Rubber filled graft

Rubber-resin heterophase systems are classified as (1) resin as the disperse phase, (2) rubber as the disperse phase, (3) grafted rubber latex particles as the disperse phase, and (4) filled graft rubber as the disperse phase. Adhesion mechanisms related to these systems are discussed. Special emphasis is made on the last two systems which involve grafting. The graft rubber isolated from the fourth system is characterized. The graft rubber is shown to function as a compatibilizer and as an adhesive or a coupling agent for the rubber-resin interface. 

Filled Graft Rubber as the Disperse Phase. Rubber-modified polystyrene is generally obtained by polymerization grafting of a rubber in the presence of styrene monomer. The polymerization is carried out totally or partially in mass with the aid of shearing agitation, as patented by Amos et al. (1). The study on the initial stage of this type of polymerization was first published by Bender (5), and phase inversion similar to that discovered for the two-phase pressure-sensitive adhesives was observed. The mechanism of particle formation has also been reviewed (47). 

The rubber particles were examined with an electron microscope after the sample was treated with osmium tetroxide (27). The micrograph (Figure 7) clearly indicates the porous nature of the rubber phase and the occlusion of polystyrene. We therefore classify this type of rubber phase as filled graft rubber. Since grafting takes place before and after the rubber chain is coiled, therefore, for this case, the monomer is grafted onto the rubber both within and without the rubber phase. Polybutadiene is thus made more compatible to the polymer matrix surrounding the rubber phase and the polymer filling the rubber phase. Here we have an... 

The results are shown in Fig. 9. A small amount of the filler strongly increases the energy contribution which is in full contradiction to the assumed increase in the concentration of active network chains caused by the filler. Curve 2 summarizes the results for filled PDMS rubber and for PDMS block and graft copolymers. It is seen that below 20% of the filler or hard phase, the energy contribution is practically independent of the amount of hard phase, but then a considerable increase of (AU/W)v>t is observed. Although in all these cases the energy contribution is... 

Since these rubber particles are highly filled with a homopolymer or a copolymer, the rubber is already reinforced with a resin to give a higher modulus particle than the grafted rubber latex. On the basis of the uniqueness of these rubber particles, this process is also more appropriate in manufacturing high-strength medium-impact ABS polymer (31), or rubber-reinforced styrene-methyl methacrylate copolymer (32). The... 

This article reviews recent developments in polymer thermomechanics both in theory and experiment. The first section is concerned with theories of thermomechanics of polymers both in rubbery and solid (glassy and crystalline) states with special emphasis on relationships following from the thermomechanical equations of state. In the second section, some of the methods of thermomechanical measurements are briefly described. The third section deals with the thermomechanics of molecular networks and rubberlike materials including such technically important materials as filled rubbers and block and graft copolymers. Some recent data on thermomechanical behaviour of bioelastomers are also described. In the fourth section, thermomechanics of solid polymers both in undrawn and drawn states are discussed with a special focus on the molecular and structural interpretation of thermomechanical experiments. The concluding remarks stress the progress in the understanding of the thermomechanical properties of polymers. 

Fig. 9. Dependence of the energy contribution on the filler (filled rubbers) or hard phase (thermo elastoplastics) content. 1 — filled silicone rubber1221 Sil-51 (A), Sil-4600 ( ) multiblock copolymer polyarylate-PDMS (O) us) graft copolymer of PDMS and AN ( x) 128>. 2 — Butyl rubber with high abrasion furnace black125). 3 — Butyl rubber with medium thermal black 125). 4 — SBR-filled rubber 126). 5 — aerosil //j Si-filled silicon rubber138). 6 — EPR-filled rubber 129,130). 7 — plastisized PVC filled with aerosil131132). 8 — SBS block copolymers 134)...

The mobility in both tightly and loosely bound BR and isoprene rubbers increases, and the fraction of bound rubber decreases with a decreasing concentration of silanol groups on the silica surface [124], This led to the suggestion that the silanol groups on the silica surface are active sites for the chain adsorption. The grafting of aliphatic chains to the silica surface leads to a decrease in BR-silica interactions [125]. The effect is less pronounced in BR filled with carbon black containing aliphatic chains at the surface. 

Water can be removed from methanol by a membrane of polyvinyl alcohol cross-linked with polyacrylic acid, with a separation factor of 465.204 A polymeric hydrazone of 2,6-pyridinedialdehyde has been used to dehydrate azeotropes of water with n- and /-propyl alcohol, s- and tort butyl alcohol, and tetrahydrofuran.205 The Clostridium acetobutylicum which is used to produce 1-butanol, is inhibited by it. Pervaporation through a poly(dimethyl-siloxane) membrane filled with cyclodextrins, zeolites, or oleyl alcohol kept the concentration in the broth lower than 1% and removed the inhibition.206 Acetic acid can be dehydrated with separation factors of 807 for poly(4-methyl-l-pentene) grafted with 4-vinylpyridine,207 150 for polyvinyl alcohol cross-linked with glutaraldehyde,208 more than 1300 for a doped polyaniline film (4.1 g/m2h),209 125 for a nylon-polyacrylic acid membrane (5400 g/m2h), and 72 for a polysulfone.210 Pyridine can be dehydrated with a membrane of a copolymer of acrylonitrile and 4-styrenesulfonic acid to give more than 99% pyridine.211 A hydrophobic silicone rubber membrane removes acetone selectively from water. A hydrophilic cross-linked polyvinyl alcohol membrane removes water selectively from acetone. Both are more selective than distillation.212... 

Research efforts on filled polymer blends have been more focused on nanopartide-filled systems [42, 43]. One usual observation is the same as those with microscopic fillers - polar nanofillers localize in more polar phases [44—53]. In cases where both phases are polar or nonpolar, the filler particles have been observed to be expelled from both phases in the blend [54—56]. Selective localization of nano-sized partides has been an interesting topic of research. We discuss some of the results here. Gahleitner et al. [57] observed a preferential localization of clay particles in PA6 droplets in PA6/PP blends. Recall that day, espedally montmorillonite, is highly polar in both its pristine and various organically modified forms [58-62]. Similarly, Wang et al. [63] reported selective localization of clay particles in maleic anhydride grafted ethylene-propylene-diene (EPDM-MA) rubber droplets in poly(trimethylene terephthalate)/EPDM-MA blends. Selective localization of fillers other than clay particles has also been reported. Eor instance, Ou and Li [64] observed that toluene diisocyanate modified titania particles selectively localized in PA6 droplets in PP/ PA6/titania blends. 

In the rubber industry the distribution of particle size is considered to be important as it affects the mechanical properties and performance. Aggregate size also varies with particle size. Aggregates can have any shape or morphology. The fundamental property of the filler used in a filled elastomer is the particle size. This affects the reinforcement of elastomer most strongly. One of the sources of reinforcement between the carbon black surface and the rubber matrix is the van der Waals force attraction. Also, rubber chains are grafted onto the carbon black surface by covalent bonds. The interaction is caused by a reaction between the functional group at the carbon black particle surface and free radicals on polymer chains. Hence, filler-rubber interface is made up of complex physical-chemical interaction. The adhesion at the rubber-filler interface also affects the reinforcement of rubber. When the polymer composites are filled with spherical filler (aspect ratio of the particle is equal to unity), the modulus of the composite depends on the modulus, density, size, shape, volume ratio, and number of the incorporated particles. 

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