Catalytic degradation of the mixed polyethylene and polypropylene into middle distillate products

Mixture of polymers (HDPE/LDPE/PP) was pyrolyzed over a silico-alumina catalyst using a laboratory semi batch reactor operating isothermally at ambient pressure. The experiments discussed in this work show that the use of catalyst provides proper selectivity in the liquid product distributions and improves the yield of light hydrocarbon productions. The liquid samples were analyzed using GC/FID to find out their composition. The liquid collected at optimum condition (420 °C, 40 cat/pol ratio) was distilled at different temperatures to discretize light and heavy fractions. Octane number, color, Reid vapor pressure, specific gravity, and density are further analyses which done to determine extra physicochemical properties of the liquids at optimum reaction condition. Also, results compared with the physical properties of commercial gasoline which imply that the liquid somewhat matches with standard gasoline. By using Arrhenius’s law, a kinetic model at optimum reaction conditions has been developed and activation energy determined. The reaction follows the first-order kinetic rate relationships. This model equation gives a suitable match with experimental results.     

Application of Taguchi approach to optimize friction stir spot welding parameters of polypropylene

This paper shows experimental and numerical results of friction stir spot welding of high density polypropylene. The determination of the welding parameters plays an important role for the weld strength. The experimental tests, conducted according to combinations of process factors such as tool rotation speed, plunge depth and dwell time at beginning welding, were carried out according the Taguchi orthogonal table L9 in randomized way. The Taguchi approach was used as a statistical design of experiment technique to set the optimal welding parameters. The results show coherence between the numerical predictions and experimental observations in different cases of weld strength. The signal-to-noise ratio and the analysis of variance were utilized to obtain the influence of the friction stir spot welding parameters on the weld strength. Finally, the improvement in the weld strength from the initial welding parameters to the optimal welding parameters was about 47.7%.     

A new insight into the Taguchi method.

To obtain high quality products at low cost and in a short time is an economical and technological challenge to today's engineering community. Design of Experiments based on the Taguchi approach is a powerful technique to attain this objective. In some processes, it is necessary to consider not only two factors but also the ratio of their levels 'as a factor.' This paper introduces a new look at the Taguchi method that makes it possible, by choosing the proper levels, to evaluate the ratio of two factors as a new factor in the same orthogonal array. An experiment to study four three-level factors was designed, and a case study is presented to illustrate the ratio of the two three-level factors as a new factor using the same L9 orthogonal array.     

Effects of gamma irradiation on polypropylene, polypropylene + high density polyethylene and polypropylene + high density polyethylene + wood flour

The effect of the gamma-irradiation on the mechanical properties of the composites, Polypropylene (PP), PP+high density Polyethylene (HDPE), PP+ HDPE+wood flour, where HDPE is virgin and recycled, was studied. This paper discusses the behavior of the composites after exposure to various doses of gamma irradiation (1–7 MRads) in the presence of oxygen. The dependence of mechanical properties on the integral dose for a constant dose rate of 0.48 MRads/h confirms the influence of the irradiation. Strong effects on the elongation at break and break strength is noticed. The mathematical analysis suggests for the PP+r-HDPE a bimolecular process of the elongation at break. On the order hand, for the PP+HDPE a complex process is represented for a three exponential equation. Received: 9 October 2000 / Reviewed and accepted: 10 October 2000     

Creep behaviour of polyethylene and polypropylene

Tensile creep tests and stress reduction studies during creep have been carried out for polyethylene and polypropylene. The results obtained suggest that a consistent approach for the presentation of creep data for these polymeric materials can be obtained since the creep curves at 293K for polyethylene and polypropylene over a wide stress range can be superimposed by describing the variation of creep strain,, with time,t, as= ₀ + _p [1 – exp (–K t)] + t, where ₀ is the initial strain on loading, _p is the primary creep strain, is the secondary creep rate, andK is a constant.     

