Morphology and mechanical properties of blends of thermoplastic polyurethane and polyolefins

Polyolefins (PO) were melt mixed with thermoplastic polyurethane (TPU) in a 20 : 80 weight ratio with or without compatibilizer containing 0.5 wt % of maleic anhydride. Effects of component viscosities on morphology and on mechanical properties of the blend were studied by scanning electron microscope (SEM), tensile property analysis, and dynamic mechanical analysis (DMA). It was found that the disperse particle size of compatibilizer‐free blends decreased with the decreasing viscosity ratio of the disperse phase to TPU. The efficiency of the compatibilizer in reducing the particle size varied with viscosity ratios of the disperse phase to compatibilizer. However, the particle size did not decrease with the decreasing viscosity ratio monotonically. With lower viscosity ratio, addition of 5 wt % compatibilizer resulted in a greater reduction of particle size and less loss in the tensile properties as compared to the TPU matrix. For the polyethene (PE) that has the lowest viscosity value among all the POs, its size in the blend was stabilized with the addition of compatibilizer and no compatibilization was detected by DMA and by tensile property analysis. The mobility of the disperse phase and compatibilizer and the dispersion competition between them seemed important. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 875–883, 2006     

Morphology control of polyoxy‐methylene/thermoplastic polyurethane blends by adjusting their viscosity ratio

Polyoxymethylene (POM) is an important plastic with very good properties. However, its poor impact strength limits its applications. Theoretical and experimental studies have confirmed that thermoplastic polyurethane (TPU) can effectively enhance the notched impact strength of POM. This paper reports that the notched impact strength of POM/TPU blends can be further improved when these blends are endowed with a fine morphology by changing the viscosity ratio of TPU to POM (P = η_TPU/η_POM) during processing. The experimental results show that the viscosity of TPU is more sensitive to temperature than that of POM, and that the viscosity ratio P decreases with increasing temperature; also for quite a wide range of shear rate, P is close to 1 when the processing temperature (T_p) is around 190 °C. Accordingly, the phase structure of POM/TPU blends changes with P. The dispersed phase of TPU shows ellipsoidal morphology when P > 1 at T_p < 190 °C, filamental morphology when P ≈ 1 at T_p ≈ 190 °C and spheroidal morphology when P < 1 at T_p > 190 °C. The results suggest that the filamental morphology endows POM/TPU (90/10) blends with the highest notched impact strength (～14 kJ m^?2). Copyright © 2006 Society of Chemical Industry     

Thermal and mechanical properties of polyisobutylene‐based thermoplastic polyurethanes

We investigated thermal and mechanical properties of thermoplastic polyurethanes (TPUs) with the soft segment comprising of both polyisobutylene (PIB) and poly(tetramethylene)oxide (PTMO) diols. Thermal analysis reveals that the hard segment in all the TPUs investigated is completely amorphous. Significant mixing between the hard and soft segments was also observed. By adjusting the ratio between the hard and soft segments, the mechanical properties of these TPUs were tuned over a wide range, which are comparable to conventional polyether‐based TPUs. Constant stress creep and cyclic stress hysteresis analysis suggested a strong dependence of permanent deformation on hard segment content. The melt viscosity correlation with shear rate and shear stress follows a typical non‐Newtonian behavior, showing decrease in shear viscosity with increase in shear rate. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 891‐897, 2013     

Mechanical properties of thermoplastic elastomeric blends of chitosan and natural rubber latex

Thermoplastic chitosan/natural rubber blends (Cs/NR) were prepared from natural rubber latex and chitosan by solution casting technique. The blends were characterized by mechanical analysis (stress–strain) and the mechanical properties were found to vary with chitosan/natural rubber ratios. Experimental values were compared with different theoretical models. Effect of thermal aging on mechanical properties was also investigated. Dicumyl peroxide was used as the crosslinking agent. The effect of crosslinking on mechanical properties of Cs/NR has also been studied. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Processing and properties of thermoplastic starch and its blends with sodium alginate

