Styrene Concentration Research Articles

Effect of loading types on performance characteristics of a trickle-bed bioreactor and biofilter during styrene/acetone vapor biofiltration

ABSTRACTA 2:1 (w/w) mixture of styrene (STY) and acetone (AC) was subjected to lab-scale biofiltration under varied loading in both a trickle bed reactor (TBR) and biofilter (BF) to investigate substrate interactions and determine the limits of biofiltration efficiency of typical binary air pollutant mixtures containing both hydrophobic and polar components. A comparison of the STY/AC mixture degradation in the TBR and BF revealed higher pollutant removal efficiencies and degradation rates in the TBR, with the pollutant concentrations increasing up to the overloading limit. The maximum styrene degradation rates were 12 and 8 gc m−3 h−1 for the TBR and BF, respectively. However, the order of performance switched in favor of the BF when the loading was conducted by increasing air flow rate while keeping the inlet styrene concentration (Cin) constant in contrast to loading by increasing Cin. This switch may be due to a drastic difference in the effective surface area between these two reactors, so the biofilter becomes the reactor of choice when the rate-limiting step switches from biochemical processes to mass transfer by changing the loading mode. The presence of acetone in the mixture decreased the efficiency of styrene degradation and its degradation rate at high loadings. When the overloading was lifted by lowering the pollutant inlet concentrations, short-term back-stripping of both substrates in both reactors into the outlet air was observed, with a subsequent gradual recovery taking several hours and days in the BF and TBR, respectively. Removal of excess biomass from the TBR significantly improved the reactor performance. Identification of the cultivable strains, which was performed on Day 763 of continuous operation, showed the presence of 7 G− bacteria, 2 G+ bacteria and 4 fungi. Flies and larvae of Lycoriella nigripes survived half a year of the biofilter operation by feeding on the biofilm resulting in the maintenance of a nearly constant pressure drop.

Studies on the Simultaneous Formation of Aroma-Active and Toxicologically Relevant Vinyl Aromatics from Free Phenolic Acids during Wheat Beer Brewing.

During the brewing process of wheat beer, the desired aroma-active vinyl aromatics 2-methoxy-4-vinylphenol and 4-vinylphenol as well as the undesired and toxicologically relevant styrene are formed from their respective precursors, free ferulic acid, p-coumaric acid, and cinnamic acid, deriving from the malts. Analysis of eight commercial wheat beers revealed high concentrations of 2-methoxy-4-vinylphenol and 4-vinylphenol always in parallel with high concentrations of styrene or low concentrations of the odorants in parallel with low styrene concentrations, suggesting a similar pathway. To better understand the formation of these vinyl aromatics, each process step of wheat beer brewing and the use of different strains of Saccharomyces cerevisiae were evaluated. During wort boiling, only a moderate decarboxylation of free phenolic acids and formation of desired and undesired vinyl aromatics were monitored due to the thermal treatment. In contrast, this reaction mainly occurred enzymatically catalyzed during fermentation with S. cerevisiae strain W68 with normal Pof(+) activity (phenolic off-flavor) resulting in a wheat beer eliciting the typical aroma requested by consumers due to high concentrations of 2-methoxy-4-vinylphenol (1790 μg/L) and 4-vinylphenol (937 μg/L). Unfortunately, also a high concentration of undesired styrene (28.3 μg/L) was observed. Using a special S. cerevisiae strain without Pof(+) activity resulted in a significant styrene reduction (<LoQ), but also in low amounts of 2-methoxy-4-vinylphenol (158 μg/L) and 4-vinylphenol (46.7 μg/L), resulting in a less pronounced wheat beer aroma.

