Abstract
Two series of new thermoplastic poly(thiourethane-urethane) elastomers (EPTURs), with different hard-segment content (40–60 wt%), were synthesized by a one-step melt polymerization from poly(oxytetramethylene) diol (PTMO) of $$ \overline{M}_{\text{n}} $$ = 1,000 g mol−1 or poly(hexamethylene carbonate) diol (PHCD) of $$ \overline{M}_{\text{n}} $$ = 860 g mol−1 as a soft segment, hexane-1,6-diyl diisocyanate and (methylenedi-1,4-phenylene)dimethanethiol as a chain extender at the NCO/(OH + SH) molar ratio of 1. The structures of all the EPTURs were examined by Fourier transform infrared spectroscopy (FTIR), atomic force microscopy and X-ray diffraction analysis. Their thermal behavior was investigated by means of differential scanning calorimetry and thermogravimetric analysis (TG). For the chosen polymers the gaseous products evolved during the decomposition process were analyzed by TG-FTIR. Moreover, physicochemical, adhesive and tensile properties as well as Shore A/D hardness were determined. The resulting high-molecular-mass EPTURs were stable up to 254–262 °C, as measured by the temperature of 1 % mass loss. They decomposed in three or four stages. The main decomposition products were carbonyl sulfide, isocyanate, carbon dioxide, aromatic hydrocarbons as well as aliphatic ethers and aldehydes (in PTMO series) and alcohols (in PHCD series). All the polymers showed partially crystalline structures, associated with crystallization of thiourethane hard segments. Their melting temperatures were in the range of 184–186 °C. The PTMO series EPTURs exhibited better low-temperature properties (glass-transition temperature in the range of −64 to −44 vs. −26 to −22 °C), but poorer tensile strengths (20–28 vs. 37–43 MPa). These EPTURs showed improved adhesive properties in comparison with their polyurethane analogs.
Highlights
Sulfur-containing polymers, when considering their structure, make up a complex group of macromolecular compounds of varied and often remarkable features that determine their versatile applications
In our previous paper [14], we describe two series of polymers obtained by melt polymerization from bis[4-(sulfanylmethyl)phenyl]methanone, HDI, and poly(oxytetramethylene) diol (PTMO) of Mn = 1,000 g mol-1 or poly(hexamethylene carbonate) diol (PHCD) of Mn = 860 g mol-1 as a soft segment
The use of PHCD produced polymers with significantly higher tensile strengths (36.8–42.6 vs. 20.4–28.0 MPa) and higher Tgs (-26 to -22 vs. -64 to -44 °C), which to some extent limits the possibility of applications of these polymers as elastomers within negative temperatures
Summary
Sulfur-containing polymers, when considering their structure, make up a complex group of macromolecular compounds of varied and often remarkable features that determine their versatile applications. (methylenedi-1,4-phenylene)dimethanethiol (DT), which is easier to obtain and due to its lower melting temperature (Tm) more suitable for the synthesis of polyurethane elastomers by melt polymerization with aliphatic diisocyanates Application of this chain extender that introduces diphenylmethane units with active methylene groups into polymer structure facilitates the cross-linking of these polymers by peroxide and improves their mechanical strength properties [16]. Basic physicochemical, mechanical and adhesive properties were determined It includes a characterization of the newly obtained poly(thiourethane) (PTUR) based on DT and HDI, building the thiourethane hard segment in these EPTURs. In order to facilitate the interpretation of the results, syntheses of polyurethanes not containing chain extender DT The plates were fixed by tensile-testing machine clips and underwent tensile testing, the speed of 2 mm min-1 at 23 °C
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