Viscosity measurements were carried out on corn starch (CS) and CS–sodium alginate (SA) suspensions at low levels of SA [1 to 10% (w/w)], as a function of temperature. The addition of SA caused the granular CS gelatinization process to occur at a lower onset temperature. CS and CS–SA mixtures were extruded in single‐ and twin‐screw extruders, with 15% glycerol and different water contents. Processing of plasticized CS–SA mixtures required lower temperatures, which is consistent with the viscosity results. Homogeneous and flexible extrudates were obtained by processing in a twin‐screw extruder. Samples in the composition range between 0 and 10% (w/w) SA were examined using tensile tests as a function of water content. Mechanical properties were dependent on the water content and on the SA composition. A significant increase in the Young's modulus value was observed for the blend containing 1% SA. Dynamic mechanical analysis was carried out for CS and CS–SA blends. Two transitions were detected in the temperature range –80 to 150°C. Scanning electron microscopy was used to examine the morphology of the extruded samples. The surfaces of the films were homogeneous, which demonstrated that the CS granules in all samples were characteristically destructured under the conditions used in processing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 412–420, 2001     

不同热塑性弹性体增韧聚甲醛

在比较乙烯-辛烯共聚热塑性弹性体(POE)、氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物(SEBS)和凝胶丁腈弹性体(GNBE)增韧聚甲醛(POM)的力学性能基础上,研究了GNBE增韧POM共混物的应力一应变、断裂形貌和热稳定性。结果表明,以GNBE改性POM共混物的力学性能最好。当以质量分数为6％的酚醛树脂为增容剂时,用质量分数为20％的GNBE增韧POM,共混物缺口冲击强度为21．6kJ／m^2,扯断伸长率为133．0％,拉伸强度为33．8MPa。当GNBE质量分数为10％时,POM／GNBE共混物应变为未改性POM的2倍。试样缺口冲击断裂形貌分析表明,POM的断裂表面光滑平整,是典型的脆性断裂;而POM／GNBE共混物的断裂表面粗糙。加入质量分数为20％,的GNBE,POM／GNBE共混物在空气气氛中的热失重温度有明显的提高。     

Improved dynamic properties of thermoplastic polyurethanes made from co-monomeric polyester polyol soft segments based on azelaic acid

Research and developmental work of bio-based materials from both renewable resources and biotechnological processes have gained significant interest recently. In this study, bio-based azelaic acid has been used in combination with succinic and adipic acids to synthesize co-monomeric polyester polyol soft segments for thermoplastic polyurethanes (TPUs). Hysteresis of TPUs made from co-monomeric polyester polyols were significantly lower in comparison to the reference TPUs made from monomeric polyester polyols, indicating significant improvement in dynamic properties. In addition, tensile sets of TPUs prepared with co-monomeric polyester polyols were lower compared to TPUs prepared from monomeric polyester polyols, confirming excellent dynamic properties. Improved dynamic properties of TPUs based on co-monomeric polyester polyols can be ascribed to a phase-separated morphology which was quantified as the lowest fraction of bonded urethane from FTIR spectra, reduced crystallinity in differential scanning calorimetry thermograms, narrow tan δ peaks measured using dynamic mechanical analyses, and images from atomic force microscopy.     

Study on mechanical,thermal and shape memory properties of polycarbonate/thermoplastic polyurethane blends

The objective of the study is preparation of shape memory blend of polycarbonate (PC) and thermoplastic polyurethane (TPU). Polycarbonate is blended with three types of TPUs and subsequently mechanical, thermal, morphological, and shape memory properties of the PC/TPU blends are studied. When TPU content in the blend is higher than 40% (by weight), the glass transition temperature related to PC is not shown in the differential scanning calorimetry thermogram, indicating loss of PC properties. The 60/40 optimized blend of PC/TPUs exhibits maximum increment of about 1100% in elongation and 43% decrement in tensile strength. The shape recovery of the optimized blend obtained by addition of 40% (by weight) of TPUs in PC polymer is found to be 65% and shape fixity is 97%. These results suggest that the blend of PC/TPU may be utilized for various applications where shape memory property is required including strategic applications.     

