Nitrosamine Free Rubber Compounds – Replacing a Hazardous Thiuram Accelerator with Safe Alternatives
Pekkonen, Joonas (2018)
Pekkonen, Joonas
2018
Teknis-luonnontieteellinen
Teknis-luonnontieteellinen tiedekunta - Faculty of Natural Sciences
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Hyväksymispäivämäärä
2018-12-05
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tty-201811212665
https://urn.fi/URN:NBN:fi:tty-201811212665
Tiivistelmä
Vulcanization is the process of cross-linking rubber to form a three-dimensional network giving rubber its characteristic properties. The most common form of vulcanization is sulfur vulcanization, where sulfur atoms form the cross-links in the structure. Accelera-tors are used in sulfur vulcanization to boost the vulcanization, i.e. to reduce the time and temperature required for the reaction between polymers.
Tetramethylthiuram disulfide (TMTD) is a fast thiuram accelerator, often used in combi-nation with other accelerators to boost their performance. Using TMTD causes a problem, as potentially carcinogenic nitrosamines can form as byproducts in the vulcanization.
The purpose of this thesis was to improve the safety of rubber manufacturing and rubber products by replacing TMTD with a safer accelerator. The goal was to find replacements for TMTD and create new recipes for the two rubber compounds studied. The studied compounds were a mixture of natural rubber and bromobutyl rubber, denoted as com-pound A, and a mixture of styrene butadiene rubber and acrylonitrile butadiene rubber, denoted as compound B. Both compounds originally had a vulcanization system, where TMTD was used in combination with the dibenzothiazyl disulfide (MTBS) accelerator.
Test compounds were mixed from both compounds and tests were carried out to deter-mine the effects of varying the accelerators and their amounts on the properties of the rubber compounds. The tested accelerators for compound A were tetrabenzylthiuram di-sulfide (TBzTD) and Vultac TB710. The choice for compound B was limited, because this compound is used in a food contact application and it needs to fulfill regulations. Thus, the only test accelerator for compound B was zinc dibenzyldithiocarbamate (ZBEC).
For compound A, a successful replacement for TMTD was found from Vultac TB710, used in combination with the N-tert-butyl-2-benzothiazole (TBBS) accelerator. The cor-rect amounts of MBTS and ZBEC for compound B were found using central composite design (CCD) method and analyzing and optimizing the results with the Design Expert 11 statistical program.
This thesis confirms that a nitrosamine producing accelerator such as TMTD can be re-placed by a safer alternative without altering the compound in other ways. Two different types of cases have been demonstrated and these examples propose a good basis to extend the replacement to other rubber compounds and other hazardous nitrosamine producing accelerators.
Tetramethylthiuram disulfide (TMTD) is a fast thiuram accelerator, often used in combi-nation with other accelerators to boost their performance. Using TMTD causes a problem, as potentially carcinogenic nitrosamines can form as byproducts in the vulcanization.
The purpose of this thesis was to improve the safety of rubber manufacturing and rubber products by replacing TMTD with a safer accelerator. The goal was to find replacements for TMTD and create new recipes for the two rubber compounds studied. The studied compounds were a mixture of natural rubber and bromobutyl rubber, denoted as com-pound A, and a mixture of styrene butadiene rubber and acrylonitrile butadiene rubber, denoted as compound B. Both compounds originally had a vulcanization system, where TMTD was used in combination with the dibenzothiazyl disulfide (MTBS) accelerator.
Test compounds were mixed from both compounds and tests were carried out to deter-mine the effects of varying the accelerators and their amounts on the properties of the rubber compounds. The tested accelerators for compound A were tetrabenzylthiuram di-sulfide (TBzTD) and Vultac TB710. The choice for compound B was limited, because this compound is used in a food contact application and it needs to fulfill regulations. Thus, the only test accelerator for compound B was zinc dibenzyldithiocarbamate (ZBEC).
For compound A, a successful replacement for TMTD was found from Vultac TB710, used in combination with the N-tert-butyl-2-benzothiazole (TBBS) accelerator. The cor-rect amounts of MBTS and ZBEC for compound B were found using central composite design (CCD) method and analyzing and optimizing the results with the Design Expert 11 statistical program.
This thesis confirms that a nitrosamine producing accelerator such as TMTD can be re-placed by a safer alternative without altering the compound in other ways. Two different types of cases have been demonstrated and these examples propose a good basis to extend the replacement to other rubber compounds and other hazardous nitrosamine producing accelerators.