Search Results for Molding resins

Resin transfer molding (RTM) and structural reaction injection molding (SRIM) are two similar processes that are well suited to the manufacture of large, complex, and high-performance structures. This article discusses the similarities and differences of RTM and SRIM processes and the unique design considerations with respect to the physical properties, geometry, surface quality, process economics, equipment, and tooling of a component that should be considered in choosing RTM or SRIM over other competing processes for fabricating reinforced components.

Resin transfer molding and structural reaction injection molding belong to a family, sometimes denoted as liquid composite molding. This article provides information on the characteristics and automotive and aerospace applications of liquid composite molding. It reviews techniques that use hard tooling and positive (superatmospheric) pressures to produce structures. The techniques include vacuum-assisted resin injection, vacuum infusion, resin-film infusion, and injection-compression molding. The article provides an overview of the materials that are commonly used together with some of processing characteristics that are important to processing speed and part quality. It concludes with a discussion on design guidelines for the liquid composite molding.

This article discusses classification of foundry processes based on the molding medium, such as sand molds, ceramic molds, and metallic molds. Sand molds can be briefly classified into two types: bonded sand molds, and unbonded sand molds. Bonded sand molds include green sand molds, dry sand molds, resin-bonded sand molds, and sodium silicate bonded sand. The article describes the casting processes that use these molds, including the no-bake process, cold box process, hot box process, the CO2 process, lost foam casting process and vacuum molding process. The casting processes that use ceramic molds include investment casting, and plaster casting. Metallic molds are used in permanent mold casting, die casting, semisolid casting, and centrifugal casting.

The goal of design is to improve the overall performance of the metal or ceramic matrix rather than to create a material with different response than the base matrix. This article focuses on the design for manufacturing polymeric composites. Specially developed methods including contact molding, compression-type molding, resin-injection molding, and pultrusion are described. The article also discusses the various factors to be considered in designing for composite manufacturing.

Differential scanning calorimetry (DSC) is the most common thermal technique for polymer characterization. This article provides a detailed account of the various factors and processes involved in DSC. The discussion covers the equipment used, specimen preparation process, calibration requirements, data analysis, and provides examples of the applications and interpretation of DSC.

This article reviews analytical techniques that are most often used in plastic component failure analysis. The description of the techniques is intended to familiarize the reader with the general principles and benefits of the methodologies, namely Fourier transform infrared spectroscopy, energy-dispersive x-ray spectroscopy, differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The article describes the methods for molecular weight assessment and mechanical testing to evaluate plastics and polymers. The descriptions of the analytical techniques are supplemented by a series of case studies to illustrate the significance of each method. The case studies also include pertinent visual examination results and the corresponding images that aided in the characterization of the failures.

This article reviews the analytical techniques most commonly used in plastic component failure analysis. These include the Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis, thermomechanical analysis, and dynamic mechanical analysis. The descriptions of the analytical techniques are supplemented by a series of case studies that include pertinent visual examination results and the corresponding images that aid in the characterization of the failures. The article describes the methods used for determining the molecular weight of a plastic resin. It explains the use of mechanical testing in failure analysis and also describes the considerations in the selection and use of test methods.

Mounting of the specimen is often desirable or necessary for handling and metallographic polishing after the specimen is cut into an appropriate size. This article illustrates the different mechanical clamps used in mounting small specimens. It provides useful information on compression molded mounts, which are molded with thermoplastic and thermosetting resins. The article reviews several resins and their key factors, which help in the selection of the most appropriate mounting method and resin. It also discusses the characteristics of plastic mounting materials. The article provides information on the molds and resins used for castable mounts, vacuum treatment of mounts, special mount arrangements, and mount marking and storage.

Shell molding is used for making production quantities of castings that range in weight from a few ounces to approximately 180 kg (400 lb), in both ferrous and nonferrous metals. This article lists the limitations or disadvantages of shell mold casting. It describes the two methods for preparation of resin-sand mixture for shell molding, namely, mixing resin and sand according to conventional dry mixing techniques, and coating the sand with resin. Shaping of shell molds and cores from resin sand mixtures is accomplished in machines. The article discusses the major steps in producing a mold or core and describes the problems most frequently encountered in shell-mold casting. The problems include mold cracking, soft molds, low hot tensile strength of molds, peelback, and mold shift. The article concludes with information on examples that provide some relative cost comparisons between shell molding and green sand molding.

Rotational molding is a simple but unique process that has the capability of producing small to large hollow items with very uniform wall thicknesses. Providing an overview of the operating principles of rotational molding, this article discusses the key selection factors, including function and property requirements for resins and additives; size, shape, design, and cost of molded parts; equipment type and size; and the type of mold to be used. Commonly used molds include cast aluminum, fabricated sheet metal, nickel deposit, machined aluminum, silicone, fiberglass, and prototype molds.

This article presents the basic guidelines considered in designing a composite structure, and the basic definitions of terms that apply to composites. It describes the analysis of a composite laminate based on stress-strain relationships, stress-strain load relationships, general load displacement case, and general load case solution. Factors affecting the composite materials properties and allowables of fiber-reinforced polymers are reviewed. The article discusses the process considerations for mold design, such as master model, metal tooling, composite tooling, and tool care. It explains the resin selection in designing the composite for use in a particular application. The article illustrates the various methods that are used to process a composite component, namely, wet lay-up, autoclave, resin transfer molding, and vacuum-assisted resin transfer molding. It provides a discussion on electromagnetic interference shielding, electrostatic discharge protection, metal plating, fire resistance, and corrosion resistance on composite materials.

This article illustrates the polymer matrices used for composite materials. It describes the use of prepeg materials in manufacturing high-performance composites. The article discusses the various infusion processes for the development of fiber-reinforced composites, namely, resin transfer molding, vacuum-assisted resin transfer molding, and resin film infusion. It explains the composite- and matrix-toughening methods for fiber-reinforced composites, such as dispersed-phase toughening and interlayer toughening. The article concludes with information on optical microscopy, which provides an insight into the micro- and macrostructure of fiber-reinforced composites.

Thermogravimetric analysis (TGA) is a thermal analysis technique that measures the amount and rate of change in the weight of a material as a function of temperature or time in a controlled atmosphere. This article provides a detailed account of the concepts of TGA, covering the various criteria to be considered for specimen preparation and calibration of TGAs. The use of thermogravimetric analysis data in the assessment of failure analysis of plastics and the combined usage of TGA with other techniques to understand the changes in the sample are also covered. The article provides examples of applications and provides information on the interpretation of TGA.