不同硬段含量聚天冬氨酸酯聚脲结构和性能研究

通过聚天冬氨酸酯、端氨基聚醚与脂肪族异氰酸酯六亚甲基二异氰酸酯三聚体/预聚物反应,合成了纯硬段聚脲和不同硬段含量的聚脲,并考察了硬段含量对聚脲的结构形态、动态力学性质和力学性质的影响。硬段含量为73%~50%的聚脲呈现微相分离的形态,随着硬段含量降低,软段和硬段相的混合程度提高,脲羰基的氢键化程度增加,NH基氢键键长增加,硬段玻璃化转变温度Tgh降低,软段玻璃化转变温度Tgs的变化幅度较小,微相分离程度降低。材料的拉伸强度、模量和硬度随着硬段增加而提高,弹性则随之降低。     

2,4-二氨基甲酸乙酯甲苯对聚氨酯弹性体微相分离的影响

合成了一种分子结构中含有氨基甲酸酯基的化合物——2,4-二氨基甲酸乙酯甲苯,并加至聚氨酯弹性体中,采用傅里叶变换红外光谱(FTIR)、差示扫描量热分析(DSC)以及扫描电镜(SEM)等表征手段研究了该化合物对聚氨酯弹性体微相分离结构的影响。结果表明:加入2,4-二氨基甲酸乙酯甲苯后,聚氨酯弹性体的各基团之间形成了更多的氢键,提高了软段的玻璃化转变温度;另外当2,4-二氨基甲酸乙酯甲苯的添加达到一定量时,会促使弹性体硬段聚集形成微区。     

二聚醇嵌段型聚氨酯与单萜相容性的分子动力学模拟

含有六元环结构的二聚醇嵌段型聚氨酯具有聚氨酯胶粘剂的优异性能,加入增粘树脂可以进一步提高其粘接性能。其中,2者的相容性是胶粘剂体系获得优异性能的关键问题。本文采用分子动力学模拟法研究了二聚醇嵌段型聚氨酯与单萜的相容性,结果表明,二聚醇嵌段型聚氨酯结构中软段与硬段存在着较为明显的相分离行为,在330K附近最易混合。设计了四种软硬段相对含量不同的二聚醇嵌段型聚氨酯的结构,模拟并分析了4种结构的二聚醇嵌段型聚氨酯与单萜的相容性。结果表明,随软段含量增加,二聚醇嵌段型聚氨酯与单萜相容性增加。根据模拟结果讨论了二聚醇嵌段型聚氨酯与单萜共混体系的Huggins-Flory相互作用参数与温度之间的关系,确定了在最优结构和温度下,体系能够良好互容。单萜的加入,提高了胶粘剂体系综合相容性。     

H_(12)MDI聚氨酯弹性体微相分离研究

以4,4′-二环己基甲烷二异氰酸酯(H12MDI)/1,4-丁二醇(BDO)为聚氨酯硬段,分别以聚四氢呋喃醚二醇(PTMEG)、聚己二酸丁二醇酯(PBA)为软段合成了硬段含量(质量分数,下同)为23%～50%的聚氨酯弹性体。借助IR、DSC等分析手段研究了其微相分离结构,并针对所制备弹性体进行力学性能表征。结果表明,硬段含量对H12MDI基弹性体的软段玻璃化温度影响很小;硬段含量的增加,PTMEG型PU的微相分离程度随之先降低后增加,而PBA型PU的微相分离程度则随之降低;以PBA为软段的H12MDI基弹性体在硬段含量为40%时力学性能达到最优。     

硬段对热塑性聚氨酯弹性体结构及性能的影响

以实验室自制聚己二酸乙二醇酯二醇PEA为软段,二苯基甲烷-4,4’二异氰酸酯(MDI)为硬段,分别采用乙二醇(EG、1,4-丁二醇)、BOD和1,6-己二醇、HG为扩链剂,经预聚体法合成了硬段不同的聚氨酯弹性体。研究了硬段结构和硬段含量对弹性体硬度及力学性能的影响。采用旋转流变仪研究了弹性体在降温条件下的非等温结晶过程。结果表明,当硬段含量相同时,BDO-TPU结晶性能最好,拉伸强度最大;HG-TPU断裂伸长率最好。在BDO-TPU体系中,随硬段含量增加,材料硬度和强度增加,伸长率减小;结晶起始温度逐渐增大,结晶性能增强。     

热塑性聚氨酯热熔胶的合成与性能研究

以己二酸系聚酯二醇为软段,二异氰酸酯与扩链剂生成的链段为硬段,制备了聚氨酯热熔胶;研究了软硬段组成、结构、相对分子质量、扩链剂、异氰酸酯指数等对聚氨酯热熔胶的力学性能、结晶性能、粘接性能及耐热性能的影响。     