Spatial analysis of volatile organic compounds in South Philadelphia using passive samplers

ABSTRACTSelect volatile organic compounds (VOCs) were measured in the vicinity of a petroleum refinery and related operations in South Philadelphia, Pennsylvania, USA, using passive air sampling and laboratory analysis methods. Two-week, time-integrated samplers were deployed at 17 sites, which were aggregated into five site groups of varying distances from the refinery. Benzene, toluene, ethylbenzene, and xylene isomers (BTEX) and styrene concentrations were higher near the refinery’s fenceline than for groups at the refinery’s south edge, mid-distance, and farther removed locations. The near fenceline group was significantly higher than the refinery’s north edge group for benzene and toluene but not for ethylbenzene or xylene isomers; styrene was lower at the near fenceline group versus the north edge group. For BTEX and styrene, the magnitude of estimated differences generally increased when proceeding through groups ever farther away from the petroleum refining. Perchloroethylene results were not suggestive of an influence from refining. These results suggest that emissions from the refinery complex contribute to higher concentrations of BTEX species and styrene in the vicinity of the plant, with this influence declining as distance from the petroleum refining increases.Implications: Passive sampling methodology for VOCs as discussed here is employed in recently enacted U.S. Environmental Protection Agency Methods 325A/B for determination of benzene concentrations at refinery fenceline locations. Spatial gradients of VOC concentration near the refinery fenceline were discerned in an area containing traffic and other VOC-related sources. Though limited, these findings can be useful in application of the method at such facilities to ascertain source influence.

Impacts of nickel supported on different zeolites on waste tire-derived oil and formation of some petrochemicals

Waste tire-derived oils commonly contain the considerable valuable aromatics such as benzene, toluene, ethylbenzene, toluene, xylenes and etc., but they also contain a significantly-high amount of sulfur compounds, which cause a low quality of pyrolytic oil. Ni is a cheap metal, which exhibits hydrogenation/dehydrogenation and ring-opening like a noble metal, and widely used as promoter in desulfurization of fuels. In this work, Ni was expected to be a catalyst promoter of zeolites for reduction of sulfur content in oil and enhancement of petrochemical formation in oil. Therefore, the effect of 5wt.% nickel loading on different four type zeolites (HZSM-5, HMOR, HY, HBETA) on the sulfur removal and quality of waste-tire derived oil was studied. The results show that the incorporations of nickel on all zeolites significantly reduced sulfur contents in oil. However, the quality of waste tire-derived oil did not only depend on the nickel promoter, but also strongly depended on zeolite supports. The introduction of nickel on HZSM-5 zeolite, which possesses a smaller pore size than HBETA zeolites, provided a lighter oil with higher proportion of gasoline and kerosene than Ni/HBETA catalyst, and produced a higher amounts of valuable aromatic such as ethylbenzene, toluene, cumene, and mixed-xylenes than Ni/HBETA catalyst. Moreover, the addition of nickel on HMOR zeolite, which possesses a 1D zeolite channel structure, also provided a lighter oil with a high proportion of gasoline and kerosene than the Ni-loaded on HBETA (3D zeolite channel structure), and exhibited a better petrochemical production with a higher concentrations of ethylbenzene, toluene, cumene and styrene in maltene. On the other hand, Ni/HBETA provided the lower sulfur content in oil than Ni/HMOR catalyst, but the sulfur removal ability by nickel species on HMOR was higher than nickel species on HBETA zeolite. Furthermore, the introduction of nickel on HY zeolite provided the heavier oil with higher proportion of gas oil, LVGO and HVGO and lower proportion of petrochemical than Ni/HBETA zeolite whereas the sulfur removal of nickel species on the HBETA support with higher acid strength was better than on the HY support.

Monostyrene Intake in Albino Rats: Accumulation in Organs and Effects on Growth Performance and Oxidative Stress

