Relative Degree Of Crystallinity Research Articles

Use of asphaltene filler to improve low-density polyethylene properties

ABSTRACTAsphaltene filled LDPE composite were prepared and characterized. The composites were studied to determine the reinforcement imparted by the asphaltene on the durability of LDPE polymer. The study showed that the composites have higher melting and crystalline behavior, delays the degradation induced by heat and acts as a thermal barrier limiting the emission of the gaseous degradation products, resulting in an increase in the thermal stability of the composites, higher tensile strength, have higher values of the storage and loss modulus. 5 wt% of asphaltenes added in the LDPE afforded the best dispersion in the polymeric matrix, larger crystallite size, enhanced thermal stability, highest relative degree of crystallinity and improved mechanical tensile or thermo-mechanical properties.

The influence of bamboo fiber content on the non-isothermal crystallization kinetics of bamboo fiber-reinforced polypropylene composites (BPCs)

Abstract Bamboo fiber (BF)-reinforced polypropylene (PP) composites (BPCs) have been investigated and it was shown by differential scanning calorimetry (DSC) that BF is a nucleation agent and accelerates the crystallization rate of the PP matrix. Numerical analyses according to Avrami, Avrami-Ozawa, and Friedman described well the nucleation mechanism, the crystallization rate and the activation energy for the non-isothermal crystallization behavior of BPCs, respectively. The Avrami approach indicated that BF as a reinforcement significantly changed the crystal growth mechanism of PP matrix during the cooling process. Based on the Avrami-Ozawa method, a lower cooling rate can achieve a certain relative crystallinity degree within a time period. According to the Friedman method, the activation energies of BPCs were lower than that of neat PP below a relative crystallinity of 35%, when the BF content was more than 60%.

The potential of synergism between ultrasonic energy and Soluplus® as a tool for solubilization and dissolution enhancement of a poorly water soluble drug. A statistically based process optimization

The present study was a trial to improve the solubility and dissolution of a model poorly water soluble drug, nimesulide, through a combined technique of ultrasonic exposure with a surfactant treatment. A 23 full factorial design was applied to study the effect of varying the drug concentration, the solvent: anti-solvent ratio and the ultrasonication time on the % yield, saturated solubility and particle size of the produced sonocrystals either plain or combined with 0.025% Soluplus®. Optimized formulae were subjected to particle crystallinity and dissolution studies. Differential scanning colorimetry showed a successive lowering in the Δ H value from −25.41 J/g for the drug to −22.79 J/g for F5 and -16.7 J/g for F5+ 0.025% Soluplus® which possessed the most favorable heat of solution. X ray diffractometry showed that optimized sonocrystals acquired lower relative degree of crystallinity than untreated particles; however the addition of surfactant restored the original degree of drug crystallinity. Ultrasonic energy increased the rate of drug dissolution through a hastening in the value of t1/2 from 236, to 151 and 88.5 min for plain drug, F5 and F5 with 0.025% Soluplus® respectively. Therefore, subjecting the drug to ultrasound energy assisted with amphiphilic surfactant proved to be a simple and promising technique to treat drug insolubility.

Effect of Grinder Pretreatment for Easy Disintegration of Chitin into Nanofiber

Chitin nanofibers were prepared by grinder pretreatments and subsequent mechanical treatment using a high-pressure water-jet (HPWJ) system. From SEM observations, grinder pretreatment improved disintegration efficiency in subsequent HPWJ treatment. That is, with pretreatment, excellent nanofiber networks were observed after a single HPWJ treatment, and sufficient nano-fibrillation was accomplished with 5 cycles of HPWJ treatments. The characteristic crystalline structure of α-chitin and degree of relative crystallinity were maintained after a series of mechanical treatments. From UV-Vis spectra, grinder pretreatment improved transparency of chitin nanofiber slurry, indicating the pretreatment facilitated subsequent HPWJ mechanical disintegration. Viscosities of chitin nanofiber slurry also showed that the grinder pretreatment and HPWJ treatment disintegrated the chitin into nanofiber very well. However, excessive HPWJ treatment decreased nano-fiber length, resulting in lower viscosity.