Molecular model of drawing polyethylene and polypropylene

Morphological studies of plastic deformation of single crystals, thin layers, and bulk samples together with mechanical, X-ray and infra-red data revealed the existence of three stages in cold drawing of crystalline polymer: the plastic deformation of the original spherulitic structure, the discontinuous transformation of the spherulitic into fibre structure by micronecking, and the plastic deformation of the fibre structure. The initial material, which has low strength and high ductility, consist of stacks of parallel lamellae with few interlamella links. It deforms plastically by stack rotation, sliding of lamellae, phase change and twinning of crystal lattice, chain slip and tilt until the predeformed lamellae reach the position of maximum compliance for fracture by micronecking. The micronecks transform every single lamella into microfibrils of between one and three hundred angstroms in width, consisting of folded chain blocks broken off the lamella primarily by chain slip in the boundary layers between adjacent mosaic blocks. The chains bridging the crack are partially unfolded during the micronecking process. They connect in axial direction the blocks in the microfibril as intrafibrillar tie molecules. The number of microfibrils per cm of crack length increases with molecular weight. The draw ratio of the microfibrils and the axial separation in the microfibril of the originally adjacent crystal blocks increase with the average distance between microfibrils and, hence, decrease with increasing molecular weight. The concentration of micronecks in every stack of lamellae in a thin destruction zone produces a bundle of microfibrils of rather uniform draw ratio. Such a fibril measuring a few thousand angstroms in width includes the interlamella ties of the original sample as interfibrillar tie molecules connecting adjacent microfibrils. The concentration of micronecks also provides the conditions for a nearly adiabatic heating of the generated fibril by the transformation work in the destruction zone. The local temperature rise imparts so much mobility to the chains in the crystal blocks that during subsequent cooling to ambient temperature, the long period becomes adjusted to this temperature. The more or less random distribution of destruction zones in the neck makes the transformation from spherulitic to fibre structure appear to be a gradual process in spite of the discontinuous transformation in the micronecks. The plastic deformation of the new fibre structure can proceed only by longitudinal sliding of microfibrils past each other, a process limited by interfibrillar tie molecules. Hence, high molecular weight samples with many interlamella links exhibit a smaller draw ratio than lower molecular weight material. The three stages are to some extent intermixed in the neck. In the initial neck characterised by a low draw ratio and rather gentle constriction, the transformation into the fibre structure is not complete, so that some of the remains of the original microspherulitic structure are still present in the necked portion. They are destroyed during subsequent drawing which completes the transformation and also deforms the fibre structure. The sharply constricted mature neck, however, yields a high draw ratio which is composed of the draw ratio of microfibrils and of subsequent sliding motion of the microfibrils. The technically important natural draw ratio is the maximum draw ratio obtained with the sample under the conditions of the experiment. It seems to be higher than the draw ratio of the microfibrils.     

氧弹燃烧法测定聚乙烯和聚丙烯材料中的微量卤素

试样通过氧弹燃烧的方法,采用离子色谱仪测定卤素含量,准确可靠地定量聚乙烯和聚丙烯类材料中的微量卤素。4个元素的标准曲线线性相关性良好,相关系数为0．99997、0．99969、0．99940和0．99954,各6次的重复进样结果表明此法测定F-、CI-、Br和l-的相对标准偏差均〈5％。     

High efficiency degradation of 4-nitrophenol by microwave-enhanced catalytic method

Application of the microwave-enhanced catalytic degradation (MECD) method on the abatement of 4-nitrophenol (4-NP) using nickel oxide was studied. A mix-valenced nickel oxide was prepared from nickel nitrate aqueous solution through a precipitation with sodium hydroxide and an oxidation by sodium hypochlorite with/without microwave-assisted heating. They were characterized by X-ray (XRD), infrared spectroscopy (IR), temperature programmed reduction (TPR), and transmission electron micrographs (TEM). Their catalytic activities towards the degradation of 4-NP were investigated through continuous bubbling of air during the liquid phase and evaluated quantitatively with high pressure liquid chromatography (HPLC). Also, the effect of the kinds of catalyst, temperature, pH, initial concentration, and dosage of catalyst on the efficiency of 4-NP degradation was investigated. The results showed that the 4-NP was completely degraded using the high efficiency MECD method within 15 min under [H(+)] = 1.0M, T = 40 °C, and C = 200 ppm over nickel oxide.     

废聚丙烯制取汽柴油馏分技术研究

采用热裂解、热裂解-催化改质、催化裂解等方法将废聚丙烯制成汽、柴油馏分。研究发现废聚丙烯垃圾可以不经过任何处理直接作为裂解原料制取油品。分析了不同工艺条件下的汽油馏分及气体组成,测定了汽油馏分的辛烷值以及柴油馏分的十六烷值,并对三种方法进行了技术评价,认为热裂解-催化改质是最为实用的油化方法。     

成核剂改性聚丙烯共混体系的研究

用偏光显微镜和DSC研究了几种成核剂对聚丙烯共混体系结晶形态、结晶度、结晶温度的影响.结果表明,成核剂4030的加入,使共混体系的结晶度最大,成核剂d(自制)的加入使共混体系的最高结晶峰温度最低,也使制品收缩率最大.     

