The rapid determination of volatile fatty acid number in para rubber latex using fourier transform-near infrared spectroscopy based on quantification and discrimination model
Abstract:Volatile Fatty Acid number (VFA no.) is one of the parameters indicating the state of quality of Para rubber latex at that particular time. Most factories analyze this parameter using standard analytical method as in ISO 506:1992(E). Nevertheless, this procedure is complicated, chemical and time consuming, as well as skilled analyst required. Therefore, near infrared (NIR) spectroscopy which is rapid, accurate and nonchemicals method was applied to determine the VFA no. in¯eld latex and concentrated latex base… Show more
“…13,14 They are components of the isoprene unit of rubber. 9,11 Based on the established data from Workman and Weyer, 17 the obvious peaks at about 5823 cm −1 (1717 nm) was due to functional group C–H methylene for hydrocarbons, 5230 cm −1 (1912 nm) due to P–OH phosphate (.P–OH) for phosphate, 4613 cm −1 (2168 nm) due to CONH 2 for proteins and 4335 cm −1 (2307 nm) due to C–H methylene associated with linear aliphatic hydrocarbon. Figure 2.(a) Raw PV spectra, (b) thin film spectra and (c) thick film spectra.…”
Section: Resultsmentioning
confidence: 99%
“…9 and Hock and Sirisomboon 10 used this technique to evaluate the dry rubber content of latex. Narongwongwattana et al., 11 Sirisomboon et al. 12 and Narongwongwattana et al.…”
Section: Introductionmentioning
confidence: 97%
“…Sirisomboon et al 9 and Hock and Sirisomboon 10 used this technique to evaluate the dry rubber content of latex. Narongwongwattana et al, 11 Sirisomboon et al 12 and Narongwongwattana et al 13 were equally successful in using NIR spectroscopy to determine the volatile fatty acid number, apparent viscosity and alkalinity of latices, respectively. TS or equilibrium swelling of a vulcanized rubber in a solvent is dependent on the density of the crosslinks, the nature of the solvent and the rubber.…”
Toluene swell or equilibrium swelling is universally used by rubber factories to measure the degree of crosslink of their compounded or prevulcanized latices at different stages of production. To apply near infrared spectroscopy for rapid and accurate quality control, spectral acquisition of prevulcanized latex, thin film and thick film was performed using a Fourier transform near infrared spectrometer in diffuse reflection mode across the wavenumber range of 12,500-3600 cm À1. For prevulcanized latex an effective model was developed using partial least squares regression with preprocessing (first derivative þ straight line subtraction method). The coefficient of determination (r 2), root mean square error of cross validation and bias of the validation set were 0.71, 3.93% and À0.005%, respectively. For the thin film model the r 2 , root mean square error of cross validation and bias were 0.65, 4.01% and À0.028%, respectively. Whereas for the thick film model the r 2 , root mean square error of cross validation and bias were 0.70, 4.00% and À0.006%, respectively. Three models including prevulcanized latex, thin film and thick film were validated by 23 unknown samples, providing standard error of prediction and bias of 5.357 and 2.494, 4.565 and 1.001 and 3.641 and À0.961%, respectively, for prevulcanized latex, thin film and thick film. The model developed for the thick film spectra gave the best results.
“…13,14 They are components of the isoprene unit of rubber. 9,11 Based on the established data from Workman and Weyer, 17 the obvious peaks at about 5823 cm −1 (1717 nm) was due to functional group C–H methylene for hydrocarbons, 5230 cm −1 (1912 nm) due to P–OH phosphate (.P–OH) for phosphate, 4613 cm −1 (2168 nm) due to CONH 2 for proteins and 4335 cm −1 (2307 nm) due to C–H methylene associated with linear aliphatic hydrocarbon. Figure 2.(a) Raw PV spectra, (b) thin film spectra and (c) thick film spectra.…”
Section: Resultsmentioning
confidence: 99%
“…9 and Hock and Sirisomboon 10 used this technique to evaluate the dry rubber content of latex. Narongwongwattana et al., 11 Sirisomboon et al. 12 and Narongwongwattana et al.…”
Section: Introductionmentioning
confidence: 97%
“…Sirisomboon et al 9 and Hock and Sirisomboon 10 used this technique to evaluate the dry rubber content of latex. Narongwongwattana et al, 11 Sirisomboon et al 12 and Narongwongwattana et al 13 were equally successful in using NIR spectroscopy to determine the volatile fatty acid number, apparent viscosity and alkalinity of latices, respectively. TS or equilibrium swelling of a vulcanized rubber in a solvent is dependent on the density of the crosslinks, the nature of the solvent and the rubber.…”
Toluene swell or equilibrium swelling is universally used by rubber factories to measure the degree of crosslink of their compounded or prevulcanized latices at different stages of production. To apply near infrared spectroscopy for rapid and accurate quality control, spectral acquisition of prevulcanized latex, thin film and thick film was performed using a Fourier transform near infrared spectrometer in diffuse reflection mode across the wavenumber range of 12,500-3600 cm À1. For prevulcanized latex an effective model was developed using partial least squares regression with preprocessing (first derivative þ straight line subtraction method). The coefficient of determination (r 2), root mean square error of cross validation and bias of the validation set were 0.71, 3.93% and À0.005%, respectively. For the thin film model the r 2 , root mean square error of cross validation and bias were 0.65, 4.01% and À0.028%, respectively. Whereas for the thick film model the r 2 , root mean square error of cross validation and bias were 0.70, 4.00% and À0.006%, respectively. Three models including prevulcanized latex, thin film and thick film were validated by 23 unknown samples, providing standard error of prediction and bias of 5.357 and 2.494, 4.565 and 1.001 and 3.641 and À0.961%, respectively, for prevulcanized latex, thin film and thick film. The model developed for the thick film spectra gave the best results.
“…Narongwongwattana et al [25] reported that most factories analysed VFA number by the method in ISO 506:1992(E). However, the procedure was complicated, time and chemical consuming and also skilled technician required.…”
The parameters including physico-chemical properties such as dry rubber content (DRC), total solids content (TSC), volatile fatty acid (VFA) number, alkalinity (ammonia content) and potassium hydroxide (KOH) number and physical properties such as viscosity and cross-link density are important to the trading and processing of natural rubber latex and its products. Traditionally these properties of field and concentrated latices and their products including thin and thick films are evaluated with chemicals and time-consuming methods and with the need of technical experts. The near-infrared (NIR) spectroscopy is a nondestructive, rapid, accurate and environment-friendly technique. It needs no chemical. This chapter describes the application of NIR spectroscopy on evaluation of the properties of natural rubber latex and its products.
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