Instron measurements

The author thanks A. J. Thomas for Instron measurements Dr. A. R. Thompson for scanning electron microscopy and Dr. S. C. Peterson for proofreading the manuscript. 

An important consequence of entanglement and network formation is the effect on the Tg that determines all diffusion-limited structural and mechanical relaxation processes of the system. As shown schematically in Figure 10 (2), while the molecular or segmental Tg remains constant above the entanglement MW limit, the network Tg, i.e. the macroscopic, controlling Tg of the supramolecular network (that would affect Instron measurements of the modulus, for instance (D). continues to increase with increasing MW above the entanglement MW, because of the increased probability of crosslinks (97.101). 

PMMA sample no. Internal energy, J/g (Instron measurement)... 

Tensile Testing. The most widely used instmment for measuring the viscoelastic properties of soHds is the tensile tester or stress—strain instmment, which extends a sample at constant rate and records the stress. Creep and stress—relaxation can also be measured. Numerous commercial instmments of various sizes and capacities are available. They vary greatiy in terms of automation, from manually operated to completely computer controlled. Some have temperature chambers, which allow measurements over a range of temperatures. Manufacturers include Instron, MTS, Tinius Olsen, Apphed Test Systems, Thwing-Albert, Shimadzu, GRC Instmments, SATEC Systems, Inc., and Monsanto. 

Tensile and flexural properties were studied with an Instron 4204 testing machine. Tensile tests were performed on the drawn strands at a test speed of 3 mm/ min, while three-point-bending tests (ISO 178) at a speed of 5 mm/min were applied to the injection molded specimens. Charpy impact strength was measured of the unnotched samples with a Zwick 5102 pendulum-type testing machine using a span of 70 mm. The specimens (4 X 10 X 112 mm) used for three-point-bending tests were also used for the impact tests. It should be noted that neither the tensile tests for the strands nor the impact tests were standard tests. The samples were conditioned for 88 h at 23°C (50% r.h,) before testing. 

The labor-intensive nature of polymer tensile and flexure tests makes them logical candidates for automation. We have developed a fully automated instrument for performing these tests on rigid materials. The instrument is comprised of an Instron universal tester, a Zymark laboratory robot, a Digital Equipment Corporation minicomputer, and custom-made accessories to manipulate the specimens and measure their dimensions automatically. Our system allows us to determine the tensile or flexural properties of over one hundred specimens without human intervention, and it has significantly improved the productivity of our laboratory. This paper describes the structure and performance of our system, and it compares the relative costs of manual versus automated testing. 

Figure 1. Overall instrument layout showing (A) Instron 1125 universal tester (B) Zymark laboratory robots (C) Specimen bar magazine (D) Specimen bar measuring device.

Young moduli and breaking strength (measured by an Instron apparatus) of pectin gel and of extruded citrus fibre at different concentrations ( 60% sucrose, pH 3)... 

Texture measurements Texture of canned carrots was measured using Instron Universal Testing Machine (Model 1011) fitted with Kramer shear cell. Thirty grams of drained carrot cubes were evenly placed in the Kramer shear cell and were compressed, sheared and extruded using a crosshead speed of 100 mm/min. Each measurement was repeated 10 times and the mean was used to express the firmness of carrot cubes in Newton(N). 

Mechanical Properties. The mechanical properties of thin, solvent-cast polymer films were measured on an Instron Tensile Tester according to ASTM standard D882-83. In all cases, tensile values were calculated from the average of at least four measurements obtained from four separate specimens per polymer sample. 

All tensile and stress-relaxation measurements were done using an Instron Tensile tester. The samples were cut into the dumbbell shape corresponding to the ASTM D412 type C model (total length 4.5 in. straight part 1.5 in. width 0.25 in.). 

Mechanical Properties. The stress-strain and the hysteresis behavior of the polymers were measured on a Model 1122 Instron using dog-bone samples of 0.28 cm width and 1.0 cm effective length. The strain was measured using the displacement of the crosshead. In the calculation of the strain it was assumed that... 

