Carbon black and titanium dioxide

The initial uses of colorants in plastics were as extenders and additives. Carbon black and titanium dioxide were and are stiU used as fillers (qv) because of their low cost. Almost from plastics inception the limitation of black and white did not offer sufficient color choices for end users looking to differentiate their products. The increase in aesthetic requirements along with different performance requirements and resin compatibiUties led to a great expansion in the number of different chemical classes of colorants and forms in which these colorants are available in today s market. 

Certain fillers are commonly added to protect the urethane backbone from oxidative degradation. Carbon black and titanium dioxide are commonly used in conjunction with antioxidants to protect polyether polyurethanes in exterior adhesive applications that may be exposed to oxygen and light (Fig. 12). 

Addition of low levels of certain additives to PBT can be a desirable way to enhance properties. The most common additives are colorants. Both pigments and dyes can be used to color PBT. Carbon black and titanium dioxide are most widely used. Carbon black and other pigments, for example, phthalocyanines, can also act as a nucleant for speeding crystallization. 

Heinrich, U., Fuhst, R., Rittinghausen, S., Creutzenberg, O., Bellmann, B, Koch, W., and Levsen, K. (1995). Chronic inhalation exposure of Wistar rats and two different strains of mice to diesel engine exhaust, carbon black, and titanium dioxide. Inhal Toxicol 7, 533-556. 

For the protection of the light sensitive IC devices, pigments are usually incorporated into the RTV encapsulant (such as low level of the carbon black and titanium dioxide). The main parameter that affects the RTV rheology may be filler incorporation and filler activity. Through the RTV silicone study, we have learned that the rheology of the RTV silicone is closely related to its coating performance. 

Potential adverse effeets calcium carbonate interferes with radiation curing, calcium caibonate may react with pollutant (SO2) to form sulfate, fillers eontaining cadmium, cobalt, copper, iron, lead, or nickel reduce thermal stabihty, low concentration of carbon black and titanium dioxide reduces UV stability, zinc oxide decreases thermal stability, zinc oxide in combination with carbon black reduces UV stability... 

Reasons for use coloring, protection against UV degradation (carbon black and titanium dioxide)... 

Much has been documented concerning the affect of colorants, primarily carbon black and titanium dioxide, on the properties of polymers. Polymers generally studied include polyolefins and ABS. Properties talked about are usually viscosity of color concentrates, color development and consistency, or occasionally mechanical properties. Unfortunately, little has been documented on the affect of colorants on engineering resins specifically, and their influence on mechanical properties in particular. 

The creation of Janus particles, with interesting asymmetric electrical properties, was reported by Nisisako et al. [2]. In this case, isobornyl acrylate was used as a hydrophobic, water-insoluble, monomer, and pigmented with carbon black and titanium dioxide as black and white colors, respectively (Figure 14.21). 

Fillers are mainly used for reasons of economy, but in many cases they also improve some properties of the polymer. The most important fillers for polymers are minerals such as talc, chalk and china clay. Filler content generally used with plastics is up to 60 wt%. The most common practice is to feed the filler downstream into the melt by means of a twin-screw side feeder (Figure 6.3). It is well-known that thermoplastic melts with high loadings of small particles such as calcium carbonate, carbon black and titanium dioxide give both yield values in shear flow [58, 59], and uniaxial extension [60, 61]. 

In solvent-borne rubber adhesives, a variety of solvents can be chosen to control drying rate, adjust viscosity and dissolve important ingredients. Resins can be added to improve tack, wetting properties, heat resistance, bond strength and oxidation resistance. The most common resins nsed in rubber-based adhesives are rosins, rosin esters, and terpene, coumarone-indene, hydrocarbon and phenobc resins. Plasticizers and softeners reduce hardness, enhance tack and decrease cost of rubber adhesive formulations. Paraffinic oils, phthalate esters and polybutenes are typical plasticizers. Fillers are not often added to rubber adhesive formulations because they reduce adhesion. However they are sometimes used because they decrease cost and increase solution viscosity. Carbon black and titanium dioxide are also used to provide colour to the adhesives. Clays, calcium carbonate and silicates are also common fillers in rubber adhesive formulations. For water-borne adhesives, typically protective colloid, preservative, defoamers, wetting agents and emulsifiers are included in the formulations. 

It should be noted that Figures 7.1 and 7.2 are plotted as Ni vs. rather than Nj vs. y. Where the latter representation was used then the data would appear as shown in Figure 7.3(a). Orxly curves for particulate fillers - titarxium dioxide and carbon black - are shown for illustration purposes. It can be seen that both these fillers appear to increase normal stress differences of the polymer melt at the same shear rate. Thus from Figure 7.3(a) it can be concluded that small particulate fillers like carbon black and titanium dioxide increase the elasticity of polymer melts. This is contrary to the trend in Figure 7.1 for the same filled systems using the same data but different representation wherein... 

Figura 7.3(a) Variation of primary normal stress difference with shear rate for filled polystyrene melts containing 20 volume fraction of carbon black and titanium dioxide fillers. (Reprinted from Ref. 27 with kind permission from Society of Plastics Engineers Inc., Connecticut, USA.)...

S. Hussain, S. Boland, A. Baeza-Squiban, et al.. Oxidative stress and proinflammatory effects of carbon black and titanium dioxide nanoparticles role of particle surface area and internalized amount. Toxicology 260 (1-3) (2009) 142-149. 

S. Hussain, L.C.J. Thomassen, I. Ferecatu, et al.. Carbon black and titanium dioxide nanoparticles elicit distinct apoptotic pathways in bronchial epithebal cells. Particle Fiber Toxicol. 7 (2010) 10. 

Salem, M.A. Mechanical properties of UV-irradiated low-density polyethylene films formulated with carbon black and titanium dioxide. Egypt. J. Solids 24, 141-150 (2(K)1)... 

UV absorbers have been well known for a long time as light stabilizers of polymers. Materials such as carbon black and titanium dioxide can prolong the service life of polymer articles. In applications where transparency is necessary, however, these materials are often not an option. 

---