Monostyrene (MS) residuals are daily migrating from different polystyrene shaping containers to our foods. In the present study, the distribution, accumulation and clearness rate of MS in different organs were done by one oral gavage of sub-lethal dose of 500 mg/kg bwt in male albino rates. Following MS in kidney, liver and brain indicated that the highest concentration peak was reached after 3 hr. Meanwhile, the maximum and minimum levels were detected in kidney (190.6 µg/100g) and brain (12.8 µg/100g), respectively. After 3 hr of styrene administration, the same decline rate was observed in the three organs. The clearness and metabolites rates of MS after 7 hr of administration were 93%, 76.9% and 71.1% in kidney, liver and brain, respectively. Further, this study investigated the effects of different MS at doses (0.1, 0.3 and 1.0 mg/kg) on growth performance parameters included weight gain (WG), relative liver weight, food efficiency ratio (FER), protein efficiency ratio (PER) and on oxidative stress biomarker; malondialdehyde (MDA) in the plasma of male and female albino rats after 12 weeks of feeding. All tested MS concentrations showed significant effects (P &gt;0.05) on WG, FER and PER of either male or female rats compared to the control group. All these indices were more pronounced in both male and female that administrated MS at dose of 1.0 mg MS/kg bwt. Only in female, relative liver weight was affected significantly at doses of 0.3 and 1.0 mg/kg bwt of MS. Significant differences (P &gt;0.05) were found among the experimental groups in malondialdehyde concentration in plasma of male and female rats; but not in nonlinear behavior. MDA concentration increased significantly (P &gt;0.05) in female plasma compared to male at all tested doses. Styrene concentration in male liver after three months at oral administration of 1 mg/kg was 1.72 µg/100g. It is concluded that MS at tested levels had affected growth performance parameters and led to increase oxidative stress which could have significant health risks. Kidney is the main organ responsible for MS elimination. More precaution should be addressed to food packaging industry to control and monitor MS release from PS food contact materials.

Respiratory and auditory health disorders among workers in a plastic factory (industrial zone, Queisna City, Menoufia Governorate)

Objective The aim of the study was to investigate auditory and respiratory health disorders among Egyptian workers in a plastic industry as well as assess the workplace environment in the same factory. Background The common health hazards associated with plastic manufacturing processes include noise, and exposure to respirable airborne particulates, especially polyvinyl chloride (PVC) and styrene, that lead to occupationally induced hearing loss and chronic effects such as decreased pulmonary function and lung disease. Participants and methods A cross-sectional comparative study was carried out in 180 workers in a plastic factory in Queisna City, Menoufia Governorate, Egypt, and in 60 nonoccupationally exposed individuals, who served as the control group. An environmental study of dust, fumes, and noise levels was carried out. Spirometric measurements were taken and air conduction audiometric examination was performed. Results The mean values of PVC, styrene concentrations, and noise levels are higher than the national and international permissible levels. Plastic factory workers had a highly significant prevalence of chest and auditory manifestations as well as deteriorated spirometric measurements and abnormal audiometric findings. Conclusion Exposure to a high level of PVC, styrene, and noise is implicated in the increase in frequency of chest manifestations, early spirometric changes, and occupationally induced hearing loss. Use of an automated plastic grinding machine to decrease the exposure to dust as well as use of good-quality personal protective equipment, especially masks and ear mufflers, is recommended.

Multipod-like silica/polystyrene clusters.

Multipod-like clusters composed of a silica core and PS satellites are prepared according to a seeded-growth emulsion polymerization of styrene in the presence of size-monodisperse silica particles previously surface-modified with methacryloxymethyltriethoxysilane. Tuning the diameter and concentration of the silica seeds affords homogeneous batches of tetrapods, hexapods, octopods, nonapods and dodecapods with morphology yields as high as 80%. Three-dimensional reconstructions by cryo-electron tomography are presented on large fields for the first time to show the high symmetry and regularity of the clusters demonstrating the good control of the synthesis process. These synthesis experiments are visited again digitally, in order to successfully refine an original simulation model and better understand the correlation between the history of the cluster growth and the final composition of the cluster mixture. Finally, using the model as a predictive tool and varying the extra experimental conditions, e.g. the composition of the surfactant mixture and the styrene concentration, result in trapping other cluster morphologies, such as tripods.

