Thermal and mechanical properties of thermoplastic polyurethane elastomers from different polymerization methods

Thermoplastic polyurethane elastomers (TPUs) based on 4,4′-methylene-diphenyl diisocyanate, poly(tetramethylene glycol), diamine-terminated aliphatic nylon oligomer, and 1,4-butanediol were synthesized by two different polymerization methods, i.e. one shot and prepolymer methods. The effects of the polymerization method on the thermal and mechanical properties of the TPUs have been studied. A broader distribution of hard segment lengths in TPUs prepared by the one shot method was observed from thermal and tensile property measurements, compared with those prepared by the prepolymer method. TPUs by the one shot method showed a higher T_m of the hard segments and better tensile properties when soft-hard segment interaction was relatively small. However, inferior tensile properties were observed when the soft-hard segment interaction was high; typically when nylon oligomer was used as a soft segment.     

Miscibility and physical properties of conducting poly(urea‐urethane) thermoplastic elastomers

A series of amine‐terminated polyaniline oligomer (OPA)‐based conducting poly(urea‐urethane) thermoplastic elastomers (PUUs) was synthesized by two‐stage solution polymerization and characterized by FTIR. Various percentages of OPA were introduced into PUUs as chain extenders to form hard segments of PUUs with urea‐linkages. Spectroscopic and differential scanning calorimetry, as well as dynamic mechanical analysis, were conducted to elucidate the interaction and degree of miscibility between hard and soft segments, which were related to the stress–strain properties of PUUs. The hydrogen bonding index (HBI) measured by FTIR was employed to show the degree of interchain hydrogen bonding. Copolymer films with higher OPA content exhibit higher HBI and the degree of miscibility is significantly improved. The resultant conducting copolymers have higher tensile strength, higher Young's modulus, and lower elongation at break, because of the long rigid structure of OPA and the increase in the number of hydrogen bonds among the copolymers blocks. Incorporating OPA in PUUs increases the mass of the residue at temperatures over 600°C, according to thermogravimetric analysis. The conductivity of PUUs is found to range from 0.83 S/cm for neat OPA to 6.11 × 10^?5 S/cm for PUUs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3803–3810, 2007     

Morphology and mechanical properties of ethylene‐vinyl acetate rubber/polyamide thermoplastic elastomers

High performance thermoplastic elastomers based on ethylene‐vinyl acetate rubber (EVM) and ternary polyamide copolymer (tPA) were prepared through a dynamic vulcanization process in the presence of dicumyl peroxide (DCP). The morphology, crystallization, and mechanical properties of the EVM/tPA blends were studied. A phase transition of EVM/tPA blend was observed at a weight ratio of 60/40. The presence of EVM increased the melting enthalpy at the high temperature of tPA, ascribing to the heterogeneous nucleating effect of EVM. The tensile strength of EVM/tPA (70/30) blends was increased up to 20.5 MPa as the DCP concentration increased to 3.5 phr, whereas the elongation at break of the blends kept decreasing as the DCP concentration increased. The addition of ethylene‐acrylic acid copolymer (EAA) or maleic anhydride‐grafted EVM (EVM‐g‐MAH) to the EVM/tPA blends both induced finer dispersion of the EVM particles in the tPA phase and improvement in the tensile strength and elongation at break of the blends, which were ascribed to the compatibilization of EAA or EVM‐g‐MAH. Finally, a high performance EVM/tPA (70/30) thermoplastic elastomer with Shore A hardness of 75, tensile strength of 24 MPa, elongation at break of 361%, and set at break of 20% was obtained by adding 5 wt % of EVM‐g‐MAH and 3.5 phr DCP. It has great potential in automotive and oil pipeline applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Influence of silane‐modified coconut shell powder on thermal and mechanical properties of thermoplastic elastomers

