Compatibilization of recycled and virgin PET with radiation-oxidized HDPE

Blends of high-density polyethylene (HDPE), which cross-links on radiation, and both, recycled and pristine polyethylene terephtalate (PET), one of the most radiation-stable polymers, that contain aromatic groups, which are effective at dissipation of the energy of the ionizing radiation, were irradiated with gamma rays, in order to form a copolymer capable of improving the compatibility of the blend HDPE/PET. Due to the low content of the PET in the resulting copolymer, blends PET and radiation-oxidized HDPE, were also studied. The tensile and flexural properties were improved when the PET content was increased and when the HDPE was pre-irradiated; the largest increase in the mechanical properties was observed for PET contents between 10% and 20% (w/w). The improvement in the properties is believed to occur because of a percolation effect of the PET in the HDPE matrix and the radiation-improved compatibility by means of polar groups formed in the polyethylene. However, impact properties were observed to decrease when the PET content increased in spite of the irradiation.     

The effect of molecular weight on the topography of thin films of blends of poly(4-bromostyrene) and polystyrene

Blends of polystyrene and poly(4-bromostyrene) phase-separate during spin-casting onto silicon wafers to give a thin film with islands of poly(4-bromostyrene) in a sea of polystyrene. Variation of the molecular weights of the blend components shows that the poly- (4-bromostyrene) and polystyrene influence the film structure in different ways. For poly(4-bromostyrene) of a given molecular weight, the ratio of the observed feature height to the overall film thickness remained constant as the film thickness increased. Moreover, the mean height of the topographical features was independent of the polystyrene but decreased with the molecular weight of the brominated polymer. It is concluded that the substrate–poly(4-bromostyrene) interaction dominates the formation of topography and consequently, though the islands are poly(4-bromostyrene), the mean height of the topographical features is greater the lower the molecular weight of the brominated polymer. The polystyrene has a secondary role, altering the thermodynamics or viscosity of the blend, thereby controlling the number of islands formed: the higher the molecular weight of the polystyrene the greater the number of islands. Received: 2 December 1999 Accepted: 7 April 2000     

Binary and ternary blends of high‐density polyethylene with poly(ethylene terephthalate) and polystyrene based on recycled materials

Binary blends of recycled high‐density polyethylene (R‐HDPE) with poly(ethylene terephthalate) (R‐PET) and recycled polystyrene (R‐PS), as well as the ternary blends, i.e. R‐HDPE/R‐PET/R‐PS, with varying amounts of the constituents were prepared by twin screw extruder. The mechanical, rheological, thermal, and scanning electron microscopy (SEM) analyses were utilized to characterize the samples. The results revealed that both R‐HDPE/R‐PET and R‐HDPE/R‐PS blends show phase inversion but at different compositions. The R‐PET was found to have much higher influence on the properties enhancement of the R‐HDPE compared to R‐PS, but at the phase inverted situation, a significant loss in the tensile strength of R‐HDPE/R‐PET blend was observed due to the weak interaction at this morphological state. However, the ternary blends with higher loading of second phase, namely greater than 50 wt% of R‐PET+R‐PS, demonstrated better mechanical properties than the binary blends with the same content of either R‐PET or R‐PS. Copyright © 2009 John Wiley & Sons, Ltd.     

Weld line morphology and strength of polystyrene/polyamide-6/poly(styrene-co-maleic anhydride) blends

The effect of weld line on the morphology and mechanical properties of 70/30 polystyrene and polyamide-6 blends with various amounts of poly(styrene-co-maleic anhydride) (SMA) as compatibilizer was investigated. For blends without or with low content of SMA, the dispersed domains near the weld line were elongated parallel to the weld line; and the dispersed domains in weld line were spherical. But for blend with high content of SMA, the isotropic morphology was observed. And the difference of morphology at weld line caused the distinction of fracture mechanism. The tensile strength of the blend is greatly influenced by the morphology of dispersed domains at weld line. While the morphology has only slight effect on impact strength of the blends.     

