Synthesis and properties of nanosilica‐reinforced polyurethane for grouting

A polyurethane/nanosilica (PU/SiO₂) hybrid for grouting was prepared in a two‐step polymerization using poly(propylene glycol) diols as the soft segment, toluene 2,4‐diisocyanate (TDI) as the diisocyanate, 3,3′‐dichloro‐4,4′‐diaminodiphenylmethane (MOCA) as the chain extender, and acetone as the solvent. The size and dispersion of nanosilica, the molecular structure, mechanical properties, rheological behavior, thermal performance, and the UV absorbance characteristic of the PU/SiO₂ hybrid were investigated by transmission electron microscopy (TEM), FTIR, mechanical tests, viscometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and UV spectroscopy. Nanosilica dispersed homogeneously in the PU matrix. The maximum values of mechanical properties such as tensile strength, elongation break, and adhesive strength showed an addition of nanosilica of about 2 wt %. Resistance to both high and low temperatures was better than with PU. And the UV absorbance of the PU/SiO₂ hybrid increased in the range of 290–330 nm with increasing nanosilica content. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4333–4337, 2006     

The effect of nanosilica on mechanical,thermal and morphological properties of epoxy coating

In this study, nanosilica of very high specific surface area is used as reinforcing filler for preparing an epoxy-based nanocomposite coating. For appropriate dispersion of nanoparticles in the polymer matrix, ultrasound waves were applied after mechanical mixing. The resulting perfect dispersion of nanosilica particles in epoxy coating revealed by transmission electron microscopy ensured the transparency of the nanocomposite. Nanoindentation was used to determine some mechanical properties such as hardness and elastic modulus. The obtained results show 26 and 21% increases in hardness and elastic modulus, respectively for resin filled with 5% nanosilica compared to neat epoxy. DMA results show that the glass transition temperature of samples is increased with increasing silica nanoparticles. The result of TGA shows significant improvement of the thermal decomposition temperature of epoxy coating containing 5% nanosilica compared to neat epoxy. Scanning electron microscopy (SEM) micrographs of fractured surfaces show increased roughness with nanosilica addition.     

Structure–property correlation of polyurethane nanocomposites: Influence of loading and nature of nanosilica and microstructure of hyperbranched polyol

New generation polyurethane nanocomposites based on toluene diisocyanate, poly(propylene glycol), hyperbranched polymers (HBPs), and nanosilica were synthesized with the aim of determining the effect of the loading and nature of nanosilica and the functionality of HBP on the structure and properties of polyurethane nanocomposites. Good dispersion of nanosilica at 4 wt % loading in the polymer was confirmed from atomic force microscopy. The properties of the polyurethane nanocomposites were a function of content and nature of the nanosilica in the matrix. The optimum silica loading was 4 wt %. At this loading, tensile strength and storage modulus at 25°C of the nanocomposites increased by 52 and 40%, respectively over the pristine polyurethane. Organo‐treated nanosilica exhibited higher physico‐mechanical properties than the untreated one. With the increase of functionality in the hyperbranched polyol, the tensile strength, thermal stability, and dynamic mechanical properties of the nanocomposites improved. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of the diisocyanate structure and the molecular weight of diols on bio‐based polyurethanes