A silane coupling agent (glycidyloxypropyltrimethoxysilane, GPTMS) was used to modify coconut shell powder (CSP), and the influence of the modified coconut shell powder (G‐CSP) on the thermal and mechanical properties of thermoplastic elastomers (TPEs) was investigated. The thermal stabilities of the G‐CSP‐TPEs were studied using TGA; Young's modulus of the G‐CSP‐TPEs was studied by means of the spherical indentation test and the tensile test, and the tensile test was also used to characterize the tensile strength of the G‐CSP‐TPEs. The results revealed that the specific functional groups of GPTMS were efficiently grafted onto the CSP and that G‐CSP enhanced the thermal stability of the TPEs. Under 8% strain, Young's moduli of 0–7.5 wt% G‐CSP‐TPEs obtained by the spherical indentation test and tensile test were almost equal, while the modulus of 10–15 wt% G‐CSP‐TPEs measured by the latter test was greater than that of the former test. The tensile strength of G‐CSP‐TPEs increased up to a threshold limit (10 wt% G‐CSP), followed by a significant decrease. Micro‐images of the fractured surfaces obtained by SEM indicated that the addition of G‐CSP gradually filled the microvoids in the matrix and enhanced the tensile strength of the composite. As the G‐CSP mass percentage exceeded a threshold limit (>10 wt%), the particles started to agglomerate, resulting in weak interfacial adhesion and inferior mechanical properties. Hence, an optimal amount of reinforcing agent G‐CSP should be added to attain desirable thermal and mechanical properties. © 2020 Society of Chemical Industry     

Optical transparency,thermal resistance,intermolecular interaction,and mechanical properties of poly(styrene‐butadiene‐styrene) copolymer‐based thermoplastic elastomers

The optical transparency, thermal resistance, intermolecular interaction, and mechanical properties of poly(styrene‐block‐butadiene‐block‐styrene) (SBS), which were modified by blending with crystalline polypropylene (PP) or amorphous polystyrene (PS), were analyzed. The dynamic mechanical test indicated that the PP exhibited an intermolecular interaction with SBS and PS was compatible with SBS. The optical properties indicated that the direction of the light was changed due to the difference between the refractive indices of SBS and the added modifiers. Additionally, refraction and reflection occurred at the interface, reducing the transparency of SBS. The thermal resistance of SBS clearly improved upon modification by the addition of crystalline PP polymer. The thermal treatment increased the tensile strength and the elongation at breakage of modified SBS by reducing the internal stress, which was generated during the blending process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Rheology of co‐continuous phase in physical thermoplastic elastomers

Nowadays, chemical and physical thermoplastic elastomers have found many applications in different industries. Compatibilizer and co‐continuous composition are among the important factors which control the optimum properties of a number of physical blends. Morphology, mechanical and rheological properties of various blends of polystyrene (PS) and polybutadiene were investigated. The results show that the co‐continuous composition for these blends is located in‐between 24 and 35 wt% of PS. These blends show a negative deviation from the viscosity logarithmic additivity rule. This observation suggests an improvement in the interactions between the phases in co‐continuous composition. Rheological and mechanical properties were used in determination of the co‐continuous phase. Copyright © 2004 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     

Rheological and thermal properties of glycidyl azide polyol‐based energetic thermoplastic polyurethane elastomers

The purpose of this study was to investigate the effects of polyol on glycidyl azide polyol (GAP)‐based energetic thermoplastic polyurethane elastomers (ETPEs). Briefly, a series of GAP/polyol‐based ETPEs (GAP/polyol ETPEs) with different copolyol ratios and hard segment contents were synthesized using GAP‐diol with common polyol and 4,4‐methylenebis(phenylisocyanate)‐extended 1,5‐pentanediol as soft and hard segments, respectively, by solution polymerization in dimethylformamide. The three types of polyols used were poly(tetramethylene ether) glycol (PTMG), polycarbonate‐diol (PCL‐diol) and polycaprolactone‐diol (PCD‐diol). The synthesized GAP/polyol ETPEs were identified and characterized using Fourier transform infrared and ¹H NMR spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheometric mechanical spectrometry. For GAP/PCL ETPEs with lower hard segment content, DSC results showed that the GAP segment failed to interact with either the PCL segment or PCL melting. In addition, the results of DMA showed that the presence of PCL segments in ETPEs improved the storage modulus below the melting temperature of the PCL block. Further, the crystalline PCL segments were attributed to reinforcing the ETPEs in a manner similar to that of the hard domain. As the hard segment content increased in the GAP/polyol ETPEs, both GAP/PTMG ETPEs and GAP/PCL ETPEs exhibited microphase separation transitions, while rheological experiments demonstrated a sudden decrease in complex viscosity in neighboring microphase separation transitions. © 2012 Society of Chemical Industry     

Properties of thermoplastic composites based on wheat‐straw lignocellulosic fillers

