Rubber latex effect

Methylinositol, one of the constituents of natural rubber latex. Although it is present at about 1% it does not appear to have any effect on the properties of either field latex or concentrated latex. 

Alkyl alkoxy silanes have been found to be very effective in reducing alkali-aggregate expansion [11] (Fig. 6.4). Of the silanes used in the study, hexyl trimethyl siloxane and decyl trimethoxyl silane were found to be more effective in decreasing the expansion than the others. In the same study, Ohama et al. [11] investigated the effect of sodium silicofluoride, alkyl alkoxy silane, lithium carbonate, lithium fluoride, styrene-butadiene rubber latex and lithium hydroxide on compressive strength and the expansion of mortar containing cement with 2% equivalent Na20. The reduction of the level of expansion shown in Fig. 6.4 with the siloxanes was attributed to... 

Types of Latex Compounds. For comparison with dry-rubber compounds, some examples of various latex compounds and the physical properties of their vulcanizates are given in Table 23. Recipes of natural rubber 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 listed. The effects of curing ingredients, accelerator, and antioxidant are also listed. Table 24 also includes similar data for an SBR latex compound. A phenolic antioxidant was used in all cases. 

Most ABS is made by emulsion polymerization. A polybutadiene or nitrile rubber latex is prepared, and styrene plus acrylonitrile are grafted upon the elastomer in emulsion. The effect of rubber particle size in ABS graft copolymer on physical properties is the subject Chapter 22 by C. F. Parsons and E. L. Suck. Methyl methacrylate was substituted for acrylonitrile in ABS by R. D. Deanin and co-workers. They found a better thermoprocessability, lighter color, and better ultraviolet light stability. 

The purpose of this paper is to summarise results which have recently been obtained for the effects of various soaps and surfactants upon the mechanical and chemical stability of natural rubber latex, and to indicate the inferences which have been drawn in the course of endeavouring to interpret these observations. 

The ability of a soap or surfactant to enhance the chemical stability of natural rubber latex was assessed by ascertaining its effect upon the mechanical stability of natural rubber latices whose stabilities had been reduced by various chemical modifications. Natural rubber latices of reduced stability were produced in three different ways as follows ... 

Effects of added fatty-acid soaps upon mechanical and chemical stability of natural rubber latex (1,2,5)... 

Saturated straight-chain fatty-acid soaps (1). Figure 1 shows the effects of increasing levels of various potassium saturated straight-chain fatty-acid soaps upon the mechanical stability of natural rubber latex. For convenience of making comparisons between the various soaps, the levels of added soap are expressed as moles per 100 g. of latex solids. 

The results summarised in Table I show the effect of equal parts by weight of each of the potassium fatty-acid soaps upon the mechanical stability of each of the three chemically-destabilised latices. For convenience in making comparisons, estimates of the corresponding results for unmodified natural rubber latex are also included. It is clear from these results that the ability of added potassium fatty-acid soaps to enhance the stability of chemically-destabilised natural rubber latex roughly parallels their abilities to enhance the mechanical stability of unmodified natural rubber latex. 

Figure 2. Effect of alkyl chain length of added soap upon mechanical stability of natural rubber latex at four molal levels of addition (A) 0.84 X 10 4 (B) 2 X 10 4 (C) 3.36 X 10 4 (D) 4.20 X 10 4 mol/100 g of latex solids (1)...

Figure 3. Effect of various straight-chain potassium C18 carboxylate soaps upon mechanical stability of natural rubber latex (2) (KCt8) potassium stearate (KC18) potassium oleate (KC18") potassium elaidate (KC18Z) potassium linoleate (KC=ZZ) potassium linolenate (KC1H12(oli)) potassium 12-hydroxy stearate ...

The abilities of the five laurates to protect natural rubber latex against chemical destabilisation appear to be broadly parallel to their effects upon mechanical stability. 

We have also recently discovered that added calcium laurate is able markedly to enhance the mechanical stability of natural rubber latex (2.). This observation is surprising, partly because of the low solubility of calcium laurate in water, and partly because calcium ions are known to be powerful destabilisers of natural rubber latex (j ). It indicates that the stabilising effect of the laurate anion is much greater than the destabilising effect of the calcium cation. 

It is important to point out that our investigation of counterion effects in carboxylate soaps has so far been concerned almost exclusively with laurate soaps. Laurate soaps were chosen partly because they are generally convenient to handle in that many of them are readily soluble in water to give solutions of low viscosity, and partly because, as has been shown above, laurate soaps are very effective in enhancing the mechanical and chemical stability of natural rubber latex. It must therefore be borne in mind that the conclusions which have been drawn from this investigation concerning effects attributable to counterion variation in laurate soaps may not be generally valid for carboxylate soaps as a family. 

The effects of a range of sodium n-alkyl sulphates and sodium n-alkyl sulphonates upon the mechanical stability of natural rubber latex are summarised in Figures 4 and 5 respectively. As in the case of added potassium fatty-acid soaps, small additions of... 

Some data are also available for the effect of the counterion of a dodecyl sulphate upon its ability to enhance the mechanical stability of natural rubber latex. As in the case of the laurates the lithium, sodium, potassium and ammonium salts are similar in behaviour, but the morpholinium salt is slightly less effective. Again, the latter effect is attributed to specific adsorption of the morpholinium cation. Calcium and magnesium dodecyl sulphates are also effective in enhancing mechanical stability, their abilities being similar to that of morpholinium dodecyl sulphate. 

Some interesting results have recently become available for the effects of a range of n-alkyl triethyl ammonium bromides upon the mechanical stability of natural rubber latex. The number of carbon atoms in the alkyl group varied from 6 to 18. Figure 6 summarises the results. It is usually believed that the addition of cationic surfactants to an anionic latex such as natural rubber latex invariably leads to a reduction in colloid stability, the effect being attributed to adsorption of the cations with consequent partial neutralisation of the particle charge and reduction of the counterion cloud surrounding the particles. 

Figure 6. Effect of added n-alkyl triethyl ammonium bromides upon mechanical stability of natural rubber latex (9). Numbers appended to curves are numbers of carbon atoms in n-alkyl chain of surfactant.

The results summarised in Figure 7 show that small additions of ethylene oxide-fatty alcohol condensates to natural rubber latex generally cause the mechanical stability of the latex to fall. This phenomenon is attributed to the displacement of adsorbed proteinaceous molecules by the condensate molecules. Although the latter are more surface active than the former, they are presumably less effective in conferring mechanical stability upon the rubber particles, perhaps because, unlike the proteinaceous molecules, they are not ionised. 

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