Rockwell R hardness

Extremely soft and fluid blends of E-plastomers with iPP have been made by incorporating a large amount of a low-density E-plastomer with added process oil for fluidity and softness with a minor amount of iPP [10]. In a representative formulation, 56 parts of an impact copolymer (ICP) which had 62 wt% of iPP and the balance an EPR, 22 parts of an E-plastomer (hexene comonomer), 11 parts of an E-plastomer (octene comonomer), and 5 parts of talc showed a Rockwell R hardness 77,... 

Parts TCPb notch) Rockwell R, Hardness Flame Resistance... 

Procedure B of the Rockwell R hardness test (ASTM D785) applies to plastics. The load on a 0.5 in (1.3 cm) indenter is held for 10 s at 10 kg and then increased... 

Results of the hardness test regression are summarized in Table 4. The p-value and adjusted R squared indicate a highly significant regression that explains 63.5% of the variation present. Both factors and the interaction between them are statistically significant. As expected, an increase in mold temperature resulted in a drop in hardness, which is due to the thinner skin thickness. As expected, an increase in the lubricant content resulted in an increase in the hardness, which is due to the thicker skin. The interaction shows that at higher mold temperatures, the increased lubricant content resulted in a lower hardness than at lower lubricant levels. However, neither of the factors showed a substantial increase in hardness the largest factor effect was a decrease of approximately 2 points on the Rockwell R hardness scale. This is not unexpected since the skin is relatively thin (typically 500-600 microns) and a hardness test compresses the entire cross-section of the sample. 

Hardness Measurements. Hardness was measured on two scales, the Rockwell R scale, and the Shore D scale. The Rockwell test measures nonrecoverable deformation after a %-inch sphere has been pressed into a molded sheet of the plastic and the load released. In the Shore... 

With the second category of hardness tests the measurement is carried out after the load is removed. This is the case with Rockwell R, S, V. L, M and P under a small prestress the position of the sphere is measured, so the permanent penetration depth, h (mm). The sphere diameter isy or j inch, the load is 60, 100 or 150 kg force, dependent on which of the six types of test is chosen. The hardness is defined as HR = 130 - hi0.002. This hardness value has no relation at all to the modulus of elasticity the permanent deformation after recovery is being measured (such a type of test would result in a very high value for rubbers ). 

Hardness of PTFE is determined by a mrmber of methods, such as ASTM D758 or D2240 (Rockwell R Scale), or by Durameter scales. The mrmbers reported are Rockwell R Scale of 58, Durameter A Scale of 98, and Durameter D Scale of 50-65.P" Figure 3.25 illustrates the variation of hardness of PTFE and nylon as a function of temperatures. Both plastics become softer with increasing temperature but, in all temperatures, nylon is harder than PTFE. 

Rockwell R, L, M, E, K Buchholz hardness Vickers hardness Knoop hardness Scratch hardness... 

Flexural Modulus (Psi x 10 ) Compressive Strength (Psi) Hardness (Rockwell R)... 

Unlike other Rockwell scales, Rockwell R parameter correlates with the hardness as determined by ball indentation. Fett (1972) has shown that... 

---