Rheology, morphology and mechanical properties of compatibilized poly(vinylidene fluoride) (PVDF)/thermoplastic polyurethane (TPU) blends

Compatibilized blends of poly(vinylidene fluoride) (PVDF) and thermoplastic polyurethane (TPU) were developed using maleated PVDF (PVDF-g-MA). Excellent compatibilization between PVDF and TPU was demonstrated by theological, morphological, and mechanical measurements. The introduction of PVDF-g-MA into the PVDF/TPU blends caused an increase in viscosity and storage modulus. Much finer morphology was clearly observed by SEM. The tensile tests showed that the tensile strength and ultimate elongation achieved a significant improvement with addition of PVDF-g-MA.

Scanning Electron Microscopy Studies on Tear and Wear Failure of Short Kevlar Fiber-Thermoplastic- Polyurethane Composite

Tear and wear properties of short kevlar fiber, thermoplastic polcurethane (TPU) composite with respect to fiber loading-and fiber onentation has been studied and the fracture surfaces were examined under scanning electron microscope (SEM). Tear strength first decreased up to 20 phr fiber loading and then gradually increased with increasing fiber loading. Anisotropy in tear strength was evident beyond a fiber loading of 20 phr. Tear fracture surface of unfilled TPU showed sinusoidal folding characteristics of high strength matrix. At low fiber loading the tear failure was mainly due to fibermatrix failure whereas at higher fiber loading the failure occurred by fiber breakage. Abrasion loss shows a continuous rise with increasing fiber loading, the loss in the transverse orientation of fibers being higher than that in the longitudinal orientation. The abraded surface showed lone cracks and ridges parallel to the direction of abrasion indicating an abrasive wear mechanism. In the presence of fber the abrasion loss was mainly due to fiber low.

Polymer nanocomposites based on P3OT, TPU and SWNT: preparation and characterization

Single walled carbon nanotubes (SWNTs) were incorporated in polymer nanocomposites based on poly(3-octylthiophene) (P3OT), thermoplastic polyurethane (TPU) or a blend of them. Thermogravimetry demonstrated the success of the purification procedure employed in the chemical treatment of SWNTs prior to composite preparation. Stable dispersions of SWNTs in chloroform were obtained by non-covalent interactions with the dissolved polymers. Composites exhibited glass transitions, melting temperatures and heat of fusion which changed in relation to pure polymers. This behavior is discussed as associated to interactions between nanotubes and polymers. The conductivity at room temperature of the blend (TPU-P3OT) with SWNT is higher than the P3OT/SWNT composite.

The investigation of exfoliation process of organic modified montmorillonite in thermoplastic polyurethane with different molecular weights

Cloisite 30B (30B) was melt-mixed with two kinds of thermoplastic polyurethane (TPU) with different molecular weights to discern the roles of molecular diffusion and shear in the exfoliation process. The higher level of exfoliation was achieved in TPU matrix with higher molecular weight due to the appropriate viscosity. In order to have an insight into the mechanism of exfoliation, the degree of dispersion and exfoliation of 30B was characterized by wide angle X-ray diffraction and transmission electron microscopy. The layers of 30B were exfoliated via a slippage process, which was also observed in polyamide 12 nanocomposites recently.

A strategy of fabricating exfoliated thermoplastic polyurethane/clay nanocomposites via introducing maleated polypropylene

By reducing the attraction between the platelets of octaclecylammonium chloride modified montmorillonite (OMMT-C18) via pre-intercalation of maleated polypropylene (MAPP), OMMT-C18 was exfoliated in thermoplastic polyurethane (TPU) matrix during melt-mixing. Wide angle X-ray diffraction, transmission electron microscopy and thermogravimetric analysis were used to investigate the microstructure of TPU nanocomposites. Three factors (including introducing sequence, the kind and the content of MAPP) showed important effects on the dispersion degree of OMMT-C18 in TPU matrix. The results confirmed that the pre-intercalation of MAPP was necessary for the exfoliation of OMMT-C18; however, the role of MAPP in TPU nanocomposites was different from that in polypropylene nanocomposites.