Bio‐based polyurethanes (PU) containing poly(ε‐caprolactone) diol (PCL) and hydroxyl telechelic natural rubber (HTNR) were synthesized. The effect of the diisocyanate structure and the molecular weights of diols on the mechanical properties of PU were investigated. Three different molecular structures of diisocyanate were employed: an aliphatic diisocyanate (hexamethylene diisocyanate, HDI), an aromatic diisocyanate (toluene‐2,4‐diisocyanate, TDI) and a cycloalkane diisocyanate (isophorone diisocyanate, IPDI). Two molecular weights of each diol were selected. When HDI was employed, a crystalline PU was generated while asymmetrical structures of TDI and IPDI provided an amorphous PU. The presence of crystalline domains was responsible of a change in tensile behavior and physical properties. PU containing TDI and IPDI showed a rubber‐like behavior: low Young's modulus and high elongation at break. The crystalline domains in PU containing HDI acted as physical crosslinks, enhancing the Young's modulus and reducing the elongation at break, and they are responsible of the plastic yielding. The crystallinity increased the tear strength, the hardness and the thermal stability of PU. There was no significant difference between the TDI and IPDI on the mechanical properties and the physical characteristics. Higher molecular weight of PCL diol changed tensile behavior from the rubber‐like materials to the plastic yielding. Thermal and dynamic mechanical properties were determined by using DSC, TGA and DMTA. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Biodegradable poly(ester)urethane (PU) elastomer‐based nanocomposite films incorporated with organically modified nanoclay were prepared with melt‐extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X‐ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water‐vapor barrier properties of the nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of new functional poly(urethane‐imide) crosslinked networks

To synthesize new functional poly(urethane‐imide) crosslinked networks, soluble polyimide from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′‐oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4‐diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane‐imide) thin films were finally prepared by the reaction between maleimide end‐capped soluble polyimide (PI) and acrylate end‐capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano‐indentation. Dielectric constant of poly(urethane‐imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane‐imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane‐imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane‐imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane‐imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006     

Waterborne polyurethane and modified polyurethane acrylate composites

Abstract

Waterborne polyurethane (PU) and a series of PU acrylate (PUA) composite dispersions were synthesised from isophorone diisocyanate, polyester polyols, dimethylol propionic acid, hydroxyethyl methyl acrylate, butyl acrylate and methyl acrylate. Fourier transform infrared, ultraviolet visible and differential scanning calorimetry were used to demonstrate structures, optical transparency and thermal stabilities of PU and PUA. The PUA sample had lower glass transition temperature of hard segment and higher decomposition temperature than the PU sample. Performances of the dispersion and film were studied by means of apparent viscidity, particle size and particle size distribution index, surface tension and mechanical property. The results indicated that the solvent resistance and mechanical property of PUA film were improved compared with the pure PU film. The obtained stable PUA composite samples have excellent integrated properties and have a great potential application in meeting the highly diversified demands in modern technologies, such as coatings, leather finishing, adhesives, sealants, rubbers, plastic coatings and wood finishes.     

Modification of aqueous polyurethane dispersions via tetraphenylethane iniferters

Aqueous polyurethane (PU) dispersions containing tetraphenylethane iniferter groups were prepared from 4,4′‐diphenylmethane diisocyanate, poly(propylene oxide)glycols, dimethylol propionic acid, and 1,1,2,2‐tetraphenylethane‐1,2‐diol. To improve the water resistance of the dispersions, methyl methacrylate monomers were added into these dispersions and block‐copolymerized onto the main PU chain. The viscosity and particle size of the dispersions were determined. Dispersion‐cast films were characterized in terms of the contact angle, the swell in water, and the mechanical properties. Contact‐angle and water‐swell measurements showed that the hydrophilicity of the films was decreased significantly when methyl methacrylate was polymerized in the presence of tetraphenylethane containing aqueous PU dispersions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2993–3000, 1999     

Enhancement of hydrolytic stability and adhesion of waterborne polyurethanes

A new type of polyester polyol, with alkyl side groups, viz. poly(2,4‐diethyl‐1,5‐pentamethylene adipate) glycol (PDPAd) was synthesized and used to improve the hydrolytic stability of waterborne polyurethanes (PU). The results compared favorably with poly(tetramethylene adipate) glycol (PTAd)–based PU and blends of the two types of PU in terms of particle size, thermal, XRD, mechanical, dynamic mechanical, and swell behavior of the dispersion cast films in addition to hydrolytic stability and adhesion properties. Blends of PTAd‐based PU and PDPAd‐based PU gave significantly improved green (immediate) adhesion and hydrolytic stability due to the synergistic effects of crystallinity (heat of crystallization, high density) and amorphous regions (tack, high thermal stability). © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1961–1969, 2005     