Influence of particle size of isotactic polypropylene (iPP) on barrier property against agglomeration of homogenized microcrystalline cellulose (HMCC) in iPP/HMCC composites

AbstractIsotactic polypropylene (iPP) powders were treated by a colloid mill for different times to obtain a series of particle sizes ranging from 682 μm to 89 μm. The relative crystallinity degree index (Xc, %) calculated by X-ray diffraction, and the initial degradation temperature measured by thermogravimetry, were all reduced after the milling process, which revealed that the structure of iPP molecular chains was destroyed during the powerful shearing and friction action. Furthermore, the increasing melt flow rate (MFR) index indicated that the molecular weight of iPP had reduced during the mechanical treatment. Scanning electron micrographs showed the inevitable agglomeration of homogenized microcrystalline cellulose (HMCC) fibers after being dried directly without iPP powders. However, the addition of achieved superfine iPP powders presented a good barrier property against the agglomeration phenomenon and consequent improvement in mechanical performance of the iPP/HMCC composites.

Effect of Ti–SiO2 nanoparticles on non-isothermal crystallization of polyphenylene sulfide fibers

Systematic studies of non-isothermal crystallization kinetics of polyphenylene sulfide (PPS) and PPS/Ti–SiO2 (1.0, 3.0 and 5.0 mass%) fibers raw materials were performed by DSC combining with SEM and polarized optical microscopy (POM). There are significant dependence of non-isothermal crystallization behavior and kinetics of PPS/Ti–SiO2 nanocomposites on the Ti–SiO2 content and cooling rate. Nano Ti–SiO2 acted as nucleating agents. Not only initial crystallization temperature was increased but also the rates of crystallization accelerated by analyzing relative degree of crystallinity, crystallization rate coefficient and crystallization rate parameter. Combining with POM images, non-isothermal crystallization kinetics was studied by Jeziorny, Ozawa and Mo’s equation. Spherulitic morphology of PPS has not been changed by nano Ti–SiO2, but the numbers of initial crystal nucleus increased and spherulitic size became smaller. Crystallization activation energy of PPS and PPS/Ti–SiO2 nanocomposites was estimated using isoconversional analysis of calorimetric data and proved that Ti–SiO2 increased effective energy barrier of crystallization due to its strong surface adsorption and the crystallization of PPS/Ti–SiO2 was more sensitive to temperature.

Enhancement of the functional properties of Dioscoreaceas native starches: Mixture as a green modification process

To study the effect of the mixing, three types of starch from Dioscorea sp., Dioscorea piperifolia Humb. var. Wild. and Dioscorea Trífida tubers were mixed in different proportions and their thermal, structural and rheological properties were characterised. Using thermogravimetric (TG) and differential thermal analysis (DTA) it was found that all the mixed samples presented enhanced thermal stability. By differential scanning calorimetry (DSC) and viscoamylograph (RVA) techniques it was verified that the amylose content from the D. sp. starch influenced the gelatinisation and paste properties of the mixed samples. Furthermore, using scanning electron micrograph (SEM) analysis it was possible to suggest a correlation between the size of the starch granules and their relative degree of crystallinity, which was calculated by the X-ray diffraction (XRD) patterns. The colour analysis revealed that, irrespective of the proportion, the strong tendency to yellow of the native Dioscorea piperifolia predominated in the mixed samples.

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. We report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Furthermore we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.

Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics

The morphological structure of poly(3-hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin-casting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side-chain stacking, π–π stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLE-deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin-casting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in-plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin-cast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 39–48

Physicochemical properties of maca starch

Maca (Lepidium meyenii Walpers) is gaining research attention due to its unique bioactive properties. Starch is a major component of maca roots, thus representing a novel starch source. In this study, the properties of three maca starches (yellow, purple and black) were compared with commercially maize, cassava, and potato starches. The starch granule sizes ranged from 9.0 to 9.6μm, and the granules were irregularly oval. All the maca starches presented B-type X-ray diffraction patterns, with the relative degree of crystallinity ranging from 22.2 to 24.3%. The apparent amylose contents ranged from 21.0 to 21.3%. The onset gelatinization temperatures ranged from 47.1 to 47.5°C as indicated by differential scanning calorimetry. Significant differences were observed in the pasting properties and textural parameters among all of the studied starches. These characteristics suggest the utility of native maca starch in products subjected to low temperatures during food processing and other industrial applications.