Viscometric study on the miscibility of polystyrene/brominated polystyrene blends

The miscibility of polystyrene/brominated polystyrene blends (PS/PBrS) was investigated by using dilute-solution viscometry (DSV) method. The intrinsic viscosity and the viscometric parameters of this system have been determined at 20 ± 0.1 °C for prepared several PS/PBrS compositions (85/15, 75/25, 50/50, 25/75, 10/90). The binary systems were prepared in chloroform at five different concentrations; 0.15, 0.30, 0.60, 0.90, 1.20 g 100 ml⁻¹. The miscibility criteria on the basis of the sign of Δ[η] _m, Δb and Δb′, which are based on the difference between experimental and ideal values of [η]_m, and b_m were calculated by applying the Garcia et al., Catsiff-Hewett and Krigbaum-Wall theoretical equations. The thermodynamic parameter, α, modified thermodynamic parameter, β, and interaction parameter, μ, were also estimated. The data obtained from the viscometry studies showed that the examined blends were immiscible in all the compositions range besides the composition (10/90). The results from the DSV method are correlated with the miscibility data obtained for the same blend by differential scanning calorimetry (DSC) find.     

Miscibility and interactions of polystyrene/polyolefine and polystyrene/poly(n-alkyl methacrylate) mixtures in dilute xylene solutions

The miscibility and intermolecular interactions between polystyrene (PS) and poly(ethylene-co-propylene) (EPC), as well as between PS and long-chain poly(alkyl methacrylates) (PAMA), namely, poly(dodecyl methacrylate) (PDDMA) and poly(octadecyl methacrylate) (PODMA), in dilute xylene solutions at 30 °C were studied. Investigated polymers are widely used as rheology modifiers, i.e. viscosity index improvers and pour point depressants for lubricating mineral oils. The specific and reduced viscosities of two- and three-component polymer solutions as well as intrinsic viscosities and Huggins’ parameter values were determined as functions of the polymer mixture composition and overall polymer concentration. The reduced viscosity was found to be linearly dependent on the overall polymer concentration. The observed viscosities of polymer mixtures were intermediate to those of the mixture constituents; the values decrease in the order: EPC > PS > PAMA. The specific viscosities of all the polymer mixtures obtained as the experimental results and calculated applying the Catsiff-Hewett and Krigbaum-Wall theoretical equations were considered. Since all the polymer/polymer pairs showed the negative viscometric interaction parameter values (Δb₁₂ < 0), the PS/EPC and EPC/PAMA mixtures were found to be immiscible. The observed repulsive molecular interactions originate from the differences in polymer composition and molar masses. This conclusion was supported by calculations employing the group contribution approach of Coleman, Graf and Painter. The calculated values of interaction parameters for (co)polymer blends, Λ₁₂, were 5.47, 6.42 and 13.1 J cm⁻³ for PS/PDDMA, PS/PODMA and PS/EPC, respectively.     

Superdrawing of polytetrafluoroethylene virgin powder above the static melting temperature

A new two‐stage draw technique was successfully applied to the superdrawing of polytetrafluoroethylene (PTFE) virgin powder. A film, compression‐molded from powder below the melting temperature (T_m = 335 °C), was initially solid‐state coextruded to an extrusion draw ratio (EDR) of 6–20 at 325 °C, about 10 °C below the T_m. These extrudates from the first‐stage draw were further drawn by a second‐stage pin draw in the temperature (T_d) range of 300–370 °C that covers the static T_m. The maximum achievable total draw ratio was ～60 at a T_d = 300 °C and increased rapidly with increasing T_d, reaching a maximum of 100–160 at a temperature window between 340 and 360 °C, depending on the initial EDRs. At yet higher T_d's, the ductility was lost as a result of melting. The high ductility of the PTFE extrudates at such high temperatures was ascribed to the improvement of interfacial adhesion and bonding between the deformed powder particles upon the first‐stage extrusion combined with the rapid heating of only a portion of the extrudate followed by the elongation at a high rate. The highly drawn fibers were highly crystalline (χ_c ≤ 87%) and showed high chain orientation (f_c ≤ 0.997) and a large crystallite size along the chain axis (D₀₀₁₅ ≤ 160 nm). The molecular draw ratio, estimated from the entropic shrinkage above the T_m, was close to the macroscopic deformation ratio independently of the initial EDRs. These results indicate that the draw was highly efficient in terms of chain extension, orientation, and crystallization. Thus, the maximum tensile modulus and strength achieved in this work were 102 ± 5 and 1.4 ± 0.2 GPa, respectively, at 24 °C. These tensile properties are among the highest ever reported on oriented PTFE. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1995–2004, 2001     

