Prepregs applications

A modified structural phenolic for prepreg application. Meets MIL-R-9299, Type A. 

A 127 - 149 C cure, modified phenolic resin for prepreg application for press cured parts for aircraft interior sandwich panels. 

A polyester for prepreg application offering good structural integrity, excellent electrical characteristics and optical clarity. Meets MIL-R-7575, Grade A B, Class 2. 

A Silicone resin for prepreg application with good electrical and high temperature characteristics in the manufacture of structural parts. Cure temperature 175"C with a step post cure and a service temperature potential of 260 C. Meets MIL-P-25518. 

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Mat and continuous glass fibre reinforcements theoretically all the thermoplastics are usable in these forms, but up to now developments have concentrated on polypropylenes (PP), polyamides (PA) and thermoplastic polyesters (PET) fibre-reinforced PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. 

The function of the resin matrix material in filament-wound structures is to help distribute the load, maintain proper fiber position, control composite mechanical and chemical properties, and provide interlaminar shear strength. Either a thermosetting or a thermoplastic resin material may be selected. Thermosetting resins may be selected for application in a wetwinding process or as part of a prepreg resin system. 

The chapter is divided into a section on development of process cycles or plans and a section on in-process control. The tools to be discussed include design of experiments, expert systems, models, neural networks, and a variety of combinations of these techniques. The processes to be discussed include injection molding, resin transfer molding, autoclave curing, and prepreg manufacturing. The relative cost and difficulty of developing tools for these applications will be discussed where data is available. 

The reaction product of BMI-MDA and MDA, known as Kerimide 601, is prepolymerized to such an extent that the resulting prepolymer is soluble in aprotic solvents such as NMP, DMF, and the like, and therefore can be prepregged via solution techniques. Kerimide 601 is mainly used in glass fabric laminates for electrical applications and became the industry standard for polyimide-based printed circuit boards (45). 

Blends have also been prepared by dissolving DMPPO in a monomer and then polymerizing the monomer. An example is an epoxy—DMPPO blend prepared by curing a solution of DMPPO in Epon 828 at 85°C with an aluminum—tetramethylguanidine catalyst. Some copolymer formation is observed. The solutions can be applied to glass cloth before curing to produce prepregs for composites in applications such as printed circuit boards (67). 

The product is processed to a condition where it is either tack-free or slightly tacky to aid in application to vertical or contoured substrates. These films may be in the form of unsupported sheet, or they may be reinforced with glass fabric, paper, or another reinforcing medium. These supported films are sometimes referred to as prepreg. 

A plot of Eq. (32) for two relative humidities (50 and 100%) yields a void stability map which is shown in Fig. 10. It is evident from this map that vacuum can be applied without encouraging void growth if such application is coordinated with the temperature of the system. Brown and McKague 14) have experimentally observed that the void content is reduced significantly when pressure is applied to the prepreg early in the cycle, which is in accordance with the stability map. 

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