Hydroxyl-terminated Polydimethylsiloxane Research Articles

Synthesis and characterization of UV-curable waterborne Polyurethane–acrylate modified with hydroxyl-terminated polydimethylsiloxane: UV-cured film with excellent water resistance

In this paper, a series of UV-curable waterborne polyurethane–acrylate (WPUA) emulsions were synthesized by using isophorone diisocyanate (IPDI) as the hard segment, polybutylene adipate glycol (PBAG) and different dosages of hydroxyl-terminated polydimethylsiloxane (HTPDMS) as the soft segment, 2,2-dimethylolpropionic acid (DMPA) as hydrophilic chain extender, and pentaerythritol triacrylate (PETA) as the blocking agents. The properties of the WPUA emulsions were then characterized by using Fourier transform infrared spectrometry, Zeta potential analysis, dynamic light scattering, and UV-cured films were characterized through Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, scanning electron microscope, UV–vis spectrophotometer, and thermogravimetric analysis, as well as by measuring the contact angle of water, testing the water absorption. The results indicated that with increasing HTPDMS content in the WPUA, the particle size of the emulsion was increased significantly, while the absolute value of Zeta potential was increased slightly. The resistance of WPUA cured film to water was increased. The ultimate water absorption declined from 11.12 % to 6.81 % and the equilibrium time of water absorption extended from 50 h to more than 100 h. When the HTPDMS content of WPUA was 10.0 wt%, the water contact angle of the cured film was the largest at 114°, which indicated that the surface of the cured film has been changed from a hydrophilic surface to a hydrophobic one. Thermogravimetric analysis results showed that the initial decomposition temperature of WPUA film gradually increased with adding of HTPDMS, performing better thermal stability.

Effect of Boric Acid on the Structure and Properties of Borosiloxanes

Borosiloxane materials obtained by mixing and thermostatting of hydroxyl-terminated polydimethylsiloxane and boric acid are studied. Samples synthesized at room temperature and at a temperature above 220°С are nontransparent rubberlike masses. Washing of boric acid yields single-phase transparent borosiloxanes demonstrating the rubberlike behavior. Studies are carried out using elemental analysis, dynamic light scattering, synchronous thermal analysis, and polarization optical microscopy. The viscoelastic properties of the samples are characterized by rheological methods and the ability of polymer ball-like samples to spread and rebound. It is shown that in initial states they contain boric acid microcrystalline inclusions that scatter visible light. An increase in the synthesis temperature and the presence of unreacted boric acid improve the elasticity of the materials and decrease their thermal stability. The content of boron in borosiloxane obtained at an increased temperature is an order of magnitude higher than that in borosiloxane synthesized at room temperature, whereas the radius of the effective hydrodynamic sphere is smaller by a factor of 5 than that in the high-temperature borosiloxane. The rheological properties of the tested samples are different. These materials show promise as components of multilayer self-healing and shock-absorbing composites and materials with controlled tackiness.

Superhydrophobic magnesium oxychloride cement based composites with integral stability and recyclability

Magnesium oxychloride (MOC) cement has attracted much interest due to the superior mechanical properties, however enhancing the poor water-resistance is facing challenges and it is worthwhile devoting much effort to it. Here, a simple method to produce MOC based composites (MOCBCs) with superhydrophobicity is proposed. The samples could maintain superhydrophobic (SHP) after bearing mechanical and chemical damages, and the SHP MOCBCs are also capable of anti-icing. Meanwhile, the modified MOCBCs overcomes the poor water-resistance, the fatal defect of MOC based materials, because the main phases are protected by hydrophobic silicone rubber. SHP ability of MOCBCs can attribute to the combination of dual-level fractal structure and addition of hydroxyl-terminated polydimethylsiloxane (HPDMS), and this characteristic helps to achieve the function of self-cleaning. Besides, the powders ground from wasted MOCBCs exhibit superhydrophobicity, suggesting the potential recyclability of this material, which can be applied to SHP coating and oil/water separation.

