Polyblend grafts

The SA polymer exhibited a two-phase structure in which the filler particles of radius ca. 0.26 /x are dispersed in the plastic matrix. The impact and tensile behavior of this polyblend was compared with that of an MBAS polyblend (graft diene rubber approximately the same size) which was examined previously by the laser light scattering technique. 

The mechanical properties of two-phase polymeric systems, such as block and graft polymers and polyblends, are discussed in detail in Chapter 7. However, the creep and stress-relaxation behavior of these materials will be examined at this point. Most of the systems of practical interest consist of a combination of a rubbery phase and a rigid phase. In many cases the rigid phase is polystyrene since such materials are tough, yet low in price. 

N. Polyblends, block, and graft polymers IJ. Brittle Fracture and Stress Concentrators... 

The photomicrographs show that the characteristic granular structure of polyblends is absent for copolymers. Moreover, the rather uniform appearance achieved once the graft has been heated, remains unchanged upon further temperature cycling. This offers additional evidence that microphase separation cannot take place at higher temperatures. 

Rigid impact poly (vinyl chloride) can be made either by polyblending or by grafting. P. Dreyfuss, M. P. Dreyfuss, and H. A. Tucker, discuss in their chapter polyblends of poly (vinyl chloride) with polyethers. F. Wollrab, F. Declerck, J. Dumoulin, M. Obsomer, and P. Georlette review grafting of vinyl chloride upon polyethylene, ethylene/ propylene rubber, and chlorohydrin rubber. 

Elastomeric graft copolymers of methyl methacrylate upon diene and acrylic rubbers were prepared by R. G. Bauer and co-workers. These elastomers are compatible with rigid methyl methacrylate-styrene copolymers of identical refractive index, yielding transparent polyblends. 

Table III. The Effect of Graft Resin on Polyblend Mechanical Properties (Resin—Backbone Rubber Ratio = 2.5—1.0)...

The importance of the graft handle on a 62/38 butadiene-methyl methacrylate rubber can be illustrated by its effect on the optical properties of the polyblend. From Table II it can be seen that the reduction in percent haze is dramatic for an increase of methyl methacrylate graft from 0 to 27% by weight, while there is no apparent change in the light transmission. The blend resin in this polyblend system was an 88-12 methyl methacrylate-styrene copolymer, and the total resin to backbone rubber ratio was kept at 2.5-1.0. The measured refractive indices are included for each component (the graft rubber and the blend resin). The difference in refractive index amounts to no more than 0.004 unit for any of the components. 

The effect of the graft resin on the polyblend mechanical properties for this same system (2.5-1.0 resin-backbone rubber) can be seen in Table III. 

Typical mechanical properties for transparent injection-molded polymers, designated MBAS, having a compositional range of from 11-18%, 1,3-butadiene, 34-39% styrene, and 23-25% each of acrylonitrile and methyl methacrylate are given in Table IV. This polymer is closely akin to the polyblend described previously, differing by containing a butadiene-styrene elastomer backbone, with a terpolymer resin graft consist-... 

By combining the concepts of copolymer homogeneity, matching refractive indices, and partial compatibilization via grafting, impact resistant polyblend systems can be produced from numerous monomer combinations that approach optical clarity. 

Grafting had the same beneficial effect in producing the necessary interdispersion of phases as that observed for a diene rubber polyblend. The feasibility of grafting a monomer to a saturated backbone was considered adequate for this particular system, based on reported studies of similar systems (6,7,8). 

Tensile Strengths. Table VI contains the tensile strengths of the polyblends corresponding to the impact values of Table V. Fluctuations are small since the weight ratio of grafted copolymer to substrate is reasonably constant. Tensile strengths of the 1100 A substrate polyblends... 

The possibility of fracture on impact can be reduced by dispersing an elastomeric phase uniformly through the rigid material, as it is done in polyblends or better in grafting vinyl monomer upon rubber. H. Bartl and D. Hardt describe the manufacture of a tough rigid PVC by grafting vinyl chloride upon an elastomeric ethylene—vinyl acetate copolymer. 

Cellulose is an old polymer with new industrial applications. The derivatization of cellulose has opened up tremendous production and marketing possibilities for the adhesives industry. Various important adhesives have been derived from cellulose ethers. The structure and molecular size of cellulose and their influence on swelling and solubility are important considerations in the preparation of cellulose derivatives for adhesive applications. Modern cellulosic adhesives derived from grafted copolymers and polyblends are also proving very useful. 

Cellulose constitutes a ubiquitous and renewable natural material that has great potential for chemical conversion into high-quality adhesive products. The resurrection of research and development of cellulose derivatives, such as cellulose esters and ethers, cellulose graft-copolymers, and cellulose polyblends, has instituted new avenues for adhesive applications. There is little doubt that new solvent systems for cellulose have created the potential of developing uniform cellulose products with superior properties for adhesive applications. 

It is well known that systems like polystyrene or polystyrene-acrylonitrile—generally considered brittle materials—have a remarkable increase in toughness and resistance to impact when polyblended with finely dispersed, crosslinked, but partly compatible, rubber particles. These particles are generally 0.1-10 fi in size and frequently consist of butadiene which has been grafted with monomers of similar composition to the matrix or continuous phase. 

Copolymerization techniques offer the opportunity to control polymer structure and hence the degree of mixing of the components. The multiphase physical characteristics of polyblends are also observed in graft, block, and heterogeneous copolymers (4, 5). Materials suitable for broad temperature range viiBration damping have been prepared from polyblends (4, 6, 7), graft copolymers (2, 8), and IPN s. 

Because no termination step exists, styrene/butadiene/styrene (SBS) triblock polymers can easily be made by charging styrene, butadiene, and again styrene, in succession, to the catalyst. Because the polystyrene blocks behave like styrene homopolymer, these triblock polymers are not suitable for use in automobile tires, but they lend themselves well in polyblends and as the backbone in the graft polymerization of Impact polystyrene and ABS... 

---