Addition Of Thermoplastic Polyurethane Research Articles

Tailoring the physical properties of poly(lactic acid) through the addition of thermoplastic polyurethane and functionalized short carbon fibers

AbstractThe elevated brittleness of commercial grades of poly(lactic acid) (PLA) may limit their use in several engineering applications. Therefore, the aim of this work is to develop a PLA‐based material possessing well‐balanced stiffness and toughness. Composites were prepared by blending PLA with increasing contents (from 10 to 30 wt%) of a thermoplastic polyurethane (TPU) and a fixed concentration (5 wt%) of carbon fibers (CFs), to tune the mechanical properties of the resulting materials. In order to increase the interfacial adhesion between CFs and polymeric phase, CFs were subjected to an acidic modification, by treating them in solution of H2SO4 and HNO3. The prepared composites were characterized from a chemical, rheological, morphological, and thermo‐mechanical point of view. Fourier transform infrared spectroscopy showed that the fiber surface reactivity was significantly enhanced by the acid treatment, with the introduction of reactive functional groups on CFs. Rheological and dynamic‐mechanical tests confirmed that the introduction of acid‐treated CFs implied strong fiber–matrix interactions. Thanks to the presence of the acid treated CFs, an important increase in tensile modulus and maximum stress was obtained for all the compositions. In particular, samples containing 10 wt% of TPU showed +74% tensile modulus and +43% maximum stress with respect to the unfilled blends. Moreover, the elongation at break of PLA was significantly improved (+81%) with the addition of 30 wt% of TPU. It was therefore demonstrated that the adopted approach could be effective for the preparation of novel PLA‐based materials with tailorable and well‐balanced properties that could find application in various technological fields.

Morphological, Mechanical and Thermal Properties of Polybutylene Tetrephthalate‐Polyester Based Thermoplastic Polyurethane Blends

AbstractPolybutylene tetrephthalate (PBT)‐polyester based thermoplastic polyurethane (TPU) blends with varying percentages of TPU (10 %, 20 %, 30 %, 40 %) were prepared in order to improve impact strength of PBT to enhance its applications. The blends were prepared by melt mixing using a twin screw extruder. Based on morphological images, impact strength analysis and dynamical mechanical analysis, TPU was well dispersed in PBT polymer matrix. Studies using Differential Scanning Calorimetry indicate a decrease in crsytallinity on addition of 30 % TPU in PBT. Thermogravimetric analysis demonstrates that addition of TPU in PBT matrix increases the char content. PBT and TPU have a good interfacial adhesion, according to SEM investigations. Mechanical characteristics demonstrate that the inclusion of TPU in PBT matrix resulted in a significant increase in impact strength of about 208 %, with minor changes in tensile strength and tensile modulus. Change in glass transition temperature of the optimised blend was measured using DMA.

Investigation of continuous PAN nanofiber yarn produced with polymer additives

Nanofiber yarns were produced by electrospinning technique from polyacrylonitrile (PAN), thermoplastic polyurethane (TPU) added and polyvinylidene fluoride (PVDF) added PAN polymer solutions. The effects of the other polymers as additive to PAN nanofiber yarn are investigated. SEM, stress-strain characterizations were carried out. A sample plain fabric was woven from PAN nanofiber yarns to show that nanofiber yarns are feasible and can be integrated into conventional textile structures. Addition of the other polymers has increased the Young modulus by 40%, whereas TPU addition has increased the tenacity by 50% but TPU + PVDF addition has decreased the tenacity by half of only PAN. Breaking elongation was slightly decreased by the addition of TPU and PVDF polymers.

Evaluation of Effect of Thermoplastic Polyurethane (TPU) on Crumb Rubber Modified (CRM) Asphalt Binder.