Tertiaryamine linked and polysiloxane modified polyurethane acrylate oligomer and its effects of migration/co-initiation on photo-curable inkjet printing

To resolve the issue of handle-softness inadequacy in current polyurethane acrylate (PUA) oligomers for photo-curable inkjet printing on flexible substrates, and to improve the ability of anti-oxygen inhibition and photo-initiation efficiency of the tertiaryamine macromolecular co-initiator, the hydroxyl-terminated polydimethylsiloxane co-polymerized with tertiaryamine modified polyurethane acrylate (SiPUA) oligomer was designed and synthesized by using a sequential polymerization process. The structure of the SiPUA oligomer was confirmed by titration test and FTIR analysis, and the properties of the oligomers and the resultant photo-cured films were characterized by a range of analytical and measurement techniques. During the photo-curing process, the polysiloxane chain segment moved to the surface of the photo-cured SiPUA-HEA film due to the similar "surfactant critical micelle effect", forming an interconnected microphase structure of 50-70 μm thickness enriched with siloxane. The tertiaryamine group linked with polysiloxane segment was also enriched in the surface accordingly due to the migration of polysiloxane, thus improving the ability of anti-oxygen inhibition and photo-initiation efficiency. Benefiting from the both polysiloxane and tertiaryamine enriched surface and the retained PUA-HEA framework bulk in the cured film, a soft, flexible and strong photo-cured film with water-resistance and high photo-initiating efficiency was obtained.

Optimizing energy harvesting performance of silicone elastomers by molecular grafting of azobenzene to the macromolecular network.

The dielectric elastomer generator (DEG) has attracted significant attention in the past decade for harvesting energy from reciprocating mechanical motion owing to its variable capacitance under tension. However, the challenge of conceiving novel DEGs with high energy harvesting performance should be addressed. In this work, azobenzene molecules with strong polarity were synthesized and chemically grafted onto a hydroxyl-terminated polydimethylsiloxane (PDMS) network through a simple one-step process, offering a robust, molecularly homogenous silicone rubber. In addition, dimethyl silicone oil (DMSO) plasticizer was simultaneously added to reduce the mechanical modulus of the composite. The loading content of DMSO was firstly optimized in terms of the mechanical and dielectric properties of the resultant azo-g-PDMS/DMSO elastomers. Then, the effects of azobenzene loading on the morphology, and mechanical, dielectric and electric generation performances were thoroughly investigated. Overall, the dielectric permittivity displayed a rising trend with the increase of the azobenzene content while the breakdown strength increased initially and then decreased. The breakdown strength could reach as high as 73 V μm−1 by grafting with 7 phr of azobenzene while maintaining a relatively low mechanical modulus. Meanwhile, the as-prepared azo-g-PDMS/DMSO films exhibited enhanced energy harvesting density (0.69 mJ cm−3) and electromechanical conversion efficiency (5.01%) at a bias voltage of 1500 V, which were 2 and 2.5 times as much as those of the azobenzene-free matrix. This work provides ideas for future applications of DEG with high energy harvesting performance.

A green approach to preparing hydrophobic, electrically conductive textiles based on waterborne polyurethane for electromagnetic interference shielding with low reflectivity

A green method was employed to fabricate a coated textile with hydrophobic surface that provided electromagnetic interference shielding performance with low reflectivity. First, two-component waterborne polyurethane dispersions modified with hydroxyl-terminated polydimethylsiloxane were synthesized. Multi-walled carbon nanotubes (CNT) and graphene were well dispersed in water via high pressure microfluidizer. Waterborne polyurethane and fillers containing 80% CNT and 20% graphene were applied to textiles by dipping method. The water contact angles of the polyurethane coating and the coated textile were 103.4° and 153.6°, respectively, when the polyurethane contained 10% hydroxyl-terminated polydimethylsiloxane. The electromagnetic interference (EMI) shielding effectiveness (EMI SE) of the coated textile (3% filler loading) could achieve 35 dB with a thickness of only 0.35 mm and the reflectivity is ca. 41.4%. By dipping a textile into polyurethane dispersions with different filler loadings (1% and 3%) to obtain a coated textile with a two-layer structure coating. EMI SE of the coated textile reached 30 dB and the reflectivity was only ca. 26.5%, indicating 26.5% of the electromagnetic waves is reflected during the propagation process when 99.9% electromagnetic waves is attenuated. Possible attenuation mechanisms of electromagnetic waves such as dielectric loss, multiple reflections, scattering and conductive loss were discussed. The mechanical properties, thermal conductivity and thermal stability of the coatings and coated textiles were studied. The coated textiles fabricated in a green and facile approach with excellent electromagnetic shielding performance and low reflectivity have great potential in advanced EMI shielding applications.

