MEASUREMENT OF VOC AND SVOC EMITTED FROM AUTOMOTIVE INTERIOR MATERIALS BY THERMAL DESORPTION TEST CHAMBER METHOD K Hoshino 1*, S Kato 2, S Tanabe 3, Y Ataka 4, S Ogawa 1, T Shimofuji 1 1 GL Sciences Inc., Japan 2 Institute of Industrial Science, University of Tokyo, Japan 3 Department of Architecture, Waseda University, Japan 4 Yoshino Gypsum Co., Ltd., Japan ABSTRACT In order to clarify the mechanism of indoor air quality in vehicle cabins, it is important to measure correctly the emission rates of volatile organic compounds (VOC) and semi-volatile organic compounds (SVOC) from automotive interior materials. In this study, we measured VOC and SVOC emitted from automotive interior materials using the Thermal Desorption Test Chamber method (TDC method), which quantified emission rates (ER) of VOC and SVOC of materials at actual temperature. This method was composed of two measurement steps. First, VOC emitted from material in the glass chamber was measured. Second, SVOC adsorbed on the internal chamber surface was measured. As a result, VOC emitted (Toluene, Ethylbenzene, Xylene, Styrene, Cyclohexanone, etc.) and SVOC emitted (BHT, DEP,, DEHP, DINP, DOA, etc.) were confirmed. These results indicated that measurements of VOC and SVOC emitted from automotive interior materials could be carried out effectively. INDEX TERMS VOC, SVOC, Automotive interior materials, Emission rates, Adsorption INTRODUCTION The VDA (an automotive industry association) method is the typical measurement method of emissions from automotive interior materials. A 1-m3 test chamber is used to measure volatile organic compounds (VOC) concentrations in the chamber air, and then a fogging test method is used to measure condensable components of semi-volatile emissions (SVOC) from materials (VDA276-1 2000). A cooling element mounted inside the test chamber is used in the fogging test method. While qualitative determinations of SVOC of emissions can be performed with this method. It is extremely difficult to obtain quantitative determinations. On the other hand, VDA 278 (2001) quantifies VOC and SVOC of emissions, but is applicable only materials, that can fit in the thermal desorption tube (O.D. 6 mm x I.D. 4 mm). We previously reported the Thermal Desorption Test Chamber method (TDC method) for quantifying SVOC of emissions from building materials and household electric appliances (Hoshino et al. 2002, 2003). In this study, we measured (qualitative and quantitative) VOC and SVOC emitted from automotive interior materials by the TDC method. RESEARCH METHODS The TDC method was composed of two measurement steps. First, a test piece of automotive interior material (50mm square) was put into a quartz chamber (inside dimensions: 100 mm bore x 50 mm high, 393mL vol) that was placed in the heating oven of the emission gas concentrating system MSTD258M-B (GL Sciences Inc.). Helium gas was supplied to the chamber, and the chamber was heated to the target temperature (65 C or 100 C). Emissions from the test piece were sampled with Tenax TA tubes with a pump (mainly VOC emissions). Second, the test piece was removed from the chamber. The empty chamber was heated to 250 C in a helium atmosphere in order to desorb the compounds adsorbed on the internal chamber surface (mainly SVOC emissions). Tenax TA tubes were used for sampling. After sampling, all tubes were analyzed by the thermal desorption auto-sampler (TD, GL Sciences Inc., TMD-253H) connected to gas chromatography/mass spectrometry equipment (GC/MS, Shimadzu QP2010). The system flows of the measurements are shown in Figure 1. Before these measurements, test pieces of automotive interior materials were stored in clean-air of approximately RH 50% and 20 C for about 48 h. Table 1 lists the automotive interior materials measured and Table 2 lists the measurement conditions. * Corresponding author email: hoshino@gls.co.jp 2231
