scholarly journals Effect of Heterogeneous Deacetylation on the Properties of Northern Shrimp Chitin and Chitosan

2020 ◽  
Author(s):  
Nataliia Dolgopiatova ◽  
Yuliya Kuchina ◽  
Tatiana Dyakina ◽  
Tatiana Volkova
Keyword(s):  
Molecular Weight ◽  
Shear Stress ◽  
Alkaline Treatment ◽  
Degree Of Crystallinity ◽  
Repeated Treatment ◽  
Experimental Conditions ◽  
Northern Shrimp ◽  
Chitin And Chitosan ◽  
Chitosan Deacetylation ◽  
The Degree Of Crystallinity

The effect of alkaline treatment of shrimp chitin on the molecular weight, the degree of deacetylation and degree of crystallinity of the resulting chitosan is studied. The viscosity of chitosan solutions from repeatedly deacetylated chitin is studied. It is shown that repeated treatment of chitin/chitosan with alkali causes the destruction of polysaccharide macromolecules. After four-time deacetylation and one-time deacetylation of chitin/chitosan for four hours, the molecular weight of the polysaccharide decreases by ten times. The maximum degree of chitosan deacetylation under experimental conditions was 92.0 -92.5%. The diffractograms of chitin and chitosan from the Northern shrimp are of the form typical for samples containing an amorphous phase in addition to a crystalline phase. The degree of crystallinity of chitin from Northern shrimp was 40.8%, of chitosan samples after one-, two-, and three-time deacetylation was 62-65%. For a sample of chitosan obtained after four-time deacetylation, recrystallization, and drying in a freeze dryer, the degree of crystallinity is close to the degree of crystallinity of shrimp chitin. The investigated acetic acid chitosan solutions with a concentration of 5% (wt.) and the chitosan molecular weight of 250, 160 and 130 kDa in their rheological properties are liquid-like non-Newtonian systems, their viscosity decreasing with increasing shear stress. After four-time deacetylation of chitin, the viscosity of chitosan solutions practically does not change with increasing shear stress, which apparently can be due to a significant decrease in the molecular weight of chitosan under these conditions.

Effect of Tension on Mechanical Properties and Structure of Aramid Fibers during Heat Treatment

2013 ◽  
Vol 774-776 ◽  
pp. 856-859
Author(s):  
Hong Peng Zhong ◽  
Ahmed DawElbeit ◽  
Hai Juan Kong ◽  
Chun Mao Kang ◽  
Mei Hua ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Molecular Weight ◽  
Surface Topography ◽  
Fiber Strength ◽  
Degree Of Crystallinity ◽  
Aramid Fibers ◽  
Weight Decrease ◽  
The Degree Of Crystallinity

The heat treatment was carried out to modify the aramid fibers, and the effect of tension on the mechanical properties and structure was investigated through Fiber Strength Equipment, viscosity, XRD and SEM . The results show that fibers，strength slightly decrease, but modulus increase significantly according to the increasing of tension at 480°C and 10s, and reach a maximum when the tension value is 300 g. After heat treatment, molecular weight decrease and the degree of crystallinity increase. SEM show that there is little effect on the surface topography of the fibers during treatment.

scholarly journals Investigation of Thermal Behavior of Layered Double Hydroxides Intercalated with Carboxymethylcellulose Aiming Bio-Carbon Based Nanocomposites

2019 ◽  
Vol 3 (2) ◽  
pp. 55
Author(s):  
Vagner R. Magri ◽  
Alfredo Duarte ◽  
Gustavo F. Perotti ◽  
Vera R.L. Constantino
Keyword(s):  
Layered Double Hydroxides ◽  
Mixed Oxides ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Vibrational Spectroscopies ◽  
Xrd Patterns ◽  
Double Hydroxides ◽  
The Degree Of Crystallinity

