Syntheses of novel benzoxazines having vinyl groups and thermal properties of the thermosets

2012 ◽  
Vol 24 (8) ◽  
pp. 765-774 ◽  
Author(s):  
Tsutomu Takeichi ◽  
Soulideth Thongpradith ◽  
Shoko Hirai ◽  
Tomomi Takiguchi ◽  
Takehiro Kawauchi
Keyword(s):  
Thermal Properties ◽  
Ring Opening ◽  
Exothermic Peak ◽  
Thermal Cure ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Chemical Structures ◽  
Polymerization Behavior ◽  
Chain Polymerization ◽  
Vinyl Group

Novel benzoxazines having vinyl groups were synthesized from phenol or bisphenol A, 3- or 4-vinylaniline and paraformaldehyde. The chemical structures of the monomers were confirmed by Fourier transform infrared and 1H-NMR analyses. The polymerization behavior of the monomers was monitored by differential scanning calorimetry. Exothermic peak of the monomers appeared in the range of 219–252 °C, due to the chain polymerization of the vinyl group and the ring-opening polymerization of benzoxazine occurring at the same temperature range. The thermal cure of the monomers afforded polybenzoxazines that have higher thermal properties than those from typical benzoxazines without vinyl groups. For example, glass transition temperature ( Tg) increased for 40 to 100 °C by the introduction of vinyl groups, the highest Tg being observed at 290 °C. The 5% weight loss temperature determined by thermogravimetric analysis also increased by the introduction of vinyl groups.

Thermal properties of polybenzoxazine exhibiting improved toughness: Blending with cyclodextrin and its derivatives

2021 ◽  
pp. 095400832110130
Author(s):  
Hailong Li ◽  
Sipei Zhao ◽  
Li Pei ◽  
Zihe Qiao ◽  
Ding Han ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Hydrogen Bonds ◽  
High Performance ◽  
Practical Application ◽  
Scanning Calorimetry ◽  
Thermoset Resins ◽  
Chemical Structures ◽  
Microscopy Techniques ◽  
Fractured Surface ◽  
Scanning Electron

Polybenzoxazines are emerging as a class of high-performance thermoset polymers that can find their applications in various fields. However, its practical application is limited by its low toughness. The cyclic β-cyclodextrin and a newly synthesized derivative (β-cyclodextrin-MAH) were separately blended with benzoxazine to improve the toughness of polybenzoxazine. The results revealed that the maximum impact strength of the blend was 12.24 kJ·m−2 and 14.29 kJ·m−2 when 1 wt.% of β-Cyclodextrin and β-Cyclodextrin-MAH, respectively, were used. The strengths were 53% and 86% higher than that of pure polybenzoxazine. The curing reaction, possible chemical structures, and fractured surface were examined using differential scanning calorimetry, Fourier transform infrared spectroscopy, and scanning electron microscopy techniques to understand the mechanism of generation of toughness. The results revealed that the sea-island structure and the presence of hydrogen bonds between polybenzoxazine and β-cyclodextrin and β-cyclodextrin-MAH resulted in the generation of toughness. Furthermore, the curves generated during thermogravimetric analysis did not significantly change, revealing the good thermal properties of the system. The phase-separated structure and the hydrogen bonds present in the system can be exploited to prepare synergistically tough polybenzoxazine exhibiting excellent thermal properties. This can be a potential way of modifying the thermoset resins.

Characterization of bi-layered magnetic nanoparticles synthesized via two-step surface-initiated ring-opening polymerization

2015 ◽  
Vol 87 (11-12) ◽  
pp. 1085-1097 ◽  
Author(s):  
Li Wang ◽  
Stefan Baudis ◽  
Karl Kratz ◽  
Andreas Lendlein
Keyword(s):  
Magnetic Nanoparticles ◽  
Ring Opening ◽  
Average Molecular Weight ◽  
Polymer Networks ◽  
Gel Permeation Chromatography ◽  
Degree Of Crystallinity ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Transmission Electron