Pilot scale production and in vitro gastro-small intestinal digestion of self-assembled recrystallised starch (SARS) structures

Two commercial maize starches (Hylon VII, HA7; and normal maize starch, MS) and a potato starch were processed in the presence of palmitic acid (C16:0, Palm) at 140 °C followed by retrogradation in order to produce self-assembled recrystallised starches (SARS). The new starch structures prepared from HA7 exhibited a stronger birefringence pattern under polarised light and greater relative crystallinity (%) than those prepared from potato and normal MS. Also, the SARS from HA7 showed a typical Vh pattern (2Ө: 8.5°, 15°, 23°) confirming a strong inclusion complexation between amylose and fatty acid. Effect of other fatty acids (stearic, C18:0 and oleic, C18:1) on SARS formation was also studied using HA7. The degree of relative crystallinity (%) of these samples showed an order of palmitic > oleic > stearic, with the former also showing greater yield (YSARS). The transition temperatures and enthalpies of melting or dissolution for SARS prepared from HA7 and three fatty acids (further referred to as HA7-SARS) ranged between 101 and 131 °C and 11–18jg−1, respectively. The scanning electron micrographs of the freeze-dried HA7-SARS showed the presence of aggregated round and disc/torus shaped morphologies in varying amounts. An in vitro starch digestion model was used to study the kinetics of glucose release during digestion of ground and cooked HA7-SARS for 120 min. All the HA7-SARS samples exhibited slower and significantly lower overall starch hydrolysis than the native HA7 starch (70%), with the SARS prepared using palmitic acid showing the lowest hydrolysis (44%). Digesta from the latter also showed the presence of intact microparticles resistant to gastro-small intestinal digestion.

Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers: Effect of sebacic acid as a third comonomer

Abstract Nylon 10T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry (DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10T at a given temperature or relative crystallinity degree, which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope (POM) and X-ray diffraction (XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10T, the crystallization rate was increased with the addition of the sebacic acid comonomer.

The Effect of Montmorillonite Modification on Crystallization Behaviour of Polypropylene/Montmorillonite Composites

This paper reports the preparation of organic montmorillonite (OMMT) modified by octadecylamine and polypropylene/montmorillonite (PP/MMT) composites produced by the method of melt compounding. The effect of MMT modification degree on the crystallization behaviour of PP was emphasized by X-ray diffraction (XRD), polarizing optical microscopy and differential scanning calorimetry (DSC). Interlayer d-spacings of 3.02 nm, 1.27 nm and 2.59 nm were detected for MMT modified by octadecylamine, Titivate coupling agent and commercial OMMT, respectively. The spherulite size and the crystallinity of the composite decreased and the number of spherulites increased with the interlayer spacing of OMMT. The values of t1/2 and F(T) for PP crystallisation decreased with the interlayer spacing at a given cooling rate or a given relative crystallinity degree, indicating that MMT with a larger gallery height could accelerate the crystallization rate of PP more efficiently. Moreover, the composites containing OMMT modified by octadecylamine exhibited better mechanical properties in comparison to those incorporating OMMT modified by Titivate coupling agent and commercial OMMT, indicating that primary amine was one of the best potential surfactants for MMT modification. It was concluded that full modification of OMMT by octadecylamine was more beneficial to the crystallization of PP and hence caused a positive effect on the mechanical properties of the composites.

Influence of mannitol concentration on the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol

Mannitol is a pharmaceutical excipient that is receiving increased popularity in solid dosage forms. The aim of this study was to provide comparative evaluation on the effect of mannitol concentration on the physicochemical, mechanical, and pharmaceutical properties of lyophilised mannitol. The results showed that the physicochemical, mechanical and pharmaceutical properties of lyophilised mannitol powders are strong functions of mannitol concentration. By decreasing mannitol concentration, the true density, bulk density, cohesivity, flowability, netcharge-to-mass ratio, and relative degree of crystallinity of LM were decreased, whereas the breakability, size distribution, and size homogeneity of lyophilised mannitol particles were increased. The mechanical properties of lyophilised mannitol tablets improved with decreasing mannitol concentration. The use of lyophilised mannitol has profoundly improved the dissolution rate of indomethacin from tablets in comparison to commercial mannitol. This improvement exhibited an increasing trend with decreasing mannitol concentration. In conclusion, mannitols lyophilised from lower concentrations are more desirable in tableting than mannitols from higher concentrations due to their better mechanical and dissolution properties.