The Effect of Styrene Monomer in the Graft Copolymerization of Arcylonitrile onto Deproteinized Natural Rubber

Graft copolymerization of an acrylonitrile monomer onto Deproteinized Natural Rubber (DPNR) is an important process in the modification of Natural Rubber (NR) to increase its oil resistance. However, coagulation at the beginning of the process was a problem causing a copolymerization foil to occur. The presence of a styrene monomer is therefore expected to improve the emulsion condition so that coagulation can be prevented in the early reaction step. For comparison purposes, the processes with and without styrene were investigated. The influence of the concentration of styrene as well as the ratio of the DPNR:monomer on the stabilization process were also observed. The results showed that the addition of styrene could improve the stabilization process as proven by Fourier Transform Infrared Spectroscopy (FTIR). The presence of the functional group of CN at FTIR proved the production of the polyacrylonitrile in the mixture. The investigation showed that the concentration of styrene monomer, which led to the emulsion stability, is up to 1.5 wt% concentration of styrene at the ratio of DPNR:monomer (M) of 70:30 wt%.

Effects of Styrene-metabolizing Enzyme Polymorphisms and Lifestyle Behaviors on Blood Styrene and Urinary Metabolite Levels in Workers Chronically Exposed to Styrene.

The aim of this study was to investigate whether genetic polymorphisms of CYP2E1, GSTM1, and GSTT1 and lifestyle habits (smoking, drinking, and exercise) modulate the levels of urinary styrene metabolites such as mandelic acid (MA) and phenylglyoxylic acid (PGA) after occupational exposure to styrene. We recruited 79 male workers who had received chronic exposure in styrene fiberglass-reinforced plastic manufacturing factories. We found that serum albumin was significantly correlated with blood styrene/ambient styrene (BS/AS), urinary styrene (US)/AS, and US/BS ratios as well as urinary metabolites, that total protein correlated with US/MA and US/PGA ratios, and that low density lipoprotein (LDL)-cholesterol significantly correlated with US/BS, US/MA, and US/PGA ratios. Multiple logistic regression analyses using styrene-metabolizing enzyme genotypes and lifestyle habits as dependent variables and blood and urine styrene concentrations and urine styrene metabolite levels as independent variables revealed that CYP2E1*5 was associated with the MA/US ratio and GSTM1 with US/BS, that a smoking habit was associated with US/AS and MA/US ratios and MA and PGA levels, and that regular exercise was correlated with PGA/US. In conclusion, the results suggested that genetic polymorphisms of styrene-metabolizing enzymes, lifestyle behaviors, and albumin and LDL-cholesterol serving as homeostasis factors together are involved in styrene metabolism.

The effect of HRT and carriers on the sludge specifications in MBR to remove VOCs from petrochemical wastewater

This work employs two membrane bioreactors (with and without carrier) to evaluate the influence of carrier and hydraulic retention time (HRT) on the sludge specifications when removing organic volatile compounds (e.g. styrene and ethylbenzene) from petrochemical wastewater. This study is conducted during three various HRTs. The results indicate that the optimum HRT (e.g. 15 h.) was achieved in the reactor with carrier during biological removal and membrane fouling minimization. During the optimum HRT, the biological removal efficiency for styrene, ethylbenzene, and COD is 99.8 ± 0.1%, 99.8 ± 0.1%, and 99 ± 0.8%, respectively, and the concentration of styrene and ethylbenzene in the exit air reached to the minimum concentration (e.g. 0.1 and below 0.1 ppm, respectively). The fluctuation of the transmembrane pressure indicates a slight variation for the reactor with carrier rather than without carrier. Further, the sludge particle distribution in reactors demonstrates that the HRT reduction decreases the sludge particle size. This is also validated by flocculation ability tests. Finally, the alteration of soluble microbial product (SMP) and extracellular polymeric substance (EPS) in two reactors during all the HRTs show that the SMP is the main reason for fouling of the membranes and the EPS is not the main factor for sludge flocculation.

