Phenolic hydroxyl‐terminated (HTPU) and aromatic amine‐terminated (ATPU) PU modifiers were prepared by reacting two different macroglycols (PTMG, polytetramethylene glycol, Mn = 2000, and PBA, Polybutylene adpate, Mn = 2000) with 4,4′‐diphenylmethane diisocyanate (MDI), then further coupling with two different coupling agents, bisphenol A or 4,4′‐diaminodiphenyl sulfone (DDS). These four types of PU prepolymers were used to modify the epoxy resin with 4,4′‐diamino‐diphenyl sulfone as a curing agent. From the experimental results, it was shown that the values of fracture energy, GIC, for PU‐modified epoxy were dependent on the macroglycols and the coupling agents. Scanning electron microscopy (SEM) revealed that the ether type (PTMG) of PU‐modified epoxy showed the presence of an aggregated separated phase, which varied between 0.5 μm and 4 μm in the ATPU (PTMG) and between 1 μm and 1.5 μm in HTPU (PTMG) modified system. On the contrary, the ester type (PBA) PU‐modified epoxy resin showed a homogeneous morphology and consequently a much smaller effect on toughening for its good compatibility with the epoxy network. In addition, it was found that the hydroxyl‐terminated bisphenol A as a coupling agent improved fracture toughness more than the amine‐terminated DDS because of effective molecular weight buildup by a chain extension reaction. The glass transition temperature (Tg) of modified epoxy resin as measured by dynamic mechanical analysis (DMA) was lower in PTMG‐based PU than in a PBA‐based PU series with the same weight of modifier.
SYNOPSISHydroxyl-, amine-, and anhydride-terminated polyurethane (PU) prepolymer which were synthesized from polyether (PTMG) diol, 4,4'-diphenylmethane diisocyanate (MDI), and a coupling agent bisphenol-A, 4,4'-diaminodiphenyl sulfone (DDS), or benzophenonetetracarboxylic dianhydride (BTDA) were used to modify the toughness of bisphenol-A diglycidyl ether epoxy resin (DGEBA) cured with 4,4-diaminodiphenyl sulfone. From the experimental results, it was shown that the modified resin displayed a significant improvement in fracture energy (GIc) and also in its interfacial shear strength with polyaramid fiber. It was more enhanced with increase of the PU modifier wt % content. The hydroxyl-terminated PU was found to be the most effective among those three prepolymers. In addition, the toughening mechanism was discussed based on the morphological and the dynamic mechanical behavior of the modified epoxy resin. Fractography of the specimen observed by transmission (TEM) and scanning electron microscopy (SEM) revealed that the modified resin had a two-phase structure. The existence of an unclean fiber surface after its fiber pullout test suggested that a ductile fracture might have occurred. 0 1995 John Wiley & Sons, Inc.
ABSTRACT:The elastomers of polyvinyl alcohol gel were made from the polyvinyl alcohol polymer, with boric acid added as a crosslinking agent, in the mixed solvent of dimethyl sulfoxide and water. From the experimental results, the viscosity of polyvinyl alcohol solution is found to increase not only with an increment of boric acid content, but also with the temperature in the range of 70°C ϳ 100°C, although the viscosity is decreased in the range of 30°C ϳ 70°C. Moreover, the molecular mass between junctions of polyvinyl alcohol gel is calculated from the rubber elastic theory and found to be decreased with the increment of boric acid content. We also evaluated the values of Young's modulus of polyvinyl alcohol gel, E, E*, and the elastic parameters C 1 and C 2 of the Mooney-Rivlin equation, according to Hook's law and theory of rubber elasticity. Based on these, the polyvinyl alcohol gel behaves as a good rubberlike elastic property.
ABSTRACT:In this article, we have successfully synthesized polyurethanes (PUs) with a covalent bond of dye molecule via a coupling agent of epichlorohydrin. The structure is proven by infrared (IR) spectra, which exhibits the absorption peak of dye molecule, as we expected. The dye-grafted polyurethanes were used to evaluate their inherent viscosity, mechanical, and thermal properties and, also, their dyeing behavior. For the inherent viscosity, the PUs with the grafting of the dye molecule demonstrate a lower value of viscosity than those without grafting of the dye molecule. The tensile strength is found to decrease with the grafting of the dye molecule due to the further separation of intermolecular distance of the grafted PUs. But the elongation at break is increased with the grafting of the dye molecule. In consideration of the thermal properties, PUs with the grafting of dye molecule exhibit higher T g h than those without dye molecule. However, their T g s and T m s of soft segment between dyed and undyed PU seem to be similar. For dye migration property, the PUs with the grafting of dye molecule are proven to be much lower thermal migration values (Mp%) than those of simple mixing of PU and dyestuff.
A silicon-containing water-borne polyurethane (PU) polymer with hydroxyl side groups was synthesized that was stable in basic conditions and also capable of reacting with a reactive dye to form a covalently bonded dye molecule. The silicon-containing anionic water-borne PU prepolymer was synthesized from H 12 -4,4Ј-diphenylmethane diisocyanate (H 12 -MDI), polytetramethylene glycol, polydimethylsiloxane (PDMS), 2,2Ј-bis(hydroxymethyl), propionic acid (anionic centers), and triethyleneamine using the prepolymer mixing method. Water was then added to emulsify and disperse the resin to form an anionic water-borne PU prepolymer. N-(2-Hydroxyethyl ethylene diamine) (HEDA) was used to extend the prepolymer to form a water-borne PU polymer with a side chain of hydroxyl groups, which can further react with the reactive dye to form a dyed PU. The reactive dye of chlorosulfuric acid esters of sulfatoethyl sulfones can react with the water-borne PU polymer. Behaviors of alkali resistance and dyeing properties were observed. In consideration of thermal properties, the dye-grafted PU polymers exhibited lower glasstransition temperatures for soft segments and hard segments than those without dye. Concerning mechanical properties, it was found that the modulus and the strength of the dyed PU polymers decreased with grafting of the dye molecule, but elongation at break was increased. The alkali resistance increased with PDMS content. For dye-uptake properties, the percentage of dye grafting was over 90%. Also, the dye-grafted PU exhibited a lower percentage of dye migration than that of polymers with ethylene diamine instead of HEDA as a chain extender, and showed greater colorfastness to light.
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