Synthesis and structure of calcium silicate hydrate (C-S-H) modified by hydroxyl-terminated polydimethylsiloxane (PDMS)

Calcium silicate hydrate (C-S-H) is the main hydration product of cement, and its micro-nano-structure has an important influence on the properties of cement-based materials. The disadvantages of cement-based materials are related to the micro-nano-structure defects of C-S-H. The modification of the C-S-H structure by silane can make up the defects of C-S-H. Here, we studied the structure of C-S-H modified by a straight-chain silane containing silicon hydroxyl groups at both ends. Calcium silicate hydrate (C-S-H) gel particles modified by hydroxyl-terminated polydimethylsiloxane (PDMS) were synthesized by the sol–gel method. The influence of this organic modification on the structure of C-S-H was investigated by XRD, FTIR, NMR, SEM, TG-DTG and water contact angles techniques. The results show that various sizes of C-S-H gel particles are connected with PDMS via covalent bond. PDMS acts as a bridge between C-S-H particles. The introduction of PDMS changes the morphology of stacked spherical particles to cauliflower-like and increases water contact angle of C-S-H. In addition, various sizes of C-S-H gel particles are also coated by PDMS. This research explains the methods for affecting the stacking process of C-S-H gel particles.

Flexible Nanocomposites Based on Polydimethylsiloxane Matrices with DNA-Modified Graphene Filler: Curing Behavior by Differential Scanning Calorimetry.

Novel silicone-based nanocomposites with varied elastic properties were prepared by blending standard polydimethylsiloxane (PDMS) with a lower viscosity component (hydroxyl-terminated PDMS) and integrating a graphene nanoplatelets (GNP) filler modified by strands of deoxyribonucleic acid (DNA). The curing behavior of these nanocomposites was studied by dynamic and isothermal differential scanning calorimetry. The activation energies of the polymerization reactions were determined using the Kissinger method and two model-free isoconversional approaches, the Ozawa–Flynn–Wall and the Kissinger–Akahira–Sunose methods. Results show that the complex trend of the curing behavior can be described using the isoconversional methods, unveiling lower activation energies for the nanocomposites with standard PDMS matrices. The role of the DNA modification of graphene on the curing behavior is also demonstrated. The curing reactions of the nanocomposites with the PDMS matrix are favored by the presence of the GNP–DNA filler. PDMS/PDMS–OH blends generate softer nanocomposites with hardness and reduced elastic modulus that can be tuned by varying the amount of the filler.

Study on synthesis and abrasion resistance of thermoplastic polyurethanes using hydroxyl-terminated polydimethylsiloxane and polyether polyols

Since a production line for 3D printing is easier to change a product model than that for traditional manufacturing one, 3D printing technology is developing and growing faster than most other technologies. A thermoplastic polyurethane is suitable for a 3D printing material because of easy control of its properties by changing a hard/soft segment ratio. A polyurethane having a low content of hard segment can be melted at low temperature and shows high rebound resilience and high slip resistance. However, it is not suitable for a shoe outsole material because of its low abrasion resistance. In this study, hydroxyl-terminated polydimethylsiloxane (PDMS-OH) was used as an additional polyol to improve abrasion resistance. Polyurethanes were synthesized by adding a small amount of PDMS-OH. Abrasion and slip resistances of the synthesized polyurethanes were investigated as a shoe outsole material for 3D printing. The result showed that both properties of PDMS-containing polyurethanes were strongly depended on the content of PDMS.

