Residual Styrene Monomer Research Articles

Assessment of residual styrene monomer migration into yoghurt packed in High Impact Polystyrene pots using a modelling approach

Assessment of residual styrene monomer migration into yoghurt packed in High Impact Polystyrene pots using a modelling approach

Comparison of residual styrene monomer determination of pharmaceutical materials packed with polystyrene using gas chromatography and ultraviolet/visible spectrophotometer

Background: Plastics such as plastic wrapping are an integral part of today’s society. Plastics are made by polymerization of styrene monomers. If the polymerization reaction is not perfect, then there will be unreacted monomer residues. Although styrene is still considered harmless, if there is a metabolic process will form styrene oxide that can cause effects that are carcinogenic. Aims and Objectives: This study aims to determine the residue of pharmaceutical styrene materials packed with polystyrene using gas chromatography (GC) and ultraviolet (UV)/visible spectrophotometers which are usually available in chemical analysis laboratories. Materials and Methods: Orientation of analysis method was performed using latex polystyrene sample. Styrene monomer analysis was performed using a GC and UV/visible spectrophotometer. Then a comparative study was conducted on both methods. Once this method was accepted, it was applied to a polystyrene-containing sample obtained from the market. Styrene was isolated from the sample; then, both methods were tested and compared. Results: Using polystyrene latex sample and varying column temperature, for GC, the optimum condition was obtained at column temperature 110°C, detector temperature 200°C, and temperature of injector 200°C. Using the packing column, we got a repeatability of 96.67%, PRECISION test of 2.81%, 96.49% recovery test, and a detection limit of 0.25 ppm. For the quantitative test of latex polystyrene samples, the average residual content obtained was 0.276%. When using GC with a capillary column, used column DB-17 at 110°C, detector, and injector temperature at 200°C, the average content of styrene residue was 0.278%. When using the spectrophotometer UV/visible, λ maximum at 280.5 nm, the reliability, assay, recovery test, and detection limits were 94.83%, 4.36%, 93.72% and 0.30 ppm, respectively. The residual styrene results obtained with this instrument was an average of 0.271%. Using variance analysis with the fixed model for all three methods (GC with the capillary column, GC with packing column, and spectrophotometer UV/visible) obtained H0 hypothesis was rejected so that it was continued with Duncan test with the result of all three methods could be used for analysis of styrene residue. The result of average analysis for beverage sample with Spectrophotometer UV/visible method was 0.0220%, packed column GC was 0.0221% packing, and capillary column GC of 0.0.223%. For medication samples in each instruments were found 0.0239%, 0.0241%, and 0.0242%, whereas for food samples obtained 0.0236%, 0.0238%, and 0.0239%. Conclusions: A GC method with either a packing column or a capillary column and a spectrophotometer UV/visible could be used to analyze the residual styrene monomer of a polystyrene-grade pharmaceutical sample. The best analysis could use GC with a capillary column. It is recommended to use differential scanning calorimetry and thermogravimetric analysis, if available, as well as infrared spectrophotometer to obtain a cheaper and better method.

Nucleation of gold nanoparticles on latex particle surfaces

AbstractGold particles were nucleated on functionalized (i.e., sulfonate or imidazole groups) latex particle surfaces. Gold ions were associated with the functional groups present on the surface of the latex particles by metal‐ligand formation and were then reduced to nucleate gold particles on the particle surface. The use of imidazole groups favored the metal‐ligand formation more effectively compared with sulfonic acid groups, so gold nucleation was investigated on the surface of imidazole‐functionalized model latex particles. The desorption of gold atoms or their surface migration first occurred during the reduction process and then gold nanoparticles were nucleated. The utilization of strong reductants, such as NaBH4 and dimethylamine borane (DMAB) under mildly acidic conditions (i.e., pH 4) led to the deprotonation of imidazole‐rich polymer chains present on the surface of the model latex particles followed by deswelling of hydrophilic polymer surface layers. As a result, well‐dispersed gold nanoparticles were embedded in the hydrophilic polymer surface. On the other hand, the use of weak reductants led to the formation of localized gold aggregates on the surface of the latex particles. The removal of residual styrene monomer is very important because gold ions can be coordinated with the vinyl groups present in styrene monomer and would then be reduced by nucleophilic water addition. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 912–925, 2008

Determination of residual styrene monomer in polystyrene granules by gas chromatography–mass spectrometry

Polystyrene is widely used in formulations intended for children use. The main problem with this plastic is the residual styrene, which can migrate from the product, and therefore, be in contact with children. The acute toxicity of styrene is well known, raising the need of an efficient and fast method of analysis for this compound. Several extraction methods have been evaluated and compared for the determination of residual styrene monomer in polystyrene granules used in toys: supercritical fluid extraction (SFE), microwave-assisted extraction (MAE), Soxhlet extraction, headspace emission and dissolution-precipitation. The analyte was subsequently detected by gas chromatography (GC) with MS detection. The results indicated that the most efficient method was dissolution-precipitation giving even higher extraction efficiency than SFE. For validating the method, PS samples spiked with known quantities of styrene at three concentration levels were prepared to calculate the extraction recovery. The founded validation data proved the suitability of the proposed method.

