Rubber impact resistance tests

According to Partridge [163], toughening is efficient when, by comparison to the neat homopolymer tested under the same conditions, the impact resistance is multiplied by a factor of 10, without losing more than 25% of stiffness. The upper temperature limit for the use of rubber-modified blends is controlled by the matrix melt temperature, Tm, their lower limit by the glass transition temperature, Tg, of the particles. As soon as the viscoelastic response of the latter is too slow to accommodate an external loading, the polymer assumes a glassy state and breaks in a brittle way. 

At lesser rubber levels, heavy duty solventless coatings models based on dlethylenetrlamlne or fatty polyamide cures, showed elastomer-modification (10 phr rubber level) to advantage in Gardner impact, mandrel bend and corrosion-resistance testing (41). Impact testing (direct and reverse) gave 110 and 60 in-lbs, respectively for the rubber-modified fatty polyamide cured epoxy coating (14 days at R.T.), whereas a control formulation tested 10 in-lbs in each mode. 

Donskoi and co-workers [54] showed that each of the components of a chlorosulfonated polyethylene (CSPE) mix has its own influence on the fireproofing properties and chemical processes that occur. In this case, the thermal properties of the vulcanisates of CSPE were studied, and also the heat flows from the flame on the surface of the specimen. It was established that the thermooxidative breakdown of CSPE and vulcanisates based on it during heating under dynamic conditions, is a multi-stage process. The results of tests involving various fillers and plasticisers made it possible to create rubber-like, high-impact resistant materials. 

If the glass transition temperature increases at about 6 to 7°C per decade of frequency, the effective glass transition temperature of the rubbery phase is increased about 60°C above values measured at low frequencies, about 10 Hz. This calculation, while grossly oversimplified, suggests that the Tg of the elastomer phase must be about 60°C below the test temperature, which correlates well with the experimental evidence (see Table 11.4) (18). Thus, if the impact experiments are done at about 20°C, the glass transition of the rubber must be below about -40°C in order to attain significant improvement in impact resistance (21). 

Safety shoes need to be sturdy and have an impact-resistant toe. In some shoes, metal insoles protect against puncture wounds. Additional protection, such as metatarsal guards, may be found in some types of footwear. Safety shoes come in a variety of styles and materials, such as leather and rubber boots and oxfords. Safety footwear is classified according to its ability to meet minimum requirements for both compression and impact tests and need to meet ANSI standard Z41. 

Impact Strength - Impact strength or impact resistance is the measure of a hard rubber s resistance to fracture imder sudden impact or force. The impact force is one of compression on one side of the rubber and tension on the other, so that fracture is a result of failure similar to that occuring when a tensile sample is elongated to break. The same filler-elastomer consideration as in tensile and flexural testing therefore apply. 

Bis(2,3-dibromopropyl) fumarate has been used as a fourth monomer in nitrile rubber- and graft-type ABS materials giving flame-resistant polymers. At least 10% bromine incorporation is required to pass the Underwriters Laboratories Subject 94 test. The graft-type materials fail at 7-10% bromine only because of dripping. Both types pass the ASTM D-635 test with 7% or more bromine. For the impact strength to be equivalent to that of conventional ABS, the fourth monomer must be present in both the rubber and resin phases. Thermal stability is marginal but can be improved with typical PVC stabilizers. 

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