Polyether-based Thermoplastic Polyurethane Research Articles

Rheology, mechanical properties and peel adhesion of hot-melt adhesive based on thermoplastic polyurethane/nanosilica

A series of thermoplastic polyurethane hot-melt adhesive formulations have been synthesized by melt blending of polyether-based thermoplastic polyurethane and different nanosilica, C5, and C9 hydrocarbon loadings. Different analyses, including FESEM, tensile strength, rotational rheometry, T-peel strength with polyester fabric, and nitrogen gas permeability, are conducted to examine the properties of the prepared adhesive formulations. The results show that the addition of 0.25 wt% of nanosilica increased the tensile properties of the polyurethane slightly and improved the T-peel strength with the polyester fabric. On the other hand, adding 5 wt% of C5 hydrocarbon tackifier reduced the tensile properties a bit, reduced the storage and loss modulus, and increased the T-peel strength with the polyester fabric. On the other hand, adding the C9 tackifier reduced the tensile strength more than the counterpart formulation including C5, reduced the storage and loss modulus and increased the T-peel strength. A noteworthy result was that the addition of nanosilica in the presence of C5 or C9 tackifiers lowered the loss and storage modulus and complex viscosity Adhesive formulation with 5 wt% of C5 tackifier has the highest average and maximum peel strength with about 20 and 35% higher strength than neat TPU.

Effect of N2 plasticization on the crystallization of different hardnesses of thermoplastic polyurethanes

Dissolving gas in polymer caused them to plasticize and induced crystallization. As a result, the glass transition temperatures (Tg) and melting points (Tm) decreased and crystallinity changed. This study investigated the effect of N2 dissolution on the thermal behavior of polyether-based thermoplastic polyurethanes (TPUs). Although the affinity between the polymers and N2 is not strong, the solubility of N2 in TPU is below 3 wt% at pressures below 10 MPa and temperatures in the range of 190 °C~210 °C. A unique phenomenon is reported. Dissolving N2 in TPU reduced the melting point but decreased crystallinity.A weight-loss-based test showed that the N2 sorption increased with increased soft segment (SS) content. Annealing with N2 showed an apparent plasticizing effect on TPU with high SS content. The melting peak of imperfect ordered crystals, around 100 °C, completely disappeared. This research contributes to understanding the impact of N2 plasticization on TPU crystallization and the development of nitrogen foaming technology.

Testing thermoplastic elastomers selected as flexible three-dimensional printing materials for functional garment and technical textile applications

Three-dimensional printing has already been shown to be beneficial to the fabrication of custom-fit and functional products in different industry sectors such as orthopaedics, implantology and dental technology. Especially in personal protective equipment and sportswear, three-dimensional printing offers opportunities to produce functional garments fitted to body contours by directly printing protective and (posture) supporting elements on textiles. In this article, different flexible thermoplastic elastomers, namely, thermoplastic polyurethanes and thermoplastic styrene block copolymers with a Shore hardness range of 67A–86A are tested as suitable printing materials by means of extrusion-based fused deposition modelling. For this, adhesion force, abrasion and wash resistance tests are conducted using various knitted and woven workwear and sportswear fabrics primarily made of cotton, polyester or aramid as textile substrates. Due to polar interactions between thermoplastic polyurethane and textile substrates, excellent adhesion and high fastness to washing is observed. While fused-deposition-modelling-printed polyether-based thermoplastic polyurethane polymers keep their abrasion–resistant properties, polyester-based thermoplastic polyurethanes are more prone to hydrolysis and can be partially degraded if presence of moisture cannot be excluded during polymer processing and printing. Thermoplastic styrene compounds generally exhibit lower adhesion and abrasion resistance, but these properties can be sufficient depending on the requirements of a particular application. Soft thermoplastic styrene filaments can be processed down to a Shore hardness of 70A resulting in three-dimensional printed parts with good quality and comfortable soft-touch surface. Finally, three demonstrator case studies are presented covering the entire process to realize the customized and three-dimensional printed textile. This encompasses product development and fabrication of a textile integrated custom-fit back protector and knee protector as well as customized functionalization of a technical interior textile for improved acoustic comfort. In the future, printing material modifications by compounding processes have to be taken into account for optimized functional performance.

Scattering of X-rays during melting and solidification of thermoplastic polyurethane. Graphite as nucleating agent and stabilizer of the colloidal melt

Melting and solidification of thermoplastic polyurethanes (TPU) are monitored by X-ray scattering. The colloidal character of the typical material becomes unstable as soon as the hard domains (HD) are molten. Then the scattered intensity fluctuates considerably and “lost” photons are found at small scattering angles (Tyndall effect). In this temperature regime the material is a fluid. Competing homogenization and segregation processes appear to take place, which modulate the materials colloidal character.Monitored by SAXS and WAXS, TPU elastomers are melted and re-solidified (heating rate: 20 K/min, temperatures Tmax: 220 °C, 190 °C). Strong fluctuations in scattering intensity due to varying Tyndall effect are observed in most of our experiments. Here the typical effects are demonstrated on a polyether-based TPU with a hard segment content of 30%, whose colloidal melt is stabilized by adding 0.5% graphite. In the hot quiescent melt the morphology is characterized by density undulations. HD arrangement does not grow late. Graphite stabilizes the colloidal melt. It increases both the HD melting-temperature (from 185 °C to 210 °C) and the HD formation temperature (from 90 °C to 165 °C).

