How Moisture Absorption Relates to the Stability of a Machined Polymer

April 13, 2021

Most polymers have a natural tendency to absorb water. In fact, some superabsorbent polymers are highly sought after in advanced applications for medical, construction and more. Yet, moisture absorption of thermoplastics leads to changes with regard to processing and properties.

It is crucial for machinists and designers to understand the moisture absorption of thermoplastics for CNC machining. During the design phase, this not only helps with initial material selection, but plays a role in predicting the life span of a part. At AIP, we take great care in providing unrivaled results to ensure the optimal dimensions and properties for machined polymers and composites. Join us in this technical brief as we give an in-depth explanation of the effects of moisture absorption for machined polymers.

Plastics Machining and the Importance of Water Absorption

Moisture / water absorption is the capacity of a plastic or a polymer to absorb moisture from its environment. Absorbed moisture sometimes acts as a plasticizer, reducing the glass transition temperature and strength of plastic (this is a reversible side effect). However, absorbed water also can lead to irreversible degradation of the polymer structure.

Some effects include:

Dimensional and mass changes (swelling) caused by water absorption
Extraction of water-soluble components
Changes in mechanical (elasticity, tensile strength, impact strength) and electrical performance

Water absorption is expressed as increase in weight percent or % weight gain of a plastic specimen under the following testing procedures:

Water Absorption 24 hrs at 23°C – Immersion of a plastic specimen in distilled water during 24 hours at 23°C
Water Absorption 24 hrs at 100°C– Immersion of a plastic specimen in distilled boiling water during 24 hours Water Absorption at saturation – Immersion of a plastic specimen in distilled water at 23°C. Measurement occurs when the polymer does not absorb water anymore
Water Absorption at Equilibrium– Plastic specimen is exposed to a humid environment — generally at 50% relative humidity — at a specified temperature — 23°C or 73.4°F — for 24 hours

(Source: Omnexus)

Exposure to humidity, immersion and boiling water can result in different material responses. The equilibrium moisture content can be used to compare the amount of water absorbed by different types of plastics when they are exposed to moisture.

Plastics Processing and Properties

Polymers are affected by moisture from their environment or from simply sitting on a shelf waiting to be used. This is not a huge concern, but when the moisture absorption reaches more than 1% or 2%+, this can result in enough dimensional movement to create concerns.

Moisture Absorption Affects:

Mechanical properties
Wear properties
Dimensions

For example, parts made from TORLON (PAI) require special attention due to a 1.7% moisture at saturation value. While this number may not sound like much, it is enough to cause a precision machined TORLON part to exceed tolerance; in this scenario, the part cannot be used.

Therefore, it is important to properly package these mission critical polymers for lasting shelf-life and function. This can be achieved in two ways: 1) Vacuum-sealing them in a moisture-impermeable layer or 2) packaging them with bags of desiccant. This prevents moisture uptake in humid environments.

Tests to Measure Water Absorption of Plastics

Source

ASTM D570 – Standard Test Method for Water Absorption of Plastics

This test method for rate of water absorption has two main functions:

A guide to the proportion of water absorbed by a material and consequently, in those cases where the relationships between moisture and electrical or mechanical properties, dimensions, or appearance have been determined, as a guide to the effects of exposure to water or humid conditions on such properties.
A control test on the uniformity of a product. It is particularly applicable to sheet, rod, and tube arms when the test is made on the finished product.

Procedure: Parts are dried in an oven for a specified time and temperature and then placed in a desiccator to cool. Upon cooling, the specimens are weighed to establish a point of reference. The material is then submerged in water at standardized conditions (usually 23°C for 24 hours or until equilibrium). Specimens are removed from the liquid, dried and weighed.

What affects water absorption?

