Polyethylene glycol oligomers as siloxane modificators in consolidation of carbonate stones

2016 ◽  
Vol 88 (12) ◽  
pp. 1117-1128 ◽  
Author(s):  
Bruno Sena da Fonseca ◽  
Susana Piçarra ◽  
Ana Paula Ferreira Pinto ◽  
Maria de Fátima Montemor
Keyword(s):  
Molecular Weight ◽  
Polyethylene Glycol ◽  
Carboxylic Acid ◽  
Sol Gel ◽  
Silica Matrix ◽  
Strength Increase ◽  
Molecular Weights ◽  
Uniform Strength ◽  
End Groups ◽  
Stone Consolidants

AbstractThe overall performance of alkoxysilanes as stone consolidants is constrained by stone mineralogy (particularly in the carbonate varieties) and by their tendency to crack during drying. In an attempt to overcome these problems, polyethylene glycol “chains” with two carboxylic acid end-groups (PEG-CA) were introduced in siloxane sols obtained by sol-gel chemistry using tetraethoxysilane (TEOS) as precursor. Different pre-condensation degrees (by varying the stirring times of sol-gel reaction: 10 min, 2, and 24 h) and PEG-CA chains with different molecular weights were studied as variables affecting the initial efficacy of the consolidants when applied into a limestone. The sol containing siloxanes with the lowest pre-condensation degree (10 min stirring) was quite susceptible to the carbonate media and thus a poor consolidation was achieved. The sol with the highest pre-condensation degree (24 h stirring) together with the PEG-CA chains with intermediate molecular weight produced significant and uniform strength gains along the stone depth. The consolidation also showed to be highly dependent on the molecular weight of the PEG-CA chains, the PEG-CA with highest molecular weight produced a non-uniform strength increase with potential harmful side effects. The results confirmed the role of carboxylic acid end-groups as efficient sol-gel catalysts and their ability to be incorporated into the silica matrix in the presence of carbonate stone.

scholarly journals Synthesis, Structural, Morphological and Thermal Characterization of Five Different Silica-Polyethylene Glycol-Chlorogenic Acid Hybrid Materials

Polymers ◽  
2021 ◽  
Vol 13 (10) ◽  
pp. 1586
Author(s):  
Michelina Catauro ◽  
Pavel Šiler ◽  
Jiří Másilko ◽  
Roberta Risoluti ◽  
Stefano Vecchio Ciprioti
Keyword(s):  
Polyethylene Glycol ◽  
Chlorogenic Acid ◽  
Hybrid Materials ◽  
Sol Gel ◽  
Antibacterial Properties ◽  
Silica Matrix ◽  
Sem Images ◽  
Fixed Amount ◽  
Organic Components ◽  
Free Material

The present study investigated the structure, morphology, thermal behavior, and bacterial growth analysis of novel three-component hybrid materials synthesized by the sol-gel method. The inorganic silica matrix was weakly bonded to the network of two organic components: a well-known polymer such as polyethylene glycol (PEG, average molar mass of about 4000 g/mol), and an antioxidant constituted by chlorogenic acid (CGA). In particular, a first series was made by a 50 wt% PEG-based (CGA-free) silica hybrid along with two 50 wt% PEG-based hybrids containing 10 and 20 wt% of CGA (denoted as SP50, SP50C10 and SP50C20, respectively). A second series contained a fixed amount of CGA (20 wt%) in silica-based hybrids: one was the PEG-free material (SC20) and the other two contained 12 and 50 wt% of PEG, respectively (SP12C20 and SP50C20, respectively), being the latter already included in the first series. The X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images of freshly prepared materials confirmed that all the materials were amorphous and homogeneous regardless of the content of PEG or CGA. The thermogravimetric (TG) analysis revealed a higher water content was adsorbed into the two component hybrids (SP50 and SC20) because of the availability of a larger number of H-bonds to be formed with water with respect to those of silica/PEG/CGA (SPC), where silica matrix was involved in these bonds with both organic components. Conversely, the PEG-rich materials (SP50C10 and SP50C20, both with 50 wt% of the polymer) retained a lower content of water. Decomposition of PEG and CGA occurred in almost the same temperature interval regardless of the content of each organic component. The antibacterial properties of the SiO2/PEG/CGA hybrid materials were studied in pellets using either Escherichia coli and Enterococcus faecalis, respectively. Excellent antibacterial activity was found against both bacteria regardless of the amount of polymer in the hybrids.