Lignocellulosic fractions from wheat straw were used as natural fillers in composites of a polyolefin (a copolymer of polyethylene and polypropylene) and a biodegradable polyester [poly(butylene adipate‐co‐terephthalate)]. The mechanical properties of these injected composites were investigated with tensile and impact testing. A reinforcing effect of wheat‐straw residues was found for both types of composites. Compared with the polyester‐based composites, the polyolefin composites were more brittle. The addition of compatibilizing agents (γ‐methacryloxypropyltrimethoxysilane, maleic anhydride modified polypropylene, and stearic acid) did not improve the properties of the polyolefin composites. The surface properties were studied with contact‐angle measurements, and poor interfacial adhesion was found between the hydrophilic lignocellulosic filler and the hydrophobic polyolefin matrix. Thermal characterization revealed the formation of low intermolecular bonds between the polyester matrix and the lignocellulosic filler, in agreement with the surface tensions results and scanning electron microscopy observations. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 428–436, 2004     

Microstructure‐properties correlations in dynamically vulcanized nanocomposite thermoplastic elastomers based on PP/EPDM

Thermoplastic vulcanized (TPV) nanocomposites were prepared in a laboratory mixer using EPDM, polypropylene of different viscosities, maleic anhydride modified polypropylene, an organo‐clay, and a sulfur‐based curing system. Based on the obtained results from X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimeter, and mechanical properties, the microstructure of the prepared nanocomposites was found to be sensitive to the viscosity difference between the two phases and the clay content. X‐ray diffraction and TEM images of the TPV nanocomposites showed that clay was nearly exfoliated and randomly distributed into the polypropylene phase. The SEM photomicrographs of the dynamically vulcanized thermoplastic elastomer samples showed that the rubber particles were dispersed through the polypropylene in form of aggregates and their size increased with the introduction of clay. The nanoscale dimensions of the dispersed clay resulted in a significant improvement of the tensile modulus of the TPV nanocomposite samples, from 20 to 90% depending on clay content and the viscosity ratio of PP/EPDM. In the PP nanocomposites, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. Moreover, the oxygen permeability in the TPV nanocomposites was found to be lower than in unfilled but otherwise similar materials. POLYM. ENG. SCI., 47:207–217, 2007. © 2007 Society of Plastics Engineers.     

Dynamic mechanical properties of thermoplastic elastomers from polypropylene–natural rubber blend

The dynamic mechanical properties of thermoplastic elastomers from polypropylene natural rubber blends have been evaluated with special reference to the effect of blend ratio and extent of dynamic crosslinking of the elastomer phase. The effects of HAF black and silica fillers have also been studied. It has been found that increasing the proportion of elastomer phase reduced the storage modulus and increased the loss tangent values of the blends. The effect of dynamic crosslinking was found to be more prominent in blends containing higher proportion of elastomer phase. The improvement in storage modulus and decrease in loss tangent values were quite remarkable with increase in extent of crosslinking in these blends. The 70:30 NR:PP blend was found to exist as a two-phase system, both the components forming continuous phases of the blend.     

Morphology and mechanical properties of thermoplastic elastomers from nylon-nitrile rubber blends

Nylon-nitrile rubber blends having different plastic-rubber component ratios (100/0, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 0/100) were prepared by melt mixing technique in a Rheocord-90 at a temperature set at 180°C. The mixing characteristics of the blends have been analyzed from the rheographs. The morphology of the blend was studied using optical and electron microscopies, with special reference to the effect of blend ratio. The micrographs indicate a two-phase system where the component having lower proportions was found to disperse in the major continuous phase. A cocontinuous morphology was observed for 50/50 composition. Mechanical properties of the blends have been measured according to standard test methods. The effect of blend ratio on the mechanical properties like tensile strength, tear strength, elongation at break, stress-strain behavior, and hardness has been analyzed. The influence of the strain rate on the mechanical properties has also been analyzed. The mechanical properties were found to have a strong dependence on the amount of nylon in the blend. It is found that the blends with higher proportions of nylon have superior mechanical properties. The observed changes in mechanical properties are explained on the basis of the morphology of the blend. Various theoretical models such as Series, Parallel, Halpin-Tsai, and Coran's equations have been used to fit the experimental mechanical data. © 1996 John Wiley & Sons, Inc.     

