Siloxane Urethane Research Articles

Preparation and properties of solvent induced biodegradable thermosetting poly (siloxane urethane)

AbstractIt is difficult to recycle classic thermosetting plastics. Although some of them can be reprocessed, the mechanical properties decline linearly after processing. In addition, most thermosetting plastics are not environmentally friendly and difficult to degrade, resulting in a lot of pollution and limiting their practical application potential. In this paper, the prepolymer is synthesized by using castor oil (CO), hydroxyl terminated polydimethylsiloxane (PDMS‐OH), and toluene diisocyanate (TDI). Using 4,4'‐diaminodiphenyl disulfide (ODD) as a chain extender with dynamic disulfide bond and aniline (An) as a blocking agent, polysiloxane‐aminoester (SiCPUO) with recyclable function under DMF induction was prepared. The effect of the amount of rigid chain extender (ODD) containing disulfide bond on the properties of SiCPUO was studied, its heat resistance will first increase and then decrease with the increase of ODD content, especially the mechanical properties are more obvious, this trend has never been reported before; the mechanical properties and recyclability of SiCPUO are tested, and the comprehensive performance of SiCPUO2 is the best, the tensile strength is 0.84 MPa and the elongation at break was 65.81%; the solubility test of different solvents showed that it has recyclability, recovery rate is 95%;the material has self‐healing function, the repair efficiency is up to 95%.

Dependence of the structure of siloxane urethane elastomer on the conditions of synthesis

The morphology and thermal and mechanical properties of siloxane urethane block copolymers based on oligosiloxane- and oligoalkylene diols are investigated. The dependence of morphology on the conditions of synthesis is studied via atomic force microscopy and scanning electron microscopy.

Thermal and surface properties of hybrid materials obtained from epoxy-functional urethane and siloxane

In this work, a series of high-solids crosslinked hybrid networks based on the epoxy-terminated urethane oligomer and the comb-like structure epoxy-functional siloxane cured with diethylenetriamine, were obtained. The structure of the obtained poly(urethane–siloxane) thermosets was confirmed by FTIR spectroscopy. The samples were submitted to detailed thermal degradation investigations at non-isothermal conditions in nitrogen and air. The contact angles of the coatings and free surface energy calculated by Owens–Wend as well as van Oss–Good method, were studied. Some coating properties of the obtained hybrid materials were also investigated. The synthesized poly(urethane–siloxane) networks are hydrophobic materials, with free surface energy of 26–29 mJ/m2. The thermal stability and hardness of these increases with increasing siloxane content.

High Performance Randomly Segmented Poly(Urethane Siloxane) and Poly(Imide Siloxane) Copolymers

Polyimide materials with several kinds of mechanical properties have a great potential to use in aviation and space technology. One of these kinds of polyimide materials is poly(imide siloxane) copolymers. By this work, we also aimed to get flexible substrates in order to use as substrates in solar energy technology. Randomly segmented Poly(imide siloxane) and poly(urethane siloxane) block copolymers were produced based on benzofenon-3,3’,4,4’-tetracarboxylic dianhydride (BTDA), 4,4’-oxydianiline (ODA) and bis(3-aminopropyl) polydimethlysiloxane (APPS). The ODA and BTDA are the hard segments, APPS and BTDA are the soft segments in the structure. Many kinds of these copolymers could be produced by adjusting the soft and hard segment lengths. Poly(imide siloxane) block copolymers were insoluable in many organic solvents.

Synthesis and properties of high-solids hybrid materials obtained from epoxy functional urethanes and siloxanes

Abstract In this work series of novel high-solids crosslinked hybrid networks based on the epoxy-terminated polyurethane prepolymer and the comb-like structure co-poly(dimethyl)(methyl, 3-glycidoxypropyl)siloxane cured with diethylenetriamine, were obtained. The viscosity lowering of epoxy-terminated polyurethane prepolymer with temperature allowed for the preparation of the hybrid systems without using of any solvent. The structure of the obtained poly(urethane–siloxane) thermosets was confirmed by FT-IR spectroscopy. The DSC studies reveal, that the addition of siloxane resulted in the decrease of the glass transition temperature of the hybrid materials. The synthesized poly(urethane–siloxane) networks are hydrophobic, with the free surface energy of 17–31 mJ/m 2 . An increased amount of siloxane resulted in an increase of water contact angle and decrease of degree of water absorption as well as of FSE, which confirms a hydrophobic nature of the employed siloxane. Some properties of obtained hybrid materials based coatings were also studied.