Crumb rubber binder with thermoplastic polyurethane (TPU) has been experimented with to characterize the performance properties considering the workability, rutting, fatigue cracking and cracking resistance at low temperatures depending on the temperatures and aging states. Physical and rheological properties were evaluated to proceed with the study by applying Superpave asphalt binder testing and multi-stress creep recovery (MSCR). Based on the targeted experiments, the binder samples were produced at three aging states (original, short-term aged and long-term aged) using a rolling thin film oven (RTFO) and pressure aging vessel (PAV). The results revealed that (i) the addition of TPU into CRM binders has a potential effect on increasing viscoelasticity at the original condition, (ii) CRM binders containing TPU showed improved anti-aging performance based on results of RTFO residues and (iii) the inclusion of TPU made it possible for CRM asphalt binder to improve its fatigue and cracking resistance at low temperature.

Effect of the Molecular Structure of TPU on the Cellular Structure of Nanocellular Polymers Based on PMMA/TPU Blends.

In this work, the effects of thermoplastic polyurethane (TPU) chemistry and concentration on the cellular structure of nanocellular polymers based on poly(methyl-methacrylate) (PMMA) are presented. Three grades of TPU with different fractions of hard segments (HS) (60%, 70%, and 80%) have been synthesized by the prepolymer method. Nanocellular polymers based on PMMA have been produced by gas dissolution foaming using TPU as a nucleating agent in different contents (0.5 wt%, 2 wt%, and 5 wt%). TPU characterization shows that as the content of HS increases, the density, hardness, and molecular weight of the TPU are higher. PMMA/TPU cellular materials show a gradient cell size distribution from the edge of the sample towards the nanocellular core. In the core region, the addition of TPU has a strong nucleating effect in PMMA. Core structure depends on the HS content and the TPU content. As the HS or TPU content increases, the cell nucleation density increases, and the cell size is reduced. Then, the use of TPUs with different characteristics allows controlling the cellular structure. Nanocellular polymers have been obtained with a core relative density between 0.15 and 0.20 and cell sizes between 220 and 640 nm.

Laboratory Evaluation of Sustainable PMA Binder Containing Styrene-Isoprene-Styrene (SIS) and Thermoplastic Polyurethane

In this study, thermoplastic polyurethane (TPU) and styrene-isoprene-styrene (SIS) were utilized to enhance asphalt binder properties. Superpave asphalt binder tests and multiple stress creep recovery (MSCR) were conducted to evaluate the physical and rheological performance (viscosity, rutting, and cracking properties) of the asphalt binders before and after short-term aging and after the long-term aging process. The results showed that (i) TPU has a positive effect on workability, including the mixing and compaction processes, which was evident from the reduced binder viscosity; (ii) asphalt binders with TPU and SIS showed better rutting resistance compared to the SIS binders without TPU; (iii) the cracking resistance of asphalt binders was found to be improved significantly with the addition of TPU; and (iv) TPU has the potential to be considered as a sustainable polymer modifier for producing bearable asphalt binders by improving rutting and crack resistance without increasing the melting temperature of the asphalt binders.

Thermoplastic polyurethane (TPU) modifier to develop bimodal cell structure in polypropylene/TPUmicrocellular foam in presence of supercriticalCO2

AbstractCurrently, the fabrication of microcell and bimodal cell structures (BCS) in polymer foams by using supercritical fluids has become a hot as well as a challenging research area worldwide. In this work, an environmentally friendly, effective, facile, and CO2‐based foaming technique was presented to fabricate microcellular polypropylene (PP) foams with BCS via blending with thermoplastic polyurethane (TPU). The toughness, thermal properties, rheological properties, and foamability of PP were systematically investigated with gradual incorporation of TPU. Representative sea‐island structure was observed in the scanning electron microscopy (SEM) images for the fracture surface of various PP/TPU samples. Rheological measurement results demonstrated that the viscoelasticity of various PP/TPU samples was improved remarkably compared with that of pure PP and pure TPU. The impact strength of various PP/TPU samples possessed the highest value as 12.4 kJ/m2with the TPU content of 15 wt%. After the addition of TPU, an ameliorative cellular morphology was observed in the SEM micrographs of various PP/TPU samples and their volume expansion ratio was enhanced significantly thanks to their improved melt elasticity. Moreover, it is worth noting that BCS appeared in various PP/TPU foams when the TPU content exceeded 5 wt%.

