Relative Degree Of Crystallinity Research Articles

Mechanical properties, thermal, and crystallization behavior of polypropylene composites reinforced by starch and wasted cotton cloth

AbstractIn this study, wasted cotton cloth was bonded with soluble starches as an adhesive, then dried, cut into fiber fragments and filled into polypropylene (PP) to achieve resource efficiency. The mechanical, thermal, and crystallization properties of the composites were characterized. The results indicated that with the addition of wasted cotton cloth treated without or with silane coupling agent (RC or TRC), PP composites' tensile strength, impact strength, and flexural strength have been improved. The heat distortion temperatures increased slowly, indicating that wasted cotton cloth filled into PP can be turned back into useful items without degradation of PP composites exhibited. Thus, it is a good avenue for the utilization of an otherwise wasted cotton cloth resource. The crystallization activation energy, nucleation constant, and folding surface free energy of PP were markedly reduced in PP/RC composites and its compatibilized composites. The value of F(T) gradually increased with the increasing relative degree of crystallinity. The addition of wasted cotton cloth could significantly reduce the spherulitic size of PP. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of different inorganic filler over isothermal and non-isothermal crystallization of polypropylene homopolymer

In this study, the effect of several inorganic fillers: silicon oxide (SiO2), nanoclay (C20A), alumina (Al2O3), and calcium carbonate (CaCO3) on the crystallization behavior of polypropylene were analyzed for composites with fixed filler content (5 mass%) prepared by intensive mixing following by compression molding. In addition, for calcium carbonate, which produces the highest increase on toughness, PP grafted with maleic anhydride (PP-g-MA) was added to enhance the compatibility. In that case, different content of particles was used (from 5 to 20 mass%) and the synergic effect of both incorporations was demonstrated. For this purpose, isothermal and non-isothermal crystallization tests were carried out in the bulk (by differential scanning calorimetry). In addition, the spherulitic growth was studied (by optical microscopy). Different models were used to predict the relative degree of crystallinity and several parameters were analyzed. All results indicate that whereas alumina and calcium carbonate acted as nucleating agents, silica and nanoclay displayed an opposite behavior. The full models that take into account the different parameters during cooling under isothermal and non-isothermal conditions were used to construct continuous cooling transformation and time temperature transformation diagrams. Both kind of diagrams provide a fundamental tool to understand the crystallization behavior of studied composites and are useful to determine the processing conditions.

Drastic Control of Texture in a High Performance n-Type Polymeric Semiconductor and Implications for Charge Transport

Control of crystallographic texture from mostly face-on to edge-on is observed for the film morphology of the n-type semicrystalline polymer {[N,N-9-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,59-(2,29-bithiophene)}, P(NDI2OD-T2), when annealing the film to the polymer melting point followed by slow cooling to ambient temperature. A variety of X-ray diffraction analyses, including pole figure construction and Fourier transform peak shape deconvolution, are employed to quantify the texture change, relative degree of crystallinity and lattice order. We find that annealing the polymer film to the melt leads to a shift from 77.5% face-on to 94.6% edge-on lamellar texture as well as to a 2-fold increase in crystallinity and a 40% decrease in intracrystallite cumulative disorder. The texture change results in a significant drop in the electron-only diode current density through the film thickness upon melt annealing, while little change is observed in the in-plane transport of bottom gated thin film transistors. This suggests that the texture change is prevalent in the film interior and that either the (bottom) surface structure is different from the interior structure or the intracrystalline order and texture play a secondary role in transistor transport for this material.

Mechanical Properties, Morphology, Thermal Performance, Crystallization Behavior, and Kinetics of PP/Microcrystal Cellulose Composites Compatibilized by Two Different Compatibilizers

Polypropylene (PP)/microcrystalline cellulose (MCC) composites and PP/MCC composites modified by maleic anhydride grafted PP (PP-g-MA) and methyl acrylic acid glycidyl ester grafted PP (PP-g-GMA) respectively were prepared in a twin-screw extruder. The mechanical properties, morphology, and thermal performance were investigated. The nonisothermal crystallization, melting behavior, and nonisothermal crystallization kinetics were investigated by DSC. The results indicated that the addition of MCC had led to the increase of the tensile strength, impact strength, and flexural strength of PP. PP-g-GMA modification was more conducive to the improvement in tensile strength, impact strength, and flexural strength. The three types of PP/MCC composites have higher thermal decomposition temperatures, Vicat softening temperatures, and dimensional stability. Nonisothermal crystallizations of PP/MCC composites were in accordance with tridimensional growth with heterogeneous nucleation. Meanwhile, MCC was acted as the nucleating agent in PP matrix, which increased the crystallization temperature. PP-g-GMA further increased the crystallization temperature while PP-g-MA weakened the heterogeneous nucleation effect of MCC. Avrami equation and Mo method give a satisfactory description of the crystallization kinetics process. The activation energy of crystallization, nucleation constant, and fold surface free energy of PP were markedly reduced in PP/MCC composites and its compatibilized composites. The value of F( T) systematically increased with increasing relative degree of crystallinity. The addition of microcrystalline cellulose has greatly reduced the spherulitic size of PP.

