Polymers and Polymer Composites

The versatility of polymers, polymeric fibers, and polymer composites is creating a growing worldwide demand for these materials in a wide variety of applications.

For more than 40 years, Southwest Research Institute (SwRI) has helped chemical and polymer producers, material suppliers, manufacturers, government agencies, and industry research groups solve problems in polymer materials, manufacturing, and design. SwRI scientists and engineers have incorporated polymers into military and aerospace applications, biodegradable products, bioreactive capsules, and biocompatible prosthetic materials.

The Institute offers integrated solutions to problems in polymer and polymer composites, with programs ranging from performing basic molecular research to developing prototype structures. The thrust of the SwRI polymer research program is conducted in its Chemistry and Chemical Engineering Division and its Mechanical Engineering Division, augmented by multidisciplinary specialists -- such as physicists and electrical, civil, petroleum, aerospace, and automotive engineers -- from other Institute divisions.

The Institute's broad range of polymer and polymer-related capabilities include:

Polymeric materials modeling
Surface and interfacial analysis
Intelligent materials processing
High-performance thermoset composite development
Polymeric biomaterials
Specialty polymer development
Polymer and composite processing, fabricating, and testing
Additional Polymer-related Services

Polymeric Materials Modeling

Using molecular dynamics computer simulation, Institute scientists illustrate the structure of a composite material. The heteronuclear polysulfone molecule is shown confined between two graphite surfaces.

Using computational modeling of materials at the molecular level, SwRI staff members develop crucial insight into the relationship between the molecular structure of a material and its end-use physical properties. The advanced software used at the Institute solves a wide spectrum of problems, including those related to:

• Molecular dynamics and Monte Carlo simulations of polymers and interfaces. Molecular modeling permits new material properties to be predicted before being produced in the laboratory, saving production costs.
  
  
• Chemical kinetics and transport properties. SwRI-developed computer models allow the prediction of molecular weight distribution, degree of cure, and relative viscosity of reactive polymer mixtures, including curing epoxies and polyimides.
  
  
• Moisture and fluid diffusion. Institute-developed computer models predict the diffusion of moisture into plastics and composites.

Surface and Interfacial Analysis

The surface and interfacial properties of polymers and polymer composites depend on the nature of the surface of the material. SwRI addresses a wide spectrum of issues in the determination of surface and sublayer properties. Institute staff members provide concrete solutions in areas such as corrosion studies, interfacial analysis, joining and bondline analysis, adhesives, thin films, polymers, thermal barrier coatings, and oxidation studies. SwRI capabilities include:

• Scanning tunneling and atomic force microscopy
• Near-infrared Raman spectroscopy
• State-of-the-art Raman imaging spectroscopy with spectral resolution of 0.2 cm-1, confocal microscopy, and direct two-dimensional Raman imaging (spatial resolution of one micrometer), enabling precise, spatially resolved chemical analysis of the surface and near-surface regions
• Electrochemical impedance spectroscopy
• Lifetime prediction of polymers and polymer surface adhesion to address the coupled chemical and mechanical problems incurred by service life within a chemical environment
• Fourier transform infrared spectroscopy by diffuse reflectance, specular reflectance, transmission, and attenuated total internal reflectance modes, with microscope attachment permitting analysis of microscopic materials

Intelligent Materials Processing

Using fiber optic sensors, kinetic and transport models, and process-control software, SwRI engineers and scientists developed the knowledge-based system to control and adjust autoclave operating parameters. The innovative technology has been extended to fiber-reinforced advanced polymeric composites.

Recognized leaders in the emerging technology of intelligent materials processing (IMP), SwRI staff members integrate advanced sensor technologies, sophisticated computational control algorithms based on artificial intelligence, and materials modeling to produce smart processing machines that control the manufacturing process by:

• Conducting physical and chemical analyses of the material being processed
• Comparing results of analyses with theoretical predictions
• Making decisions based on information received to adjust necessary process variables
• Implementing adjustments to required equipment control settings

Using IMP technology, the smart machines quickly process material with optimal cure rates to obtain the desired material properties. SwRI has established an international reputation in IMP, working in areas such as:

• Advanced composites for aerospace application, with emphasis in polymers and polymer composites
• State-of-the-art autoclave, press molding, and MechanoclaveŞ technology, successfully completing projects for major industrial consortia, aerospace manufacturers, and the electronics industry
• Advanced fiber-coating technologies, including chemical vapor deposition
• Pulsed laser deposition of thin films of yttrium barium copper oxide, producing films with high-temperature superconductivity

High-Performance Thermoset Composite Applications

Using high-service temperature thermoset resins and carbon or glass fibers, Institute staff members fabricate experimental components for stationary engine tests and other applications.

SwRI-developed low-flammability formulations are used in fabricating high-strength and lightweight honeycombs and foams for aircraft, marine, and automotive applications. (Photo courtesy of PEAR Development Corp.)

SwRI possesses experience, equipment, and processing technologies to fabricate a wide range of thermoset resin composites, using commercial and newly developed resins. Recent Institute composite efforts have focused on innovative, readily processible thermoset formulations for high-temperature, high service-load applications.

SwRI's newest formulations are adaptable for cost-effective processing by:

• Vacuum-assisted resin transfer molding
• Filament winding
• Pultrusion techniques
• Injection molding
• Autoclave curing

Polymeric Biomaterials

A scanning electron micrograph shows SwRI-developed biodegradable microspheres used for sustained or targeted release of injected therapies.

