scholarly journals Temperature and Time Dependence of the Solvent-Induced Crystallization of Poly(l-lactide)

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1065
Author(s):  
Mahitha Udayakumar ◽  
Mariann Kollár ◽  
Ferenc Kristály ◽  
Máté Leskó ◽  
Tamás Szabó ◽  
...  
Keyword(s):  
Organic Solvents ◽  
Crystal Morphology ◽  
Crystallinity Index ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Relative Crystallinity ◽  
Optical Micrograph ◽  
Unit Cell Size ◽  
Degree Of Crystallization

The role of organic solvents in governing the crystallization and morphology of semi-crystalline poly-l-lactide (PLLA) sheets was systematically investigated. Three different organic solvents; ethyl acetate (EA), o-dichlorobenzene (ODCB), and nitrobenzene (NB), with a solubility parameter analogous to PLLA and with a high capability of swelling, were chosen. It has been witnessed that the degree of crystallization and crystal morphology depends highly on the degree of swelling and evaporation rate of the solvent. Besides, the temperature and time of treatment played a significant role in the crystallization of polymers. The effect of different solvents and curing times are reflected by the measured X-ray diffraction (XRD) peaks and the differences are best shown by the unit cell size. The largest variation is observed along the c-axis, indicating shorter bonds, thus, showing better conformation after NB and ODCB treatment. The percentage of crystallinity calculated using the classical relative crystallinity index of XRD shows closer values to those calculated with differential scanning calorimetry (DSC) data, but a huge variation is observed while using the LeBail deconvolution method. The strong birefringence of polarised optical micrograph (POM) and the crystal morphology of scanning electron micrograph (SEM) also evidenced the orientation of polymer crystallites and increased crystallinity after solvent-supported heat treatment.

scholarly journals Relationship between the Stereocomplex Crystallization Behavior and Mechanical Properties of PLLA/PDLA Blends

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1851
Author(s):  
Hye-Seon Park ◽  
Chang-Kook Hong
Keyword(s):  
Mechanical Properties ◽  
Lactic Acid ◽  
Crystallization Behavior ◽  
Mechanical Analysis ◽  
X Ray Diffraction ◽  
Nucleation Agent ◽  
Scanning Calorimetry ◽  
Nucleation Sites ◽  
Wide Range ◽  
Degree Of Crystallization

Poly (l-lactic acid) (PLLA) is a promising biomedical polymer material with a wide range of applications. The diverse enantiomeric forms of PLLA provide great opportunities for thermal and mechanical enhancement through stereocomplex formation. The addition of poly (d-lactic acid) (PDLA) as a nucleation agent and the formation of stereocomplex crystallization (SC) have been proven to be an effective method to improve the crystallization and mechanical properties of the PLLA. In this study, PLLA was blended with different amounts of PDLA through a melt blending process and their properties were calculated. The effect of the PDLA on the crystallization behavior, thermal, and mechanical properties of PLLA were investigated systematically by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), polarized optical microscopy (POM), dynamic mechanical analysis (DMA), and tensile test. Based on our findings, SC formed easily when PDLA content was increased, and acts as nucleation sites. Both SC and homo crystals (HC) were observed in the PLLA/PDLA blends. As the content of PDLA increased, the degree of crystallization increased, and the mechanical strength also increased.

scholarly journals Role of Surfactants in the Properties of Poly(Ethylene Terephthalate)/Purified Clay Nanocomposites

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1397 ◽  
Author(s):  
Elaine dos Santos ◽  
Marcus Fook ◽  
Oscar Malta ◽  
Suédina de Lima Silva ◽  
Itamara Leite
Keyword(s):  
Clay Nanocomposites ◽  
Phosphonium Salts ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene ◽  
Alkyl Ammonium ◽  
Pet Crystallization

Purified clay was modified with different amounts of alkyl ammonium and phosphonium salts and used as filler in the preparation of PET nanocomposites via melt intercalation. The effect of this type of filler on morphology and thermal and mechanical properties of PET nanocomposites was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analyses (TG), tensile properties, and transmission electron microscopy (TEM). The results showed that the mixture of alkyl ammonium and phosphonium salts favored the production of PET nanocomposites with intercalated and partially exfoliated morphologies with slight improvement in thermal stability. In addition, the incorporation of these organoclays tended to inhibit PET crystallization behavior, which is profitable in the production of transparent bottles.