Type of plastic
Morphology (crystalline, amorphous…)
Type and proportion of additives, fillers and reinforcements used
Fiber fraction and orientation (in composites)
Relative humidity and temperature
Length of exposure

Water Absorption Values for Common Polymers

Polymer Name	Min Value (% weight)	Max Value (% weight)
ABS – Acrylonitrile butadiene styrene	0.05	1.80
PA – Nylon Polyamide, 66 30% Glass Fiber	0.80	1.10
PAI – Polyamide-Imides (TORLON)	0.10	0.30
PBI – Polybenzimidazole (CELAZOLE)	0.4	5
PC – Polycarbonate, high heat	0.10	0.20
PE – Polyethylene, 30% glass fiber	0.02	0.06
PEEK – Polyetheretherketone	0.10	0.50
PEI – Polyetherimide (ULTEM)	0.20	0.30
PP – Polypropylene	0.01	0.10
PS – Polystyrene, high heat	0.01	0.07
PSU – Polysulfone	0.20	0.80
PTFE – Polytetrafluorethylene	0.005	0.015
PVC – Polyvinyl chloride, rigid	0.04	0.40
PVDF – Polyvinylidene fluoride (KYNAR)	0.03	0.05

As the chart notes, some polymers such as Nylon (PA) have a higher rate of % gain from moisture absorption. However, polymers like PVDF and PTFE have a very low % gain in weight after the ASTM D570 test – which makes them excellent candidates for applications where moisture is a factor.

Performance thermoplastics are often exposed to high temperature applications (aircraft engines) which also absorb high levels of moisture. This is common in materials such as PBI (Celazole) and PAI (Torlon), since these polymers absorb moisture at high rates but are also specified in high temperature applications.

Basically, what can happen is that these materials absorb the moisture if not properly stored and packaged. Then if subject to high levels of heat without time for the moisture to dissipate, the internal moisture boils and turns to steam causing the parts to crack and blister.

Managing Moisture Absorption

For predictable machined part fit and performance, stock shapes and finished parts should be stored in a dry environment. Both finished parts and stock shapes should be packed in moisture barrier packaging. Only open packaging just prior to use. In the event that a part may have adsorbed so much moisture as to risk shocking it when placing it in high temperature or vacuum service, consider drying the material prior to use or re-use.

Your machining facility will have specifications on temperature and storage procedures for all polymers, stock shapes and components. When it comes to critical applications, work with a machine shop that has high standards for storing products. After all, machining a polymer is only part of the entire process; wasted machining, revenue and parts is not worth risking poor storage conditions. The table below shows some common packaging for polymers to increase and preserve shelf-life.

Generally, you can find a polymer’s 24 Hour and Saturation Moisture Absorption Values on a data chart. A chart can give a general idea of the moisture absorption, but an entire data set with the curve of a material is the best way to determine the right material for your project. Be sure to work with a plastics machining company that can provide you a wide range of data on the moisture absorption of polymers and composites. Your machinist will be able to identify how moisture and humidity will affect your project’s design and functionality. Talk to one our engineers at AIP about your project design, and we will work with you to provide unrivaled expertise from your project’s initial concept to completion.

Supporting Materials

Certifications and Regulatory Resources

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Common Thermoplastic Materials in Aerospace & Defense

January 27, 2020

With over three decades of experience machining precision plastic and composite parts for the Aerospace & Defense industry, AIP Precision Machining knows that weight and strength are critical for your flight-ready hardware. That’s why we’ve carefully selected, machined, and tested all our thermoplastic materials to various aerospace industry standards. Our lightweight polymers and composites have stable chemical and corrosion resistance, as well as improved strength to weight ratios when compared to exotic alloys and non-ferrous metals. AIP’s polymer and composite materials maintain their properties even at high temperatures.

Read more on thermoplastic materials commonly used in the Aerospace & Defense industry for every day to mission-critical applications.

ULTEM – PEI

ULTEM has one of the highest dielectric strengths of any thermoplastic material, meaning it works very efficiently as an electrical insulator. Being resistant to both hot water and steam, ULTEM can withstand repeated cycles in a steam autoclave and can operate in high service temperature environments (340F or 170C). ULTEM also has one of the lowest rates of thermal conductivity, allowing parts machined from ULTEM to act as thermal insulators. ULTEM is FDA and NSF approved for both food and medical contact and therefore is an excellent choice for aircraft galley equipment such as ovens, microwaves and hot or cold beverage dispensing systems. UL94 V-O flame rating with very low smoke output makes this material ideal for aircraft interior components.