Carboxymethylcellulose (CMC), a polymer derived from biomass, was intercalated into layered double hydroxides (LDH) composed by M2+/Al3+ (M2Al-CMC, M = Mg or Zn) and evaluated as precursors for the preparation of biocarbon-based nanocomposites by pyrolysis. M2Al-CMC hybrids were obtained by coprecipitation and characterized by X ray diffraction (XRD), vibrational spectroscopies, chemical analysis, and thermal analysis coupled to mass spectrometry. Following, pyrolyzed materials obtained between 500–1000 °C were characterized by XRD, Raman spectroscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Above 600 °C, Raman spectra of all samples showed the presence of graphitic carbon, which plays a role in the degree of crystallinity of produced inorganic phases (for comparison purposes, M2Al-CO3 materials were investigated after calcination in the same experimental conditions). XRD patterns of Mg2Al-CMC pyrolyzed between 600–1000 °C showed poorly crystallized MgO and absence of spinel reflections, whereas for Zn2Al-CMC, it was observed well crystallized nanometric ZnO at 800 °C, and ZnAl2O4 and γ-Al2O3 phases at 1000 °C. Above 800 °C, the carbothermic reaction was noticed, transforming ZnO to zinc vapour. This study opens perspectives for nanocomposites preparation based on carbon and inorganic (mixed) oxides through precursors having organic-inorganic interactions at the nanoscale domain.

scholarly journals Crystallinity of Electrospun and Centrifugal Spun Polycaprolactone Fibers: A Comparative Study

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Eva Kuzelova Kostakova ◽  
Laszlo Meszaros ◽  
Gabriela Maskova ◽  
Lenka Blazkova ◽  
Tamas Turcsan ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Production Technology ◽  
Average Molecular Weight ◽  
Degree Of Crystallinity ◽  
Fibrous Materials ◽  
Scanning Calorimetry ◽  
Crystallinity Degree ◽  
A Minor ◽  
Technology Effects ◽  
The Degree Of Crystallinity

Crystalline properties of semicrystalline polymers are very important parameters that can influence the application area. The internal structure, like the mentioned crystalline properties, of polymers can be influenced by the production technology itself and by changing technology parameters. The present work is devoted to testing of electrospun and centrifugal spun fibrous and nanofibrous materials and compare them to foils and granules made from the same raw polymer. The test setup reveals the structural differences caused by the production technology. Effects of average molecular weight are also exhibited. The applied biodegradable and biocompatible polymer is polycaprolactone (PCL) as it is a widespread material for medical purposes. The crystallinity of PCL has significant effect on rate of degradation that is an important parameter for a biodegradable material and determines the applicability. The results of differential scanning calorimetry (DSC) showed that, at the degree of crystallinity, there is a minor difference between the electrospun and centrifugal spun fibrous materials. However, the significant influence of polymer molecular weight was exhibited. The morphology of the fibrous materials, represented by fiber diameter, also did not demonstrate any connection to final measured crystallinity degree of the tested materials.

scholarly journals Закономерности микродеформации сверхвысокомолекулярного полиэтилена, модифицированного добавками галлуазита

2018 ◽  
Vol 60 (7) ◽  
pp. 1341
Author(s):  
В.В. Шпейзман ◽  
П.Н. Якушев ◽  
В.М. Егоров ◽  
С.В. Васильева ◽  
А.С. Смолянский
Keyword(s):  
Molecular Weight ◽  
Strain Rate ◽  
Transition Energy ◽  
Ultrahigh Molecular Weight Polyethylene ◽  
Degree Of Crystallinity ◽  
Effect Of Additives ◽  
Calorimetric Measurements ◽  
Ultrahigh Molecular Weight ◽  
Interference Measurement ◽  
The Degree Of Crystallinity

AbstractThe effect of additives of 1 and 3 wt % of halloysite on the rate and small jumps of deformation under uniaxial compression of ultrahigh-molecular-weight polyethylene was investigated. A procedure for precision interference measurement with a resolution of 325 nm for displacement and 1 kHz for frequency enabled the detection of several levels of deformation in the micro- and nanometer ranges. The addition of halloysite results in a decrease in the strain rate under the same loading conditions and a change in the characteristics of the strain jumps. Calorimetric measurements showed that melting of polyethylene with a different concentration of halloysite causes a change in the transition energy and the degree of crystallinity.

