Low‐temperature route to thermoplastic polyamide elastomers

Thermoplastic polyamide elastomers were obtained by polymerization of aminobenzoyl‐substituted telechelics derived from poly(tetrahydrofuran)‐diols (number‐average molecular weight: 1400 or 2000 g mol^?1) with several diacid dichlorides (terephthaloyl dichloride, 4,4′‐biphenyldicarbonyl dichloride, or 2,6‐naphthalenedicarbonyl dichloride) and chlorotrimethylsilane in N,N‐dimethylacetamide at 0–20 °C. The as‐prepared polymers had melting temperatures above 190 °C and exhibited elastic properties at room temperature, as evidenced by dynamic mechanical analysis and stress–strain measurements. The polymer with 2,6‐naphthalenedicarboxamide hard segments had the widest rubbery plateau within the series, the highest extension at break, and good recovery properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1449–1460, 2004     

Physical characterization of commercial polyolefinic thermoplastic elastomers

In this work, a systematic study of physical characterization on a series of commercial polyolefinic thermoplastic elastomers (TPEs), is reported. Formulations from different manufacturers, having a wide range of Shore hardness values (from A45 to D51), were examined using simple, inexpensive and standard laboratory methods. From this analysis, the TPE chemical composition and its relationship with hardness and tensile set—the key parameters that define the TPE performance in most of the applications—could be established.

It was found that the strategy followed by the manufacturers to design TPEs is very similar. The EPDMs used for the different formulations look similar in ethylene content and thermal properties. Therefore, the TPE bulk modulus (or hardness) is mainly controlled by the PP content. Nice elastomeric behavior was observed only in grades with a dominant proportion of EPDM, in agreement with the deformation mechanism generally accepted for this type of materials. Grades with higher hardness values—and a dominant proportion of PP—showed a mechanical response corresponding to a toughened thermoplastic, even when these grades are marketed by the producers as “thermoplastic elastomers”. Differently from conventional crosslinked elastomers, where hardness and ability to recover from highly deformed states can be simultaneously controlled by changing the degree of crosslinking, the results of this work indicate that it is very difficult to increase TPE hardness without sacrificing elastomeric properties.     

Cooperative self-assembling in statistical copolymers: a new approach to high-temperature thermoplastic elastomers

Based on previous work, where it was shown that 4-urazoylbenzoic acid (U4A) groups, which are attached statistically to polybutadiene, form ordered supramolecular arrays in the unpolar polymer matrix, the present work describes the synthesis of a new molecular building block capable of self-assembling in the unpolar polymer matrix. 5-Urazoylisophthalic acid (U35A) groups attached to 1,4-polybutadiene chains cause the formation of a thermoplastic elastomer of improved properties. The clusters of functional groups show an endothermic transition. The melting temperature increases for low levels of modification from 130°C up to 190°C. The mechanical properties (stress–strain and dynamic mechanical) reveal excellent rubbery characteristics and a rubbery plateau which is considerably flatter than those of technical grade thermoplastic elastomers. The IR data indicate that the U35A groups are tetrafunctional with respect to supramolecular self-assembling. Based on detailed knowledge of the structure of the self-assembled domains in U4A groups, a model is developed which describes the observed material properties qualitatively.     

Precision synthesis of sustainable thermoplastic elastomers from lysine‐derived monomers

Novel renewable thermoplastic elastomers were synthesized by sequential polymerization of lysine‐ and itaconic acid‐derived monomers. Ring‐opening polymerization of lysine‐based O‐carboxyanhydride monomer using diethylene glycol as an initiator gave well‐defined α,ω‐dihydroxy functionalized lysine‐derived polyesters. The M _n of these polyesters increased with the monomer conversion while retaining relatively narrow molecular weight distributions. Based on the successful controlled polymerization and esterification of α,ω‐dihydroxy with 2‐bromoisobutyryl bromide, the resultant Br‐PL‐Br macroinitiator was used for the atom transfer radical polymerization of N‐phenylitaconimide (PhII). Three poly(N‐phenylitaconimide)‐b‐polyester‐b‐poly(N‐phenylitaconimide) triblock copolymers were prepared containing 12 ? 25 mol% PPhII, as determined by ¹H NMR spectroscopy. The properties of the obtained triblock copolymer are evaluated as high‐performance and renewable thermoplastic elastomer materials. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 349–355     