Structure analysis of polyether-based thermoplastic polyurethane elastomers by FTIR, 1H NMR and 13C NMR

ABSTRACTOne kind of unknown structure sequence and composition ratio of thermoplastic polyurethane elastomers were characterized by nuclear magnetic resonance spectroscopy, Fourier transformed infrared spectroscopy, and gel permeation chromatography (GPC). The results showed that the polyurethane (PU) was obtained from poly(tetramethylene glycol) (PTMG) as soft segment, 1,4-butanediol (BDO) as chain extender, and 4,4′-methylenediphenyl diisocyanate (MDI) as hard segment. Furthermore, the composition ratio of MDI:PTMG:BDO was 2.07:1.22:1.00. At last, the molecular weight of PU was determined by GPC, and the number average molecular weight (Mn) and weight average molecular weight (Mw) are 63,300 and 133,800 g mol−1, respectively.

Effects of chitosan fiber addition on the properties of polyurethane with thermo-responsive shape memory.

We investigated the effects of the addition of chitosan fiber (biomass nanofiber made by Sugino (BiNFi-s)) to polyether-based thermoplastic polyurethane (TPU) on material properties. BiNFi-s (2 and 5 wt %)/TPU composite materials were prepared via compression molding, and glass fiber (2 and 5 wt %)/TPU composite materials and plain TPU were also prepared for comparison. The glass transition temperature was analyzed using differential scanning calorimetry, and the crystal structure was investigated using X-ray diffraction. 20-mm-long test specimens with cross-sectional dimensions of 1 mm × 1 mm were cut from sheets of the composite materials, and three-point bending tests were carried out using a universal testing machine to investigate their mechanical properties and shape memory. The addition of BiNFi-s or glass fiber to TPU did not influence the glass transition temperature, although the crystal structure changed from semi-crystalline to amorphous. The elastic modulus increased 40% by the addition of 5 wt % BiNFi-s (2.31 MPa) compared with plain TPU (1.65 MPa), and these composites exhibited shape recovery with clinically relevant changes in temperature. The addition of 5 wt % BiNFi-s into TPU resulted in an improvement in the elastic modulus without any decrease in the shape memory effect. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1151-1156, 2017.

Surface grafting of carboxylic groups onto thermoplastic polyurethanes to reduce cell adhesion

The interaction of polymers with other materials is an important issue, being their surface properties clearly crucial. For some important polymer applications, their surfaces have to be modified. Surface modification aims to tailor the surface characteristics of a material for a specific application without affecting its bulk properties. Materials can be surface modified by using biological, chemical or physical methods. The aim of this work was to improve the reactivity of the thermoplastic polyurethane (TPU) material (Elastollan®) surface and to make its surface cell repellent by grafting carboxylic groups onto its surface. Two TPU materials were studied: a polyether-based TPU and a polyester-based TPU. The grafting efficiency was evaluated by contact angle measurements and by analytical determination of the COOH groups. Scanning electron microscopy (SEM) of the membranes surface was performed as well as cell adhesion tests. It was proved that the surfaces of the TPUs membranes were successfully modified and that cell adhesion was remarkably reduced.

Electrostrictive thermoplastic polyurethane-based nanocomposites filled with carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH): Properties and improvement of electromechanical activity

The impact of small amounts of carboxyl-functionalized multi-walled carbon nanotubes (MWCNT-COOH) added into a polyether-based thermoplastic polyurethane elastomer (TPU) was studied considering mainly on the morphological, mechanical, electrical and electrostrictive properties. The electrostrictive properties were measured by the analysis of the deformation response occurring under external electric fields E applied on 50 μm-thick films. Dielectric measurements were carried out in order to determine the percolation threshold fc, which was found near 1 v% loading. This volume fraction leads to a very high dielectric permittivity εr′ up to ≈330, i.e. about 50 times higher than that of the pure TPU, where εr′≈6–7.

Polyisobutylene-based thermoplastic polyurethanes exhibit significant phase mixing

We investigated the morphology of a series of thermoplastic polyurethanes (TPUs) based on polyisobutylene (PIB) diol. The TPUs were synthesized using PIB diol with the molecular weight of 2000 g/mol as the soft segment, with different chemical structures and weight fraction of the hard segment. Thermal properties and microphase separated structures of these TPUs were characterized by thermal analysis and X-ray scattering techniques and were compared with those of polyether-based TPUs. Our results showed significant phase mixing between the soft segment and hard segment in PIB-based TPUs. The degree of microphase separation of PIB-based TPUs was found to be comparable to or even lower than that of TPUs based on poly(tetramethylene oxide) (PTMO) with similar composition, depending on the chemical structure of the hard segment. Comparison of the morphology before and after post-annealing suggested that while most of the microphase separated structure of PIB-based TPUs has formed during thermal processing, post-annealing further promotes the phase mixing between HS and SS.