Analysis of residual styrene monomer and other volatile organic compounds in expanded polystyrene by headspace solid-phase microextraction followed by gas chromatography and gas chromatography/mass spectrometry

A method for determination of residual styrene monomer and other volatile organic compounds in expanded polystyrene (EPS) was developed using HS SPME and gas chromatography with FID. The extraction products were identified by GC/MS. Good reproducibility of the measurements with RSD values between 3.2–3.6% was achieved by extraction using a 75 μm Carboxen-Polydimethylsiloxane fiber at 60°C with 15 min sample sonication. The contents of residual styrene monomer in two samples of EPS were 153.2 and 65.7 mg/kg, respectively. Other compounds identified in EPS were pentane, benzene, toluene, ethylbenzene, isomers of xylene, n-propylbenzene, 1,2,4-trimethylbenzene, o-methylstyrene, benzaldehyde, benzyl alcohol, and acetophenone.

Catalytic reduction of residual styrene monomer in polystyrene

Styrene monomer has a low taste and odor threshold, and its presence in the polystyrene used in food packaging applications must be as low as possible. Conventional devolatilization technology does not lower styrene contents to desired levels, so special costly devolatilization techniques have to be used. Attempts to employ scavengers for styrene to reduce residual monomer levels have been largely unsuccessful. This article evaluates the possibility that strong acids can be used to induce residual styrene to alkylate styrene units in polystyrene by Friedel–Crafts reactions. The results of studies evaluating this approach indicate its feasibility, but colored products are obtained when sulfonic acids are used and prohibitively high levels of acids must be used to be effective. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1786–1791, 2002

Polystyrene sheet composition and temperature as parameters for migration of styrene monomer into corn oil

AbstractDifferent types of polystyrene used in packaging were tested for styrene monomer migration into corn oil. Several blends of general‐purpose polystyrene with different amounts of high‐impact polystyrene demonstrated a linear increase of migration of styrene with increasing amount of high‐impact polystyrene in the polymer. Faster migration was found for higher exposure temperatures. Migration depended linearly on the content of residual styrene monomer in the polymer.

Styrene monomer migration as monitored by purge and trap gas chromatography and sensory analysis for polystyrene containers

ABSTRACTA plastic‐like off‐flavor in food packaged in multilayered polystyrene containers was determined to be predominately caused by residual styrene monomer, in conjunction with ethylbenzene, that had diffused into the food product. Purge and trap gas chromatography was used to measure μg/L (ppb) concentrations of styrene monomer that migrated from containers over time. The flavor panel used in this study was able to detect the presence of styrene in apple juice at a concentration of 50 μg/L. A mixture of styrene and ethylbenzene was found to lower the concentration at which an off‐flavor could be detected to 25 μg/L. Deionized water stored in containers at various temperatures was analyzed for styrene and ethylbenzene by purge and trap gas chromatography, and the initial data fitted a simple diffusion model showing that styrene pickup was proportional to the square root of time.

Residual styrene monomer in Chilean foods by headspace gas chromatography.

Dosage des residus de styrene monomere dans les aliments et dans les emballages de polystyrene. Etude des variations de ces taux en fonction du temps de conservation dans les emballages plastiques (migration du styrene)

Diels‐Alder reaction of a trace amount of styrene with cyclopentadiene in a liquid phase

AbstractWith the intention to prove the possibility of applying the Diels‐Alder reaction to trap a trace amount of residual styrene monomer in polystyrene, a model reaction between cyclopentadiene with styrene in a dilute o‐chlorobenzene solution was carried out. In the presence of an excess amount of dicyclopentadiene, the consumption of styrene was measured with time lapse by means of gaschromatography. At temperatures ranging from 140 to 220°C, the amount of styrene was observed to decrease remarkably until it reached an equilibrium concentration. The higher the temperature was, the higher the equilibrium concentration became. The equilibrium constants at each temperature and the activation energy for the reaction were calculated.

Copolymerization of styrene with acrylamide in an emulsifier‐free aqueous medium

AbstractCopolymerization of styrene with acrylamide was carried out in an emulsifier‐free aqueous medium. The resulting latex contained an appreciable amount of acrylamide‐rich copolymer in the serum. The copolymerization course was divided into three stages on the basis of the main reaction locus. At first, acrylamide polymerized in preference to styrene in the aqueous phase. Water‐soluble growing radicals lost hydrophilicity rapidly and nucleated the particles. After particle formation, styrene polymerized exclusively in the particles until styrene droplets disappeared. The decrease in the concentration of residual styrene monomer caused growing radicals to keep the hydrophilicity for a long time, and polymerization of acrylamide was accelerated in the aqueous phase. Polymerizations at higher temperature and lower pH resulted in prolongation of the first stage of the polymerization, that is, preferential polymerization of acrylamide in the aqueous phase. An increase in the acrylamide fraction in monomer feed caused some decreases in the particle size and its uniformity.