AbstractA versatile strategy to integrate multiple functions in a polymer based material is the formation of polymer networks with defined nanostructures. Here, we present synthesis and comprehensive characterization of covalently surface functionalized magnetic nanoparticles (MNPs) comprising a bi-layer oligomeric shell, using Sn(Oct)2 as catalyst for a two-step functionalization. These hydroxy-terminated precursors for degradable magneto- and thermo-sensitive polymer networks were prepared via two subsequent surface-initiated ring-opening polymerizations (ROPs) with ω-pentadecalactone and ε-caprolactone. A two-step mass loss obtained in thermogravimetric analysis and two distinct melting transitions around 50 and 85°C observed in differential scanning calorimetry experiments, which are attributed to the melting of OPDL and OCL crystallites, confirmed a successful preparation of the modified MNPs. The oligomeric coating of the nanoparticles could be visualized by transmission electron microscopy. The investigation of degrafted oligomeric coatings by gel permeation chromatography and 1H-NMR spectroscopy showed an increase in number average molecular weight as well as the presence of signals related to both of oligo(ω-pentadecalactone) (OPDL) and oligo(ε-caprolactone) (OCL) after the second ROP. A more detailed analysis of the NMR results revealed that only a few ω-pentadecalactone repeating units are present in the degrafted oligomeric bi-layers, whereby a considerable degree of transesterification could be observed when OPDL was polymerized in the 2nd ROP step. These findings are supported by a low degree of crystallinity for OPDL in the degrafted oligomeric bi-layers obtained in wide angle X-ray scattering experiments. Based on these findings it can be concluded that Sn(Oct)2 was suitable as catalyst for the preparation of nanosized bi-layered coated MNP precursors by a two-step ROP.

scholarly journals Analysis of Bio-Based Fatty Esters PCM’s Thermal Properties and Investigation of Trends in Relation to Chemical Structures

2019 ◽  
Vol 9 (2) ◽  
pp. 225 ◽  
Author(s):  
Rebecca Ravotti ◽  
Oliver Fellmann ◽  
Nicolas Lardon ◽  
Ludger Fischer ◽  
Anastasia Stamatiou ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Phase Change ◽  
Energy Demand ◽  
Phase Change Materials ◽  
Arachidic Acid ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
Fatty Esters ◽  
Latent Heat Storage ◽  
Chemical Structures

As global energy demand increases while primary sources and fossil fuels’ availability decrease, research has shifted its focus to thermal energy storage systems as alternative technologies able to cover for the mismatch between demand and supply. Among the different phase change materials available, esters possess particularly favorable properties with reported high enthalpies of fusion, low corrosivity, low toxicity, low supercooling, thermal and chemical stability as well as biodegradability and being derived from renewable feedstock. Despite such advantages, little to no data on the thermal behavior of esters is available due to low commercial availability. This study constitutes a continuation of previous works from the authors on the investigation of fatty esters as novel phase change materials. Here, methyl, pentyl and decyl esters of arachidic acid, and pentyl esters of myristic, palmitic, stearic and behenic acid are synthesized through Fischer esterification with high purities and their properties are studied. The chemical structures and purities are confirmed through Attenuated Total Reflectance Infrared Spectroscopy, Gas Chromatography coupled with Mass Spectroscopy and Nuclear Magnetic Resonance Spectroscopy, while the determination of the thermal properties is performed through Differential Scanning Calorimetry and Thermogravimetric Analysis. In conclusion, some correlations between the melting temperatures and the chemical structures are discovered, and the fatty esters are assessed based on their suitability as phase change materials for latent heat storage applications.

scholarly journals Synthesis and Characterization of Polycarbonate Copolymers Containing Benzoyl Groups on the Side Chain for Scratch Resistance

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Hohyoun Jang ◽  
Jaeseong Ha ◽  
Jiho Yoo ◽  
Jaeseung Pyo ◽  
Kunyoung Choi ◽  
...  
Keyword(s):  
Methylene Chloride ◽  
Water Drop ◽  
Scratch Resistance ◽  
Scanning Calorimetry ◽  
Force Microscopy ◽  
H Nmr ◽  
Chemical Structures ◽  
Atomic Force ◽  
Rearrangement Reaction ◽  
Surface Morphologies

The purpose of this study was to enhance the scratch resistance of polycarbonate copolymer by using 3,3′-dibenzoyl-4,4′-dihydroxybiphenyl (DBHP) monomer, containing benzoyl moieties on the ortho positions. DBHP monomer was synthesized from 4,4′-dihydroxybiphenyl and benzoyl chloride, followed by the Friedel-Craft rearrangement reaction with AlCl3. The polymerizations were conducted following the low-temperature procedure, which is carried out in methylene chloride by using triphosgene, triethylamine, bisphenol-A, and DBHP. The chemical structures of the polycarbonate copolymers were confirmed by1H-NMR. The thermal properties of copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry, and also surface morphologies were assessed by atomic force microscopy. The scratch resistance of homopolymer film (100 μm) changed from 6B to 1B, and the contact angle of a sessile water drop onto the homopolymer film also increased.

