Crystallization properties of polycaprolactone composites filled with nanometer calcium carbonate

Polycaprolactone (PCL) composites filled with nanometer calcium carbonate (nano‐CaCO₃) were prepared by means of a twin‐screw extruder in this study. The nano‐CaCO₃ surface treated with stearate. The crystalline properties of the PCL/nano‐CaCO₃ composites were measured with a differential scanning calorimeter to identify the influence of the nanometer filler content on the crystalline properties. The results show that the crystallization onset temperature, crystallization temperature, and crystallization end temperature of the composites were obviously higher than those of the unfilled PCL resin, and the crystallization degree (χ_c) of the composites increased with increasing particle weight fraction (?_f) when ?_f was more than 1%. When ?_f was 1%, χ_c of the composite was less than that of the unfilled PCL resin. Moreover, the dispersion of the inclusions in the matrix was observed by means of scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Crystallization kinetics of glass fiber reinforced PBT composites

The effect of glass fibers on the crystallization of poly(butylene terephthalate) (PBT) was investigated by crystallization kinetics analysis under isothermal and nonisothermal conditions. From the crosspolar optical micrographs of melt‐ and solvent‐crystallized PBT composites, the glass fibers were found to increase the number density and decrease the size of crystallites. The glass fibers provided heterogeneous nucleation sites, and thus enhanced the overall rate of PBT crystallization in isothermal experiments. However, the Avrami exponent and the regime transitions were not significantly affected by the presence of glass fibers. For the nonisothermal kinetics of PBT composites, the model prediction was excellent in most ranges of crystallization, but it deviated above 70% of crystallization especially at fast cooling rates (>40°C/min). This discrepancy of the model seemed to result from the growth regime transitions, which were clearly observed especially at high undercoolings. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 576–585, 2000     

Crystallization kinetics of polypropylene composites filled with nano calcium carbonate modified with maleic anhydride

The subject of this study was the crystallization behavior and thermal properties of polypropylene (PP)/maleic anhydride (MAH) modified nano calcium carbonate (nano‐CaCO₃) composites. In this study, 5 wt % nano‐CaCO₃ modified with different contents of MAH was filled into a PP matrix. X‐ray diffraction and differential scanning calorimetry were used to characterize the crystal morphology and crystallization kinetics of a series of composites. The results demonstrate that the nano‐CaCO₃ modified with MAH had an important effect on the thermal and morphological properties of the nanocomposites. The Avrami exponent of the pure PP was an integer, but those of the composites were not integers, but the crystallization rate constant decreased as the content of MAH in the nano‐CaCO₃ filler increased in isothermal crystallization. In nonisothermal crystallization, the kinetic parameter F(T) and the degree of crystallinity of pure PP were compared with those of the PP composites filled with nano‐CaCO₃. We suggest that heterogeneous nucleation existed in the PP composites and that the transformation and retention of the β‐form crystal into the α‐form crystal took place in the composite system and the β‐form crystal had a higher nucleation rate and growth process than the α‐form crystal in the PP composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Isothermal crystallization kinetics and mechanical properties of polycaprolactone composites with zinc oxide,oleic acid,and glycerol monooleate

The isothermal crystallization and mechanical behavior of polycaprolactone (PCL) with zinc oxide (ZnO) with oleic acid and glycerol monooleate (GMO) were studied. Theoretical melting points calculated by the Flory–Huggins and Thompson–Gibbs models were thoroughly compared with differential scanning calorimetry experimental observations. The isothermal crystallization kinetic parameters by Avrami analysis showed that crystallization was controlled by nucleation, crystal growth was spherical, and the nucleation type changed between thermal and athermal nucleation. X‐ray diffraction showed that when the additives were used together both the crystal thickness and the degree of crystallinity increased. A multiple‐response regression analysis was made with the ZnO, oleic acid, and GMO concentrations as variables and the crystallinity as output. Interaction parameters by the Pukanzky model were calculated from the tensile strength at the yield point and indicated that the addition of oleic acid or GMO improved the interface between the ZnO particles and PCL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1259‐1275, 2013     

Crystallization kinetics of poly(butylene terephthalate) and its talc composites

Crystallization kinetics of poly (butylene terephthalate) (non‐talc‐PBT) and its 0.1 wt % talc composites (talc‐PBT) was determined for a wide range of cooling rates and isothermal temperatures. The critical cooling rate to suppress crystallization is 2000 K s^?1 for non‐talc‐PBT and 7000 K s^?1 for talc‐PBT. The cooling rate dependence of the total enthalpy change and heating rate dependence of enthalpy of cold crystallization are quantitatively discussed on the basis of the Ozawa's method. For isothermal crystallization, the annealing‐temperature (T _iso) dependence of crystallization half‐time (t _1/2) shows a bimodal curve with two minima. Talc shortens the t _1/2 at T _iso above 340 K and acts as a heterogeneous nucleation agent. Tammann's approach revealed that the t _1/2 is shortened by pre‐nucleation for non‐talc‐PBT but not for talc‐PBT. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44739.     