Structural studies of oligosilanes produced by catalytic dehydrogenative coupling of primary organosilanes

1987 ◽  
Vol 65 (8) ◽  
pp. 1804-1809 ◽  
Author(s):  
C. Aitken ◽  
J. F. Harrod ◽  
U. S. Gill
Keyword(s):  
Molecular Weight ◽  
Nuclear Magnetic Resonance ◽  
Gel Permeation Chromatography ◽  
Structural Studies ◽  
Molecular Weights ◽  
Molecular Weight Distributions ◽  
Dehydrogenative Coupling ◽  
Weight Distributions ◽  
Gel Permeation ◽  
End Groups

The structures of some poly(organosilylenes), [Formula: see text] (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed.

Effects of poly(ethylene glycol) additive molecular weight on the microstructure and properties of sol-gel-derived lead zirconate titanate thin films

2003 ◽  
Vol 18 (3) ◽  
pp. 737-741 ◽  
Author(s):  
Shuhui Yu ◽  
Kui Yao ◽  
Santiranjan Shannigrahi ◽  
Francis Tay Eng Hock
Keyword(s):  
Thin Films ◽  
Molecular Weight ◽  
Ethylene Glycol ◽  
Lead Zirconate Titanate ◽  
Sol Gel ◽  
Lead Zirconate ◽  
Poly Ethylene Glycol ◽  
Molecular Weights ◽  
Zirconate Titanate ◽  
Poly Ethylene

Poly(ethylene glycol) (PEG) additives with different molecular weights were used to modify sol-gel precursor solutions for preparing lead zirconate titanate (PZT) thin films. The morphology, crystalline structure, and mechanical and electrical properties of the films were characterized. The relationship between the characteristics of the films and the molecular weight of PEG was investigated. It was observed that the PEG eliminated cracking of the films during multiple pyrolysis treatments. However, with the increase of the PEG molecular weight, the films became less dense, which led to decreased Young's modulus and dielectric constant and increased coercive field. Our experiments showed that films prepared from sols modified by PEG with a molecular weight of 200 exhibited a dense morphology and excellent mechanical and electric properties without cracking.

PEG Molecular Weight Effects on Physical and Mechanical Properties of ETICS Plaster, Hardening at Lowered Positive and Small Negative Temperatures

2014 ◽  
Vol 1004-1005 ◽  
pp. 1482-1485 ◽  
Author(s):  
Stanislav Pashkevich ◽  
Andrey Pustovgar ◽  
Aleksey Eremin ◽  
Aleksey Adamtsevich ◽  
Sergey Nefedov
Keyword(s):  
Mechanical Properties ◽  
Molecular Weight ◽  
Compressive Strength ◽  
Polyethylene Glycol ◽  
Physical And Mechanical Properties ◽  
Negative Temperature ◽  
Polystyrene Foam ◽  
Molecular Weights ◽  
Negative Temperatures

The paper presents the influence of polyethylene glycol additives wit h molecular weights of 2000... 6000 on basic physical and mechanical properties of plaster hardening at low positive and negative temperature s . The dependence of adhesion s trength to the polystyrene foam as well as compressive strength of plaster hardening at tempe rature s (+5... -10) oC on PEG molecular weight was established.

scholarly journals A Comparative Study on Magnetostructural Properties of Barium Hexaferrite Powders Prepared by Polyethylene Glycol

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Zehra Durmus
Keyword(s):  
Polyethylene Glycol ◽  
Magnetic Measurements ◽  
Sol Gel ◽  
Barium Hexaferrite ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Molar Ratio ◽  
Molecular Weights ◽  
Metal Nitrates ◽  
Gel Combustion

Nanocrystalline particles of barium hexaferrite were synthesized by a sol-gel combustion route using nitrate-citrate gels prepared from metal nitrates and citric acid solutions with Fe/Ba molar ratio 12. The present paper aims to study the effect of addition of polyethylene glycol (PEG) solutions with different molecular weights (MW: 400, 2000, and 10.000 g/mol) on magnetostructural properties of barium hexaferrite. The formation of the barium hexaferrite was inspected using X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) analysis, thermogravimetric (TGA) analysis, scanning electron microscopy (SEM) analysis and vibrating sample magnetometer (VSM) analysis for magnetic measurements.