Study on morphology, mechanical, thermal and viscoelastic properties of PA6/TPU/CNT nanocomposites

ABSTRACT Thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were incorporated into polyamide 6 in an attempt to enhance notched impact resistance and damping performance. The morphology, mechanical, thermal and viscoelastic properties of different samples were studied. Scanning electron microscopy study indicated a uniform distribution of fine TPU droplets in PA6/TPU blend. Furthermore, well-dispersed CNTs in PA6/TPU matrix and good adhesion of polymer matrix to CNTs were observed. The addition of TPU into PA6 developed a rough fracture surface morphology and increased the notched impact strength equal to 39%, yet declined tensile and flexural resistance. The inclusion of CNTs into PA6/TPU improved mechanical properties comprising tensile, flexural and notched impact strengths as high as 14%, 12% and 16% respectively. The results of dynamic mechanical thermal analysis (DMTA) indicate: the addition of TPU into PA6 improves damping performance; the inclusion of carbon nanotubes in PA6/TPU enhances both energy storage and glass transition temperature.

Body Temperature-Triggered Shape-Memory Effect via Toughening Sustainable Poly(propylene carbonate) with Thermoplastic Polyurethane: toward Potential Application of Biomedical Stents

Shape-memory polymeric materials triggered by body temperature were fabricated via toughening sustainable poly(propylene carbonate) (PPC) with thermoplastic polyurethane (TPU). With an addition of TPU through melt blending, the ductility of PPC was dramatically enhanced, leading to the increase of shape recoverability but a deterioration of shape fixity. Remarkably, the blend containing 50 wt % TPU (PT50) presented the optimal shape-memory effect (SME) with balanced shape recovery and shape fixation performances because of the formation of the co-continuous structure promoting the synergy between PPC and TPU. Moreover, the PT50 sample exhibited significant improvement in not only the shape recovery ratio (∼95.0% recovery) but also the recovery speed and recovery stress, which enabled it to achieve an excellent SME when applied in practical use. After processed into a spiral-like stent, PT50 still showed a fast response to 37 °C, giving an efficient self-expansion within only 20 s. Besides, the blood and cell compatibility testing results revealed the good biocompatibility of PT50, further demonstrating the great potential of this material for development of biomedical stents.

Poly(lactic acid)/thermoplastic polyurethane/wood flour composites: evaluation of morphology, thermal, mechanical and biodegradation properties

This study was aimed at improving the toughness of poly(lactic acid) (PLA) without compromising its strength by developing a biodegradable composite based on PLA, Thermoplastic Polyurethane (TPU) and Wood flour (WF) particles. PLA/TPU/WF green composites with varying TPU content (0–50 wt%) were prepared on a twin screw extruder. The wood flour content was kept constant (10 wt%) for all the compositions. The addition of flexible TPU (10–50 wt% of total polymer composition) to the brittle PLA causes a significant increase in impact strength and elongation at break by ∼12.40 times and ∼3.57 times (for 50 wt% TPU content), respectively. Incorporation of WF filler brought improvement in tensile strength (∼1.47 times) and impact strength (∼871% enhancement over neat PLA) of the PLA/TPU blends with 50 wt% TPU content. Morphological analysis using SEM revealed that uniformly dispersed WF particles enhanced the interfacial interaction (H-bonding observed in FTIR spectra) between the TPU and PLA phase. Thermal analysis using DSC also shows that addition of TPU and WF depreciated the crystallinity of PLA because of enhanced interaction between the components which interferes with the crystallization of PLA. Finally, biodegradability studies (tested under soil) for 1 month demonstrated the significant degradability of PLA/TPU/WF composites in presence of WF particles. The potential applications of these bio-composites may range from automobiles, packaging to furniture industries.

