scholarly journals Influence of early thermal-oxidative ageing on the structure and properties of polyoxymethylene copolymer

2021 ◽  
Vol 8 (6) ◽  
pp. 210034
Author(s):  
Yuan-Jin Pang ◽  
Wen-Shuai Xu ◽  
Ben-Tengzi Yang ◽  
Hai-Ying Ni ◽  
Jun Chen
Keyword(s):  
Amorphous Region ◽  
Chain Scission ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Crystallinity Degree ◽  
Region I ◽  
The Difference ◽  
And Performance ◽  
Oxidative Ageing

Thermal-oxidative ageing of polyoxymethylene (POM) copolymer in the oven at 100°C for 1, 2, 3, 5, 7, 10, 14 and 21 days and the influence of early thermal-oxidative ageing on POM structure and properties were studied by means of wide-angle X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry and tensile test. Based on the results, we found that the early thermal-oxidative ageing of POM copolymer can be divided into three regions. The region I is the initial 3 days. In this region, some molecular chains rearranged, resulting in internal stress relaxation, increase of crystallinity degree and grain size due to the perfection of crystal structure; both extended chain crystal (ECC) and folded chain crystal (FCC) increased and ECC grew faster than FCC. The region II is from 3 days to 10 days, and in this region, chain scission took place in amorphous region and led to chemi-crystallization. The region III is after 10 days. In this region, the structure and performance of POM copolymer reached a stable situation at this stage. In this work, the difference between skin and core were also analysed.

Structure and performance of polybutene-1 pipes produced via mandrel rotation extrusion

2014 ◽  
Vol 34 (1) ◽  
pp. 15-22 ◽  
Author(s):  
Wei Liu ◽  
Qi Wang ◽  
Min Nie
Keyword(s):  
Rotation Speed ◽  
Processing System ◽  
Axial Direction ◽  
Amorphous Region ◽  
Thermal Shrinkage ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Extrusion Processing ◽  
And Performance ◽  
Mechanical Performances

Abstract In this article, a new rotational extrusion processing system was adopted for manufacturing of polybutene-1 (PB-1) pipes, and the effects of mandrel rotation speed on their structures and mechanical performances were studied. The experimental results showed that besides the conventional axial extrusion flow field, a hoop shear stress field imposed to the melt, which was generated by the introduction of mandrel rotation, could lead the combined stress apart from the axial direction of the pipes to induce the molecular orientation deviated from the axial direction. Thus, the axial orientation of PB-1 was restrained, which was revealed by thermal shrinkage measurements and polarized infrared spectra. Moreover, it was also found and confirmed by scanning electron microscopy and two-dimensional wide-angle X-ray diffraction that orientation mainly existed in the amorphous region rather than the crystal region. Differential scanning calorimetry tests showed that the mandrel rotation could facilitate the formation of more perfect crystals and higher crystallinity. As a result, compared with the PB-1 pipe produced by conventional extrusion, the hoop strength of the PB-1 pipes manufactured at a mandrel rotation speed of 8 rpm increased from 20.2 to 24.9 MPa, achieving a mechanical balance in both axial and hoop directions.

Study in performance and morphology of polyamide 12 produced by selective laser sintering technology

2018 ◽  
Vol 24 (5) ◽  
pp. 813-820 ◽  
Author(s):  
Junjie Wu ◽  
Xiang Xu ◽  
Zhihao Zhao ◽  
Minjie Wang ◽  
Jie Zhang
Keyword(s):  
Selective Laser Sintering ◽  
Polarized Light ◽  
Chain Scission ◽  
High Energy ◽  
Laser Sintering ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Content Type ◽  
X Ray ◽  
Polyamide 12

Purpose The purpose of this paper is to investigate the effect of selective laser sintering (SLS) method on morphology and performance of polyamide 12. Design/methodology/approach Crystallization behavior is critical to the properties of semi-crystalline polymers. The crystallization condition of SLS process is much different from others. The morphology of polyamide 12 produced by SLS technology was investigated using scanning electron microscopy, polarized light microscopy, differential scanning calorimetry, X-ray diffraction and wide-angle X-ray diffraction. Findings Too low fill laser power brought about bad fusion of powders, while too high energy input resulted in bad performance due to chain scission of macromolecules. There were three types of crystal in the raw powder material, denoted as overgrowth crystal, ring-banded spherulite and normal spherulite. Originality/value In this work, SLS samples with different sintering parameters, as well as compression molding sample for the purpose of comparison, were made to study the morphology and crystal structure of sintered PA12 in detail.