Synthesis of transparent thermoplastic polyurethane elastomers

Thermoplastic polyurethanes were synthesized from poly(propylene glycol)‐block‐poly(ethylene glycol) polyols and hybrid hard segments that combined at least two different chain extenders. The combination of hard segments allowed for modification of elastomer performance and processing not achievable by any single hard segment. The combination of hard segments modulated hard‐segment energies that were directly related to elastomer performance. Special attention is paid to obtaining optically transparent elastomers with this technique. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 271–278, 2004     

线形低密度聚乙烯／废胶粉热塑弹性体动态硫化性能研究

利用动态硫化法制备了线形低密度聚乙烯(LLDPE)/废胶粉(GTR)热塑弹性体。重点研究了两种交联剂:硫和过氧化二异丙苯(DCP)对共混物性能的影响。加入一定量的苯乙烯-丁二烯-苯乙烯(SBS)共聚物作为增容剂。结果表明,经过DCP动态硫化后的共混物的力学性能比简单共混的共混物有明显的提高,而加入硫磺体系对共混物力学性能影响不大甚至有所下降。通过红外光谱、热分析(DSC)和扫描电镜(SEM)对共混物的热行为和表面形态研究表明,加入DCP交联剂使LLDPE、SBS和胶粉之间发生了交联反应,从而增加了胶粉颗粒与LLDPE间的界面相容性,使其热塑性弹性体的力学性能得以提高。     

Strain induced strengthening of soft thermoplastic polyurethanes under cyclic deformation

We investigate the cyclic mechanical behavior in uniaxial tension of three different commercial thermoplastic polyurethane elastomers (TPU) often considered as a sustainable replacement for common filled elastomers. All TPU have similar hard segment contents and linear moduli but sensibly different large strain properties as shown by X-ray analysis. Despite these differences, we found a stiffening effect after conditioning in step cyclic loading which greatly differs from the common softening (also referred as Mullins effect) observed in chemically crosslinked filled rubbers. We propose that this self-reinforcement is related to the fragmentation of hard domains, naturally present in TPU, in smaller but more numerous sub-units that may act as new physical crosslinking points. The proposed stiffening mechanism is not dissimilar to the strain-induced crystallization observed in stretched natural rubber, but it presents a persistent nature. In particular, it may cause a local reinforcement where an inhomogeneous strain field is present, as is the case of a crack propagating in cyclic fatigue, providing a potential explanation for the well-known toughness and wear resistance of TPU.     

EPDM/PP热塑性弹性体在循环应力下的老化行为研究

本文研究了动态硫化EPDM/PP热塑性弹性体的动态疲劳老化行为,考察了其力学性能的变化,并分析了产生力学性能下降的原因。实验结果表明,随着疲劳时间的延长、疲劳振幅的增大,材料的断裂强度降低,并认为疲劳过程中完全硫化的EPDM橡胶粒子和热塑性塑料PP界面处的分子链断裂、滑移导致了断裂强度的降低;紫外光的加入,加速了材料在疲劳过程的分子链断裂、滑移速率,使材料的断裂强度有更大程度的降低;在机械疲劳老化单独作用下,材料体系几乎没有发生氧化反应,而紫外光的加入,促使了机械疲劳老化过程中氧化反应的发生。     

Synthesis and characterization of thermoplastic elastomers with polyisobutylene and polyalloocimene blocks

This article presents the synthesis and characterization of diblock, triblock, and tetrablock copolymers of alloocimene (Allo), a terpene from renewable resources, and isobutylene (IB) using the recently reported two‐phase living carbocationic system. The addition of a second Allo increment to diblocks of Allo and IB yielded triblock and tetrablock structures. The block copolymers showed thermoplastic elastomeric (TPE) properties. It is demonstrated that the unusual behavior of diblocks exhibiting TPE properties is due to the strain‐induced crystallization of the polyisobutylene block. The polyalloocimene blocks can be cured, making this material a potential replacement of halobutyl rubber without halogen content. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1567–1574     