CELAZOLE – PBI

CELAZOLE provides the highest mechanical properties of any thermoplastic above 400F (204C) and offers a continuous use operating temperature of 750F (399C). CELAZOLE has outstanding high-temperature mechanical properties for use in aircraft engines and other HOT section areas. This impressive lightweight material retains 100% tensile strength after being submerged in hydraulic fluid at 200°F for thirty days.

RYTON – PPS

RYTON’s inherent fire retardancy, thermal stability and corrosion resistance makes it perfectly suited for aerospace applications, while its dimensional stability means even the most intricate parts can be molded from RYTON with very tight tolerances. RYTON is typically used for injection molded parts, however, there is limited availability of extruded rod and plate for machining.

VESPEL or DURATRON – PI

Like RYTON, VESPEL is dimensionally stable and has fantastic temperature resistance. It can operate uninterrupted from cryogenic temperatures to 550°F, with intermittent to 900°F. Thanks to its resistance to high wear and friction, VESPEL performs with excellence and longevity in severe environments—like those used in aerospace applications. VESPEL is a trademarked material of DuPont and can be provided in direct formed blanks or finished parts directly from DuPont. AIP provides precision machined components from DuPont manufactured rod and plate stock. VESPEL is typically used in high temperature and high-speed bearing and wear applications such as stator bushings.

TORLON or DURATRON – PAI

DURATRON PAI’s extremely low coefficient of linear thermal expansion and high creep resistance deliver excellent dimensional stability over its entire service range. DURATRON PAI is an amorphous material with a Tg (glass transition temperature) of 537°F (280°C). DURATRON PAI stock shapes are post-cured using procedures developed jointly by BP Amoco under the TORLON trade name and Quadrant under the DURATRON trade name. A post-curing cycle is sometimes recommended for components fabricated from extruded shapes where optimization of chemical resistance and/or wear performance is required. TOLRON parts are used in structural, wear and electrical aerospace applications.

TECHTRON – PPS

TECHTRON has essentially zero moisture absorption which allows products manufactured from this material to maintain extreme dimensional and density stability. TECHTRON is highly chemical resistant allowing it to operate while submerged in harsh chemicals. It is inherently flame retardant and can be easily machined to close tolerances. It has a broader resistance to chemicals than most high-performing plastics and can work well as an alternative to PEEK at lower temperatures.

RADEL – PPSU

With high heat and high impact performance, RADEL delivers better impact resistance and chemical resistance than other sulfone based polymers, such as PSU and PEI. Its toughness and long-term hydrolytic stability means it performs well even under autoclave pressure. RADEL R5500 meets the stringent aircraft flammability requirements of 14CFR Part 25, allowing the aircraft design engineer to provide lightweight, safe and aesthetically pleasing precision components for various aircraft interior layouts. RADEL can be polished to a mirror finish and is FDA and NSF approved for food and beverage contact.

KEL – F

Kel-F is a winning combination of physical and mechanical properties, non-flammability, chemical resistance, near-zero moisture absorption and of course outstanding electrical properties. This stands out from other thermoplastic fluoropolymers, as only Kel-F has these characteristics in a useful temperature range of -400°F to +400°F. In addition, it has very low outgassing and offers extreme transmissivity for radar and microwave applications. Many aircraft and ground-based random applications use Kel-F.

PEEK

PEEK can be used continuously to 480°F (250°C) and in hot water or steam without permanent loss in physical properties. For hostile environments, PEEK is a high strength alternative to fluoropolymers. PEEK carries a V-O flammability rating and exhibits very low smoke and toxic gas emission when exposed to flame. PEEK is an increasingly popular replacement for metal in the aerospace industry due to its lightweight nature, mechanical strength, creep and fatigue resistance, as well as its ease in processing. Its exceptional physical and thermal characteristics make it a versatile thermoplastic polymer in many aerospace applications. AIP has provided flight control, fuel system, interior, engine and aerodynamic related PEEK components for various aircraft OEM and MRO providers worldwide.

KYNAR – PVDF

Another example of thermoplastic materials used in aerospace and defense is KYNAR, or PVDF. This polymer has impressive chemical resistance at ambient and elevated temperatures, as well as good thermomechanical and tensile strength. KYNAR is extremely durable due to its weather-ability and toughness even in the most severe environments. In addition to being flame-resistant, KYNAR is easy to machine, too. You can typically find KYNAR components in pipe fitting and various fuel or other fluid-related precision manifolds or connectors.

