scholarly journals Synthesis of Monoacryloxypropyl-POSS-based Hybrid Epoxyacrylate Copolymers and Their Application in Thermally Curable Structural Self-Adhesive Tapes

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2058 ◽  
Author(s):  
Agnieszka Kowalczyk ◽  
Krzysztof Kowalczyk ◽  
Konrad Gziut
Keyword(s):  
Gel Permeation Chromatography ◽  
Transition Process ◽  
Chain Structure ◽  
Accelerated Ageing ◽  
Mechanical Resistance ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Hybrid Copolymers ◽  
Before And After ◽  
Thermal Stability Of

New organic-inorganic hybrid copolymers (EA-POSSs) based on butyl acrylate, glycidyl methacylate, hydroxybutyl acrylate, acryloiloxybenzophenone and acryloxypropyl-heptaisobutyl-POSS (A-POSS) were prepared via free-radical solution polymerization (FRP) and applied as a component of thermally curable structural self-adhesive tapes (SATs). The EA-POSS with 0.25, 0.5 or 1 mol % of A-POSS exhibited significantly higher dynamic viscosity (ca. +104%), Mw (+61%) and polydispersity (+109%; measured using gel permeation chromatography) as well as lower Tg value (−16 °C) in relation to the A-POSS-free copolymer (EA-0). Differential scanning calorimetry (DSC) measurements (one glass transition process) confirmed statistic chain structure of the EA-POSS materials. Replacement of EA-0 by the EA-POSS copolymers in a SATs recipe caused simultaneous improvement of their self-adhesive features, i.e., adhesion (+70%), tack (+21%) and cohesion (+1590%). Moreover, the POSS-based copolymers improved the shear strength of thermally cured Al/SAT/Al overlap joints; the best mechanical resistance (before and after accelerated ageing tests) was observed for the sample containing 0.5 mol % of A-POSS (an increment range of 50–294% in relation to the A-POSS-free joints). Thermogravimetric analysis (TGA) revealed markedly improved thermal stability of the A-POSS-based SATs as well.

Preparation and properties of fluorosilicone and fluorosilicone elastomer with various contents of trifluoropropyl groups

e-Polymers ◽  
2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Yan Cui ◽  
Wenge Jiang ◽  
Dongmei Li ◽  
Chengqun Niu ◽  
Shengyu Feng ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Ring Opening ◽  
Gel Permeation Chromatography ◽  
Scanning Calorimetry ◽  
Solvent Resistance ◽  
Glass Transition Temperatures ◽  
Methyl Vinyl ◽  
Dsc Measurements ◽  
Gel Permeation ◽  
Thermal Stability Of

AbstractPoly(dimethyl-methyltrifluoropropyl-methylvinyl)siloxanes (PFMVS) with various contents of trifluoropropyl groups were prepared by ring-opening copolymerization of 2,4,6-trimethyl-2,4,6-tris(3,3,3-trifluoropropyl) cyclotrisiloxane (D3F), octamethylcyclotetrasiloxane (D4) and 1,3,5,7-tetramethyl tetravinylcyclotetrasiloxane (D4Vi). All the polymers were characterized by IR, 1HNMR, 29SiNMR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements. The results show that methyltrifluoropropyl-siloxane units in the copolymer can disrupt the molecular regularity and lead to noncrystalline copolymers with low glasstransition temperatures. Moreover, the onset temperatures of thermal degradation and the glass transition temperatures of polymers decrease gradually with the content of trifluoropropyl groups increasing. Then the thermal stability and solvent resistance of elastomers based on PFMVSs were measured. The data of TGA indicate that the thermal stability of fluorosilicone elastomers are less than conventional methyl vinyl silicone rubber (MVQ), but the fluorosilicone elastomers have outstanding solvent resistance. The content of the trifluoropropyl groups influences the performances of elastomer to a certain degree.

scholarly journals Analysis of the Degradation During Melt Processing of PLA/Biosilicate® Composites

