Comparison of thermal degradation products from real municipal waste plastic and model mixed plastics

The thermal degradation of real municipal waste plastic (MWP) obtained from Sapporo, Japan and model mixed plastics was carried out at 430 °C in atmospheric pressure by batch operation. The chlorinated hydrocarbons found in PE/PP/PS/PVC [poly(ethylene)/poly(propylene)/poly(styrene)/poly(vinyl chloride)] degradation liquid products were also observed in PE/PP/PS/PVC/PET (poly(ethylene terephalate)) and MWP degradation liquid products. The presence of PET in MWP produced the additional chlorinated hydrocarbons, which are similar to the chlorinated hydrocarbons observed during the PE/PP/PS/PVC/PET degradation liquid products. In addition, the presence of PET facilitated the formation of more organic chlorine content in liquid products and drastic decrease in the formation of inorganic chlorine content.     

The effect of silica–alumina catalysts on degradation of polyolefins by a continuous flow reactor

Catalytic degradation of polyolefins was performed in a continuous flow reactor that allows the study of the degradation processes at steady state, characterized by constant values of reaction parameters and properties of the products. The continuous flow reactor was operated at atmospheric pressure and at feed rate of 0–1.5 kg h^?1 polyolefins over two silica–alumina catalysts having different SiO₂/Al₂O₃ mole ratio. Polyethylene (PE), polypropylene (PP) and polystyrene (PS) were degraded at 420, 380 and 360 °C respectively. The cracking effect of silica–alumina was proved by the increased amount of gaseous products and by the decreased molecular weight of liquid products. The differences in surface area and in concentration and acidic strength of active centers of the two catalysts affected the distribution of degradation products. Molar rate of degradation was increased in the presence of catalysts, however the mass rate of degradation was decreased leading to higher values of the calculated activation energies. These interesting results might open new perspectives in understanding the macroscopic mechanism for catalytic degradation of polyolefins.     

Catalytic coprocessing of waste plastics and petroleum residue into liquid fuel oils

Waste plastics of different types were catalytically coprocessed with petroleum residue of light Arabian crude oil in the presence of a number of catalysts. The purpose of the study was to explore effects of various conditions such as catalyst type, amount of catalyst, reaction time, pressure and temperature on the product distribution. The waste plastic studied included low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS) and polypropylene (PP). A series of single (waster plastic with catalyst) and binary (waste plastic and residue with catalyst) reactions were carried out in an autoclave reactor under variable reaction conditions. The reaction conditions used were 1, 3 and 5 wt.% catalysts, 30–120 min reaction time, 400–430 °C reaction temperature and 500–1200 psi hydrogen pressure. The product distribution achieved for residue/plastic/catalyst system showed higher yields of liquid fuels as compared to residue/plastic system. Hydrocarbon gases were formed as well along with heavy oils, insoluble gums and coke. At the reaction conditions of 3 wt.% NiMo catalyst, 90 min reaction time, 1200 psi hydrogen gas pressure, 430 °C temperature and residue to plastic feed ratio of 3:2 (wt.) afforded maximum conversion of the plastics into liquid fuel oils.     

Effect of ionizing radiation on physicochemical and mechanical properties of commercial monolayer and multilayer semirigid plastics packaging materials

Tensile testing, overall migration tests and sensory tests were used to evaluate the effects of gamma irradiation (5–60 kGy) on six commercial semirigid packaging materials. The monolayer and multilayer materials in sheet or bottle form were: polystyrene (PS), polypropylene (PP), polyvinyl chloride/high-density polyethylene (PVC/HDPE), polyethylene terepthalate (PET), HDPE/polyamide (HDPE/PA) and HDPE. In terms of mechanical strength, PET was the most radiation-resistant material, while the HDPE monolayer and multilayer showed some degradation after 60 kGy. PS was slightly affected after 30 kGy, whereas PP was severly degraded and became very brittle. Generally, there was no change in overall migration at lower doses; at higher doses migration from PP tended to increase, while migration from HDPE/PVC tended to decrease. Odor and taste transfer as well as discoloration were observed with most plastics, especially at higher doses, and it is concluded that these tests are a sensitive and important quality control tool for evaluating irradiated packaging materials.     