Synthesis and Characterization of TEOS Coating Added With Innovative Antifouling Silica Nanocontainers and TiO2 Nanoparticles

We study the synthesis and characterisation of an innovative TEOS-based composite coating, which could improve previous formulations used in the field of monument conservation. The proposed coating is composed by a tetraethoxyorthosilicate matrix (TEOS), containing an elasticiser (hydroxyl-terminated polydimethylsiloxane (PDMS-OH)) and a non-ionic surfactant (n-octylamine). The specific self-cleaning and antifouling properties are obtained by the addition of different kinds of nanofillers: the commercial TiO2 nanoparticles, plus two different silica nanocontainers, loaded with the commercial biocide 2-mercaptobenzothiazole. Through a multi-analytical approach, we evaluate the effect of the nanoparticles concentration on the coatings drying rate, on the variation of their visual aspect and textural properties. Our results show that the addition of the silica nanocontainers at 0.05% (w/v) in sol does not change the colour of the coating and reduces the formation of cracks after drying. Moreover, the coating charged with nanocontainers undergoes slower drying, thus improving its penetration into the pores of the treated surface. Further tests of photocatalytic and biocidal properties of this new product on different lithotypes and their potential interactions are in progress.

Study on Optimization of Damping Performance and Damping Temperature Range of Silicone Rubber by Polyborosiloxane Gel.

Polyborosiloxane gel (PBS-gel) with shear hardening properties was prepared by cross-linking boric acid and hydroxyl-terminated polydimethylsiloxane through B–O–Si dynamic covalent bonding. The prepared PBS gel was mixed with methyl vinyl silicone rubber (MVQ), and a benzoyl peroxide (BPO) cross-linking agent was added to vulcanize the silicone rubber. At the same time, the gel molecules were co-vulcanizing with MVQ to produce molecular cross-linking. The effects of PBS-gel on the damping properties of silicone rubber were analyzed by dynamic rheological test, Fourier transform infrared spectroscopy and dynamic mechanical analysis. The results demonstrated that the damping performance of MVQ/PBS rubber is greatly improved and the rubber has a tanδ > 0.3 in the range of −25~125 °C. The shear-hardening gel is uniformly dispersed in the system, due to the combined action of covalent bonds and intermolecular forces, which act as an active molecular chain that can efficiently dissipate and transfer energy inside the silicone rubber.

Immobilization of nonisolated BiPO4 particles onto PDMS/SiO2 composite for the photocatalytic degradation of dye pollutants

In this study, a crack-free PDMS–SiO2–BiPO4 (P/Si/Bi) composite was prepared via a solgel-assisted route by dispersing pre-prepared bismuth oxybromide into a solution that was composed of hydroxyl-terminated polydimethylsiloxane (PDMS–OH), tetraethyl orthosilicate and phosphoric acid. Analysis via the FTIR, XRD, XPS and SEM–EDX techniques demonstrated that the nonisolated BiPO4 particles with a monoclinic crystal phase were uniformly distributed on the surface of the P/Si/Bi composite, which can provide more active sites and a larger surface area for photocatalysis compared with other materials. The photocatalytic activity of the P/Si/Bi composite loaded with various mass ratios of BiPO4 (9 wt%, 12 wt%, 18 wt% and 27 wt%) was investigated via the degradation of methylene blue (MB, 10 mg/L) under UV light irradiation. It was found that the P/Si/Bi composite loaded with 18 wt% BiPO4 realized the highest degradation efficiency of MB, and its corresponding apparent rate constant was approximately 2.2 times that of the PDMS–SiO2–TiO2 composite (loaded with 18 wt% TiO2). The effects of inorganic ions on the degradation of MB were also investigated. The static contact angle and photocatalytic activity of the P/Si/Bi composite changed minimally after five cyclic experiments, thereby demonstrating its remarkable durability in sustainable applications. In addition, the photogenerated reactive species that were responsible for the degradation of MB within the P/Si/Bi composite were identified, and a photocatalytic mechanism was proposed.

High hydrophobic preservation materials can cause damage to tabia relics

Silicone has commonly been used to preserve and protect tabia relics. However, it was recently observed in numerous circumstances, that the addition of silicone facilitates failures on the consolidated parts, e.g., warping and detachment, thereby accelerating the destruction of the tabia relics. Thus, the goal of this study is to perform preliminary research work on the long-term effectiveness of tabia preservation materials. Two silicone tabia preservation materials with different hydrophobicity were prepared. Tetraethoxysilane (TEOS) supplemented with additives hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and cetyltrimethylammonium bromide (CTAB) with a static water contact angle of 110°, served as the low hydrophobicity preservation material; while hexadecyltrimethoxysilane (HDTMS) with a static water contact angle of 110° provided the high hydrophobicity preservation material. Both the two preservation materials were used on the Zhenyuan Tabia Fort in Ningbo City, Zhejiang Province, China. Multi-factor deterioration experiments, including capillary water absorption with Na2SO4 solution, salt crystallization, freeze-thaw cycle, and wet-dry cycle were performed to assess the causes of the damage induced by the preservation materials. The results indicate that the use of the high hydrophobicity of preservation material facilitates damage to the tabia relics.

