Лако-красочные материалы — производство

The differences between emulsion and solution polymerized SBRs are significant, although they do share the following similarities.

Superior water and moisture resistance While not recommended for immersion applications, and not as resistant as butyl compounds, these polymers are not affected by most aqueous chemicals.

Ease of dispersion Both emulsion and solution grade polymers are easily dispersed in aliphatic and aromatic solvents and solvent blends, and provide low viscos­ity, high solids content formulations, with low mixing costs. However, the opposite side of this feature is a poor resistance to organic solvents and oils, even when vulcanized.

Good heat resistance Emulsion grade polymers are equal to or better than natural rubber, while block copolymers are superior to natural rubber and emulsion grade SBRs. Block copolymers also are often superior for resistance to cold temperatures.

Low building tack An inherent characteristic of SBR elastomers, which normally requires the addition of tackifying resins, low molecular weight polymers, or plasticizers, or master batch processing.

Excellent substrate compatibility Properly compounded adhesives, sealants, and pressure sensitive materials will adhere to almost any surface. Block copoly­mers have exhibited superior pressure sensitive adhesion to polyolefin and other low energy surfaces.

Fair to good aging Cured products often will outperform natural rubber products, but uncured products made from emulsion polymers can degrade rather quickly if not compounded for UV, ozone, and oxygen resistance. Block copo­lymers are typically better in the uncured state than standard SBR, but still require protectant additives for extended exposure conditions.

Good processing characteristics Adhesives are often used as a contact bond type— either in water — or solvent-based systems—as a hot melt, or as a pressure sensitive, in curing systems, or as heat or solvent reactivatible systems. Block copolymers provide superior pressure sensitive adhesives, but can also be com­pounded for contact bond adhesive or sealant applications.

Curability Typically, these are sulfur cured at elevated temperatures, but can be cured by other mechanisms for higher heat resistance and better strength and aging properties.

Low cost Emulsion polymers are low cost compared to most other synthetic elas­tomers. Also they can be compounded with a variety of low cost fillers for sealant and low bond strength applications.