Influence of varying hard segments on the properties of chemically crosslinked moisture‐cured polyurethane‐urea

Abstract

Polyurethane prepolymers are widely used in the reactive hot melt adhesives and moisture-cured coatings. The chemically crosslinked moisture-cured formulation based on PEG-1000 and isophorone diisocyanate was prepared with NCO/OH ratio of 1.6:1.0. Trimethylol propane was used as a crosslinking agent. The excess isocyanate of the prepolymer was chain extended in the ratio of 2:1 (NCO/OH) with different aliphatic diols, and 4:1 with different aromatic diamines. The polymer network maturation during moisture cure was followed by dynamic mechanical thermal analyzer (DMTA) instrument. The thermal and dynamic mechanical properties of the crosslinked polymers were evaluated using thermogravimetric analysis, differential scanning calorimetric analysis and DMTA. Surface properties were evaluated through angle-resolved X-ray photoelectron spectroscopy.The present article discusses the physical properties of moisture-cured polyurethane-urea (MCPU) containing chemical crosslinks in the hard segment. The complete moisture-cured polymers showed amorous results toward room temperature modulus, tensile strength, hardness, thermal stability, and transparency. The surface properties showed the enrichment of soft segments. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: [102][103][104][105][106][107][108][109][110][111][112][113][114][115][116][117][118] 2006

The phase mixing studies on moisture cured polyurethane-ureas during cure

“…The NCO:OH ratio was maintained at 1.6:1 and 2:1. The detailed synthetic process is reported elsewhere [3,19,20].…”

“…The process of curing defines the properties of the finished coating material. Temperature, humidity level and the state of cure are, therefore, key aspects for understanding and controlling the coating performance [12][13][14][15][16][17][18][19][20]. Yanjun et al [21] modeled the curing process of isocyanate terminated urethane prepolymer based on oligoester or oligoether diols and diisocyanates by isothermal and non-isothermal DSC under saturated humidity level and have shown a second-order autocatalytic model can be successfully used to evaluate cure process.…”

Elaboration and Characterization of Advanced Biobased Polyurethane Foams Presenting Anisotropic Behavior

“…This excess leads to an increase in biuret (Figure d), allophanate (Figure c), or isocyanurate linkage (Figure e). Another way to improve HS content is to increase the weak interchain forces within the hard domains by adding polar groups such as urea …”

Calix[4]arenes Used as a New Type of Chain Extender in the Preparation of Polyurethanes

“…Consequently, the presence of urea groups produce an increase in the hard segment cohesion, and thus, increase the rigidity. [29] Furthermore, the presence of CA [4]-NH 2 increases the stiffness of the polymer. Therefore, the substitution of CA [4]-NH 2 created a larger soft/hard segment polarity difference and, thereby, an enhanced physical crossliking and/or filler effect.…”