Synthesis and characterization of polyurethane/epoxy interpenetrating network nanocomposites with organoclays

Summary Novel nanocomposites with varying contents of organophilic montmorillonite (oMMT) were prepared by intercalating oMMT to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP). The PU/EP networks and the oMMT modified PU/EP IPNs nanocomposites were studied with Fourier transform infrared spectrometry, scanning electronic microscopy, transmission electronic microscopy, wide-angle X-ray diffraction, water absorption and tensile test. The results show that oMMT and the IPNs of polyurethane and epoxy resin exhibit synergistic effect on the phase structure and morphology of the IPNs nanocomposites. The addition of oMMT to the PU/EP IPNs matrix provides two fold benefits to the properties of the IPNs nanocomposites. oMMT has not a distinct effect on chemical structure of PU/EP IPNs but promotes the compatibility and phase structure of the IPNs, and the forced compatibility of PU and EP in interpenetrating process improves the dispersion degree of oMMT. Both the mechanical properties and water resistance of the PU/EP IPNs nanocomposites are superior to those of the pure PU/EP IPNs.     

网络间的化学键效应对聚氨酯／乙烯基酯树脂IPN形态与力学性能的影响

本文通过环氧树脂（Ｅ—５１）与甲基丙烯酸合成了大分子链中含有羟基或羟基被封闭的乙烯基酯树脂（分别称为ＶＥＲＨ与ＶＥＲＡ），并用它们与聚氨酯（ＰＵ）合成了不同组成的ＰＵ／ＶＥＲ互穿网络（ＩＰＮ），用扫描电子显微镜考察了这些ＩＰＮ材料的形态，发现网络间的化学键对ＩＰＮ的形态有很大影响，它们抑制了两个网络间的分相以及ＰＵ硬段局部有序结构的形成。对这些材料的力学性能进行了测定，结果表明网络间的化学键能较大幅度地提高材料的力学性能。     

聚氨酯/环氧树脂互穿网络聚合物反应动力学

通过共混法制备了聚氨酯(PU)/环氧树脂(EP)互穿网络聚合物(IPN),采用示差扫描量热法(DSC)和动态机械分析(DMA)对IPN形成过程中的固化反应动力学及产物IPN的相容性进行了研究,结果表明,m(PU)/m(EP)=10∶6的IPN体系的反应级数为0.95,表观活化能为169.23 kJ/mol;PU/EP IPN只有1个玻璃化转变温度,相容性好。     

双酚-S环氧树脂/聚氨酯互穿网络的热性能

研究了双酚-S环氧树脂/聚氨酯(BPSER/PU)互穿网络的性能。实验表明,完全固化后的双酚-S环氧树脂的玻璃化温度比双酚-A环氧树脂在相同条件下高40～50℃。通过动态力学谱仪(TBA)研究了BPSER与PU的配比和玻璃化温度之间的关系,讨论了两相间的相容性。结果表明,随着BPSER用量的增加,体系的玻璃化温度升高。m(BPSER)/m(PU)=25/75是两组分均匀混合的最佳值,形成了反应型互穿聚合物网络。另外,用热重分析仪(TGA)研究了完全固化后的互穿聚合物网络的热分解行为,结果表明,BPSER的加入可提高PU的初始热分解温度。     

High performance epoxy resin nanocomposites containing both organic montmorillonite and castor oil-polyurethane

Summary Epoxy resin/polyurethane interpenetrating polymer network nanocomposites with various contents of organophilic montmorillonite (oM-EP/PU nanocomposites) were prepared by a sequential polymeric technique and an in situ intercalation method. X-ray diffraction(XRD), and transmission electronic microscopy(TEM) analysis showed that organophilic montmorillonite (oMMT) disperses uniformly in epoxy resin/polyurethane interpenetrating networks(IPNs), and the intercalated or exfoliated microstructures of oMMT are formed. Differential scanning calorimetry(DSC) test proved that oMMT promotes the compatibility of EP phase and PU phase, and glass transition temperature(T_g) of oM-EP/PU nanocomposites improves with increasing oMMT content. Mechanical properties tests and thermal gravity analysis (TGA) indicated that oMMT and the IPNs of EP and PU exhibit synergistic effect on improving mechanical and thermal properties of pure EP. The mechanism of toughing and reinforcing of oM-EP/PU nanocomposites was further discussed by scanning electronic microscope(SEM).     