Effect of low energy ion beam implantation on the microstructure of cellulose

The changes of cellulose microstructure after being implanted by low energy N + were studied by infrared (IR), X-ray diffraction (XRD) and scanning electron microscope (SEM). The results showed that the cellulose intramolecular and the intermolecular hydrogen bonds have broken after being implanted by N +. With the increase in implantation doses, the cellulose relative degree of crystallinity reduced gradually, when the implantation doses increased to 1500×10 14 N + cm −2, the relative degree of crystallinity decreased 6.84% than the control sample. Furthermore, the average diameter of cellulose powder reduced gradually as well, and many tiny fragments were visible on the surface of cellulose powder.

Study of the thermal properties of shape memory polyurethane nanofibrous nonwoven

Thermal properties of polymer are very important to the understanding of morphology and shape memory effect of shape memory polymers (SMPs). In this article, the thermal properties of shape memory polyurethane nanofibrous nonwoven are investigated systematically from the morphology of nanofibers, crystalline structure, isothermal crystallization behavior, and thermal-dependent strain recovery. The results indicate that the thermal properties of shape memory polyurethane nanofibrous nonwoven are influenced greatly by the electro-spinning and the recrystalline condition. The crystal melting temperature (T m) decreases as the crystallization temperature (T c) decreases, while the relative degree of crystallinity (X c) increases with the decrease of T c within the temperature range of 20 to −30 °C. In particular, when the annealing temperature is higher than 150 °C, the T m shifts to higher value and the X c decreases significantly with the increase of T c. Finally, temperature-dependent strain recovery curves show that the shape memory polyurethane nanofiber tends to have a lower recovery temperature as compared with the SMPU bulk film due to their ultrafine diameter.

Impact of the Soak and the Malt on the Physicochemical Properties of the Sorghum Starches

Starches were isolated from soaked and malted sorghum and studied to understand their physicochemical and functional properties. The swelling power (SP) and the water solubility index (WSI) of both starches were nearly similar at temperatures below 50 °C, but at more than 50 °C, the starch isolated from malted sorghum showed lower SP and high WSI than those isolated from raw and soaked sorghum. The pasting properties of starches determined by rapid visco-analyzer (RVA) showed that malted sorghum starch had a lower viscosity peak value (86 BU/RVU) than raw sorghum starch (454 BU/RVU). For both sorghum, X-ray diffractograms exhibited an A-type diffraction pattern, typical of cereal starches and the relative degrees of crystallinity ranged from 9.62 to 15.50%. Differential scanning calorimetry (DSC) revealed that raw sorghum starch showed an endotherm with a peak temperature (Tp) at 78.06 °C and gelatinization enthalpies of 2.83 J/g whereas five-day malted sorghum starch had a Tp at 47.22 °C and gelatinization enthalpies of 2.06 J/g. Storage modulus (G′) and loss modulus (G″) of all starch suspensions increased steeply to a maximum at 70 °C and then decreased with continuous heating. The structural analysis of malted sorghum starch showed porosity on the granule’s surface susceptible to the amylolysis. The results showed that physicochemical and functional properties of sorghum starches are influenced by soaking and malting methods.

X-ray diffraction study of temperature dependence of Nairit polychloroprene permolecular structure

With use of the X-ray technique the permolecular structure of Nairit polychloroprene has been investigated. It is shown that the relative degree of crystallinity decreases with the increase in the polymerization temperature. At relatively low temperatures (18–30°C), in Nairits intensive formation of nuclei occurs and simultaneously existing crystallites collapse. Although mean sizes of crystallites decrease, the degree of crystallinity increases. At higher temperatures (above 30°C) melting of existing crystallites and decrease in the number of nuclei lead to decrease in crystallinity and mean sizes of crystallites.