粒料法合成聚氨酯分散体及性能的研究

以聚四氢呋喃二醇(PTMG)为软段,异氟尔酮二异氰酸酯(IPDI)和1,4-丁二醇(BDO)为硬段,二羟甲基丙酸(DMPA)为亲水单体,采用粒料法合成了聚氨酯离子聚合物粒料,制备了固含量为40%的聚氨酯分散体(PUD),研究了亲水含量和硬段含量对分散体性能及其胶膜性能的影响。PUD的ζ电位处于30~60 mV,黏度小于1100 mPa s。随着亲水含量增加,平均粒径减小,粒径分布变窄,黏度升高;硬段含量增加,平均粒径增大,粒径分布变宽,黏度降低。透射电镜显示,溶胶粒子呈大小不一的球形结构。PUD胶膜吸水率在3.15%~6.67%。力学性能测试表明硬段含量增加,断裂伸长率降低,拉伸强度增强。DMA测试显示胶膜出现相分离,有硬段和软段两个玻璃化转变温度。随着硬段含量增加,相分离程度提高,软段玻璃化温度降低,硬段玻璃化温度升高。     

聚氨酯弹性体耐热性能的改善

1 前言 聚氨酯弹性体(PUE)在工业上已得到广泛应用,但由于PUE的耐热性差,制约了它在高温环境、高动态环境中的应用。因此改善PUE的耐热性是PUE研究领域中十分重要的课题。2 PUE硬段结构与耐热性能的关系 PUE是嵌段共聚物,软段相是橡胶态,硬段相呈玻璃态或半结晶态,两相的不相溶性形成了二相结构,两相分离的越好,PUE的耐热性能越好,耐热性主要由硬段相结构     

自乳化型聚氨酯脲乳液的制备与表征

以聚氧化丙烯二元醇为软段，甲苯二异氰酸酯、二羟甲基丙酸、２—甲基—１，３—丙二醇、乙二胺和二乙烯三胺为硬段，通过不同的方法合成了一种新型的自乳化型聚氨酯脲乳液（ＡＰｕ）。并用红外光谱、示差扫描量热仪、万能拉伸机和溶胀性实验对乳液胶膜的性质进行了表征；同时测定了乳液的高温稳定性。结果表明，在硬段之间和软段与硬段之间同时存在着氢键作用，这促使软段相的Ｔｇ向高温移动。比较两种不同方法合成的ＡＰｕ，发现，二步法ＡＰｕ具有比较规整的硬段结构，离子基团分布比较均匀，乳液的稳定性和材料的力学性能较好，但耐水性较差。     

MDI异构体对聚氨酯弹性体微观结构和性能的影响

以聚氧化丙烯二醇(DL-2000)为软段,不同2,4′-异构体含量的二苯基甲烷二异氰酸酯(MDI)和1,4-丁二醇(BDO)为硬段,采用预聚法合成了不同异构体含量的MDI型聚氨酯弹性体。采用FT-IR、DSC和DMA等分析手段对其结构和性能进行了表征。结果表明,随着2,4′-MDI异构体含量的增加,硬段间的氢键结合化程度降低,硬段区聚集结晶的能力也不断下降,硬段趋于均匀分散在连续相软段区中,两相相容性增加,聚氨酯弹性体的T和tanδ大幅度提高。     

Thermoplastic polyurethane pressure sensitive adhesives made with mixtures of polypropylene glycols of different molecular weights

New more simple and easier strategy for synthesizing thermoplastic polyurethane pressure sensitive adhesives (TPU PSAs) has been proposed. Thus, the properties of the TPU PSAs were adjusted by fixing the NCO/OH ratio to 1.1 and varying the content of the hard segments by mixing high molecular weight and low molecular weight polyether polyols during TPU synthesis. The thermoplastic polyurethanes have been synthesized with methylene diisocyanate (MDI), 1,4 butanediol chain extender and different mixtures of two polypropylene glycols (PPGs) polyols with different molecular weights (450 and 2000 Da). TPUs with different hard segments content (12.5–38.7%) were synthesized and their pressure sensitive adhesive properties depended on their hard segments contents and degree of phase separation. In general, the TPU PSAs with higher hard segments content exhibited low probe tack and low loop tack regardless of the nature of the metallic and polymeric substrate. In contrast, the 180° peel strength depended noticeably on the nature of the polymeric substrate and on the hard segments content of the TPU. TPU PSAs with hard segments content lower than 20.9% were general purpose or removable PSAs and the ones with higher hard segments content were high shear PSAs.     