Surface modification of polymers. IV. UV initiated degradation of polymers with stabilizers grafted onto the surface

Polypropylene (PP), Polyethylene (PE), and polystyrene (PS) films were grafted with glycidylmethacrylate in thin surface layers. To the oxiran groups thus grafted onto the surface three UV stabilizers were attached, 4-amino-2,2,6,6-tetramethylpiperidine (AP), 2,4-dihydroxybenzophenone (DHBP), and phenyl 4-aminosalicylate (PAS). The amount of stabilizer grafted onto the surface varied between 25 and 40 nmol/cm² depending on the polymer substrate. The samples were exposed to UV radiation in air, and the degradation and oxidation of the polymers were studied with IR, UV, and ESCA spectroscopy and by stress–strain measurements. PP grafted with AP exhibited a near 20-fold increase in lifetime compared with the unprotected PP, AP did not stabilize the PE or PS samples. DHBP was an efficient stabilizer of PE, the oxidation rate of the grafted sample being 1/2 to 1/3 of the ungrafted. A similar effect was observed when DHBP was grafted onto PP and PS. PAS underwent a rearrangement reaction when irradiated with UV light, and had only a slight stabilizing effect.     

Production of valuable hydrocarbons by catalytic degradation of a mixture of post-consumer plastic waste in a fluidized-bed reactor

A mixture of post-consumer plastic waste (PE/PP/PS/PVC) was pyrolyzed over various catalysts using a fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A model based on kinetic and mechanistic schemes for the observed products associated with chemical reactions and catalyst deactivation has been developed. The model gives a good representation of experimental results. It is also an improvement on the currently available empirical “lumping” techniques which are usually severely restricted in terms of product definitions. Additionally, this model represents the benefits of product selectivity for the chemical composition in relation to the effect of structurally different catalyst types, and the performance of the reaction temperature used as well as the particle size of the catalyst selected.     

The effect of electric discharges on electrophysical properties of polymer blends

The electric aging of HDPE-PP blends obtained from melt and PS-PVC blends prepared from solution is studied in the range of low (0.1–10 wt %) concentrations of the second component. It is found that the addition of a minor amount of PE (1–2 wt %) to PP significantly intensifies changes in the electric properties and erosion of PP. For a PS-PVC blend, the addition of small (up to 1 wt %) amounts of PVC leads to an abnormally rapid degradation of PS.     

Effects of gamma irradiation on poly(vinyl chloride)/polystyrene blends: Investigation of radiolytic stabilization and miscibility of the mixture

Commercial polystyrene (PS) has been studied as a modifier for commercial poly(vinyl chloride) (PVC) when it was submitted to gamma irradiation. PVC/PS blends were prepared with 100/0, 95/05 and 90/10 compositions. Results for gamma-irradiated (⁶⁰Co) blends are reported and changes in viscosity-average molar mass (M_v) were analyzed. The study showed that the addition of PS into PVC decreased by 73% (95/05) and 79% (90/10) the number of scissions/100 eV in the dose range of 25-100 kGy. Viscosity analyses by the Pan et al. criterion and analyses of FT-IR spectra in the C-Cl vibration region showed negligible intermolecular interactions between the components of PVC/PS blends. However when the films of blends were irradiated to 50 kGy, certain intermolecular interactions were observed by the viscosity method. The addition of PS to PVC and the main scission effect induced by gamma irradiation decreased crosslink density of blends causing changes in the elongation of break and Young's modulus.     

