Polybutadiene

Polymers from 1,3-butadiene (schematic presentation)

Section from a polymer chain of cis -1,4-polybutadiene. A C 4 unit is circled in blue .

Section from a polymer chain of trans -1,4-polybutadiene. A C 4 unit is circled in blue .

Section from a polymer chain of isotactic 1,2-polybutadiene. A C 4 unit is circled in blue . The vinyl groups can be seen in the side chains .

Section from a polymer chain of syndio tactical 1,2-polybutadiene. A C 4 unit is circled in blue . The vinyl groups can be seen in the side chains .

Polybutadiene is a collective name for homopolymers made from 1,3-butadiene . Polybutadiene one of the synthetic rubbers and also as a butadiene rubber ( abbreviated BR from English butadiene rubber referred to).

In terms of global consumption, polybutadiene is the second most important synthetic rubber, accounting for about a quarter of the market volume in 2012.

Manufacturing

Polybutadiene can be produced by means of anionic, coordinative or radical chain polymerizations . Depending on the type of polymerization, polybutadienes are formed with structural units that appear differently. The CC double bonds in the repeat units can occur as 1,4- cis , 1,4- trans or 1,2-units. A 1,2-unit corresponds to a vinyl group , the double bond is in the side chain.

Free radical chain polymerization : Emulsion polymerization leads to a random occurrence of the three sequences. At a low reaction temperature (5 ° C) the proportion of vinyl groups decreases. Initiation takes place with potassium peroxodisulfate and iron salts. With hydrogen peroxide as the initiator , short-chain macromolecules can be produced, which lead to terminal diols through initiation and termination reactions with OH radicals ( telechelic ). As diols , they are used for the synthesis of elastomeric polyurethanes .

Anionic chain polymerization : The chain polymerization is initiated with butyllithium . The polybutadiene obtained in this way contains about 40% 1,4- cis and 50% 1,4- trans units. In this way, however, butadiene is preferably converted to copolymers, such as styrene-butadiene rubbers , styrene-butadiene-styrene block copolymers or acrylonitrile-butadiene-styrene copolymers .

Coordinative chain polymerization : The stereospecific Ziegler-Natta catalysts lead to a polymer with a high proportion of 1,4- cis units. Vulcanizates of this polymer are used as elastomers .

	Polymerization	cis -1.4 units (%)	trans -1.4 units (%)	1.2 units (%)
Neodymium	coordinative	98	1	1
Cobalt	coordinative	97	1	2
nickel	coordinative	97	2	1
titanium	coordinative	93	3	4th
Butyllithium	anionic	36 to 38	52 to 53	10 to 12

Polybutadiene has a high elasticity and can be used in the temperature range from - 80 ° C to 90 ° C. Even without fillers, polybutadiene has good strength (similar to natural rubber) and excellent abrasion resistance, and when filled and vulcanized it also has a high resistance to cracking.

use

70% of the polybutadiene produced worldwide is used in the manufacture of tires.

To improve the properties and processability, polybutadiene is mixed with natural rubber or styrene-butadiene rubber SBR. It is used in car tires and golf ball cores .

Individual evidence

1. ^ MD Lechner, K. Gehrke, EH Nordmeier: Makromolekulare Chemie. 4th edition. Birkhäuser Verlag, 2010, ISBN 978-3-7643-8890-4 , p. 29.
2. ↑ Arne Peters: Elastomer market with perspective. ( Memento of the original from July 14, 2014 in the Internet Archive ) Info: The  archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. In: K newspaper. June 24, 2013.
3. ↑ Bernd Tieke: Macromolecular Chemistry. 3. Edition. Wiley-VCH, Weinheim, 2014, p. 93.
4. ↑ Bernd Tieke: Macromolecular Chemistry. 3. Edition. Wiley-VCH, Weinheim, 2014, p. 114.
5. ↑ Bernd Tieke: Macromolecular Chemistry. 3. Edition. Wiley-VCH, Weinheim, 2014, p. 149.
6. ↑ Dirk Steinborn: Fundamentals of organometallic complex catalysis. Vieweg + Teubner, Wiesbaden 2010, p. 232. (Restricted preview)