Optical properties of CCA films prepared with poly[styrene-co-sodium 1-allyloxy-2-hydroxypropane sulphonate] particles

In this study, we investigated the optical properties of CCA films prepared with poly[styrene-co-sodium 1-allyloxy-2-hydroxypropane sulphonate] particles via soap-free emulsion polymerisation. Experiments were performed by adjusting the several reaction factors such as styrene concentration, sodium 1-allyloxy-2-hydroxypropane sulphonate concentration, polymerisation temperature, initiator and divinylbenzene concentration. All latexes showed uniform spherical particles and they showed a size range of 160–550 nm. All CCA films prepared with self-assembled array showed the respective shiny structural colours from their photonic crystals. It is found that the changes in such polymerisation factors greatly affect the number of particles and particle diameter and refractive indices. Refractive indices and the reflectivity increased with sodium 1-allyloxy-2-hydroxypropane sulphonate concentration, on the other hand, and decreased with divinylbenzene concentration.

Biodegradation kinetics and interactions of styrene and ethylbenzene as single and dual substrates for a mixed bacterial culture.

This study examined biodegradation kinetics of styrene and ethylbenzene as representatives of alkenylbenzenes and mono-alkylbenzenes, respectively. The compounds were studied independently and as binary mixtures using a series of aerobic batch degradation experiments introduced by acclimatized mix culture. Initial concentration of styrene and ethylbenzene in the liquid phase vacillated from 0 to 220 mg/l. The Andrew model was applied for the biodegradation of individual substrates and the estimated constants of the equation for styrene and ethylbenzene were μmax = 0.1581, 0.2090 (1/h), KS =25.91, 37.77 (mg/L), KI =13.15, 62.62 (mg/L), respectively. The accomplished parameters from single substrate degradation tests were used to predict possible interaction factors achieved from dual substrate experiments. The Sum Kinetics with Interaction Parameters (SKIP) model and the purely competitive enzyme kinetics model were employed to evaluate any interactions. The SKIP model was found to accurately describe these interactions. Moreover, it was revealed that ethylbenzene plays an influential role on styrene consumption (e.g. IE,S = 1.64) compared to styrene which has insignificant inhibitory effect on ethylbenzene usage (e.g. IS,E =0.4) . The active site differences for styrene and ethylbenzene biodegradation and the pathway variations for biodegradation are among the major potential reasons for failure of the estimation that occurred in purely competitive kinetics model. This study is the first to calculate the interactions between styrene and ethylbenzene.

Application of response surface methodology for optimization of operational variables in photodegradation of aqueous styrene under visible light

In this study, the center composite design in response surface methodology was firstly applied to optimize the photocatalytic degradation of aqueous styrene under visible light. Twenty experiments were done by adjusting three parameters (initial concentration of styrene, concentration of catalyst and initial pH of reaction mixture) at five levels by the method of multiple variable analyses. Based on the experimental design, an empirical expression was firstly established and subsequently applied to predict the photocatalytic degradation efficiency of aqueous styrene under visible light. The results showed that the experimental photocatalytic degradation efficiencies are in accordance with the theoretically predicted values very well with a high correlation. The strongest interaction between the parameters assessed was concentration of catalyst /initial pH of mixture. Optimal experimental conditions for arbitrary aqueous styrene concentration of 115 mg L−1 were found initial pH 6.8 and catalyst loading 2 g L−1. The photocatalytic degradation efficiency of aqueous styrene under this condition reached to about 84%. Furthermore, the main degradation intermediate produced in this process was identified by GC/MS technique. The photocatalytic mineralization of styrene in aqueous solution has been studied by TOC.

