Tensile properties, experimental determination

The main experimental methodology used is to directly characterize the tensile properties of CNTs/polymer composites by conventional pull tests (e.g. with Instron tensile testers). Similarly, dynamic mechanical analysis (DMA) and thermal mechanical analysis (TMA) were also applied to investigate the tensile strength and tensile modulus. With these tensile tests, the ultimate tensile strength, tensile modulus and elongation to break of composites can be determined from the tensile strain-stress curve. 

The experimental results that will be examined consist of studies that look at the ability of a random copolymer to improve the properties of mixtures of the two homopolymers relative to the ability of a block copolymer. The three different systems that are examined include copolymers of poly(styrene-co-methyl methacrylate) (S/MMA), poly(styrene-co-2-vinyl pyridine) (S/2VP), and poly(styrene-co-ethylene) (S/E) in mixtures of the two homopolymers. The experiments that have been utilized to examine the ability of the copolymer to strengthen a polymer blend include the examination of the tensile properties of the compatibilized blend and the determination of the interfacial strength between the two homopolymers using asymmetric double cantilever beam (ADCB) experiments. 

Young s modulus of elasticity quantifies the elasticity of the polymer. Like tensile strength, this is highly relevant in polymer applications involving physical properties of polymers. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke s law holds. This can be experimentally determined from the slope of a stress-strain curve created during tensile tests conducted on a sample of the material. 

Although oven temperatures between 282-357°C have been sueeessfully tried for rotomolding ECTFE, the recommended range is 288-315°C.1 1 At temperatures above 321°C, small bubbles are formed that are difficult to eliminate from the part. Cycle time has to be determined experimentally. The best approaeh is to begin with a short eyele and inerease it until the optimal cyele has been determined. Speeific gravity and tensile property measurements ean eontrol the quality of the part. Table 9.10 gives examples of cycles for a few different part designs. 

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