邻接交联型聚氨酯弹性体的制备和性能

以端羟基聚丁二烯-丙烯腈(HTBN)、甲苯二异氰酸酯(TDI)、扩链剂2,4/2,6-二氨基-3,5-二甲硫基甲苯(DMTDA)为原料,加入化学交联剂过氧化二异丙苯(DCP)和助交联剂N,N-间苯撑双马来酰亚胺(HAV-2)制备出不同硬段含量、不同交联密度的聚氨酯弹性体(PUE),研究了硬段含量、交联密度和温度对PUE结构与性能的影响。结果表明,当NCO质量分数为9%,HVA-2加入量为1.5%时,邻接交联型PUE综合力学性能最优。邻接交联型PUE的热稳定性得到明显提高。随着HVA-2的加入,损耗因子tanδ减小。     

Rheological investigation of microphase separation transition of polyurethane elastomer

A technique of linear viscoelasticity measurements coupling with temperature scanning was found effective in the detection of microphase separation transition (MST) and in the determination of MST temperature. The validity and accuracy of the technique were confirmed and reinforced by atomic force microscopy and differential scanning calorimetry (DSC). The technique was applied to a study of the MST of a series of 13 polyurethane (PU) elastomers based on mixed toluene diisocyanate (TDI), 1,4 butadiol, and poly(tetramethylene oxide) (PTMO) of two different molecular weights; the MST temperatures of the PU elastomer samples were measured. Although each of the 13 polymer samples had distinct hard segment content and used PTMO of different chain lengths, or mixed PTMO, the MST temperatures of the 13 samples formed a linear master curve when the MST temperature was plotted against the fraction of hard segment. The master curve indicated that the MST temperature is independent of the length and type of PTMO. It was also found that 2,4 TDI prevailing over its isomer 2,6 TDI played a dominant role in the MST of this series of PU elastomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2107–2112, 2007     

Phase structure and thermal stability of crosslinked polyurethane elastomers based on well‐defined prepolymers

Taking advantage of the DSC method, general procedures were presented for qualitative and quantitative evaluation of the phase separation degree and the crystalline phase content in polyurethane elastomers with well‐defined structures. Those elastomers were obtained not only in a typical one‐step method but also in the prepolymer method with the use of urethane oligomers with controlled molecular weight distribution (MWD). Prepolymers with well defined chain structures and narrow distributions of their molecular weights (MWD) M _w/M _n = 1.1–1.3 were produced in a multistage method, i.e., in step‐by‐step polyaddition of 2,4‐ and 2,6‐TDI with polyoxyethylenediols or with polycaprolactonediols of varied molecular weights. Isocyanate oligomers obtained at individual stages were then crosslinked with triethanolamine, whereas hydroxyl‐terminated oligomers were crosslinked with 4,4′,4″‐triphenylmethane triisocyanate (Desmodur RE). The obtained polyurethane elastomers were found to be characterized by the presence of five phases: soft phase consisted of flexible polyol‐type segments, crystalline phase made of soft segments, crystalline and amorphous hard phase made of hard segments, and intermediate phase, which was a composition of the soft and hard segments. The polyurethanes obtained out of prepolymers with defined MWD were characterized by better phase separation of the soft segments and increased structural order inside the hard phase as well as by better thermal stability than polyurethanes obtained from the typical one‐step method. The structural effects were also discussed on the thermal properties of the synthesized elastomers as analyzed by the TG and DTA methods. © 2007 Wiley Periodicals, Inc. J Appl PolymSci 104: 1464–1474, 2007     

Comparison of properties of thermoplastic polyurethane elastomers with two different soft segments

Two series of thermoplastic polyurethane elastomers [poly(propylene glycol) (PPG) based PP samples and poly(oxytetramethylene)glycol (PTMG) based PT samples] were synthesized from isophorone diisocyanate (IPDI)/1,4-butanediol (BD)/PPG and IPDI/BD/PTMG. The IPDI/BD based hard segments contents of polyurethane prepared in this study were 40–73 wt %. These polyurethane elastomers had a constant soft segment molecular weight (average M_n, 2000) but a variable hard segment block length (n, 3.5–17.5; average M_n, 1318–5544). Studies were made on the effects of the hard segment content on the dynamic mechanical thermal properties and elastic behaviors of polyurethane elastomers. These properties of PPG based PP and PTMG based PT samples were compared. As the hard segment contents of PP and PT samples increased, dynamic tensile modulus and α-type glass transition temperature (T_g) increased; however, the β-type T_g decreased. The permanent set (%) increased with increasing hard segment content and successive maximum elongation. The permanent set of the PT sample was lower than that of the PP sample at the same hard segment content. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1349–1355, 1998     

