摘要:

AbstractThe principal possibilities of acceleration will be discussed. Technical polymers are a complicated system of several components exposed to the various influencing factors of the weather which themselves are often in interaction. A decisive technical presupposition concerning the comparison of accelerated weathering and outdoor weathering as well as reproducibility of accelerated weathering results are adjustment, measurement and control of the most important influencing parameters in the weathering device. This will particularly be discussed for the following parameters: Spectral energy distribution, irradiance/radiant exposure, relative humidity/water, and concentration of various industrial pollutant gases.

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370101

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractIn recent years increasing importance has been attached to modified, extended and new kinds of test tasks, such as‐ the action of radiation at a simultaneous extreme thermal stress;‐ synergistic influence of the climate (primarily radiation) and e. g. mechanical stress;‐ testing of structural parts and systems (with the requirement of large irradiation surfaces).This aspect as well as primarily ergonomic reasons in the field of the conventional accelerated light exposure and weathering tests in machines have stimulated the discussion about alternative light sources beside the time‐tested Xenon radiation appropriate for the simulation of solar radiation, they have initiated quite a number of scientific investigations, and have now found their first realization in the correspondig machines and equipment.New findings in the application of special metal halide lamps and fluorescent tubes as alternative light sources for Xenon radiation are being discussed on the basis of some typical results.The importance of the infrared part in the artificial radiation to simulate particular phenomena of deterioration is shown with the help of an example of specific problems in the automobile industry, and the transfer of these findings into especially developed and problem‐oriented machine and equipment technology will be

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370102

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe effectiveness of radiation as a function of angle of incidence on polymer films has been calculated and examined by exposure tests. Theoretical considerations for different coefficients of transmission and different indices of refraction show that the radiation with normal incidence is the most effective. However, it is concluded that a photoreceptor which is cosine corrected for a solid angle of 2π sr does undervalue radiation with oblique incidence. The exposure tests confirm these theoretical results but also show an additional unexplained peak of effectiveness for radiation with angles of incidence of about 20

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370103

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe stabilizing action of calcium‐zinc stearate and pentaerythritol systems in PVC cannot only be ascribed to the ability of binding hydrogen chloride, but also to the replacement of labile chlorine atoms of the PVC chain by stearate groups. In this way the growth of the polyene sequences is inhibited. On the other hand sufficient amounts of pentaerythritol and calcium stearate effectively inhibit the detrimental catalytic action of zinc chloride formed.A mathematical equation was deduced based on this mechanism, which satisfactorily describes the correlations among the induction period, the stabilizer concentration and the ester groups formed during thermal agein

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370104

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractWe have investigated variations in mechanical properties such as tensile strength and specific elongation as well as the variations in electrical properties such as the dielectric loss angle, permitivity and surface resistivity of PVC sheets of various thicknesses exposed during 24 months in weathering and up to 400 h in a Xenotest‐1200. Using the test data, an evaluation of the influence of the scale coefficient during ageing was achieved. The test data showed that lower variations in the investigated properties were seen in the case of the thicker sheets.After various ageing periods a correlation between the surface roughness, mechanical and electrical properties could be seen. More important variations could be seen during the ageing period ranging from 50 h to 6 months.Speculations were made about the reasons causing the variations observed in the properties of PVC sheets during agein

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370105

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractA problem of protecting polymers against weather influences is to concentrate the protective agents (UV‐absorbers, antioxidants etc.) in the adequate place: the surface layer where photocxidative reactions primarily set in. The outstanding properties of polycarbonate (PC) are high levels of toughness and heat resistance whereas polymethylmethacrylate (PMMA) exhibits brilliant transparency and excellent weatherability. Mainly because of its higher spectral energy absorption from global radiation in the critical range from 300 to 400 nm wavelength PC is inferior to PMMA in weatherability: yellowing and erosion within a 20 μm surface layer of PC become visible after 5 years natural weathering. So the idea suggested itself to combine the favourable properties of these two polymers by coating PC with acrylics. As far as weathering results are available today this idea turned out to be very useful: the improvement in weatherability by coating PC regarding the yellowness index, light transmittance and surface erosion is a factor 2–3 in time and even