Synthesis and characterization of thermoplastic polyurethanes as binder for novel thermoplastic propellant

Two series of thermoplastic polyurethanes (TPUs), which used nitroester plasticiable tetrahydrofuran‐ethylene oxide random copolyether as soft segment and adduction products of isophorone diisocyanate (IPDI) and toluene diisocyanate (TDI) with 1,4‐butanediol as hard segments respectively, were successfully synthesized as binders for novel thermoplastic propellant. Mechanical tests and DSC techniques were applied to make characterizations of the polymers in order to choose candidate materials. Results shown that the TPU based on IPDI with fraction of the hard segment around 45% will meet requirements of propellant in terms of mechanical properties and glass transition of the soft segment phase. The results were further manifested in detail by quantitative studies of the degree of microphase separation as well as hydrogen bonding within the hard segment domain based on the equations established through FTIR and DSC analyses. It was found that mixing of two phases, which mainly referred to the mount of the hard segment dissolving into the soft segment phase, was as little as 10% in IPDI series TPUs, whereas it was almost up to 30% in TDI series. This indicated that better phase separation was achieved in IPDI series TPU. By contrast, studies of hydrogen bonding in domain revealed that the domain of TPUs prepared with TDI was much oriented in comparison with that with IPDI, which indicated higher processing temperatures. The results were raised by the melting index results under required conditions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2961–2966, 2002; DOI 10.1002/app.2324     

Blends of thermoplastic starch and polyesteramide: processing and properties

The blending of thermoplastic starch (TPS) with other biodegradable polyesters such as polyesteramide could be an interesting way to produce new biodegradable starch‐based materials. Different mixes of wheat starch and polyesteramide (BAK) were melt blended by extrusion. After pelletization, granules were injection molded to produce test specimens. A range of blends was studied with glycerol (plasticizer)/starch content ratios varying from 0.14 to 0.54. BAK concentrations were up to 40 wt %, TPS remaining as the major phase in the blend. Various properties were examined with mechanical, thermomechanical (dynamic mechanical thermal analyzer) and thermal (differential scanning calorimetry) analysis. Hydrophobicity was determined with contact angle measurements. Thanks to the knowledge of the properties of each polymeric system, we analyzed the blends' behavior by varying each component concentration. The material aging was also studied. We showed that structural changes occurred during several weeks after injection. We noticed a certain compatibility between both polymeric systems. The addition of BAK to TPS matrix allowed us to overcome the weaknesses of pure thermoplastic starch: low mechanical properties, high moisture sensitivity, and high shrinkage in injection, even at 10 wt % BAK. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1117–1128, 2000     

Morphology and properties of thermoplastic polyurethanes with dangling chains in ricinoleate-based soft segments

In our previous publication on the structure-property behavior of segmented polyurethanes based on castor oil [Petrovi? ZS, Xu Y, Zhang W. Polymer Preprints 2007;48(2):852-3.], the results showed that these materials which possessed a soft segment weight concentration (SSC) of 70% have both low tensile strength and elongation at break. This behavior is distinctly different from segmented polyurethanes of comparable soft segment content obtained from petrochemical polymeric diols that possess terminal hydroxyl groups. The poor elastic properties of these segmented polyurethanes were ascribed to the low molecular weight of the polymers as well as due to the presence of the six-carbon “dangling chain”, which may influence the morphology of the resulting segmented polyurethanes. To further understand this behavior, four segmented polyurethanes with the SSC of 70, 60, 50, and 40%, respectively, were synthesized from a polyricinoleate diol with an M_n of 2580, diphenylmethane diisocyanate (MDI) and butanediol. The objective of this work was to study the effect of SSC on the morphology of the resulting polyurethanes, and to correlate the morphology with the properties of these bio-based segmented polyurethanes. Polymers were characterized by GPC, viscometry and spectroscopic methods. Thermal and mechanical properties of the polymers indicated good microphase separation. Microphase morphology was also noted by SAXS and AFM. Finally, “spherulitic-like” superstructures were noted in the solution cast films that are believed to arise from the nucleation and crystallization of the hard segments.     

Bio‐plastics and elastomers from polylactic acid/thermoplastic polyurethane blends

Blends of two biocompatible polymers: thermoplastic polyester‐urethane (TPU) and polylactic acid (PLA) were studied. The effect of the blending ratio on blend morphology and properties was examined by running a series of blends from 10 to 80 wt % of PLA. Increasing TPU concentration in the blends lowered the glass transition and melting point of PLA indicating that the components were compatible and partially miscible. The blends with 10–40 wt % PLA are hard, reinforced elastomers, while those with 60–80 wt % PLA are tough plastics. Cocontinuous morphology was suggested in samples with 40 and 50 wt % PLA. Inversion points between 30 and 40 wt % PLA (from globular phase is dispersed in the matrix to a cocontinuous morphology) and between 50 and 60 wt % PLA (a transition from cocontinuous to TPU dispersed in the PLA matrix) were observed. Elastomers with higher PLA content and intermediate morphology displayed a combination of high tensile strength, hardness, relatively high elongation and modulus. New materials have potential applications in the medical field. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41104.     

