the zein film when the films were exposed to high humidity during testing. This indicates a relationship between the WVP of the zein film and the contact angle of the zein film. The mechanical properties of the zein film depended on the drying conditions during preparation. Zein films with various useful physical mechanical properties were produced.     

Physical and functional characterization of PHASCL membranes

Dense semicrystalline membranes of polyhydroxyalkanoates with medium change length (PHA_SCL), polyhydroxybutyrate (PHB) and poly β (hydroxybutyrate-co-hydroxyvalerate) [P(βHB-co-XβHV)] were characterized using wide-angle X-ray (WAXS) and scanning electron microscopy. PHB membranes showed a more rugged surface than those of copolymers (0-22%HV). Properties such as swelling capacity, vapor permeability and selectivity were investigated. Swelling percentage in water-ethanol mixtures was 34% for PHB as compared to 14% for copolymers membranes. The ethanol/water selectivity (α_s) of PHB was 5.8 which shows that it is more selective than copolymers.The water vapor and ethanol vapor permeability were determined by a gravimetric technique at different temperatures by static and dynamic methods. PHB permeability was 69.5 Barrer at 30 °C and a discreet increment was observed at temperatures (30-50 °C). The difference in permeability between PHB and [P(βHB-co-X%βHV)] could be interpreted in terms of the crystallization rate, crystallite size and distribution which impact to transport properties of amorphous phase.     

Effects of Lipid Structure Changed by Interesterification on Melting Property and Lipemia

Interesterification or the randomization reaction changes fatty acid positional distribution and solid fat content of fats, which may consequently affect fat absorption and metabolism. It is well established that saturated fatty acids in the sn‐2 position of triacylglycerols (TAG) have better digestibility and lower postprandial chylomicron clearance compared to those in the sn‐1,3 positions in animal experiments. TAG structure is also shown to affect fasting lipid level and atherosclerosis in animals, but fat interesterification it has been shown to not affect fasting lipid level in human adults. However, its effect on postprandial responses is controversial. In this review, the complex results of studies of interesterification and lipemia were briefly discussed. More importantly, the confounding of two factors that are both changed by interesterification, TAG structure and solid fat content as the main limitation on understanding how interesterification affects lipemia is emphasized. Separation of the two factors is possible using paired fats as demonstrated. This paper also discusses some intriguing effects of fats having saturated fatty acids in the sn‐2 position and the need for future research.     

Effect of emulsion temperature on physical properties of palm oil-based margarine

Margarines made from refined, bleached, and deodorized palm oil at different emulsion temperatures showed no significant difference in their consistency, polymorphic behavior, and solid fat content (SFC) during storage, although differences were observed during processing. The emulsion temperatures studied were 40, 45, and 50°C, with other parameters such as emulsion flow rates, tube cooler temperature, and pin rotor speed kept constant. The SFC developed during processing and storage at 28°C was measured to evaluate the quality of margarine. The emulsion contained no SFC at any emulsion temperature studied. However, the amount of SFC in the perfector or tube cooler unit increased to 15.9, 13.9, and 15.6% in margarine produced at emulsion temperatures of 40, 45, and 50°C, respectively. At 40°C, the lowest SFC was developed during storage even though this margarine had the highest consistency. The softening point of this sample was moderately high and closely related to the type of crystal developed, which was a mixture of β′ and β crystals. Emulsion at 45°C gave the most stable margarine consistency and SFC with crystal in the β′ form even after the fourth week. At 50°C, moderately soft product was produced, which might be undesirable for some applications, although the crystals were in the β′ form.     

Relationship between the physical properties of butter and water loss during lamination

Butter provides ideal flavor and texture in laminated pastries. During industrial production of butter for pastries, the butter structure can break due to shear forces during lamination resulting in water loss (WL). This WL in during lamination can affect the desired qualities of the pastry. There is a need to unveil the physical properties that drive WL in butter processing. The objective of this study was to characterize the physical properties of seven commercial butter products and correlate these properties to WL during processing. The physical properties evaluated included solid fat content (SFC), water content, water droplet size, viscoelastic behavior, melting profile, hardness, and WL. Water content is the only characteristic that was significantly correlated to WL. Regression analysis showed that an increase in water content, high melting fraction enthalpy, and water droplet size, and a decrease in the viscoelastic phase shift angle increased WL. Correlation analysis was also performed in high fat content butter (>83% butterfat) and regular fat content butter (<83% butterfat) separately. The WL in high fat butters had significant negative correlations with G′ and G″ and significant positive correlations with SFC at 5, 10, and 15°C (α = 0.05). The WL of regular fat butters had significant positive correlations with hardness, water droplet size, and SFC at 30°C (α = 0.05). No other significant correlations were identified with WL in these two groups. Overall, these results show that various physical properties can affect butter quality for lamination purposes including water content, water droplet size, viscoelasticity, and melting behavior.     