Effect of Modified NanoSiO2 Agents on the Morphologies and Performances of UHMWPE Microporous Membrane via Thermally Induced Phase Separation

2016 ◽  
Vol 848 ◽  
pp. 726-732 ◽  
Author(s):  
Rong Liu ◽  
Yan Wang ◽  
Jing Zhu ◽  
Zu Ming Hu ◽  
Jun Rong Yu
Keyword(s):  
Phase Separation ◽  
Water Flux ◽  
Microporous Membranes ◽  
Thermally Induced Phase Separation ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Thermally Induced ◽  
And Performance ◽  
Surface Modified ◽  
Ultra High Molecular Weight

The effects of Modified NanoSiO2 Agents on the morphology and performance of ultra-high-molecular weight polyethylene (UHMWPE) microporous membranes via thermally induced phase separation were investigated in this work. The NanoSiO2 was surface modified by silane coupling agent KH570 (KH570-NanoSiO2). Differential scanning calorimetry (DSC) and X-Ray Diffraction (XRD) were performed to obtain crystallization of UHMWPE/white oil/ KH570-NanoSiO2 doped system. The morphology and performance of the prepared UHMWPE microporous membranes were characterized with scanning electron microscopy (SEM) and microfiltration experiments. The results showed that the morphology of UHMWPE membrane could be disturbed by KH570-NanoSiO2. Porosity and the rejection of Bovine serum albumin (BSA) of the blend membrane increased with increasing concentration of Modified NanoSiO2, while the water flux slightly decreased.

scholarly journals Synthesis of Tungsten-Doped Vanadium Dioxide Using a Modified Polyol Method Involving 1-Dodecanol

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5384
Author(s):  
Yonghyun Lee ◽  
Sang Won Jung ◽  
Sang Hwi Park ◽  
Jung Whan Yoo ◽  
Juhyun Park
Keyword(s):  
Linear Growth ◽  
Mixing Ratio ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Metal Insulator ◽  
X Ray ◽  
Mixing Ratios ◽  
The Difference ◽  
Modified Polyol Method ◽  
Optimal Mixing

The doping of tungsten into VO2 (M) via a polyol process that is based on oligomerization of ammonium metavanadate and ethylene glycol (EG) to synthesize a vanadyl ethylene glycolate (VEG) followed by postcalcination was carried out by simply adding 1-dodecanol and the tungsten source tungstenoxytetrachloride (WOCl4). Tungsten-doped VEGs (W-VEGs) and their calcinated compounds (WxVO2) were prepared with varying mixing ratios of EG to 1-dodecanol and WOCl4 concentrations. Characterizations of W-VEGs by powder X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, and infrared and transmittance spectroscopy showed that tungsten elements were successfully doped into WxVO2, thereby decreasing the metal-insulator transition temperature from 68 down to 51 °C. Our results suggested that WOCl4 variously combined with 1-dodecanol might interrupt the linear growth of W-VEGs, but that such an interruption might be alleviated at the optimal 1:1 mixing ratio of EG to 1-dodecanol, resulting in the successful W doping. The difference in the solar modulations of a W0.0207VO2 dispersion measured at 20 and 70 °C was increased to 21.8% while that of a pure VO2 dispersion was 2.5%. It was suggested that WOCl4 coupled with both EG and 1-dodecanol at an optimal mixing ratio could improve the formation of W-VEG and WxVO2 and that the bulky dodecyl chains might act as defects to decrease crystallinity.

Structure and properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)/poly(L-lactic acid) quasi core/sheath melt-electrospun microfibers

2018 ◽  
Vol 89 (9) ◽  
pp. 1770-1781 ◽  
Author(s):  
Huaizhong Xu ◽  
Benedict Bauer ◽  
Masaki Yamamoto ◽  
Hideki Yamane
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Lactic Acid ◽  
Tensile Tests ◽  
Processing Parameters ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Diffraction Patterns

A facile route was proposed to fabricate core–sheath microfibers, and the relationships among processing parameters, crystalline structures and the mechanical properties were investigated. The compression molded poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)/poly(L-lactic acid) (PLLA) strip enhanced the spinnability of PHBH and the mechanical properties of PLLA as well. The core–sheath ratio of the fibers was determined by the prefab strip, while the PLLA sheath component did not completely cover the PHBH core component due to the weak interfacial tension between the melts of PHBH and PLLA. A rotational target was applied to collect aligned fibers, which were further drawn in a water bath. The tensile strength and the modulus of as-spun and drawn fibers increased with increasing the take-up velocities. When the take-up velocity was above 500 m/min, the jet became unstable and started to break up at the tip of the Taylor cone, decreasing the mechanical properties of the fibers. The drawing process facilitated the crystallization of PLLA and PHBH, and the tensile strength and the modulus increased linearly with the increasing the draw ratio. The crystal information displayed from wide-angle X-ray diffraction patterns and differential scanning calorimetry heating curves supported the results of the tensile tests.