Thermal degradation studies of poly(urethane–siloxane) thermosets based on co-poly(dimethyl)(methyl, 3-glycidoxypropyl)siloxane and epoxy-terminated urethane oligomer

Abstract A series of crosslinked hybrid poly(urethane–siloxane) networks based on comb-like structure co-poly(dimethyl)(methyl, 3-glycidoxypropyl) siloxane, epoxy-terminated urethane oligomer cured with diethylenetriamine, were obtained. The samples were submitted to thermal stability investigations at non-isothermal conditions in nitrogen and air. The thermal degradation behavior was investigated by evolved gas analysis, using coupled TG-FTIR technique. The kinetic parameters of the degradation process were determined both by isoconversional methods of Friedman and Kissinger–Akahira–Sunose as well as by model fitting multivariate non-linear regression method. It was observed that the thermal stability of the poly(urethane–siloxane) thermosets depends on the siloxane content. The first stage of degradation is associated with urethane degradation and the second with decomposition of polyoxytetramethylene and siloxane moieties. The best fit of the f ( α ) function with the experimental data was found for two-step degradation mechanism.

Thermal degradation studies of poly(urethane–siloxane) thermosets based on co-poly(dimethyl)(methyl, hydroxypolyoxyethylenepropyl) siloxane

• The thermal decomposition of the poly(urethane–siloxane) thermosets based on siloxane was investigated. • The TGA–FTIR of evolved gases during degradation were performed. • The thermal degradation kinetic parameters were determined. • The possible degradation model f(α) was proposed. A series of crosslinked hybrid poly(urethane–siloxane) networks based on comb-like structure co-poly(dimethyl)(methyl, hydroxypolyoxyethylenepropyl) siloxane cured with aliphatic diicocyanates hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and 4,4′-methylenebis(cyclohexyl isocyanate) (H 12 MDI), were obtained. The samples have been submitted to thermal stability investigations at non-isothermal conditions in nitrogen and air. The thermal degradation behavior was investigated by evolved gas analysis, using coupled TG–FTIR technique. The kinetic parameters of the degradation process were determined both by isoconversional methods of Friedman and Ozawa–Flynn–Wall as well as by model fitting multivariate non-linear regression method. It was observed that the thermal stability of the poly(urethane–siloxane) thermosets depends on employed diisocyanate. The best fit of the f ( α ) function with the experimental data was found for two-step degradation mechanism. Successive stages of thermal decomposition occurred by diffusion and by the expanded Prout–Tompkins model, respectively.

Development of heat-resistant anticorrosion urethane siloxane paints

Three two-layer heat-resistant and anticorrosion paints have been formulated from urethane siloxane binder and traditional anticorrosion pigments such as micaceous iron oxide (MIO), zinc phosphate (ZP), and aluminum oxide. These pigments were used as the dominant components of different undercoats or topcoats. Heat-resistant pigments such as silicon nitride and glass-spheres were used in the composition of the topcoats. Thermogravimetric analysis of paints shows that the paint with ZP as dominant component of the undercoat have the highest heat-resistance and stability in inert gas and oxygen. The paint with a combination of MIO and ZP has the best hardness as well as the best protective and anticorrosion properties based on the electrochemical impedance spectroscopy. A maximum synergic effect of the properties of pigments seems to appear in this paint. Surface morphology of paints was studied by means of scanning electron microscopy. Heated at different temperatures and for several hours, paint containing MIO as the dominant component in the undercoat exhibits the best mechanical and adhesion properties.

