Han X. Xiao

Novel Fluorine-Containing Anionic Aqueous Polyurethanes

Abstract Various amounts of fluorine-containing polyol (F-diol, MW = 3700) were introduced into the soft segment of anionic aqueous polyurethanes (PUs) to examine the effect of the F-diol on the properties of the anionic aqueous PUs. The hard segments in the anionic aqueous PUs consisted of 4,4′-methylene bis(cyclohexylisocyanate), dimethylolpropionic acid, and 1,4-cyclohexanediamine (cis/trans = 80/20). Both the mechanical and water resistance properties of the anionic aqueous PUs were improved after introducing small amounts of the F-diol in the soft segment of the aqueous PUs. This is due to the increased intermolecular forces and crystallinity as well as the hydrophobic characteristic of the F-diol. Thermal analysis of the F-diol modified anionic aqueous PUs by differential scanning calorimetry and dynamic mechanical analysis indicated that both intermolecular forces and crystallinity increased with increasing concentration of the F-diol. However, both the increased intermolecular forces and crystalli...

Thermostability of Urethane Elastomers Based on p-Phenylene Diisocyanate

Polyurethane (PU) elastomers based on p-phenylene diisocyanate (PPDI), poly(oxytetramethylene) glycol or poly(1,6 hexamethylene adipate) gly col and 1,4-butanediol were prepared at different NCO/OH ratios, and the mechanical property changes of these elastomers after heat aging at 150 °C were examined in the presence and absence of various antioxidants. It was found that the highest retention of mechanical properties of the polyether based PU elastomers were achieved with Irganox 1010 followed by Irganox 1024. There was no synergism observed in the combinations of antioxidants. The thermal oxidation stability of PUs based on polyester polyol was better than one based on polyether polyol. Both NCO/OH ratio and the methods of ad dition of antioxidants to PU elastomers affect the final thermostability of the elastomers.

Polyurethane-Urea Anionomer Dispersions. II

Abstract Polyurethane-urea anionomer dispersions containing about 50% hard segments were prepared from poly(oxypropylene) glycols, toluene diisocyanate (TDI), or a mixture of TDI and polymeric MDI (PMDI), dimethylolpropionic acid (DMPA), 1,4-butanediol (BD), and different diamines as chain extenders. The structure-properties relationships of these polyurethane-urea anionomers were studied. The effects of compositional ratio, type of chain extender, and isocyanate structure on the morphology and properties of the dispersion-cast films were investigated by means of differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and determination of mechanical properties.

Kinetic studies of the reactions between isocyanates and carboxylic acids

Reaction kinetic studies between isocyanates and carboxylic acids were undertaken to evaluate the kinetic parameters. Various isocyanates (phenyl isocyanate, cyclohexyl isocyanate) and carboxylic acids (acetic acid, n-butyric acid, isobutyric acid, dimethylbutyric acid and benzoic acid) were used to study the kinetics of the reactions at different temperatures and in different solvents. It was found that these reactions followed the rate law of second-order reaction. From the Arrhenius plot, the activation energies of these reactions were computed.

Two-Component Interpenetrating Polymer Networks (Ipn's) From Polyurethane and Epoxies The Use of Modified Liquid Moca as Urethane Curative

Modified Liquid MOCA (MLM) has been shown to have potential industrial applications in interpenetrating polymer networks (IPNs). This is due to its lower toxicity, low viscosity, appropriate crosslinking kinetics and ease of handling in comparison with unmodified MOCA. Two-component IPN systems prepared from polyurethanes and epoxies, utilizing MLM as a urethane curative, have exhibited good physical and mechanical properties. One of the most significant advantages of IPNs is their ability to achieve high modulus polymer alloys without the use of fillers that increase viscosities, making processing difficult. Further advances in these systems by the use of MLM as a urethane curative have also lessened many of the processing diffi culties for these materials.

Studies on the Modification of Thermoplastic Polyolefins (TPOs)—Part I. Effect of Various Modifiers on the Adhesion of a Two-Component (2K) Polyurethane Coating to the Modified TPOs:

Thermoplastic polyolefins (TPOs) have low energy surfaces, therefore, they are difficult to be adhered to with adhesive and coating systems. Various modifiers, namely, polycaprolactone, polyvinyl acetate, poly(oxy-ethylene)glycol and polyamides were incorporated into the matrix of TPOs to modify and enhance their surface energy in order to improve adhesion of two component (2K) urethane coatings to their surface. Adhesion was investigated by using the crosshatch adhesion test. Good adhesion of 2K polyurethane coatings to the modified TPOs was achieved by using polyamides based on maleated polypropylene (MPP) and polyetheramine (PEA) (ED4000). The adhesion was found to be dependent on the modifier percentage and the equivalent ratio of MPP to PEA (ED4000).

Secondary Amine Extended Flexible Polyurethane-Urea Foams

n the present work the effects on the physical properties of flexible foams prepared with a new liquid secondary diamine are described. This additive, UNILINK 4200, was first introduced for cast elastomer applications by UOP Inc. in 1986. The current effort summarizes the preliminary evaluation of UNILINK 4200 as an additive in flexible foam applications. The reactivity of secondary amines allows for the incorporation without significant changes in the rise profile. With the addition of UNILINK 4200 a decrease in density is observed. However, it was quite unexpected that the additional urea linkages and hard segment content would afford improved physical properties, such as strength and hardness, even at the lower densities. This benefit of lower foam densities, thus lower costs on a cubic foot basis, together with improved physical properties are expected to provide the polyurethane

Urethane-Based Polymer Alloys (IPNs)

nent polymers. IPNs possess several interesting characteristics in comparison to normal polyblends. Formation of IPNs is the only way of intimately combining crosslinked polymers, the resulting mixture exhibiting (at worst) only limited phase separation. Normal blending or mixing of polymers results in a multiphase morphology due to the well-known thermodynamic incompatibility of polymers. However, if mixing is accomplished simultaneously with crosslinking, phase separation may be kinetically controlled by permanent interlocking of entangled chains. Recent studies in IPNs at the University of Detroit’s Polymer Institute have encompassed a variety of areas, including effects of molecular weight of prepolymers and extent of crosslinking on the morphology and properties, the effects of charge groups and intentional grafts, pseudo-IPNs, and three component IPNs. The polymers studied have been polyurethanes, acrylic polymers and copolymers, and epoxies.

Studies on the Application of Liquid Aromatic Secondary Amines as Chain Extenders and Reactive Carriers for Other Amine or Hydroxyl-Containing Polyurethane Curatives:

Aromatic amines generally react rapidly with aromatic isocyanates. This reaction can be slowed to a controllable rate through the use of secondary amines. This paper demonstrates the versatility of secondary diamines as curatives for toluene diisocyanate (TDI) and diphenyl methane diisocyanate (MDI) based prepolymers. Types of polyols included in the study are polyesters such as polyethylene adipate (PEA) and polycaprolactone (PCP) and polyethers such as poly(oxytetramethylene) glycol (PTMG) and poly(oxypropylene) glycol (PPG).