Physical properties of water‐borne polyurethane blended with chitosan

Water‐borne polyurethanes based on 4,4‐diphenylmethane diisocyanate, poly(butylene adipate), and chain extender N‐methyldiethanolamine (MDEA) that provided tertiary amine groups were synthesized. The polyurethane–chitosan (PU/CS) blends can be dissolved in the acetic acid and cast into films. The mechanical properties including tensile strength and elongation, as well as the water absorption and thermal properties of the PU/CS films were evaluated. The tensile strength increased with the increased amount of chitosan, but the elongation decreased accordingly. The chitosan in the blends promoted the water absorption. Chitosan was more thermally‐stable than PU, as shown in the thermal gravity analysis. Chitosan also had higher crystallinity, as demonstrated by differential scanning calorimetry. The blends were partial compatible mixtures, based on the data obtained from a dynamic mechanical analysis. Biocompatibility test was conducted utilizing immortalized rat chondrocytes (IRC). After IRC were seeded onto the PU/CS films for 1.5 and 120 h, the number of cells was counted and the morphology of cells was observed by light microscopy and scanning electron microscopy. Blends containing 30% chitosan had more cells attached initially. However, the blends containing more than 70% chitosan appeared to promote the cell proliferation. IRC were round on PU/CS films with more PU, but spread when the chitosan content in blends was higher. Overall, PU/CS films with more chitosan had better mechanical properties as well as biocompatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2683–2689, 2007     

Shape memory thin films of polyurethane: Synthesis,characterization, and recovery behavior

Polyurethane thin films with inherent two phase segregated characters are exceptional candidates for the development of shape memory materials. However, controlling the phase behavior of such complex structures for decoding their recovery behavior still experiences its early stage of development. In this work, polyurethane thin films were synthesized based on two polyols, ester-based polyols (ESP), and ether-based polyols (ETP) together with diphenyl diisocyanate (MDI). The effects of ingredient ratio of PETP (ether-based prepolymer)/PESP (ester-based prepolymer) on the chemical structure and final properties of polyurethanes were studied by the Fourier-transformed infrared spectroscopy (FTIR), the differential scanning calorimetry (DSC), the scanning electron microscopy (SEM), the dynamic mechanical thermal analysis (DMTA), a tensiometer, and the atomic force microscopy (AFM). The shape memory behaviors were explored by the thermomechanical cycles applied by a DMTA device in the controlled force mode. The PU films showed various properties compared with the bulk PU since they formed spherulitic textures with different structures. All the PU films except PU-0 showed high shape recovery ca. 90% in the first cycle with a large glassy storage modulus in the range of 2,800–4,040MPa, and a recovery ratio enhanced by increasing the number of cycle to a maximum of 95%.     

Surfactant-free core–shell hybrid latexes from soybean oil-based waterborne polyurethanes and poly(styrene-butyl acrylate)

Novel surfactant-free core–shell hybrid latexes have been successfully synthesized by seeded emulsion polymerization of 10–60 wt% vinyl monomers (styrene and butyl acrylate) in the presence of a soybean oil-based waterborne polyurethane (PU) dispersion as seed particles. The soybean oil-based waterborne polyurethanes, synthesized by reacting isophorone diisocyanate with methoxylated soybean oil polyols and dimethylol propionic acid, form the latex shell, serve as a polymeric high molecular weight emulsifier, while the vinyl polymers form the core. The structures and thermal and mechanical properties of the PU dispersions and the resulting core–shell latexes have been characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and measurement of the mechanical properties. The core–shell hybrid latex films show a significant increase in thermal stability and mechanical properties when compared with the pure polyurethane films, and exhibit a change in mechanical behavior from elastomeric polymers to tough and hard plastics, due to grafting and crosslinking in the hybrid latexes.     