scholarly journals Microstructure Evolution and Performance Improvement of Hypereutectic Al–Mg2Si Metallic Composite with Ca or Sb

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2714
Author(s):  
Min Zuo ◽  
Boda Ren ◽  
Zihan Xia ◽  
Wenwen Ma ◽  
Yidan Lv ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Nucleation Behavior ◽  
X Ray ◽  
Primary Mg2si ◽  
Before And After ◽  
And Performance ◽  
Hardness Values

In this article, the modification effects on Al–Mg2Si before and after heat treatment were investigated with Ca, Sb, and (Ca + Sb). In comparison with single Ca or Sb, the samples with composition modifiers (Ca + Sb) had the optimal microstructure. The sample with a molar ratio for Ca-to-Sb of 1:1 obtained relatively higher properties, for which the Brinell hardness values before and after heat treatment were remarkably increased by 31.74% and 28.93% in comparison with bare alloy. According to differential scanning calorimetry analysis (DSC), it was found that the nucleation behavior of the primary Mg2Si phase could be significantly improved by using chemical modifiers. Some white particles were found to be embedded in the center of Mg2Si phases, which were deduced to be Ca5Sb3 through X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM) analyses. Furthermore, Ca5Sb3 articles possess a rather low mismatch degree with Mg2Si particles based on Phase Transformation Crystallography Lab software (PTCLab) calculation, meaning that the efficient nucleation capability of Ca5Sb3 for Mg2Si particles could be estimated.

scholarly journals Lipase mediated synthesis of polycaprolactone and its silica nanohybrid

2019 ◽  
Vol 91 (6) ◽  
pp. 957-965
Author(s):  
Meltem Akkulak ◽  
Yasemin Kaptan ◽  
Yasar Andelib Aydin ◽  
Yuksel Avcibasi Guvenilir
Keyword(s):  
Average Molecular Weight ◽  
Proton Nuclear Magnetic Resonance ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Structural Investigations ◽  
Crystallinity Degree ◽  
Molecular Weights ◽  
H Nmr

Abstract In this study, rice husk ash (RHA) silanized with 3-glycidyloxypropyl trimethoxysilane was used as support material to immobilize Candida antarctica lipase B. The developed biocatalyst was then utilized in the ring opening polymerization (ROP) of ε-caprolactone and in situ development of PCL/Silica nanohybrid. The silanization degree of RHA was determined as 4 % (w) by thermal gravimetric analysis (TGA). Structural investigations and calculation of molecular weights of nanohybrids were realized by proton nuclear magnetic resonance (1H NMR). Crystallinity was determined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Scanning Electron Microscopy (SEM) was used for morphological observations. Accordingly, the PCL composition in the nanohybrid was determined as 4 %, approximately. Short chained amorphous PCL was synthesized with a number average molecular weight of 4400 g/mol and crystallinity degree of 23 %. In regards to these properties, synthesized PCL/RHA composite can find use biomedical applications.

Novel Aceclofenac cocrystals with l-Cystine: Virtual coformer screening, mechanochemical synthesis, and physicochemical investigations

2020 ◽  
Vol 17 ◽  
Author(s):  
Saroj Kumar ◽  
Amresh Gupta ◽  
Rammani Prasad ◽  
Satyawan Singh
Keyword(s):  
Dissolution Rate ◽  
Mechanochemical Synthesis ◽  
Screening Method ◽  
Research Work ◽  
Crystalline Solid ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Grinding Method ◽  
Enhanced Solubility ◽  
And Performance