First step measurement (mainly VOC sampling) Automotive interior material Heating oven Tenax TA tube Quartz chamber 50mL/min He 100mL/min Heated to 65 癈 or 100 癈 Sampling pump After sampling, Tenax TA tube was connected to a thermal desorption auto-sampler Remove the material from the chamber Second step measurement (mainly SVOC sampling) Desorb the compounds adsorbed on the internal chamber Heating oven Tenax TA tube Quartz chamber 50mL/min He 100mL/min Heated to 250 癈 Sampling pump After sampling, Tenax TA tube was connected to a thermal desorption auto-sampler Figure 1. The system flows of the measurements (the TDC method) Table 1. The automotive interior materials measured automotive interior materials PVC (Poly vinylchloride) instrument panel epidermis TPO (thermo plastic olefine) instrument panel epidermis Polyurethane used for instrument panel Weight (g) 2.143-81 2.693-2.897 3.339-4.475 When carrying out quantitative analysis of VOC and SVOC, calibration curves must be created in advance. The calibration curve for VOC measurement was analyzed by TD-GC/MS of a standard VOC mixture sample of Toluene, Ethylbenzene, o-, m-, p-xylene, Styrene, p-dichlorobenzene, Nonanal, and Tetradecane in a Tenax TA tube (100 to 5000 ng of each component) after dry purging with nitrogen for 5 min. To generate a calibration curve for measurement of SVOC, a standard SVOC mixture sample of Phthalate esters (DEP (Diethyl phthalate), (Dibutyl phthalate), DEHP (Di(2-ethylhexyl) phthalate), Adipate (DOA (Di(2-etyhlhexyl) adipate), Phosphoric esters (TBP (Tributyl Phosphate, TCEP (Tris(2-chloroethyl) phosphate), BHT (Butylated hydroxyltoluene), and D6(Dodecamethyl Cyclohexasiloxane), and a hydrocarbon mixture sample of Hexadecane and Eicosane were spiked into the chamber (100 to 2,500 ng of each component), and the chamber was heated to 250 C, after which sampling was carried out using a Tenax TA sampling tube, followed by analysis by TD-GC/MS. 2232
Table 2. Measurement conditions MSTD258M-B Chamber inside dimension φ100 譎 50mm Chamber volume 3.93? 0-4 m 3 (393ml) Supply gas to the chamber He, 100mL/min Sampling flow rate 50mL/min Sampling time and volume 40min, L Temperature Fist step measurement : 65 癈, 100 癈, Rate 5 癈 /min Second step measurement : 250 癈, Rate 20 癈 /min Sampling material Tenax TA 25/35mesh, 100mg exchange rate (n) 7.64/h Loading factor (L) 12.7m 2 /m 3 n/l 0.60 TMD253H (TD) Cold Trap Temp. -130 Desorption Temp. and Time 270, 14min QP2010 (GC/MS) Column Temperature Programming Scan mode TC-1 mmi.d.? 0m, df= 祄 40 (5min)-10 癈 /min-280 癈 (21min) m/z 35-450 RESULTS Figure 2 shows the total ion chromatogram () for measurement of VOC and SVOC emitted from the automotive interior materials at 65 C by TDC method. In first step measurement, Ethylbenzene, Xylene, Cyclohexanone, Styrene, Acetophenone, and BHT were confirmed from PVC (poly vinylchloride) instrument panel epidermis; Ethylbenzene, Xylene, p-ethylstyrene, 1-Hydroxy-1methyl -ethylacetophenone, and BHT were confirmed from TPO (thermo plastic olefine) instrument panel epidermis; and