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Toxicological information

Basic toxicokinetics

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Administrative data

Endpoint:
basic toxicokinetics, other
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
Oct. 2019
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Report date:
2019

Materials and methods

Objective of study:
other: speed of polymerization
Test guideline
Qualifier:
no guideline available
Principles of method if other than guideline:
Calorimetric techniques were used to monitor the bulk polymerization of cyanoacrylate monomers in aqueous solutions and on glass surfaces. The kinetics of base-catalysed solution polymerization of cyanoacrylates has been extensively studied using adiabatic calorimetry, whereby polymerization reactions are carried out in a calorimeter and followed by monitoring the exothermic response in the thermogram (deltaT°C vs. time curves).

Furthermore, ATR FT-IR spectroscopy was used to monitor real-time polymerization of a droplet of ECA monomer when exposed to a fine mist of water droplets. Real-time monitoring was performed by follwing the disappearance of the C=C and -CN stretch absorption bands at 1287 cm-1 and 2239 cm-1 respectively, with concomitant formation of the -CH2- stretch absorption band at 1250 cm-1.
GLP compliance:
no

Test material

Constituent 1
Reference substance name:
Ethyl-2-cyanoacrylate
IUPAC Name:
Ethyl-2-cyanoacrylate
Details on test material:
Purity: >98%
Radiolabelling:
no

Results and discussion

Any other information on results incl. tables

1.) Bulk Polymerisation Studies of Ethyl/ Allyl Cyanoacrylate Monomers in Aqueous Systems

Ethyl cyanoacrylate [batch number L27390417] monomers were tested for their reactivity in the presence of added water (50μL, both tap and deionised). Addition of 50μL of water (tap water or deionised) to 50μL of ECA [L27390417] with continuous stirring in the polypropylene tube resulted in an increase in viscosity as ECA rapidly separated into small droplets due to insolubility in an aqueous medium and forming an emulsion. The small droplet size results in a relatively large interfacial surface area to volume ratio which results in an immediate slow polymerization at the monomer-water interface. Initially the ECA/tap water exotherms are more rapid than the deionised water exotherms but the rate of polymerization then decreased relative to the deionised water exotherm. This is likely due to a faster initial polymerization in tap water due to the presence in tap water of various anionic impurities which can trigger more rapid initial polymerization, resulting in polymer formation which in tum affects mixing efficiency and possible emulsion formation. There are also undoubtedly polymer molecular weight and polymer hydrolysis effects in play here also. The tap water exotherms also give an almost constant plateau temperature which is potentially indicative not that polymerization has stopped, but rather that rate of heat production is matched by the rate of cooling. The ECA/deionised water exothenn displays an initially slower exotherm but after 1.5-2 minutes a more rapid exotherm is observed along with a significant increase in mixture coalescence/viscosity. This could be due to emulsion formation effects resulting in a higher surface area to volume ratio and hence more rapid polymerization after the initial slow exotherm. The presence of inhibiting/retarding acids present in the monomer could also be of importance here.

Within several minutes the appearance of both tap and deionised water/monomer-polymer mixtures were very similar with the formation of apparently fully/almost fully cured wet granular polymer. In both cases it is evident that ECA monomer rapidly polymerizes within seconds - minutes to poly(ECA) polymer.

2.) Bulk Polymerization Studies of ECA Monomers on Glass Beads

ECA monomers were observed to completely soak into the beads and then, within 4 - 10 seconds, rapid polymerization ensued as observed by the exothermic traces, resulting in a brittle polymer mass.

3.) Attenuated total reflectance FT-IR Spectroscopy Studies

At T = 0, the strong C=C stretch vibration absorption band can be clearly seen at 1287 cm-1 while there is no absorption due to the -CH2- stretch at 1250 cm-1, clearly indicating the presence of unpolymerized CA monomer. Following the application of a fine spray of water to the CA monomer droplet FT-IR scans were then ran approximately every 15-30 seconds for the next ten minutes to monitor changes in the degree of polymerization. As polymerization advances the C=C stretch vibration absorption band at 1287 cm-1 disappears and this is accompanied by formation of the -CH2- stretch at 1250 cm-1. The observed changes in the spectra are clear evidence for the rapid, instantaneous polymerization of ECA monomer on exposure to water in the form of a fine mist. The FT-IR traces also indicate that polymerization starts within seconds of exposure of the ECA monomer to the water and that polymerization is complete within minutes.

This is further supported by analysis of the changes in the nitrite (CN) stretch vibration at 2239 cm-1 as polymerization advances. The change in the -CN stretch vibration is characteristic for CA polymer as a result of the change in conjugation of the nitrite with the carbon-carbon double bond (in the monomer) to a nonconjugated nitrite in the polymer. CA polymer typically shows very weak or no absorption bands due to the nitrile group.

Applicant's summary and conclusion

Conclusions:
Depending on the specific reaction conditions, ethyl 2-cyanoacrylate polymerises within seconds to minutes after contact to moisture. Hence, it is not possible to reach sufficently high concentrations of monomeric ethyl 2-cyanoacrylate in an aquous environment for an appropriate time period required to test toxicological endpoints.
Executive summary:

Speed of polymerisation of ethyl 2-cyanoacrylate was determined by the use of calorimetric techniques and ATR FT-IR spectroscopy. Calorimetry studies were performed to investigate bulk polymerisation in a polypropylene test tube after addition of water and on glass beads by recording the resulting exotherm over the period of time. On glass beads, an immediate increase of the exotherm within the first seconds of the study indicated a rapid polymerisation of the material. Mixing of ethyl 2-cyanoacrylate with the same amount of water in a polypropylene tube resulted in a somewhat slower start of polymerisation, due to continuous stirring of the mixture over the first 1.5 minutes of the study. Temperature increased significantly after mixing has stopped, reaching a maximum about 2 minutes after the start of the study.

Rapid polymerisation of ethyl 2-cyanoacrylate was further confirmed by following the time-dependet loss of the C=C and CN  stretch vibration absorption and the appearance of the C-CH2 stretch vibration absorption in an ATR FT-IR experiment.