•1-10 MATERIALS AND MOLDING METHODS 



Sizes, Finishes and Binders 



The terms size, finish and binder, due to the nature of their functions have been fre- 

 quently confused by the end users of fiberglass. A size is a chemical treatment applied dur- 

 ing manufacture to fiberglass filaments immediately after they are formed by drawing 

 through the bushing orifices. A finish is a chemical treatment applied to a cloth after it is 

 woven and cleaned. A binder is a bonding resin used to hold the chopped strands of fiber- 

 glass together in a mat or preform, during manufacturing, handling and molding. 



Sizes and finishes are usually methacrylato chromic chloride types or unsaturated 

 hydrolysis products of vinyl trichlorosilane (2, 7). These sizes and finishes are commonly 

 known as "chrome" and "silane" types. Fiberglass filaments, used in the manufacture of 

 mats, preforms and rovings, are usually sized with chrome or silane at the fiber forming 

 machine. 



The chief function of chrome and silane sizes and finishes is to improve the chemical 

 bond between the molding resin and the glass filaments in the reinforcements. For the 

 weaving of glass cloth, a different type of sizing is required to lubricate and hold the strand 

 of filaments together during the weaving process. This sizing consists of oil, wetting agents 

 and starch applied to the glass filaments during the forming operation. The lubricating 

 action of this size assists in the weaving process and reduces the abrasion and the breaking 

 of the glass filaments. Lubricating size for weaving is chemically non -compatible with the 

 glass and resin and is detrimental to the bond between them. Therefore fiberglass cloth 

 intended for high dry and wet strength laminates must be heat-treated or chemically washed 

 to remove this size, and a chemically compatible finish be applied. 



Silane sizes and finishes on fiberglass reinforcements are recommended in preference 

 to chrome types for boat manufacture since greater laminate wet strength is obtained. 

 Widely used silane finishes are Garan and A172. 



The sizes, finishes and binders discussed are for use with polyester resins only. For 

 epoxy resins, sizes and finishes should contain an aminosilane type similar to OCF-801 

 size and an A-1100 finish. 



Several different binders are in common use (1). Highly soluble polyester resin binders 

 are used on mat intended for boat construction by hand lay up. 



RESINS 



The resins most commonly used in the molding of fiberglass boats are thermosetting 

 types. Thermosetting resins cannot be remolded once cured to the solid state. Thermo- 

 setting resins include polyesters, epoxies, phenolic s and melamine. 



With few exceptions, fiberglass boats are presently being made with polyester resins 

 because of their cost advantage and versatility. Epoxy resins are being used in some boat 

 hulls and will probably increase in usage (11). 



Due to a wide variation in types of resins available, manufacturers maintain Research 

 and Technical Service Departments for the assistance of fabricators of reinforced plastics. 

 A large amount of technical data on resins is available from these sources. To obtain the 

 highest quality laminates, manufacturer's recommendations for quantities and handling of 

 resins, catalysts, accelerators and inhibitors should be followed. Deviation from the pre- 

 scribed recommendations should only be made on the basis of extensive shop experience with 

 the particular materials employed. 



