Polyurethanes(PU) were prepared using toluene diisocyanate,polypropylene glycol,ethylene glycol, dimethylolpropionic acid and triethylamine,and a siloxane modified PU(PSU) was obtained through reaction of the PU prepolymers with bis(3-(1-methoxy-2-hydroxypropoxy)propyl) terminated polysiloxanes(PMTS) of different molecular weight,specifically designed for this purpose.Results showed that,with increases in molecular weight of PMTS and its content,viscosity of the final PSU latexes decreased;phase separation of the incorporated PMTS in PSU films increased;the average particle sizes of the latexes varied between 110 nm and 330 nm,and the surface tension in the final latexes was relatively constant regardless of PMTS amount and its molecular weight.It was likely that copolymerized polysiloxanes had trend to enrich on top of the film when PMTS molecular weight was around 2000 and its content above 5 wt%.In general, PMTS modified polyurethane films showed higher performance than those from unmodified waterborne polyurethane latexes. 相似文献
This article describes synthesis of polyurethane (PU) elastomers based on DMC polyethers. The influence of the molecular weight of DMC polyethers on the strength characteristics and mechanical hysteresis of model PU composites based on them is studied. It is shown that, when the molecular weight of DMC polyethers changes in the range of 2000–4000, the strength of PU materials dramatically increases, while a considerable improvement of elastic properties is observed when using polyethers with MW = 8.000 or higher. 相似文献
Electrospun scaffolds based on polymer-matrix composites have gained wide attention recently. A novel engineered biocompatible scaffold is manufactured using polyurethane (PU) loaded with eucalyptus oil (EL) and Zinc nitrate (ZnNO3) using the electrospinning technique. Morphological observations revealed the reduced fibre diameter for the PU/EL and PU/EL/ZnNO3 compared to PU. Contact angle studies indicated the increase in hydrophobic behaviour of the PU/EL whereas an increase in wettability for PU/EL/ZnNO3 compared to PU. EL and ZnNO3 presence in the PU matrix enhanced the mechanical strength. Surface topology analysis showed a decrease in the roughness for the PU/EL and PU/EL/ZnNO3 compared to the pristine PU. Both PU/EL and PU/EL/ZnNO3 showed prolonged clotting time and decreased haemolytic percentage compared to the polyurethane as indicated in their anticoagulation studies. In vitro bone mineralisation testing depicted the increase in calcium deposition for the modified PU samples compared to pure polyurethane sample. Hence, PU/EL and PU/EL/ZnNO3 scaffold with superior properties render full avenues for new bone generation. 相似文献
Microstructure-dielectric properties relationship and molecular mobility of organic/inorganic polymer composites (OIPCs), consisting of polyurethane (PU) and sodium silicate (NaSi), were investigated in this work. Broadband dielectric relaxation spectroscopy (DRS) and thermally stimulated depolarization current (TSDC) techniques were employed. Our interest was focused on the study of the glass transition mechanism and conductivity relaxation. The influence of the molecular weight of PU and inorganic phase content on the dielectric properties of the composites was of particular interest. Glass transition temperature shifts to higher temperatures with the addition of NaSi. The overall molecular mobility was found to increase in the composites, compared to the pure PU matrix. The results are more intense for the composites based on the PU with low molecular weight. 相似文献
Summary: We report on a new route to synthesize polymeric carbon nanotube‐polyurethane (PU) nanocomposites. Multi‐walled carbon nanotubes (MWNTs) functionalized by chemical modification were incorporated as a crosslinker in prepolymer, which was prepared from a reaction of 4,4′‐methylene bis(phenylisocyanate) and poly(ε‐caprolactone)diol. The reinforcing effect of carbon nanotubes in crosslinked MWNT‐PU nanocomposites was more pronounced as compared to that in conventional MWNT‐PU nanocomposites. The optimum content of chemically modified MWNTs for crosslinking with polyurethane was determined to be approximately 4 wt.‐% in our samples, based on observation of a NCO peak in FT‐IR spectroscopy. MWNT‐crosslinked polyurethane containing 4 wt.‐% modified MWNTs showed the highest modulus and tensile strength among the composites and pure PU. The presence of functionalized MWNTs in the polymeric nanocomposite yielded enhancement in the thermal stability due to crosslinking of the MWNTs with PU.