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What Can This Polymer Do? ULTEM

January 21, 2020

PART SUMMARY:

One of the high-performance thermoplastics that AIP machines is Polyetherimide (PEI), known by its tradename ULTEM. Due to its weight-saving properties, high chemical and hydrolysis resistance and tensile strength, ULTEM is popular across several industries: Automotive, aerospace and defense, electrical and electronic market, medical and life sciences and industrial applications and appliances. Read on to learn about what this incredible polymer can do!

MATERIAL PROPERTIES:

Polyetherimide (PEI) is an amorphous thermoplastic. Polyetherimide was developed to provide sufficient flexibility and good melt processability while maintaining excellent mechanical and thermal properties.

Key properties of ULTEM PEI include:

Handling at temperatures up to 340°F (171°C)
Heat Resistance
Flame Resistance
Chemical Resistance
High Rigidity
Highest Dielectric Strength
Hydrolysis Resistance
Low Thermal Conductivity

ULTEM Applications

As mentioned previously, ULTEM is a highly sought-after thermoplastic for weight-saving capabilities in aerospace components to reusable autoclave sterilizations in medical applications. However, it’s most commonly used in high voltage electrical insulation applications.

Common uses include:

Analytical Instrumentation
Dielectric Properties Required
Electrical Insulators
High Strength Situations
Reusable Medical Devices
Semiconductor Process Components
Structural Components
Underwater Connector Bodies

So, what can this polymer do? Let’s take a closer look at how ULTEM (PEI) is applied in the Aerospace & Defense, Medical & Life Sciences and Specialized Industrial markets:

WHAT CAN ULTEM DO FOR AEROSPACE & DEFENSE?

In the Aerospace & Defense Industry, ULTEM is often applied to aircraft components for weight reduction in place of metal parts. Additionally, since it has a high thermal resistance rating, polymer components have the benefit of evading radar detection in military aircraft.

AIP machines ULTEM 1000 & ULTEM 2300

ULTEM 2300 is a 30 percent glass filled version of virgin ULTEM 1000. The addition of glass increases ULTEM 1000’s dimensional stability by almost three times.

For over three decades, AIP has provided flight control, fuel system, interior, engine and aerodynamic-related ULTEM components for various aircraft OEM and MRO providers worldwide. As this industry continues to expand, evolve and innovate, the demand for high-performance materials like ULTEM contribute significantly to streamlined operations.

WHAT CAN ULTEM DO FOR MEDICAL & LIFE SCIENCES?

In the Medical Industry, biocompatibility and sterilization are paramount to medical instruments and implants. ULTEM is often a popular choice in this sector due to its resistance to chemicals and lipids. Polyetherimide also withstands dry heat sterilization at 356°F (180°C), ethylene oxide gas, gamma radiation and steam autoclave.

Some popular medical applications include disposable and re-usable medical devices and medical monitor probe housings. These could be surgical instrument handles and enclosures or non-implant prostheses. It gets extensive use in membrane applications due to its separation, permeance and biocompatible properties.

WHAT CAN ULTEM DO FOR SPECIALIZED INDUSTRIAL Sectors?

At AIP, we precision machine ULTEM for many specialized industrial applications as well: automotive, electrical and metal replacement, to name a few. Despite the diversity of these industrial applications, we have the inventory and machining capabilities to provide solutions for any project specifications.

PEI is most often used in electrical and lighting systems in the automotive market for its high heat resistance, mechanical integrity and strength. Principal automotive applications include: transmission parts, throttle bodies, ignition components, thermostat housings, bezels, reflectors, lamp sockets and electromechanical systems.

The electrical and electronic markets demand high heat resistant materials. ULTEM is an excellent choice for applications such as electrical circuit boards, switches, connectors, electronic chips and capacitors.

As discussed previously, thermoplastics like ULTEM often replace metal parts in industrial applications. For this reason, it’s often used in housewares, especially fluid handling systems. Some of these applications are: HVAC equipment, microwave cookware, steam and curling irons, dual-ovenable trays for food packaging that meets FDA food packaging requirements.

What can AIP Precision Machining do for you?