Morphological origins of temperature and rate dependent mechanical properties of model soft thermoplastic elastomers

Thermoplastic elastomers (TPEs) combine high elasticity with melt processability due to their structural features being based on physical associations rather than chemical crosslinking. Their mechanical properties are governed by the interplay of the different dynamics present in the system (i.e., hard block associations and soft block mobility) combined with their morphology. Irrespective of their exact chemical structure or type of association (crystals, hydrogen bonds, or glassy domains), many soft TPEs show a reduction in toughness at elevated temperatures. In this study, we investigate the high-temperature mechanical properties of a model series of industrially relevant TPEs via systematically varying composition and molecular weight. The results show an increase in temperature resistance and in large-strain stress response as chain length increases. We underline the key parameters that influence the mechanical behavior and explain the observed effect of molecular weight on both the temperature- and rate-dependent large-strain response. A physical network-based model is presented that can explain the experimental findings assuming an improved network connectivity and extended lifetime of the entangled segments with increasing molecular weight.     

Anti‐vibration and vibration isolator performance of poly(styrene‐butadiene‐ styrene)/ester‐type polyurethane thermoplastic elastomers

This investigation presents novel thermoplastic elastomers (TPEs) based on poly(styrene‐butadiene‐styrene) (SBS) and ester‐type polyurethane (TPU‐EX) materials were prepared with varying compositions. A series of investigations were conducted on the relationships between mechanical properties, dynamic mechanical properties, anti‐vibration and vibration isolator properties given, and the different compositions. The experimental results show incompatibilities between SBS and TPU‐EX. SBS mechanical properties, dynamic mechanical properties, anti‐vibration and vibration isolator properties are improved with an increase in the amount of TPU‐EX, suggesting that the blending of SBS with TPU‐EX was consistent with the compound rule. Based on the obtained results, the viscoelasticity of SBS materials, their capacity to isolate vibration, and their anti‐vibration performance can be adjusted by controlling the proportion of TPU‐EX. Copyright © 2009 John Wiley & Sons, Ltd.     

Difunctional initiator based on 1,3-diisopropenylbenzene. IV. Synthesis and modification of poly(alkyl methacrylate- b-styrene-b-butadiene- b-styrene-b-alkyl methacrylate (MSBSM)) thermoplastic elastomers

MSBSM five-block copolymers where B stands for butadiene, S for styrene, and M for either methyl methacrylate (MMA) or tert-butyl methacrylate (tBMA) have been synthesized by sequential anionic polymerization in an apolar solvent by using a difunctional anionic initiator derived from 1,3-diisopropenylbenzene. These block copolymers show improved mechanical properties and an extended service temperature compared to traditional SBS thermoplastic elastomers. Upon hydrolysis and further neutralization of the PolytBMA end-blocks, the upper glass transition temperature (T_g) of the five-block copolymers has been raised up to about 150°C. A further increase in this service temperature (up to ca. 160°C) has resulted from the blending of sPMMA-SBS-sPMMA five-block copolymers with isotactic poly(methacrylate) (iPMMA), due to the formation of a stereocomplex. The tensile properties of these modified five-block copolymers have remained essentially unchanged. © 1996 John Wiley & Sons, Inc.     

An NMR self-diffusion investigation of water/xylene/alkyl amine solutions

Extensions of the solution phases have been determined and the self-diffusion behaviour investigated in ternary systems containing water/xylene/primary alkyl amine, where the chain length of the amine varied between C₆ and C₁₀. The phase diagrams at 25°C are dominated by a solution phase and a rather large water/xylene miscibility gap which increases slightly in size with increasing chain length of the amine. A lamellar liquid crystalline phase was found in all binary amine/water systems at 25°C, except for hexylamine where the lamellar phase melts below this temperature. The self-diffusion coefficients of all components decrease in a similar way when water is added to a xylene/amine solution. The self-diffusion is rapid and of similar magnitude for all components, which shows that no well-defined inverse aggregates are formed. The data are discussed in terms of hydrogen bonding between the different species in the solution.     

