对苯二异氰酸酯基聚氨酯弹性体交联度对其形态与摩擦性能的影响

聚氨酯弹性体的摩擦性能在诸如船舶、汽车、生物医用等领域具有十分重要的意义,而通过化学修饰策略实现该类材料摩擦性能的精细设计,仍具有十分迫切的研究需求和广泛的应用前景。 本工作以对苯二异氰酸酯(PPDI)与聚四氢呋喃醚二醇(PTMG)为原料,通过调节1,4-丁二醇与三羟甲基丙烷两种扩链交联剂的混合比例,采用预聚体法合成了具备不同交联度的PPDI基聚氨酯弹性体。 其中,傅里叶变换衰减全反射光谱(FTIR-ATR)、广角X射线衍射(WAXD)、差示扫描量热仪(DSC)等表征结果表明,聚氨酯弹性体中硬段和软段的结晶度随交联度的提升均呈下降趋势。 同时,力学测试表明,材料的弹性模量随之降低,而PPDI基聚氨酯弹性体摩擦系数则明显增大。 此外,滞后回环曲线表明,交联度的改变影响了PPDI基聚氨酯弹性体的阻尼特性,而聚氨酯弹性体阻尼的差异在其摩擦性能对速率的依赖关系中则有所体现。 本工作由此提出,利用不同交联度下PPDI基聚氨酯中软硬段结晶度的变化,在对材料弹性模量和损耗模量进行可控调节的同时,能够实现对其摩擦性能的改变,为PPDI基聚氨酯弹性体的摩擦性能调控提供了一种简单有效的途径。     

Synthesis and Properties of High-Performance Thermoplastic Poly(ester-ether) Elastomers Reinforced by <Emphasis Type="Italic">N,N</Emphasis>′-Bis(2-carboxyethyl) Pyromellitimide Moieties

A series of poly(ester-imide-ether), consisting of soft segments from poly(tetramethylene glycol) and N,N′-bis(2-carboxyethyl) pyromellitimide and hard segments based on 1,4-butanediol and N,N′-bis(2-carboxyethyl) pyromellitimide, were synthesized via the melt polycondensation. The chemical structures of the prepared elastomers were confirmed by Fourier transform infrared spectroscopy and ¹HNMR, respectively. The results indicated that the introduction of aromatic bisimide groups endows the elastomers with excellent thermal stability and mechanical property, which increase with the increment of imide unit content in the prepared elastomers. Additionally, compared to the poly(ester-ether) elastomer, these poly(esterimide-ether) fibers displayed stronger tensile strength and better low-temperature elastic recovery property.     

The influence of the method of butadiene rubbers cross-linking on their thermal properties

The paper presents results of thermal properties measurements of cis-1,4-polybutadienes with different contents of cis-1,4 mers before and after their conventional cross-linking with the use of dicumyl peroxide and non-conventional cross-linking by means of iodoform. The measurements were carried out under the atmosphere of neutral gas using a micro-calorimeter, DSC and thermogravimetry, TG. The thermal curves have been interpreted from the point of view of phase transitions and chemical reactions of investigated elastomers.     

Effect of an anionic emulsifier on the structure of butadiene-nitrile elastomers

X-ray diffraction and TMA studies show that surfactant sodium alkyl sulfonate (C₁₅) forms one of its two LC structures (distinguished by the smallest layer periodicity) in butadiene-nitrile elastomers containing different amounts of acrylonitrile units. In this case, the surfactant serves as a structural plasticizer and facilitates a more complete selective segregation of microblocks of trans-1,4-butadiene units and, especially, of sequences of alternating trans-1,4-butadiene and acrylonitrile units.     