scholarly journals Effect of Different Molecular Weight and Concentration of Polyethylene Glycol (PEG) on Tensile and Morphology of Sago Starch Film

2021 ◽  
Vol 16 ◽  
pp. 1-10
Author(s):  
Norzita Yacob
Keyword(s):  
Molecular Weight ◽  
Tensile Strength ◽  
Polyethylene Glycol ◽  
Tensile Stress ◽  
Sago Starch ◽  
Elongation At Break ◽  
Molecular Weights ◽  
Peg 4000 ◽  
Starch Films ◽  
Ftir Technique

Sago starch is a seasonal based plantation and widely found in Asia country. Its application mainly in cooking such as biscuits and as a thickener in jellies. To further utilize its application, bioplastic from sago starch was developed. In this study, sago starch films were prepared through a blending and casting method using polyethylene glycol (PEG) as a plasticizer by varying its molecular weights and concentrations. The interaction between starch and PEG in the blend was studied using FTIR technique. The effect on transparency, tensile stress, Young’s modulus as well as elongation percentages of the films was also examined. The results suggested that the addition of low molecular weight PEG (400 g.mol-1) increased the tensile stress of sago films from 33.51 MPa up to 39.11 MPa. Nevertheless, incorporation of high molecular weight of PEG (4000 g.mol-1) decreased the tensile strength of the film. Tensile strength and elongation at break of sago films increased with increasing of PEG concentration up to 2% and decreased with further increased of PEG content. Results indicated that there was a miscibility between these two components.

scholarly journals Fire Resistance, Thermal and Anti-Ageing Properties of Transparent Fire-Retardant Coatings Modified with Different Molecular Weights of Polyethylene Glycol Borate

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4206
Author(s):  
Long Yan ◽  
Xinyu Tang ◽  
Xiaojiang Xie ◽  
Zhisheng Xu
Keyword(s):  
Molecular Weight ◽  
Polyethylene Glycol ◽  
High Molecular Weight ◽  
Fire Resistance ◽  
Fire Retardant ◽  
Phosphate Ester ◽  
Low Molecular Weight ◽  
Molecular Weights ◽  
Flame Retarded ◽  
Residual Weight

Four kinds of polyethylene glycol borate (PEG-BA) with different molecular weights were grafted into cyclic phosphate ester (PEA) to obtain flexible phosphate esters (PPBs), and then applied in amino resin to obtain a series of transparent intumescent fire-retardant coatings. The comprehensive properties of the transparent coatings containing different molecular weights of PEG-BA were investigated by various analytical instruments. The transparency and mechanical analyses indicate that the presence of PEG-BA slightly decreases the optical transparency of the coatings but improves the flexibility and adhesion classification of the coatings. The results from fire protection and cone calorimeter tests show that low molecular weight of PEG-BA exerts a positive flame-retarded effect in the coatings, while high molecular weight of PEG800-BA behaves against flame-retarded effect. Thermogravimetric and char residue analyses show that the incorporation of low molecular weight of PEG-BA clearly increases the thermal stability and residual weight of the coatings and generates a more compact and stable intumescent char on the surface of the coatings, thus resulting in superior synergistic flame-retarded effect. In particular, MPPB1 coating containing PEG200-BA exerts the best flame-retarded effect and highest residual weight of 36.3% at 700 °C, which has 57.6% reduction in flame spread rate and 23.9% reduction in total heat release compared to those of MPPB0 without PEG-BA. Accelerated ageing test shows that low molecular weight of PEG-BA promotes to enhance the durability of structural stability and fire resistance of the coatings, while PEG800-BA with high molecular weight weakens the ageing resistance. In summary, the fire-resistant and anti-ageing efficiencies of PEG-BA in the coatings depend on its molecular weight, which present the order of PEG200-BA > PEG400-BA > PEG600-BA > PEG800-BA.

