Polybutadiene-based Polyurethane Research Articles

Investigating the Effect of Chain Extender on the Phase Separation and Mechanical Properties of Polybutadiene-Based Polyurethane.

The thermodynamic incompatibility between the soft and hard segments of thermoplastic polyurethane (TPU) results in a microphase-separated behavior and excellent mechanical properties. However, the effect of the chain extender on the degree of microphase separation (DMS) and the resultant mechanical properties of TPU have not been well studied because of the complex interactions between the soft and hard segments. Herein, hydroxyl-terminated polybutadiene-based TPUs(HTPB-TPUs) without hydrogen bonding between the soft and hard segments are synthesized using hydroxyl-terminated polybutadiene, toluene diisocyanate, and four different chain extenders, and the effect of the chain extender structure on DMS is analyzed experimentally using a combination of analytical techniques. Furthermore, the solubility parameters of the soft and hard segments, glass transition temperatures, and hydrogen-bond density of the HTPB-TPUs, are computed using all-atom molecular dynamics simulations. The results clearly reveal that the chain extender significantly affects the DMS and thus the mechanical properties of HTPB-TPUs. This study paves the way for studying the relationship between the structure and properties of TPU.

Acoustically transparent polybutadiene-based polyurethane encapsulants for deep-sea and transducers

Copolyether polyurethane (PUR), as a typical encapsulation material, is widely used for underwater acoustic transducers. Two novel types of polybutadiene-based PURs were prepared using a one-step method and compared with copolyether PURs. The polybutadiene-based PUR exhibited excellent mechanical properties. Epoxidized hydroxyl-terminated polybutadiene (EHTPB)–based PUR exhibited tensile strength and hardness of up to 17.3 MPa and Shore A95, respectively, which were 76.5% and 13.3% higher than those of copolyether PURs. The molecular chain of hydroxyl-terminated polybutadiene (HTPB)-based PUR exhibited good flexibility, a soft segment glass transition temperature (Tg) (approximately -52 °C), and complete microphase separation. Compared with HTPB-based PUR, EHTPB-based PUR exhibited a higher molecular chain rigidity and a lower degree of microphase separation. The insertion losses of HTPB-based PUR at 350 and 700 kHz were 69.8 dB/m and 204.6 dB/m, respectively, which were 57.4% and 47.1% lower than those of copolymer PUR. The water absorption and water vapor transmission coefficient of HTPB-based PUR were an order of magnitude lower than those of copolymer PUR. EHTPB-based and copolymer PURs exhibited similar insertion losses at 350 kHz. EHTPB-based PUR exhibited the lowest water vapor transmission coefficient of 7.2 × 10−14 g·cm/cm2·s·Pa, which was approximately 1/15th of that of copolyether PUR.

Optical Active Thermal Stable Nanocomposites Using Polybutadiene-Based Polyurethane and Graphene Quantum Dot-MnO2

Synthesis and characterization of new polybutadiene-based polyurethane, graphene quantum dot-MnO2 nanoparticles, and relative nanocomposites were set as the aim of current artwork. For this purpose, a one-pot polymerization approach was employed in preparation of polyurethane through the reaction of amine polyol and toluene diisocyanate (TDI) in presence of DBTDL catalyst. Nanocomposites were synthesized using 1 to 3 incorporation percent of graphene quantum dot-MnO2 nanoparticles in polymer matrix. 1H-NMR and FT-IR spectroscopies confirmed successful synthesis of reaction products including graphene quantum dot-MnO2, polyurethane, and nanocomposites. UV-vis and PL spectrophotometry techniques were applied for achieving optical information of samples. Optical properties of nanocomposites were reserved properly with no great quenching. Thermal stabilities, degradation rates, and thermal characteristics of polyurethane and nanocomposites were investigated using TGA/DTG and DSC analysis. Thermal stability showed direct relationship to nanoparticle content, and 3%wt nanocomposite showed improved thermal behaviour in comparison with pure PU. SEM, XRD, and AFM techniques proved successful nanocomposite synthesis with detecting nanoparticle species and fine nanoparticle dispersion with improved topographic and morphologic characteristics making GQD-MnO2 polyurethane nanocomposites a good candidate for using in optical active and thermal stable coatings.

Hydroxyl-Terminated Polybutadiene-Based Polyurethane with Self-Healing and Reprocessing Capabilities.