Aim: Current work focuses on the improvement of solubility and dissolution of ACF by the cocrystal approach. Background: Aceclofenac (ACF) is one of the commonly used nonsteroidal anti-inflammatory drug (NSAID) representing the variety of therapeutic applications including management of pain, inflammation, rheumatoid arthritis, and osteoarthritis, etc. But very low solubility and dissolution rate of ACF compromise its therapeutic utility. Now a day's cocrystallization technique has emerged as a novel technique for modulation of said problems. Objective: The Specific objectives of this research work were mechanochemical synthesis, characterization, and performance evaluation of aceclofenac cocrystal. Method: ACF was screened with various pharmaceutically acceptable coformers (Selected from GRAS and EAFUS list) using MOPAC software and physical screening method to find out novel cocrystals of ACF with enhanced solubility and dissolution rate. Novel cocrystals (multi-component crystalline solid) of ACF with l-cystine were prepared by neat grinding method and by liquid assisted grinding method. The synthesized cocrystals (ACF-l-CYS NG and ACF-l-CYS LAG) were characterized carefully by differential scanning calorimetry (DSC), infrared spectroscopy (IR), and powder X-ray diffraction (PXRD) to verify the formation of the cocrystals. Pharmaceutically significant properties such as powder dissolution rate, solubility, and stability of the prepared cocrystals were evaluated. Results: Compared to pure ACF, the prepared cocrystals showed superior solubility and dissolution rate. The prepared cocrystals were found to be stable and non-hygroscopic under study conditions. Conclusion: The cocrystallization technique was successfully utilized to increase the solubility and dissolution rate of aceclofenac.

Chalcogenide glasses Ge–Sn–Se, Ge–Se–Te, and Ge–Sn–Se–Te for infrared optical fibers

1990 ◽  
Vol 5 (6) ◽  
pp. 1215-1223 ◽  
Author(s):  
I. Haruvi-Busnach ◽  
J. Dror ◽  
N. Croitoru
Keyword(s):  
Differential Scanning Calorimetry ◽  
Optical Fibers ◽  
Chalcogenide Glasses ◽  
Glass Composition ◽  
Amorphous Region ◽  
Maximum Power Density ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Ftir Spectrometry

Chalcogenide glasses of the systems Ge–Sn–Se, Ge–Se–Te, and Ge–Sn–Se–Te have been prepared. Several compositions were found suitable for drawing fibers for CO2 laser radiation (λ = 10.6 μm) transmission. The glasses were characterized by x-ray diffraction, DSC (Differential Scanning Calorimetry), SEM with EDX analysis, FTIR spectrometry, density, and microhardness measurements. The glass transition temperature and microhardness of Ge–Se–Sn and Ge–Sn–Se–Te glasses decreased with increasing Sn content, for most of the samples. The region of high IR transparency of Ge–Se–Sn, Ge–Se–Te, and Ge–Sn–Se–Te glasses was slightly expanded (1–2 μm) toward longer wavelengths, compared to Ge–Se glasses, mainly for the glasses containing 70 at.% Se. The intensity of the impurity absorption peak of Ge–O (at λ ∼ 12.8 μm), which usually appears in Ge–Se glasses, was reduced or absent in Ge–Sn–Se–Te glasses. The best fibers were produced with the glass composition Ge–0.8Sn0.2Se3.5Te0.5. An attenuation of 20 dB/m at 10.6 μm, and a transmitted maximum power density of 2.4 ⊠ 106 W/m2 were measured. The mechanical and optical characteristics of these glasses have been related to the glasses structure. Corresponding to the reduced masses of the bonds formed in the Ge–Sn–Se–Te system (in the amorphous region), it is expected that the multiphonon edge is slightly shifted. As a consequence, as was measured, the transparency region has been expanded by less than 2 μm toward longer wavelengths.

Structure and Performance of PP Porous Membrane Prepared with Adipic Acid and NA-40 as Nucleating Agent via TIPS

2016 ◽  
Vol 848 ◽  
pp. 733-737
Author(s):  
Hui Xia Xuan ◽  
Chun Ju He
Keyword(s):  
Adipic Acid ◽  
Water Flux ◽  
Nucleating Agent ◽  
Porous Membrane ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Sem Images ◽  
Thermally Induced ◽  
Cooling Temperature ◽  
And Performance

Polypropylene (PP) membranes were respectively prepared using adipic acid (APA) and Sorbitol (NA-40) as nucleating agent via thermally induced phase separation (TIPS) method. The effects of nucleating agent content and cooling temperature on the structure and performance of membrane were investigated using scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). WAXD spectrogram indicates that three kinds of α, β and γ-form crystal were formed in this preparation process and the relative content of β-form crystal in membrane prepared by NA-40 system is higher than that of membrane formed by adipic acid. SEM images show that porous structure and cellular structure were observed on the surface and cross-section of membrane. The water flux, tensile strength and elongation increase with the addition of nucleating agent content and decrease with cooling temperature rising. This paper aims to choose proper nucleating agent NA-40 and coagulation temperature to improve the properties of PP membranes.

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