Subsurface mechanical properties of polyurethane/organoclay nanocomposite thin films studied by nanoindentation

A series of the exfoliated or intercalated PU/organoclay nanocomposite thin films were prepared by in situ polymerization of polyol/organoclay mixture, chain extender and diisocyanate. The surface mechanical properties of the PU/organoclay nanocomposite films were investigated by means of nanoindentation. The results show that the hardness, elastic modulus and scratch resistant of the nanocomposites dramatically improved with the incorporation of organoclay. This improvement was dependent on the clay content as well as the formation structure of clay in the PU matrix. At 3% clay content, the hardness and elastic modulus of intercalated nanocomposites increased by approximately 16% and 44%, respectively, compare to pure PU. For exfoliated nanocomposite, the improvements in these properties were about 3.5 and 1.6 times higher than the intercalated ones. The exfoliated PU nanocomposites also had greater hardness and showed better scratch resistance compared to the intercalated ones.     

Synthesis of CNT‐polyurethane nanocomposites using ester‐based polyols with different molecular structure: Mechanical,thermal, and electrical properties

Polyurethanes (PUs) were prepared by in situ polymerization of three diisocyanate with three synthesized low cost ester‐based polyols. The effect of diisocyanate type, diol structure, and molar ratio of diisocyanate to polyol on the mechanical properties was examined and the optimum chemical structure was introduced regarding the superior mechanical properties. Also, in presence of well dispersed hydroxylated multiwalled carbon nanotubes (CNT), PU/CNT nanocomposites were synthesized and fully characterized. The results showed that PU synthesized based on 1,4‐butane diol (BDO) has the best mechanical properties and thermal stability. Also, the PU samples synthesized from 1,6‐hexamethylene diisocyanate (HDI) were more profitable than aromatic diisocyanate structures due to higher crystallinity and microstructure packing. The nanocomposite sample containing 1.5% CNT was the optimum composition for the maximum tensile strength and electrical conductivity. This result was related to the uniform dispersion and bonding of CNTs to PU chains at this composition, while aggregates were formed at higher concentration of CNTs which increased the defects and reduced the uniformity of the structure. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44567.     

软段对IPDI基透明聚氨酯弹性体微相结构与性能的影响

采用不同结构的软段、扩链剂l,4-丁二醇和异佛尔酮二异氰酸酯(IPDI)为主要原料合成了透明聚氨酯弹性体。研究了软段结构变化对聚氨酯弹性体的微相结构、力学性能、热稳定性及光学透明性的影响。结果表明,相对分子质量高的软段比相对分子质量低的软段更易结晶,耐低温性能更好;与聚氧四亚甲基二醇(PTMG)相比,聚酯型聚己二酸丁二醇酯二醇(PBAG)更易结晶。结晶尺寸在纳米级,材料的透明性可达85％以上。软段含量增加对软段区的结晶影响较小,但力学性能下降明显。混合多元醇的加入进一步提高了聚氨酯弹性体的微相分离程度,有利于软段结晶,在宏观上表现为拉伸强度和弹性模量明显增加。     

Transparent cyclic olefin copolymer/silica nanocomposites

In this work, melt blending of fumed nanosilica with cyclic olefin copolymer (COC) was carried out to prepare high strength transparent composites. The effects of various loadings (1, 2, 3 and 5 wt%) of nanosilica on the physical, mechanical, dynamic mechanical, thermal, tribological and optical properties of the COC composites were investigated in detail. The tensile test results showed that the nanocomposite with 3 wt% nanosilica content provides the highest tensile strength (55.6 MPa) compared with the nanocomposite with 5 wt% nanosilica content (54.6 MPa), which is believed to be significantly dependent on better dispersion. Moreover, the glass transition temperature (from tan δ) increased from 184 °C for pure COC to 194.3 °C for the COC composite with 3 wt% nanosilica. The scratch test and nano‐indentation results showed that addition of nanosilica increased the stiffness and hardness of the composite, providing higher scratch resistance and lower frictional coefficient. UV?visible spectroscopy measurements showed that the nanocomposites have excellent optical transparency which is similar to that of the pure COC film. © 2013 Society of Chemical Industry     