Influence of sorghum wax,glycerin, and sorbitol on physical properties of soy protein isolate films

Sorghum wax, sorbitol, glycerin, and soy protein isolate (SPI) composite films were prepared. Effects of sorghum wax, sorbitol, and glycerin concentrations on various films were evaluated using response surface methodology. All independent variables significantly (P<0.05) affected film water vapor permeability (WVP), tensile strength (TS), elongation at break (E), total color difference, and total soluble matter (TSM). Increasing the sorghum wax concentration decreased WVP and E. As sorbitol content increased in the composite films, WVP and TS increased. Sorbitol had a critical point of 2–5 g/5 g SPI for low values of TSM. The addition of sorbitol contributed more to the properties of the film than did glycerin.     

Analysis of Moisture Content and Density of Pears During Drying

Solar dried pears of the “S. Bartolomeu” variety are a very much appreciated and preferred dried food product in Portugal. Nevertheless, the traditional solar drying is carried out at open air during the months of 07 and 08, and this nowadays is a disadvantage for larger productions. This work is to evaluate the possibility of producing dried pears from this and other varieties, maintaining the characteristics of the traditional dried pears. In this study four different types of pears were studied, including “S. Bartolomeu” as a basis for comparison and the drying method employed was the traditional one. From the results it was concluded that, although the behaviour of the four varieties do not vary significantly, one particular variety (“D. Joaquina”) is a good alternative to the “S. Bartolomeu” pear.     

Analysis of Moisture Content and Density of Pears During Drying

Abstract

Solar dried pears of the “S. Bartolomeu” variety are a very much appreciated and preferred dried food product in Portugal. Nevertheless, the traditional solar drying is carried out at open air during the months of 07 and 08, and this nowadays is a disadvantage for larger productions. This work is to evaluate the possibility of producing dried pears from this and other varieties, maintaining the characteristics of the traditional dried pears. In this study four different types of pears were studied, including “S. Bartolomeu” as a basis for comparison and the drying method employed was the traditional one. From the results it was concluded that, although the behaviour of the four varieties do not vary significantly, one particular variety (“D. Joaquina”) is a good alternative to the “S. Bartolomeu” pear.     

Preparation and properties of sulfopropyl chitosan derivatives with various sulfonation degree

In this investigation, chitosan (CS) is modified by propane sultone via a sulfonation reaction to create various degrees of sulfonation. The sulfonated chitosan (SCS) has a pendant alkyl sulfonic group dangling at the side chain, which can improve its hydrophilicity and water solubility. Elemental analysis, Fourier transform infrared spectroscopy (FTIR) and ¹³C nuclear magnetic resonance (¹³C NMR) were applied to identify the structure by determining the distribution of the substituents in the product. The degree of sulfonation in the SCS can be controlled and the hydrogen bonding interaction can be reduced by varying the degree of sulfonation. A solubility test proved that solubility increased with degree of substitution at over a wide range of pH values. X‐ray diffraction patterns of SCS samples demonstrated that the crystallinity declined as the degree of sulfonation increased. Thermogravimetric analysis and modulated differential scanning calorimetry (MDSC) results indicated that thermal stability fell but water absorbance increased with the degree of sulfonation. More water‐soluble SCS is thus obtained. The controllable different sulfonation degree of the CS polymer suggests new possibilities for the application of CS‐based materials. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of processing conditions on physical properties of a milk fat model system: Rheology

The effect of processing conditions on rheological behavior of three blends of 30, 40, and 50% of high-melting fraction [melting point measured as Mettler dropping point (MDP)=47.5°C] in low-melting fraction (MDP=16.5°C) of milk fat was studied. The effects of cooling and agitation rates, crystallization temperature, chemical composition of the blends, and time of storage on complex, storage and loss moduli were investigated by dynamic mechanical analysis (DMA). Compression tests were performed on samples using frequency values within the linear viscoelastic range (1 to 10 Hz). Loss modulus was, on average, 10 times lower than elastic modulus and was generally not affected by processing conditions. Samples showed a more solid-like behavior that was better described by storage modulus. Storage modulus varied with all processing conditions used in this study, and even for the same solid fat content, different rheological properties were found. Storage and complex modulus increased with temperature of crystallization (25 to 30°C), even though solid fat contents of samples measured after 24 h at 10°C were the same. Moduli were higher for samples crystallized at slow cooling rate, decreased with agitation rate, and were lower for the 30–70% blend at all processing conditions used. Storage moduli also increased with storage time. Shear storage modulus was calculated from the DMA experimental data, and the results were in agreement with the values reported in literature for butter systems. Fractal dimensions calculated for these systems showed a significant decrease as agitation rate increased in agreement with the softening effect reported for working of butter.     