Synthesis and characterization of polyethylene‐g‐polystyrene as the compatibilizer for polypropylene/ Polystyrene blends

Polyethylene‐g‐polystyrene (PE‐g‐PS) was synthesized as a compatibilizer for polypropylene/polystyrene­(PP/PS) blends by the living radical polymerization of styrene with polyethylene‐co‐glycidylmethacrylate (PE‐co‐GMA). The compatibilizer effect of PE‐g‐PS on the morphology and thermal properties of PP/PS blends was investigated. The crystalline temperature of PP in PP/PS blends decreased with increasing PE‐g‐PS contents. Morphologies of PP/PE‐g‐PS/PS blends showed much better dispersion of each domain for higher PE‐g‐PS contents. The molecular weight of PS segment in PP/PE‐g‐PS/PS blend was increased by addition of styrene monomer during the post melt blending process where post living radical polymerization reaction proceeded. Copyright © 2003 John Wiley & Sons, Ltd.     

Calytic Degradation of Mixed Plastics Using Natural Clinoptilolite Catalyst

Catalytic degradation of the mixture of polyethylene (PE), polypropylene (PP), and polystyrene (PS) was investigated in a semi-batch reactor. The main degradation product was liquid oil with gasoline range carbon number distributions. Clinoptilolite a natural zeolite (HNZ) showed as good a catalytic performance as silica-alumina (SA). The protonated catalysts (HNZ, HZSM-5) showed an increased production of ethylbenzene, but a decrease of styrene production. Increase of degradation temperature resulted in a decrease of ethylbenzene and propylbenzene, but an increase of styrene. Thermogravimetric analysis revealed that the increased degradation rate in the mixed plastics came from the intermolecular carbenium ion transfer between the degraded fragments of PE, PP, and PS.This revised version was published online in December 2005 with corrections to the Cover Date.     

Potentiometric sensor for phenylephrine based on phenylephrine-tetraphenylborate lipophilic salt

Phenylephrine (PE) ion-selective electrode based on incorporation of phenylephrine-tetraphenylborate lipophilic salt in plasticized PVC matrices is constructed. The electrode shows near Nernstian response over the concentration range 1.5 × 10^–4-10^–1 M in solutions of pH 2.9–8.0 at 25°C. The electrode resists the effect of heat in the temperature range 25–55°C exhibiting an isothermal temperature coefficient of 0.0007 V/°C. The selectivity of the electrode for PE towards large number of inorganic cations, sugars and amino acids is investigated. Determination of PE in an eye-drops pharmaceutical preparation is carried out using the proposed electrode as potentiometric sensor.     

Effect of gamma radiation on the performance of jute fabrics-reinforced polypropylene composites

Jute fabrics-reinforced polypropylene (PP) composites (50% fiber) were prepared by compression molding. Composites were fabricated with non-irradiated jute fabrics/non-irradiated PP (C-0), non-irradiated jute fabrics/irradiated PP (C-1), irradiated jute fabrics/non-irradiated PP (C-2) and irradiated jute fabrics/irradiated PP (C-3). It was found that C-3 composite performed the best mechanical properties over other composites. Total radiation dose varied from 250–1000 krad and composites made of using 500 krad showed the best results. The optimized values (C-3 composites) for tensile strength (TS), bending strength (BS) and impact strength (IS) were found to be 63 MPa, 73 MPa and 2.93 kJ/m², respectively.     

Isoconversional kinetics of degradation of polyvinylpyrrolidone used as a matrix for ammonium nitrate stabilization

Thermogravimetric analyzer (TGA) has been applied to measure the kinetics of the thermal degradation of virgin polyvinylpyrrolidone (PVP) and a phase stabilized PVP–ammonium nitrate (AN) material. The PVP–AN samples have been prepared by using 20 wt.% of AN and PVP of three different molecular weights. Virgin PVP undergoes a major mass loss in the region 380–550 °C leaving a small amount of nonvolatile residue. The application of an advanced isoconversional method to the respective degradation process demonstrates that its effective activation energy increases from 70 kJ mol⁻¹ to a plateau value at 250–300 kJ mol⁻¹, which is independent of the molecular weight. The PVP–AN materials lose spontaneously 20% of their mass on heating above the glass transition temperature of the PVP matrix (160–180 °C). After the escape of AN, the remaining PVP matrix degrades in the same temperature region as virgin PVP, however, the effective activation energy of this degradation is 150–200 kJ mol⁻¹.     