Synthesis and characterization of a novel hydroxy terminated polydimethylsiloxane and its application in the waterborne polysiloxane–urethane dispersion for potential marine coatings

α‐Butyl ω‐N, N‐dihydroxyethyl aminopropylpolymethylhydrosiloxane (PDMS), a monotelechelic polydimethylsiloxane with a diol‐end group, which is used to prepare siloxane–urethane dispersion, was successfully synthesized. Then, novel silicone‐based polyurethane (PU)‐dispersion was prepared by the addition polymerization of hexamethylene diisocyanate, to PDMS, polyethylene glycol (PEG) and dimethylol propionic acid. The goal of this study was to explore the potential use of polysiloxane–urethane in marine coatings in order to boost the flexibility, adhesion, erosion and foul‐release property with respect to PDMS/PEG ratio (PDMS wt%). The PDMS was characterized by Fourier‐transform infrared (FT‐IR), proton nuclear magnetic resonance and carbon‐13 nuclear magnetic resonance spectroscopic techniques. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases. The structural elucidation of the synthesized waterborne PU and waterborne polysiloxane–urethane (WBPSU) was carried out by FT‐IR spectroscopic technique. Thermal properties of the resins were studied by using thermogravimetric analysis and differential scanning calorimetry. The antifouling property of the coatings was investigated by the immersion test under a marine environment for 90 days. The fouled area was calculated for all the samples, and the fouled area (%) decreased with increasing PDMS content. After 90 days, the lowest fouled area (6%) was observed in the sample using WBPSU2 (PDMS 4.48 wt%) among all of the samples. Copyright © 2012 John Wiley & Sons, Ltd.

Studies of the Thermal and Mechanical Properties of Poly(urethane–siloxane)s Cross-Linked by Hyperbranched Polyesters

Polyurethane networks based on Boltorn hyperbranched polyesters (HBPs) of different pseudogenerations as cross-linkers, α,ω-dihydroxy(ethylene oxide–poly(dimethylsiloxane)–ethylene oxide) (EO–PDMS–EO) and 4,4′-methylenediphenyl diisocyanate were synthesized using a two-step polymerization reaction in solution. The influence of the pseudogeneration number of Boltorn HBPs on the thermomechanical and thermal properties and morphologies of polyurethane networks was investigated using FTIR, DMTA, TGA, hardness measurements, SEM, and SAXS. Synthesized polyurethanes showed higher cross-linking density and hardness and lower thermal stability with increasing pseudogeneration number of HBP. Samples with lower EO–PDMS–EO content exhibited slightly better thermal stability and higher hardness. All utilized characterization methods yielded consistent results and confirmed the existence of microphase separated morphology with the appearance of certain microphase mixing between segments as the pseudogeneration number of HBP increased. The obtained results revealed that the synthesized polyurethanes have good thermal and thermomechanical properties, which can be tailored by changing the pseudogeneration number of the HBP or the EO–PDMS–EO content.

Structure–Thermomechanical Property Correlations of Highly Branched Siloxane–Urethane Networks

A series of B3 core-terminated highly branched siloxane–urethane polymers was synthesized through the A2 + B3 route. Isophorone diisocyanate (IPDI)-terminated polydimethylsiloxane (PDMS) was used a...

Characteristics of the phase transition of poly(siloxane/ether urethane) copolymers

The aim of this study is to investigate the characteristics of the phase transition for poly(siloxane/ether urethane) copolymers (PSi-EUs) consisting of PTMG/PDMS mixed soft segments and urethane hard segments by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). PSi-EUs exhibit three regions of amorphous phase transition, involving the PDMS soft phase, the PTMG soft phase and the urethane hard phase; therefore, they display phase separation due to low miscibility. Intermolecular hydrogen bonding, which is key to phase mixing, hence resulting in a low degree of phase separation, occurs between the PTMG soft segments in the PTMG/PDMS mixed soft phase and the urethane hard segments. Accordingly, the PSi-EUs are superior to poly(siloxane urethane) copolymer (PSiU) in terms of tensile strength due to the low phase separation and strain-induced crystallization resulting from PTMG soft segments.