Segmented block copolymers of natural rubber and propylene glycol-toluene diisocyanate oligomers

Segmented block copolymers were synthesized from hydroxyl terminated liquid natural rubber (HTNR) and polyurethane oligomers based on 1,2-propylene glycol and toluene diisocyanate (TDI) by one-shot and two-shot processes in solution. They were completely phase segregated. Structural features were characterized by infrared and nuclear magnetic resonance spectroscopies. The two-phase morphology was deducted from thermal analysis and dynamic mechanical analysis (DMA). The soft segment glass transition temperature was about ?64°C and the hard segment glass transition was between 70°C and 100°C depending on the polyurethane content. The two-phase morphology was corroborated by a two-stage thermal decomposition of the products. The morphology consisted of a heterogeneous dispersion of beads in a continuous matrix. The large size and the nature of the beads suggest that they are independent of the block copolymer structure and are formed by the agglomeration of the polyurethane homopolymers, which remain unbonded to the rubber chains during chain extension. At lower hard segment contents the materials behaved like quasi-elastomers, and at higher hard segment contents, they were like tough plastics. At intermediate compositions they behaved as rigid elastomers. Variations in hardness and tear strength were consistent with this behavior.     

Thermoplastic polyurethanes with isosorbide chain extender

Isosorbide, a renewable diol derived from starch, was used alone or in combination with butane diol (BD) as the chain extender in two series of thermoplastic polyurethanes (TPU) with 50 and 70% polytetramethylene ether glycol (PTMEG) soft segment concentration (SSC), respectively. In the synthesized TPUs, the hard segment composition was systematically varied in both series following BD/isosorbide molar ratios of 100 : 0; 75 : 25; 50 : 50; 25 : 75, and 0 : 100 to examine in detail the effect of chain extenders on properties of segmented polyurethane elastomers with different morphologies. We found that polyurethanes with 50% SSC were hard elastomers with Shore D hardness of around 50, which is consistent with assumed co‐continuous morphology. Polymers with 70% SSC displayed lower Shore A hardness of 74–79 (Shore D around 25) as a result of globular hard domains dispersed in the soft matrix. Insertion of isosorbide increased rigidity, melting point and glass transition temperature of hard segments and tensile strength of elastomers with 50% SSC. These effects were weaker or non‐existent in 70% SSC series due to the short hard segments and low content of isosorbide. We also found that the thermal stability was lowered by increasing isosorbide content in both series. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42830.     

Preparation and properties of segmented thermoplastic polyurethane elastomers with two different soft segments

Thermoplastic polyurethane elastomers were prepared from 4,4‐diphenylmethane diisocyanate (MDI)/1,4‐butanediol (BD)/poly(propylene glycol) (PPG) and MDI/BD/poly(oxytetramethylene glycol) (PTMG). The MDI/BD‐based hard‐segment content of polyurethane prepared in this study was of 39–65 wt %. These polyurethane elastomers had a constant soft‐segment molecular weight (M_n , 2000), but a variable hard‐segment block length (n, 3.0–10.1; M_n , 1020–3434). The effects of the hard‐segment content on the thermal properties and elastic behavior were investigated. These properties of the PPG‐based MPP samples and the PTMG‐based MPT samples were compared. The polyurethane prepared in this study had a hard‐segment crystalline melting temperature in the range of 185.5–236.5°C. With increasing hard‐segment content, the dynamic storage modulus and glass transition temperature increased in both the MPP and MPT samples. The permanent set (%) increased with increasing hard‐segment content and successive maximum elongation. The permanent set (%) of the MPP samples was higher than that of MPT samples at the same hard‐segment content. The value of K (area of the hydrogen‐bonded carbonyl group/area of the free carbonyl group) increased with increasing hard‐segment content in both the MPP and MPT samples, and the K value of the MPT samples was higher than that of the MPP samples at the same hard‐segment content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 345–352, 1999     

Adherence of Liquid Crystalline TDI-Polyurethanes to Steel

Linear liquid crystalline polyurethane (LC-PU) were synthesized by the reaction of 2,4-toluene diisocyanate (TDI), 4,4'-bis-(6-hydroxyhexoxy)biphenyl (BHHBP), and poly(butylene adipate) (PBA). The BHHBP as mesogenic unit was incorporated into the hard segment formed by the reaction with the TDI. The hard segments are incompatible with the PBA soft segments. The mesomorphic behaviour is influenced by both the soft segment length and the hard segment concentration.

