Rubber extraction

Plasticiser/oil in rubber is usually determined by solvent extraction (ISO 1407) and FTIR identification [57] TGA can usually provide good quantifications of plasticiser contents. Antidegradants in rubber compounds may be determined by HS-GC-MS for volatile species (e.g. BHT, IPPD), but usually solvent extraction is required, followed by GC-MS, HPLC, UV or DP-MS analysis. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out. The determination of antioxidants in rubbers by means of HPLC and TLC has been reviewed [58], The TLC technique for antidegradants in rubbers is described in ASTM D 3156 and ISO 4645.2 (1984). Direct probe EIMS was also used to analyse antioxidants (hindered phenols and aromatic amines) in rubber extracts [59]. ISO 11089 (1997) deals with the determination of /V-phenyl-/9-naphthylamine and poly-2,2,4-trimethyl-1,2-dihydroquinoline (TMDQ) as well as other generic types of antiozonants such as IV-alkyl-AL-phenyl-p-phenylenediamines (e.g. IPPD and 6PPD) and A-aryl-AL-aryl-p-phenylenediamines (e.g. DPPD), by means of HPLC. 

Applications Open-column chromatography was used for polymer/additive analysis mainly in the 1950-1970 period (cf. Vimalasiri et al. [160]). Examples are the application of CC to styrene-butadiene copoly-mer/(additives, low-MW compounds) [530] and rubbers accelerators, antioxidants) [531]. Column chromatography of nine plasticisers in PVC with various elution solvents has been reported [44], as well as the separation of CHCI3 solvent extracts of PE/(BHT, Santonox R) on an alumina column [532]. Similarly, Santonox R and Ionol CP were easily separated using benzene and Topanol CA and dilaurylthiodipropionate using cyclohexane ethyl acetate (9 1 v/v) [533]. CC on neutral alumina has been used for the separation of antioxidants, accelerators and plasticisers in rubber extracts [534]. Column chromatography of polymer additives has been reviewed [160,375,376]. 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

In a study on the identification of organic additives in rubber vulcanisates using mass spectrometry, Lattimer et al. [22] used direct thermal desorption with three different ionisation methods El, Cl and FI. Also, rubber extracts were examinated directly by four ionisation methods (El, Cl, FD and FAB). The authors did not report a clear advantage for direct analysis as compared to analysis after extraction. Direct analysis was a little faster, but the extraction methods were considered to be more versatile. 

An effective means to facilitate the mass-spectral analysis of rubber acetone extracts is to use desorp-tion/ionisation techniques, such as FD [92,113] and FAB [92]. FAB mass spectra for rubber extracts are generally more complex (due to fragment ions) than FD spectra of the same materials. Nevertheless, the FAB spectra are often complementary to FD, since ... 

In an acetone extract from a neoprene/SBR hose compound, Lattimer et al. [92] distinguished dioctylph-thalate (m/z 390), di(r-octyl)diphenylamine (m/z 393), 1,3,5-tris(3,5-di-f-butyl-4-hydroxybenzyl)-isocyanurate m/z 783), hydrocarbon oil and a paraffin wax (numerous molecular ions in the m/z range of 200-500) by means of FD-MS. Since cross-linked rubbers are insoluble, more complex extraction procedures must be carried out (Chapter 2). The method of Dinsmore and Smith [257], or a modification thereof, is normally used. Mass spectrometry (and other analytical techniques) is then used to characterise the various rubber fractions. The mass-spectral identification of numerous antioxidants (hindered phenols and aromatic amines, e.g. phenyl-/ -naphthyl-amine, 6-dodecyl-2,2,4-trimethyl-l,2-dihydroquinoline, butylated bisphenol-A, HPPD, poly-TMDQ, di-(t-octyl)diphenylamine) in rubber extracts by means of direct probe EI-MS with programmed heating, has been reported [252]. The main problem reported consisted of the numerous ions arising from hydrocarbon oil in the recipe. In older work, mass spectrometry has been used to qualitatively identify volatile AOs in sheet samples of SBR and rubber-type vulcanisates after extraction of the polymer with acetone [51,246]. 

The surface area of a filler per cubic centimetre coming into interfacial contact with the rubber. Extraction... 

Tabun Petrol additives, hydraulic fluids, insecticides, flame retardants, pharmaceuticals, detergents, pesticides, missile fuels, vulcanisation of rubber, extraction of gold and silver from ores. 

An ultraviolet (UV) spectrum of an aqueous rubber extract identifies and quantifies the antioxidants, curing agents, accelerators, and other UV-absorbing species extracted from the compound. 

This guideline advocates more information on rubber extractables and the proper use of DMFs. 

Use Manufacture of nylon solvent for cellulose ethers, fats, oils, waxes, bitumens, resins, crude rubber extracting essential oils chemicals (organic synthesis, recrystallizing medium) paint and varnish remover glass substitutes solid fuels fungicides analytical chemistry. 

The polymers which will be studied in this book are synthetic polymers and the industrial importance of such materials is well-known. However, we must recall that there also exist numerous natural polymers, and some of these have a great biological importance. Among the most common ones, we may cite natural rubber extracted from hevea latex and cellulose, with its derivatives, extracted from wood. 

