Crystallinity test specimens

These workers stress that high temperatures encountered for limited periods in practice, (e.g. during pasteurisation, sterilisation or preparation of foodstuffs in plastics packs) must be simulated by use of appropriate test temperatures and times. Moreoever, experimental films made only for test purposes should be of the same thicknesses as the article that will actually be used, since the thickness of the film has a definite influence on the amount of additive migrating. The extent of migration also depends on the physico-chemical properties of the test material, including its density, surface quality and crystallinity. Test specimens, both of films and plastics containers should therefore be made under standard production conditions. 

Microindentation hardness normally is measured by static penetration of the specimen with a standard indenter at a known force. After loading with a sharp indenter a residual surface impression is left on the flat test specimen. An adequate measure of the material hardness may be computed by dividing the peak contact load, P, by the projected area of impression1. The hardness, so defined, may be considered as an indicator of the irreversible deformation processes which characterize the material. The strain boundaries for plastic deformation, below the indenter are sensibly dependent, as we shall show below, on microstructural factors (crystal size and perfection, degree of crystallinity, etc). Indentation during a hardness test deforms only a small volumen element of the specimen (V 1011 nm3) (non destructive test). The rest acts as a constraint. Thus the contact stress between the indenter and the specimen is much greater than the compressive yield stress of the specimen (a factor of 3 higher). 

Mechanical Properties. Because PVDC is difficult to fabricate into suitable test specimens, very few direct measurements of its mechanical properties have been made. Some characteristic properties of high VDC content, unplaslicized copolymers are listed in Table 3. The performance of a given specimen is sensitive to morphology, including the amount and kind of crystallinity, as well as orientation. Tensile strength increases willi crystallinity, whereas toughness and elongation decrease. Orientation, however, improves all three properties. 

For simulating the heterogeneous crystallization process, a test specimen witii a dimension of 3a 3a l2a including two amorphous-crystalline interfaces is prepared by attaching 12 layers of c-Si (216 atoms), as a crystalline seed, to a bulk fl-Si (648 atoms). The bulk a-Si is obtained by the above cooling process and pre-annealed at 500 K for 200 ps. The constant NVT MD simulations are carried out using the Newton equation with a time step for the integration set at 2fs. 

The EWF tests were named with a eode indicating material, erosshead rate and orientation, in that order. In this way, PC20-10T (or P) results correspond to tests carried out on PC20 blends tested at 10 mm/min in 90° (or 0°) crack propagation with respect to the melt flow direction. It is important to mention that even the fact that tensile parameters were determined on thicker (4 mm) dumbbell specimens could invalidate their use in EWF validations due to some morphological and crystallinity differences, some SEM observations and DSC measurements on plaques and dumbbell test specimens verified that these microstructural features are quite similar on both specimen geometries (Table 1). 

PHB Under optimum conditions, in the accumulation phase during the fermentation process, the rate of the enzymatic degradation of this amorphous PHB is extremely fast, within a few hours. In contrast to this, extracted or processed, partially crystalline PHB is attacked relatively slowly over periods of weeks. The enzymatic decomposition, for example, of the PHB test specimen, leads to a slow surface erosion, while the volume body remains unchanged for some time, so the whole weight and the properties change slowly. The enzymatic degradation occurs at the surface of the PHB material and the rate of the surface erosion is strongly dependent on both the structure and the composition. 

All test specimens were injection molded under controlled conditions, and a 6000 ci cobalt-60 facility was used for sample irradiation. The isotactic polypropylene was 60% crystalline with a density of 0.903 g/cm3. 

Oxidised single crystalline NiAl specimens were deformed by four-point bending at elevated temperatures. Bend tests at RT could be performed only with Fe-doped NiAl because of its higher ductility. Typical scale defects which were generated on the side... 

It is one of several methods used to measure the softening temperature or temperature resistance of a plastic. It should be noted that the heat distortion point is generally lower than the glass transition temperature or melt temperature of the polymer because of the mechanical effect of the load. However, in amorphous polymers, HDT is generally the same as the glass transition temperature (Tg) of the material. The HDT test method is more reproducible with amorphous polymers than with crystalline polymers. With some polymers, it may be necessary to anneal the test specimens to obtain reliable results. 

Polymer pellets of isotactic polypropylene (iPP) were melted in a laboratory hot press for 15 min at 230 °C and 10 MPa, and then quenched in ice water (0 °C) or boiling water (100 °C). To control the crystallinity of the iPP sample, we annealed the sample sheets prepared at 0 °C for 2 hr at various temperatures from 40 to 140 °C. Square pillar shaped test specimens were cut out from a 1 mm thick sheet and used for the measurements. Double-edge notched sample specimens with the gauge length of 2 mm were used for the temperature dependence and the dumbbell shaped specimen with gauge length of 5 mm for the elongation speed dependence. 

Fired clay is formed by a matrix of glass beads in a glass phase. Therefore, it can manifest crystallinity through vitreous grains such as character through the matrix. However, the conductivity and specific heat of the tested specimens show the baked clay has a crystalline character [23]. With respect to conductivity, it decreases linearly with temperature from 0.87 W/(mK) to about the value of 0.4 W/(mK). 

The HDPE of fuel tanks contains small amounts of fluorine, determined as 0.3-1 g per 10 kg tank, incorporated as a sealant and present as polytetraethylene (PTFE). In Stage 2, to determine the effect of this fluorine, samples of fluorinated and unfluorinated tanks were sawn into small pieces and reground before being formed into injection-moulded test specimens for determination of torsion modulus, and of tensile, impact and ballistic properties. The thermal properties investigated were the degree of crystallinity, melting temperature, and flow characteristics. The measured properties were compared with those provided for in the relevant quality order for new material. 

Microscopy (qv) plays a key role in examining trace evidence owing to the small size of the evidence and a desire to use nondestmctive testing (qv) techniques whenever possible. Polarizing light microscopy (43,44) is a method of choice for crystalline materials. Microscopy and microchemical analysis techniques (45,46) work well on small samples, are relatively nondestmctive, and are fast. Evidence such as sod, minerals, synthetic fibers, explosive debris, foodstuff, cosmetics (qv), and the like, lend themselves to this technique as do comparison microscopy, refractive index, and density comparisons with known specimens. Other microscopic procedures involving infrared, visible, and ultraviolet spectroscopy (qv) also are used to examine many types of trace evidence. 

In colorfastness to acid spotting, ISO 10S-E0S, drops of a solution of either acetic acid (300 g of glacial acetic acid per Hter of water), sulfuric acid (50 g of concentrated acid per Hter), or tartaric acid (100 g of crystalline acid per Hter) are spotted onto the test material, which is then dried and assessed. Colorfastness to alkaH spotting, ISO 10S-E06, is like E05 except that a solution of 100 g of anhydrous sodium carbonate per Hter of water is used. Colorfastness to water spotting, ISO 10S-E07, is like E05 but uses drops of water and assessment is made after 2 min wet and after drying. In colorfastness to hot water, ISO 10S-E08, the textile specimen and adjacents are wound around a glass rod and placed in water adjusted to pH 6 with acetic acid at 70°C... 

The fracture strength and mode of fracture of a material have been found to be related to a number of characteristics of the polymer molecules of which it is made up. These include, among others, constitution, molar mass, polydispersity, crystallinity, and degree of crosslinking. Other factors which also affect fracture strength and mode of fracture are temperature, strain rate, and geometry of the specimen, all of which are decided upon prior to testing the material. 

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