The Preparation, Properties and Potential Applications of “Diimide-Hydrogenated” Styrene-Butadiene (HSBR) and Polybutadiene (HBR) Thermoplastic Elastomers

Abstract

Our unique diimide-based process for preparing HNBR latex from NDR latex without the use of hydrogen, noble metal catalysts or solvents has now been successfully extended to the preparation of hydrogenated thermoplastic elastomers latexes directly from SBR or BR latex precusors. Commercially available SBR latex such as SBR 1502 can be readily reduced to high saturation levels (95+%) via the diimide reduction technique. Latex cast films of the highly reduced elastomer show excellent ozone and oxidation resistance as expected. Unexpectedly however, the hydrogenated polymer films demonstrate high tensile strength and thermoplastic elastomer (TPE) behavior. The TPE properties have been found to be caused by polyethylene crystallites that exist even in the unstretched films under ambient conditions. Latex is an unusual physical form for a TPE material. As a latex, TPE elastomers can be fabricated into sheets or other products by simple dipping or spraying methods—methods not normally available to TPEs in bulk form. In this regard, HSBR or HBR could function as superior replacements for natural rubber (NR) latex in articles such as tubing, gloves, condoms etc., where ozone and oxidation resistance may be required or in applications where good strength properties coupled with the absence of potentially allergenic proteins and/or curatives may be desirable. Alternatively, HSBR or HBR latexes may also be conventionally coagulated and processed using standard rubber/TPE compounding techniques.

Influence of styrene content on the hydrogenation of styrene-butadiene copolymer

“…This happens in the low-temperature region only. 9 Contrary to the expectation, the thermal stability of HSBR is less than that of SBR in the presence of air in the temperature range between 280 and 480°C and the thermal stability of SBR in air is higher than in nitrogen. 21 A similar observation was made here also.…”

“…7,8 It has also been claimed that newer thermoplastic elastomeric latexes could be obtained by this technique. 9 Scientifically, it is interesting to alter the properties of the butadiene units of SBR and to generate new polymers with controlled crystalline segments. Both the microstructure of butadiene units and the styrene level are expected to influence the hydrogenation reaction, although a literature search revealed that these have not been reported.…”

Thermoplastic elastomeric hydrogenated styrene-butadiene elastomer: Optimization of reaction conditions, thermodynamics, and kinetics

“…Wideman 4 discovered that an elastomer in latex form can be converted directly into its saturated analogue when treated with hydrazine able solvent, or hydrogen gas. Parker et al 5 later 30% hydrogen peroxide was added dropwise over the specific period of time with the help of a dropprepared hydrogenated styrene-butadiene rubber (SBR) latex by the diimide reduction technique ping funnel. The volume of H 2 O 2 was varied from 10 to 40 mL (0.09 to 0.35 mol).…”

Preparation of a Polyethylene Latex by Catalytic Hydrogenation of a Polybuta‐1,4‐diene‐Based Dispersion

“…Since this early effort, a number of studies have been published in this area, but all of them mainly focus on enhancing the properties of latexes based on acrylonitrile-butadiene [6][7][8][9][10][11] and styrene-butadiene rubbers. [12][13][14][15] Until now, no group has taken advantage of the hydrogenation reaction to generate polyethylene (PE) latex. Such a route is potentially of great interest to produce a purely linear PE-based latex with very different properties from those of branched PEs produced by free radical emulsion polymerization.…”