具有超支化结构的聚醚型脂肪族聚氨酯弹性体的合成与表征及力学性能研究

用聚四氢呋喃醚二醇、端羟基超支化聚酯(HB-20)、异佛尔酮二异氰酸酯和1,4-丁二醇,合成了含有超支化结构的聚醚型脂肪族聚氨酯(PU)弹性体.通过Flory-Rehner公式计算了体系的交联密度;用FT-IR、WAXD和DSC表征了超支化PU的氢键化程度和形态.实验结果表明,在PU弹性体中引入少量的HB-20,能提高氨基甲酸酯羰基的氢键化程度和软硬段间的微相分离程度,从而显著提高材料的拉伸强度.由于氢键化程度和交联密度双重效应的影响,含6 wt%HB-20的聚醚型PU与不含HB-20的PU相比拉伸强度提高了2倍多,达到37.9 MPa,断裂伸长率仍高达414%.     

Synthesis and performances of poly(butylene-succinate) with enhanced viscosity and crystallization rate via introducing a small amount of diacetylene groups

A cross-linkable comonomer containing a diacetylene group, named dimethyl 4,4'-(buta-1,3-diyne-1,4-diyl)dibenzoate (DA) was synthesized and copolymerized with dimethyl succinate and 1,4-butanediol to prepare a series of slightly cross-linked PBS copolyesters (PBDASx). The chemical structure, crystallization and rheological behaviours of PBDASx were well investigated. Compared to neat PBS, PBDASx showed the greatly increased crystallization rate because of the promoting nucleation of the cross-linking domains, and the XRD results indicated that it had no influence on crystallization structure of PBS. The rheological behaviours indicate that PBDASx possessed higher viscosity than neat PBS even at high shear rate and temperature. PBDAS0.3 exhibited better comprehensive properties than neat PBS, which will widen applications of PBS.     

Synthesis, characterization and mechanical properties of polyester-based aliphatic polyurethane elastomers containing hyperbranched polyester segments

Aliphatic polyester-based polyurethane (PU) elastomers with hyperbranched polyester segments were synthesized from polyester diol, hydroxyl-terminated hyperbranched polyester (HB-20), isophorone diisocyanate (PDI) and 1,4-butanediol. The crosslinking density of the PU elastomer was calculated by using Flory-Rehner equation. The degree of hydrogen bonding, the microstructure and the morphologies of these PU materials were characterized by means of FT-IR, WAXD and DSC, respectively. The experimental results showed that the PU elastomers containing small amount of HB-20 exhibited the enhanced hydrogen bonding and mechanical properties. As compared with the comparable PU specimen, the tensile strength of the polyester-based aliphatic PU containing 6 wt% HB-20 increased by 71.2 times, up to 36.1 MPa, and the elongation at break was still as high as 333.1%, resulting from the dual effects of the hydrogen bonding and the crosslinking density in the PU system.     

Characteristics of polyether urethanes with mixed soft segments,prepared by two- and three-step procedures

A three-step procedure for preparing polyurethanes with mixed polyether segments was suggested. It involves preparation of the “inverse” prepolymer by the reaction of one of oligodiisocyanates with 1,4-butanediol taken in a double excess, followed by the reaction with the other oligodiisocyanate. Polyurethanes with alternating poly(tetramethylene oxide) and poly(propylene oxide) soft segments were prepared by this procedure. Such materials surpass polyurethanes prepared from a mixture of oligodiisocyanates in the strength and softening point of the hard phase. In contrast to poly(tetramethylene oxide) urethane, elastomers with mixed polyether segments do not crystallize.     

Synthesis and Characterization of Polyurethanes Based on Oligo(ϵ-caprolactone) Prepared by Free-Metal Method

The oligoester diols were synthesized via ring-opening polymerization of ?-caprolactone in the presence of creatinine and diethylene glycol or 1,4-butanediol as initiator systems. Thus, obtained oligomers were successfully used in the synthesis of segmented polyurethanes. The oligoester diols (poly(?-caprolactone) and dihydroxy(polyethylene adipate)) were reacted with 4,4′-methylenebis(phenyl isocyanate) in the presence of 1,4-butanediol as the chain extender to obtain polyurethanes. The physical and mechanical properties of polyurethanes were determined. The structures of the oligoesters and polyurethanes were elucidated by means of NMR, IR and MALDI-TOF MS studies.     