Hydroxyl-terminated polybutadiene (HTPB)-based polyurethane (PU) networks play indispensable roles in a variety of applications; however, they cannot be reprocessed, resulting in environmental problems and unsustainable industrial development. In this work, recyclable HTPB-based PU vitrimer (HTPB-PUV) networks are fabricated by introduction of a cross-linker 2,2′-(1,4-phenylene)-bis[4-mercaptan-1,3,2-dioxaborolane] (BDB) with dynamic boronic ester bonds into the network. Meanwhile, the BDB can stabilize the HTPB unit in the network by elimination of double bonds. The novel HTPB-PUV networks are constructed by a thiol-ene “click” reaction and an addition reaction between HTPB and cross-linker BDB and isocyanates (HDI). The dynamic HTPB-PUV networks are characterized by dynamic mechanical analysis (DMA) and Fourier transform infrared (FTIR). The obtained dynamic HTPB-PUV networks possess superior thermostability. Moreover, due to the presence of dynamic boronic ester bonds, the HTPB-PUV network topologies can be altered, contributing to the reprocessing, self-healing, and welding abilities of the final polymer. Through a hot press, the pulverized sample can be reprocessed for several cycles, and mechanical properties of the reprocessed samples are similar to those of the pristine one, with the tensile strength being even higher. The self-healed sample exhibits almost complete recovery from scratch after the healing treatment at 130 °C for 3 h. Moreover, a welding efficiency of 120% was achieved.

Effect of Hollow Silica Microspheres on Compressive and Dynamic Mechanical Properties of Hydroxyl-Terminated Polybutadiene-Based Polyurethane Composites.

Porous polyurethane composites containing hollow silica microspheres were prepared by one-step bulk polymerization to study cyclic compressive and dynamic mechanical properties of the composites. Cyclic compression testing was conducted to record the stress versus strain curves during the loading and unloading cycles and in order to study the compressive behavior and time-dependent recovery of the composites. Effect of frequency on the dynamic mechanical properties of the composites was also evaluated using dynamic mechanical analysis. Master curves were constructed based on time-temperature superposition principle in order to show long-term dynamic mechanical behavior of the composites.

Influence of microstructural variations on morphology and separation properties of polybutadiene-based polyurethanes.

Polybutadiene-based polyurethanes with different cis/trans/1,2-vinyl microstructure contents are synthesized. The phase morphology and physical properties of the polymers are investigated using spectroscopic analysis (FTIR and Raman), differential scanning calorimetry (DSC), X-ray scattering (WAXD and SAXS) and atomic force microscopy (AFM). In addition, their gas transport properties are determined for different gases at 4 bar and 25 °C. Thermodynamic incompatibility and steric hindrance of pendant groups are the dominant factors affecting the morphology and properties of the PUs. FTIR spectra, DSC, and SAXS analysis reveal a higher extent of phase mixing in high vinyl-content PUs. Moreover, the SAXS analysis and AFM phase images indicate smaller microdomains by increasing the vinyl content. Smaller permeable soft domains as well as the lower phase separation of the PUs with higher vinyl content create more tortuous pathways for gas molecules and deteriorate the gas permeability of the membranes.

A novel synthesis of polybutadiene-based polyurethane binder and conductive graphene–polyurethane nanocomposites: a new approach to polybutadiene recycling

Synthesis and characterization of a new class of polybutadiene polyol polyurethanes were investigated with three consecutive reactions, namely polybutadiene (PB) chain cleavage by a two-step oxidation reaction using meta-chloroperbenzoic acid (m-CPBA) and periodic acid (H5IO6) in order to prepare polybutadiene polyol precursor, continued by telechelic amine polyol synthesis by an amination reaction using diethanolamine (DEA) in the presence of sodium borohydride (NaBH4) and finally telechelic polyurethane preparation by the reaction of synthesized polyol and toluene diisocyanate (TDI). Nanocomposites were prepared through an in situ polymerization reaction by incorporation of 1–3 wt% of graphene conductive nanosheets. Successful structural elucidation of the synthesized polymeric binder and nanocomposites was investigated by using well-known methods. TGA analysis revealed slower degradation and moderate thermal stability in higher weight percent nanocomposite. SEM images and XRD patterns resulted in fine nanoparticle distribution, lack of agglomeration and approximately constant nanoparticle size. Conductometry confirmed higher electrical conductivity data for nanocomposites by increasing graphene nanosheet contents.