Cellular morphology evolution in nanocellular poly (lactic acid)/thermoplastic polyurethane blending foams in the presence of supercritical N2

Currently, the formation of nanocells and complex cellular structure (CCS) in semi-crystalline polymer using supercritical fluids as blowing agent had become a big and newly developing challenge worldwide. In this paper, a facile methodology of polymer blending and batch foaming was proposed to fabricate CCS with large cells in micro-size and small cells in nano-size in semi-crystalline poly (lactic acid) (PLA) foams. Thermoplastic polyurethane (TPU) was introduced into PLA through melt mixing method to improve the viscoelasticity and foaming behaviors of PLA. Differential scanning calorimetry results showed that with the addition of TPU, the cold crystallization temperature of various PLA samples increased and their crystallinity kept unchanged almost. Compared with those of pure PLA, the complex viscosity, and storage modulus of PLA/TPU blends increased. Interestingly, with the increasing TPU content, the CCS appeared and became distinct in PLA/TPU blending foams as well as the thermal conductivity of various PLA foams decreased, respectively. The formation mechanism of CCS in nanocellular PLA/TPU blending foams was proposed and explained by schematic diagram. With the foaming temperature rising from 135 to 140 °C, a transition from nano-cells to micro-cells was also observed in PLA/TPU 5 blending foam, due to the decreased melt viscosity.

Hybrid Nanocomposites of Poly(Lactic Acid)/Thermoplastic Polyurethane with Nanosilica/Montmorillonite

The aim of this study is to improve the physical properties of poly(lactic acid) (PLA) by incorporating thermoplastic polyurethane (TPU), organo-montmorillonite (OMMT) and/or nanosilica (nSiO2). PLA was first melt mixed with five loadings of TPU (10–50 wt%) on a twin-screw extruder, followed by injection molding. The addition of TPU was found to increase the impact strength, elongation at break and thermal stability of the blends, but decrease the tensile strength and Young’s modulus. Based on a better combination of the mechanical properties, the 70/30 (w/w) PLA/TPU blend was selected for preparing both single and hybrid nanocomposites with a fix total nanofiller content of 5 parts per hundred of resin (phr), and the OMMT/nSiO2 weight ratios were 5/0, 2/3, 3/2 and 0/5 (phr/phr). The Young’s modulus and thermal stability of the nanocomposites were all higher than those of the neat 70/30 PLA/TPU blend, but at the expense of reducing the tensile strength, elongation at break and impact strength. However, all the nanocomposites exhibited higher impact strength and Young’s modulus than the neat PLA. Among the four nanocomposites, a single-filler nanocomposite containing 5 phr nSiO2 exhibited the highest impact strength and thermal stability, indicating that there was no synergistic effect of the two nanofillers on the investigated physical properties. However, the hybrid nanocomposite containing 2/3 (phr/phr) OMMT/nSiO2 possessed a compromise in the tensile properties.

Polyacetal/Acrylonitrile-Butadiene-Styrene/Thermoplastic Polyurethane Blends and Their Nanocomposites Morphological and Rheological Behavior as a Tertiary Blend

The effect of thermoplastic polyurethane (TPU) on morphological and rheological properties of polyacetal/acrylonitrile-butadiene-styrene (POM/ABS) blends has been investigated. The morphological investigations revealed that addition of TPU to the blends improves the dispersion of dispersed phase, regardless of the dominant phase. In the POM rich phase blend, this effect was more significant and morphology changed from non-uniform to droplet-matrix. The rheological studies showed that complex viscosity as well as elasticity, increased by adding TPU to the POM/ABS blends. This improvement in rheological properties was more significant in the POM rich phase blend, which was proved by positively deviating blends (PDB) in the complex viscosity curve in the entire range of frequency obtained from the log-additivity rule. Such a phenomenon could have occurred due to partial miscibility of TPU with POM and placement of TPU at the interface and/or in POM phase. Transmission electron microscopy (TEM) micrographs showed that addition of Cloisite 30B nanoclay into the blend creates both intercalated and tactoids morphology. X-ray powder diffraction (XRD) analysis also confirmed the presence of two different types of nanoclay dispersion. TEM results also demonstrated that nanoclay particles morphology was intercalated and was located in the ABS phase as well as phase interfaces.