Non-isothermal crystallization kinetics of polypropylene/silicon nitride nanocomposites

The non-isothermal crystallization kinetics of polypropylene/silicon nitride (PP/Si 3N 4) nanocomposites was investigated. The Avrami method, Ozawa method and a method proposed by Mo were applied to the analysis of the non-isothermal crystallization of the PP nanocomposites. Nucleation activity of the Si 3N 4 nanoparticles on the PP matrix was also explored. The nucleation activity was strongest when the Si 3N 4 content was 2 wt%. The effective activation barrier (Δ E) for non-isothermal crystallization was also estimated as a function of the relative degree of crystallinity using the isoconversional analysis of calorimetric data. The value of Δ E was found to vary with the relative degree of crystallinity, as well as with the presence of Si 3N 4 filler.

Quantitative appraisal of the interfacial anchoring state of polyaromatic hydrocarbons during the formation of C/C composites

The preferred anchoring state for polycyclic aromatic hydrocarbons (PAHs) pyrolyzed onto carbon substrates has been studied by semi-quantitative methods, examining their interfacial lattice arrangements. The samples were prepared by decomposing petroleum pitch inside carbon nanotubes resulting in a variety of crystallinities forming one-dimensional C/C composites. Studies indicate that the preferred anchoring state of PAH molecules depends on the nature of the substrate. Accordingly the PAHs in mesophase pitch should exhibit a face-on orientation on the carbonaceous substrates, including a graphite sheet, glassy carbon, and pyrolytic carbon. However, it showed that the anchoring state (face-on or edge-on) of PAH units can be altered even on carbonaceous substrates. The results demonstrated that in C/C composites the anchoring state is predominantly determined by the relative degree of crystallinity of the pitch/carbon substrate, and can be semi-quantitatively estimated using the I D/ I G ratio from Raman spectra. Face-on anchoring is preferred when the I D/ I G ratio of substrate is smaller (higher crystallinity) than that of the pyrolyzed precursor, whereas edge-on anchoring is favored when it is larger. Such an estimation method is useful in tailoring microstructures in the fabrication of C/C composites using PAH precursors.

Overall crystallization behavior of polypropylene–clay nanocomposites; Effect of clay content and polymer/clay compatibility on the bulk crystallization and spherulitic growth

AbstractThe effect of clay nanoparticles on the overall crystallization (isothermal crystallization, spherulitic growth, and nonisothermal crystallization) behavior of polypropylene (PP) was studied by means of differential scanning calorimetry and polarized light optical microscopy. In addition, the changes produced by the compatibility between the filler and the matrix were analyzed by using more hydrophobic clays or incorporating PP grafted with maleic anhydride (PP‐g‐MA). Different models were used to predict the relative degree of crystallinity and several parameters were analyzed. A clear nucleating effect of clay nanoparticles was found on the experimental behavior (induction time, half‐crystallization time, and overall crystallization time) and also deducted from the models parameters (Avrami exponent, rate constant, nucleation activity, activation energy). The effect was also related with the matrix/clay compatibility. In addition, the polarized light optical microscopy showed that the number of spherulites increased and their size decreased when clay was incorporated, which is also an indication of the heterogeneous nucleating behavior of such particles. We also noted faster spherulitic growth and increasing Kg (the model parameter). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis, characterization and properties of biodegradable poly(butylene succinate)‐block‐poly(propylene glycol) segmented copolyesters

AbstractBACKGROUND: To obtain a biodegradable thermoplastic elastomer, a series of poly(ester‐ether)s based on poly(butylene succinate) (PBS) and poly(propylene glycol) (PPG), with various mass fractions and molecular weights of PPG, were synthesized through melt polycondensation.RESULTS: The copolyesters were characterized using 1H NMR, gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, dynamic mechanical analysis, mechanical testing and enzymatic degradation. The results indicated that poly(ester‐ether)s with high molecular weights were successfully synthesized. The composition of the copolyesters agreed very well with the feed ratio. With increasing content of the soft PPG segment, the glass transition temperature decreased gradually while the melting temperature, the crystallization temperature and the relative degree of crystallinity decreased. Mechanical testing demonstrated that the toughness of PBS was improved significantly. The elongation at break of the copolyesters was 2–5 times that of the original PBS. Most of the poly(ester‐ether) specimens were so flexible that they were not broken in Izod impact experiments. At the same time, the enzymatic degradation rate of PBS was enhanced. Also, the difference in molecular weight of PPG led to properties being changed to some extent among the copolyesters.CONCLUSION: The synthesized poly(ester‐ether)s having excellent flexibility and biodegradability extend the application of PBS into the areas where biodegradable thermoplastic elastomers are needed. Copyright © 2009 Society of Chemical Industry