蛋壳型Ni/Al2O3催化剂的制备研究

随着生产的发展,工业装置日趋大型化,催化剂内表面利用率?宏观选择性?阻力降等问题日益引起人们的注意。为了提高催化剂的利用率,人们开始关注活性组分非均匀分布催化剂[1-2]。活性组分非均匀分布催化剂分为蛋壳型?蛋白型和蛋黄型三种典型类型[3]。蛋壳型催化剂能减少贵金属活性组分的用量,提高不可逆串联反应过程中中间产物的选择性[4,5];除此外蛋壳型催化剂抗自身中毒的性能较好[6-9]。本文用几种方法来制备蛋壳型催化剂,并对其进行了比较,由实验数据和理论分析得出:刷涂沉淀法能使活性组分N i最集中分布在活性氧化铝球载体表面,制得活性…     

Fabrication of macroporous polystyrene/graphene oxide composite monolith and its adsorption property for tetracycline

Macroporous polystyrene microsphere/graphene oxide(PS/GO) composite monolith was first prepared using Pickering emulsion droplets as the soft template. The Pickering emulsion was stabilized by PS/GO composite particles in-situ formed in an acidic water phase. With the evaporation of water and the oil phase(octane), the Pickering emulsion droplets agglomerated and combined with each other, forming a three-dimensional macroporous PS/GO composite matrix with excellent mechanical strength. The size of the macrospores ranged from 4 mm to 20 mm. The macroporous PS/GO composite monolith exhibited high adsorption capacity for tetracycline(TC) in an aqueous solution at p H 4–6. The maximum adsorption capacity reached 197.9 mg g 1at p H 6. The adsorption behaviour of TC fitted well with the Langmuir model and pseudo-second-order kinetic model. This work offers a simple and efficient approach to fabricate macroporous GO-based monolith with high strength and adsorption ability for organic pollutants.     

Multiobjective Optimization of Fabrication Parameters of Jute Fiber/Polyester Composites with Egg Shell Powder and Nanoclay Filler

In the present study, a model is presented to optimize the fabrication parameters of natural fiber reinforced polyester matrix composites with dual fillers. In particular, jute fiber mat was chosen as reinforcement and eggshell powder (ESP) and montmorillonite nanoclay (NC) were selected as fillers. The weight per square meter (GSM) of the fiber, the weight percentage of ESP and NC have been chosen as independent variables and the influence of these variables on tensile, flexural and impact strength of the composite has been inspected. The permutations of the different combinations of factors are intended to accomplish higher interfacial strength with the lowest possible number of tested specimens. The experiments were designed by the Taguchi strategy and a novel multi-objective optimization technique named COPRAS (COmplex PRoportional ASsessment of alternatives) was used to determine the optimal parameter combinations. Affirmation tests were performed with the optimal parameter settings and the mechanical properties were evaluated and compared. Experimental results show that fiber GSM and eggshell powder content are significant variables that improve mechanical strength, while the nanoclay appears less important.     