Plantain‐starch: Microstructural, physicochemical, and morphological characteristics of two cultivars grown in Malaysia

Starches isolated from mature green “Nangka” and “Tanduk” plantain (Musa paradisiaca L) cultivars grown in Malaysia were appraised for their morphological, physicochemical, and structural properties. The amylose contents of “Nangka” and “Tanduk” starches were 31.79 and 26.08% and the degree of relative crystallinity were 62.1 and 52.1%, respectively. Both cultivar starches presented an A‐type diffraction pattern, which has rarely been reported for banana starches. Gelatinization temperatures evaluated by differential scanning calorimeter were higher for “Tanduk” starch than “Nangka” starch. The scanning electron micrograph of “Nangka” starch granules was larger than “Tanduk” starch with an average particle size of 38.77 and 23.91 μm, respectively. In addition, “Nangka” starch produced lower molar mass (Mw) and gyration radius (RG) compared to “Tanduk” starch.

Crystallization behaviors of poly(vinylidene fluoride) and poly(methyl methacrylate)-block-poly(2-vinyl pyridine) block copolymer blends

In this study, blends of poly(vinylidene fluoride) and different contents of poly(methyl methacrylate)-block-poly(2-vinyl pyridine) block copolymer (BCP) (PMMA-b-P2VP) are prepared by solution mixing. The phase separation and crystallization behaviors of PVDF and PMMA-b-P2VP blends were characterized by X-ray scattering from small angle to wide angle at different annealing temperatures. The non-isothermal crystallization kinetics of the blends is investigated by differential scanning calorimetry (DSC). During the non-isothermal cooling process, PVDF in blends has higher onset crystallization temperature than that of pure PVDF, which may be attributed to a weak phase separation seen from X-ray scattering patterns, in favor of the nucleation of PVDF. A unique crystallization behavior in DSC test is that as the PVDF content in the blends is dispersed as 30 mass%, degree of crystallinity turns out to be the highest among the blends, even higher than PVDF itself, although the crystallization rate is decreasing with the BCP content. By a novel treatment of dividing the X t ~ t plot to three stages, it can be found that the relative degree of crystallinity at the end of nucleation process can be responsible for the unusual crystallization behavior. Incorporation of BCP definitely increases the hydrophilic property of PVDF materials by water contact angle test. Understanding of PVDF crystallization in the system with BCP guides the further development of high-performance PVDF membrane materials.

Isothermal and nonisothermal crystallization kinetics of bio-sourced nylon 69

Bio-sourced nylon 69, one of promising engineering plastics, has a great potential in developing sustainable technology and various commercial applications. Isothermal and nonisothermal crystallization kinetics of nylon 69 is a base to optimize the process conditions and establish the structure–property correlations for nylon 69, and it is also highly beneficial for successful applications of nylon products in industry. Isothermal and nonisothermal crystallization kinetics has been investigated by differential scanning calorimetry for nylon 69, bio-sourced even–odd nylon. The isothermal crystallization kinetics has been analyzed by the Avrami equation, the calculated Avrami exponent at various crystallization temperatures falls into the range of 2.28 and 2.86. In addition, the Avrami equation modified by Jeziorny and the equation suggested by Mo have been adopted to study the nonisothermal crystallization. The activation energies for isothermal and nonisothermal crystallization have also been determined. The study demonstrates that the crystallization model of nylon 69 might be a two-dimensional (circular) growth at both isothermal and nonisothermal crystallization conditions. Furthermore, the value of the crystallization rate parameter (K) decreases significantly but the crystallization half-time (t1/2) increases with the increase of the isothermal crystallization temperature. To nonisothermal crystallization, the crystallization rate increases as the cooling rate increases according to the analysis of Jeziorny's theory. The results of Mo's theory suggest that a faster cooling rate is required to reach a higher relative degree of crystallinity in a unit of time, and crystallization rate decreases when the relative degree of crystallinity increases at nonisothermal crystallization conditions.