From concept to completion, our team of engineers will work with you to realize the final product. With some of the fastest lead times in the industry, our unrivaled technical experts we can tackle your polymer challenges.

What Can This Polymer Do? Supportive Information

Medical Sector Biomaterials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

Amorphous Materials

Aerospace Case Study: Weight-saving Polymers

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The History of Aviation Materials

July 18, 2019

Key Moments in Aircraft & Aerospace Innovation

Aviation technology has come a long way to get to where it is today. Over the course of the last century countless test flights, thousands of blueprints, and endless research from passionate minds have propelled the evolution of aircraft and aerospace technologies. Read on to discover how aviation materials have shifted to create a better, safer, and more efficient flight experience.

The Pioneers of Aviation

For much of human history, we have been fascinated with taking flight. The ancient Greeks contemplated sprouting wings in myths like Icarus and Daedalus – the boy who flew too close to the sun with wax and feather wings. Leonardo Da Vinci sketched flying machines that were way ahead of Renaissance times. It all came to fruition in 1857 when Félix du Temple de la Croix, a French Naval officer, received a patent for a flying machine. By 1874, he had developed a lightweight steam-powered monoplane which flew short distances under its own power after takeoff from a ski-jump. Finally, in 1903, the Wright Brothers made the first controlled, powered, and sustained flight near Kitty Hawk, North Carolina. The Wright Flyer featured a lightweight aluminum engine, wood and steel construction, and a fabric wing warping. According to the U.S. Smithsonian Institution, the Wright brothers accomplished the “world’s first successful flights of a powered heavier-than-air flying machine.”

Just 12 years later, the first all-metal airplane (Junkers J1), built by Hugo Junkers (1859-1935), took flight in 1915. Previously, aircraft experts believed that airplanes can only fly with light materials such as wood, struts, tension wires, and canvas. Junkers thought differently and believed that heavier materials like metal were necessary to transport passengers and goods.

The Golden Age

The Roaring 20’s ushered in airplane racing competitions, which led aircraft designers to focus on performance. Innovators, such as Howard Hughes, found that monoplanes (aircraft with one pair of wings) were more aerodynamic in comparison to biplanes, and that frames made with aluminum alloys were capable of withstanding extraordinary pressures and stresses. Due to its lightweight properties, aluminum also made its way into the internal fittings of the aircraft decreasing the weight and allowing for a more fuel-efficient design.

In 1925, Henry Ford acquired the Stout Metal Airplane Company, utilizing the all-metal design principles proposed by Hugo Junkers, Ford developed the Ford Trimotor, nicknamed the “Tin Goose.” The “Tin Goose” propelled the race to design safe and reliable engines for airline travel. A few years later, Henry Ford’s Trimotor NC8407 became the first airplane flown by Eastern Air Transport, a leading domestic airline in the 1930s flying routes from New York to Florida. This positioned metal as the primary material for domestic aircraft, and eventually military applications with the onset of WWII.

Plastic’s Mettle: Wartime Materials Take Flight

By the 1930’s, the use of wood became obsolete and all-metal aircrafts were produced for their durability. Imperial Airways, known today as British Airways, made headway in the air travel industry with advertisements of luxury and adventure to cross borders. However, those borders were sealed off with the breakout of WWII. In 1939, Imperial Airways, a private commercial airline, was ordered to operate from a military standpoint at Bristol Airport. Across the Atlantic, engineers focused their efforts on building aircraft meant specifically for military strategy – strength, durability, agility, and weaponry. The Boeing P-26 “Peashooter” entered service with the United States Army Air Corps as the first all-metal and low-wing monoplane fighter aircraft. Known for its speed and maneuverability, the small but feisty P-26 formed the core of pursuit squadrons throughout the United States.

In times of war, there are often significant advancements in material usage, weaponry, and machinery. World War II was no different. Plastics entered the scene during World War II, starting with the replacement of metal parts for rubber parts in U.S. aircraft after Japan limited metal trade with the United States. Following that, plastics of higher grades began to replace electrical insulators and mechanical components such as gears, pulleys, and fasteners. Aircraft manufacturers began to replace aluminum parts with plastics as they were lighter and thus more fuel efficient than aluminum.