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370106

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe stabilization of polyamides or nylons, considered the oldest engineering plastics, has been the subject of many patents in the last 50 years. Most of these patents refer to attempts to improve the resistance of polyamides against the negative influence of heat and oxygen. Light stability, however, was always of certain interest as well, and more so in recent years when polyamide producers started to search seriously for new fields of application.Some general remarks will be made on how to test the heat stability of this substrate group. The three different types of heat stabilizing systems with their advantages and disadvantages will be discussed briefly. Among these three systems ‐ copper halides, secondary aromatic amines and phenolic antioxidants ‐ the latter will be dealt with in some depth.Some information will cover investigations on stabilization of polyamides in general. Another study will be presented that deals with the behavior of polyamide 6 at various elevated temperatures. The results of an extraction of polyamide 66 with boiling water will be explained including discussion of the consequences.An example will also be given for the heat stabilization of polyamide 12.Some general remarks on testing polyamides under the influence of light lead to several considerations concerning light stabilizer systems for polyamides. Examples will be given for polyamides 6, 66 and 12.A short survey of the status quo with regard to polyamide stabilization and an outlook for the future will conclude this pa

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370107

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractThe cold‐drawing behavior of naturally aged poly(ethylene terephthalate) (PET) is investigated and an attempt is made to compare the mechanical behavior of unaged commercial PET and material which has been naturally aged for 11 years. Mechanical, viscometric, DSC and IR measurements are applied. The previously observed unusual ability of fresh PET bristles to be cold drawn up to 15:1 is not achieved for the naturally aged material. This fact is related to chemical cross‐linking occuring on the surface of bristles after drawing and thermal treatment. The cross‐linking skin is unsoluble, infusible and uncrystallizable. The naturally aging defeats the ability of PET to respond to external treatments which would otherwise change the internal structure. Such a “stabilization” of material properties is a result of the transformation, during natural aging, of the original physical network into a chemical network consisting of coval

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370108

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractOxidative degradation of segmented copoly(ether ester)s can be suppressed by interference of the following basic processes:a. degradative radical chain reactions. Effective inhibition is possible by means of primary antioxidants.b. initiation of the radical chain reactions by means of hydroperoxides formed. Such initiation reactions can be suppressed by inactivation of the hydroperoxides with the aid of secondary antioxidants.c. polyester segmental chain scission by formic acid formed during oxidative degradation of the polyether segments. By scavenging the formic acid, or its precursor formaldehyde, this serious process can be restricted.Combined addition of stabilizers, simultaneously influencing the basic processes a., b. and c. can lead to synergism. Examples of the activity of the different stabilizers are given.

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370109

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY

摘要:

AbstractIrradiation of dilute solution of cis‐1,4‐polybutadiene in carbon tetrachloride with UV light in the presence of air causes fast formation of white precipitate—insoluble gel. It has been shown that carbon tetrachloride was effective photosensitizer for oxidation of cis‐1,4‐polybutadiene. Separated sol and gel fractions were analysed by infrared spectroscopy for better understanding of gelation process and structure of the gel. Three stages were detected in the process of oxidative photogelation of cis‐1,4‐polybutadiene in carbon tetrachloride solution: pre‐gelation(sol‐stage), gelation (sol/gel‐stage) and post‐gelation (gel‐stage). In the first stage intensive photooxidative reactions between cis‐1,4‐polybutadiene, carbon tetrachloride and oxygen take place, giving products with high content of hydroperoxide and bounded chlorine. When hydroperoxide and chlorine content reached critical value, precipitation‐gelation takes place. It is proposed sequence of free radical reactions which involves: photolysis of carbon tetrachloride to free radicals, addition of solvent radicals to the double bonds of rubber followed by combining of resulting radicals with oxigen to chlorinated polymeric peroxy radicals. Initially formed gel is peroxidic in nature, which photolyses to the more stabile ether

ISSN:0003-3146    

DOI:10.1002/apmc.1985.051370110

出版商:Hüthig&Wepf Verlag    

年代:1985

数据来源: WILEY