Triethyamine, Cyclohexanone, 2-(2-ethoxyethoxy) -ethanol, and BHT were confirmed from polyurethane used for instrument panel. In second step measurement, Dodecanol, Tridecanol, Tetradecanol, BHT, and were confirmed from PVC instrument panel epidermis; 1-Hydroxy-1 -methylethylacetophenone, and DEP were confirmed from TPO instrument panel epidermis; and Triethylenediamine, and were confirmed from urethane used for instrument panel. Table 3 lists emission rates (ER, µg/m2/h) of each of the automotive interior materials at 65 C. Total ER value of VOC and SVOC in the first step measurement was calculated as a toluene equivalent and Total ER value of VOC and SVOC in the second step measurement was calculated as a hexadecane equivalent. There was a high proportion of VOC emitted in the first step measurement. BHT was detected in both the first and second step measurements. was detected in the second step measurement. Figure 3 shows the for the measurement of VOC and SVOC emitted at 100 C by the TDC method. Table 4 lists ER of each of the automotive interior materials at 100 C. Each material was used after measurement at 65 C by the TDC method. In first step measurement, there was a significant increase in detection of VOC compounds and medium-boiling compounds before a retention time of 30 min compared to those at 65 C. In second step measurement, large amounts of SVOC (, DEHP, DOA) were detected and, DINP was also detected from PVC materials. 2233
1 (x1,000,000) PVC Fist step at 65 0 (x1,000,000) 1.75 TPO Fist step at 65 7.5 m- or p-xylene Cyclohexanone o-xylene Ethylbenzene C 7 H 16 O 2 Acetophenone Styrene BHT 1.50 0 Ethylstyrene 1-Hydroxy-1 -methylethylacetophenone o-xylene m- or p-xylene BHT + C 15 H 32 Ethylbenzene 0 0 (x1,000,000) (x1,000,000) PVC Second step at 65 TPO Second step at 65 1.75 1.50 C 7 H 16 O 2 1-Hydroxy-1 -methylethylacetophenone 0 0 Tridecanol Dodecanol Undecanol Decanol BHT ester compound Tetradecanol Pentadecanol (x1,000,000) 1.5 0.5 Polyurethane Fist step at 65 DEP Cyclohexanone Triethyamine 2-Ethyl-1-hexanol BHT + C 15 H 32 6.0 (x1,000,000) Polyurethane Second step at 65 Triethylenediamine Figure 2. for measurement of VOC and SVOC emitted from the automotive interior materials at 65 C by TDC method Table 3. ER (µg/m 2 /h) of each of the automotive interior materials at 65 C PVC TPO Polyurethane 1st Step 2nd Step 1st Step 2nd Step 1st Step 2nd Step Ethylbenzene 1566.8 < 6.0 49.0 N.D. 34.6 N.D. m or p-xylene 2667.5 19.4 140.2 N.D. 57.6 N.D. o-xylene 1810.6 < 6.0 141.2 N.D. 44.6 N.D. Styrene 296.8 < 6.0 < 6.0 N.D. 8.7 N.D. BHT 466.1 106.7 74.2 33.6 67.7 65.3 DEP N.D. N.D. N.D. 28.5 N.D. N.D. < 6.0 49.4 < 6.0 8.7 < 6.0 145.5 DOA N.D. N.D. N.D. N.D. N.D. N.D. DEHP N.D. < 6.0 N.D. < 6.0 N.D. N.D. Total VOC and SVOC 39,336 2,529 6,001 2,388 14,606 3,911 2234
1.50 (x10,000,000) Cyclohexanone PVC Fist step at 100 6.0 (x1,000,000) TPO Fist step at 100 0 m- or p-xylene Ethylbenzene o-xylene Dodecanol Acetophenone BHT Decanol Tridecanol Undecanol ester compound m- or p-xylene o-xylene Ethylstyrene BHT + C 15H 32 1-Hydroxy-1 -methylethylacetophenone Diacetylbenzene 0 0 (x1,000,000) 1.75 1.50 0 C 7 H 16 O 2 Cyclohexanone BHT Tridecanol Dodecanol Tetradecanol DOA PVC Second step at 100 DEHP DINP (x1,000,000) 1.5 0.5 1-Hydroxy-1 -methylethylacetophenone DEP TPO Second step at 100 DEHP 0 4 1 (x1,000,000) Polyurethane Fist step at 100 2-Ethyl-1-hexanol 7.5 2,2'-azobis-2-methyl-propnenitrile Cyclohexanone BHT + C 15H32 Triethyamine 6.0 (x1,000,000) Polyurethane Second step at 100 Triethylenediamine DOA Figure 3. for measurement of VOC and SVOC emitted from the automotive interior materials at 100 C by TDC method Table 4. ER (µg/m 2 /h) of each of the automotive interior materials at 100 C PVC TPO Polyurethane 1st Step 2nd Step 1st Step 2nd Step 1st Step 2nd Step Ethylbenzene 4146.5 47.2 76.6 N.D. 48.5 N.D. m or p-xylene 6717.9 88.2 218.2 N.D. 85.8 N.D. o-xylene 5597.6 66.9 257.4 N.D. 94.8 N.D. Styrene 392.3 < 6.0 7.4 N.D. 11.2 N.D. BHT 202 127.6 529.2 25.8 60 41.1 DEP N.D. N.D. 34.9 16.7 N.D. N.D. 66.4 85.8 10.2 18.9 164.6 240.3 DOA N.D. 114.7 N.D. N.D. N.D. 321.2 DEHP N.D. 317.3 N.D. 279.3 N.D. < 6.0 Total VOC and SVOC 166,143 4,034 30,225 3,971 91,657 4,586 2235
DISCUSSION This study confirmed the following: Most detected compounds in first step measurement were VOC compounds and medium-boiling compounds before a retention time of 30 min. DEHP, DINP and DOA used as plasticizers were only detected in second step measurement at 100 C. BHT, DEP and were detected in first and second step measurements. s were detected from urethane and TPO materials. Higher alcohol (Decanol, Undecanol, Tridecanol, Tetradecanol and Pentadecanol) were detected from PVC materials. Emission rates (ER, µg/m2/h) was calculated with the following equation (1): ER=C Q/A+Ad/(Q t) Q/A=(C+Ad/(Q t)) n/l (1) Where C (µg/m3) is the concentration of a compound, Q (m3/h) is flow rate of helium gas, A (m2) is the sample area, Ad (µg) is the amount of compound adsorbed on the internal chamber surface, t (h) is the sampling time, n (number of times/h) is the exchange rate, L (m2/m3) is the loading factor. Reportedly, organophosphate esters used as flame retardants are emitted from automotive interior materials (M. Wensing et al. 2003). But organophosphate esters were not detected in this experiment. In future, the authors will measure organophosphate esters emitted from materials by the TDC method. CONCLUSION AND IMPLICATIONS With regard to measurement of emissions from automotive interior materials, it is important to elucidate the behavior of high-boiling compounds such as SVOC emitted from materials. The results of the present study demonstrated the effectiveness of the TDC method. REFERENCES Hoshino K., Iwasaki T., Kato S. et al. 2002. Study on measurement of semi volatile organic compounds (SVOCs) emitted from indoor materials and products using glass test chamber, Proceedings of the 9th International Conference on Indoor Air Quality and Climate- Indoor Air 2002, Montrey: Indoor Air 2002, Vol.2, pp 950-954. Hoshino K., Ogawa S., Kato S. et al. 2003. Measurement of SVOCs emitted from building materials and electric appliances using thermal desorption test chamber method, Proceedings of the 7th International Conference on Healthy Buildings 2003, Vol.1, pp 474-479. Singapore: Healthy Buildings 2003. VDA276-1. 2000. Determination of organic emissions from automotive interiors with a 1-m3 test cabinet, Automotive Industry Association. VDA278 2001. Thermal desorption analysis of organic emissions for the characterization of non-metallic motor vehicle materials, Automotive Industry Association. Wensing M., Pardemann J., and Schwampe W.. 2003. Flame retardants in the indoor environment. Part V: Measurement and exposure evaluation of organophosphate esters from automobile interiors Proceedings of the 7th International Conference on Healthy Buildings 2003, Vol.1, pp 172-177. Singapore: Healthy Buildings 2003. 2236