Effect of solvents on electro-spinnability of polystyrene solutions and morphological appearance of resulting electrospun polystyrene fibers

The effects of solvents and their properties on electro-spinnability of the as-prepared polystyrene (PS) solutions and the morphological appearance of the as-spun PS fibers were investigated qualitatively by means of a scanning electron microscope (SEM). The eighteen solvents used were benzene, t-butylacetate, carbontetrachloride, chlorobenzene, chloroform, cyclohexane, decahydronaphthalene (decalin), 1,2-dichloroethane, dimethylformamide (DMF), 1,4-dioxane, ethylacetate, ethylbenzene, hexane, methylethylketone (MEK), nitrobenzene, tetrahydrofuran (THF), 1,2,3,4-tetrahydronaphthalene (tetralin), and toluene. The PS solutions in 1,2-dichloroethane, DMF, ethylacetate, MEK, and THF could produce fibers with high enough productivity, while the PS solutions in benzene, cyclohexane, decalin, ethylbenzene, nitrobenzene, and tetralin were not spinnable. Qualitative observation of the results obtained suggested that the important factors determining the electro-spinnability of the as-prepared PS solutions are high enough values of both the dipole moment of the solvent and the conductivity of both the solvent and the resulting solutions, high enough boiling point of the solvent, not-so-high values of both the viscosity and the surface tension of the resulting solutions.     

Synthesis of polystyrene/SiO2 composite microparticles by dispersion polymerization in supercritical fluid

A novel synthetic route to prepare polystyrene/SiO₂ composite microparticles in supercritical carbon dioxide (scCO₂) is presented. Silica particles with the size of 130 nm which were surface-modified with 3-(trimethoxysilyl) propyl methacrylate were used as seeds in the dispersion polymerization of styrene in the presence of a polymeric stabilizer, poly(1,1-dihydroheptafluorobutyl methacrylate-co-diisopropylaminoethyl methacrylate) to produce dry composite particles. The transmission electron microscopy analysis revealed that the composite microspheres contained several silica particles.     

Vibrational and electrical investigations of a uniaxially stretched polystyrene/carbon nanotube composite

Multiwall carbon nanotube (MWCNT)/polystyrene (PS) composite materials were prepared in the absence and in the presence of a surfactant. TEM analysis reveals the formation of chains made of several nanotubes tied up together upon application of the surfactant while an almost random distribution is observed without any treatment. These nanotubes are seen to be highly oriented in the uniaxially stretched composite. It is shown that the presence of the surfactant and the alignment reduce electrical conductivity while polymer chain orientation remains insensitive to these parameters.     

The influence of hematite nano-crystals on the thermal stability of polystyrene

A synthetic procedure based on thermal hydrolysis of iron(III) chloride solutions for the preparation of hematite (α-Fe₂O₃) sol consisting of nano-crystals (NCs) is described. The α-Fe₂O₃ NCs were characterized by transmission electron microscopy and X-ray diffraction measurements. Incorporation of α-Fe₂O₃ NCs into polystyrene (PS) was based on the transfer of α-Fe₂O₃ NCs from the aqueous phase to the organic solvent. A significant shift in the glass transition temperature of PS by 17 °C towards higher temperatures was observed after incorporation of α-Fe₂O₃ NCs. Also, the thermal stability of PS was improved by about 100 °C in the presence of 3.6 wt% of α-Fe₂O₃ NCs.     

Kinetics of the degradation of polystyrene in supercritical acetone

The kinetic analysis of the degradation of polystyrene (PS) in supercritical acetone has been studied using the nonisothermal weight loss technique with heating rates of 3, 5 and 7 °C/min. The weight loss data according to degradation temperature have been analyzed using the integral method based on Arrhenius form to obtain the kinetic parameters such as apparent activation energy and overall reaction order. The kinetic parameters obtained from this work were also compared with those of the thermal degradation of PS in nitrogen atmosphere. From this work, it was found that the activation energies of PS degradation in supercritical acetone were 73.3-200.7 kJ/mol and lower than those of the thermal degradation in nitrogen atmosphere.     