2019 ◽  
Vol 3 (2) ◽  
pp. 52 ◽  
Author(s):  
Eduardo H. Backes ◽  
Laís de N. Pires ◽  
Lidiane C. Costa ◽  
Fabio R. Passador ◽  
Luiz A. Pessan
Keyword(s):  
Molecular Weight ◽  
Gel Permeation Chromatography ◽  
Melt Processing ◽  
Poly Lactic Acid ◽  
Processing Route ◽  
Mechanical Resistance ◽  
Scanning Calorimetry ◽  
Oxidative Reactions ◽  
Bioactive Composites ◽  
Internal Mixer

Poly (lactic acid) (PLA)/bioactive composites are emerging as new biomaterials since it is possible to combine stiffness, mechanical resistance, and bioactive character of the bioglasses with conformability and bioabsorption of the PLA. In this study, PLA/Biosilicate® composites were prepared using a melt-processing route. The processability and properties were evaluated aiming to produce composites with bioactive properties. Two different PLA (PLA 2003D and PLA 4043D) were tested with the addition of 1 wt. % of Biosilicate®. Both materials presented a huge reduction in melt viscosity after internal mixer processing. The degradation effects of the addition of Biosilicate® in the PLAs matrices were evaluated using zeta potential tests that showed a very high liberation of ions, which catalyzes PLA thermo-oxidative reactions. To understand the extension of degradation effects during the processing, the composites were characterized using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and rheological tests. GPC results showed that PLA with the lowest residual acid content (RAC), PLA 2003D, presented higher thermal stability, higher molecular weight, and viscosity baseline compared to PLA 4043D. The composites showed a significant decrease in molecular weight for both PLA with the addition of Biosilicate®. TGA results showed that Biosilicate® might have reduced the activation energy to initiate thermodegradation reactions in PLAs and it occasioned a reduction in the Tonset by almost 40 °C. The DSC results showed that severe matrix degradation and the presence of bioglass did not significantly affect glass transition temperature (Tg), melting temperature (Tm) and crystallinity of PLAs, but it influenced cold crystallization peak (Tcc). In this way, the type of PLA used influences the processability of this material, which can make the production of filaments of this material for 3D printing unfeasible.

Glass Forming Ability and Crystallization Kinetics of Al-Mg-Ni-La Metallic Glasses

2014 ◽  
Vol 960-961 ◽  
pp. 161-164 ◽  
Author(s):  
Juan Mu ◽  
Hai Feng Zhang
Keyword(s):  
Crystallization Kinetics ◽  
Glass Forming Ability ◽  
Continuous Heating ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Glass Forming ◽  
Dsc Measurements ◽  
Mg Addition ◽  
Kinetics Of ◽  
Thermal Stability Of

Glass forming ability and crystallization kinetics of Al-Mg-Ni-La alloys have been investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The maximum thickness achievable in glasses of Al76Mg11Ni8La5and Al69Mg18Ni8La5ribbons were 200 and 120 μm, respectively. The crystallization temperature and peak temperature indicated by DSC measurements displayed dependence on the heating rate during continuous heating, and were coincident with Lanoka’s relationship. The activation energies for the crystallization reactionExwere obtained from the Kissinger’s equation. The results show the Mg addition is beneficial to the thermal stability of the amorphous phase.

The Influence of Gamma Radiation on the Glass Transition of Hydroxyapatite/Poly L-Lactide Composite

2007 ◽  
Vol 555 ◽  
pp. 497-502
Author(s):  
Dejan Miličević ◽  
S. Trifunović ◽  
N. Ignjatović ◽  
E. Suljovrujić
Keyword(s):  
Activation Energy ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Structural Relaxation ◽  
Absorbed Dose ◽  
Gel Permeation Chromatography ◽  
Chain Scission ◽  
Scanning Calorimetry ◽  
Dsc Measurements

Hydroxyapatite/poly L-lactide (HAp/PLLA) is a composite biomaterial which has been widely utilized for substitution and reparation of the hard bone tissue. It is well known that gamma irradiation has been successfully employed in the modification/sterilization of such porous composites and that it has advantages over other procedures. In this study, differential scanning calorimetry (DSC) measurements were made to investigate the influence of the radiation on glass transition behavior and structural relaxation, as well as to estimate the activation energy for this process. The apparent activation energy ΔH* for structural relaxation in the glass transition region was determined on the basis of the heating rate dependence of the glass transition temperature Tg. Furthermore, the results were correlated with those obtained by gel permeation chromatography (GPC). Our findings support the fact that the radiation-induced chain scission in the PLLA phase is the main reason for the decrease of the glass transition temperature and/or activation energy with the absorbed dose.