Poly[glycidyl methacrylate(GMA)/methylmethacrylate(MMA)-b-butadiene(B)-b-GMA/MMA] reactive thermoplastic elastomers: Synthesis and characterization

New block copolymers of the ABA type, where B stands for polybutadiene (PBD) and A for polyglycidylmethacrylate(PGMA), poly(methylmethacrylate(MMA)-co-GMA) and PMMA-b-PGMA, respectively, have been successfully synthesized by using the diadduct of tert-butyllithium (tert-BuLi) to meta-diisopropenylbenzene (m-DIB) as a difunctional initiator. The PBD midblock has been synthesized in a cyclohexane/diethylether (100/6, v/v) mixture at room temperature, whereas the methacrylate outer blocks have been synthesized in a cyclohexane/diethylether/THF (100/6/150, v/v/v) mixture at −78°C. Block copolymers of a very narrow molecular weight distribution (1.10) have been analyzed by differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and tensile testing. These materials are phase separated and can exhibit tensile strength up to 22 MPa together with very high elongation at break (1500%). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 3507–3515, 1997     

Unique plastic and recovery behavior of nanofilled elastomers and thermoplastic elastomers (Payne and Mullins effects)

We have proposed recently that the mechanical properties of nano-filled elastomers are governed by the kinetics of rupture and re-birth of glassy bridges which link neighboring nanoparticles and allow for building large rigid clusters of finite life-times. The latter depend on parameters such as the temperature, the nanoparticle-matrix interaction, and the distance between neighboring fillers. Most importantly these life-times depend on the history of deformation of the samples. We show that this death and re-birth process allows for predicting unusual non-linear and plastic behavior for these systems. We study in particular the behavior after large deformation amplitude cycles. At some point we put the systems at rest under large deformation, and let the stress relax in this new deformed state. During this relaxation process the life-time of glassy bridges increases progressively, even for large deformation states. The systems thus acquire a new reference state, which corresponds to a plastic deformation. The stretching energy of the polymer strands of the rubbery matrix is larger than in the initial undeformed state, but this effect is compensated by a new configuration of glassy bridges, which are much stiffer. For plastic deformations of less than about 10%, the new system acquires mechanical properties around this new reference state which are very close to those of the initial system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1495–1508, 2010     

Synthesis of poly(vinyl ether)‐based,ABA triblock‐type thermoplastic elastomers with functionalized soft segments and their gas permeability

The ABA‐type triblock copolymers consisting of poly(2‐adamantyl vinyl ether) [poly(2‐AdVE)] as outer hard segments and poly(6‐acetoxyhexyl vinyl ether) [poly(AcHVE)], poly(6‐hydroxyhexyl vinyl ether) [poly(HHVE)], or poly(2‐(2‐methoxyethoxy)ethyl vinyl ether) [poly(MOEOVE)] as inner soft segments were synthesized by sequential living cationic polymerization. Despite the presence of polar functional groups such as ester, hydroxyl, and oxyethylene units in their soft segments, the block copolymers formed elastomeric films. The thermal and mechanical properties and morphology of the block copolymers showed that the two polymer segments of these triblock copolymers were segregated into microphase‐separated structure. Effect of the functional groups in the soft segments on gas permeability was investigated as one of the characteristics of the new functional thermoplastic elastomers composed solely of poly(vinyl ether) backbones. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1114–1124     

Use of maleic anhydride compatibilization to improve toughness and other properties of polylactide blended with thermoplastic elastomers

Polylactide (PLA) being a very brittle biopolymer could be toughened by blending with thermoplastic elastomers such as thermoplastic polyurethane elastomer (TPU) and thermoplastic polyester elastomer (TPE); unfortunately, these blends are immiscible forming round domains in the PLA matrix. Therefore, the purpose of this study was to investigate the effects of using maleic anhydride (MA) compatibilization on the toughness and other properties of PLA blended with TPU and TPE. MA grafting on the PLA backbone (PLA‐g‐MA) was prepared separately by reactive extrusion and added during melt blending of PLA/thermoplastic elastomers. IR spectroscopy revealed that MA graft might interact with the functional groups present in the hard segments of TPU and TPE domains via primary chemical reactions, so that higher level of compatibilization could be obtained. SEM studies indicated that PLA‐g‐MA compatibilization also decreased the size of elastomeric domains leading to higher level of surface area for more interfacial interactions. Toughness tests revealed that Charpy impact toughness and fracture toughness (K_IC and G_IC) of inherently brittle PLA increased enormously when the blends were compatibilized with PLA‐g‐MA. For instance, G_IC fracture toughness of PLA increased as much as 166%. It was also observed that PLA‐g‐MA compatibilization resulted in no detrimental effects on the other mechanical and thermal properties of PLA blends. Copyright © 2014 John Wiley & Sons, Ltd.     