scholarly journals Synthesis of New Imidazolidine and Tetrahydropyrimidine Derivatives

2014 ◽  
Vol 2014 ◽  
pp. 1-4 ◽  
Author(s):  
Hamid Beyzaei ◽  
Reza Aryan ◽  
Zahra Keshtegar
Keyword(s):  
Ring Opening ◽  
Reaction Times ◽  
Reaction Conditions ◽  
Ir Spectrometry ◽  
H Nmr ◽  
Chemical Structures ◽  
Thioamide Group ◽  
Solvent Free Conditions ◽  
Ft Ir ◽  
C Nmr

Synthesis of new imidazolidine and tetrahydropyrimidine derivatives 3a, b and 4a–c as cyclic 1,3-diamines under two reaction conditions (A and B) is described. Under reaction conditions-A, a suspension of (E)-2-cyano-2-(oxazolidin-2-ylidene)ethanethioamide 1 (1 eq.) and diaminoalkanes 2a–e (2 eq.) in absolute ethanol is heated under reflux for 16–22 h to afford 3a, b and 4a–c. Alternatively, under reaction conditions-B, a solution of thioamide 1 (1 eq.) in diaminoalkanes 2a–e (3 eq.) is stirred under solvent-free conditions at room temperature for 3 days to give desired products. Reaction conditions-A for having higher yields, shorter reaction times, and required less diamines is more effective than reaction conditions-B. Oxazolidine ring opening is observed by reacting compound 1 with all of the diamines 2a–e, but the thioamide group only reacts with nonbulky diamines 2a, b. The chemical structures of novel compounds were confirmed by 1H NMR, 13C NMR, elemental analysis, and FT-IR spectrometry.

scholarly journals Thermal properties of flax fiber scoured by different methods

2015 ◽  
Vol 19 (3) ◽  
pp. 939-945 ◽  
Author(s):  
Dong Zheng ◽  
Ruo-Yao Ding ◽  
Zheng Lei ◽  
Zhang Xingqun ◽  
Yu Chong-Wen
Keyword(s):  
Thermal Properties ◽  
Thermal Behavior ◽  
Value Added ◽  
Exothermic Peak ◽  
Endothermic Peak ◽  
Scanning Calorimetry ◽  
Volatile Products ◽  
Third Stage ◽  
Thermal Stability Of ◽  
Thermal Gravity Analyzer

Thermal properties of flax roves untreated and treated were characterized by differential scanning calorimetry (DSC) and thermal gravity analyzer (TGA) in order to understand their thermal behavior in more detail and to evaluate the effect of scouring processing on the thermal behavior. Flax roves were treated with six kinds of methods including biological scouring, one bath, two bath, bleaching, alkali scouring and industry chemical scouring as standards. Results showed that all treatments improved thermal stability of flax roves. The results indicated that glass transition temperature (Tg) decreased after scouring besides the sample by directly bleaching. It is more difficult to determine the endothermic peak of flax treated by chemical scouring in industry because it takes a very flat course. A distinct endothermic peak was observed for the untreated flax rove, while a distinct exothermic peak in different temperature interval was revealed for other four treated flax rove samples. For TGA analysis, thermal degradation of flax roves studied consists of three regions of the initial, main, and char decomposition, and the third stage consists of secondary weight loss and carbonization for flax roves with biological scouring, one-bath and two-bath. Besides, different residue left indicates that the bio-scoured flax roves are lost with volatile products and does not contribute to char formation. These results provide valuable preferences for mechanism and top value added application of bio-scouring in flax roves.

scholarly journals 1-n-Butyl-3-methylimidazolium-2-carboxylate: a versatile precatalyst for the ring-opening polymerization of ε-caprolactone and rac-lactide under solvent-free conditions

2013 ◽  
Vol 9 ◽  
pp. 647-654 ◽  
Author(s):  
Astrid Hoppe ◽  
Faten Sadaka ◽  
Claire-Hélène Brachais ◽  
Gilles Boni ◽  
Jean-Pierre Couvercelle ◽  
...  
Keyword(s):  
Differential Scanning Calorimetry ◽  
Ring Opening ◽  
Gel Permeation Chromatography ◽  
Ring Opening Polymerization ◽  
Solvent Free ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Solvent Free Conditions ◽  
Gel Permeation