Possible configuration for MWNT‐PU nanocomposite molecules and FT‐IR spectra of samples obtained during reaction of prepolymer with functionalized MWNTs (second step). 相似文献
This effort reports on novel polylactic acid-derived polyurethane (PU) and polyamide 6,12 (PA6,12)-based blends and graphene-reinforced nanocomposite. PU/PA6,12 (50:50) blend was opted as matrix based on molecular weight and shear stress performance. PU/PA6,12 with 5?wt% graphene (PU/PA6,12/graphene 3) showed improved T0 and Tmax of 515 and 541°C relative to neat blend. PU/PA6,12/graphene 3 also revealed significantly high tensile (53?MPa) and flexural strength (1,711?MPa). For Eschericia coli, Staphylococcus, and Pseudomonas bacterial strains, nanocomposite with higher graphene loading produced significant inhibitory effects. Novel nanocomposites displayed fine antimicrobial and barrier properties against O2 and H2O to be used as a packaging material. 相似文献
A new route to polyurethanes containing nucleic acid base derivatives as grafted pendants have been established. The method is based on the grafting of 2-(thymin-1-yl)propionic acid (TPA) or 2-(adenin-9-yl)propionic acid (APA) onto amino functionalized polyurethane, poly[2-amino-2-methyl-1,3-propylene methylene bis(4-phenyl carbamate)] (PU-NH2, IX ) at the primary amino group by the N-hydroxy compound of active ester technique. Two novel polymer models of polynucleic acid—poly[2-(2′-(thymin-1′-yl) propionamido)-2-methyl-1,3-propylene methylene bis(4-phenylcarbamate)] (PU–NHT, X ) and poly[2-(2′-(adenin-9′-yl)propionamido)-2-methyl-1,3-propylene methylene bis(4-phenylcarbamate)] (PU–NHA-40, XI )—were obtained. The amino functional polyurethane was prepared by the following three step reactions; (1) Selective N-protection of N-benzyloxycarbonyloxy-5-norbornene-2,3-dicarbonimide (CbzONB) with 2-amino-2-methyl-1,3-propanediol gave the N-protecting diol monomer 2-benzyloxycarbonylamino-2-methyl-1,3-propanediol (CbzAMP); (2) N-Protecting polurethane poly(2-benzyloxycarbonylamino-2-methyl-methyl-1,3) propylene methylene bis(4-phenylcarbamate) (PU–NHCbz, VIII ) was obtained by the polyaddition of 4,4′-diphenyl-methane diisocyanate (MDI) with CbzAMP. (3) Deprotection of PU–NHCbz produced amino polyurethane PU-NH2. Prior to polymer synthesis, the amidation of APA with 3-aminoheptane or diethylamine were carried out as a model reaction study and the related monomer model compounds were prepared by the same methods. 相似文献
Rigid polyurethane (PU) foams having saccharide and castor oil structures in the molecular chain were prepared by reaction between reactive alcoholic hydroxyl group and isocyanate. The apparent density of PU foams was in a range from 0.05 to 0.15 g cm?3. Thermal properties of the above polyurethane foams were studied by differential scanning calorimetry, thermogravimetry and thermal conductivity measurement. Glass transitions were observed in two steps. The low-temperature side glass transition was observed at around 220 K, regardless of castor oil content. This transition is attributed to the molecular motion of alkyl chain groups of castor oil. The high-temperature side glass transition observed in the temperature range from 350 to 390 K depends on the amount of molasses polyol content. The high-temperature side glass transition is attributed to the molecular motion of saccharides, such as sucrose, glucose, fructose as well as isocyanate phenyl rings, which act as rigid components. Thermal decomposition was observed in two steps at 570 and 620–670 K. Thermal conductivity was observed at around 0.032 J sec?1 m?1 K?1. Compression strength and modulus of PU foams were obtained by mechanical test. It was confirmed that the thermal and mechanical properties of PU foams could be controlled by changing the mixing ratio of castor oil and molasses for suitable practical applications. 相似文献
One kind of unknown structure sequence and composition ratio of thermoplastic polyurethane elastomers were characterized by nuclear magnetic resonance spectroscopy, Fourier transformed infrared spectroscopy, and gel permeation chromatography (GPC). The results showed that the polyurethane (PU) was obtained from poly(tetramethylene glycol) (PTMG) as soft segment, 1,4-butanediol (BDO) as chain extender, and 4,4′-methylenediphenyl diisocyanate (MDI) as hard segment. Furthermore, the composition ratio of MDI:PTMG:BDO was 2.07:1.22:1.00. At last, the molecular weight of PU was determined by GPC, and the number average molecular weight (Mn) and weight average molecular weight (Mw) are 63,300 and 133,800?g?mol?1, respectively. 相似文献
A novel waterborne polyurethane (PU), based on (-)-epigallocatechin-3-gallate (EGCG) that contains phenolic hydroxyl group, was successfully synthesized and characterized. The structural study of PU based on EGCG through FT-IR confirmed the incorporation of EGCG into the chain of PU. The results of X-ray diffraction (XRD) showed that the introduction of EGCG changed the crystallization behavior of the pure waterborne PU. Thermogravimetric analysis (TGA) results indicated that the PU samples exhibited improved thermal decomposition temperature. The degree of phase segregation of modified PU was confirmed by Scanning electron microscope (SEM) analysis. The physical and biodegradable properties of modified PU indicated a comprehensive performance. 相似文献