Rubber-resin blend

More systematic study of resin-rubber blends was reported by Class and Chu. i i ) It revealed the relationship between the structure, concentration, and molecular weight of the resin and their effect on the viscoelastic properties of the rubber-resin composition. These authors also attempted to correlate the viscoelastic properties of the adhesives and its PSA... 

Three different resin-rubber blend systems were examined by frequency scan at room temperature. First, we examined blends of natural rubber with a compatible aliphatic oil. Figure 44 shows G vs. frequency at various loadings of oil to natural rubber. As we add oil, the modulus curve as a function of frequency is depressed. This is to be expected as the oil softens the composition which, in turn, causes the reduction of the modulus. In other words, oil does not change the tan 8 peak (7g) temperature of natural rubber it only reduces the room-temperature modulus value of natural rubber. Consequently, it does not function as an effective tackifying resin. 

Polymers can exist in a number of states. They may be amorphous resins, rubbers or fluids or they can be crystalline structures. TTie molecular and the crystal structures can be monoaxially or biaxially oriented. Heterogeneous blends of polymers in different states of aggregation enable materials to be produced with combinations of properties not shown by single polymers. 

Tackifying resins enhance the adhesion of non-polar elastomers by improving wettability, increasing polarity and altering the viscoelastic properties. Dahlquist [31 ] established the first evidence of the modification of the viscoelastic properties of an elastomer by adding resins, and demonstrated that the performance of pressure-sensitive adhesives was related to the creep compliance. Later, Aubrey and Sherriff [32] demonstrated that a relationship between peel strength and viscoelasticity in natural rubber-low molecular resins blends existed. Class and Chu [33] used the dynamic mechanical measurements to demonstrate that compatible resins with an elastomer produced a decrease in the elastic modulus at room temperature and an increase in the tan <5 peak (which indicated the glass transition temperature of the resin-elastomer blend). Resins which are incompatible with an elastomer caused an increase in the elastic modulus at room temperature and showed two distinct maxima in the tan <5 curve. 

The chemical nature of the tackifier also affects the compatibility of resin-elastomer blends. For polychloroprene (a polar elastomer) higher tack is obtained with a polar resin (PF blend in Fig. 27) than with a non-polar resin (PA blend in Fig. 27). Further, the adhesion of resin-elastomer blends also decreases by increasing the aromatic content of the resin [29]. Fig. 28 shows a decrease in T-peel strength of styrene-butadiene rubber/polychloroprene-hydrocarbon resin blends by increasing the MMAP cloud point. Because the higher the MMAP... 

For resistance to acid conditions alone, traditional filled and unfilled bituminous solutions (which have economic advantages), chlorinated rubber and shellac have been used. Crosslinking coatings, e.g. amine-cured epoxy resins, often blended with coal-tar which develops resistance to oils and solvents, have obvious advantages on chemical plant. 

Blends of natural rubber or styrene-butadiene rubber with high styrene resins used as soling material in footwear manufacture. Such resin rubbers should not be confused with... 

Table II. Effect of Graft Resin on Blend Optical Properties (Resin—Backbone Rubber = 2.5—1.0)...

This section focuses on the modification of epoxy resins by blending with acrylonitrile butadiene (nitrile) resins. These are true alloyed blends since the nitrile rubber usually contains no groups that are normally reactive with epoxy groups. The nitrile molecules and the epoxy molecules intermingle as a blend to provide a single-phase alloy. If a large elastomer concentration is used, no phase separation will occur to form precipitates. 

Blends with Nitrile Rubbers. The data in Table III show the importance of using a terpolymer rubber to obtain good impact strength in a blend with styrene-acrylonitrile-DBPF terpolymer resin. Blend No. 1 gives the properties of a conventional nitrile rubber blend type ABS. Blends 2-4, involving terpolymer resins with the same amount of the rubber used in Blend 1, have a much lower impact strength. 

If, however, terpolymer resin is blended with terpolymer rubber (Blends 5-7), the impact strength approaches that of the conventional... 

SR-7475. [Firestone Syn. Rubber] Buta-dbne-styrene cqpolymer rubber blend-aUe modifier for thermoplastic resins and asphalt... 

Natac . [Whitney Oettler] Resin ac-ids-amine resin sotqjs blend tackifier for rubber molding aid inhibits bloom in NR and NR/SBR blends. 

Turgum . [Whitney Oettler] Tur-pene-resin add blend plasticizer and condidtmer ftn SBR retarder fw furnace bladc/rubber stocks. 

Even in the phase separated blends, where some degree of partial miscibility or compatibility exists between the components, simple melt blending in an intensive shear mixer is adequate for making a well dispersed, reasonably stable blend product with useful combination of properties, such as polypropylene/ethylene-propyl-ene rubber blend, ABS/polycarbonate blend, etc. The self-compatibUizing nature of these blends stems from partial miscibility and the mutual interpenetration of polymer chains at the interface. Slight modifications of the polymer backbone are often employed, particularly in the case of styrenic and ABS resins to induce partial miscibility with other resins. 

A commercial blend of SMA and polycarbonate (Arloy , ARCO) was offered for some time, but recently it was discontinued. The polarity of SMA copolymer may account for the good degree of compatibility between the two resins. The blend contained the polybutadiene rubber normally used in SMA resins for impact strength. It exhibited good low temperamre impact strength (Table 15.8) and in many properties was similar to ABS/PC blend. 

Gupta et al. (39) has studied the effect of dynamic cross-linking on tensile yield behavior of PP/EPDM rubber blends. They prepared blends of PP/EPDM in internal mixer by simultaneous blending and dynamic vulcanization. Dimethyl phenolic resin vulcanized PP/EPDM blends showed higher yield stress and modulus than unvulcanized PP/EPDM blend (Fig. 14.17 and Table 14.1). They found the increase in... 

Drying sealants are represented by solutions of rubber blends in organic solvents. As soon as the solution is impregnated into the clearance and the solvent evaporates, the sealant becomes rubbery and gains elasticity. The original compositions contain adhesive additives (coumarone, terpenic and phenolic resins, rosin or its esters), PI and solvents (toluene, xylol, benzine, etc.), fillers (chalk, titanium dioxide, talc, etc.) and stabilizers. These compositions can be easily impregnated with Cl [15]. 

Notable among the thermoplastic materials are polyethylene, polypropylene, polyvinyl chloride, the styrene synthetic rubber blends, the acrylics, and the fluorocarbons. Notable among the thermosetting reinforced materials are the polyesters, epoxy, and the furan resins as custom-made reinforced materials, and the phenolic and epoxy resins molded, filament-wound, and/or extruded with reinforcement. AU these materials are available as piping, sheet stock, and miscellaneous molded and fabricated items. These materials, particularly polyvinyl chloride, polypropylene, and reinforced polyesters, are now being used extensively for ventilating ductwork in handling corrosive fumes. They have proved to be economically improved over metals such as stainless steel, lead. 

As the concentration of a normally compatible resin is increased in a rubber-resin blend, a level is reached where two phases appear. Natural rubber blended with a poly (vinyl cyclohexane) resin and styrene-butadiene rubber blended with a polystyrene resin, systems which were compatible at the 50% resin level, appear to have two phases at the 75% resin level. 

Plots of the styrene-butadiene rubber blends give higher values of 2.45 to 2.65 for the exponent, as shown in Fig. 25. A possible explanation is that the styrene-butadiene rubber contains gels that do not participate in the dilution by the resin. Therefore, the resin concentration in the amorphous phase is higher than calculated which would reduce the modulus more than expected. This would result in an apparent higher power for the polymer volume fraction. 

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