The adhesion of such polyurethanes used as primer in composites based on steel as substrate and alkyd melamine resin as coating is dependent on the polyurethane structure, the thickness of the polyurethane layer and its drying conditions. The highest wet adhesion stability is achieved by the hard-segment-type polyurethane composed of TDI and the mesogenic unity BHHBP. Partial substitution of BHHBP by 2,2-bis-(hydroxymethyl)propionic acid (BHMPA) in this LC polyurethane enhances the effectiveness of the primer.     

Morphology of water-blown flexible polyurethane foams

A series of four TDI–polypropylene oxide (PO) water-blown flexible polyurethane foams was produced in which the water content was varied from 2 to 5 pph at a constant isocyanate index of 110. A portion of each foam was thermally compression molded into a plaque. The morphology of both the foams and plaques was investigated using dynamic mechanical spectroscopy (DMS), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), scanning electron microscopy (SEM), swelling, wide angle X-ray scattering (WAXS), and small angle X-ray scattering (SAXS). A high degree of microphase separation occurs in these foams, and its degree is nearly independent of water (hard segment) content. In the foam with the lowest water content the morphology possesses many similarities to that of typical linear segmented urethane elastomers. Small hard segment domains are present with a correlation distance of about 7.0 nm. When the water content is increased a binodal distribution of hard segment material appears. There are the small hard segment domains typical of segmented urethane elastomers as well as larger “hard aggregates” greater than 100 nm in size. The larger domains are thought to be aggregates of rich polyurea that develop by precipitation during the foaming reaction. WAXS patterns of the foams suggest urea and possibly hard segment ordering that may be of a paracrystalline nature but certainly lacking in true 3-dimensional crystallinity.     

Thermal and mechanical properties of poly(esterurethane) modified by copolyamide segments of various molecular weight

Thermoplastic polyurethane elastomers (TPUs) from diol-terminated poly(ethylene adipate) (PEA), 1,4-butanediol (BD) and 4,4′-diphenylmethane-diisocyanate (MDI) were modified by copolymerizing with diamine-terminated nylon-6/6,6 copolyamide (CPA) oligomers. The effects of content and molecular weight of CPA segments on the thermal and mechanical properties of TPU were studied. PEA segments showed enhanced crystallization when some of the hard segments were replaced by CPA segments, showing weaker CPA–PEA interaction. The crystallinity of the hard segments was reduced, probably due to some interaction and phase mixing between hard and CPA segments. The modulus of TPU also decreased, more markedly with CPA segments of higher molecular weight.     

Novel quinoline-based polyurethane elastomers. The effect of the hard segment structure in properties enhancement

Polyurethane elastomers incorporating a quinoline moiety along their polymeric backbones and aliphatic, aromatic or heterocyclic crosslinkers have been synthesized and characterized. For this, NCO-terminated urethane oligomers were prepared from poly(butylene adipate) diol and methylene diphenyl diisocyanate and were subsequently chain extended with 2,4-quinolinediol and different crosslinkers. This study reports the influence of the different crosslinker chemical structures and the hard segment molar ratio on the thermal and dynamic mechanical thermal properties, as well as on the mechanical properties of these elastomers. The fluorescence spectra of polyurethane elastomers were determined at an excitation wavelength of 290 nm. The different chemical structures of the crosslinkers determine the hard segment cohesion and reduce the mobility of the soft phase, having an important effect on thermal stability and on the mechanical properties of the polyurethane films. Thus the incorporation of aromatic crosslinkers results in polyurethanes with lower elongation and stress at break. The highest mechanical properties were obtained for polyurethanes crosslinked with aliphatic crosslinkers.     