Revisiting the reaction kinetics of selective hydrogenation of phenylacetylene over an egg-shell catalyst in excess styrene

Selective hydrogenation of phenylacetylene is an important reaction for the removal of a small amount of phenylacetylene from styrene monomer. In this work, the kinetics of phenylacetylene hydrogenation over an egg-shell Pd/Al2O3 catalyst in the presence of excess styrene was investigated by using a laboratory-scale fixed-bed reactor. The liquid-phase residence time distribution (RTD) in the reactor under different operating conditions was measured by tracer pulse method, and the Peclet number was determined based on the experimental data and the RTD model. The kinetic experiments showed that an increase in temperature and pressure or a decrease in the liquid hourly space velocity gave rise to increased conversion of phenylacetylene and decreased concentration of styrene. A rigorous mathematical model combining reaction kinetics, external mass transfer, intraparticle diffusion as well as axial dispersion of the liquid phase was developed to describe the selective hydrogenation of phenylacetylene in the reactor, and the kinetic and adsorption parameters involved in the kinetic model were estimated by minimization of the sum of squares of relative residuals between observed and model-derived concentrations of different components. The kinetic model can describe the phenylacetylene hydrogenation over the Pd/Al2O3 catalyst very well, and the activation energies for the hydrogenation reactions of phenylacetylene to styrene, styrene to ethylbenzene and phenylacetylene to ethylbenzene were 48.6, 52.2 and 57.9kJ/mol, respectively.

Styrene vapor mass transfer in a biotrickling filter: Effects of silicone oil volume fraction, gas-to-liquid flow ratio, and operating temperature

The addition of silicone oil as a non-aqueous phase (NAP) to the trickling liquid enhances the mass transfer of hydrophobic compounds from gas to liquid phase in biotrickling filters (BTFs). The present study investigated the effect of NAP volume fraction (ϕ; 0–20%), gas-to-liquid flow ratio (7.5, 16 and 32), and operating temperature (30 and 50°C) on styrene mass transfer in a BTF under abiotic conditions using a full-factorial experimental design. The BTF was packed with a mixture of pumice and steel pall rings. The inlet styrene concentration was 0.5–1.2gm−3 and EBRTs were set at 1 and 2min. The results were incorporated into a model to calculate the maximum fraction of styrene transferable from the gas to the aqueous phase (βS∗). The βS∗ was determined to be 0.208–1, depending on the operating conditions. Flow ratio and ϕ were the most significant factors affecting styrene mass transfer (p-value=0.0348 and p-value=0.0230, respectively). Temperature had no significant effect on the model (p-value=0.9322) at a 95% confidence interval. Styrene mass transfer was very sensitive to ϕ when ϕ<10%; at ϕ>10% the addition of silicone oil had a slight effect on βS∗.

Mechanistic insights into catalytic linear cross-dimerization between conjugated dienes and styrenes by a ruthenium(0) complex

The mechanistic studies for linear cross-dimerization between 2,3-dimethylbuta-1,3-diene and styrene by a Ru(0) complex, Ru(η6-naphthalene)(η4-1,5-COD) (1), are performed both by kinetic and computational studies. This reaction is basically zero-order to both of the diene and styrene concentrations and first-order to the catalyst concentration. The Hammett plot using p-substituted styrenes gives a linear relationship with a positive slope (ρ = +0.482). The deuterium isotope experiment clearly shows the present reaction being a formal 1,4-addition of a C–H bond in styrene to cisoid-1,3-diene. These kinetic studies show the reaction proceeding via oxidative coupling mechanism that is also supported by the DFT calculations.

Biomonitoring for Exposure Assessment to Styrene in the Fibreglass Reinforced Plastic Industry: Determinants and Interferents.

Fifty-eight workers exposed to styrene were monitored in four fibreglass reinforced plastic industries of Central Italy. The aim of the study was to explore the factors that can influence the levels of styrene exposure biomarkers of the workers and the aspects that might interfere with the exposure assessment measures, such as the co-exposure to acetone. Personal monitoring of professional exposure to airborne styrene and acetone was carried out by Radiello samplers and GC/MS analysis. Biological monitoring was performed by the determination of urinary metabolites, mandelic (MA), and phenylglyoxylic (PGA) acids with HPLC/MS/MS and unmetabolized styrene in saliva and venous blood by HS/GC/MS. The median values of the four sites ranged between 24.1 to 94.0mg m(-3) and 7.3 to 331.1mg g(-1) creatinine for airborne styrene and MA + PGA, respectively. A good linear correlation was found between styrene in air and its urinary metabolites (r = 0.854). The median value for airborne styrene was found to exceed the (Threshold Limit Value - Time Weighted Average) of 85 mg m(-3) in one site for all the workers and in two if only moulders are considered. The multiple linear regression model showed that the determinants of urinary MA + PGA excretion were the type of process, workers' tasks, level of acetone co-exposure, and the use of respiratory protection devices. Data show that the simultaneous exposure to acetone modify the styrene metabolism with a reduction in the levels of (MA + PGA) excreted. A significant linear log-correlation was found between salivary levels of styrene and blood concentration (r = 0.746) sampled at the same t x time.