The photolysis in polymer matrices of dyes containing a benzothioxanthene chromophore linked with a hindered amine

Novel dyes based on a benzothioxantheneimide chromophore covalently linked with a sterically hindered amine (HAS) were prepared and their light stability was tested in polymer matrices. The following dyes: 2-(2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINH) and N-alkoxy derivative 2-(1-(1′-phenylethoxy)-2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej] isoquinoline-1,3-dione (BTXINOR) were prepared. For comparison the parent dye without HAS structural unit benzothioxanthene-3,4-dicarboxylic anhydride and the N-alkyl derivative 2-(1-dodecyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXID) and the stable nitroxyl radical 2-(1-oxo-2,2,6,6-tetramethyl-4-piperidyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTXINO) were also tested. Their spectral properties, absorption and fluorescence have been examined in polystyrene (PS), poly(methyl methacrylate) (PMMA), poly(vinyl chloride) (PVC) and in isotactic polypropylene (PP). The light stability of these dyes and model compounds were examined in thin polymer films. The photolysis rate was monitored by UV spectroscopy and for all additives under study it was in the range 10⁻⁴–10⁻³ h⁻¹. The rate of decomposition was the lowest for the parent amine BTXINH in PMMA, PS and PVC. The rate constants of photolysis are about 10 times higher for all adducts and the lowest rate of decomposition in PP matrix was observed for BTXINOR. A distinct stabilization effect of HAS structural unit on the dye decomposition was not observed. The light stability of the dyes was more influenced by the selection of the polymer. The photolysis proceeds rather fast in PP, and moderately in PS and PVC compared to PMMA.     

Morphologies, crystallinity and dynamic mechanical characterizations of polypropylene/polystyrene blends compatibilized with PP-g-PS copolymer: Effect of the side chain length

PP-g-PS copolymers were synthesized with the same polypropylene (PP) backbones and various side chain lengths of PS sequences via reactive comonomer p-allyltoluene (p-AT) by Ziegler–Natta copolymerization and the subsequent living anionic graft-polymerization. ¹H NMR characterized that the PP-g-PS copolymer had grafted 3.15 side chains per 1000 carbons in the PP backbones and the length of PS sequences varied in the range of 25.8–309.9 units. PP/PS blends with the PP-g-PS copolymer as compatibilizer (wt. 75/25/5) were prepared and characterized by SEM, WAXD and DMA to investigate the morphologies, crystallinity and glass transition temperatures of the PP/PS blends. All the results pointed out that the average side chain length (GL) of the graft copolymer (GL is from 25.8 to 309.9) made great effects of the PP/PS blends, such as the PS dispersed phase, the crystallinity of the PP component and the two glass transition temperatures of the blends, which showed the same trend with the increase of the GL. Overall, only with a suitable average side chain length, the PP-g-PS copolymer could achieve optimal compatibilizing efficiency of the PP/PS blends.     

Catalytic degradation of polyolefins over hexagonal mesoporous silica: Effect of aluminum addition

Degradations of polypropylene (PP) and polyethylene (PE) over pure hexagonal mesoporous silica and aluminum-containing hexagonal mesoporous silica catalysts were studied in a fixed bed catalytic reactor at 380 and 430 °C, respectively. The thermal and catalytic degradations of both PP and PE in liquid-phase-contact and vapor-phase-contact modes over pure hexagonal mesoporous silica had no significant effect on the product yields. The liquid products were widely distributed in hydrocarbons with boiling point ranges of 36–405 °C. By adding a small amount of aluminum to the hexagonal mesoporous material, aluminium-containing hexagonal mesoporous silica exhibited good performance in cracking heavy molecular weight hydrocarbons into light hydrocarbons. High liquid yields and less coke deposits were obtained in liquid-phase-contact reaction with increasing aluminum content. The liquid products were mainly composed of C₅–C₁₀ hydrocarbons with boiling points of 36–174 °C, and propene, butene, and butane were main components in gaseous products. The effect of degradation temperature was not observed on product yields though degradation rate of polyolefin into liquid products was faster. Conversely, in vapor-phase-contact reaction, an increase in gaseous yield was observed when increasing the amount of aluminum and temperature of the cracking reactor, while the residue yield remained constant.     

