Solution properties of NR/PU block copolymers by size‐exclusion chromatography and viscometry

Abstract

Soluble block copolymers based on natural rubber and polyurethane oligomers derived from 1,3 butane diol and toluene diisocyanate were synthesized for the first time. The dilute solution properties of these block copolymers dissolved in tetrahydrofuran (THF) were studied by viscometry and gel permeation chromatography (GPC). The Mark-Houwink constants K and a of the block copolymer system were determined by the molecular weight data from GPC combined with the viscosity data. Both the values were found to be in the range usually given by flexible elastomers. The intrinsic viscosity values were found to decrease successively with a decrease in the NCO/OH ratio from 1.12 to 1.05. The unperturbed chain parameters, K h and B were determined from the viscosity data. The K h calculated was used to get the unperturbed end-to-end distance and radius of gyration of the block copolymer systems in THF. The viscosity data were also used to study the chain conformation in dilute solutions. It was found that the molecules adopt a compressed core and shell conformation in which the higher molecular weight component, NR, forms the shell, which compresses the PU core. All the block copolymers assume a compressed segregated core and shell model which changes to a partially segregated core and shell conformation, or partially Gaussian conformation, at the transition temperature located at 70 8C.

Elaboration and properties of renewable polyurethanes based on natural rubber and biodegradable poly(butylene succinate) soft segments

“…Dynamic mechanical thermal analysis was investigated by using a Rheometric Scientific V R DMTA V. The experiment was carried out in the dual-cantilever bending mode at a frequency of 1 Hz with a strain control of 0.01%, a heating rate of 38C min 21 , and a temperature range of 280 to 2008C.…”

“…The hardness Shore A (ASTM D2240) was investigated by a Shore Durometer V R PTC 408. The tensile properties (ASTM D 412C) and tear strength (ASTM D 624 for the right-angle specimen) were determined by a universal testing machine (Lloyd V R LR10K) at a crosshead speed of 500 mm min 21 . Testing was performed at 258C 6 28C.…”

“…15,17,25,26 Briefly, controlled oxidative chain cleavage of natural rubber, using periodic acid afforded carbonyl telechelic natural rubber (CTNR). The reduction of CTNR by NaBH 4 led to HTNR with M n $ 1700 g mol 21 . The FTIR analysis of HTNR showed mainly characteristics band of hydroxyl stretching vibration at 3365 cm 21 , C@C stretching vibration at 1664 cm 21 and C@CAH bending vibration at 834 cm 21 .…”

“…The reduction of CTNR by NaBH 4 led to HTNR with M n $ 1700 g mol 21 . The FTIR analysis of HTNR showed mainly characteristics band of hydroxyl stretching vibration at 3365 cm 21 , C@C stretching vibration at 1664 cm 21 and C@CAH bending vibration at 834 cm 21 . The 1 H NMR showed the total disappearance HTPBS was prepared by reacting 1,4-butanediol and succinic acid in 1.2:1 initial molar ratio.…”

“…[10][11][12][13][14][15][16][17] HTNR has been used as a starting material (Polyol) in the preparation of many kinds of polyurethanes. [12][13][14][15][18][19][20][21][22][23][24] In addition, our group reported recently the preparation of bio-based polyurethane from HTNR and poly(ecaprolactone) (PCL). 25,26 Polybutylene succinate (PBS) is a promising biodegradable and renewable aliphatic polyester which can be prepared from succinic acid and 1,4-butanediol.…”