Effect of toughening agents on the properties of poplar wood flour/poly (lactic acid) composites fabricated with Fused Deposition Modeling

This study was aimed at improving the toughness and interfacial properties of poplar wood flour/polylactic acid (PLA) composites by Fused Deposition Modeling. The effect of toughening agents was discussed. The results showed that, the addition of thermoplastic polyurethane (TPU) significantly increased the impact strength of composites by 51.31%.Comparing to other toughening agents, such as polycaprolactone (PCL) and poly (ethylene-co-octene) (POE), the compatibility between wood flour and PLA was superior when TPU was used. With the addition of TPU, the complex viscosity and the storage modulus of the composites were highly increased. The graft copolymers (GC), synthesized by free-radical melt grafting using glycidyl methacrylate as a graft monomer and dicumyl peroxide as an initiator, were used as compatibilizers in the composites. With the addition of 5 wt% wood flour loading, the grafting degree of GC was enhanced by 61.54%. At a 2 wt% loading of the GC, the impact strength and tensile strength of composites increased by 7.75% and 8.39%, respectively, and the interfacial adhesion of the ternary composites were improved.

Miscibility, Crystallization Behaviors and Toughening Mechanism of Poly(butylene terephthalate)/Thermoplastic Polyurethane Blends

Blends of poly(butylene terephthalate) (PBT)/thermoplastic polyurethane (TPU) were prepared by melt compounding. The miscibility, crystallization behaviors and toughening mechanism of the PBT/TPU blends were studied. Dynamic mechanical analysis results demonstrated that PBT was immiscible with TPU. Differential scanning calorimetry and wide angle X-ray diffraction results showed that the crystallinity of PBT decreased with increasing TPU content. Furthermore, blending with TPU did not modify the crystal structure of PBT. The small angle X-ray scattering results indicated that the crystal layer thickness decreased and the amorphous layer thickness increased with increasing TPU content, indicating that TPU mainly resided in the interlamellar region of PBT spherulites in the blends. An obvious improvement in toughness of PBT was achieved with addition of TPU. Neat PBT had elongation at break and impact strength of about 15 % and 2.9 kJ/m2, respectively. However, the elongation at break and impact strength of the 70/30 PBT/TPU blend reached 410 % and 62.9 kJ/m2, respectively. The morphology of the PBT/TPU blends after tensile and impact tests was investigated, and the corresponding toughening mechanism is discussed. It was found that the PBT showed obvious shear yielding in the blend during the tensile and impact tests, which induced dissipation of energy and, therefore, led to the improvement in toughness of the PBT/TPU blends.

Addition of thermo-plastic polyurethane (TPU) to poly(methyl methacrylate) (PMMA) to improve its impact strength and to change its scratch behavior

The effect of blending PMMA with TPU on both mechanical properties and scratch performance is studied. A higher TPU content leads to an enhanced impact strength and elongation at break but to a lower tensile strength and tensile modulus. PMMA tends to a brittle-ductile scratch behavior including cracks and material removal. Adding TPU changes the scratch behavior towards ductile ploughing without material removal. Fewer cracks occur within the scratch groove as the TPU content increases. The scratch walls show signs of ironing. However, the increasing TPU content also increases the opacity making it impossible to compare the scratch visibility of the blends to the neat material. There seems to be a good linear relation between the Charpy impact strength and the indentation depth of the PMMA/TPU blends. Similar to that, the Shore D hardness seems to linearly correlate to the indentation depth of the blends as well.