Microstructural organization of polydimethylsiloxane soft segment polyurethanes derived from a single macrodiol

Segmented polyurethane (PU) block copolymers were synthesized using 4,4′-methylenediphenyl diisocyanate and 1,4-butanediol as hard segments and oligomeric ethoxypropyl polydimethylsiloxane (PDMS) as the soft segments, with hard segment contents ranging from 26 to 52 wt%. The microphase separated morphology, phase transitions, and degrees of phase separation of these novel copolymers were investigated using a variety of experimental methods. Like similar copolymers with mixed ethoxypropyl PDMS/poly(hexamethylene oxide) soft segments, PU copolymers containing only ethoxypropyl PDMS soft segments were found to consist of three microphases: a PDMS matrix phase, hard domains, and a mixed phase containing ethoxypropyl end group segments and dissolved short hard segments. Analysis of unlike segment demixing using small-angle X-ray scattering demonstrates that degrees of phase separation increase significantly as copolymer hard segment content increases, in keeping with findings from Fourier transform infrared spectroscopy measurements.     

聚醚型聚氨酯弹性体的合成及其动态力学行为

采用两步合成法,以4,4′-二苯基甲烷二异氰酸酯(MDI)和1,4-丁二醇(BDO)为硬段,相对分子质量分别为1000、2000、4000的聚氧化丙烯二元醇(PPG)为软段,制备了一系列聚醚型聚氨酯(PUR)弹性体,研究了预聚体异氰酸酯指数R及软段相对分子质量对PUR动态力学性能的影响。结果表明,预聚体R值增大,即PUR的硬段含量增加,储能模量G′提高,软段相的玻璃化转变温度(Tg)升高,软硬相区的相容性增大;软段相对分子质量增加,PUR的G′下降,软段相的Tg降低,并出现硬段相的玻璃化转变,软硬相区的相分离程度增大。     

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.     

Block copolyesters of poly(pentamethylene 2,6‐naphthalenedicarboxylate) and poly(tetramethylene adipate)

Hydroxy‐terminated poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers were prepared by melt polycondensation of dimethyl 2,6‐naphthalenedicarboxylate with excess 1,5‐pentanediol followed by evacuating out some 1,5‐pentanediol. The molecular weight of the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers was controlled by the charge molar ratio of 1,5‐pentanediol to dimethyl 2,6‐naphthalenedicarboxylate and the amount of 1,5‐pentanediol removed under vacuum. The ¹H‐NMR spectra of the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomers indicate that the transesterification between dimethyl 2,6‐naphthalenedicarboxylate and 1,5‐pentanediol was almost complete. Block copolyesters with hard segments of poly(pentamethylene 2,6‐naphthalenedicarboxylate) and soft segments of poly(tetramethylene adipate) were prepared by coupling the poly(pentamethylene 2,6‐naphthalenedicarboxylate) oligomer and a poly(tetramethylene adipate) glycol with methylene‐4,4′‐diphenylene diisocyanate in solution. The block copolyesters were characterized by IR, ¹H‐NMR, DSC, and X‐ray diffraction. The hard segments in the block copolyesters display an amorphous state. However, the thermal transitions of soft segments in the block copolyesters are strongly dependent on the composition. When the content of the hard segments increases, the glass transition temperature of the soft segments increases. Thus, the amorphous parts of the soft segments would be partially miscible with the hard segments. When the content of the hard segments is very low, the soft segments of the block copolyesters exhibit high crystallinity. But, as the content of the hard segments is about 30 wt % or more, the soft segments of the block copolyesters become amorphous. This is described as the effect of the presence of the hard segments which are partially miscible with the soft segments. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3652–3659, 2002     

Segmental orientation of thermoplastic polyurethanes investigated by 1H double-quantum NMR. Correlation with thermodynamic and mechanical properties

The segmental orientation of a series of thermoplastic polyurethane (TPU) samples with different content in hard segments and different number average molecular weights of soft segments was investigated by ¹H double-quantum (DQ) NMR. The residual dipolar couplings of the hard segments were measured via the residual second van Vleck moments. A simple theoretical approach based on Rouse modes was developed to explain the orientation dependence of the hard segments on the number average molecular weight of the soft segments. The effective transverse relaxation rates of the hard segments were correlated to the ¹H residual dipolar couplings. Moreover, the correlation between the segmental orientation of the hard segments and the thermodynamic and mechanical properties of the TPU samples is investigated. The glass transition temperatures of the soft segments represent the relevant thermodynamic quantities. The mechanical parameters used for discussing the correlations are Young's modulus, yield stress, and rebound resilience angles from tensile testing and rebound resilience measurements.     