The Race for Space

Lighter and more fuel efficient were the key words following World War II as nations turned their attention to the skies and beyond. The space program in the 1960’s brought together illustrious minds to solve the seemingly impossible feat of being the first country to put mankind on the moon, thus, the great race for space began. Aircraft were now going beyond the sky and NASA scientists knew they were dealing with new territory in aero innovation. They needed a material that could break the Earth’s atmosphere and carry a hefty amount of fuel, while protecting the spacecraft’s crew from extreme temperatures. NASA scientists turned to plastics, specifically Kevlar and nylon. Layers of nylon and other insulators were wrapped under the body of the spacecraft to protect the crew from the extreme temperatures of space. Both of these plastics are still staples in the aerospace industry – keeping the Hubble telescope and many other satellites scanning humanity’s charted and uncharted expanse.

Plastics of the Future

Plastics continue to lead the future of materials in aerospace and aviation industries for their durability, precision, and ingenuity. For example, in 2009, the 787-8 Dreamliner made its first maiden flight, becoming the first aircraft to have wings and fuselage made from carbon-fiber plastics. Besides being lightweight, plastics offered increased safety with their resistance to high impact, and their proven ability to withstand chemically harsh environments. This proved plastics an invaluable material when compared to alternative material choices like glass or metal.

Starting in the 1970s, plastics began to play a more crucial part in the defense and military industry, especially in stealth aircraft. The U.S. Air Force saw the potential of plastics when they learned that plastics could absorb radar waves. The added benefit of reduced radar signature makes plastics ideal for creating stealthy aircraft. Plastics continue to contribute to innovation in the defense industry, especially with stealth fabrics and other composite materials which can virtually create invisibility to radars in the near future.

Aside from plastics becoming increasingly popular for use in the defense and military sector, high grade plastics like PEEK are highly favorable for space travel due to its ability to function in hostile environments, critical in space exploration. Plastics are even being researched for lightweight radiation shielding for the International Space Station and flights to Mars.

At AIP, we’re proud to be a continued part of aviation and aerospace advancements and we look forward to engineering solutions for the next frontier. In fact, at the time this article was written, we are AS9100D:2016 certified, which means we meet the high-quality standards of applications in the aerospace industry. In addition, we are also ISO 13485:2016, ISO 9000:2015, FDA audited, and ITAR certified. Above call, we strive to create genuine relationships with our customers to deliver mission critical components with promise. To learn how we can help you, contact us today.

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Advantages of Polymer Components over Metallic Materials for Machined Parts

March 25, 2019

This post was originally published in August 2017 and updated in March 2019.

When in need of a custom-machined component for a project, choosing a metallic material may be the instinctive consideration to the design engineer. This article is intended to provide educational insight as to a more sensible alternative for precision-machined, high-strength, durable parts: machined polymers and composites. Let’s explore the benefits of opting for a plastic material versus the more traditional metal materials for precision parts.

Benefits Across the Board

Machined polymer and composite components are the most cost-effective solution when compared to metal.

Machined plastic parts are lighter and therefore provide immense advantages over metals by offering lower lifetime freight costs for equipment that is regularly transported or handled over the product’s lifetime. In bearing and wear applications, polymers provide extensive advantages over metals by allowing for lower power motors for moving parts due to lower frictional properties of polymer wear components compared to metals. The low frictional properties provide for less wear as well. The lower wear rates allow for less maintenance-related downtime. Now your equipment can be online longer producing you more profit. Not only are plastics lighter, but they’re also less expensive than many raw metal materials used for parts. Plastics are produced in faster cycles than metals which helps keep manufacturing costs down as well.

Plastics are more resistant to chemicals than their metal counterparts.

Without extensive and costly secondary finishes and coatings, metals are easily attacked by many common chemicals. Corrosion due to moisture or even dissimilar metals in close contact is also a major concern with metal components. Polymer and composite materials such as PEEK, Kynar, Teflon, and Polyethylene are impervious to some of the harshest chemicals. This allows for the manufacture and use of precision fluid handling components in the chemical and processing industries which would otherwise dissolve if manufactured from metallic materials. Some polymer materials available for machining can withstand temperatures over 700°F (370°C).

Plastic parts do not require post-treatment finishing efforts, unlike metal.