Investigations of effect of hydroxyl-terminated polybutadiene-based polyurethane binders containing various curatives on thermal decomposition behaviour and kinetics of energetic composites

An energetic composite of an octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine with a polymer matrix is generally developed to reduce sensitivity, improve mechanical strength and furnish engineering shape. A hydroxyl-terminated polybutadiene (HTPB) and various curatives, namely methylene diphenyl diisocyanate (MDI), isophorone diisocyanate (IPDI), toluene diisocyanate (TDI) and trimethyl-hexamethylene diisocyanate (TMDI), were mixed in 1:1 [NCO]/[OH] equivalent ratio to form polyurethane, and these samples were designated by HTPB/MDI, HTPB/IPDI, HTPB/TDI and HTPB/TMDI, respectively. The four kinds of energetic composites were prepared by mixing of an energetic HMX with various HTPB/MDI, HTPB/IPDI, HTPB/TDI and HTPB/TMDI matrices. These composites were studied for the thermal stability by employing thermogravitry analysis (TGA) and found to be almost similar. The kinetic parameters of all kinds of composites were investigated through the isoconversional Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods for the first and second stages of the thermal decomposition using TGA data. The results of the activation energy obtained from the FWO method were analogous to those values obtained from the isoconversional KAS method. In addition, the kinetic parameters were also investigated through isoconversional KAS method using DSC data. The overall values of the activation energy of the HMX/HTPB/MDI, HMX/HTPB/IPDI, HMX/HTPB/TDI and HMX/HTPB/TMDI samples were varied in a range of 168–263, 277–409, 210–421 and 206–324 kJ mol−1 at a constant value of conversion (α = 0.1–0.9), respectively. The results indicated that there was significant variation in the activation energy with varying curative groups in the HTPB-based PU matrices. The compensation effect method was used to calculate the pre-exponential factor. The energetic composites were also investigated for the thermodynamic parameters for formation of the activated complexes and are discussed.

Mechanical and Swelling Properties of Hydroxyl-Terminated Polybutadiene-Based Polyurethane Elastomers

The mechanical and swelling properties of an elastomeric polyurethanes have been studied. The elastomers were composed of hydroxyl-terminated polybutadiene, the chain extended with either glyceryl monoricinoleate, neopentyl glycol, trimethylolpropane and cured with toluene diisocyanate and 4,4′-methylene diphenyl diisocyanate. The mineral fillers under study were nanoclay, TiO2, ZrO2 and ZnO. Gel fraction, crosslinking degree and average molecular weight between crosslinks were calculated from the swelling data. The hydrogen bonding index, which is a measure of hydrogen bonding, was calculated from infrared spectrophotometric data. The most remarkable result was that crosslink density diminished for a nanoclay polyurethane nanocomposite compared to an unfilled sample. Samples with nanoclay exhibited an unusual inverse correlation between crosslink density and tensile strength. Our findings showed that nanoclay in particular is an effective inorganic filler that can modulate the microstructural and mechanical behavior of polyurethane elastomers for tuned applications.

Mechanical and Thermal Insulation Properties of Porous Silica/Polyurethane Composites.

Porous hydroxyl-terminated polybutadiene-based polyurethane (HPU) composites containing various hollow glass microspheres (HGMs) up to 75 vol.% were synthesized by one-step bulk polyaddition-type polymerization. An unfilled (non-porous) HPU sample was also prepared as a reference. The thermal conductivity of the HPU/HGM composites, which are considered as a three-phasic material composed of a bulk HPU matrix, silicate thin layer, and pores, could be predicted perfectly by the Felske model. The thermal properties, such as Tg and thermal stability, of the HPU/HGM composites were affected slightly by the addition of HGMs compared to the unfilled HPU. On the other hand, the shell thickness and volume of the HGMs played an important role in determining the mechanical properties of the composites leading to reinforcement with increasing wall thickness and content of HGMs.

Micro and nanocomposites of polybutadienebased polyurethane liners with mineral fillers and nanoclay: thermal and mechanical properties

AbstractMicro and nanocomposites of hydroxyl terminated polybutadiene (HTPB)-based polyurethanes (NPU) were obtained using five mineral fillers and Cloisite 20A nanoclay, respectively. Samples were prepared by the reaction of HTPB polyol and toluene diisocyanate (TDI), and the chain was further extended with glyceryl monoricinoleate to produce the final elastomeric polyurethanes. Mechanical and thermal properties were studied, showing that mineral fillers (20%w/w) significantly increased tensile strength, in particular nanoclay (at 5% w/w). When nanoclay-polymer dispersion was modified with a silane and hydantoin-bond promoter, elongation at break was significantly increased with respect to NPU with C20A. Thermal properties measured by differential scanning calorimetry (DSC) were not significantly affected in any case. The molecular structure of prepared micro and nanocomposites was confirmed by Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. Interaction of fillers with polymer chains is discussed, considering the role of silanes in compatibilization of hydrophilic mineral fillers and hydrophobic polymer. The functionalization of nanoclay with HMDS silane was confirmed using FTIR. Microstructure of NPU with C20A nanoclay was confirmed by Atomic Force Microscopy (AFM).

