Segmented block copolymers of natural rubber and propylene glycol‐toluene diisocyanate oligomers

Abstract

Segmented block copolymers were synthesized from hydroxyl terminated liquid natural rubber (HTNR) and polyurethane oligomers based on 1,2‐propylene glycol and toluene diisocyanate (TDI) by one‐shot and two‐shot processes in solution. They were completely phase segregated. Structural features were characterized by infrared and nuclear magnetic resonance spectroscopies. The two‐phase morphology was deducted from thermal analysis and dynamic mechanical analysis (DMA). The soft segment glass transition temperature was about −64°C and the hard segment glass transition was between 70°C and 100°C depending on the polyurethane content. The two‐phase morphology was corroborated by a two‐stage thermal decomposition of the products. The morphology consisted of a heterogeneous dispersion of beads in a continuous matrix. The large size and the nature of the beads suggest that they are independent of the block copolymer structure and are formed by the agglomeration of the polyurethane homopolymers, which remain unbonded to the rubber chains during chain extension. At lower hard segment contents the materials behaved like quasi‐elastomers, and at higher hard segment contents, they were like tough plastics. At intermediate compositions they behaved as rigid elastomers. Variations in hardness and tear strength were consistent with this behavior.

Synthesis and characterization of a poly(ether–ester) copolymer from poly(2,6 dimethyl‐1,4‐phenylene oxide) and poly(ethylene terephthalate)

“…7 Poly(ether-ester)s and poly(ester-ester)s are two types of segmented copolymers with a wide range of applications. 8 Some of these copolymers show a single glass transition temperature (T g ) that is intermediate between the T g s of the pure components. 3 For these materials, the evolution of the copolymer T g with respect to hard or soft segment composition has been successfully described by mixing rules used for compatible copolymers 9 (as Gordon-Taylor equation).…”

Segmented block copolymers of natural rubber and bisphenol A-toluene diisocyanate oligomers

“…On comparing the T g values of these samples with those of the polyurethane elastomers based on aliphatic chain extenders, 20 such as ethylene glycol (EG), propylene glycol (PG), 18 1,3-butane diol (1,3-BDO), and 1,4-butane diol (1,4-BDO), it is observed that the methyl and phenyl groups in BPA have got some remarkable influence in their thermal properties. Table III presents a comparative account of the T g values of various polyurethanes.…”

Synthesis and thermal studies of block copolymers from NR and MDI‐based polyurethanes

“…[14][15][16] The two types of segments, viz., the NR and polyurethane are termed as the soft and hard segments, respectively. NR behaves as the soft segment due to its inherent flexibility.…”

“…[14][15][16] Required stoichiometric amount of HTNR (Table I) was dissolved in chloroform (25% w/v), DBTDL catalyst, quantity of which was noted in a later section, viz., ''Copolymer synthesis'', was added and the solution was brought to reflux at 60-658C. The final stoichiometric amount of MDI in chloroform (25% w/v) was dropped into it over a period of 30 min, followed by one and a half hour reaction to endcap the HTNR.…”

“…Recent example to this category of block copolymers are those based on liquid natural rubber and polyurethane oligomers. [14][15][16] The latter constituent is the hard phase and it has been derived from a dissymmetric diisocyanate, viz., 2,4-toluene diisocyanate on reaction with a chain extender diol such as propylene glycol, 1,3-butane diol or bisphenol A. However, it is interesting to follow the effect of symmetric diisocyanate such as MDI (4,4 0 -diphenyl methane diisocyanate) on the properties of this group of block copolymers.…”