Rubber extracted from the tree, Hevea brasiliensis. 

Lattimer and coworkers have published several reports on polymer compound analysis by mass spectrometry. " In earlier studies, the emphasis was on field desorption analysis of rubber extracts. A typical example is shown in Figure 6.14, which is the FD mass spectrum of the acetone extract from an EPDM vulcanizate. The spectrum shows the presence of several ingredients phenyl-)3-napthylamine antioxidant (MW 219), fatty acid (MW 256, 282, 284), dioctylphthalate plasticizer (MW 390), and a paraffin wax (MW 324, 338, et al.). 

Higlily iiiastic.iied pale crepe rubber extracted by acetone. ... 

Hayes and Altenau [34] were the first to report the use of MS to directly characterise antioxidants and processing oil additives in synthetic rubbers. Since then, various MS techniques have been applied to the analysis of rubber and polymer additives either as extracts or on the sample surface by laser techniques as reviewed by Lattimer and Harris [35]. Lattimer reviewed the present situation regarding MS in polymer analysis [36]. Analysis of polymer extracts by MS has proved challenging. Electron impact mass spectra (EI-MS) are often difficult to interpret due to the high concentration of processing oils and the additives in the extract, and excessive fragmentation of the molecular ions. Desorption/ionisation techniques such as field desorption (ED) and fast atom bombardment (FAB) have been found to be the most effective means for analysing polymer and rubber extracts [37, 38]. 

Rubber extracts were examined directly by the four ionisation methods. Of the vaporisation/ionisation methods, it appears that field ionisation is the most efficient for identifying typical organic additives in rubber vulcanisates. 

Fiorenza and co-workers [50] have described a technique based on column chromatography on neutral alumina for the separation of antioxidants, plasticisers, and so on, in rubber extracts (Figure 3.8). They detected the separated compounds by monitoring the effluent with a LKB 254 nm UV detector (Figure 3.9). In this procedure a carbon tetrachloride solution of the sample is applied to an alumina column wetted with the same solvent and the column is successively eluted with carbon tetrachloride, mixtures of carbon tetrachloride and benzene, benzene, mixtures of benzene and absolute ethanol, and finally, ethanol. Separations were carried out on a scale to provide enough of each separated compound for the preparation of IR and UV spectra. 

Figure 3.8 Column chromatography on alumina of antioxidants, accelerators and plasticisers in rubber extracts and UV spectra of separated compounds Reproduced from Fiorenza and co-workers, Materie Plastiche ed Elastomerie [50]...

This technique has found limited applications in polymer additive analysis in plastics and rubbers. These include aromatic amines and antiozonants in rubber extracts [2, 50-62], and di-laurylthiodipropionate in polymer extracts [56]. 

Wheeler [1] has reviewed the available literature on the applications of paper chromatography in the examination of polymers for antioxidants (Table 6.1). He points out that, as most antioxidants are highly polar, they cannot be efficiently separated on normal paper except by the use of highly polar mobile phases. Consequently reversed-paper chromatography [2-5] or acetylated papers [6-9] have been used to reduce the effects of tailing . Various workers have discussed the determination of antioxidants in rubber extracts [10-14]. 

Lattimer and co-workers [25] have applied mass spectrometry (MS) to the determination of antioxidants and antiozonants in rubber vulcanisates. Direct thermal desorption was used with three different ionisation methods [electron impact (El), chemical ionisation (Cl), field ionisation (FI)]. The vulcanisates were also examined by direct fast atom bombardment mass spectrometry (FAB-MS) as a means for surface desorption/ionisation. Rubber extracts were examined directly by these four ionisation methods. Of the various vaporisation/ionisation methods, it appears that field ionisation is the most efficient for identifying organic additives in the rubber vulcanisates. Other ionisation methods may be required, however, for detection of specific types of additives. There was no clear advantage for direct analysis as compared to extract analysis. Antiozonants examined include aromatic amines and a hindered bisphenol. These compounds could be identified quite readily by either extraction or direct analysis and by use of any vaporisation/ionisation method. 

To estimate the properties of ozonizated Indian rubber in the rubber compound a sample of 0.4 kg mass was obtained with ozonization degree of 0.8 mass % (sample 6 in Table 13.1). This sample was used for the preparation of the rubber compoimd according to the standard formulation approved in tire production. Rubber compound prepared on the basis of the rubber extracted from the sample of original latex that was preliminarily plasticized with the use of cold rolling mills with the gap of 2 mm for 3 min was applied as the reference sample. The choice of plasticization time was connected with the necessity of decrease of the rubber molecular mass up to the value of that one obtained from the ozonizated latex. 

FIG. 18 FTIR spectra of rubbers extracted from (a) PBTDBS9 (b) PBTESI0.5 (c) PBTTEPR. 

Protivova and Pospisil have reported on the behaviour of some amine antioxidants and antiozonants and some model substances (phenols, aromatic hydrocarbons and amines) during gel permeation chromatography and have applied this technique (method 47) to the analysis of rubber extracts. 

---