The ring-opening polymerization of ε-caprolactone (ε-CL) and rac-lactide (rac-LA) under solvent-free conditions and using 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIM-2-CO2) as precatalyst is described. Linear and star-branched polyesters were synthesized by successive use of benzyl alcohol, ethylene glycol, glycerol and pentaerythritol as initiator alcohols, and the products were fully characterized by 1H and 13C{1H} NMR spectroscopy, gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). BMIM-2-CO2 acts as an N-heterocyclic carbene precursor, resulting from in situ decarboxylation, either by heating under vacuo (method A) or by addition of NaBPh4 (method B). Possible catalytic and deactivation mechanisms are proposed.

Novel surface treatment for natural fiber composites

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744092 ◽  
Author(s):  
Wendy Zhang ◽  
Xiaowen Yuan
Keyword(s):  
Ring Opening ◽  
Natural Fiber ◽  
Fiber Composites ◽  
Proton Nuclear Magnetic Resonance ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Dsc Studies ◽  
Flax Fibers ◽  
H Nmr

Poly(lactide) (PLA) — flax fibers stereocomplex composites were prepared by casting commercial poly(L-lactide) (PLA) and flax-g-poly(D-lactide) (flax-g-PDLA), where flax-g-PDLA was synthesized via ring-opening polymerization. Successful surface grafting was revealed by Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy, wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC) studies. DSC results showed that stereocomplex crystallites formed between the PLA matrix and flax-g-PDLA, resulting in good fiber/PLA interfacial adhesion.

scholarly journals Desiccation sensitivity of wild Castanea mollissima Blume determined by differential scanning calorimetry

2020 ◽  
Vol 49 (4) ◽  
pp. 975-980
Author(s):  
Biao Han ◽  
Lu Lu ◽  
Su-Juan Guo ◽  
Wen-Qing Li ◽  
Xiao-Man Xie
Keyword(s):  
Thermal Properties ◽  
Moisture Content ◽  
Water Content ◽  
Exothermic Peak ◽  
Onset Temperature ◽  
Unfrozen Water ◽  
Scanning Calorimetry ◽  
Moisture Contents ◽  
Unfrozen Water Content ◽  
Castanea Mollissima

Thermal properties of wild Castanea mollissima seeds embryos with different moisture contents, and the optimal moisture contents for cryopreservation were studied. Seeds of similar size and weight (3.5 ± 0.3g) were put in silica gel at 0 to 7 days, embryo moisture content, viability and thermal properties were measured everyday. The results showed that the onset temperature and the crystallization peak of the mean enthalpy decreased with the decrease of embryo moisture content. Exothermic peak disappeared when the seeds were dried for 4 days, with an embryo moisture content of 0.45 ± 0.15 gH2O/g dw. The unfrozen water content (WCu) was 0.247 gH2O/g dw. The optimal water content was found to be 0.45 ± 0.15 gH2O/g dw, with the survival of 76.2%. Castanea mollissima embryonic axes dehydration needs comprehensive consideration of exothermic peak, unfrozen water content, onset temperature and viability loss.

Preparation and Characterization of Dioxanone and Poly(dioxanone)

2013 ◽  
Vol 711 ◽  
pp. 22-25
Author(s):  
Kui Lin Deng ◽  
Wen Hui Jin ◽  
Fu Chen Zhang ◽  
Chun Xiu Li ◽  
Hui Juan Shen ◽  
...  
Keyword(s):  
Ring Opening ◽  
Raw Materials ◽  
Copper Chromite ◽  
Copper Nitrate ◽  
Ring Opening Polymerization ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Dsc Measurements ◽  
Ammonium Dichromate

In this paper, the ammonium dichromate and copper nitrate were used as raw materials to prepare the copper chromite, and nanocopper chromite as a catalyst was used to synthesize the monomer dioxanone in diethylene glycol dehydrogenation. Under the strict conditions of no water and no oxygen, the stannous octoate was selected to catalyze ring-opening polymerization of the dioxanone to prepare the polydioxanone. And dioxanone and its polymers were characterized with IR spectroscopy,1H NMR spectroscopy, thermogravimetric analysis (TG) and differential scanning calorimetry (DSC ) measurements.

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