Preparation and characterization of polycarbonate/thermoplastic polyurethane blend membranes for wastewater filtration

The polycarbonate (PC)/thermoplastic polyurethane (TPU) blend membranes were prepared by phase inversion process applied to membrane bioreactor (MBR) to investigate the fouling characteristics. The impact of TPU and poly (vinylpyrrolidone) PVP concentration in polymer dopes on membrane structure, morphology, and performance were studied. The flat sheet fabricated membranes were characterized by scanning electron microscope (SEM), water contact angle (WCA), membrane surface roughness measurements and mechanical strength. The membrane performance was investigated at subcritical operating conditions. Pure water and critical flux through the fabricated membranes were measured for better understanding of the filtration and antifouling properties in MBR. The results showed that the membrane with polymer composition of 85/15 (PC/TPU) presented better performance in activated sludge throughout critical flux than that of other prepared membranes. Therefore, different dosages of PVP were introduced in this composition to study the effect of the additive in novel blend membranes. Likewise, the results indicated that TPU played the role of pore formation agent during the NIPS process, and the mean pore size of the membranes were increased with the increment in TPU content, which led to higher water flux. Finally, SEM images showed that the sponge-like structure formation was intensified by addition of TPU in casting solution. However, the finger-like structure was found to increase with introduction of 0.5wt.% PVP content into the casting solution. This study highlights the potential of PC membrane application in wastewater treatment with incorporation of TPU and PVP into PC membrane matrix.

Preparation, rheological properties and primary cytocompatibility of TPU/PLA blends as biomedical materials

A polymer blends containing thermoplastic polyurethane (TPU) and poly (lactic acid) (PLA) as a biomedical material were prepared by a process of modifying thermally induced phase separation (MTIPS) and melt blending. The influences of composition, shear frequency, and temperature on the rheological behaviors of the blends were investigated by small amplitude oscillatory shear rheology. The results revealed that the addition of TPU into PLA significantly decreased the non-Newtonian index of the blends, and increased the sensitivity of the blends on shear rate, suggesting that optimization of the shear rate and temperature could improve the flowability of the blend melts in the extrusion process. In addition, the results of SEM images revealed that TPU distributed well into PLA matrix and showed good compatibility between the TPU and PLA, which made the blends with good toughness. The primary cytocompatibility of the blends was evaluated using C2C12 cells. The results suggested that the TPU/PLA blends did not affect cell growth, showing no cytotoxicity. In short, the TPU/ PLA blends with excellent toughness had potential application as biomedical devices.

Study on the rheological, thermal and mechanical properties of thermoplastic polyurethane/poly (butylene terephthalate) blends

Thermoplastic polyurethane (TPU)/poly (butylene terephthalate) (PBT) blends with different ratios were prepared by extrusion and injection molding. The morphology, dynamic viscoelastic, capillary rheological, thermal and mechanical properties of the blends were studied. Results showed that there was good compatibility between TPU and PBT. The capillary rheological properties showed that the apparent viscosity decreased with the TPU content. DSC analysis indicated that with increasing TPU content the crystallization temperature (Tc), the melting point (Tm) and the percent crystallinity (Xc) decreased. Mechanical properties showed that the addition of TPU could lead to a remarkable increase, about 368.18%, in impact strength with a small reduction in tensile and flexural strength of TPU/PBT blends.

Reactive compatibilization of PLA/TPU blends with a diisocyanate

AbstractThis study focuses on the compatibilization of poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends by using 1,4 phenylene diisocyanate (PDI) for the first time, as the compatibilizer. Because of the potential interactions of diisocyanates with OH/COOH, they are useful for reactive processing of PLA/TPU blends in the melt processing. To have insight on the reactively compatibilized structure of PLA/TPU blends, phase morphologies are observed by means of scanning electron microscopy. The mechanical, thermal, and rheological responses of the blends are investigated. The observations are that the brittle behavior of PLA changes to ductile with the addition of TPUs. The addition of PDI improves the tensile properties of the blends. The compatibilization action of PDI is monitored with DMA and rheological experiments. Cross‐over in the G′ and G″ curves of compatibilized blends indicates the relaxation of branches formed in the presence of PDI. The dispersed phase size of TPU decreases in PLA in the presence of PDI due to the improved compatibility. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40251.