With expertise in designing polymer shell materials for microcapsules, developing dental polymers, and modifying polymer surfaces, SwRI has earned international recognition in biomaterial development. Using the Institute's state-of-the-art facilities, experienced staff members offer integrated solutions to biomaterial-related problems, including:

Microencapsulation Design

• Cell entrapment and cell immobilization
• Controlled release of injectable and implantable drugs
• Biocompatibility evaluation
• Biodegradable and biocompatible polymer evaluation for implantation
• Preclinical trial facilities meeting Good Laboratory Practices and Good Manufacturing Procedures criteria

Dental Polymer and Composite Development

• SwRI proprietary hydrophilic acrylic monomers containing amino acid half esters
• Inorganic-organic hybrid nanocomposites with low shrinkage and superior mechanical properties as dental restorative materials

Polymer Surface Modification

• Chemical surface treatments
• Ion implantation
• Ion beam-assisted coatings
• Diamond-like carbon coatings

Specialty Polymer Development

SwRI technicians measure the film thickness of a newly applied aerospace primer to ensure compliance with military specifications and industry procedures. The Air Force CTIO facilities and SwRI laboratories are well equipped to develop, characterize, and assess processes, equipment, techniques, and materials with system performance and environmental impacts.

SwRI staff members continuously assist clients with technical aspects of commercializing specialty materials, such as controlled-release biocidal films and nanoparticle-polymer composites, both invented by SwRI. The Institute is committed to helping clients understand market needs and adapting or developing technology that addresses factors such as improved performance, cost, intellectual property, scale-up requirements, and environmental or regulatory concerns. SwRI-developed applications include:

• Protective packaging composed of controlled-release biocidal films
• Nanoparticle-polymer composites for medical applications, including dental restoratives and sun screens
• Films having special electro-optical and sensing properties
• Glass coatings for specialized surface properties
• Nonhalogenated, nonemissive fire-retardant technologies for plastics, including low-density polyolefins

SwRI serves as primary technical contractor for the U.S. Air Force Coating Technology Integration Office (CTIO). The Institute uses a multidisciplinary, integrated approach to improve external aircraft coatings by optimizing the materials, processes, and equipment and incorporating state-of-the-art technology. SwRI technical contributions to coating technology include:

• Materials chemistry and polymerization studies
• Analytical techniques and instrumentation
• Corrosion control and assessment
• Environmental regulations and pollution prevention
• Robotics, automation, and equipment design/specification
• Composites structural assessments

Polymer and Composite Processing and Testing

To support the development of new advanced aerospace and industrial thermoset resin composites, the Institute uses a highly versatile hot melt (or solvent) prepreg machine that produces thermoset precursors-coated unidirectional tows of carbon, glass, KevlarTM, or other fibers. Accessories allow 20-cm wide cloth prepregs to be produced.

The Institute has extensive experience in compression and autoclave curing, extrusion, polymer blending, and vacuum-assisted resin transfer molding. SwRI-developed polyether amide thermoset resin formulation technology allows filament winding, pultrusion, and resin film infusion. State-of-the-art laboratory facilities are equipped with a wide variety of instrumentation to synthesize, analyze, and test polymers and polymeric products. Experienced SwRI staff members provide the following services:

Polymer Processing

• High-strength, heat-resistant thermoset resin composites fabrication
• Thermoplastic extrusions (to 425 degrees Celsius)
• Thermoplastics and blends reinforced with high- strength short fibers and small particulate fillers
• Adhesive formulations vacuum mixing
• Elastomer formulations mixing and curing kinetics
• Epoxy repair adhesives not requiring refrigerated storage

Materials Analysis

• Chromatography, including high-performance liquid, gas, and high-temperature gel permeation
• Spectroscopy, including nuclear magnetic resonance, X-ray diffraction and energy-dispersive analysis, ultraviolet-visible, infrared and Raman, surface (Auger and X-ray photoelectron), atomic absorption, and inductively coupled plasma
• Electron microscopy, including transmission, scanning, and scanning transmission
• Thermal, including differential scanning calorimetry and thermal gravimetric analysis

Polymer Rheological Testing

• Time and frequency
• Strain
• Curing kinetics
• Viscosity and flow
• Deformation and stress relaxation
• Extended-time predictions

Additional Polymer-related Services

Using a cone calorimeter, the flammability of linear low-density polyethylene is compared to that of an Institute-developed nonhalogenated, fire-retardant formulation. The incident heat flux in each case is 20 kW/m2.

The diverse capabilities of the Institute allow its engineers and scientists to provide comprehensive and cost-effective evaluation, analysis, and testing services to the polymer industry. Specific capabilities include:

Flammability Evaluation

• Laboratory and full-scale standard and custom flammability tests for most polymeric materials used in aircraft, ship, rail, and rapid transit applications
• Performance evaluation of full-size polymer-containing assemblies, including cars, buses, railcars, and building modules
• Assessment of composite's remaining strength after undergoing fire testing
• Computer-modeled fire scenario evaluation

Failure Analysis

• Fiber-reinforced composite structures
• Polyethylene gas distribution pipes
• Acrylic windshields

Nondestructive Evaluation

• Nondestructive methods such as shearography, radiography, computer-assisted tomography, pulsed infrared thermography, liquid-coupled and dry-coupled ultrasonics
• SwRI-developed methods to detect delamination, lack of adhesion, excess adhesive, matrix cracking, impact damage, and fiber damage in composites
• Institute-developed method to inspect polyethylene pipe fusion joints

Composites Mechanical and Environmental Testing

• Mechanical tests include creep, torsion and shear, shock and vibration, high-speed impact, compression and tensile strength
• Standard environmental tests include thermal, ultraviolet, humidity, altitude, acoustic, rain or fog, salt, and sand or dust

This brochure was published in May 1997. For more information, contact the appropriate Institute staff member.

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