Surface free energy of polyurethane coatings with improved hydrophobicity

The polarity of polyurethane coats was studied on the basis of the goniometric method for determination of wetting angle values, on the basis of calculated surface free energy (SFE) values by the van Oss-Good and Owens-Wendt methods, and on the basis of polarity measurements with the use of the (1)H NMR spectra. Test polyurethanes were synthesised in the reaction of methylene diphenyl 4,4'-diisocyanate (MDI) or 3-izocyanatomethyl -3,5,5- trimethylcyclohexyl isocyanate (IPDI) and polyoxyethylene glycols or polyesters poly(ε-caprolactone) diols and poly(ethyleneadipate) diol with different molecular weights, and some diols as chain extenders, in dioxane. The type of raw material was found to significantly affect the phase structure of the obtained polyurethane elastomers and to control physical interactions within those structures, thus influencing the SFE values. Fundamental reduction in the SFE value of a coating below 28?mJ/m(2) was achieved by the use of 2,2,3,3-tetrafluoro-1,4-butanediol as the urethane prepolymer chain extender.     

交联密度对脂肪族聚氨酯弹性体结构与性能的影响

采用异佛尔酮二异氰酸酯(IPDI)与聚醚二元醇、三羟甲基丙烷(TMP)和1,4-丁二醇反应制备了具有不同交联密度的脂肪族聚氨酯弹性体.研究结果表明,当聚氨酯弹性体的硬段含量为40 wt%时,随着TMP含量的增加,聚氨酯弹性体的交联密度线性增加.随着聚氨酯弹性体交联密度的提高,聚氨酯中硬段相的玻璃化转变温度由32℃降为2...     

Polydimethylsiloxane–polyurethane elastomers: Synthesis and properties of segmented copolymers and related zwitterionomers

A series of polyurethane block polymers based on hydroxybutyl-terminated polydimethyl-siloxane soft segments of molecular weight 2000 were synthesized. The hard segments consisted of 4,4′-methylenediphenylene diisocyanate (MDI) which was chain extended with either 1,4-butanediol (BD) or N-methyldiethanolamine (MDEA). The MDEA-extended materials were ionized by using 1,3-propane sultone. The weight fraction of hard segments was in the range 0.13–0.39. The morphology and properties of these polyurethane elastomers were studied by a variety of techniques. All of these short-segment block copolymers showed nearly complete phase separation. The zwitterionomer materials exhibited ionic aggregation within the hard domains. Hard-segment crystallinity or ionic aggregation did not affect the morphology. Hard-domain cohesion was found to be a more important factor than hard-domain volume fraction in determining the tensile and viscoelastic properties of these elastomers.     

Phase transition behavior of a poly(oxyethylene-b-butylene adipate) ionomer with shape memory properties

A series of biodegradable poly(oxyethylene-b-butylene adipate) ionomers (POBAi) were prepared by two-step in situ polymerization using adipic acid, 1,4-butanediol and mixed monomers of bis(poly(oxyethylene)) sulfonated dimethyl fumarate. The chemical composition of these POBAi was ascertained by ¹H NMR spectroscopy. The objective of this study was to investigate the shape memory effect of POBAi containing ionomer compared to non ionic POBA. It was observed that POBA5.0i showed a good shape memory effect than that of POBA 2.5 mol% or none of ionic group due to much physical cross-linking point by rich ionic group. Stress-induced phase transition was investigated during the shape deformation and recovery process using a wide-angle X-ray diffractometer (WAXD). The POBA crystal phase transition from β- to α-form was observed in all POBA samples by either thermal treatment or physical drawing. The α-form crystal did not recover to the initial β-form during the recovery process because the monoclinic α-form crystal is structurally more stable than the orthorhombic β-form crystal.     

