Vulcanizate properties effect

The effect of palm oil fatty acid additive (POEA) on curing characteristics and vulcanizate properties of sdica-filled NR compounds was studied by Ismail [30]. The incorporation of POEA improved the cure rate and state of cure of the compounds. Compared to the control, the incorporation of POEA not only enhanced the vulcanizate properties but also improved the reversion resistance of the silica-filled NR compounds. 

Effect of Filler-Elastomer Interactions on Vulcanizate Properties.117... 

The addition of a wide variety of compounding ingredients to facilitate processing, effect vulcanization, and modify or improve vulcanizate properties, calling for tests for... 

Effects of changes in the concentrations of accelerator and sulfur on vulcanizate properties have been studied by using the following recipe (parts by weight) natural rubber, 100 N330 carbon black, 50 N-isopropyl-N -phenyl-p-phenylenediamine (IPPD antidegradant) 2 zinc oxide, 5 stearic acid, 3 plasticizer, 3 sulfur, variable N-cylohexylbenzothiazolesulfenamide (CBS), variable (Coran, 1978). 

The effects of concentrations of sulfur and accelerator on network structure and vulcanizate properties have been studied (McCall, 1969 Datta et al., 2007 Fan et al., 2001 Dijkhuis et al., 2009 Campbell, 1409 Cooper, 1958). The low values for fatigue life at low levels of sulfur, but high levels of accelerator. 

Fillers. Fillers for elastomers are not generally used just to fill space and cheapen the compositions. They are very important to modify the properties of rubber compositions in very positive ways. This is especially true for the so-called reinforcing fillers. Their presence in the compound can improve the strength- and durabihty-related properties of vulcanizates and can strongly enhance processing characteristics. The choice and amount of filler can have a profound effect on vulcanizate properties. These effects depend on several factors level of use (concentration), primary particle size, surface area (inverse function of primary particle size), and structure (shape factor, e.g., spherical, chain or rod-like, plate-like, and so forth). 

Although petroleum oils reduce compound viscosity, process aids are now available that are more effective in this respect at much lower levels of addition, so minimizing the effect on vulcanizate properties. These materials are as follows ... 

The processing of natural rubber with chemical peptizers both in single-stage, full-chamber mastication and as part of a mixing cycle (called in batch peptization) was investigated for efficiency of breakdown and possible effects of chemical peptizers on subsequent vulcanizate properties. 

SP rubbers find particular advantage when used in lightly loaded extruded or calendered products to the extent that even pure gum formulations can be processed as easily as heavily filled formulations. Particular benefits in extrusion are reduced die swell and faster throughput (Table 12). The effect of SP rubbers on vulcanizate properties is negligible. 

Crowt ier, B. G., Effects of process oils on the vulcanizate properties of a natural rubber tread stock, Nat. Rubber TechnoL, 14(2), 1983, 79. 

FIGURE 1.7 Effect of zinc oxide and magnesium oxide levels on compound and vulcanizate properties of CR. (Notes (a) All vulcanizates were cured 30 min at 150°C. (b) Formulation CR (medium fast crystallization grade) 100, stearic acid 0.5, PBNA 2, SRF N762 30, ETU 0.5. (c) Excerpt from technical information bulletin Baypren 2.2.1, Bayer AG.)... 

The potential for the formation of ionic crosslinks with Vamac terpolymers precludes the use of fillers that may contain soluble divalent metal ions. Metal stearates, metal stearate-coated fillers, clays, and precipitated silicas are not recommended for use in Vamac terpolymers. Precipitated fillers can contain impurities, which can lead to ionic bonding. Another potential source of soluble divalent metal ions is the pigment used to color mineral-filled compounds. Ionic bonds can significantly increase the viscosity of the uncured stock and increase the compression set of vulcanizates. The effect of metal ions and ionic bonds on stock and vulcanizate properties can vary considerably from batch to batch and is dependent on the impurity concentration in the lot of filler as well as the mixing/processing procedures. 

Types of Latex Compounds. For comparison with dry-mbber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural mbber latex compounds, including one without antioxidant, and data on tensile strength and elongation of sheets made from those, both before and after accelerated aging, are also Hsted. The effects of curing ingredients, accelerator, and antioxidant are also Hsted. Table 24 also includes similar data for an SBR latex compound. A phenoHc antioxidant was used in all cases. 

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