Crystallization Behavior and Crystal Morphology of PP/POEg Blends

2014 ◽  
Vol 941-944 ◽  
pp. 1253-1256
Author(s):  
Kun Yan Wang
Keyword(s):  
Crystallization Behavior ◽  
Crystal Morphology ◽  
Optical Microscope ◽  
Melt Blending ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Blending Method ◽  
Differential Scanning Colorimetry ◽  
Poly Ethylene ◽  
Spherulitic Structure

Polypropylene (PP)/Maleic anhydride grafted poly (ethylene-octene) (POEg) were prepared by melt blending method. The crystallization behavior and crystal morphology were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarzing optical microscope (POM). Differential scanning colorimetry (DSC) experiments showed that the melting point and crystallization point decreased when POEg added to the blend. XRD results show that the POEg not change the crystal structure in the blends but only decrease the intensity of the diffraction peak. The spherulitic structure could also observed when added POEg to the matix of PP, but the shape of the spherulites distorted.

scholarly journals Use of hydrolysis prior to the chemical and thermomechanical modification of rice starch: alternative to traditional modification treatments

Biotecnia ◽  
2021 ◽  
Vol 23 (1) ◽  
pp. 151-160
Author(s):  
Nancy Grajeda ◽  
Mayra Márquez ◽  
Tomás Galicia García ◽  
Iván Estrada ◽  
Mónica Mendoza ◽  
...  
Keyword(s):  
Crystallinity Index ◽  
Wall Material ◽  
Rice Starch ◽  
Scanning Calorimetry ◽  
Food Ingredient ◽  
Relative Crystallinity ◽  
Native Starch ◽  
Modified Starches ◽  
Acetyl Group ◽  
Starch Gels

Rice starch isolated (NS), was subjected to chemical and thermomechanical modification with previous hydrolysis (MHS) and without previous hydrolysis (MS) to be evaluated on main starch properties as degree of substitution (DS), color, water absorption and solubility index (WAI, WSI), viscosity, texture, thermal properties (differential scanning calorimetry DSC) and structural properties (infrared-IR, Xray-Rx analysis, and relative crystallinity index-ICR). The modified starches were compared to native starch (NS). The DS obtained in both starches was within the range allowed by the FDA for its safety use as food ingredient (0.01-0.2). The modification showed an increase in WAI and WSI values, being WAI value higher in MS (4.80) and WSI value higher in MHS (32.06). The viscosity of retrogradation showed a significant decrease (P<0.05) in both starches (HMS 0.013 and MS 5.613), obtaining gels with greater stability, however, the hardness of starch gels decreased (60 %) while the adhesiveness decreased only in MS (66 %). The crystallinity index (ICR) of the modified starches increased with regard to the native starch indicating a depolymerization of the molecule due to the modification. The presence of the acetyl group in the starch molecule was observed in the signals between 1650 to 1744 cm-1 confirming the esterification. The starches showed a high potential for its application as edible coatings and as wall material for microencapsulation.

Alloy Effects And Extended Solubilities In Binary Mixtures Of Nanometer-Sized Fe-Cu Crystals

1991 ◽  
Vol 238 ◽  
Author(s):  
J. Eckert ◽  
R. Birringer ◽  
J. C. Holzer ◽  
C. E. Krill ◽  
W. L. Johnson
Keyword(s):  
Binary Mixtures ◽  
Phase Region ◽  
Alloy Formation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Two Phase ◽  
Transmission Electron ◽  
Thermodynamic Conditions ◽  
20 Nm

ABSTRACTBinary mixtures of Fe-Cu powders in the range of 10–95 at.% Fe have been prepared by mechanical alloying and investigated by x-ray diffraction, differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The final grain sizes of the powders vary between 6 and 20 nm, and depend on the composition of the material. Indications for the formation of single-phase alloys with up to 60 at.% Fe in Cu and 20 at.% Cu in Fe have been found although the Fe-Cu system exhibits only vanishingly small solid solubilities under equilibrium conditions. Between 60 at.% and 80 at.% Fe a two-phase region of fee and bec solid solutions exists. Alloy formation is discussed with respect to the thermodynamic conditions of the material. The influence of the large grain boundary fraction, as well as the role of internal strains and stored enthalpies introduced by ball milling, is critically assessed.

Ultrasonic Welding of Fe78Si9B13 Metallic Glass

2014 ◽  
Vol 809-810 ◽  
pp. 348-353 ◽  
Author(s):  
Xiao Cun Song ◽  
Zheng Qiang Zhu ◽  
Yan Fei Chen
Keyword(s):  
Metallic Glass ◽  
Metallic Glasses ◽  
Elevated Temperatures ◽  
Supercooled Liquid ◽  
Amorphous Structure ◽  
Ultrasonic Welding ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Optical Micrograph ◽  
Area X