Physicochemical and functional properties of starches from sorghum cultivated in the Sahara of Algeria

Pure starches were isolated from white and red sorghum cultivated in Tidikelt, a hyper arid region situated in south Algeria. Amylose content, X-ray pattern and rheological properties of starches were examined. The amylose content in white sorghum starch (27.1%) was slightly higher than that in red sorghum (24.8%). The swelling power and the solubility behavior of both starches were nearly similar below 65 °C. At higher temperatures, starch isolated from the white sorghum cultivar showed higher swelling power and lower solubility index than pigmented sorghum starch. The pasting properties of starches determined by RVA, Rapid Visco Analyser showed different viscosity peaks. Red sorghum starch had a higher value (4731 cP) than white sorghum starch (4093 cP). For both sorghum, X-ray diffractograms exhibit an A-type diffraction pattern, typical of cereal starches and the relative degrees of crystallinity were estimated at 22.72% and 28.91%, respectively, for local white and red sorghum starch. DSC analysis revealed that sorghum starches present higher temperatures at the peak (70.60 and 72.28 °C for white and red sorghum starches, respectively) and lower gelatinization enthalpies (9.087 and 8.270 J/g for white and red sorghum starches, respectively) than other cereal starches. The results showed that physicochemical and functional properties of sorghum cultivar starches were influenced by the genotype and the environment.

Poly(para‐dioxanone)/inorganic particle composites as a novel biomaterial

In this work, poly(para-dioxanone) (PPDO) was mixed with 1% (by weight) calcium carbonate (CaCO(3)), beta-tricalcium phosphate (beta-TCP), or calcium sulphate dihydrate (CSD) by solution co-precipitation. Samples were compression molded into bars using a platen-vulcanizing press. The morphology, thermal and mechanical properties, and crystalline structure of the composites were investigated using differential scanning calorimetry, polarized optical microscopy, scanning electron microscopy, and X-ray diffraction. All results suggest that three types of inorganic particle in this system promote the crystallinity of PPDO and act as an effective nucleating agent: the relative degree of crystallinity of PPDO increased from 30.74% to 100%, and the crystallization temperature of PPDO was increased by 18 degrees C. On the other hand, the mechanical properties of PPDO were changed by the presence of inorganic particles: the tensile strength of PPDO/CSD increased by 11.46%.

Preparation and nonisothermal crystallization behavior of polypropylene/layered double hydroxide nanocomposites

Polypropylene (PP)/layered double hydroxide (LDH) nanocomposites were prepared via melt intercalation using dodecyl sulfate anion modified LDH and maleated PP as compatibilizing agent. Evidently the interlayer anions in LDH galleries react with maleic anhydride groups of PP-g-MA and lead to a finer dispersion of individual LDH layers in the PP matrix. The nanostructure was characterized by XRD and TEM; the examinations confirmed the nanocomposite formation with exfoliated/intercalated layered double hydroxides well distributed in the PP matrix. The nonisothermal crystallization behavior of resulting nanocomposites was extensively studied using differential scanning calorimetry (DSC) technique at various cooling rates. In nonisothermal crystallization kinetics, the Ozawa approach failed to describe the crystallization behavior of nanocomposites, whereas the Avrami analysis and Jeziorny method well define the crystallization behavior of PP/LDH nanocomposite. Combined Avrami and Ozawa analysis (Liu model) also found useful. The results revealed that very small amounts of LDH (1%) could accelerate the crystallization process relative to the pure PP and increase in the crystallization rates was attributed to the nucleating effect of the nanoparticles. Polarized optical microscopy (POM) observations also support the DSC results. The effective crystallization activation energy was estimated as a function of the relative degree of crystallinity using the isoconversional analysis. Overall, results indicated that the LDH particles in nanometer size might act as nucleating agent and distinctly change the type of nucleation, growth and geometry of PP crystals.

Synthesis and characterization of photocrosslinkable poly( l-lactide)s with a pendent cinnamate group