Synthesis and properties of thermoplastic elastomers based on PTMO and tetra-amide

Segmented copolymers based on T6T6T-dimethyl (two-and-a-half repeating unit of nylon-6,T) and PTMO or extended PTMO₁₀₀₀/DMT that are thermoplastic elastomers were made via polycondensation. The materials have a good solvent resistance, are melt-processable and transparent. The polymers all have a low glass transition temperature (−60 to −0 °C). The rubbery plateau is wide and extremely flat and the melting temperature is sharp and high. The shear modulus of the rubbery plateau (3.3-14.5 MPa) and the flow temperature (183-220 °C) increase with increasing T6T6T content (5-16 wt%), corresponding to increasing crystallinity. The undercooling, as measured by DSC, is 20-30 °C. The compression set at room temperature is low (6-7%) and decreases slightly with decreasing T6T6T content. With AFM it was shown that the crystalline T6T6T units form long threads or ribbon like structures with a high aspect ratio in the amorphous PTMO matrix.     

The effects of hybrid fillers on thermal,mechanical, physical,and antimicrobial properties of ultrahigh‐molecular‐weight polyethylene‐reinforced composites

The effects of hybrid filler of zinc oxide and chitosan (chitosan–ZnO) on thermal, flexural, antimicrobial, chemical resistance, and hardness properties of ultrahigh‐molecular‐weight polyethylene (UHMWPE) composites with varying concentration of zinc oxide (ZnO) and further hybridized by chitosan (CS) were successfully studied. The composites were prepared using mechanical ball milling and followed by hot compression molding. The addition of ZnO to the UHMWPE matrix had lowered the melting temperature (T _m) of the composite but delayed its degradation temperature. Further investigation of dual filler incorporation was done by the addition of chitosan to the UHMWPE/ZnO composite and resulted in the reduction of UHMWPE crystallization. The flexural strength and modulus had a notably high improvement through ZnO addition up to 25 wt% as compared to neat UHMWPE. However, the addition of chitosan had resulted in lower flexural strength than that of 12 wt% ZnO UHMWPE composite but still higher than that of neat UHMWPE. It was experimentally proven that the incorporation of ZnO and chitosan particles within UHMWPE matrix had further enhanced the antimicrobial properties of neat UHMWPE. Chemical resistance was improved with higher ZnO content with a slight reduction of mass change after the incorporation of chitosan. The hardness value increased with ZnO addition but higher incorporation of chitosan had lowered the hardness value. These findings have significant implications for the commercial application of UHMWPE based products. It appears that these hybrid fillers (chitosan–ZnO)‐reinforced UHMWPE composites exhibit superior overall properties than that of conventional neat UHMWPE. POLYM. COMPOS., 38:1689–1697, 2017. © 2015 Society of Plastics Engineers     

Effect of fillers and plasticizers on the performance of novel heat and oil‐resistant thermoplastic elastomers from nylon‐6 and acrylate rubber blends

The effects of various fillers (SRF black, silica, and clay) and plasticizers (dibutyl phthalate and dioctyl phthalate) on the mechanical, dynamic mechanical, and rheological properties and on the heat and oil resistance of the thermoplastic elastomeric reactive blends of nylon‐6 and acrylate rubber (ACM) were investigated. The mixing torque behavior of the blends in Brabender Plasticorder shows reduced extent of interaction between the two component polymers in the presence of both fillers and plasticizers. Silica‐filled blends show the highest viscosity increment due to the possibility of reaction between its surface silanol groups and the reactive epoxy groups present in the ACM chain during melt‐blending operation. Though the addition of fillers reduces the processability of the blends, it improves the extensibility as well as the tension set properties of the blends. The mechanical integrity and the damping characteristics of the blends are also improved with the addition of fillers; the latter is evidenced from the dynamic mechanical thermal analysis of the blends. The tensile strength and hardness of the filled blends remain practically unchanged after ageing at 175°C for 72 h and, also, the oil swell does not change appreciably with the addition of fillers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1490–1501, 1999     

Isothermal decomposition behavior and dynamic mechanical properties of in situ‐reinforcing elastomer composites based on thermoplastic elastomers and thermotropic liquid crystalline polymer