1,5-萘二异氰酸酯与1,4-丁二醇基为基质的多嵌段聚氨酯弹性体的合成与性能

利用 1 ,5_萘二异氰酸酯 (NDI)和 1 ,4_丁二醇 (BDO)为均匀硬质分子单体 ,与不同软质分子单体 (聚醚、聚酯、聚硅氧烷 )缩合制备多嵌段聚氨酯弹性体 ,详细研究了硬嵌段相 (NDI)弹性体的结构与性能间的关系 ,发现随着硬嵌段相长度的增加 ,或者氨基甲酸酯中胺基与聚醚、聚酯、聚硅氧烷中软段氧原子间氢键的减弱 ,都导致微相分离程度的增加 ,造成聚合物熔点和熔化热的升高。硬嵌段相熔化的多峰行为是由于形成了NDI/BDO半微晶区 ,在退火时转变为更加有序的结晶微区 ,当温度高于 1 80℃时 ,由于氢键的断裂 ,NDI/BDO硬嵌段发生分解反应 ,该过程源于不很有序的硬嵌段半结晶微区。当温度高于 2 5 0℃时 ,发生快速的分解。在动态力学行为方面 ,NDI基聚醚弹性体比其它硅氧烷基的弹性体展示了更高的硬嵌段区的稳定性 ,同时 ,在使用温度范围内 ,也显示出最高的储能模量值 ,表明刚性对温度的依赖性 ,以及NDI/BDO硬嵌段中活性填料的显著影响     

多元醇对对苯二异氰酸酯基聚氨酯微孔弹性体的形态与性能影响

以对苯二异氰酸酯(PPDI)、1,4-丁二醇、水、聚四氢呋喃醚多元醇(PTMEG)和氢化端羟基丁二烯多元醇(HLBH)为原料,采用两步法制备出聚氨酯微孔弹性体样品。通过傅里叶变换衰减全反射红外光谱(FTIR-ATR)、动态机械分析(DMA)、差示扫描量热仪(DSC)、万能材料试验机等技术手段对样品的微相分离、耐低温性能、动态生热进行了系统表征。结果表明,两种多元醇结构对泡孔尺寸影响不大,微孔尺寸在100~300μm之间,其中以150μm尺寸左右的泡孔居多;HLBH制备的聚氨酯微孔弹性体硬段形成的氢键数量多于PTMEG制备的微孔弹性体,具有更好的微相分离;由于较好的微相分离结构,HLBH样品在-30~150℃具有很宽的模量平台区,而PTMEG样品受软段的低温结晶影响,在0℃以下模量急剧上升,HLBH样品低温下的刚度变化优于PTMEG样品;同时HLBH样品的滞后生热亦小于PTMEG样品,具有更好的动态疲劳性能。     

Poly(chloropropylmethyl-dimethylsiloxane)–polyurethane elastomers: Synthesis and properties of segmented copolymers and related zwitterionomers

A series of polyurethane block copolymers based on hydroxybutyl terminated poly(chloropropylmethyl-dimethylsiloxane) and poly(tetramethylene oxide) soft segments of molecular weights 2100 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′-methylenediphenylene diisocyanate (MDI) that was chain extended with either 1,4-butanediol (BD) or N-methyldiethanolamine (MDEA). The materials chain extended with MDEA were ionized using 1,3-propane sultone. The weight fraction of the hard segments was in the range 0.30–0.45. The effect of mixed soft segments, chain extenders, and zwitterionization on the extent of phase separation and physical properties was studied by utilizing differential scanning calorimetry and dynamic mechanical, stress-strain, and Fourier Transform Infrared spectroscopy experiments. All of these short segment block copolymers showed nearly complete phase separation. The zwitterionomer materials exhibited ionic aggregation within the hard domains. Although hard segment crystallinity or ionic aggregation did not affect the morphology, hard domain cohesion was important in determining the tensile and viscoelastic properties of these elastomers.     