The permeation resistance of polyethylene, polyethylene/polyamide and polyethylene/modified polyamide blown tubes against unleaded gasoline

The barrier resistance of polyethylene (PE), polyethylene/polyamide (PE/PA) and polyethylene/modified polyamide (PE/MPA) blown tubes against gasoline permeation is reported. The blown tubes prepared from pure PE exhibited much poorer gasoline permeation resistance than PE/PA and PE/MPA blown tubes. About 93% of the filled gasoline permeated out of PE blown tubes in 14 days at 40°C. In contrast, the gasoline permeation resistance of the blown tubes improved significantly by blending MPA (or PA) before tube blowing. PE/MPA blown tubes exhibited significantly better gasoline permeation resistance than PE/PA blown tubes of the same PE contents. The order of gasoline permeation resistance of PE/MPA blown tubes is the same as the order of the barrier resistance of MPA resins against gasoline permeation before blending with PE. In fact, by using proper compositions and carefully controlling the MPA morphology, the gasoline permeation resistance of the PE/MPA blown tubes can reach about 360 times better than that of pure PE blown tubes at 25°C. These interesting phenomena were investigated in terms of the morphology, thermal and rheological properties of the base resins and/or blown tubes of PE/PA and PE/MPA blends.     

Epitaxial crystallization of high-density polyethylene on polypropylene in solution-cast films

Epitaxial crystallization of high-density polyethylene (HDPE) on isotactic polypropylene (iPP) in solution-cast films has been investigated by electron microscopy. The specimen-tilt technique of electron microscopy has been used to study the structural relationship between HDPE and iPP crystals. HDPE exhibits different crystalline morphologies in the two basic types of iPP spherulite textures, cross-hatched and lathlike regions. In the former, the crystallographic c axis of HDPE lamellae is in the film plane, while in the latter, the c axis of HDPE crystallites is at an angle of about 50 with the normal of the film. In both structural regions of iPP, however, the contact planes of epitaxial growth are (010) for iPP and (100) for HDPE.     

Importance measure method for error sources of degradation systems based on the present worth of expected Taguchi quality loss

Deteriorating of the error sources and the deviation of the quality characteristic (QC) of the product from the target value are ubiquitous in practice. Studying the relative contribution of the error sources to the QC deviation is helpful for improving the product performance effectively. In this study, we propose an error importance measure (EIM) method to quantify the relative contribution of error sources to the Taguchi quality loss that is caused by the QC deviation. The present worth of the expected Taguchi quality loss (ETQL) is used to characterize the deteriorating QC deviation. We use Taylor series expansion to decompose the time-dependent ETQL and the present worth of ETQL into a series of fractions, representing the individual and the interaction contributions of the error sources. Based on the decomposition, the time-dependent and the time-independent EIM indices for one and a group of error sources are defined, respectively. The evaluation procedure for the EIM indices is provided and the properties are discussed. Finally, we provide a realistic application case to an aircraft wheel door mechanism to demonstrate the effectiveness of the proposed EIM method.     

On the internal morphologies of high-modulus polyethylene and polypropylene fibres

High modulus polyethylene fibres, both melt and gel-spun, contain the same longitudinal density deficient regions, revealed by permanganic etching, as were found in specimens of the same fibres after treatment by the Leeds high temperature compaction process. For these materials a new model of fibre structure is proposed, which develops as a consequence of nucleation on an extended network of entangled molecules permeating the fibres. Subsequent growth into spaces between the network will encounter stresses due to the contraction on crystallization leading to distributed density deficient regions of high free volume. Each of the four commercial PE fibres examined differs from the others in its characteristic outline and the details of its internal substructure. The structure of commercial polypropylene fibres is also compared.     

An experimental study on conversion of high-density polyethylene and polypropylene to liquid fuel

Clean Technologies and Environmental Policy - Pyrolysis of plastic material is a potential way for the conversion of plastic into hydrocarbon fuel. Thermal and catalytic pyrolysis of high-density...     

Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon

A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels.     