Dual-action hygienic coatings: Benefits of hydrophobicity and silver ion release for protection of environmental and clinical surfaces

Coatings that demonstrate reduced attachment of crystalline precipitates and the medical device colonising Staphylococcus epidermidis were prepared by the immobilisation of silver doped perfluoropolyether–urethane siloxane thin films on glass substrates. The presence of stratified hydrophobic perfluoropolyether groups protects the coating surface from the attachment of crystalline hydrophilic species such as chlorides and phosphates, whilst silver ion release inhibited attachment of S. epidermidis and subsequent biofilm formation in vitro. The release of silver ions protects the perfluoro groups from the hydrophobic interactions of S. epidermidis cells, which can reduce the hydrophobicity of the protective coating. These coatings also exhibited significant antibacterial activity against planktonic Acinetobacter baumannii and S. epidermidis bacterial strains. Detailed elemental and chemical surface analysis obtained using X-ray photoelectron spectroscopy (XPS) provided useful information on the effect of bacterial incubation on key indicator hydrophobic and hydrophilic functional groups. XPS analysis indicated preferential adsorption of S. epidermidis cells at the hydrophobic sites along the polymeric chain. These dual-action hygienic coatings can be employed to protect against contamination environmental surfaces and bacterial colonisation on implanted medical devices.

Characteristics of the degradation and improvement of the thermal stability of poly(siloxane urethane) copolymers

AbstractThis work investigates the characteristics of the thermal degradation of poly(ether urethane) (E‐PU) and poly(siloxane urethane) (S‐PU) copolymers by thermogravimetric analysis (TGA) and thermogravimetric analysis/Fourier transform infrared spectroscopy (TG–FTIR). The stage of initial degradation for E‐PU was demonstrated as a urethane‐B segment consisting of 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol. Moreover, the urethane‐B segment in the copolymers had the lowest temperature of degradation (ca. 200°C). The degradation of E‐PU was determined by TGA and TG–FTIR analyses and had three stages including seven steps. Although the soft segment of S‐PU possessed the thermal stability of polydimethylsiloxane (PDMS), the unstable urethane‐B segment existed in S‐PU. Therefore, the initial degradation of S‐PU appeared around 210°C. The four stages of degradation of S‐PU involved eight steps, as revealed by TG–FTIR, which identified the main decomposition products: CO2, tetrahydrofuran, and siloxane decomposition products. The imide group with high thermal stability was to replace the urethane‐B segment of S‐PU, which had the lowest thermal stability herein. The poly(siloxane urethane imide) (I‐PU) copolymer around 285°C exhibited a high initial temperature of degradation, and the initial degradation occurred at the urethane‐S segment consisting of MDI and PDMS. The degradation of I‐PU was similar to that of S‐PU and had four stages including six steps. Moreover, the degradation region of the imide group between 468 and 625°C was merged into the degradation stage of the siloxane decomposed products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

High throughput combinatorial characterization of thermosetting siloxane–urethane coatings having spontaneously formed microtopographical surfaces

High throughput combinatorial characterization was performed on thermosetting siloxane–urethane coatings in order to find a correlation between the characterization techniques, surface topography, and adhesion strength of barnacles. A series of coatings having microtopographical surfaces with different domain sizes were prepared based on a thermosetting siloxane–urethane system. This microtopography was formed spontaneously during the film-formation process. These surfaces were characterized by atomic force microscopy (AFM), surface energy, dynamic contact angle, and pseudo barnacle pull-off adhesion and were compared to pure polyurethane (PU) and silicone rubber control. Surface energy and dynamic contact angles were measured by an automated surface energy measurement system and pull-off adhesion values were obtained from a high throughput pull-off adhesion measurement unit. The results were compared with the adhesion strength of barnacles.

Gas transport properties of segmented poly(ether siloxane urethane urea) membranes

Poly(ether siloxane urethane urea) with different polysiloxane contents were synthesized and characterized. The single gas permeation properties of poly(ether siloxane urethane urea) membranes were determined at 30 °C for O 2, N 2, CO 2, CH 4, n-C 4H 10. Their structures and gas permeation properties were compared. Significant correlation among the polysiloxane soft segment with the permeation properties was found. In addition, an analysis of the viability to use these membranes for n-C 4H 10/CH 4 separation was made. A membrane with interesting properties such as higher n-C 4H 10/CH 4 selectivity for a mixture of gases than for single gases was obtained, indicating a possibility of application of the poly(siloxane urethane) membranes for n-C 4H 10/CH 4 separation.