Stress-Strain Data. Tensile tests were made with an Instron tester at some seven crosshead speeds from 0.02 to 20 inches per minute at five or six temperatures from 30° to —46°C. The tests were made on rings cut with a special rotary cutter from the circular sheets of the elastomers. The dimensions of each ring were determined from the weights of the ring and the disc from its center, the thickness of the ring, accurately measured, and the density of the rubber. Typically, the outside and inside diameters were 1.45 and 1.25 inches, respectively, and the thickness was about 0.085 inch. The test procedure used is described elsewhere (11), and the cubic equation, eq 4 in ref. j 2, was used to compute the average strain in a ring from the crosshead displacement. 

Characterization of Hydrogel Films. Mechanical testing was conducted in buffered saline on an Instron instrument, according to the modified ASTM D-1708 (tensile) and D-1938 (tear) and were reported in g/mm2 for modulus and g/mm for tear strength. The water contents and the amount of extractables were measured gravimetr ica1ly. 

Oligomer and Film Characterization. Brookfield viscosity measurements were taken on a Model RVTD digital readout viscometer. Samples for Instron testing were prepared on glass plates using 25 or 75 pm (1.0 or 3.0 mil) Byrd film applicator. Coatings for cure speed and MEK double rub (MEKDR) studies were prepared on aluminum Q-Panels using a 40 wire wound rod (100 pm or 4.0 mil). 

Dielectric constant and dissipation factor measurements were conducted according to the procedures of ASTM D-150-87. Tensile strength and modulus and percent elongation were measured on an Instron model 1125 according to the procedures of ASTM-D-882-83. 

Melt viscosities were measured using an Instron capillary melt rheometer (Model 3210) using a 0.050-in. diameter capillary (L D = 40 1). Corrected viscosities were calculated in the conventional manner. In all cases, samples were preheated for 7 min prior to data acquisition. 

The tensile strength, modulus, and elongation at break were measured on an Instron Tensile Tester at a crosshead speed of 20 in./min (ASTM D-412) and the hardness by means of a Shore A Durometer (ASTM D-2240). 

Tensile Tests. Polymers were padded on filter paper at lOX add-on, cured at 150°C for 3 or 10 min, and tested as In Tappi Useful Method UH656. Tensile measurements on padded samples were done with 1" strips on an Instron Tester after conditioning In a constant temperature and humidity room. Wet, methyl ethyl ketone (MEK) and perchloroethylene (PCE) tenslles were run after brushing the sample with IX aqueous Aerosol OT or solvent. 

Foamed blends of ethylene-styrene interpolymer and LDPE were subjected to a range of mechanical tests, including compressive impact testing, Instron compression and Poisson s ratio measurements, compressive creep measurements and compression set and recovery measurements. The data obtained were compared with those for EVA and the suitability of these foamed blends as replacements for EVA in the manufacture of soccer shin guards and midsoles for sports shoes was evaluated. 20 refs. 

Texture has a number of component attributes, and some of them can be assessed by mechanical means. The texture or firmness of cooked potatoes is evaluated by subjecting each sample to a compression test using a universal testing machine equipped with a load cell. Cooked potato cylinders are compressed in a single-cycle compression-decompression test. Uniaxial compression is measured with an Instron machine with a lOON load cell. Measurements are performed on hot potato cylinders (depth 12 mm, height 10 mm) from 15 potatoes immediately after cooking, at a deformation rate of 20 mm/min. Stress and strain at fracture are calculated by the Instron series IX version 7.40 software and means of 15 repetitions are calculated. 

The texture of the processed potato can also be measured by shearing using a single blade, 1 mm thick, attached to the crosshead of the Instron Testing Machine. The processed whole potato with its skin intact is placed on the steel platform of the Instron and sheared longitudinally to a depth of 25 mm at a cross-head speed of 50 mm/min. Maximum shear force (kN) is calculated from the plot of force against displacement. 

Stress-strain measurements were carried out on molded films ( 1 mm thickness) at room temperature by the use of microdumbell-shaped samples and an Instron tensile tester (model No. 1130, crosshead speed of 5 cm/min). The samples were premolded between Mylar sheets for 10 min at 162 °C at about 5000 psi, then remolded at 165 °C and 7000 psi for 20 min, and slowly cooled ( 1 °C/min) to 50 °C. Select samples were solvent extracted by MEK using a Soxhlet extractor before molding. 

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