Cathodic electrophoretic deposition of manganese dioxide films

Cathodic electrophoretic deposition (EPD) method has been developed for the deposition of manganese dioxide films. It was shown that phosphate ester (PE) is an effective charging additive, which provides stabilization of manganese dioxide nanoparticles in suspensions. The influence of PE concentration and deposition voltage on the deposition efficiency has been studied. EPD has been utilized for the fabrication of porous nanostructured films with thickness in the range of 0.5–20 μm for application in electrochemical supercapacitors (ES). Cyclic voltammetry and chronopotentiometry data for the films tested in the 0.1 M Na₂SO₄ solutions showed capacitive behavior in the voltage window of 1 V. The highest specific capacitance (SC) of 377 F g⁻¹ was obtained at a scan rate of 2 mV s⁻¹. The SC decreased with increasing film thickness and increasing scan rate in the range of 2–100 mV s⁻¹. The deposition mechanism, kinetics of deposition and charge storage properties of the films are discussed.     

Structural aspects of the radiation modification of the dielectric properties of polyolefins

The effects of crystallization conditions and supermolecular structure on the processes of radical formation and changes in the dielectric (tan; ) and strength (E _st) properties of LDPE, HDPE, and PP under exposure to -radiation were studied. It was found that polyolefin specimens with a high crystallinity exhibited an enhanced electric strength, radiation stability, and a high yield of quasi-stable radicals at 293 K. It was assumed that a possible mechanism of the electric strengthening of PE and PP by their radiation modification (at radiation doses of 30–50 and to 5–6 Mrad, respectively) consists in a reaction of the type R^· + e^– R^–, the capture of trapped electrons by quasi-stable radicals.__________Translated from Khimiya Vysokikh Energii, Vol. 39, No. 3, 2005, pp. 176–182.Original Russian Text Copyright © 2005 by Magerramov, Dashdamirov.     

Kinetics of the dehydrochlorination of poly(vinyl chloride) in the presence of NaOH and various diols as solvents

The dehydrochlorination of PVC in the presence of NaOH was investigated in different diols. Diethylene glycol (DEG), triethylene glycol (TEG), and propylene glycol (PG) were found to be effective in accelerating the dechlorination of PVC. The dehydrochlorination was promoted in the order TEG > DEG > PG, which was in agreement with the compatibility between PET and the diol. Compatibility resulted in an improved penetration of the PVC particle by the solvent, leading to the acceleration of the dehydrochlorination. The dehydrochlorination of PVC in NaOH/diol followed first-order kinetics, confirming the progress of the reaction under chemical reaction control. The apparent activation energies were 82 kJ mol⁻¹, 109 kJ mol⁻¹, and 151 kJ mol⁻¹ for TEG, DEG, and PG, respectively. The lower the activation energy became the faster the dehydrochlorination of PVC proceeded.     

Tertiary recycling of commingled polymer waste over commercial FCC equilibrium catalysts for producing hydrocarbons

A mixture of post-consumer polymer waste (PE/PP/PS) was pyrolysed over cracking catalysts using a fluidising reaction system similar to the FCC process operating isothermally at ambient pressure. Greater product selectivity was observed with a commercial FCC equilibrium catalyst (FCC-E1) with about 53 wt% olefin products in the C₃-C₆ range. Experiments carried out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. A kinetic model based on a lumping reaction scheme for the observed products and catalyst coking behaviours has been investigated. The model gave a good representation of experiment results. This model provides the benefits of lumping product selectivity, in each reaction step, in relation to the performance of the catalyst used and particle size selected as well as the effect of operation conditions, such as rate of fluidising gas and reaction temperature. It is demonstrated that under appropriate reaction temperatures and suitable catalysts can have the ability to control both the product yield and product distribution from polymer degradation, and can potentially lead to a cheaper process with more valuable products.