Curing and barrier properties of NBR/organo-clay nanocomposite

Organo-montmorillonite/NBR nanocomposites were prepared by a melt intercalation process. The characteristics of NBR nanocomposites were characterized by oscillating-disk rheometer, water-vapour transmission and transmission electron microscopy (TEM). Changes in cure characteristics resulting from changes in clay content and the addition of silane coupling agent were investigated. The study confirmed that organo-montmorillonite/NBR nanocomposites cure characteristics, viz minimum torque, maximum torque, scorch time and curing time, change according to the change in clay content and the addition of silane coupling agent. Of the water-vapour transport properties, the clay content and silane content are the dominating factors in determining the individual water-vapour permeability of these NBR nanocomposites. TEM analysis provided clear evidence for the homogeneous dispersion of clay in the NBR matrix without regard to increases in clay content. Copyright © 2004 Society of Chemical Industry     

Isothermal Crystallization of Palm Oil-Based Fats with and without the Addition of Essential Oils

The objective of study was to evaluate the crystallization behavior of palm oil-based fats processed with and without the addition of essential oils (5% w/w) obtained from the flowers (EsOF) and stems (EsOS) of Pituranthos scoparius. Palm oil (PO) and a mixture of PO, soybean oil, and sunflower oil (Mix) were tested. The addition of the essential oils did not change the melting points of the fats but affected their crystallization behavior. A delay in crystallization was observed, evidenced by lower crystallization rates, and lower solid fat contents. This delay was comparable in the samples crystallized with EsOF and EsOS for the PO samples but EsOF was more efficient at delaying crystallization in the Mix sample. EsOF generated a less organized crystalline network in both samples (lower enthalpy values) while EsOS generated a more organized crystalline network (high enthalpy values) when used in the Mix sample. The addition of EsO also affected the crystal microstructure in some cases. While a slight increase in crystal size was observed for some PO samples crystallized with EsOF, no change or a decrease in crystal size was observed for the samples crystallized with EsOS. A slight decrease in crystal size was observed for Mix samples crystallized with EsOF while no effect was observed for these samples crystallized with EsOS. Results from this study show that these essential oils can be used as natural additives to modify the crystallization of fats for food applications and therefore widen their functional properties.     

Influence of Drying Techniques on the Characteristics of Chitosan and the Quality of Biopolymer Films

In this work, spouted bed and tray-drying techniques were employed at different drying air temperatures to produce dried chitosan, and the chitosan powder was used to produce biofilms. The products obtained from each drying technique were compared in relation to quality aspects (molecular weight, lightness, and hue angle). The results found for chitosan in spouted bed drying (90°C) showed lower alteration and best quality aspects in relation to the chitosan powder. However, in tray drying under the best condition (60°C) the chitosan molecular weight increased about 50% in relation to the initial value and browning was observed. The biofilms produced from chitosan dried in the spouted bed showed the best mechanical properties (tensile strength of 42 MPa and elongation of 29%) and lower water vapor permeability (3.95 g mm m^?2 kPa^?1 day^?1).     

Rheological and Microscopic Properties of Fat Blends with Similar Solid Fat Content but Different Trans Composition

In this study, two different groups of fat samples were prepared in a way that samples of each group had different trans fatty acid (TFA) composition but similar solid fat content (SFC). Samples of the first group (named group A) had TFA between 0.0 and 56.23 %, while the samples of the second group (group B) contained trans isomers ranging from 0.0 to 44.4 %. A polarized microscope was used to monitor the differences between the samples in terms of crystal size and crystal number during isothermal crystallization. In general, increasing TFA resulted in formation of larger crystals in a shorter time. Similar findings were also observed when small deformation time and frequency sweep experiments were conducted. A higher TFA content led to higher complex modulus values during isothermal crystallization. On the other hand, when the samples were stored at 4 °C for 48 h, the samples with the lower trans isomer had higher hardness values.