Ablation and fire-retardant properties of hydroxyl-terminated polybutadiene-based polyurethane-g-polyhedral oligomeric silsesquioxane composites

This study examined the ablation and flammability of hydroxyl-terminated polybutadiene-based polyurethane composites grafted by polyhedral oligomeric silsesquioxane (HTPB-based PU- g-POSS) that were prepared by a one-step PU reaction using the HTPB prepolymer, two types of reactive POSS diol, and isophorone diisocyanate. The ablation property was measured using an oxyacetylene torch, and the ablation rate and relative ablation resistivity were evaluated. The results show that POSS molecules incorporated chemically into the HTPB-based PU matrix make a positive contribution to the ablative resistance. POSS molecules in the HTPB-based PU composites exhibited distinct microphase separation, aggregating into a spherical shape on the nanometer scale. This morphology of the POSS domain in the HTPB-based PU matrix leads to the formation of densely accumulated spherical silica (SiO2) droplets on the top of the ablated surface of materials under thermally oxidative conditions during ablation, resulting in improved ablation resistance compared with pristine HTPB-based PU. This unique SiO2-forming ability of POSS molecules can also enhance the flame-retardant behavior of the composites, as illustrated by the limited oxygen index and cone calorimeter measurements.

Synthesis and properties of hydroxyl-terminated polybutadiene-based polyurethanes reinforced with polyhedral oligomeric silsesquioxanes.

Polyurethane/polyhedral oligomeric silsesquioxane (PU/POSS) hybrid composites are prepared by a one-step PU reaction using hydroxyl-terminated polybutadiene (HTPB) prepolymer, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS molecule. The effect of incorporation of functionalized POSS molecules covalently bonded or physically blended into PU matrix is investigated in terms of mechanical reinforcement and thermal stability of these resulting PU/POSS hybrid composites. PU/POSS hybrid composites prepared with reactive POSS molecules exhibit the mechanical reinforcement while maintaining low glass transition temperataure (T(g)), probably due to the fact that reactive POSS molecules chemically incorporated in PU are aggregated to crystallize, effectively working as a physical crosslinking in PU/POSS hybrid composites. This can be advantageous in that mechanical reinforcement of PU/POSS hybrid composites can be achived without sacrificing the low temperature properties of these composites. However, the contribution of POSS molecules incorporated covalently into PU matrix is virtually absent on the thermal decomposition temperature (T(d,max)) measured using TGA/DTG. Thermal degradation behavior of these hybrid composites in the early stage rather appears to depend preferably on characteristics of POSS molecules incorporated.

Vinyl-modified hyperbranched polyether cross-linked hydroxyl-terminated polybutadiene-based polyurethane membrane for pervaporation recovery of butanol

Hyperbranched polyether was synthesized and vinyl modified using the one-pot method and characterized by Fourier transform infrared spectroscopy (FTIR), hydrogen nuclear magnetic resonance spectroscopy, and thermogravimetric analysis (TGA). The as-obtained polyether was used to cross-link hydroxyl-terminated polybutadiene-based polyurethane (PU). The PU was characterized by FTIR, TGA, scanning electron microscopy, water contact angle, tensile tests, and swelling properties. The PU was used in pervaporation (PV) recovery of butanol from its dilute aqueous solution. The PV performance was determined using the separation factor ( α) and permeate flux ( Fp). With a membrane thickness of 31 μm, the separation factor of the membrane was up to 10.2 with a total flux of 320.7 g m−2 h−1 at 70°C.