Crystallization kinetics of highly filled glass fibre/polyamide 6 composites

Summary The present paper deals with the isothermal and non-isothermal crystallization of pure polyamide 6 (PA 6) and PA 6/glass fibre composite with a high fibre content of 81 % by weight. The so-called Avrami exponent n of pure PA 6 seems to be nearly independent of crystallization temperature fluctuating around 3.0 whereas for the composite this quantity increases strongly with crystallization temperature from 1.2 to about 6.     

Crystallization kinetics of iPP: Influence of operating conditions and molecular parameters

An analysis of the crystallization kinetics of different grades of isotactic polypropylene (iPP) is here presented. To describe the crystallization kinetics as a function of molecular and operating parameters, the methodological path followed was the preparation of quenched samples of known cooling histories, calorimetric crystallization isotherms tests, differential scanning calorimetry cooling ramps, wide angle X‐ray diffraction (WAXD) measurements, and density determination. The WAXD analysis performed on the quenched iPP samples confirmed that during the fast cooling at least a crystalline structure and a mesomorphic one form. The diffractograms were analyzed by a deconvolution procedure, to identify the relationship between the cooling history and the distribution of the crystalline phases. The whole body of results (including calorimetric ones) provides a wide basis for the identification of a crystallization model suitable to describe solidification in polymer‐processing operations, based on the Kolmogoroff–Avrami–Evans nonisothermal approach. The kinetic parameters, determined for all the materials, are discussed, highlighting the effect of molecular parameters on the crystallization kinetics: molecular mass and distribution, tacticity, nucleating agents, and ethylene units content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1358–1367, 2007     

Enhancement of basic properties of polysaccharide-based composites with organic and inorganic fillers: A review

The global shift towards biodegradable composite has made polysaccharides a green alternative to synthetic polymers owing to their biocompatibility, sustainability, and ecofriendly biomaterials. Despite the limitations in their applications, many studies have validated the effectiveness of using organic or inorganic fillers to ameliorate their mechanical and barrier properties. However, the understanding of how polysaccharides matrix is enhanced by fillers is still inexplicit. Hence, it is imperative to review the effects of using inorganic and organic fillers in some prominent polysaccharides in terms of mechanical and water barrier properties while taking into account the function of filler morphology, size and loading. Although it is intricate to indicate the best filler used for each of the polysaccharides matrices, this review served as a “food for thought” on the established works of enhanced-matrix filler combinations aimed at improving the mechanical and barrier properties of biodegradable films based on neutral or negatively charged polysaccharides-based composite films for potential application in food packaging, agriculture, biomedicine and constructions sector. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47251.     

Volatilization of ammonia from urea-ammonium nitrate solutions as influenced by organic and inorganic additives

Fertilizers containing urea can suffer from nitrogen (N) loss through ammonia volatilization, resulting in reduced effectiveness of the fertilizers. The loss of N may be reduced by use of organic or inorganic additives.Laboratory experiments were conducted on surface soil samples (0–15 cm) from two agricultural soils (St. Bernard and Ste. Sophie) to determine the impact of ammonium thiosulfate (ATS), boric acid, and a humic substance from leonardite, on NH₃ losses from surface-applied urea-ammonium nitrate (UAN) solutions. Experiments were carried out using moist soil samples in closed containers. Evolved NH₃ was carried out of the containers and trapped in boric acid solution using an ammonia-free humidified air flow.Total NH₃ losses in these experiments ranged from 12.1 to 21.3% of the N applied. The reduction in NH₃ volatilization (expressed as % of added N) due to additives ranged from 13.6 to 38.5% and 3 to 36.3% in St. Bernard and Ste. Sophie soils, respectively. More NH₃ volatilized from the boric acid or humic treated UAN solutions than from ATS-UAN solutions.Boric acid, ATS, and the humic substance, all significantly reduced urea hydrolysis in both soils in comparison to the untreated UAN solution. Further, the humic substance and boric acid treatment induced significant reduction in NO₃-formation. The results suggest that humic substance and to a lesser extent boric acid may function as urease and/or nitrification inhibitors. ATS treatment, particularly at higher levels increased NO₃-formation in both soils. The reason for this increase in nitrate formation is not clear.     