Investigation of the Crystallization of Polyetherketones by the Differential Scanning Calorimetry Method

2018 ◽  
Vol 935 ◽  
pp. 36-39 ◽  
Author(s):  
Azamat A. Zhansitov ◽  
Azamat L. Slonov ◽  
Arthur E. Baikaziev ◽  
Marina M. Murzakanova ◽  
S.Yu. Khashirova
Keyword(s):  
Molecular Weight ◽  
Differential Scanning Calorimetry ◽  
Phase Transitions ◽  
Crystallization Temperature ◽  
Amorphous Structure ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
Polyether Ether Ketone ◽  
Ether Ketone ◽  
The Degree Of Crystallinity

Differential scanning calorimetry was used to study the temperatures and character of phase transitions of fibers based on polyether ether ketones. It is shown that in the production of fine fibers from polyether ether ketones, a predominantly amorphous structure is formed. Increasing the temperature to the crystallization temperature leads to an almost twofold increase in the degree of crystallinity. Lower molecular weight polyether ether ketone is characterized by a higher rate of crystallization and the formation of a more homogeneous crystalline structure.

Thermal Crystallization of Polytetrahydrofuran Networks

1991 ◽  
Vol 64 (1) ◽  
pp. 74-82 ◽  
Author(s):  
C. Michael Roland ◽  
Gary S. Buckley
Keyword(s):  
Melting Point ◽  
Crystallization Behavior ◽  
Degree Of Crystallinity ◽  
Melting Point Depression ◽  
Network Architectures ◽  
Experimental Conditions ◽  
Thermal Crystallization ◽  
Melting Temperatures ◽  
Equilibrium Melting Point ◽  
The Degree Of Crystallinity

Abstract The formation of a network in PTHF inhibits the crystallization of chain units in proximity to the crosslinks. From melting-point-depression measurements, it is estimated that the suppression in crystallizability extends to as much as 8 chain units away from a network junction. This estimate is consistent with the degree of crystallinity measured in various crosslinked PTHF rubbers. The equilibrium melting point for linear PTHF was determined to be 361°K. Although this is significantly higher than previously reported values, the present result is congruent with the melting temperatures measured for crosslinked PTHF, and its use leads to satisfactory predictions of their melting-point depression. The distribution in the lengths of network chains exerted a trivial influence on thermal crystallization behavior. Although this distribution must in principle influence crystallization behavior in so far as it governs crystallizable sequence lengths, differences between uni- and bi-modal network architectures were moderate under the present experimental conditions.

The Influence of e-Beam Irradiation on the Morphology and Functional Properties of UHMWPE

2013 ◽  
Vol 197 ◽  
pp. 6-12
Author(s):  
Joanna Maszybrocka ◽  
Adrian Barylski ◽  
Jerzy Cybo ◽  
Piotr Czaja
Keyword(s):  
Molecular Weight ◽  
Friction Surface ◽  
Morphological Changes ◽  
Crosslinking Density ◽  
Degree Of Crystallinity ◽  
Beam Irradiation ◽  
Sem Images ◽  
Applied Dose ◽  
Radiation Modification ◽  
The Degree Of Crystallinity

The paper presents an analysis of the effectiveness of radiation modification of GUR 1050 and GUR 1020 polymers intended for endoprosthesis bearing components. It has been demonstrated through extraction and expansion that the crosslinking density increases as the applied dose of electron irradiation and the molecular weight of polyethylene grow. The recorded changes were accompanied by an increase in the degree of crystallinity, which was more significant in the case of the more heavy GUR 1050 (compared to GUR 1020). The morphological changes are supported by the results of micromechanical, sclerometric and tribological examinations. Tribological examinations were documented with SEM images of the surface of specimens subjected to oscillatory friction (roll-block tester). Series of crosswise valleys and projections, arranged along the friction direction, were found on the friction surface. The smoothening of the surface and a lack of lamella fragments on the base specimens which were not subjected to e-beam irradiation are observed along with a reduction of wear due to the increasing dose of irradiation.