Water and oil resistance improvement of paper coated with aqueous mixture of hydrophilic and hydrophobic cross-linked copolymers

An aqueous mixture of hydrophilic and hydrophobic cross-linked copolymers was prepared and coated on the surface of filter paper to improve the water and oil resistances. The mixture was mainly composed of sodium alginate and hydroxyl-terminated polydimethylsiloxane (PDMS)-tetramethoxysilane (TMOS) cross-linked network. The results indicated that the resistances to both water and oil of the resulting paper were significantly enhanced. The water contact angle results demonstrated that the mixture enhanced the hydrophobic properties of the coated paper greatly with water contact angles higher than 110°, and the coated paper showed excellent oil resistance with a Kit number as high as 10.

Promoted ablation resistance of polydimethylsiloxane via crosslinking with multi-ethoxy POSS

The utilization of advanced propellants leads to unbearable temperature and pressure in propellent ramjet engines, paving the way for the enhancement of thermal insulation materials. High temperature vulcanized polydimethylsiloxane composites have been adopted due to the satisfactory ablation resistance at the expense of complicated industrial costs. For the purpose of simplifying the processes and enhancing the ablation resistance of polymer matrices, room temperature vulcanized hydroxyl-terminated polydimethylsiloxane (HPDMS) crosslinked with multi-ethoxy POSS (EOPS) coatings (EOPS@ HPDMS) were prepared through capping crosslink. Comparative analyses of different EOPS loadings of EOPS@HPDMS revealed the chemical bonding of EOPS ameliorated the effects about crosslinking properties, mechanical strengths, thermal performance and ablation resistance of HPDMS. This work could provide an optional method for developing advisable ablation resistance composites in aerospace applications.

Influence of Epoxy Content on the Properties and Marine Bacterial Adhesion of Epoxy Modified Silicone Coatings

This study addresses the issue of enhancing the mechanical properties and adhesion of silicone antifouling coatings. In this paper, γ-aminopropyltriethoxysilane was used to pretreat bisphenol A epoxy resin to obtain epoxy-silicone prepolymer, which was then mixed with hydroxyl-terminated polydimethylsiloxane to obtain epoxy-modified silicone. It was cured with polyamide curing agent and dibutyltin dilaurate catalyst to form film, and a three-component epoxy-modified silicone coating was prepared. Fourier transform infrared (FTIR) spectroscopy was used to characterize its chemical structure. The effects of epoxy content on the surface properties, mechanical properties and antibacterial properties of the coatings were characterized by confocal laser scanning microscope (CLSM), contact angle measurements, tensile test and bacterial adhesion test. The results show that adding epoxy makes the adhesion of the coating at level 1 and the surface free energy of the coating was between 15–21 mJ/m2. When its content is less than 22.1 wt %, the coating is in a ductile material state. Once it is higher than 22.1 wt %, the coating was in a brittle material state. As the content increases, material’s hardness and fracture strength increases; elastic modulus decreases first and then increases, but bacteria removal rate decreases. The modification of the epoxy to silicone can effectively improve the adhesion and mechanical properties of the coating, while maintaining the characteristics of the low surface of the coating. It plays a positive role in improving the performance of silicone antifouling coatings.

Effect of a hydroxyl terminated poly dimethyl siloxane, in combination with TESPT, on the mechanical and dynamic properties of silica filled rubber in addition to reducing ethanol emission in combination with TESPT

ABSTRACTThis work is aimed to improve the dispersion of silica without compromise on the Mechanical and Dynamic properties, by the addition of Hydroxyl terminated poly dimethyl siloxane (PDMS-OH). PDMS-OH is expected to interact with silica through hydrogen bonding which is reversible, reduces filler–filler interaction and hence improve the silica dispersion. Dissociation of hydrogen bonds which is reversible, provides a way for significant energy dissipation during deformation by the external stress and then promotes the recovery after the stress is removed. This prevents the filler re-agglomeration after deformation which is not possible with only silica-TESPT bonds which are covalent and irreversible. This study also explores the possibilities of reducing the emission of volatile organic compound ethanol by partially replacing the TESPT coupling agent with PDMS-OH without sacrificing in Mechanical and Dynamic properties such as Rolling Resistance and wet Traction.