Polymer and composites are both thermally and electrically insulating. Metallic components require special secondary processing and coating in order to achieve any sort of insulating properties. These secondary processes add cost to metallic components without offering the level of insulation offered by polymer materials. Plastic and composite components are also naturally corrosion resistant and experience no galvanic effects in a dissimilar metal scenario that require sheathing. Unlike metals, plastic materials are compounded with color before machining, eliminating the need for post-treatment finishing efforts such as painting.

Let’s Break It Down by Industry

The benefits and features of plastic materials over metals discussed above span across multiple industries, showcasing the utility and versatility that plastic brings to the table.

Aerospace & Defense

Lightweight: Polymer and composite materials are up to ten times lighter than typical metals. A reduction in the weight of parts can have a huge impact on an aerospace company’s bottom line. For every pound of weight reduced on a plane, the airline can realize up to $15k per year in fuel cost reduction.

Corrosion-Resistant: Plastic materials handle far better than metals in chemically harsh environments. This increases the lifespan of the aircraft and avoids costly repairs brought about by corroding metal components an in-turn reducing MRO downtime provides for more operational time per aircraft per year.

Insulating and Radar Absorbent: Polymers are naturally radar absorbent as well as thermally and electrically insulating.

Flame & Smoke Resistances: High-performance thermoplastics meet the stringent flame and smoke resistances required for aerospace applications.

Learn More

Medical & Life Sciences

Sterility: In the medical industry, cleanliness is vital when it comes to equipment. Infection is the greatest threat facing hospital patients. Polymer and composite materials are easier to clean and sterilize than metal.

Radiolucency: Radiolucency is the quality of permitting the passage of radiant energy, such as x-rays, while still offering some resistance to it. Surgical instruments and components manufactured from polymer materials allow the surgeon a clear unobstructed view under fluoroscopy. This allows for safer, more precise surgeon outcomes in the OR. Metal instruments impede the surgeon’s view.

Lightweight: Plastic and composite surgical components allow orthopedic OEMs to meet ergonomic weight limits for surgical trays. Each metallic instrument adds weight and strain to the surgical team carrying and using metal instruments.

Reduced Stress-Shielding: Stress shielding occurs when metal implants and bone don’t become one nor work in unison. In medical-grade polymers like PEEK, however, its similar modulus to bone “fuses” with the bone into a single construct.

Learn More

Specialized Industrial

High Tensile Strength: Several lightweight thermoplastics can match the strength of metals, making them perfect for industrial equipment metal part replacement.

Chemical & Corrosion Resistances: Semiconductor equipment and electronics require survival in extreme, high-pressure environments.

Flexibility & Impact Resistance: Polymers are resistant to impact damage, making them less prone to denting or cracking the way that metals do.

Excellent Bearing & Wear Properties: Bearing-grade plastics can withstand repeated friction and wear for your high-load solutions.

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Power & Energy

Weight, corrosion, and sealing: Plastic materials allow the oil and gas industry to explore deeper depths than ever before by offering tool weight reduction without a loss of strength as well as materials which offer superior sealing attributes.

Superior Insulation: Naturally insulating plastics provide for superior thermal and electrical insulation over metals, which is a must for power generation equipment that deals with electrical currents.

Chemical, Wear & Corrosion Resistances: Plastic components with a strong chemical, wear and corrosion resistances reduce downtime and yield long-lasting performance and reliability.

Extreme Water & Earth Depth Capabilities: These qualities are necessary for high pressure and temperature applications that involve surviving extreme environments.

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As you can see, plastics have a variety of unique attributes which place them above metals in terms of utility, cost-effectiveness and flexibility for precision-machined components. Search specific plastic materials and their applications per industry with our useful material search function.

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Machining Delrin: A Plastics Guide

March 1, 2019

An Informational Brief on Polymer Machining

Delrin®, also commonly known as an acetal (polyoxymethylene) homopolymer, is an impact and wear resistant semi-crystalline thermoplastic popular for a broad range of machining applications. To list just a few of its impressive qualities, Delrin offers great stiffness, flexural modulus, and high tensile and impact strength.

Our latest machining guide discusses what goes into machining Delrin and how its considerations differ from other manufacturing options such as metal machining, injection molding, and 3D printing.

