Reinforcement, and

Nitrile Rubber. Vulcanized mbber sheets of NBR and montmorillonite clay intercalated with Hycar ATBN, a butadiene acrylonitrile copolymer have been synthesized (36). These mbber hybrids show enhanced reinforcement (up to four times as large) relative to both carbon black-reinforced and pure NBR. Additionally, these hybrids are more easily processed than carbon black-filled mbbers. 

Concrete Products. Limestone aggregate is used competitively with other aggregate in the manufacture of molded, reinforced, and prestressed concrete products in the form of block, brick, pipe, panels, beams, etc. 

The interface region in a composite is important in determining the ultimate properties of the composite. At the interface a discontinuity occurs in one or more material parameters such as elastic moduli, thermodynamic parameters such as chemical potential, and the coefficient of thermal expansion. The importance of the interface region in composites stems from two main reasons the interface occupies a large area in composites, and in general, the reinforcement and the matrix form a system that is not in thermodynamic equiUbhum. 

Thermal expansion mismatch between the reinforcement and the matrix is an important consideration. Thermal mismatch is something that is difficult to avoid ia any composite, however, the overall thermal expansion characteristics of a composite can be controlled by controlling the proportion of reinforcement and matrix and the distribution of the reinforcement ia the matrix. Many models have been proposed to predict the coefficients of thermal expansion of composites, determine these coefficients experimentally, and analy2e the general thermal expansion characteristics of metal-matrix composites (29-33). 

Fig. 14. Reinforcement and crack tip kiteractions ki a particulate composite (a) coarse particles ki a strong particle—matrix kiterface, and (b) fine particles ki...

It is important to note that reinforced plastics remain a combination of materials differing in form or composition on a macro scale. The main constituents (resin, reinforcement, and filler) retain their identities and do not dissolve or merge into each other rather, they act in concert. These components can be physically identified and exhibit an interface between each other. 

Hand Lay-Up and Spray-Up. In hand lay-up, fiber reinforcements in mat or woven form are placed on the mold surface and then saturated with a Hquid polymer, typicaHy a polyester resin, that has been chemically activated to polymerize (cure) without the addition of heat. Multiple pHes of reinforcement and multiple cure steps aHow very heavy waH thicknesses to be achieved. 

PVC. Poly(vinyl chloride) (PVC), a very versatile polymer, is manufactured by the polymerisation of vinyl chloride monomer, a gaseous substance obtained from the reaction of ethylene with oxygen and hydrochloric acid. In its most basic form, the resin is a relatively hard material that requites the addition of other compounds, commonly plasticisers and stabilisers as well as certain other ingredients, to produce the desired physical properties for roofing use. The membranes come in both reinforced and nonreinforced constmctions, but since the 1980s the direction has been toward offering only reinforced membranes. The membrane thickness typically mns from 0.8—1.5 mm and widths typically in the range of 1.5—4.6 m. 

Reinforcing Resins. Reinforcement and stiffness of a compound can also be achieved with the use of reactive resins. Resins consisting of two-component systems of resorcinol or resorcinol condensation products and a methylene donor such as hexamethoxymethylmel amine (HMMM) or hexamethyltetramine (HMT) are the most popular in tires. These materials can be prereacted and added to the formula, or for more effective results they can react in situ ie, they can be added separately into the formula and react when the tire is vulcanized. 

G. CoraHo, "Historical Review of Light-Duty Tyre Carcass Reinforcement and the State of Current and Next Generation Technology," Conference Preprints ACS, PuhherTdivision, Philadelphia, Pa., May 1995, p. 13. 

Fibrous Glass. Fibrous glass is manufactured in two different forms, very fine intermingled fibers called insulation fibrous glass for insulation and fine but coarser fibers called continuous or textile fibers for reinforcement and other textile appHcations. Both products have constmction related apphcations. 

Calcium carbonate continues to be used in its original appHcation, putty, as weU as caulks, sealants (qv), adhesives (qv), and printing inks (qv). Large volumes are used in carpet backing and in joint cements. It is used to improve body, reinforcement, and other properties. 

Aromaticity is the most important property of a carbon black feedstock. It is generally measured by the Bureau of Mines Correlation Index (BMCI) and is an indication of the carbon-to-hydrogen ratio. The sulfur content is limited to reduce corrosion, loss of yield, and sulfur in the product. It may be limited in certain locations for environmental reasons. The boiling range must be low enough so that it will be completely volatilized under furnace time—temperature conditions. Alkane insolubles or asphaltenes must be kept below critical levels in order to maintain product quaUty. Excessive asphaltene content results in a loss of reinforcement and poor treadwear in tire appHcations. 

The consumption of the vanous carbon black grades can be divided into tread grades for tire reinforcement and nontread grades for nontread tire use and other mbber appHcations. Table 9 shows the distnbution of production of types for these uses. In the United States 55% production is for tread grades. In Western Europe tread-grade production is 64%, and in Japan it is 60%. 

Further reduction in the price of carbon fibers may enable penetration into the automotive market. A primary carbon fiber producer has armounced that prices will drop to 700 yen/kg ( 6.80/lb) by 1995 (73) and that cooperative development efforts with a main Japanese automobile producer are underway. Development for use in constmction, such as cement and cable reinforcement, and marine apphcations will result in sustained growth volume through the eady twenty-first century. 

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