Polyisobutylene-containing block polymers by sequential monomer addition. X. Synthesis of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) thermoplastic elastomers

Preparatory to triblock synthesis experiments, the cationic polymerization of α-methylstyrene (αMeSt) was investigated using the 2-chloro-2,4,4-trimethylpentane (TMPCI)/TiCl₄ initiating system in the presence of triethylamine (Et₃N) as electron donor (ED) and CH₃Cl/n-hexane mixed solvent in the ?80 to ?40°C range. Conversions are influenced by temperature, [TiCl₄], [Et₃N], and [αMeSt]. The polymerization of αMeSt is living at ?80°C: Both termination and chain transfer to monomer are frozen out, however, initiation is slow relative to propagation. Highly syndiotactic (>94%) Pα Mest was obtained. At?60deg;C initiator efficiency is ca. 100%, but termination becomes evident. Et₃N may act both as Ed and as proton scavenger. Novel poly(α-methystyrene-b-isobutylene-b-α-methylstyrene) (PαMeSt-PIB-PαMeSt) triblocks have been synthesized by adding αMeSt to biliving polyisobutylene carbocations (⊕PIB⊕) in the ?80 to ?40°C range. The effects of temperature, solvent polarity, and [Et₃N] on the block copolymerization have been investigated. At ?80°C, the rate of crossover from ⊕PIB⊕ to αMeSt is lower than that of propagation of PαMeSt⊕, so that the triblock is contaminated by PIB and PIB-b-PαMeSt. At ?60°C, crossover occurs preferentially. The rate of propagation relative to that of crossover is also reduced by lowering the solvent polarity and increasing the [Et₃N]. High crossover efficiency and blocking efficiency can be obtained under optimum blocking conditions. The triblocks are novel thermoplastic elastomers (TPEs). © 1994 John Wiley & Sons, Inc.     

Crystalline morphologies in segmented copolymers with hard segments of uniform length

The crystal morphological properties of segmented poly(ether ester aramide) elastomers with aromatic hard‐segment amide units of uniform length were studied. Four samples with hard‐segment fractions ranging from 3.4 to 9 wt % were studied by tapping atomic force microscopy (AFM). For one sample, both solution and melt‐processed surfaces were examined, and similar crystal morphologies were found. The semicrystalline morphologies of these polymers had some similarities to other low‐hard‐segment segmented elastomers. The very thin needlelike or ribbonlike crystallites at the surface had a high aspect ratio for all the samples. The main difference observed for the different compositions was a decrease in the surface area density of ribbons with a decrease in the hard‐segment fraction. One sample was chosen for in situ AFM studies during film extension. The details of the crystallite orientation and breakup were studied in increments up to 700% elongation (8× stretch ratio) and after relaxation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1783–1792, 2004     

Structure of the hard segments in trans,trans-diisocyanato dicyclohexylmethane based PU elastomers

A model for the structure of the hard segments and the hydrogen bonded network in the hard domains of segmented polyurethane elastomers with trans,trans-diisocyanato dicyclohexylmethane (tt-HMDI)/1,4-butanediol (BDO) based hard segments is proposed. The structure of the bis(methylurethane) oftt-HMDI (Me-ttHMDI-Me) has been determined by single crystal x-ray diffraction analysis and the conformation and packing of the polyurethane hard segments are constructed by connecting the successive Me-ttHMDI-Me units via –CH₂–CH₂– groups using the principle of isomorphic substitution. The conformation and hydrogen bonds of the monomer units are retained. The resulting polyurethane structure is highly crosslinked by a three-dimensional hydrogen bond network. The special packing principle may explain the high melting point as compared to the well-known structure of 4,4-diisocyanato diphenylmethane (MDI)-BDO hard segments and the differences in the material properties.