Structure,composition, and adhesion properties of thermoplastic polyurethane adhesives

The composition and hard segment content of 13 commercial thermoplastic polyurethane elastomers (TPUs) were obtained using 1H-nuclear magnetic resonance (¹H-NMR). The properties of the TPUs were studied using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), dynamic mechanical thermal analysis (DMTA), and contact angle measurements. Solventbased adhesives were prepared by dissolving the TPUs in 2-butanone. Films of the TPUs were obtained by solvent evaporation, and their properties were studied. Adhesion properties were determined from T-peel tests on solvent-wiped poly(vinyl chloride) (PVC)/polyurethane adhesive joints. The influence of the segmented structure on the properties of the TPUs was assessed. The increase in the hard segment content in TPUs favoured the incompatibility (i.e. reduced phase separation) between hard and soft domains. TPUs with a high hard segment content had a low crystallinity, a low wettability, and a high joint strength. The storage and loss moduli obtained using DMTA decreased as the hard segment content in the TPUs increased. Furthermore, the TPUs prepared using ε-polycaprolactone as the macroglycol had a slower crystallization rate than those prepared using the polyadipate of 1,4-butanediol or the polyadipate of 1,6-hexanediol. The increase in the length of the hydrocarbon chain of the macroglycol improved both the rheological and the thermal properties of the TPUs. Finally, TPUs prepared using MDI as the isocyanate showed a higher crystallinity and a higher degree of crosslinking than those prepared using TDI.     

Mechanical properties of organic–inorganic polyurethane elastomers. I. Al(OH)3–polyurethane composites based on PPG

Aluminum hydroxide was used as a reactive filler to elastomers prepared from poly(oxypropylene)glycol (PPG), 2,4-tolylene diisocyanate (TDI), and 1,4-butane diol (BD). Mechanical properties, dynamic mechanical properties, and thermal properties were measured. Morphologies were observed by use of X-ray diffraction and scanning electron micrographs. The model reaction of isocyanate and aluminum was also studied. It was found that aluminum hydroxide fillers can be used for cost reduction without any detrimental effects on mechanical properties. Scanning electron micrograph studies of freshly cut surfaces of the aluminum filled elastomers showed that aluminum hydroxide is highly compatible with the elastomer. © 1994 John Wiley & Sons, Inc.     

用二元胺扩链的聚丁二烯型聚氨酯弹性体的结构与性能

以端羟基聚丁二烯、4,4’-二苯甲烷二异氰酸酯和4,4’-亚甲基双(2-氯苯胺)为原料,制备了具有优良物理机械性能的聚丁二烯型聚氨酯弹性体,研究了其结构与性能的关系。结果表明,该弹性体是一种微相分离接近完全的体系,硬段含量增加时微相分离则更趋完全。硬相微区中的大量氢键,具有强烈的物理交联作用。物理交联密度比化学交联密度大得多,对弹性体的结构和性能起着主要作用。     

Microphase-separated structure and mechanical properties of norbornane diisocyanate-based polyurethanes

Norbornane diisocyanate (NBDI: 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane) is a new commercialized diisocyanate. NBDI-based polyurethane elastomers (PUEs) were prepared from poly(oxytetramethylene) glycol (PTMG), NBDI and 1,4-butanediol (BD) by a prepolymer method. Microphase-separated structure and mechanical properties of the NBDI-based PUEs were compared with general aliphatic and cycloaliphatic diisocyanate-based PUEs. The diisocyanates used were isophorone diisocyanate (IPDI), 4,4′-dicyclohexylmethane diisocyanate (HMDI) and 1,6-hexamethylene diisocyanate (HDI). Regular polyurethanes were also prepared as hard segment models from each isocyanate and BD to understand the feature of each hard segment chain. The HDI-based PUE showed the largest Young's modulus and tensile strength in the four PUEs due to the ability of crystallization of the hard segment component and the strongest microphase separation. HMDI has both properties of aliphatic and cycloaliphatic diisocyanates because of its high symmetrical chemical structure compared with NBDI and IPDI. On the other hand, the NBDI- and IPDI-based PUEs have an inclination to phase mixing, leading to decreased Young's modulus and tensile strength. The NBDI-based PUE exhibited better thermal properties at high temperatures due to stiff structure of NBDI.     

