Physical properties and application development of recycled products from waste plastics

The degradation of the physical properties of polypropylene (PP) used for automotive outer trims for several years is unexpectedly small. It, therefore, can be fully anticipated that PP so used can be recycled for the same purpose or for other applications.     

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.     

Recycling of mixed automotive plastics

Mixed plastics from junked autos were homogenized by milling or extrusion, modified by addition of low-molecular-weight low-melt-viscosity polymers, and processed by compression or injection molding. Properties were comparable with high-density polyethylene and common building panel materials.     

Rheological and mechanical properties of ABS plastics prepared by bulk polymerization

A series of ABS plastics prepared by bulk polymerization was studied. The test samples contained almost equal amounts of PB but mostly differed in the molecular mass of a styrene-acrylonitrile copolymer. It was shown that the molecular mass of the copolymer strongly affects the rheological and mechanical properties of ABS plastics. An increase in molecular mass leads to a rise not only in the non-Newtonian viscosity of plastics but also in their yield point, storage modulus under periodic steady-state shear flow in the low-frequency plateau region, and impact strength. Quantitative correlations between these rheological and mechanical characteristics of the copolymers and their M _w values were established. As opposed to homophase polymer systems, a marked increase in the shear stress has no effect on viscosity in relation to the molecular mass of ABS plastics. In the case of melts, the influence of the M _w of the styrene-acrylonitrile copolymer on the rheological behavior of ABS plastics is apparently related to a change in the interaction of PB particles with the copolymer that controls the structural framework of the system. The relationship between the impact strength of the copolymer and its M _W may be explained by the fact that the latter parameter influences orientational effects in crazes that arise during steady-state shear flow of ABS plastics in the solid state.     

Multiaxial mechanical testing of plastics

This paper outlines the many problems associated with the testing of plastics and suggests a method of minimising these problems by the use of multiaxial testing techniques. It extends the multiaxial approach into the determination of the fatigue loading characteristics of a plastic. General design criteria of such machines, as well as details of a family of machines that have been developed for that purpose, are given.     

Compatibilization and impact modification of mixed recycled plastics

In order to solve the problems related to the reuse and recycling of polymer materials, approaches must be developed to address the incompatibility of most plastics. In many cases, the complete separation of dissimilar plastics may not be economically feasible or technologically possible, so commingled plastics recycling may be the only option. Our work has concentrated on upgrading the performance of a blend of two incompatible polymers. For this, we have used a model composition of two plastics commonly found in business machine housings. Our approach concentrates on compatibilization of the blend with a tailored copolymer, in addition to impact modification of the different phases. Improvements in mechanical performance of the blends are elucidated through the use of transmission electron microscopy.     

Effect of the mechanical activation of nepheline concentrate on its binding properties in mixed cements

Binding properties of a Portland cement-nepheline-water formulation were studied in relation to its nepheline content by using a preliminary mechanical activation. A thermal analysis was used to estimate the hydration rate of cement phases in the system under study. The accelerating role of nepheline in hardening of mechanically activated Portland cement-nepheline formulations was revealed and found to be more pronounced in early stages. The gain in the strength of the cement stone was analyzed in relation to the formulation composition and hardening duration.     

Removal of fission products from mixed solvents using zeolites

The solvents tributylphosphate (TBP) and odourless kerosene (OK) are widely used to extract plutonium(IV) and uranium(V) in nuclear processing plants. Although these solvents are chosen because of their low affinity for fission products it is, nevertheless, of value to study ways of removing the small quantities of fission products, such as isotopes of Cs, Sr and Ru, which can be present in the solvents. This paper describes simple distribution coefficients (K _d) measurements made to test the ability of the aluminosilicate zeolites to remove¹⁰⁶Ru from TBP, OK, and their mixtures.     

Analysis of products from the pyrolysis of plastics recovered from the commercial scale recycling of waste electrical and electronic equipment

Three plastic fractions from a commercial waste electrical and electronic equipment (WEEE) processing plant were collected and investigated for the possibility of recycling them by batch pyrolysis. The first plastic was from equipment containing cathode ray tubes (CRTs), the second plastic was from refrigeration equipment, and the third plastic was from mixed WEEE. Initially, the decomposition of each of the plastics was investigated using a TGA linked to a FT-ir spectrometer which showed that the CRT plastic decomposed to form aliphatic and aromatic compounds, the refrigerator plastic decomposed to form aldehydes, CO₂, aromatic, and aliphatic compounds, and the mixed WEEE plastic decomposed to form aromatic and aliphatic compounds, CO₂, and CO. Each plastic mixture was also pyrolysed in a batch reactor to determine the halogen and metal content of the pyrolysis products, additionally, characterisation of the pyrolysis oils was carried out by GC–MS and the pyrolysis gases by GC–FID and GC–TCD. It was found that the halogen content of the oils was relatively low but the halogen and metal content of the chars was high. The pyrolysis oils were found to contain valuable chemical products and the pyrolysis gases were mainly halogen free, making them suitable as a fuel.     

Relationship between swelling and mechanical properties of cross-linked polymers mixed with sand

Cross-linked polymers consisting of acrylamide, sodium acrylate, starch fragments and a cross-linker were synthesized with the same content of carboxyl groups and three degrees of cross-linking Q of 0.04, 0.2 and 1 wt%. An increase in Q gradually reduces the swelling of polymer gels in water; when distributed in sand, polymer gels exhibit maximum swelling at Q = 0.2 wt%. It is shown that the behavior of polymer gels in sand is determined by the balance between the elasticity of swollen polymer gels and the resistance of sand particles     

Effect of the chain-length compatibility of surfactants and mechanical properties of mixed micelles on surfaces

Force/distance curves for silicon nitride tip/flat silica or alumina coated by a layer of mixed micelles of cationic/anionic surfactant are measured by using AFM. Mixtures of SDS/C(n)TAB (with molecular ratios of 3:1 and 20:1) and C(n)TAB/SDS (with molecular ratio of 85:15) were used for alumina and silica substrates, respectively. The number of carbon atoms per C(n)TAB molecule, n, was in the range of 8 to 16. On the basis of the force/distance curves, the elastic modulus, E, and yield strength, Y, of surface micelles are calculated. It is shown that in surfactant mixtures containing SDS the maximal repulsive force (the barrier F(bar)) at which the tip punctured the micelles, as well as the magnitudes of E and Y, attained the maximal values for C(12)TAB ( i.e., when the hydrocarbon chain lengths of two oppositely charged surfactants are the same). Obviously, it can be related to the highest density structure of these micelles. Note that the literature data for the surface micelles from pure C(n)TAB solutions demonstrate a monotonic dependence of F(bar), E, and Y on n in the range of n = 8-16, whereas the oppositely charged mixed surfactant systems yield much higher values of F(bar), E, and Y than does an equivalent chain length from the homologue series plots. The results obtained for mechanical characteristics of mixed micelles at the surface are compared with the results for the relaxation time, tau(2), that characterizes the lifetime (and therefore structure) of the bulk micelles. Both the dependence of F(bar), E, and Y on n for the surface mixed micelles and tau(2) on n for the bulk mixed micelles demonstrate a maximum at n = 12 for the C(n)TAB + SDS system. This correlation between properties of the surface and bulk micelles suggests that the mechanical properties of the surface micelles are largely determined by the interactions between surfactant molecules with surfactant-substrate interactions playing a secondary role.     

Effect of the mechanical activation of baddeleyite concentrate on its binding properties in the composition of mixed cements

The binding properties of the baddeleyite concentrate mechanically treated with the use of Portland cement and alumina clinkers as activator were studied.     

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.     

Radiation-induced degradation of polyethylene: Role of amorphous region in the formation of oxygenated products and the mechanical properties

Quenched samples of linear low density, medium density and two kinds of high density polyethylene films were irradiated with γ-rays from a ⁶⁰Co source in vacuum and in air at room temperature with irradiation doses ranging from 0 to 100 Mrad. On irradiation in vacuum the extent of crosslinking was about one-and-a-half times greater in the linear low density polyethylene (LLDPE) than in the high density polyethylene (HDPE). On the other hand, irradiation in air produced more crosslinking in high density polyethylene (HDPE). Growth of trans-vinylene unsaturation was found around 10 Mrad in all the samples. Initial increase in elongation and breaking strength (below 5 Mrad) occurred, which was followed by a decrease with increasing dose. LLDPE showed some elongation even at 50 Mrad, while the other samples became brittle and broke at doses far below this value. The mechanism of oxidative degradation is discussed.     

Effects of photoaging on the tribological properties of engineering plastics

Ball‐on‐disk tests were performed to investigate the effects of photoaging on the tribological properties of engineering plastics under dry sliding. Results exhibit that different molecular structures of plastics result in different aging morphologies, and ultra high molecular weight polyethylene has better resistance to photoaging than polyformaldehyde (POM). However, POM has better wear resistance before and after the photoaging. Marked increase of the width and depth of wear tracks is observed after aging. Analysis of worn surface has revealed that photoaging significantly affects the wear mechanism of ultra high molecular weight polyethylene and POM. Although the major wear mechanism before the aging of materials is identified as plastic deformation and adhesive wear, it becomes quite complicated when the materials experienced photoaging. Such complex wear mechanism hence deteriorates the tribological performance of the engineering plastics. Copyright © 2014 John Wiley & Sons, Ltd.     

用木粉制备生物降解塑料的探讨

本文报道以木粉制备生物降解塑料的工艺，以及该塑料的机械性能和生物降解性能等情况。在摸索出的样品组成及加工工艺条件下制备的样品，其拉伸强度为5MP左右，冲击强度为2.0kJ／m~2左右。并具有一定的生物降解性能，在三个月内降解失重率为15％左右。     

机械活化木薯淀粉氧化产物的结构表征

采用搅拌球磨机对木薯淀粉进行机械活化,以活化60min的木薯淀粉为原料,CuSO4为催化剂,H2O2为氧化剂干法制备氧化淀粉。利用红外光谱、扫描电子显微镜、X-射线衍射等手段对产物的结构进行表征分析,并与原淀粉的氧化产物进行比较。结果表明,机械活化对木薯淀粉的氧化反应有显著的影响。原木薯淀粉的氧化反应主要发生在淀粉颗粒的表面及无定形区,部分发生在结晶区,产物是无定形及结晶状态的结构;活化淀粉的氧化反应在淀粉团粒表面及内部均匀进行,产物是无定形的聚集状态结构。并就机械活化对淀粉氧化的强化机理进行了探讨。     

Atomic force microcopy study of the mechanical and electrical properties of monolayer films of molecules with aromatic end groups

The effect of intermolecular pi-pi stacking on the electrical and mechanical properties of monolayer film molecules containing aromatic groups was studied using atomic force microscopy. Two types of aromatic molecules, (4-mercaptophenyl) anthrylacetylene (MPAA) and (4-mercaptophenyl)-phenylacetylene (MPPA), were used as model systems with different pi-pi stacking strength. Monolayer films of these molecules on Au(111) surfaces exhibited conductivities differing by more than 1 order of magnitude, with MPAA being the most conductive and MPPA being the least conductive. The response to compressive loads by the AFM tip was also found to be very different for both molecules. In MPAA films, distinct molecular conductivity changes are observed upon mechanical perturbation. This effect, however, was not observed on the MPPA film, where intermolecular pi-pi interactions are likely weaker.     

Size-exclusion chromatography of the soluble lignin products from hydrogen peroxide brightening of mechanical pulps

The molar mass distributions and yields of soluble lignin degradation products formed during the alkaline hydrogen peroxide brightening of spruce mechanical pulp have been determined. These distributions depend on pH, the extent to which the pulp was subjected to solvent extractions, H₂O₂ concentration and reaction time. At and below pH 11, there is an excellent correlation between the brightness and b values on pulp and the amounts of residual peroxide and lignin derived products in solution. Brightening reactions lead primarily to products with intermediate molecular mass values between 1500 and 6000. During multistage brightening, the products formed are initially those with high ionizable phenolic hydroxyl and low carbohydrate contents, and carbonyl-containing moieties. NMR and UV spectroscopic analysis show that products formed include lignin and carbohydrate-containing species. The lignin-originating products from the later stages contain a lower relative concentration of ionizable phenolic groups and more visible-absorbing and carbohydrate-containing species. Brightness and b gains during multistage brightening were exponential with product yield.