scholarly journals Estimation of the Age of Architectural Heritage Objects by Microstructural Changes of Calcite in Lime Mortars of Ancient Brickwork and Masonry

Buildings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 240
Author(s):  
Vladimir Kotlyar ◽  
Victoria Pishchulina ◽  
Alexey N. Beskopylny ◽  
Besarion Meskhi ◽  
Yury Popov ◽  
...  
Keyword(s):  
18Th Century ◽  
Degree Of Crystallinity ◽  
Architectural Heritage ◽  
Natural Conditions ◽  
Relative Age ◽  
Lime Mortars ◽  
Powder Samples ◽  
Diffraction Patterns ◽  
Cultural Monuments ◽  
The Degree Of Crystallinity

Determining the age of ancient architectural and cultural monuments is a significant scientific problem. An approach based on the transformation of portlandite into calcite and subsequent recrystallization of calcite is considered, which allows for estimating the relative age of ancient brickworks for local groups of historic buildings based on the results of diffraction studies of powder samples of carbonate mortars and measurements of samples with a known age. This article presents the results of the study of lime mortars of ancient brickwork. Under natural conditions, the process of transformation of portlandite into calcite takes from 100 to 200 years. The rate of this process is influenced by temperature, humidity, peculiarities of interaction with carbon dioxide contained in the air, etc. Examples show that portlandite is completely transformed into calcite in masonry mortars of the 18th century and that portlandite is not found in older mortars. It was determined that after the transformation of portlandite into calcite, an increase in the degree of recrystallization of calcite is observed, which manifests itself in powder diffraction patterns in the relative broadening of the diffraction peak of calcite hkl 104. In a detailed study, an estimate of the peak width at half maximum (FWHM) associated with the degree of crystallinity is effective. The actual data are given, which show that in older lime mortars the degree of recrystallization of calcite is higher than in younger ones. This fact makes it possible to indirectly determine the relative age of brickwork and masonry of various buildings of architectural heritage, which is especially relevant for the objects with the use of lime mortars of the northern provinces of the Byzantine Oecumene and other periods of various cultures.

scholarly journals Impact of Macrodiols on the Morphological Behavior of H12MDI/HDO-Based Polyurethane Elastomer

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2060
Author(s):  
Shazia Naheed ◽  
Mohammad Zuber ◽  
Mahwish Salman ◽  
Nasir Rasool ◽  
Zumaira Siddique ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Contact Angle ◽  
Chain Length ◽  
Microphase Separation ◽  
Soft Segment ◽  
Group Identification ◽  
Degree Of Crystallinity ◽  
Polyurethane Elastomers ◽  
Hard Segments ◽  
Morphological Behavior

In this study, we evaluated the morphological behavior of polyurethane elastomers (PUEs) by modifying the soft segment chain length. This was achieved by increasing the soft segment molecular weight (Mn = 400–4000 gmol−1). In this regard, polycaprolactone diol (PCL) was selected as the soft segment, and 4,4′-cyclohexamethylene diisocyanate (H12MDI) and 1,6-hexanediol (HDO) were chosen as the hard segments. The films were prepared by curing polymer on Teflon surfaces. Fourier transform infrared spectroscopy (FTIR) was utilized for functional group identification in the prepared elastomers. FTIR peaks indicated the disappearance of −NCO and −OH groups and the formation of urethane (NHCOO) groups. The morphological behavior of the synthesized polymer samples was also elucidated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The AFM and SEM results indicated that the extent of microphase separation was enhanced by an increase in the molecular weight of PCL. The phase separation and degree of crystallinity of the soft and hard segments were described using X-ray diffraction (XRD). It was observed that the degree of crystallinity of the synthesized polymers increased with an increase in the soft segment’s chain length. To evaluate hydrophilicity/hydrophobicity, the contact angle was measured. A gradual increase in the contact angle with distilled water and diiodomethane (38.6°–54.9°) test liquids was observed. Moreover, the decrease in surface energy (46.95–24.45 mN/m) was also found to be inconsistent by increasing the molecular weight of polyols.

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