Test for polymeric materials

A number of fire tests for polymeric materials have been developed, during the past several years, by the International Standards Organization (ISO). Hopefully, these tests will replace the present national test methods, which often correlate badly with each other. I he development at ISO is aimed at describing the fire properties of polymeric materials comprehensively, with test methods chosen so as to be applicable to all types of samples. At present, the ISO fire test methods are published as standards (ISO R 1182-79 for non-combustible materials, ISO R 1326-70 and ISO R 1210-70 for flame spread, etc.), or as draft for development (DP 5657, ISO/TC 92 N 531-79 as an ignitability test). One can only sympathize with using certain complex fire hazard indices for describing material behavior in fire... 

The standard fatigue tests for polymeric materials are the ASTM-D 671 test and the DIN 50100 test. In the ASTM test, a cantilever beam, shown in Figure 1, is held in a vise and bent at the other end by a yoke which is attached to a rotating variably eccentric shaft. 

The limiting oxygen index of Tefzel as measured by the candle test (ASTM D2863) is 30%. Tefzel is rated 94 V-0 by Underwriters Laboratories, Inc., in their burning test classification for polymeric materials. As a fuel, it has a comparatively low rating. Its heat of combustion is 13.7 MJ/kg (32,500 kcal/kg) compared to 14.9 MJ /kg (35,000 kcal/kg) for poly(vinyHdene fluoride) and 46.5 MJ /kg (110,000 kcal/kg) for polyethylene. 

The Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances (UL 94) has methods for determining whether a material will extinguish, or burn and propagate flame. The UL Standard for Polymeric Materials-ShortTerm Property Evaluations is a series of small-scale tests used as a basis for comparing the mechanical, electrical, thermal, and resistance-to-ignition characteristics of materials. 

From a pharmacological point of view the first two strategies raise several distinct disadvantages. First, the exact structures of these fullerene-based systems in solution are usually unknown and, especially for polymeric materials inhomogeneous samples are frequently obtained. Furthermore, in many cases the amount of incorporated fullerene is not clearly determined. In addition, the presence of other molecules like the hosts or polymeric residues can cause unpredictable side effects and in no case the mode of action or activity can doubtlessly be associated with the fullerenes. However, for systematic investigations on structure-function relationships or extensive testings of toxicological or human availability properties, the use of structurally well-defined and characterized materials is mandatory. 

It must be noted that the values cited in the tables of data and within the text for polymeric materials are typically average values with the actual measured value obtained for a material dependent on the specific origin of the material (i.e.. conditions of synthesis and pretreatment) and on the specific test procedure employed. 

The American Society for Testing and Materials (ASTM) provides standards, compatibility testing, and tests for mechanical properties, recommended practices and procedures as well as codes for polymeric materials. The various industry codes and standards are summarized in Table 4.95. 

The benzyl-spaced aminosilica was also used as a scaffold on which to anchor CGC-inspired catalysts [19]. As in the trityl-spaced study, the aminosilica was first reacted with Cp -silane. For the benzyl-spaced materials, complete conversion of the amine groups through reaction with the Cp -silane did not occur however, the amine conversion for this material was twice the amine conversion for the traditionally grafted material (63% reacted amines vs. 29% reacted amines) [19]. When the grafted, metallated catalyst was tested for polymerization of ethylene, the benzyl-spaced catalyst again outperformed the traditionally grafted material, although it was somewhat less active than the trityl-spaced immobilized catalyst. 

It is well established that the presence of fluoride on a Cr/silica-titania catalyst increases its 1-hexene incorporation efficiency, and lowers the amount of very low-MW material [605]. Table 43 shows one example of this. Two catalysts, Cr/silica and Cr/silica-titania, were activated at 600 °C, with and without fluoride. These catalysts were tested for polymerization activity in the presence of 0.5 mol L 11-hexene. In the absence of titania, no difference was observed in the amount of 1-hexene incorporated into the polymer. However, Cr/silica-titania exhibited a major increase in 1-hexene incorporation when it contained fluoride. 

List of Pertinent ASTM Testing Methods for Polymeric Materials... 

There are many other tests that can be carried out on adhesives using standard test methods for polymeric materials and these should be reviewed for the most appropriate procedure (see Standards on adhesion and adhesives. Appendix). 