High-Throughput Synthesis of Oligo(ε-caprolactone) / Oligotetrahydrofuran Based Polyurethanes

MRS Advances ◽  
2018 ◽  
Vol 3 (49) ◽  
pp. 2965-2973
Author(s):  
M. Balk ◽  
A. Lendlein ◽  
M. Behl
Keyword(s):  
Molecular Weight ◽  
Chain Length ◽  
High Throughput ◽  
Melting Transition ◽  
Multiblock Copolymers ◽  
Molecular Weights ◽  
Melting Temperatures ◽  
End Groups ◽  
Model Components ◽  
End Group

ABSTRACTRobot assisted synthesis as part of high-throughput (HT) technology can assist in the creation of polymer libraries, e.g. polymers with a variety of molecular weights, by automatizing similar reactions. Especially for multiblock copolymers like polyurethanes (PUs) synthesized from telechels via polyaddition reaction, the adjustment of equivalent molar amounts of reactants requires a comprehensive investigation of end group functionality.In this work, PUs based on oligo(ε-caprolactone) (OCL) / oligotetrahydrofuran (OTHF) as model components were designed utilizing HT synthesis enabling the quantitative determination of the optimized ratio between reactive end-groups via fully automated syntheses without major characterization effort of end group functionality. The semi-crystalline oligomeric telechelics were connected with a diisocyanate and OCL with a molecular weight of 2, 4, or 8 kg∙mol-1 was integrated. Here, optimized molecular weights between 90 ± 10 kg∙mol-1 (in case of OCL 8 kg∙mol-1) and 260 ± 30 kg∙mol-1 (in case of OCL 2 kg∙mol-1) were obtained with an isocyanate content of 120 mol%, whereby 100 mol% of isocyanate groups resulted only in molecular weights between 60 ± 6 kg∙mol-1 (OCL 8 kg∙mol-1) and 80 ± 10 kg∙mol-1 (OCL 2 kg∙mol-1). In addition to the optimized ratio between isocyanate and hydroxy end groups, quantitative influences of the OCL chain length and overall molecular weights of PUs on thermal and mechanical properties were detected. The melting temperatures (Tms) of OCL and OTHF domains were well separated for PUs of low molecular weight, the temperature interval between the Tms decreased when the molecular weight of the PUs was increased, and were even overlapping towards one broad Tm, when OCL 2 kg∙mol-1 was incorporated. The storage modulus E’ was highly dependent on OCL chain length exhibiting an increase with increasing molecular weight of OCL from 220 MPa to 440 MPa at 0 °C and decreased with increasing chain length of PUs. The elongation at break (εb) was analyzed below and above Tm of OTHF resulting in εb = 780-870% at 0 °C and εb = 510-830% at 30 °C for PUs of high molecular weight. Accordingly, stretchability of PUs was almost independent of the state of OTHF (semi crystalline or amorphous) but correlated with the OCL precursor chain length (increasing εb with increasing chain length) and overall molecular weight of PUs (PUs at higher molecular weight exhibited higher εb). Hence, the analysis of these quantitative influences between macromolecular structure of multiblock copolymers and the resulting properties (well separated Tms versus overlapping melting transition, improvement of stretchability) would enable the design of new tailored PUs.

Permeabilization of Piceaglauca protoplasts to macromolecules

1989 ◽  
Vol 19 (10) ◽  
pp. 1316-1321 ◽  
Author(s):  
Faouzi Bekkaoui ◽  
David I. Dunstan
Keyword(s):  
Molecular Weight ◽  
Polyethylene Glycol ◽  
Fluorescein Isothiocyanate ◽  
White Spruce ◽  
Fluorescent Dye ◽  
Molecular Weights ◽  
Chemical Permeabilization ◽  
Protoplast Viability

Chemical permeabilization (polyethylene glycol, molecular weight 3350) and electropermeabilization (electroporation) treatments were applied to white spruce protoplasts to determine their effectiveness for uptake of membrane impermeable macromolecules. The two techniques have been compared using the membrane impermeable fluorescent dye calcein (molecular weight 622). The effects of varying the polyethylene glycol concentration, or the capacitance and voltage, were tested. In both techniques, the viability of protoplasts decreased after treatment compared with the controls. However, electroporation (capacitance 25 μF; voltage 300 V, 750 V•cm−1) gave better-permeabilization results (55% protoplast viability with 96% of these being fluorescent protoplasts) than the best treatment with polyethylene glycol (20%) (30% protoplast viability with 15% being fluorescent protoplasts). An investigation was made with the dye fluorescein isothiocyanate dextrans at different average molecular weights: 4000, 70 000, and 150 000. The degree of internalization by electroporation of each of these molecules did not substantially differ, though they were all low compared with calcein, which is suggestive of a limitation in permeability. The protoplasts subjected to either polyethylene glycol or electroporation treatments gave rise to callus and proembryos.

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