Chlorinated paraffins: chapter 2

2. Identity and physical/chemical properties

2.1 Identity

As was the case for the first Priority Substances List (PSL1) assessment, short-chain chlorinated paraffins (SCCPs), medium-chain chlorinated paraffins (MCCPs) and long-chain chlorinated paraffins (LCCPs) are assessed separately in this report.

2.1.1 Composition of CP Mixtures

SCCPs (C_10-13), MCCPs (C_14-17) and the lower chlorinated LCCPs are mixtures that are viscous, colourless or yellowish dense oils. C_>20 highly chlorinated alkanes are waxy solids at ambient temperatures. The average chlorine content by weight is 30-52% for C_18-20 liquid products, 40-54% for C_>20 liquid products, and 70-72% for C_>20 solid products.

Impurities in commercial CPs are likely to be related to those present in the n-alkane feedstocks, which consist of a mixture of homologues. Furthermore, the n-alkanes may contain branched alkanes (usually <1%) and aromatics (<0.1%), which could be chlorinated. Commercial mixtures also contain stabilizers, which include epoxidized esters and soya bean oils, erythritol, thymol, urea, glycidyl ethers, acetonitriles and organic phosphates (European Commission, 2000; Schenker 1979; Houghton 1993). Various stabilizers are often added to commercial CP products in order to improve their thermal stability or light stability.

2.2 Physical/chemical properties

The large difference in chlorine content is primarily responsible for the large differences that are evident in measurements and estimates of physical/chemical properties. The approximate range of molecular weights for SCCPs is 320-500 (European Commission, 2000), for MCCPs is 235-825 (U.K. Environment Agency 2003) and for LCCPs is 325-1355 (U.K. Environment Agency 2001).

Presented in Table 1 are ranges of physical properties for SCCPs, MCCPs and 3 subclasses of LCCPs.

Table 1: Range of physical properties of CPs congeners
CP class	Vapour pressure^Footnote a (Pa)	Henry's law constant (Pa·m³/mol)	Water solubility (µg/L)	log K_OW	log K_OA	Log K_OC	Reference^Footnote b
SCCPs	2.8 × 10^-7 - 0.028 (48 - 71% Cl)	0.68 - 17.7	6.4 - 2370 (48 - 71% Cl)	4.39 - 8.69 (48 - 71% Cl)	8.2 - 9.8 (48 - 56%Cl)	4.1 - 5.44	1-7, 14, 15
MCCPs	4.5 x 10^-8 - 2.27 × 10^-3 (42 - 58% Cl)	0.014 - 51.3 (37 - 56% Cl)	9.6 x 10^-2 - 50 (37 - 56% Cl)	5.47 - 8.21 (32 - 68% Cl)	8.81 - 12.96 (32 - 68% Cl)	5.0 - 6.23	4, 5, 6, 7, 8, 9, 10, 11
C_18-20 liquid LCCPs	2 × 10^-5 - 5 × 10^-4 (40 - 52% Cl)	0.021 - 54.8 (34 - 54% Cl)	0.017 - 6.1 (34 - 54% Cl)	7.34 - 7.57 (34 - 54% Cl)	9.21 - 12.12^Footnote c (34 - 54% Cl)	-	4, 10, 11, 12
C_>20 liquid LCCPs	3 × 10^-15 - 2.7 × 10^-3 (40 -54% Cl)	0.003 (50% Cl)	1.6 × 10^-6 - 6.6 (41.9 - 50% Cl)	7.46 - 12.83 (42 - 49% Cl)	-	-	4, 5, 6, 9, 10, 12, 13
C_>20 solid LCCPs	1 × 10^-23 - 3 × 10^-14 (70%Cl)	3.6 × 10^-7 - 5.6 × 10^-6 (70 -71.3% Cl)	1.6 × 10^-11 - 5.9 (70 - 71.3% Cl)	-	-	-	4, 5, 12

Footnotes

Footnote a

Return to footnotea Referrer

Vapour pressure values not given at a consistent temperature.

Footnote b

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References: 1. Drouillard et al. (1998a), measured data; 2. Drouillard et al. (1998b), estimated data; 3. Sijm and Sinnige (1995), measured data; 4. BUA (1992), estimated data; 5. Madeley et al. (1983a), measured data; 6. Renberg et al. (1980), thin-layer chromatography (TLC) - K_OW correlation; 7. Fisk et al. (1998a), measured data; 8. U.K. Environment Agency (2003), measured data; 9. Campbell and McConnell (1980a), measured data; 10. BUA (1989), measured data; 11. Sijm and Sinnige (1995), estimated data; 12. U.K. Environment Agency (2001), estimated data; 13. Howard et al. (1975), estimated data; 14. Drouillard (1996), measured and estimated; 15. Thompson et al. (1998), measured.

Footnote c

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Octanol-air partition coefficients, estimated from ratio of K_OW/HLC (unitless).

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Date modified:: 2019-06-18

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