In situ‐reinforcing composites based on two elastomer matrices very different in melt viscosity, styrene–(ethylene butylene)–styrene triblock copolymer (Kraton G1650), and styrene–(ethylene propylene) diblock copolymer (Kraton G1701), and a thermotropic liquid crystalline polymer (TLCP), Rodrun LC3000, were prepared using a twin‐screw extruder. The isothermal decomposition behavior and dynamic mechanical properties of the extruded strands were investigated by means of thermogravimetry (TG) and dynamic mechanical analysis (DMA), respectively. No significant change in the shape of TG curves for the neat matrices and their LC3000‐containing blends was observed under isothermal heating in nitrogen. In air, G1650 and G1701 showed a single weight‐loss stage and rapid decomposition whereas their blends with 30 wt % LC3000 showed different profiles of weight loss depending on isothermal temperatures. The calculated kinetic parameters indicated that the thermal stability of the polymers is much higher in nitrogen than in air and suggested an enhancement of thermal resistance of the elastomer matrices by addition of TLCP. DMA results showed a great enhancement in dynamic moduli for the blend with 10 wt % LC3000 when compared with the neat matrix. The tan δ peaks corresponding to the elastic and hard phases in both matrices mostly shifted to the lower temperature with LC3000 loading. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 917–927, 2007     

填料对丁羟型聚氨酯弹性体力学性能的影响

介绍了丁羟(端羟基聚丁二烯液体橡胶,HTPB)与2,4-甲苯二异氰酸酯(TDI)的固化反应机理,考查了当丁羟为100份,填料为85份时,不同填料对丁羟型聚氨酯弹性体力学性能的影响。     

动态硫化工艺对EPDM/PP相态结构及力学性能的影响

采用透射电镜(TEM)研究二次硫化的加工工艺对EPDM/PP热塑性弹性体相态结构及力学性能的影响,研究发现,与传统的一次硫化的加工工艺相比,采用二次硫化加工工艺制备的EPDM/PP弹性体,硫化橡胶能以颗粒态均匀分散于PP的连续相中,其力学性能也较一次硫化制备的样品有较大提高。     

Rheological properties of ionically and covalently crosslinked polypropylene‐type thermoplastic elastomers

Maleic anhydride was grafted onto a polypropylene‐type thermoplastic elastomer PER by reactive processing with a screw extruder, and a maleated PER (MPER) was prepared. Aiming at ionic crosslinking, magnesium 12‐hydroxy stearate (MgStOH), zinc oxide (ZnO), and zinc sulfide (ZnS), and aiming at covalent crosslinking, melamine as an amino compound, and Epocizer and GRYCI‐ALE as epoxy compounds, were added to the MPER, melt‐mixed by use of the screw extruder, and crosslinked compounds were obtained. The rheological properties such as capillary flow properties and dynamic viscoelasticities of the compounds were measured and their melt processabilities were evaluated. The degree of crosslinking was in the order of epoxy compounds > MgStOH > melamine > ZnO, ZnS > MPER (blank). In the case of the compound with MgStOH of a moderately high degree of crosslinking, the non‐Newtonian behavior is remarkable and the die swell ratio is low and suitable for extrusion. However, in the case of compounds with epoxy compounds of an excessive degree of crosslinking, fine extrudate cannot be obtained due to the lack of fusion and the control of degree of crosslinking is necessary. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 762–773, 2002     

Melt‐blowing thermoplastic polyurethane and polyether‐block‐amide elastomers: Effect of processing conditions and crystallization on web properties

Melt‐blown webs from ester and ether thermoplastic polyurethanes and polyether‐block‐amide (PEBA) elastomers were produced at different die‐to‐collector distances (DCD) to study the correlation between the polymer type and hardness, melt‐blowing process conditions, and web properties. An experimental set up was built to measure the air temperature and velocity profiles below and across the melt‐blowing die to correlate the fiber formation process and polymer crystallization behavior to process conditions and web properties. It was shown that air temperature and velocity profiles follow similar trends with increasing distance below the melt‐blowing die: both drop rapidly until reaching a plateau region approximately 5–6 cm below the die. Thereafter, they remain relatively constant with further increasing distance. It was found that crystallization onset and peak temperatures of all block copolymers in this study fall within this region of rapid velocity and temperature drop. This suggests that the polymers have already started to crystallize and solidify before reaching the collector, the extent of which depends on the crystallization kinetics of the polymer. The strong influence of the crystallization kinetics on web strength was clearly demonstrated in the PEBA series. In particular, the hardest grade produced the lowest web strength mainly because of its high crystallization rate and crystallization onset temperature. It is concluded that the melt‐blown web strength is strongly dependent on the degree of fiber‐to‐fiber adhesion within the web, which is determined by the amount of fiber solidification that occurs prior to the collector. The crystallization kinetics of the polymer and the distances traveled between the die and collector or the exposure time of the polymer melt to process and ambient air were shown to be critical in the amount of fiber solidification attained. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers