Das Versagen von Polymeren unter Belastung mit konstanten Dehngeschwindigkeiten

Zusammenfassung Der Bruch oder das Erreichen der Streckgrenze eines Polymeren ist ein Versagensphänomen, das unter konstanten Umgebungsbedingungen von der Belastungsgeschichte abhängig ist. Versuche mit konstanten Dehngeschwindigkeiten ergeben bei zunehmenden Dehngeschwindigkeiten eine eindeutige Zunahme der dem Versagenspunkt entsprechenden Spannung und Dehnung. Der Vergleich experimenteller und rechnerischer Ergebnisse zeigt, daß die Hypothese der konstanten dissipierten Verformungsenergie, die schon früher erfolgreich für die Rißbildung unter Kriech- und Spannungsrelaxationsbelastung angewendet wurde, auch als Kriterium des Versagens von Polymeren unter Belastung mit konstanten Dehngeschwindigkeiten geeignet ist.

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Summary Fracture or yielding are failure phenomena which, at constant environmental conditions, depend upon the loading history of the considered polymer. Experiments with different constant strain rates have shown that the increase of the strain rate leads to an increase of both strain and stress of the failure point. A comparison of experimental and computational data shows that the hypothesis of constant dissipated energie, which has been applied earlier with success for the crazing of polymers in creep and stress relaxation, is also suitable as a criterion of the failure of polymers under loading with constant strain rates.

Mit 7 Abbildungen und 1 Tabelle     

Plastics as Optical Materials

The Principal material used in optics is glass. Plastics can only gain acceptance in optics if they have properties not encountered with glass or if a desired article can be produced more rationally from a plastic. An example of the first case is provided by UV light guides consisting of a quartz glass core surrounded by a plastic cladding; there is no glass with a sufficiently low refractive index. Examples of the second case are viewfinder optics for camerás and lenses for sunglasses and industrial safety spectacles.     

塑料中邻苯二甲酸酯类化合物的高效液相色谱分析

采用高效液相色谱法对塑料制品中的邻苯二甲酸酯类化合物进行了测定。塑料样品经粉碎后，用乙醇溶解后超声提取，直接用高效液相色谱分析，外标法定量。该方法精密度1．07％～1．98％，回收率76．0％～96．0％。此方法简便、易行，分离度较好，可作为测定塑料制品中增塑剂邻苯二甲酸酯类的方法。     

The effects of ageing by ultraviolet degradation of recycled polyolefin blends

Products manufactured from recycled polyolefin blends were subjected to accelerate weathering conditions and subsequent tests. Field-aged products were also tested.Samples were analysed for changes in mechanical, rheological and chemical properties. Data obtained in this study, by means of tensile, impact, and melt flow tests, GPC, gloss and colour analyses showed that the effect of UV exposure, whether in the field or artificial environments, was not significant as far as the mechanical properties of the materials were concerned. There was some change in the surface characteristics but such surface effects would not compromise the mechanical integrity of the product when recycled. During reprocessing of the materials, it is likely that stabilizer is redistributed at the surface of any new moulding, thus renewing the surface characteristics. Hence damaged or end-of-life products need not be discounted from recycling.     

ICP-AES法测定地质样品中的金

在 2 0 % (V/ V)王水介质中 ,用聚醚型泡沫塑料对金进行分离富集。以 1.0 % (W/ V)硫脲溶液解脱吸附在泡沫塑料上的金 ,解脱液中的金直接用 ICP- AES法测定。检出限为 0 .0 1× 10 -4 %。本方法简便、快速 ,用于测定地质样品中的金 ,结果与 AAS法相符     

Catalytic efficiency of some novel nanostructured heterogeneous solid catalysts in pyrolysis of HDPE

In the present study, the catalytic conversion of high density polyethylene (HDPE) to useful products has been investigated in the presence of BaTiO₃ based catalysts in a micro steel reactor at 350 °C and 30 min reaction time. The catalysts, including BaTiO₃, Pb/BaTiO₃, Co/BaTiO₃ and Pb–Co/BaTiO₃ were prepared in the laboratory by reactive calcination method and characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-rays (EDX), Surface Area Analyzer (SAA) and X-rays Diffractometry (XRD). The product yields (over all yields and yields of liquid, gas and coke/residue) as a function of individual catalyst concentration was studied. The result indicated a promising effect of the catalysts used on conversion to liquid products and their composition in term of carbon range (C₆ – >C₃₀) & hydrocarbon group types (paraffin's, olefins, naphthenics, and aromatics). Among the catalysts used, Pb–Co/BaTiO₃ gave the maximum yield of liquid products (86%) when used in 1 wt % loading. The same catalyst gave the average yield (20–25%) of different range hydrocarbons i.e. C₆–C₁₂, C₁₃–C₁₆, C₁₇–C₂₀ and C₂₀–C₃₀. Inversely, the un-doped BaTiO_3, favored the formation of C₆–C₁₂ and C₁₃–C₁₆ range hydrocarbons, whereas Pb doped BaTiO₃ and Co doped BaTiO₃ enhanced the yield of C₁₃–C₁₆, and C₂₀–C₃₀ range hydrocarbons. Regarding the hydrocarbon group types, all catalysts significantly increased the formation of paraffins and reduced olefins and naphthenes.     

Surface modification of plasticized PVC by dry cleaning methods: Consequences for artworks

A study of dry cleaning methods for plasticized PVC has been undertaken using three commercial cloths recommended for plastics artworks, in addition to cotton swabs traditionally used in art conservation. The evaluation of the cleaning has focussed on the efficiency of the cleaners, and the physical and chemical damages caused by the cleaning. The physical and chemical modifications of the PVC surface have been studied by optical microscopy, non-contact profilometry and ATR-FTIR spectroscopy, while spectrocolorimetry and non-contact profilometry have been used for evaluating the cleaning efficiency. The results have shown that the cleaner's composition and the cleaning time play an important role in damaging the plasticized PVC surface. On the contrary, it has not been completely determined if the texture of the cleaning agents’ surface had an influence on the cleaning efficiency.     

微波消解-等离子体发射光谱法测定塑料中铅元素和测定方法不确定度评定

用微波消解-等离子体发射光谱法测定塑料中铅元素.检测限为10.2ng/mL.测定方法的相对标准偏差在1.10%和2.71%之间,回收率在96.2%和99.1%之间.根据欧洲分析化学组织(EURACHEM)的不确定度数学模型,采用测定方法的精密度和回收率数据计算,扩展不确定度为测定结果的0.056.     

Accurate measurement of bromine contents in plastic samples by instrumental neutron activation analysis

Accurate measurements of bromine contents in plastic samples were made by the direct comparator instrumental neutron activation analysis (INAA). Individual factors affecting the measurements were comprehensively evaluated and compensated, including the volatility loss of bromine from standard comparators, the background bromine level in the filter papers used for preparation of the standard comparators, nuclear interference, γ-ray spectral interference and the variance among replicates of the samples. Uncertainty contributions from those factors were thoroughly evaluated and included in the uncertainty budgeting of the INAA measurement. ⁸¹Br was chosen as the target isotope, and the INAA measurements for bromine were experimentally confirmed to exhibit good linearity within a bromine content range of 10–170 μg. The established method has been applied to the analysis of eight plastic samples: four commercially available certified reference materials (CRMs) of polyethylene and polystyrene and four acrylonitrile butadiene styrene (ABS) samples prepared as the candidate reference materials (KRISS CRM 113-01-012, -013, -014 and -015). The bromine contents of the samples were calculated at three different γ-ray energies and compared, showing good agreement. The results of the four CRMs also showed good consistency with their certified values within the stated uncertainties. Finally, the bromine contents of the ABS samples were determined with expanded uncertainties (at a 95% level of confidence) between 2.5% and 5% in a bromine content range of 25–900 mg kg⁻¹.     

Monitoring of residual stresses in injection-molded plastics with holographic interferometry

Residual stresses are often trapped in injection-molded plastic parts due to the rapid cooling of the material in this manufacturing process. These stresses are a common source of failure in plastic components in automobiles, appliances and computers and are difficult to measure with conventional residual-stress experimental methods. Real-time holographic interferometry appears to be a viable technique to identify and monitor these stresses in plastic parts. In this investigation, holographic interferometry was used to monitor the relaxation of residual stresses in the plastic-molded actuator arm of a computer hard drive. In the first phase of this study, the relaxation of these residual stresses as a function of temperature was observed. In the second phase, the time to completely relax the residual stresses in the plastic part at an elevated temperature, the annealing temperature, was determined. In the third phase of this investigation, the rate of relaxation of these residual stresses as a function of time at various operating temperatures, was studied. Based on the results of this study, holographic interferometry appears to be a powerful research tool in the study of residual stresses in plastic parts. It also has the potential to be a practical tool for the inspection of manufactured plastic parts for the presence of residual stress.