Morphologies and Mechanical Properties of Polyurethane/Epoxy Resin Interpenetrating Network Composites Modified with Kaolin

Polyurethane/epoxy resin (PU/EP)/dimethyl sulfoxide modified kaolin (PU/EP/K-DMSO) interpenetrating network composites were prepared by in situ intercalation method. FT-IR showed that hydrogen bonding existed between kaolin and PU/EP matrix. The structure of composites was characterized by XRD, SEM and TEM. The result indicated that: K-DMSO by a nanometer size and homodisperse in the PU/EP matrix. The analysis of images obtained by polarizing microscope showed that bubble diameter has decreased with the K-DMSO added. Mechanical test results indicated that: the tensile and compression strength of the PU/EP/K-DMSO composites are superior to those of the PU/EP IPNs.     

Interpenetrating polymer networks of bismaleimide and polyether polyurethane–crosslinked epoxy

In this work, we prepared the interpenetrating polymer networks of bismaleimide and polyether-type polyurethane(polyoxypropylene)–crosslinked epoxy (BMI/PU(PPG)–EP IPNs) by employing the simultaneous bulk polymerization technique. The polyurethane (PU)–crosslinked epoxy was identified via infrared (IR) spectra analysis. Also investigated herein were the mechanical properties, including tensile strength, Izod impact strength, and fracture energy (G_IC) of the IPNs with various BMI contents in PU–crosslinked epoxy matrix. In addition, differential scanning calorimetry (DSC) analysis and the thermogravimetric analysis (TGA) were performed to examine the thermal properties of the BMI/PU(PPG)–EP IPNs. In addition, morphology and dynamic mechanical analysis (DMA) of the BMI/PU(PPG)–EP IPNs were also studied. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2635–2645, 1998     

Synthesis,characterization and properties of organoclay‐modified polyurethane/epoxy interpenetrating polymer network nanocomposites

organoclay‐modified polyurethane/epoxy interpenetrating network nanocomposites (oM‐PU/EP nanocomposites) were prepared by adding organophilic montmorillonite (oMMT) to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymerization technique. Wide‐angle X‐ray diffraction (WAXD) and transmission electronic microscopy (TEM) analysis showed that the interpenetrating process of PU and EP improved the exfoliation and dispersion degree of oMMT. The effects of the NCO/OH ratio (isocyanate index), the weight ratio of PU/EP and oMMT content on the phase structure and the mechanical properties of the oM‐PU/EP nanocomposites were studied by tensile testing and scanning electronic microscopy (SEM). Water absorption tests showed that the PU/EP interpenetrating networks and oMMT had synergistic effects on improvement in the water resistance of the oM‐PU/EP nanocomposites. Differential scanning calorimetry (DSC) analysis showed that PU was compatible with EP and that the glass transition temperature (T_g) of the oM‐PU/EP nanocomposites increased with the oMMT content up to 3 wt%, and then decreased with further increasing oMMT content. The thermal stability of these nanocomposites with various oMMT contents was studied by thermogravimetric analysis (TGA), and the mechanism of thermal stability improvement was discussed according to the experimental results. Copyright © 2005 Society of Chemical Industry     

Diffusion and sorption of benzene vapor through polybutadiene‐, polybutadiene/styrene‐, and polybutadiene/acrylonitrile‐based polyurethanes

A series of polyurethane (PU) films made from toluene diisocyanate (TDI), 1,4‐butanediol (BDO), and hydroxyl‐terminated polybutadiene (HTPB), hydroxyl terminated polybutadiene/styrene (HTBS), or hydroxyl terminated polybutadiene/acrylonitrile (HTBN) was synthesized by solution polymerization. The absorption of benzene vapor was found mainly in the soft phase. The equilibrium adsorption (M_∞) was reduced with increasing hard segment content for all the PUs. The values of M_∞ were in the sequence of HTBN‐PUs > HTBS‐PUs > HTPB‐PUs, which could be explained by the different interaction parameters between soft segments and benzene. The HTBN‐PU film showed the lowest degree of phase segregation and had more hard segments intermixed in the soft phase, restricting the movement of soft segments, and therefore resulted to non‐Fickian behavior, while the HTPB‐PU is antithetical. FTIR and atomic force microscopy were utilized to identify the hydrogen bonding behavior and morphology change of the PU films before and after the absorption of benzene vapor. The tensile strength of the HTBN‐PUs showed a greater decrease than that of HTBS‐PUs and HTPB‐PUs after absorbing benzene vapor. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2984–2991, 2004