Crystallisation kinetics and morphology of high density polyethylene containing organic and inorganic pigments

Some organic pigments, present in very small amounts (0.1 to 0.2%), can cause warpage and shrinkage phenomena in moulded parts of linear polyethylene. Investigations on such phenomena have been carried out by dilatometric and morphological analysis. The influence on polyethylene crystallisation kinetics and morphology of such organic and inorganic pigments, which do not cause any deformation effect, has been studied. The experimental results show that only organic pigments increase the crystallisation rate, by acting as nucleating agents; in these cases, moreover, the crystalline grain is smaller and the typical morphology of polyethylene crystallised in bulk is altered. A possible correlation between the nucleating action and the warpage effect of organic pigments on moulded polyethylene is discussed.     

水性聚氨酯的结晶动力学参数及其在鞋用胶黏剂的应用

以聚己二酸1,4-丁二醇酯（PBA）、六亚甲基二异氰酸酯（HDI）和异佛尔酮二异氰酸酯（IPDI）为主要原料,制备了不同软段分子量和不同硬段含量的水性聚氨酯（WPU）乳液。采用DSC技术表征了WPU胶膜在非等温和等温条件下的结晶行为,并以莫志深方程和Avrami方程为模型,对WPU胶膜的结晶行为进行了研究。WPU胶膜的非等温结晶动力学分析结果表明,随着WPU相对结晶度的增加,非等温结晶动力学参数F（T）增大,说明适当提高活化温度可提高WPU胶黏剂的结晶速率和初黏强度;WPU胶膜的等温动力学分析结果表明,不同软段分子量和不同硬段含量的WPU胶膜的等温结晶动力学参数t_1/2与相应WPU胶黏剂的开放时间存在对应关系,即t_1/2较大者,相应WPU胶黏剂的开放时间较长。     

Crystallization kinetics of PPS composites and quantification of fiber nucleation density using a computer simulation

Differential scanning calorimetry and hot-stage optical microscopy were used to study the isothermal crystallization kinetics of unreinforced poly(phenylene sulfide) (PPS) and PPS reinforced with aramid, carbon, and glass fibers. The influence that fibers have on the crystallization kinetics of PPS was found to depend on the characteristics of the fiber as well as the type of PPS used. For one kind of PPS, fibers enhanced the crystallization rate, while for another type of PPS, reinforcing fibers had a moderate depressing effect on the polymer crystallization rate. To clarify these effects, we used a new method of quantifying the nucleation process in fiber-reinforced composites that employs a 3-D computer simulation of spherulitic crystallization. Using this method, the nucleation density in the bulk polymer, N_b, and the nucleation density on fiber surfaces, N_f, were calculated for PPS composites as a function of crystallization temperature. The calculated values of N_b and N_f were used to explain differences in the effectiveness of the fibers as well as differences in the nucleating characteristics of the two polymers. © 1995 John Wiley & Sons, Inc.     

Micellar thin-layer chromatographic separation of heavy metal cations: Effect of organic and inorganic additives on migration behavior

The migration behavior of heavy metal cations on cellulose layers using aqueous micellar, hydro-organic, and water-organic-surfactant mobile phases was investigated. Anionic, cationic, and nonionic surfactant systems were examined over a 0.001–5% concentration range. Brij-35, a nonionic surfactant capable of forming charged complexes with some metal ions, was identified as the best surfactant. The effect of the presence of organic additives, such as dimethylsulfoxide, dimethylformamide, methanol and acetone, on the mobility of metal ions was also studied. Acetone was found to be the most effective additive at 10% concentration with 3% Brij. Quantitative determination of UO₂ ²⁺ by spectrophotometry after preliminary thin-layer chromatographic (TLC) separation from Fe³⁺ and Hg²⁺ was also performed. A maximal recovery of 93% was obtained. This TLC method is rapid, with development times averaging 2 min.     

Influence of inorganic and organic additives on the composition of the precipitate of synthetic hydroxylapatite and calcium oxalate monohydrate

Synthetic hydroxylapatites are prepared with additives, such as Mg²⁺, CO ₃ ^2? , and C₂O ₄ ^2? . An increase in the concentration of magnesium leads to the formation of struvite. In the Ca(NO₃)₂-(NH₄)HPO₄-Na₂CO₃-NH₄OH-H₂O system, an excess of carbonate ions leads to the formation of calcite. When the synthesis is performed using oxalate ions as additives, calcium oxalate does not form the inherent phase. Calcium oxalate monohydrate is synthesized with additives, such as CO ₃ ^2? , HPO ₄ ^2? , and SO ₄ ^2? ions and urea, glycine, and glutamic acid. X-ray powder diffraction analysis has revealed that the composition of the CaC₂O₄ · H₂O precipitate remains unchanged under these conditions and in the presence of the aforementioned additives.     

