Polyblends transparency

Using these techniques to prepare the resin and rubber components of polyblends, transparent impact polymer blends can be obtained which exhibit mechanical properties comparable with ABS materials. Like ABS, they have a fairly flat modulus curve, which varies gradually over a wide temperature range (Figure 4). Impact properties are outstanding for these transparent impact polymers even at temperatures as low as —40°C. 

The commercial success of ABS polymers has led to the investigation of many other polyblend materials. In some cases properties are exhibited which are superior to those of ABS and some of the materials are commercially available. For example, the opacity of ABS has led to the development of blends in which the glassy phase is modified to give transparent polymers whilst the limited light aging has been countered by the use of rubbers other than polybutadiene. 

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. 

Appearance of Fused Product. From the fabrication point of view, if two polymers give a smooth band on a two-roll mill, the polyblend is said to be compatible. If the fused product is cheezy, it is said to be incompatible. Frequently, the fused product is pressed into a flat sheet. Transparency of the sheet signifies compatibility, whereas an opaque appearance means incompatibility. Obviously, these criteria are arbitrary and crude. They are subject to great variation owing to difference in individual judgement. In addition, they give no information on the morphological feature of the system. 

The performance of polyblends is quite consistent with that of the two components alone. This might be expected owing to the high degree of ultraviolet transparency of each of the components polymers (Figure 10). Their retention of tensile strength and elongation is limited by the... 

Where the two phases are completely compatible, a homogeneous polyblend results which behaves like a plasticized resin (one phase). If two polymers are compatible, the mixture is transparent rather than opaque. If the two phases are incompatible, the product is usually opaque and rather friable. When the two phases are partially compatibilized at their interfaces, the polyblend system may then assume a hard, impact-resistant character. However, incompatible or partially compatible mixtures may be transparent if the individual components are transparent and if both components have nearly the same refractive indices. Furthermore, if the particle size of the dispersed phase is much less than the wavelength of visible light (requiring a particle size of 0.1/a or less), the blends may be transparent. 

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-... 

In an effort to interpret the morphology of these transparent polyblends, electron photomicrographs were made from microtomed cross sections of molded sheets. Such a photomicrograph is shown in Figure 7. 

Typical physical properties for an injection-molded transparent acrylic polyblend resin are given in Table II. The injection molding conditions used are given in Table III. Tensile, flexural, and impact properties are within the range reported for typical ABS and high impact polystyrene resins. Optical properties approach those of the acrylics [i.e., poly (methyl methacrylate)]. The strength properties are on the low side of those reported in the first paper for the transparent diene... 

A procedure (I) was described to examine the size of these rubber particles and the interparticle distance using laser light scattering which is uniquely applicable to transparent polyblends. This procedure is best... 

Acrylate rubbers such as poly (butyl acrylate) or poly (ethyl hexylacrylate) are characterized by better aging characteristics than polydienes. Ethyl hexylacrylate and acrylonitrile were grafted onto PVC in solution by R. G. Bauer and M. S. Guillord. They observed that this graft copolymer was transparent in contrast to a mere polyblend of PVC and an AN/acrylate copolymer. 

A given Cop is therefore a better emulsifier in a polyblend if smaller amounts are required to obtain transparent films, i.e., small particle size of the dispersed phase. In order to compare the emulsifying efficiencies of different polyblends, it is convenient to define the ratio of the molecular weights of the homopolymer and the corresponding component of the block copolymer as follows ... 

In these blends the counterion of the basic organic moiety acts as a surfactant and the covalently attached acidic group to this organic moiety forms a salt with an emeraldine macromolecule which can induce solute solvent interaction to give a tertiary system [9]. Cao et al [8] have reported that a complex of polyaniline and dopant can be co-dissolved in a common organic solvent at a desired ratio with a host polymer to form a solution of the polyblend. The polyblend can then be processed from solution to yield conducting transparent film/fibers with a electrical conductivities of about 1 S cm for a blend containing 2% polyaniline. This low volume of polyaniline required has been traced to a fibrillar well-connected network. 

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