Plastics, filler content tests

Figure 4 shows the different responses to abrasion at the end of the tests for filler contents of 0, 1 and 4 percent All plastic fillers except vent dust reduced abrasion. Vent dust caused an increase in the abrasion when only 1 percent was incorporated in the concrete, but it reduced the abrasion when the content was increased to 4 percent. 

Mineral microfillers have been tested in a plasticized starch matrix [CAR 01]. For example, micrometric particles of kaolin have been incorporated by extrusion. Due to a significant compatibility between the matrix and the filler, we note an increase in the glass transition temperature, a reduction in water absorption and an increase in the rigidity of the material. However, with the corresponding filler contents, these composites no longer satisfy the standards of biodegradation (at least 90% of the material has to be degraded). 

Although the primary purpose of this chapter is to discuss mechanical testing and strength of adhesive joints, the reader should be aware that ASTM covers a wide variety of tests to measure other properties. ASTM, for example, includes standard tests to measure the viscosity of uncured adhesives, density of liquid adhesive components, nonvolatile content of adhesives, filler content, extent of water absorption, stress cracking of plastics by liquid adhesives, odor, heat stability of hot-melt adhesives, ash content, and similar properties or features of adhesives. 

Standard test method for environmental stress-cracking of ethylene plastics Insulating and sheathing materials of electric and optical cables - Common test methods - Part 4-1 Methods specific to polyethylene and polypropylene compounds - Resistance to enviromnental stress cracking - Measurement of the melt flow index - Carbon black and/or mineral filler content measurement in polyethy-lene by direct combustion - Measurement of carbon black content by thermogravimetric analysis (TGA) - Assessment of carbon black dispersion in polyethylene using a microscope... 

Except for the CMUs which were produced in an industrial block plant, the batches were completed following the same procedure. Before starting a typical concrete batch, the water, sand and pea gravel were adjusted for moisture content. The two aggregates and the plastic filler were introduced into the mixer and mixed for approximately 30 seconds. The cement and two-thirds of the total water were added and the drum was rotated for 2 minutes more. The rest of the water was added within the next 30 seconds. After two minutes the drum was stopped, and the slump test was performed. The drum was then scraped to loosen any material not previously mixed. It was restarted and rotated... 

The fact that plastics are good insulators does not mean that plastics are inert in an electrical field. They can in fact, be made to conduct electricity by the addition of fillers such as carbon black and metallic flake. The type and degree of interaction depends on the polarity of the basic resin material and the ability of an electrical field to produce ions that will cause current flows. In most applications for plastics, the intrinsic properties of the polymer are related to the performance under specific test conditions. The properties of interest are the dielectric strength, the dielectric constant at a range of frequencies, the dielectric loss factor at a range of frequencies, the volume resistivity, the surface resistivity, and the arc resistance. The last three are sensitive to moisture content in many materials. These properties are determined by the use of standardized tests described by ASTM (Table 16-1). These properties of the plastics are temperature dependent as are many of their other properties. Temperature dependence must be recognized to avoid problems in electrical products made of plastics. 

Nontoxic Citrates Nontoxic citrate plasticizers derived from natural citric acid, such as triethyl citrate (TC), tributyl citrate (TBC), acetyl triethyl citrate (ATC), acetyl tributyl citrate (ATBC), and triacetine, have been shown to be effective plasticizers for PLA [27-29]. Some gas permeability tests have been performed to assess the potential use of PLA and nontoxic citrate plasticizer blends in food packaging and other applications. The effect of ATBC on PLA barrier properties was studied by Coltelli et al. [30] using PLA mixed with ATBC (10-35 wt%), followed by compression molding. Yu et al. [31] blended PLA/ATBC mixmres with carbon black (CB) to form electrically conductive polymer composites. Fourier transform infrared (FTIR) experiments revealed that the interaction between the PLA/ATBC matrix and the CB filler was increased by the addition of ATBC. Water vapor permeability values decreased with an increase in ATBC content (at constant CB levels). For example, at 30wt% CB, the WVP of the PLA decreased from 0.66 x 10 kgm/(msPa) (at 0% ATBC) to 0.10 X 10 kgm/(msPa) with the addition of 30% ATBC. 

The development of such a craze-like deformation band is shown in Fig. 6.3 in SEM in a sequence from an in situ deformation test of HDPE filled with 28 wt.% of about 1 pm AI2O3 particles [9]. The starting step is phase separation and void formation at the larger filler particles and agglomerates (a). Thin matrix strands between closely connected voids are plastically stretched and transformed into long fibrils (b). With increasing strain, craze-like deformation bands appear in the sample (c). Under an optimum balance of size and volume content of particles, as well as of matrix ductility, a remarkable Increase In toughness of such composites can be realized [9,10]. 

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