Effect of polydimethylsiloxane viscosity on silica fume-based geopolymer hybrid coating for flame-retarding plywood

Hydroxyl-terminated polydimethylsiloxane (PDMS) modified silica fume-based geopolymer explores a novel challenging and interesting flame-retardant hybrid coating, and the effect of PDMS viscosity on the flame resistance and microstructure is investigated firstly. The optimum kinetic viscosity of PDMS is estimated as 350 cps according to the results of cone calorimeter (CC), which imparts a 50% decreased fire growth index (FGI) with the fire performance index (FPI) of 3.80 s·m2·kW−1 to the hybrid coating. The incorporation of PDMS renders the decreases in the weight loss percent (52.51%) and the average combustion velocity Vac (6.74 × 10−2%·s−1), as well as excellent smoke suppression. The doped PDMS (350 cps) facilitates the transformation from Q40 (no aluminum ion in Si-O-Si chains) to Q41 or Q42 groups (one or two aluminum ions Al3+ replace the pristine Si4+) involved in geopolymer coating, evidenced by the results of 29Si magic angle spinning nuclear magnetic resonance (29Si MAS NMR) spectra, leading to a continuous, compact, and intact barrier layer from microstructure analysis. Moreover, the retarding mechanism of PDMS in the hybrid coating is elucidated including physical filling, heat sink effect of Si-O- chains, hydrogen bonding, and crosslinking. However, excessive PDMS viscosity exerts adverse flame resistance to the silica fume-based geopolymer hybrid coating.

Hybrid siliconized–epoxidized EPDM/polyurethane (eEPDM-g-APTES/HTPDMS/PU) matrices for potential application in cable insulation

Hybrid matrices (epoxidized of ethylene–propylene–diene monomer (eEPDM) -g-aminopropyltriethoxysilane (APTES)/hydroxyl terminated polydimethylsiloxane (HTPDMS)/polyurethane (PU)) were developed based on eEPDM with 3-APTES coupling agent and varying weight percentages (0.75, 1.50, 2.25, and 3.00 wt%) of PU prepolymer as coreactant using 7.5 wt% of HTPDMS as chain extender using suitable experimental conditions. The formation of hybrid matrices and their structure were characterized by Fourier transform infrared (FTIR). The thermal and morphological properties of the hybrid matrices were analyzed using differential scanning calorimetry and scanning electron microscope, respectively. Mechanical properties (tensile strength, elongation at break (%), Young’s modulus, and hardness) were characterized as per ASTM standards. Data resulted from mechanical studies, it was noticed that the incorporation of 3-APTES, HTPDMS, and PU into eEPDM has improved the elongation at break (%) and lowered the values of tensile strength, Young’s modulus, and hardness according to the percentage concentration. Morphological studies indicate the presence of heterogeneous morphology. Data obtained from different studies, it suggested that the hybrid matrices developed in the present work can be used as cable insulates for high-performance industrial and engineering applications.

First-Order and Third-Order Nonlinearities from Medium-Amplitude Oscillatory Shearing of Hydrogen-Bonded Polymers and Other Viscoelastic Materials

Medium-amplitude oscillatory shear experiments are employed to study the supramolecular relaxation modes in hydroxyl-terminated polydimethylsiloxane. For these associating melts, this allowed us to identify the nonlinear rheological signature of hydrogen-bond-mediated structures occurring in addition to those of the covalent chains. First-order and third-order nonlinearity parameters are determined for the supramolecular and chainlike modes to compare them with the predictions of an array of rheological models. Fingerprints of the two supramolecular modes can be recognized in the nonlinear response. By collecting third-order nonlinearity parameters 3Q0 for about 35 materials including polymer melts, polymer solutions, and other viscoelastic fluids, it is demonstrated that the maximum value of 3Q0 correlates with the magnitude of the shear modulus at the frequency at which this maximum occurs. The implications of this experimental finding are discussed.