One-pot synthesis of hyperbranched polyols and their effects as crosslinkers on HTPB-based polyurethane

Hyperbranched polyethers and hyperbranched poly(amino ester)s were synthesized through one-pot method, and characterized by fourier transform infrared spectroscopy, hydrogen nuclear magnetic resonance and thermogravimetry analysis (TGA). The as-obtained hyperbranched polyols with different molecular structure and sizes were used to crosslink hydroxyl-terminated polybutadiene-based polyurethane (PU). The PU was characterized by tensile test, dynamic mechanical analysis, TGA, and swelling properties. It was found that the crosslinker structure and size have great effects on the properties of the PU. Hyperbranched polyether cross-linked PU showed the best mechanical properties, which reached mechanical strength of 1.45 MPa with elongation at break of 617 % for the third generation with hard segment content of 26.8 % at 25 °C.

The effect of thiolation on the mechanical and protein adsorption properties of polyurethanes

Segmented polyurethanes are important polymers for a number of industrial and technological applications. The purpose of this work was to synthesize polybutadiene-based polyurethanes and subsequently graft carboxylate and sulfonate side chains via thiol-ene reaction. Spectroscopic investigations showed that grafting yielded good conversion for the vinyl unsaturation of the polybutadiene soft segment. DSC and tensile testing revealed that grafted polyurethanes had a better segmental compatibility and superior mechanical properties than the control polyurethane without grafting. The carboxylic side chains of the soft segment were responsible for the observed improved mechanical properties. Initial protein adsorption tests on these polymers were found to be higher than the control surface. The polyurethanes of the current study could be used for biomedical applications where protein attachment to the surface is needed for specific cell adhesion and tissue repair.

Evaluation of tg data of htpb-based polyurethanes

Thermogravimetry (TG) was used to provide some new information on some polybutadiene-based polyurethanes. The results showed two main mass decomposition stages, from 230 to 564°C. The first mass loss stages were used to quantify the hard segments of the polymers. The results correlated well with the ASTM methodology. In addition, two 23 factorial design studies were applied to evaluate the importance of some selected factors on the TG results of the polyurethanes.

Synthesis and Structure - Property Relations of Latexes Containing Graft Copolymers between Telechelic Polybutadiene and Dodecyl Methacrylate

Latexes comprising novel copolymers were formed by second-stage emulsion polymerization of dodecyl methacrylate (DMA) onto a hydroxylated polybutadiene-based polyurethane prepolymer (PUD) as seed latex, with persulfate initiator. Morphology data from TEM imaging (including chemical fixation ultra-microtoming), glass transition temperature, dynamic mechanical analysis, and other mechanical-property data were all consistent with a system showing extensive grafting and compatibilization between the different polymeric components. Water adsorption and AFM measurements showed that samples with poorer film-forming properties had higher water sensitivity, greater mixing of the polymer phases, and poorer mechanical properties. These properties were related to a phase-inversion phenomenon occurring above a critical dodecyl methacrylate/prepolymer ratio. The compatibilization of the PUD and poly(DMA) given by these modifications resulted in a product with increased tackiness, although with a higher water sensitivity.

Diffusion behavior of hexane in diamine chain-extended hydroxyterminated polybutadiene based polyurethanes

A new method of edge correction has been formulated to calculate the near true diffusion coefficient of hexane in thin polyurethane and polyurethaneurea sheets. The method involves the calculation of time-average thickness during the diffusion of hexane in hydroxyterminated polybutadiene-based polyurethane and polyurethaneurea sheets. The precision of the method has been tested by the iteration of data. The diffusion coefficient increases with the increase of diamine chain extender in polyurethaneureas. The variation of activation parameters and enthalpy of diffusion of hexane with diamine chain extender in polyurethaneurea also have been studied. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 90–97, 2002

Thermomechanical properties and morphology of interpenetrating polymer networks of polyurethane–poly(methyl methacrylate)

AbstractInterpenetrating networks (IPNs) of polybutadiene‐based polyurethane (PU) and poly(methyl methacrylate) (PMMA) were synthesized. The effect of the incorporation of 2% glycidyl methacrylate (GMA) and 2‐hydroxyethyl methacrylate (2‐HEMA) on the thermal, mechanical, and morphological properties of IPNs was investigated. Both 2‐HEMA and GMA led to improvements in these properties. However, 2‐HEMA‐containing IPNs showed somewhat better tensile strength, elongation, and damping characteristics. The morphology of IPNs containing 2‐HEMA showed better mixing of the components. The improvement in the properties was observed for up to 40% PMMA in the IPNs. Differential scanning calorimetry thermograms showed the presence of three glass transitions. The third glass‐transition temperature was explained by possible grafting of methyl methacrylate onto PU. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1576–1585, 2002