Thermo-mechanical characteristics of thermally aged polyethylene/polypropylene blends

Polyethylene (PE), polypropylene (PP) and their blends have attracted a lot of attention due to their potential industrial applications. Therefore, the current work has been carried out with the main objective of investigating the impact of the thermal aging/treatment and blend ratio (composition range) on the mechanical (tensile and hardness) and thermal characteristics (using thermogravimetric analysis in a dynamic air atmosphere) of PE, PP and PE/PP binary blends. Samples of PE/PP blends containing 100/00, 75/25, 50/50, 25/75 and 0/100 wt.% were prepared via injection moulding technique and thermally treated/aged at 100 °C for 0, 2, 4, 7, 14 days. The tensile measurements indicated that the yield strength and the modulus decrease with increasing PE content. It was also observed that PE, PP and their blends deform in ductile modes. They undergo a uniform yielding over a wide range of deformation, which is followed by strain hardening and then failure. The strain to break for pure PE is found to be much higher than that for pure PP and for their blends, intermediate values have been observed. The hardness measurements have also revealed that increasing PE content in PE/PP blends reduced the hardness value of PP, however, thermal aging at 100 °C has not affected the polymers hardness which holds also true for the tensile properties, showing a good correlation between tested mechanical properties. The thermogravimetric analysis (TGA) in a dynamic air atmosphere and derivative thermogravimetric analysis (DTA) were conducted to study the thermal degradation and stability of thermally unaged and aged PE, PP and PE/PP blends in terms of the initial (T_d and T_d(1%)) and final (T_d(99%)) decomposition temperatures and maximum decomposition rate temperature (T_max). All polymers start to decompose at no less than 365 °C. As for mechanical properties, the blend ratio has affected the thermal properties however, aging time has not.     

The plastic deformation of oriented polypropylene and polyethylene: deformation mechanisms

Polypropylene and high-density polyethylene, oriented by hot drawing, have been tensile testedin situ in a low angle X-ray camera. Two orientations of polypropylene, ₀=31° and ₀=60°, and one orientation of polyethylene, ₀=30°, were examined. ( ₀ is the initial angle between the tensile axis and the molecular axis.) Low-angle and wide-angle X-ray patterns were taken at successive stages of increasing strain up to approximately 100%. The rotations of the molecular axis and lamellar normal for both materials oriented near ₀=30° were quantitatively consistent with predominantly intermolecular shear, occurring within the lamellae. In the case of polypropylene, it is proposed that small amounts of interlamellar and interfibrillar shear were also present.At ₀=60°, the polypropylene was shown to deform by void opening or fibril separation, followed by intermolecular shear. The behaviour of polypropylene was consistent with the yield criterion based on a fibre reinforced composite model which was presented in a previous paper [1].     

基于田口方法的橡胶砂浆受风沙冲蚀性能

针对内蒙古中西部风沙环境特征,利用模拟风沙环境侵蚀实验系统,采用L₁₆（5⁴）田口方法进行实验设计,研究了不同橡胶粒径和掺量的橡胶砂浆在风沙环境下的冲蚀磨损行为,应用SEM观测橡胶砂浆冲蚀后的微观形貌。结果表明：在冲蚀速度为17 m/s、橡胶粒径为1.70 mm、橡胶掺量为5%、冲蚀角度为45°和下沙量为45 g/min的条件下,橡胶砂浆的冲蚀率最小;下沙量和冲蚀速度是影响橡胶砂浆冲蚀磨损性能的显著因素;相同冲蚀条件下,各粒径的橡胶砂浆冲蚀率大小为：1.70 mm的橡胶砂浆 < 普通水泥砂浆 < 0.18 mm的橡胶砂浆 < 0.42 mm的橡胶砂浆;橡胶砂浆的冲蚀磨损主要体现为沙粒对其表面的切削和挤压作用,其中1.70 mm的橡胶颗粒对沙粒有较好的抵抗作用,0.42 mm的胶粉颗粒易剥落,加剧沙粒的磨损作用。     

Reinforcement of polyethylene with polypropylene by a blending and deformation process

The blending of polymers to achieve either unique or intermediate properties has become a rather common practice. High density polyethylene (HDPE) and isotactic polypropylene (PP) are immiscible in the melt state and phase segregate. This behaviour and their difference in melting point (132 against 165° C) has been exploited to produce a uniaxial reinforcement of HDPE with PP fibres by a process of melt blending, and tensile drawing followed by annealing. Tensile drawing of the blends results in the transformation of each phase to a fibrous structure having an increased modulus and tensile strength. The annealing of this material to melt and recrystallize the HDPE converts it to a lower modulus ductile lamellar structure which is reinforced with the fibrous PP regions. Both the modulus and tensile strength in the fibre direction fit simple composite theory for isotropic HDPE filled with higher modulus PP fibres over the entire composition range.