There are several standards that medical polymers must adhere to. One of the most common standards observed for polymeric materials is published by the United States Pharmacopeia (USP), which necessitates using animal models (in vivo) to test toxicity of elastomers, plastics, and other polymeric materials, prior to clinical use. The standard and forms of testing it outlines is considered in the medical industry as the minimum requirement for a polymeric material before it is considered for use in healthcare applications. According to the standard the biological response of the test animals are measured and determined via three main techniques (1) Systemic toxicity test Evaluates the effects of leachables of intravenously or intraperitoneally injected materials on systems such as the nervous or immune system (2) Intracutaneous test Evaluates local response to materials injected under the skin (3) Implantation test Both local tissue microscopic and macroscopic parameters evaluated at material implant sites. 

Nanodispersed metal hydroxides have been proved as efficient flame retardants for polymeric materials. It has been shown [107] that the LOI obtained from EVA containing 50 wt% Mg(OH)2 increases from 24% to 38.3% when micrometric Mg(OH)2 (2-5 irm) is replaced with nanometric Mg(OH)2. The enhancement of EVA flame retardancy by nanosized Mg(OH)2 was attributed to the good dispersion of the nanoparticles, which leads to the formation of more compact and cohesive charred layers during the combustion test. Therefore, the nanodispersed LDH layers may also contribute to the flame retardancy of polymer/LDH nanocomposites. 

The UL Standard for Polymeric Materials—Short Term Property Evaluations is a series of small-scale tests used as a basis for comparing the mechanical, electrical, thermal, and resistance-to-ignition characteristics of materials. 

Through proper selection of the SFM cantilevers, a very wide range of polymeric materials can be tested by the SFM technique. Elastic moduli can be measured as low as MPa for rubbers to as high as several tens of GPa for hard plastics if selection of cantilever spring constants from 0.05 to 100 N/m is available. A probe plot selection for quick evaluation of optimal SFM cantilevers for polymeric materials with various elastic properties is proposed and verified. 

Dielectric breakdown is a measurement of breakdown voltage which is made parallel rather than perpendicular to the plane of a sample, as illustrated in Fig. 9.7(b). In the standard test (D149) the electrodes are taper pins inserted into the sample on 1 in centres. The voltage is applied at a controlled rate of increase with the sample immersed in oil. Dielectric strength depends on both surface and bulk characteristics of a material and is, of course, reduced by increases in humidity, water absorption and ionic or other conducting contaminants. Typical values for polymeric material are in the range 10-50 kV. 

Table 2.5 summarises the main applications of thermal analysis and combined techniques for polymeric materials. Of these, thermomechanical analysis (TMA) and dynamic mechanical analysis (DMA) provide only physical properties of a very specific nature and yield very little chemical information. DMA was used to study the interaction of fillers with rubber host systems [40]. Thermomechanical analysis (TMA) measures the dimensional changes of a sample as a function of temperature. Relevant applications are reported for on-line TMA-MS cfr. Chp. 2.1.5) uTMA offers opportunities cfr. Chp. 2.1.6.1). The primary TA techniques for certifying product quality are DSC and TG (Table 2.6). Specific tests for which these techniques are used in quality testing vary depending upon the type of material and industry. Applications of modulated temperature programme are (i) study of kinetics (ii) AC calorimetry (Hi) separation of sample responses (in conjunction with deconvolution algorithms) and (iv) microthermal analysis.

In the field of polymer/additive analysis a rather limited number of other laboratory performance studies is available. Recently, the Swiss Eederal Laboratories for Materials Testing and Research (EMPA, St. Gallen) has organised a series of interlaboratory tests on polymeric materials, examining the glass transition point by DSC (amorphous thermoplastics), antioxidant content in polyolefins. 

Perfluoropolymers bum, but do not continue to bum when the flame is removed. All perfluorinated fluoropolymers pass a UL 83 vertical flame test and are classified 94 V-0 according to Underwriters Laboratory (UL) in their burning test classification for polymeric materials. Limiting oxygen index (LOI) by ASTM D2863 is 95% or higher for PTFE, PFA, FEP, and PCTFE. Partially fluorinated fluoropolymers are more flame resistant than other thermoplastics but not quite as resistant as the perfluorinated fluoropolymers, as evidenced by their lower EOI values. PVDF, ETFE, and ECTFE meet UE 94 V-0. Table 13.48 lists the EOI of various fluoropolymers. 

ASTMF732-00(2011) Standard Test Method for Wear Testing of Polymeric Materials for Use in Total Joint Prostheses. 

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