Sintering kinetics of high-alumina ceramics with complex additives

Results of a study of ceramic compaction kinetics under conditions of isothermal and nonisothermal heating are given. Kinetic equations of the compaction process using a structure/energy parameter as the dependent variable are given, and on this basis values of apparent activation energy for two compaction stages are determined. It is demonstrated that modification transitions and formation of unstable phases and solid solutions in the course of ceramic firing have a substantial effect on the mechanism of ceramic compaction. Translated from Steklo i Keramika, No. 4, pp. 9 – 12, April, 1999.     

Crystallization kinetics by differential scanning calorimetry for PCL/starch and their reinforced sisal fiber composites

Calorimetric results obtained by differential scanning calorimetry (DSC) have been used to develop a kinetic model for the crystallization behavior of PCL/starch and their composites with sisal fibers. The model takes into account the effects of nucleation and crystal growth, and it is able to describe the isothermal and non‐isothermal conditions, especially for the low cooling rates. The effect of the sisal fiber has also been analyzed. The Avrami exponent was 2.0 for the crystallization of PCL/starch and sisal fiber reinforced composite. The activation energy of the crystallization process was 4.3 and 4.0 kJ/mol for PCL/starch and sisal composite, respectively. The induction time of the crystallization and the crystallization rate was not influenced by the presence of sisal fiber.     

高质量分数对二甲苯结晶动力学研究

利用间歇动态法研究高质量分数混合二甲苯中的对二甲苯结晶动力学,应用矩量变换法求解粒数衡算方程,通过测量结晶过程中的母液温度和对二甲苯质量分数的变化,由非线性优化法求解对二甲苯结晶动力学参数。实验结果表明,在自然降温和线性降温方式下,所得到的结晶动力学参数一致,而且能很好地模拟对二甲苯结晶过程的母液中对二甲苯质量分数的变化,相对误差大多在±0.5%以内,因而可以用来优化和模拟对二甲苯结晶过程。     

Preparation and characterizations of polycaprolactone/green coconut fiber composites

The mechanical, thermal, and morphological properties of polycaprolactone (PCL) and green coconut fiber (GCF) composites were evaluated. Blends containing acrylic acid‐grafted PCL (PCL‐g‐AA/GCF) exhibited noticeably better mechanical properties due to better compatibility between the two components. The dispersion of GCF in the PCL‐g‐AA matrix was significantly more homogeneous due to the creation of branched and cross‐linked macromolecules via reactions between carboxyl groups in PCL‐g‐AA and hydroxyl groups in GCF. The tensile strength of the PCL‐g‐AA/GCF composites at break was considerably greater than that of PCL/GCF composites. In addition, the PCL‐g‐AA/GCF blend was more easily processed due to lower melt viscosity. Biodegradation tests were performed with each composite in an Acinetobacter baumannii BCRC 15556 environment. The mass of both composites was reduced by the GCF content within 4 weeks. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thin films of organic polymer composites with inorganic aerogels as dielectric materials: polymer chain orientation and properties

Summary High temperature poly(p-phenylene biphenyltetracarboximide) nanocomposite films with inorganic particulates, which are applicable to the fabrication of microelectronic devices, were prepared from the poly(amic acid) and silica aerogels with a size of ca. 150 nm in diameter by solution blending and subsequent conventional polyimide film formation process. The structure and properties were measured. By the composite formation, the optical and dielectric properties were improved due to the low dielectric constant characteristic of silica aerogels, whereas the interfacial stress and thermal expansion coefficient were significantly degraded by a large disturbance in the polymer chain in-plane orientation caused by silica aerogels despite of their low thermal expansivity. This indicates that in the rigid type of polymer composites with inorganic particulates, the orientation of polymer chains still plays a critical role on the physical properties.     

刚性无机粒子增韧聚氯乙烯/有机蒙脱土复合材料的结构与性能研究

采用纳米碳酸钙(nano-CaCO3)对PVC/有机蒙脱土复合材料进行了填充改性,通过X射线衍射和透射电镜对复合材料的结构进行了表征。采用基本断裂功的方法研究了复合材料的断裂韧性。结果表明,nano-CaCO3和有机蒙脱土在PVC基体中实现了纳米尺度的分散,两者对PVC具有协同增韧的作用。