The effect of chain extenders structure on properties of new polyurethane elastomers

Two series of polyurethane elastomers were synthesized to investigate what effect does the incorporation of various new chain extenders have on the mechanical and thermal properties of polyurethane elastomers. The polyurethane soft segments were based on poly(ε-caprolactone) polyol. The hard segment was based on 1,6-hexamethylene diisocyanate in combination with 2,5-dimethyl-3-hexine-2,5-diol (DHD), hexaethylene glycol, glycerin, or castor oil. The results showed that the degradation rate and mechanical properties of the final products can be controlled through the structure of diol chain extenders or/and hard segment cross-linking present in the polyurethane elastomers. The DHD-based polyurethane displayed a relatively low glass transition temperature of −57 °C and a tensile strength of 11–14 MPa and elongation at break of 600–700%. These kinds of materials have potential application in many domains.     

低压变(LCS)特种聚氨酯微孔弹性体研制

分别以不同异氰酸酯、端羟基聚二甲基硅氧烷(HTPDMS)、聚四氢呋喃醚二醇(PTMG2000)和扩链剂等为原料,采用半预聚法工艺制备了有机硅链段改性的低压缩永久变形(LCS)聚氨酯微孔弹性体(MPU)。探讨了预聚物类型、扩链剂类型、HTPDMS添加量、R值、硬段含量等因素对MPU力学性能特别是30%压缩永久变形(70℃、22 h)的影响。结果表明,采用液化MDI为异氰酸酯组分、自制902为扩链剂、R值为1.05、硬段质量分数为22%、软段中HTPDMS质量分数为15%时,压缩永久变形为1.8%,满足LCS要求。     

助剂对丁羟聚氨酯弹性体力学性能的影响

通过单向拉伸试验、交联密度和凝胶分数测试等手段,研究了MAPO、TEBA、防老剂H对丁羟(HTPB)聚氨酯弹性体力学性能的影响。结果表明:在不含催化剂的条件下MAPO与TDI完全能够发生反应;由于MAPO和HTPB竞争与TDI反应,进入弹性体交联网络结构中,可能破坏了网络结构的完整性,从而影响了弹性体的单向拉伸性能;TEBA与TDI反应进入弹性体网络结构中,增加了网络链的柔顺性;防老剂H对丁羟弹性体力学性能的影响是扩链作用、改变HTPB的反应分数和增加物理交联点3种作用的综合结果。     

Segmented block copolymers of natural rubber and bisphenol A–toluene diisocyanate oligomers

Segmented block copolymers were synthesized from hydroxyl‐terminated liquid natural rubber and polyurethane oligomers based on Bisphenol A and toluene diisocyanate by one‐shot and two‐shot processes in solution. Structural features were characterized by infrared and nuclear magnetic resonance spectroscopic analysis. The spectra of the one‐shot materials were identical with those of the two‐shot materials, indicating their chemical identity. The soft segment T_g was well defined and almost invariant around −64°C, but the hard segment T_g varied from 75 to 105°C as the hard segment content increased from 30 to 60 wt %. Two relaxation temperatures were observed for each sample in dynamic mechanical analysis (DMA). These observations and the two‐stage thermal decomposition by random nucleation mechanism, as investigated in thermogravimetric analysis unambiguously confirmed complete phase segregation in these materials. The scanning electron microscopy and optical micrographs showed well‐defined domains dispersed in a matrix, indicating the two‐phase morphology. Systematic changes in hardness and tensile properties with hard segment content were also observed. The samples behaved like soft elastomers at lower hard segment content, toughened plastics at high hard segment content, and rigid elastomers at intermediate compositions. Variations in hardness and tear strength were consistent with this behavior. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 706–721, 1999     

硬质多孔聚氨酯脲抛光垫材料的制备及性能研究

采用浇注机浇注的方法制备了可作为抛光垫材料使用的硬质多孔聚氨酯脲弹性体,借助万能拉力机、DMA、DSC等手段对材料性能进行表征。实验结果表明:调整硬段含量在一定范围时,可获得不同性能、多种抛光需求的抛光垫;与2,4–TDI相比,2,6–TDI的增加有助于与MOCA形成规整的硬段结晶,阻尼峰向高温处移动,但由于产物是完全线性结构,材料的储能模量反而有所降低;KEL值(能量损耗因子)用于表征材料的抛光性能时,少量的交联有助于获得较好的抛光效果。