Morphology of polyurethane–isocyanurate elastomers

The dynamic viscoelastic properties and thermal transition behavior of reaction injection molding (RIM) and cast polyurethane—isocyanurate elastomers have been studied as a function of various segments (soft and hard urethane, and hard isocyanurate) content. RIM and cast elastomers were prepared at different concentrations of soft and hard urethane, and hard isocyanurate segments. RIM elastomers with the higher isocyanate index (lower hard urethane and greater isocyanurate segment content) displayed an unchanged T_g (glass transition temperature of soft segment) and increasing T_gh (glass transition temperature of hard segment) related to the hard urethane and isocyanurate segments. This is due to the phase separation between the soft and the hard segments. Cast elastomers synthesized from the higher amount of 1,4-butanediol (greater hard urethane and less hard isocyanurate segment content) showed an increasing T_gs, decreasing T_gh of hard urethane segments, and an unchanged T_gh of isocyanurate segments. This is related to the phase mixing between the soft and the hard urethane segments and the phase separation of hard isocyanurate and hard urethane segments.     

Influence of soft segment composition on phase-separated microstructure of polydimethylsiloxane-based segmented polyurethane copolymers

Segmented polyurethane block copolymers were synthesized using 4,4′-methylenediphenyl diisocyanate (MDI) and 1,4-butanediol (BDO) as hard segments and various soft segments derived from poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS)-based macrodiols and mixtures thereof. The microstructure and degrees of phase separation were characterized using a variety of experimental methods. Copolymers synthesized with the PDMS macrodiol and from PDMS/PHMO macrodiol mixtures were found to consist of three phases: a PDMS phase; hard domains; and a mixed phase of PHMO, PDMS ether end group segments and some dissolved hard segments. Two models were used to characterize the small-angle X-ray scattering from these copolymers: pseudo two-phase and core-shell models. Analysis using both methods demonstrates that as the PDMS content in the soft segment mixture increases, the greater the fraction of hard segments involved in hard domains than are dissolved in the mixed phase. Findings from analysis of the carbonyl region of FTIR spectra are also in agreement with greater hard/soft segment demixing in copolymers containing higher PDMS contents.     

Mechanical response of dibenzyl-based polyurethanes with diol chain extension

A systematic investigation was made of the effects of varying hard and soft segment chemistry, crosslinking and preparation procedures, on the mechanical response of melt-cast polyurethane elastomers. In particular, two hard segments were compared, based on the diisocyanates: 4,4′-methylene bis(phenyl isocyanate) (MDI) and 4,4′-dibenzyl diisocyanate (DBDI). Rotation around the central -CH₂-CH₂- bridge in DBDI allows alignment of aromatic rings and hence crystallization within the hard phase, which is not available with MDI in melt-cast polyurethanes. Thus, new polymers were achieved, with a controlled ordering of copolymer hard segment blocks on the macromolecular chain. Wide angle X-ray diffraction of the as-moulded polymers revealed the presence of crystallinity in some cases, in the DBDI-based PU materials. Mechanical tests included load-unload cycles at constant rate of extension, with measurement of hysteresis and strain recovery, and stress relaxation tests. The presence of DBDI hard segments instead of MDI led systematically to increases in: the input strain energy to a given elongation, hysteresis and residual strain under cyclic loading, and stress relaxation. The results were interpreted in terms of a physically-based constitutive model framework previously proposed. This revealed that the observed effects of varying hard segment could all be explained by the hard domains having a higher flow stress in the presence of DBDI relative to MDI, associated with increased hydrogen bonding in DBDI-based polymers, which is enhanced in some cases by hard segment crystallinity. Materials with mixed MDI and DBDI hard segments were found to give the optimum combination of high input strain energy, but minimum residual strain, compared to equivalent materials based on MDI or DBDI alone.     

硬段含量对水性聚氨酯软段结晶性能的影响

以异佛尔酮二异氰酸酯、六亚甲基二异氰酸酯、聚己二酸丁二醇酯为主要原料合成了水性聚氨酯(WPU),通过FT-IR、DSC、XRD、SEM表征手段,研究了硬段含量对软段结晶性及WPU粘结性能的影响。研究表明,随着硬段含量的增加,WPU分子链上氨基甲酸酯键之间的氢键化程度提高,软硬两相相混严重,WPU软段结晶熔融焓变小,熔融温度变低;结晶衍射峰变弱,软段结晶性变差;粘结性能测试表明,在硬段含量较低时,聚氨酯体现出良好的结晶性能,初粘性较好。