In this report, we describe the synthesis and characterization of photosensitive poly( l-lactide) with a pendent cinnamate group. α,ω-Dihydoxy terminated poly( l-lactide) (PLLA-diol) [molecular weights (MW); 2000, 4000 and 9000 g/mol ] was chain-extended with a diacyl chloride of 5-cinnamoyloxyisophthalic acid (ICA) to obtain high-molecular-weight photocrosslinkable poly( l-lactide)s (ICA/PLLA). The resulting polyesters were characterized by proton nuclear magnetic resonance spectroscopy, gel permeation chromatography, ultraviolet–visible spectroscopy, differential scanning calorimetry, thermomechanical analysis and thermogravimetry. The glass transition temperature ( T g), the melting temperature ( T m) and the degree of relative crystallinity ( X c) of ICA/PLLAs increased with the increasing MW of the PLLA-diols. The photosensitive ICA/PLLAs were irradiated with a 400 W high-pressure mercury lamp ( λ > 280 nm) for various times to produce the PLLA gel films without a photoinitiator. The crosslinking rate monitored by a UV–vis spectrum decreased with the increasing MW of the PLLA-diols. The crosslinking of the ICA/PLLA −4000 film enhanced the T g slightly and the tensile strength and Young’s modulus significantly, while reduced the T m and X c. The enzymatic degradation was measured by the weight loss of the films in a phosphate buffer solution with proteinaze-k. The crosslinking of the films decreased markedly the degradation rate.

The Effect of Electrocatalytic Activity and Crystal Structure of PbO_2 Surfaces on Polyphenylene Oxide (PPO) Production in Acetonitrile

The crystallographic nature of PbO_2 films was changed by optimizing the electrolysis conditions in an electrodeposition solution of PbO_2. These PbO_2 films were then used to prepare PPO films. It was determined that \alpha and \beta modifications, and relative degrees of crystallinity had profound effects on the electrocatalytic performance of PbO_2 films in the production PPO films.

Properties of bacterial cellulose produced in a pilot-scale spherical type bubble column bioreactor

The saccharogenic liquid obtained by the enzymatic saccharification of food wastes was used as a medium for production of bacterial cellulose (BC). The enzymatic saccharification of food wastes (SFW) was carried out by the cultivation supernatant of Trichoderma inhamatum KSJ1. 5.6 g/L of BC was produced in a new modified 50 L bubble column bioreactor by Acetobacter xylinum KJ1. The productivity was similar to that of a modified 10 L bubble column bioreactor (5.8 g/L). When pure oxygen was supplied into the scaled-up culture conditions, 6.8 g/L (12% enhancement) of BC was produced, indicating a very useful method for BC mass production. The oxygen uptake rate (OUR) and q O2 (specific oxygen uptake rate) were 0.214 mg-DO/L·min and 0.257 mg-DO/g-cell·min, respectively. The physical properties, such as morphology, molecular weight, crystallinity, and tensile strength of BCs produced in static culture (A), 10 L (B) and 50 L (C) modified bubble column cultures were investigated. All BCs showed fibrils with highly networking structure. The number average molecular weight of BCs in A, B and C was 2,314,000, 1,878,000, and 1,765,000, respectively. All of the BCs had a form of cellulose I representing pure cellulose. The relative degree of crystallinity showed the range of 79.6–86.0%. Tensile strengths of BC sheet in A, B and C were 1.75, 1.21, and 1.19 kg/mm2, respectively. In conclusion, BC production by the modified bubble column culture mode of 50 L brought more favorable results in terms of the physical properties and its ease of scale-up.

Manifestations of crystallinity in polyamidobenzimidazoles

Polyamidobenzimidazoles derived from 3,3′,4,4′-tetraaminodiphenyl ether, diphenyl esters of aliphatic and aromatic dicarboxylic acids, and ɛ-caprolactam were prepared by solid-phase polycondensation. The relative degree of crystallinity, imparting the plasticity to the polymers as compared to the corresponding polybenzimidazoles, was determined by X-ray phase analysis.

Nonisothermal Crystallization Kinetics and Melting Behaviors of Isotactic Polypropylene/N,N′,N″″‐tris‐ tert.butyl‐1,3,5‐benzene‐tricarboxamide

The nonisothermal crystallization and melting behavior of an additive‐free (blank) iPP(BPP) and iPP (isotactic polypropylene) containing 0.3 wt% of N,N′,N″‐tris‐tert.butyl‐1,3,5‐benzene‐tricarboxamide (NA) was investigated by the differential scanning calorimetry (DSC). The results showed that adding NA and increasing the cooling rate led to an increased crystallization rate. he BPP presented multiple melting behavior, while the NPP (nucleated iPP) showed a single melting peak with a slightly increased melting peak temperature, and the increased cooing rate had limited influence on the melting peak temperature. Friedman's isoconversion method was used to estimate the activation energy of the nonisothermal process. It was found that the NA led to a more negative value of activation energy, and the magnitude of activation energy increased almost linearly with increased relative degree of crystallinity. The nucleation activity of NA for iPP was calculated according to Dobreva's model, and the result showed that it was a effective nucleating agent for iPP.