The influence of residual styrene monomer, benzaldehyde, and microbial activity on the surface properties of polystyrene latices

AbstractThe influence of residual styrene monomer and benzaldehyde on the surface properties of polystyrene latices has been considered. These materials are commonly found after emulsion polymerisation and their complete removal by dialysis is almost impossible. Steam stripping at reduced pressure (nitrogen atmosphere, < 350K) can be used to remove the last traces of styrene and benzaldehyde from polystyrene, but this process results in some degree of hydrolysis of the surface sulphate groups.Latices are easily contaminated by microorganisms, especially those which are airborne. This can occur during cleaning and/or storage. Microorganisms can survive and multiply in suitable latex environments and can result in the destabilisation and subsequent flocculation of the latex. Controlled experiments with a latex dosed with various levels of a penicillium type fungus demonstrated the possibility that enzymes (classified as aryl sulphate sulphohydrolases ‐ E. C. 3.1.6.1.) were produced which resulted in the rapid hydrolysis of surface sulphate groups. Fungal growth was accompanied by the release of weak acids and metabolites which were titrated in the aqueous phase.Careful consideration should be given to the conditions of latex preparation, cleaning and storage, e.g. use of autoclaved water and γ‐irradiation techniques, which will reduce the possibility of microbial contamination. Routine tests for bacteria and fungi should be carried out by plating on microbiological media, since the usual tests for protein such as the Folin‐Ciocalteu are insensitive at the low levels of contamination which may be present.

Effects of post‐curing of unsaturated polyester resins in various media

AbstractExperimental studies were performed on the effects of postcuring of' styrenated, unsaturated polyesters in nitrogen gas, water or its vapor, hexane vapor, dimethyl sulfoxide (DMSO), and dirnethyl formamide (DMF) all at 100°C It was found that, nitrogen gas and water are inactive, hexane acts as a chain transfer agent, and DMF and DMSO behave as solvents which extract residual styrene monomer and anhydrides from the resins. Post‐treatment in inert media can result in further reaction leading to more complete cure as free radicals and residual monomer continue to react. The post‐curing reaction is a radical copolymerization. Further condepgation polymerisation does not occur. Post‐curing in, hexane vapor1eads to a transfer of the active sites from the radicals to the hexane and to no further radical polymerization.

Energy Transfer and Quenching in Plastic Scintillators

Abstract Luminescence quenching in polystyrene + 9,10-diphenylanthracene + quencher and polystyrene + quencher systems has been investigated. In the latter system, the residual styrene monomer is regarded as a fluorescent solute. Result show that solvent quenching observed under uv excitation is due mainly to the competition between dipole-dipole energy transfer from polystyrene to the fluor and that from polystyrene to the quencher, and that such a transfer occurs directly from an excited polystyrene segment before it forms an excimer with an unexcited segment. Solvent quenching under beta-ray excitation was generally greater than that under uv excitation. It is suggested that this phenomenon may result from the occurrence of energy transfer at higher excited state of polystyrene. Solute quenching in some series of polystyrene + 9,10-diphenylanthracene + quencher is not accounted for by usual mechanisms of quenching. Such quenching can be explained by assuming energy transfer from the singlet excited state of 9,10-diphenylanthracene to the triplet state of the quencher.

Influence du mode de préparation sur le rendement lumineux des scintillateurs plastiques à base de polystyroléne

The effect of polymerization time on the luminescent yield of plastic scintillators and several monomer purification techniques are examined. The amount of residual styrene monomer and its effect on the scintillator's fluorescence spectra have been studied.

Effect of Styrene Monomer on the Fluorescence Properties of Polystyrene

Fluorescence spectra and lifetimes have been studied for polystyrene samples having different average molecular weights and different concentrations of residual styrene monomer. The residual styrene monomer is fluorescent and acts as a typical fluorescent solute in a rigid medium. The fluorescence properties of polystyrene were found to be dependent on both the concentration of residual styrene monomer and, to a lesser extent, the average molecular weight.

Determination of residual styrene (monomer) and acetophenone in polymer latices

AbstractA rapid, quantitative, direct procedure for the determination of monomeric styrene in a styrene‐based polymer emulsion has been developed. The method includes the extraction of styrene in cyclohexane and a subsequent measurement of the ultraviolet absorbance of the solution. Determination of, and compensation for interference from, acetophenone is also described. The range of 0–5% monomeric styrene was studied by statistical methods.

A Spectrophotometric Method for Residual Styrene in SBR Latex

Abstract The spectrophotometric method of analysis for residual styrene monomer in SBR latex has several advantages. No standardization of reagents is required. The method is rapid, accurate, and precise. The direct ultraviolet absorption method is applicable only in absence of interferences. The alternate distillation-ultraviolet method is applicable even in the presence of most interferences.

On the measurement of polymerization rates by means of infrared absorption spectra

AbstractMeasurements have been made of the rate of thermal polymerization of styrene by observation of the infrared absorption spectrum of polymerizing samples in infrared absorption cells at 100°C. No effect of cell thickness on polymerization rate was noted, and the rate obtained agrees well with previously published values. An infrared method for determination of residual styrene monomer in polystyrene is described, and its possible application to rate studies on systems at high per cent conversion is noted.