The solid bonds of multi-layer Fe78Si9B13metallic glass foils have successfully been produced by ultrasonic welding technology. The interface of weld joints was investigated by Optical micrograph (OM), scanning electron microscope (SEM) observation, micro-area X-ray diffraction (micro-XRD) and differential scanning calorimetry (DSC) analysis. The results demonstrate that no visible interface and defects were observed and the amorphous structure was maintained. The thermal properties of the joined metallic glasses were the same as that of the parent metallic glass. The formation of joining metallic glasses was attributed to the superplastic flow and the thermal stability at elevated temperatures in the supercooled liquid state. Ultrasonic welding as tack welding proposes an effective method for the preparation of bulk metallic glasses (BMGs) and lays the foundation for its future applications.

scholarly journals Insight in the Crystallization Kinetics of AlPO4-11 Molecular Sieve Using Di-Isopropylamine as Template

2021 ◽  
Vol 11 (14) ◽  
pp. 6544
Author(s):  
Renilson O. Mapele ◽  
Antonio O. S. Silva ◽  
Marcelo J. B. Souza ◽  
Anne M. G. Pedrosa ◽  
Ana C. F. Coriolano ◽  
...  
Keyword(s):  
Infrared Spectroscopy ◽  
Hydrothermal Synthesis ◽  
Crystallization Kinetics ◽  
Molecular Sieve ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Relative Crystallinity ◽  
X Ray ◽  
Ft Ir ◽  
Diffraction Patterns

The hydrothermal synthesis of aluminophosphate molecular sieve type AlPO4-11 was processed from chemicals containing psueudobohemite, 85% phosphoric acid, water, and di-isopropylamine as templating agent. The crystallization of the samples was studied by taking samples in times from 2 to 74 h. The obtained white powder products were characterized by X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry (TG) and differential scanning calorimetry (DTG) data and pH measurement of the mother liquor. The pore volume, as determined from TG and DTG curves, was ca. 0.17 cm3g−1. The percent relative crystallinity was determined by XRD and FT-IR methods. The crystallization kinetics evidenced that the hydrothermal synthesis of AlPO4-11 exhibited in its initial phase a behavior of first order reaction with a specific velocity constant of ca. 0.25 h−1, as determined from XRD and FT-IR data. The results obtained by both X-ray diffraction and infrared spectroscopy are comparable, and FT-IR is found to be a rapid method for estimating crystallinity and structure of aluminophosphate.

Transparent Glass-Ceramics Derived from Spontaneously Crystallized Phosphosilicte Glasses

2011 ◽  
Vol 239-242 ◽  
pp. 1096-1100
Author(s):  
Shu Jiang Liu ◽  
Yan Fei Zhang
Keyword(s):  
Glass Ceramics ◽  
Compositional Variation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Rich Phase ◽  
Transparent Glass ◽  
X Ray ◽  
Phosphosilicate Glass ◽  
Degree Of Crystallization ◽  
Good Transparency

Transparent phosphosilicate glass-ceramics were prepared by heating the spontaneously crystallized precursor glasses in which crystals have formed during cooling of the melts. And the effects of compositional variation on the crystalline phases, degree of crystallization and transparency were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). It is found that Mg2+tends to exist in silicate-rich phase rather than phosphate-rich phase, such MgO is more beneficial to the transparency of phosphosilicate glass-ceremics compared to CaO. In addition, the substitution of P2O5for SiO2enhances the tendency of phase separation, and hence the precipitation of Na2MgSiO4crystals for the precursor glasses as well as glass-ceramics with good transparency.

scholarly journals Tuning the mechanical properties and degradation properties of polydioxanone isothermal annealing

2020 ◽  
Vol 44 (5) ◽  
pp. 1430-1444
Author(s):  
Xiliang LIU ◽  
Shaomin FENG ◽  
Xin WANG ◽  
Jin QI ◽  
Dong LEI ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Isothermal Annealing ◽  
Hydrolytic Degradation ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Optical Micrograph ◽  
Potential Applications ◽  
Degradation Properties ◽  
The Degree Of Crystallinity

Polydioxanone (PPDO) is synthesized by ring-opening polymerization of p-dioxanone, using stannous octoate as the catalyst. The polarized optical micrograph (POM) shows thes pherulite growth rate of PPDO decreases with an increase in the isothermal crystallization temperature. PPDO is compression-molded into bars, and PPDO bars are subjected to isothermal annealing at a range of temperatures (Ta = 50, 60, 70, 80, 90, and 100 °C), and correspond to three different annealing times (ta = 1h, 2h, 3h). The effect on PPDO is investigated by using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM). With an increase in Ta and ta, the grain size and the degree of crystallinity also increase. Meanwhile, the tensile strength is significantly improved. The PPDO bars (90 °C, 2 h) reach the maximum crystallinity (57.21%) and the maximum tensile strength (41.1 MPa). Interestingly, the heat treatment process does not result in serious thermal degradation. It is observed that the hydrolytic degradation of the annealed PPDO is delayed to some extent. Thus, annealed PPDO might have potential applications, particularly in the fields of orthopedic fixation and tissue engineering.

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