Syndiotactic polystyrene/thermoplastic polyurethane blends using poly(styrene-b-4-vinylpyridine) diblock copolymer as a compatibilizer

The effect of adding diblock copolymer poly(styrene-b-4-vinylpyridine) (P(S-b-4VPy), to immiscible blends of syndiotactic polystyrene (sPS)/thermoplastic polyurethane (TPU) on the morphology, thermal transition, crystalline structure, and rheological and mechanical properties of the blends has been investigated. The diblock copolymer was synthesized by sequential anionic copolymerization and was melt-blended with sPS and TPU. Scanning electron microscopy (SEM) showed that the added block copolymer reduced the domain size of the dispersed phase in the blends. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the extent of compatibility between sPS and TPU affected the crystallization of the sPS in the blends. Tensile strength and elongation at break increased, while the dynamic modulus and complex viscosity decreased with the amount of P(S-b-4VPy) in the blend. The compatibilizing effect of the diblock copolymer is the result of its location at the interface between the sPS and the TPU phases and penetration of the blocks into the: corresponding phases, i.e. the polystyrene block enters the noncrystalline regions of the sPS, and the poly(4-vinylpyridine) block interacts with TPU through intermolecular hydrogen bonding. (C) 1999 Elsevier Science Ltd. All rights reserved.

STUDIES ON COMPATIBILIZATION OF POLYPROPYLENE THERMOPLASTIC POLYURETHANE BLENDS AND MECHANISM OF COMPATIBILIZATION

This paper reports a study of compatibilization and the mechanism of compatibilization of polypropylene (PP)/thermoplastic polyurethane (TPU) blends with maleated polypropylene (PP-MA) and its graft copolymer with polyethylene oxide (PEO), (PP-MA)-g-PEO.

Rotational moulding of thermoplastic polyester urethanes

Various grades of Thermoplastic Polyurethane (TPU) supplied by Bayer were studied to determine their suitability for the rotational moulding process. Following grinding, parts were produced using a variety of peak internal air temperatures and cooling rates. The tensile and impact properties of these parts were then analysed and it was found that both the grade and moulding conditions had a large bearing on the quality and mechanical strength of the part produced.

Self adhesion of short Kevlar fibre -thermoplastic polyurethane composite

The self adhesion behaviour of thermoplastic polyurethane (TPU) in itself and its composite with short Kevlar fibre with respect to contact time, temperature, pressure, and fibre loading has been studied. The adhesion strength showed two linear increments of different slopes with respect to the square root of time: with temperature and pressure of contact, the adhesion strength was improved. The maximum strength was obtained with 20 phr of short fibre in only one of the mating substrates in the peel test sample. The duration for wetting and diffusion was shifted to longer time intervals with fibres loaded in both the substrates.

Studies on the Effect of an External Flaw on the Tensile Strength of Short Kevlar Fiber-Thermoplastic Polyurethane Composites

The effect of an external flaw on the tensile strength of short kevlar fiber-thermoplastic composites has been studied with respect to fiber content, fiber orientation, location of the external flaw, and the temperature of test. The composites showed a three-step reduction in tensile strength with increasing flaw size. The critical flaw-length region was shifted to higher flaw-size levels with increasing fiber content. With increasing temperature, the critical flaw length was increased in the case of unfilled TPU, whereas it remained more or less constant in the case of short kevlar fiber-filled-TPU composite.

Studies on the Flammability of Short Kevlar Fiber-Thermoplastic Polyurethane Composite

The flammability of short Kevlar aramide fiber-thermoplastic polyurethane (TPU) has been investigated with respect to fiber loading and various flame retardant additives such as halogen containing polymers, antimony oxide/chlorine donor combination, zinc borate, and aluminum hydroxide. Smoke generation was reduced drastically, while the oxygen index was reduced marginally in the presence of short fibers. The best improvement in the oxygen index was obtained with antimony oxide/chlorinated paraffin wax combination, in the weight ratio 1:6. A 70 phr loading of aluminum hydroxide improved LOI and reduced smoke generation.