Detection of Phase Transition in Free-Cutting Al-Mg-Si Alloys by Resonant Ultrasound Spectroscopy

2014 ◽  
Vol 794-796 ◽  
pp. 21-26 ◽  
Author(s):  
Jitka Nejezchlebová ◽  
Hanuš Seiner ◽  
Miroslav Karlík
Keyword(s):  
Volume Fraction ◽  
Thermal Hysteresis ◽  
Transition Process ◽  
Transition Temperatures ◽  
Scanning Calorimetry ◽  
Resonant Ultrasound Spectroscopy ◽  
Dsc Measurements ◽  
Temperature Ranges ◽  
Small Volume Fraction ◽  
Resonant Ultrasound

The transition temperatures of small amounts of eutectic particles contained in free-cutting aluminum alloys (namely AA6262 and AA6023) are investigated in this paper. Detection of the transition temperatures by conventional differential scanning calorimetry (DSC) measurements is difficult because of the small volume fraction (~ 1wt.%) of the eutectic. On the other hand, the melting of the particles induces small changes of elastic moduli of the alloy, which can be sensitively measured by resonant acoustic methods, for example by resonant ultrasound spectroscopy (RUS). It is shown that the phase transitions of the particles correspond to well-detectable changes of the resonant spectrum, which enables a more detailed characterization of the transition process. A significant thermal hysteresis is observed between the cooling and the heating runs, and also the widths of the temperature ranges in which the transitions occur exhibit a strong melting/freezing asymmetry.

Preparation and Properties of UV-Curable Adhesives Based on Epoxy Acrylate Prepolymers

2011 ◽  
Vol 418-420 ◽  
pp. 1444-1447
Author(s):  
Yi Chi Chen ◽  
Tao He ◽  
Wei Yang ◽  
Li Qun Zhu ◽  
Wei Ping Li ◽  
...  
Keyword(s):  
Room Temperature ◽  
Uv Curing ◽  
Gel Permeation Chromatography ◽  
Epoxy Acrylate ◽  
Uv Curable ◽  
Gel Permeation ◽  
Before And After ◽  
Thermal Stability Of ◽  
Different Molecular Weight

Three kinds of commercially available epoxy acrylate reactive prepolymers with different molecular weight (MW) were used to formulate the UV-curable adhesives by addition of photo-initiator, reactive diluent, crosslinker and other additives as necessary. The MW of the said prepolymers were measured by gel permeation chromatography (GPC), while the structural characterization of the prepolymers before and after UV-curing was made by FTIR. Thermal stability of two kinds of UV-cured prepolymers with distinct MW and MW distribution was detected by thermogravimetric (TG) analysis.Lap shear strength of the adherents at different temperature were tested and compared with a known superior UV-curable adhesive (Loctite 3493). Adhesion strength of the adhesives at room temperature were all higher than 15 MPa which were more than the reported riveting intensity (10.3 MPa).

Evaluating efficacy of different UV-stabilizers/absorbers in reducing UV-degradation of lignin

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Saeid Nikafshar ◽  
Mojgan Nejad
Keyword(s):  
Lignin Degradation ◽  
Gel Permeation Chromatography ◽  
Wood Products ◽  
Uv Exposure ◽  
Resonance Spectroscopy ◽  
Uv Degradation ◽  
Scanning Calorimetry ◽  
Wood Coatings ◽  
Before And After ◽  
Uv Absorbers