Influence of solvent composition and degree of reaction on the formation of surface microtopography in a thermoset siloxane–urethane system

The effects of solvent composition and degree of reaction prior to film formation leading to the formation of a biphasic microtopographical surface in a crosslinked siloxane–urethane coating system were explored. For the solvent composition study, a D-optimal mixture design study was carried out using methyl n-amyl ketone (MAK), toluene, ethyl 3-ethoxypropionate (EEP), butyl acetate (BA) and isopropyl alcohol (IPA) as solvents. The study revealed that the presence of slow evaporating solvents MAK, EEP and the absence of fast evaporating solvent IPA in the solvent composition with a minimal amount of BA favored formation of a structured surface. Control over the domain size could be obtained by varying the MAK:EEP ratio in solvent compositions having a fixed amount of BA. The effect of mixing time on the formation of surface domains was studied. At short mixing times (<2 h) and long mixing times (>7 h), no surface phase separation is observed, while at intermediate times a ‘window’ was found where surface microdomains of similar size are generated. Doubling the level of catalyst halves the mixing time required to generate surfaces with microdomains. Scanning electron microscopy (SEM) studies with energy dispersive X-ray mapping and dynamic mechanical analysis (DMA) were done in order to understand the development of the phases in the PDMS-polyurethane system.

Coating of Polyester with Poly(dimethylsiloxane)- and Poly(tetramethylene oxide)-based Polyurethane

Copolymers siloxane–urethane are prepared to coat polyester fabrics to make them hydrophobic. Initially, our focus was on the bulk synthesis of poly(siloxane–urethane) in two steps: the first relates to the formation of a prepolymer between the isophorone diisocyanate and a poly(oxytetramethylene) glycol. In the second step, 1,4-butanediol is added, as the chain extender. Thus two types of polyurethanes are obtained according to whether poly(dimethylsiloxane) is introduced in the first or in the second step. Then the polyester fabric is impregnated with the prepared formulations. The contribution of coating during the mechanical tests is checked. The measurement of contact angles makes it possible to control the waterproofing effect expected for this kind of formulation.

Hydrogen bonding: a critical parameter in designing silicone copolymers

Structure–property relations in polydimethylsiloxane (PDMS) containing segmented copolymers with model hard segments capable of forming hydrogen bonding, such as urea, N-methylurea and urethane have been investigated. High molecular weight silicone containing copolymers with these hard segments were prepared from PDMS oligomers with number average molecular weights ranging from 890 to 3750 g/mol. Due to major differences in the solubility parameters between PDMS and polar hard segments, all copolymers are expected to display good microphase separation. It was demonstrated that mechanical and thermal properties of these copolymers are directly linked to the strength of the hydrogen bonding in the hard segments. As expected, siloxane–urea copolymers displayed much higher tensile strengths when compared with siloxane– N-methylurea and siloxane–urethane copolymers with similar compositions.

Investigations of morphology of moisture‐cured silicone–urethanes

Results of studies on synthesis and properties of siloxane–urethane prepolymers as well as on selected properties of moisture-cured silicone–urethanes have already been published. In this paper, some results of investigations of the effect of chemical structure of such silicone–urethane polymers on their phase seggregation investigated using mainly (TEM) transmission electron microscopy and small-angle x-ray scattering (SAXS) techniques are presented. It was found in TEM studies that in silicone-urethanes obtained by moisture-curing of NCO-terminated prepolymers prepared from siloxane oligomer diols (SOD) and isophoronediisocyanate (IPDI), two factors determine the morphology of samples: length of siloxane chain and NCO/OH ratio. SAXS investigations showed that these silicone–urethanes had a lamellar structure. It was found that the long period of this structure changed from 4 to 9 nanometers as the siloxane chain length increased nine times. The increase of the long period correlated with the decrease of Young's modulus of the corresponding samples. TEM investigations of silicone–urethanes obtained by moisture-curing of NCO-terminated prepolymers prepared from the blends of SOD and polyoxypropylenediol (PPG) revealed complex morphology which depended on the SOD/PPG ratio. Copyright © 2000 John Wiley & Sons, Ltd.