Hardness type Shore

Figure 15.8 shows the evolution of the parameter of surface hardness type Shore A, depending on the concentration of nanoparticles for vulcanized NR and magnetic nanocomposites (NR/NZF). Dots represent the experimental data and the line represents the theoretical fit. Measurements were made using a typical laboratorial durometer in Shore A scale. The assay was performed in quintuplicate and measurement time equal to Is, in accordance with the international standard ISO 868 2003. The hardness type Shore A was determined from Equation (15.1) ... 

Figure 15.8 Hardness type Shore A for the magnetic nanocomposites based on vulcanized natural rubber (NR/NZF) depending on the nanoparticle concentration.

Type C2H4 mole% Tg/T , Crystallinity % Tensile strength kg cm " Izod impact strength kg cm cm " 23 °C Elongation at break % Flexural modulus kg cm Hardness, Brittle shore A temperature T... 

A very convenient and simple way to compare the mechanical strength of two materials is to compare their hardness. The testing device used to measure the hardness is a Zwick type 3117 apparatus. The hardness is measured by pushing a needle into the material with a certain force (fixed value). The depth of the indentation is related to the hardness (hardness scale Shore D). Materials with a hardness between 70-80 Shore D are considered to he very hard. 

Various types of hardness meters are available from ATS FAAR inclnding International Rubber Hardness Degree, Shore, Rockwell, and Fiat for testing against ASTM, ISO, UNI, DIN and FIAT specifications. The Martin Instrument Company is also a supplier of Shore hardness meters. Hardness measurements have recently been reported on methacrylate dental resins [31], polymeric coatings based on polyester resin, PU and acrylic acid [32], polyacrylamide [33] and aged PE [34]. 

Tear resistance was measured at 22°C using a trouser tear specimen described in ASTM D 470-82. The crosshead speed was 500 mm/min. The data reported are averages of results for six specimens. A hand-held Shore Durometer, hardness type "A-2" was used to determine the hardness of the samples, according to ASTM D 2240-75. Specimens were rectangular, 25 mm in length by 13 mm wide. Four plies of sample were used to achieve a thickness of 6.4 mm. Three readings were taken, 6 mm apart on the surface of the four plies. Hardness values measured on the blocks tended to be as much as five units lower. 

Shore hardness It is the indentation hardness of a material as determined by the depth of an indentation made with an indenter of the Shore type durometer. The scale reading on this durometer is from zero (corresponding to 0.100 in. depth) to 100 for zero depth. The Shore A indenter has a sharp point, is spring-loaded, and is used for the softer plastics. The Shore B indenter has a blunt point, is spring-loaded at a higher value, and is used for harder plastics. 

An instrument for the determination of the hardness of vulcanised rubber. The name is usually, but not necessarily, applied to a pocket-type instrument made by the Shore Instrument and Manufacturing Co. Inc. The use of the term in the sense of hardness (a durometer of 60°) is not recommended. 

ISO 7267-2 1986 Rubber-covered rollers - Determination of apparent hardness - Part 2 Shore-type durometer method... 

For many years there was no move to produce an international standard for durometers but one was eventually published in 1986. ISO 7619 is now in two parts44,45, separating a meter calibrated in IRHD from the others. Part 1 now covers the Shore A and D type meters, a meter designated AO for soft materials and a micro Shore type meter designated AM. The Shore A scale corresponds approximately to the IRHD scale and the D scale can conveniently be used for hard rubbers above about 90 Shore A. The AO meter is suitable for rubbers less than 20 Shore A, whilst the AM meter covers the normal Shore A range. As expected from its name, the meter in Part 2 of the standard covers the IRHD range. 

Owing to the specific type of action, the method has no use in mineral testing (small surfaces), but being a non-destructive method it is recommended for estimation of rocks used for lining. Specified in Table 4.4.6 are Shore hardness values selected from among 179 measurements of various rocks in the Soviet Union, published by Baron (1973). As evidence... 

Substitute for Conventional Vulcanized Rubbers, For this application, the products are processed by techniques and equipment developed for conventional thermoplastics, ie, injection molding, extrusion, etc. The S—B—S and S—EB—S polymers are preferred (small amounts of S—EP—S are also used). To obtain a satisfactory balance of properties, they must be compounded with oils, fillers, or other polymers compounding reduces costs. Compounding ingredients and their effects on properties are given in Table 8. Oils with high aromatic content should be avoided because they plasticize the polystyrene domains. Polystyrene is often used as an ingredient in S—B—S-based compounds it makes the products harder and improves their processibility. In S—EB—S-based compounds, crystalline polyolefins such as polypropylene and polyethylene are preferred. Some work has been reported on blends of liquid polysiloxanes with S—EB—S block copolymers. The products are primarily intended for medical and pharmaceutical-type applications and hardnesses as low as 5 on the Shore A scale have been reported (53). 

There are several ways of measuring indentation, but they differ only in the type of equipment used. Basically, they all measure the size of indentation produced by a hardened steel or diamond tool under a defined pressure. A durometer is an instrument for measuring hardness by pressing a needlelike instrument into the specimen. Durometers are available in several scales for measuring relatively hard, brittle materials to soft elastomers. The two types appropriate for most cured adhesives and sealants are the Shore Type A and Shore Type D. ASTM C 661 offers a method for measuring indentation hardness of elastomeric-type sealants. 

Materials. Two types of standard tire cord obtained from Gen Corporation were used in this investigation polyester, 1300/3, and nylon 66, 1260/3. The rubber composition to which the adhesively dipped cords were bonded had the following composition in parts by weight styrene-butadiene rubber (SBR) 1502, 100 N330 carbon black, 50 zinc oxide, 5 stearic acid, 0.5 sulfur, 1.7 2-morpholinothio-benzothiazole, 2. Master batches were mixed 7 min in a 350-ml Brabender Plasticorder, and curatives were added on a cool two-roll mill. Cure characteristics at 155 °C were determined with an oscillating disc rheometer (ASTM D 2084). The time to reach 90% of the final cure state was 23 min, and the Shore A hardness of the final vulcanizate was approximately 60. 

Shore A hardness was measured by a type A2 Iidentation Durometer. 

Another type of hardness measurement is that involving the dynamic deformation or indentation of the material specimen. In the most direct method an indenter is dropped on to the metal surface and the hardness is expressed in terms of the energy of impact and the size of the resultant indentation (Martel, 1895). In the Shore rebound scleroscope (Shore, 1918) the hardness is expressed in terms of... 

EPDM (monomer name), 75 Shore A (as-cured hardness). However, this type of identification scheme is insufficient to guarantee reliable service performance in critical applications. See Figure 7-3. 

Unsaturated resins are usually mixtures of vinyl monomers and prepolymers, such as unsaturated polyesters, polyurethane acrylates, and ac-rylated epoxides of the bisphenol A type. Polymerization of styrene-based resins involves the formation of a three-dimensional network via the cross-linking of prepolymer chains by styrene radicals. These standard thermoset resins are therefore characterized by great hardness (Shore D over 80, DIN 53505, arbitrary scale 0-100 based on the penetration of a needle point in the tested material), do not melt, and are not soluble in organic solvents. 

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