New fluoro‐modified thermoplastic polyurethanes

New fluoro‐modified thermoplastic polyurethanes containing perfluoropolyether (PFPE) blocks were synthesized by the reaction of a fluorinated macrodiol with a hydrogenated prepolymer based on poly(tetramethylene glycol) and 4,4′‐methylene‐bis‐phenylisocyanate, followed by subsequent chain extension with 1,4‐n‐butanediol. This multistep bulk process opened the way for a new family of polymeric materials whose tensile properties appear to be excellent and unchanged in comparison with the corresponding unmodified hydrogenated polymers. Dynamic mechanical analysis and differential scanning calorimetry revealed peculiar characteristics. These polymers showed an unusual multiphase structure in which not only the hard and the hydrogenated soft segments were self‐organized, but also a second soft phase, constituted by the PFPE segments, was present. Moreover, an easier hard‐phase segregation and self‐organization were observed, as was evidenced by the higher melting temperatures of the semicrystalline phase. This unique characteristic combined with a selective enrichment of PFPE segments to the surface, as indicated by the unusually low coefficient of friction data and superior chemical resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2279–2294, 2003     

Film processability and properties of polycaprolactone/thermoplastic starch blends

In this work, the processing and properties of blown films prepared from thermoplastic corn starch (TPS) and polycaprolactone (PCL) were studied, in particular at high TPS content. The influence of processing parameters and material moisture content on the tensile properties was also studied. The results show that final film properties are mainly controlled by the draw ratio, blow‐up ratio and PCL concentration in the blends. The results also show that PCL/TPS films are less hydrophilic as PCL content increases. Finally, it was found that a very narrow processing window exists for this blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Mechanical and thermal properties of polyolefin thermoplastic elastomer blends

ABSTRACT

Polyolefin thermoplastic elastomers (POEs) are a class of thermoplastic elastomer (TPE) that can be easily processed. POEs have broad applications from automobiles to footwear and it is desirable to be able to alter the microstructure and properties. In this work, a systematic study of how blending and thermal processing of POEs affects mechanical and thermal properties is undertaken. Ethylene-octene copolymer POEs with different degrees of crystallinity are blended, compounded, and moulded and then slow cooled, quenched, or annealed. Differential scanning calorimetry (DSC) results show that the blends are immiscible and that quenching suppresses crystallinity while annealing thickens crystals. More crystals of the same thickness or thicker crystals of the same amount in the blends result in a higher modulus, lower elastic recovery, and more residual strain or permanent deformation after tensile testing. Microstructural control will allow for the optimal design of elastomeric materials with anticipated properties.     

Effects of aggregation structure on rheological properties of thermoplastic polyurethanes

The effects of the molecular aggregation structure on the rheological properties of thermoplastic polyurethane (TPU) were investigated. The TPU was composed of poly{(tetramethylene adipate)-co-(hexamethylene adipate)} glycol as the soft segments, 4,4′-diphenylmethane diisocyanate and 1,4-butanediol as the hard segments. The TPU sheets prepared by injection molding were annealed at various temperatures from 23 to 120 °C to vary the molecular aggregation structure. Glass transition temperature of the soft segment and melting points of the hard segment domains of the TPUs decreased and increased, respectively, with increasing annealing temperature. The results of DSC, solid-state NMR spectroscopy and dynamic viscoelastic measurements revealed that the degree of micro-phase separation of the TPUs becomes stronger with increasing annealing temperature due to the progress of formation of well-organized hard segment domains. The dynamic temperature sweep experiments for molten TPUs revealed that the temperature at critical gel point, which is defined as the temperature at which the dynamic storage modulus coincides with the loss storage modulus, in the cooling process increased with the progress of aggregation of the hard segments in the TPUs observed in the solid state. The uniaxial elongational viscosity measurements showed that TPUs exhibited an obvious strain hardening behavior with strain rate owing to residual hard segment domains at an operating temperature. It was revealed that the formation of well-organized hard segment domains had a profound effect on the rheological properties of TPUs, in particular on their elongational viscosity.     