Synthesis and properties of a monolithic gradient polymer material based on polyurethane structures and 1,4-butanediol as a chain extender

Conditions of preparing monolithic gradient polymeric materials based on aliphatic polyether Laprol 5003 (Voranol 4711), 2,4-tolylene diisocyanate, and 1,4-butanediol as a chain extender have been studied. The materials have been synthesized on a semiautomatic lab molding machine that makes it possible to control the feed rate of precursors; therefore, the chemical structure of the material may be changed in the desired direction. As a consequence, the elastic modulus of the material changes along the sample length from 19 to 410 MPa; that is, the gradual transition from a low-modulus plastic to a rigid rubber occurs. The introduction of 1,4-butanediol improves the viability of precursors and thus hampers the occurrence of premature gelation and creates wide possibilities for obtaining both monolithic and composite reinforced gradient polymeric materials.     

Thermal properties of diene elastomers

The paper presents the results of investigating the effect of the macromolecule chemical structure and the spatial network structure of butadiene (BR), butadiene-styrene (SBR) and butadiene-acrylonitrile (NBR) rubbers on their thermal properties. The rubbers were cross-linked by the conventional method by means of dicumyl peroxide or sulfur as well as by the non-conventional way using iodoform (CH₃I). The rubber and their vulcanizates were assessed by the derivatographic method (under air) and by means of differential scanning calorimetry (DSC) under inert gas. The thermal cross-linking degree of the polydienes and the efficiency of the cross-linking processes, dependent on both the chemical structure of elastomer macromolecules and their spatial network structure were determined. The cross-linking of elastomers with iodoform changes the thermal properties of polymers, significantly increasing their glass transition temperature during both sample heating and cooling, which results from the increase in mutual interaction of macromolecules connected with their modification with iodine compounds.     

反相毛细管整体柱的制备及其在多肽混合物分离中的应用

采用甲基丙烯酸月桂酯为基础功能单体,乙二醇二甲基丙烯酸酯为交联剂,正十二醇、1,4-丁二醇及二甲基亚砜为致孔剂,在内径为75 μm的石英毛细管内制备了具有良好机械性能及化学稳定性的反相毛细管整体柱。考察了致孔剂的种类、比例以及交联剂在单体混合物中的比例对柱压和分离效果的影响;以单体15%、交联剂15%、致孔剂70%(均为质量分数)作为优化配方,在70 ℃条件下反应24 h;并对所合成的毛细管整体柱进行了电镜表征,测试了流速、柱长与柱压的关系。结果表明,毛细管整体柱的通透性良好,可通过延长柱长的方法提高分离效果。将所制备的毛细管整体柱装于纳升级高效液相色谱仪上进行牛血清白蛋白及血浆样本的胰蛋白酶酶切液的分离,获得了比较理想的分离效果。     

Tensile strength of polyurethane and other elastomeric block copolymers

Processes that impart strength and toughness are discussed along with reinforcement by colloidal plastics to indicate that high strength, except under restricted test conditions, necessitates a dispersed phase. Thereafter the dependence of the nominal and true tensile strengths on the type, size, and concentration of polar segments in polyurethane elastomers is considered. Data are first examined on formulations devoid of plastic domains and then on those containing domain-forming segments that result from the reaction of toluene-2,4-diisocyanate (TDI) with either toluene-2,4-diamine or 4,4′-methylene-bis-(2-chloroaniline) and from the reaction of 4,4′-diphenyl methane diisocyanate (MDI) with 1,4-butanediol (BD). Segments from TDI and either diamine give plastic domains that are especially effective for augmenting strength over an extended temperature range. Segments from MDI and BD are comparatively ineffective, although the formulation studied exhibits high strength at and below room temperature owing to strain-induced crystallization. From data on various segmented and triblock elastomers, general conclusions are drawn regarding the dependence of strength on the characteristics of the domains and the matrix. For some six segmented and triblock elastomers, it is found that the true tensile strength is essentially independent of the weight fraction of domains provided it exceeds 0.20 or thereabouts.