Thermal degradation of short kevlar fibre thermoplastic polyurethane composite

The thermal degradation of short kevlar fibre-thermoplastic polyurethane (TPU) composites has been studied by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). TGA showed that the thermal degradation of TPU takes place in two steps with peak maxima (T1max and T2ma,) at 383°C and 448°C, respectively. In the presence of 10-40 phr of short kevlar fibres, T1_ and T2max were shifted to lower temperatures. The temperature of onset of degradation was increased from 245 to 255°C at 40 parts per hundred rubber (phr) fibre loading. Kinetic studies showed that the degradation of TPU and kevlar-TPU composite follows first-order reaction kinetics. The DSC study showed that there is an improvement in thermal stability of TPU in the presence of 20 phr of short kevlar fibres.

Preparation and property testing of compatibilized poly(l-lactide)/thermoplastic polyurethane blends

Poly(l-lactide) (PLL) has been blended with a polycaprolactone-based thermoplastic polyurethane (TPU) elastomer as a toughening agent and a poly(l-lactide-co-caprolactone) (PLLCL) copolymer as a compatibilizer. Both 2-component (PLL/TPU) and 3-component (PLL/TPU/PLLCL) blends were prepared by melt mixing, characterized, hot-pressed into thin sheets and their tensile properties tested. The results showed that, although the TPU could toughen the PLL, the blends were largely immiscible leading to phase separation. However, addition of the PLLCL copolymer improved blend compatibility. The best all-round properties were found for the 3-component blend of composition PLL/TPU/PLLCL = 90/10/10 parts by weight.

Enhancement of thermal stability, strength and extensibility of lipid-based polyurethanes with cellulose-based nanofibers

Cellulose was extracted from lignocellulosic fibers and nanocrystalline cellulose (NC) prepared by alkali treatment of the fiber, steam explosion of the mercerized fiber, bleaching of the steam exploded fiber and finally acid treatment by 5% oxalic acid followed again by steam explosion. The average length and diameter of the NC were between 200-250 nm and 4-5 nm, respectively, in a monodisperse distribution. Different concentrations of the NC (0.1, 0.5, 1.0, 1.5, 2.0 and 2.5% by weight) were dispersed non-covalently into a completely bio-based thermoplastic polyurethane (TPU) derived entirely from oleic acid. The physical properties of the TPU nanocomposites were assessed by Fourier Transform Infra-Red spectroscopy (FTIR), Thermo-Gravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), X-Ray Diffraction (XRD), Dynamic Mechanical Analysis (DMA) and Mechanical Properties Analysis. The nanocomposites demonstrated enhanced stress and elongation at break and improved thermal stability compared to the neat TPU. The best results were obtained with 0.5% of NC in the TPU. The elongation at break of this sample was improved from 178% to 269% and its stress at break from 29.3 to 40.5 MPa. In this and all other samples the glass transition temperature, melting temperature and crystallization behavior were essentially unaffected. This finding suggests a potential method of increasing the strength and the elongation at break of typically brittle and weak lipid-based TPUs without alteration of the other physico-chemical properties of the polymer. (C) 2012 Elsevier Ltd. All rights reserved.

Fabrication of multifunctional graphene decorated with bromine and nano-Sb₂O₃ towards high-performance polymer nanocomposites

Despite great advances, it remains highly attractive but challenging to create high-performance polymeric materials combining excellent flame-retardancy and outstanding thermal, mechanical and electrical properties. We herein demonstrate a novel strategy for fabricating a multifunctional nano-additive (Br-Sb2O3@RGO) based on graphene decorated with bromine and nano-Sb2O3. Cone calorimetric tests show that incorporating 10 wt% Br-Sb2O3@RGO into thermoplastic polyurethane (TPU) strikingly prolongs the time to ignition and decreases the peak heat release rate by 72%. Besides, tensile strength and Young's modulus are enhanced by 37% and 820%, respectively. Meanwhile, the electric conductibility is increased by eleven orders of magnitude relative to the TPU matrix. This work provides a promising strategy for addressing the critical bottleneck with the existing flame retardants that only enhance flame retardancy at the expense of mechanical properties of polymeric materials. As-prepared high-performance TPU composites are expected to find many applications, especially in aerospace, tissue engineering, and cables and wires.