热塑性聚氨酯弹性体与乙华平橡胶共混物的性能

将聚酯型和聚醚型聚氨酯弹性体(TPU385E,TPU8685)分别与不同乙酸乙烯酯含量的乙华平橡胶(EVM400,EVM700)进行共混,考察了原料种类、共混比对共混物力学性能和耐磨性的影响。结果表明,随着TPU用量的增加,EVM/TPU共混物的拉伸强度、邵尔A硬度、100%定伸应力和300%定伸应力均提高,扯断伸长率下降;随着EVM用量的增加,EVM/TPU共混物的拉伸强度、邵尔A硬度、100%定伸应力和300%定伸应力均降低,扯断伸长率增大;随着TPU用量的增加,EVM/TPU共混物的耐磨性提高;TPU8685/EVM400共混物具有最大的拉伸强度,TPU385E/EVM700共混物具有最大的扯断伸长率,TPU8685/EVM700共混物具有最好的耐磨性;当2种TPU与EVM400质量比都为50/50时,TPU385E/EVM400的耐磨性最差。     

Preparation and studying properties of polybutene‐1/thermoplastic starch blends

Starch as an inexpensive and renewable source has been used as a filler for environmental friendly plastics for about two decades. In this study, glycerol was used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/polybutene‐1(PB‐1) blend. PB‐1 was melt blended with TPS using a single screw extrusion process and molded using injection molding process to investigate the rheological and mechanical properties of these blends. Rheological properties were studied using a capillary rheometer, and the Bagley's correction was performed. Mechanical analysis (stress–strain curves) was performed using Testometric M350‐10 kN. The rheological properties showed that the melt viscosity of the blend is less than that of PB‐1, and the flow activation energy at a constant shear stress of the blend increases with increasing glycerol content in the blend. The mechanical experiments showed that both stress and strain at break of the blends are less than that of PB‐1, whereas the Young's modulus of the most blends is higher than that of PB‐1 which confirms the filling role of TPS in the blend. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Morphology and rheological properties of compatibilized low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch blends

Morphology and rheological properties of low‐density polyethylene/linear low‐density polyethylene/thermoplastic starch (LDPE/LLDPE/TPS) blends are experimentally investigated and theoretically analyzed using rheological models. Blending of LDPE/LLDPE (70/30 wt/wt) with 5–20 wt % of TPS and 3 wt % of PE‐grafted maleic anhydride (PE‐g‐MA) as a compatibilizer is performed in a twin‐screw extruder. Scanning electron micrographs show a fairly good dispersion of TPS in PE matrices in the presence of PE‐g‐MA. However, as the TPS content increases, the starch particle size increases. X‐ray diffraction patterns exhibit that with increase in TPS content, the intensity of the crystallization peaks slightly decreases and consequently crystal sizes of the blends decrease. The rheological analyses indicate that TPS can increase the elasticity and viscosity of the blends. With increasing the amount of TPS, starch particles interactions intensify and as a result the blend interface become weaker which are confirmed by relaxation time spectra and the prediction results of emulsion Palierne and Gramespacher‐Meissner models. It is demonstrated that there is a better agreement between experimental rheological data and Coran model than the emulsion models. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44719.     

From microstructure to mechanical properties of compatibilized polylactide/thermoplastic starch blends

Bio‐degradable polymer blends of polylactic acid/thermoplastic starch (PLA/TPS) were prepared via direct melt blending varying order of mixing of ingredients fed into the extruder. The effect of interface interactions between PLA and TPS in the presence of maleic anhydride (MA) compatibilizer on the microstructure and mechanical properties was then investigated. The prepared PLA/TPS blends were characterized by scanning electron microscopy, differential scanning calorimetry (DSC), tensile, and rheological measurements. Morphology of PLA/TPS shows that the introduction of MA into the polymer matrix increases the presence of TPS at the interface region. DSC results revealed the reduction of glass transition temperature of PLA with contributions from both TPS and MA. The crystallization temperature was decreased by the addition of MA leading to reduction of overall crystallization of PLA/TPS blend. The mechanical measurements show that increasing MA content up to 2 wt % enhances the modulus of PLA/TPS more than 45% compared to the corresponding blends free of MA compatibilizer. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44734.