Optimization of the processing parameters in melt blending of thermoplastic polyurethane and poly dimethyl siloxane rubber

This article emphasizes the optimization of processing parameters required for the blending of polyether-based thermoplastic polyurethane (TPU) and poly dimethyl siloxane (PDMS) rubber. Taguchi methodology was adapted as a statistical tool in the design of experiment to optimize processing conditions on the basis of tensile strength and impact strength for 50:50 blend of TPU and PDMS. L9 (33) orthogonal array strategy was utilized for conducting the experiments. The experimental data were transformed into signal-to-noise ratios, based on which each processing parameter has been optimized. Measure of confidence of the results has been studied using standard statistical technique of analysis of variance. From the results, the processing conditions have been optimized.

Sequence Analysis of Polyether-Based Thermoplastic Polyurethane Elastomers by 13C NMR

In this Note we would like to report on the analysis of the microstructure of segmented polyurethanes by 13CNMRmaking use of the signals arising from nonprotonated aromatic carbons which appear to be sensitive to dyads sequence distribution. The polyurethanes here studied were obtained from poly(tetramethylene glycol) (PTMG) as macrodiol soft segment, 1,4-butanediol (BD) chain extender, and 4,40'-methylenediphenyl diisocyanate (MDI) as hard segment.The results obtained in this work provide a relatively simple and reliable method to determine the microstructure of MDI-based thermoplastic polyurethanes by means of the NMR technique.

Effects of compatibilizer and testing speed on the mechanical and morphology behaviors of co-continuous amorphous copolyester-polyoxymethylene blends

Co-continuous amorphous copolyester (PETG)/polyoxymethylene (POM) (50/50 wt%/wt%) blends were prepared using a twin screw extruder followed compression molding. Two types of thermoplastic polyurethane (TPU) (i.e., polyester-based and polyether-based) were used to compatibilize the blends system. The thermal properties were characterized by using differential scanning calorimetry (DSC). The mechanical properties of the co-continuous PETG/POM blends were studies through flexural and single-edge notch tensile test (SEN-T). The SEN-T test was performed at three different testing speeds; 1, 100, and 500 mm/min. Scanning electron microscope (SEM) was used to access the fracture surface morphology. The flexural strength of the PETG/POM blends was decreased in the presence of TPU. This was attributed to the elastomeric nature of the TPU. The compatibilizing effects of TPU on the PETG/POM blends were proven by moderate improvement in the fracture toughness and confirmed by the SEM observation. The SEN-T fractured surface of the compatibilized blends showed gross matrix shear yielding as compared to the uncompatibilized system. The Kc values of the PETG/POM blends decreased as the testing speed increased. The optimum toughening effect was observed in PETG/POM blends compatibilized with polyether-based TPU at testing speed of 100 mm/min. The polyether-based TPU is a more efficient compatibilizer, because the amount required is one-half that of the polyester-based counterpart to achieve the same Kc value. This was attributed to the elastomeric nature of the polyether-based TPU. The softer nature of polyether-based TPU could provide better toughening effect than the polyester-based TPU, which is relatively harder in nature. POLYM. ENG. SCI., 45:710–719, 2005. © 2005 Society of Plastics Engineers

Thermoplastic Polyurethanes Softening in 37°C N-Saline

ABSTRACTThe softening of thermoplastic polyurethane (TPU) in the body environment represents one of the major advantages of these biomaterials. Although the literature contains an abundance of hydrolytic stability data, almost no information exists describing the softening of these materials in the body. A series of polyether-based TPUs, consequently, was synthesized based on 4,4′-diphenylmethane diisocyanate/1,4-butanediol hard segment and polytetramethylene ether glycol soft segment and the effect of simulated body environment (37°C n-saline) was studied as a function of the hard segment content and the soft segment glycol molecular weight. A mechanism and phenomenological analysis of this softening are offered and discussed in terms of TPU morphology. Both water and heat, for example, plasticize the TPU to increase the chain mobility; in the body environment this results in a reversible reduction in elastic modulus.

Polyether Based Polyur Ethane Thermoplastic — Effect of the Hard Segment Content

A series of polyether-based thermoplastic polyure thanes, varying in hard segment content between 20 and 80 weight percent, was prepared using an (oxypropylene-oxyethy lene) diol of Mn = 2,000 and 4,4'-diphenyl methane diisocyanate (MDI) extended with 1,4-butanediol (BDO). Physical-mechanical, dynamic-mechanical and specific heat data are used to elucidate the behavior of these materials. The polyurethanes varied from soft elastomeric to high-modulus plastic.