Abstract Susceptibility of wood to UV degradation decreases the service life of wood products outdoors. Organic UV absorbers (UVAs) and hindered amine light stabilizers (HALSs), as well as inorganic UVAs, are added to coatings to improve the UV stability of coated-wood products. Although about 85% of UV radiation is absorbed by lignin in the wood, it is unclear which UV stabilizers can minimize lignin degradation. In this study, the photodegradation of softwood organosolv lignin was monitored over 35 days of UV exposure. Changes in lignin properties were assessed using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), gel permeation chromatography (GPC), and phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR). It was found that the aromatic rings of lignin underwent significant degradation, resulting in increased glass transition temperature and molecular weight of lignin. Subsequently, 18 different additives were mixed with lignin and exposed to UV irradiation. The analysis of samples before and after UV exposure with FTIR revealed that inorganic UVAs (cerium oxide and zinc oxide) and a mixture of organic UVAs and HALSs (T-479/T-292, T-5248, and T-5333) were the most effective additives in reducing lignin degradation. This study can help coating scientists to formulate more durable transparent exterior wood coatings.

scholarly journals Microstructures and Thermal Stability of the Metastable-Phase Precipitates Formed in an Al-Cu Alloy

2005 ◽  
Vol 475-479 ◽  
pp. 353-356 ◽  
Author(s):  
Sung Kyu Son ◽  
Mahoto Takeda ◽  
Takao Endo
Keyword(s):  
Vickers Microhardness ◽  
Early Stage ◽  
Metastable Phase ◽  
Peak Hardness ◽  
Precipitation Behavior ◽  
Scanning Calorimetry ◽  
Dsc Measurements ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Thermal Stability Of

The precipitation behavior in an Al-Cu alloy isothermally annealed at 373K～493K was studied, using the Vickers microhardness tests, Differential scanning calorimetry(DSC) and Transmission electron microscope(TEM) observations. An additional endothermic peak was found in DSC measurements which may be attributed to the θ″-phase independent from the formations of the G.P.(Ⅱ) and the θ′-phase at the aging temperatures. High resolution transmission electron microscopy (HRTEM) revealed that the G.P.(Ⅰ) is formed at a very early stage of isothermal aging at 463K. Comparing the Vickers microhardness and TEM images, it was concluded that G.P.(Ⅱ) is mainly responsible for the peak hardness.

Thermooxidative degradation of injection-moulded sepiolite/polyamide 66 nanocomposites

2014 ◽  
Vol 78 (5) ◽  
pp. 1227-1239 ◽  
Author(s):  
A. Yebra-Rodríguez ◽  
C. Fernández-Barranco ◽  
M. D. La Rubia ◽  
A. Yebra ◽  
A. B. Rodríguez-Navarro ◽  
...  
Keyword(s):  
Polymer Degradation ◽  
Treatment Temperature ◽  
Polymer Chains ◽  
Accelerated Ageing ◽  
Thermooxidative Degradation ◽  
X Ray Diffraction ◽  
Polyamide 66 ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Thermal Stability Of

AbstractClay/polymer nanocomposites (CPN) exhibit improved technical properties compared to their microand macro-counterparts. Nevertheless, thermal degradation of CPN may limit the applicability of these hybrid materials. In this paper accelerated ageing (110°C and 150°C) was performed in injection moulded pure polyamide 66 (PA66-S-0 samples) and polyamide 66 reinforced with 5 wt.% sepiolite (PA66-S-5 samples) CPN. Polymer degradation was monitored by the amount of newly formed carbonyl bonds. The carbonyl indices obtained indicate that degradation occurs to a greater extent as the temperature of the ageing process increases. Moreover, the degradation increases with time at the highest treatment temperature (150°C). On the other hand, the occurrence of carbonaceous silicates in the nanocomposite samples at high temperatures yields greater thermal stability of sepiolite/PA66 nanocomposites compared to pure PA66. Furthermore, the sepiolite nanofibres maintain their position in the reticulated semicrystalline structure. In agreement with those results, differential scanning calorimetry and X-ray diffraction analyses show that the motion of the amide groups in the polymer chains are constrained by the well dispersed sepiolite.

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