Effect of simple electrolytes on the hydrodynamic radius of polystyrene latex

We studied the salt concentration dependence of the diffusion constant of the highly charged and monodispersed polystyrene latex sphere using the techniques of dynamic light scattering. At extremely low ionic strength, the diffusion constant is smaller than that at the higher ionic strength by 10 % of the latter value. The addition of smal amount of N(CH₃) ₄ ⁺ to the latex solution increases the diffusion constant. These experimental results are explained by the change of the hydrodynamic radius which depends on sizes of the polystyrene core and the structural water surrounding it.     

A literature review on the in situ generation of reinforcing fibers

Liquid crystal polymers (LCPs) are a relatively new class of materials. These polymers usually consist of rigid rodlike molecular chains and they are capable of forming highly oriented structures even in the as-made product, with strength/modulus significantly higher than those of the conventional flexible chain polymers. Blending of LCPs with conventional polymers produces composite-like structures with LCPs serving as the reinforcing component. The properties of the blends are affected by the size, shape and distribution of the LCPs in the matrix polymer, which in turn are related to the processing conditions such as the blend composition, the extrusion and drawing conditions, the viscosity ratio of the component polymers and the type and grade of the LCPs and the matrix polymers. Improved processability of the blend due to the reduction in viscosity and the improved interfacial adhesion between reinforcing fibers and the matrix polymer are among the advantages of these materials over the conventional short fiber reinforced composites. This paper gives a brief review of the work currently available in the literature on rheology, fabrication, blend morphology and mechanical/thermal properties of the in situ composites from blends of LCPs and conventional polymers.     

Effective in situ synthesis and characteristics of polystyrene nanoparticle‐covered multiwall carbon nanotube composite

The higher surface area of selectively grown multiwall carbon nanotubes (MWCNTs) and the better proximity of the reactant species in in situ microemulsion polymerization were used to attach the polystyrene (PS) nanoparticles to the outer wall of MWCNTs. Attachment were achieved by replacing surfactant with PS nanoparticles. SEM showed that the MWCNTs and PS nanoparticles were distributed in the composite. High resolution transmission electron microscopy showed successful anchoring of PS nanoparticles to the outer wall of the MWCNTs. In addition, anchoring enhanced the Raman's G/D ratio of the MWCNT and degradation temperature in PS nanoparticles. A mechanism of attachment of PS nanoparticles on the outer wall of MWCNT was proposed. The modified MWCNTs exhibited good durability and dispersability in different organic solvents. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1523–1529, 2009     

Effect of processing on the environmental stress cracking resistance of high-impact polystyrene

Processing conditions have a strong effect on the final mechanical properties of products made of polymeric materials. Relevant phenomena most commonly include thermal stresses, physical ageing, frozen-in strains and molecular orientation. In this work, two different high-impact polystyrenes, processed by thermoforming, were considered: a “standard” one and a grade specifically resistant to Environmental Stress Cracking (ESC). The main effect induced by thermoforming was molecular orientation. The local degree of orientation was measured on a thermoformed product and its effect on the material ESC behavior in sunflower oil was studied. A Fracture Mechanics approach was applied to evaluate the fracture resistance of the two materials. Results show that a higher degree of orientation increases the fracture resistance in air but has no effect on the (expectedly lower) resistance in the active oil environment.     

Effects of CeO2 and CaO composite promoters on the properties of eggshell Ni/MgO-Al2O3 catalysts for partial oxidation of methane to syngas

The effects of CeO₂ and CaO composite promoters on the properties of eggshell Ni/MgO-Al₂O₃ catalysts of 1.5 mm diameter for the partial oxidation of methane to syngas were investigated. The addition of 1wt.% promoters could enhance the catalytic performance of the Ni/MgO-Al₂O₃ catalyst, while further increasing the promoter content to 4wt.% results in the decrease of reactivity. The catalytic property is related to the oxidizability of surface nickel species.