Preparation,Mechanical and Thermal Properties of Polyurethane/Nanosilica Composites via High Pressure Shearing Methods

Nanosilica particles were dispersed into polymer diols by high pressure shearing homogenizer (HPSH), then polyurethane nanocomposites were prepared via in-situ polymerization of diphenylmethane diisocyanate (MDI) and polymer diols. FTIR analysis indicated that the -NCO groups of MDI had reacted with the hydroxy on the surface of nanosilica during in-situ polymerization. TGA suggested that polyurethane/nanosilica composites obtained by in-situ polymerization had better thermal stability than pure polyurethane. Meanwhile, the tensile and dynamic mechanical properties of the samples prepared by HPSH were superior to those by directly ultrasonic dispersing nanosilica, accompanied by more homogeneous dispersion of nanosilica particles in the polymer matrix.     

Hydrogels based on polyurethane–polyacrylic acid multiblock copolymers via macroiniferter technique

Polyurethane (PU)–polyacrylic acid (PAAc) multiblock copolymers have been prepared via a macroiniferter technique, and were tested for living mechanism, thermal, and water swell of the cast films. It was found that molecular weight of the PU–PAAc block copolymers linearly increased while molecular weight distribution decreased with conversion. As the PAAc content increases, water swell of the cast films and crystalline melting temperature (T_m) of PU decreased while glass transition temperature of PU increased.     

丙烯酸树脂改性水性聚氨酯的结构与性能研究

采用丙烯酸树脂对水性聚氨酯进行改性，得到了共混改性（PU／PA）、共聚改性（PUA’）、接枝改性（PUA）3种丙烯酸改性水性聚氨酯聚合物。通过对改性聚氨酯乳液的激光粒度分析，乳胶膜的红外光谱、热分析、透明性、耐化学性及扫描电镜进行分析，结果表明：改性后的水性聚氨酯，各项性能均有不同程度的提高。在机械共混聚合物PU／PA体系中，聚氨酯分子链和丙烯酸树脂分子链间具有一定的相容性及共混性；在共聚反应聚合物PUA’、PUA体系中，聚氨酯分子链和丙烯酸树脂分子链形成核壳结构，且在PUA中，聚氨酯分子链和丙烯酸树脂分子链之间形成的化学键，可以有效的提高二者的相容性及共混程度。     

Performance properties of self-curing aqueous-based PU system with tri-glycidyl phosphate curing agent

Amino-terminated and carboxylic acid containing aqueous-based polyurethane (PU) dispersion was prepared by a conventional NCO-terminated PU prepolymer process by using isophorone diisocyanate (IPDI), polypropylene glycol-2000 (PPG-2000) and 2,2′-dimethylolpropanoic acid (DMPA) as the key raw materials. A new curing agent, tri-glycidyl phosphate (POG) was prepared from a substitution reaction of phosphorus oxychloride and glycidol. A single-component self-curable aqueous-based PU system is obtained from an addition of POG into aqueous-base PU dispersion and its curing reaction occurred among POG oxiranes and PU amino groups immediately after hydrophobic POG diffused into PU particles (as polymeric micelles). The cross-linked PU resins were resulted on drying at ambient temperature. Original PU dissolved into THF and ethanol. And its gel content increased to 90.1% and sample loss in ethanol decreased to 9.2% of this self-cured PU system with 5.0 phr POG. The limiting oxygen index (LOI) value is 20 of original PU and its LOI reached to 27 of this same self-cured PU system. The improved mechanical and thermal properties of those self-cured PU resins were evaluated, respectively in this report.