Surface structure and composition of narrowly-distributed functional polystyrene particles prepared by dispersion polymerization with poly(l-glutamic acid) macromonomer as stabilizer

A novel macromonomer composed of poly(α-l-glutamic acid) was used as a stabilizer for dispersion polymerization of styrene in DMF–water medium with AIBN initiator, giving narrowly-distributed functional polystyrene particles on which the poly(α-l-glutamic acid) was grafted. The resultant particles had 0.54–2.12 μm in size and 0.2–2.6 residue/nm2 in surface density and showed a pH-responsive colloidal behavior associated with a helix–coil transformation of the surface poly(α-l-glutamic acid). Not only the particle size but also the surface density were controlled with macromonomer concentration, macromonomer length, DMF composition, and styrene concentration, while no consistent trend for AIBN concentration was observed. A gel-permeation-chromatography curve of the particles was separated into three components. We tentatively identify the origin of each component and propose a possibility that unstable particles, which were generated even after the growing particles were stabilized, took an important role in particle growth and size distribution of the resultant particles.

Thermal, physico‐mechanical, and morphological properties of HDPE graft‐copolymerized with polystyrene

In this study, polystyrene was graft‐copolymerized onto high‐density polyethylene (HDPE) by in situ polymerization of styrene monomer to change the physico‐mechanical and thermal properties of HDPE. The grafting was carried out in a Brabender‐type static mixer by injecting styrene monomer directly into the molten HDPE in the presence of a free‐radical initiator (lauroyl peroxide or LP). The effect of wt% of styrene and initiator concentrations on thermal, physico‐mechanical, and morphological properties of HDPE was investigated. The neat and modified HDPE was characterized by differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and also by tensile strength and contact angle measurements. It was found that the increase in wt% of styrene and LP dosage reduced elongation at break, hygroscopic expansion and also the melting, and the crystallization temperatures of HDPE but increased its tensile strength. The tensile strength was increased from 14.6 MPa for the neat HDPE to 20.6 MPA for the 10 wt% of styrene grafted onto HDPE using 0.8% LP. Scanning electron microscopy results show that there was no phase separation, and the grafted polystyrene became integral part of HDPE. The results demonstrate that styrene could be used in melt compounding to improve various properties of HDPE. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Characterization of the auto‐curing behavior of rapid prototyping materials for three‐dimensional printing using dielectric analysis

Three‐dimensional printing technology applies the high efficiency of the ink jet printer technology to manufacture functional prototypes. To optimize the printing process of PMMA powder containing an initiator and a liquid binder consisting of polymerizable monomers with activator molecules, the knowledge of the curing kinetics is required. Therefore, a methodology was developed to apply dielectric analysis measuring changes of the ion and dipole mobility in terms of a quantity called ion viscosity. Connecting time‐dependent changes of ion viscosity and reaction heat determined by DSC leads to detailed insight into the curing process. The results show that the styrene concentration of the binder determines the curing kinetics—reduces thermal stresses and provides time for stress relaxation. The curing process differs significantly with respect not only to composition of the binder, but also to its aging state. The proposed approach can be implemented directly to a printer to detect dielectric changes of the materials during the manufacturing process. POLYM. ENG. SCI., 55:1485–1493, 2015. © 2015 Society of Plastics Engineers