Structural characteristics and rheological properties of plasma-treated starch

Abstract Corn starch was treated by a dielectric barrier discharge plasma, and the changes in the granule morphology, crystalline structure, and molecular structure, as well as the rheological properties, were investigated using diverse techniques. Dielectric barrier discharge plasma could change not only the granule surface but also the internal structures of the starch granule through its pinholes. Specifically, after the plasma treatment, as the pinhole diameter increased, the relative degree of crystallinity decreased, accompanied by molecular chain oxidation, i.e., the generation of carboxyl groups, and degradation, i.e., molecular weight reduction. Therefore, the rheological behavior changed from pseudo-plastic to Newtonian with a decrease in the paste viscosity. The results indicate that dielectric barrier plasma could be used to produce modified starch with low viscosity at a high concentration for food and non-food applications. Industrial relevance As an eco-friendly and non-thermal physical technique, dielectric barrier discharge plasma has attracted great attention in polymer modification due to the interest in reducing generated wastes during modification and producing polymer products with high safety. Starch is traditionally a main material for foods and has been widely used in food and non-food industries. For improving the properties of starch and thus widening its industrial applications using a specific technique, it is indispensible to understand how the technique affects starch's structure and property. The present work revealed that not only was the surface of starch granules altered by the dielectric barrier discharge plasma but also the internal structure was affected, since the pinholes promoted the penetration of the plasma into granule interior. In particular, along with a reduced degree of crystallinity, molecular chain oxidation and degradation occurred, as confirmed by the generation of carboxyl groups and the molecular weight reduction. Then, the rheological behavior of starch paste changed from pseudo-plastic to non-Newtonian, together with a decreased paste viscosity. These results have demonstrated that dielectric barrier discharge plasma could be used as a new physical method to modulate the structure and rheological properties of starch, for the production of starchy food products with relatively low viscosity at a high concentration.

Recrystallization characteristics of high hydrostatic pressure gelatinized normal and waxy corn starch

High hydrostatic pressure (HHP) can lead to starch gelatinization at room temperature, while the retrogradation mechanism of HHP gelatinized starch is not well known. HHP gelatinized normal and waxy corn starches were stored at room temperature for 192h in order to investigate the retrogradation characteristics. The scanning electron microscopy (SEM), polarised light microscopy and differential scanning calorimetric (DSC) analysis showed that the pressurization of normal and waxy corn starch suspensions with concentration of 30% (w/v) at 600MPa for 15min resulted in a complete gelatinization. In addition, the pressure-gelatinized normal and waxy corn starch gels were stored and subjected to X-ray diffraction (XRD) analysis, resistant starch content determination, swelling power and pasting behavior. The retrograded normal maize and waxy maize starch showed a substantial loss of A-type crystallinity. Both pressure-gelatinized normal and waxy corn starches showed an increase in resistant starch content and relative crystallinity degree with the increase of storage time. In addition, restricted starch swelling power and lower pasting viscosities were observed for these two retrograded starches. The amylose molecule within starch granules has been regarded as the main factor to affect the structural and physicochemical properties during the retrogradation process of HHP-gelatinized starch granules.

Physicochemical Properties of Starch Isolated from Bracken (Pteridium aquilinim) Rhizome.

Bracken (Pteridium aquilinum) is an important wild plant starch resource worldwide. In this work, starch was separated from bracken rhizome, and the physicochemical properties of this starch were systematically investigated and compared with 2 other common starches, that is, starches from waxy maize and potato. There were significant differences in shape, birefringence patterns, size distribution, and amylose content between bracken and the 2 other starches. X-ray diffraction analysis revealed that bracken starch exhibited a typical C-type crystalline structure. Bracken starch presented, respectively, lower and higher relative degree of crystallinity than waxy maize and potato starches. Ordered structures in particle surface differed among these 3 starches. The swelling power tendency of bracken starch in different temperature intervals was very similar to that of potato starch. The viscosity parameters during gelatinization were the lowest in waxy maize, followed by bracken and potato starches. The contents of 3 nutritional components, that is, rapidly digestible, slowly digestible, and resistant starches in native, gelatinized, and retrograded starch from bracken rhizome presented more similarities with potato starch than waxy maize starch. These finding indicated that physicochemical properties of bracken starch showed more similarities with potato starch than waxy maize starch.