How does AIP approach Delrin and its machining process? To start, we’ll explain the difference between machining Delrin, a thermoplastic, and machining thermosets.

Machining Thermoplastics vs Thermosets

We’ve already said that Delrin is a thermoplastic, but what does that mean exactly?

All polymers can more or less be divided into two categories: thermoplastics and thermosets. The main difference between them is how they react to heat. Thermoplastics like Delrin, for example, melt in the heat, while thermosets remain “set” once they’re formed. Understanding the technical distinction between these types of materials is essential to CNC machining them properly.

What type of thermoplastic is Delrin in particular? Acetal homopolymer is a semi–crystalline, engineering thermoplastic.

Properties & Grades of Machined Delrin

This strong, stiff and hard acetal homopolymer is easy to machine and exhibits dimensional stability and good creep resistance, among several other desirable qualities. Delrin is also known for its superior friction resistance, high tensile strength, and its fatigue, abrasion, solvent and moisture resistance.

The latter quality allows Delrin to significantly outperform other thermoplastics like Nylon in high moisture or submerged environments without losing high-performance in the process. In other words, Delrin can retain its low coefficient of friction and good wear properties in wet environments.

One of the main reasons for Delrin’s popularity is its sheer versatility. The above blend of unique qualities makes Delrin broadly applicable to various industries in the medical, aerospace and energy sectors. For example, you can machine Delrin for medical implants and instruments, or for industrial bearings, rollers, gears, and scraper blades. It is ideal for smaller applications at temperatures below 250 °F (121°C) and can have centerline porosity.

Some of the Delrin grades we regularly machine at AIP include:

PTFE-Filled Acetals

PTFE (polytetrafluoroethylene) filled grades of Delrin is ideal where impact strength and wear capability are of the highest importance.

Glass-Reinforced Acetals

Acetals that are reinforced with glass have a much higher strength and greater heat resistance than other grades of Delrin.

FDA-Compliant Acetals

There are FDA-compliant grades of Delrin available for use in medical and food-related applications.

Machining Delrin

It’s true that Delrin is an easy material to work with in terms of machining. It is a very stable material, which makes precise, tight tolerances easier to achieve for this thermoplastic.

While machining, keep in mind that Delrin is sensitive to heat at or above 250 °F (121°C).

Balance the material removal as best as you can to keep your dimensions stable.

We also suggest non-aromatic, air-based coolants to achieve optimum surface finishes and close tolerances. Coolants have the additional benefit of extending tool life as well.

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as medical and life sciences. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats, and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

Delrin Machining Guide: Supportive Information

General Engineering Materials

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What are the advantages of plastics over metals?

November 16, 2018

AIP explains the advantages of using plastics over metals in our infographic below, with special emphasis on how each industry benefits from using polymers. Read on to learn all about it from the plastics professionals.

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Where Does This Part Go?

September 26, 2018

PPS Wheel Bushing | AIP Precision Machining

If you’ve been to a popular Florida amusement park, then it’s possible you’ve encountered the latest part starring in our “Where Does This Part Go?” series.

Find out why this part really makes a “splash” in the section below…

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Machining PPS: A Plastics Guide

August 30, 2018

An Informational Brief on Polymer Machining

Did you know that PPS (or Polyphenylene sulfide) products offer the broadest resistance to chemicals of any high-performance thermoplastic? It’s no surprise that this makes them a popular choice for industrial applications such as wheel bushings, chemical pumps, and compound clamp rings for semiconductor wafers.

What goes into machining this thermoplastic, however, and how does it differ from metal machining, injection molding, or 3D printing?

With Machining PPS: A Plastics Guides, AIP provides you with a guide to this material and its machining process. First, let’s start with the basics: thermoplastics vs thermosets.

Machining Thermoplastics vs Thermosets

We’ve already said that PPS is a thermoplastic, but what does that mean exactly?

All polymers can more or less be divided into two categories: thermoplastics and thermosets. The main difference between them is how they react to heat. Thermoplastics like PPS, for example, melt in heat, while thermosets remain “set” once they’re formed. Understanding the technical distinction between these types of materials is essential to CNC machining them properly.

What type of thermoplastic is PPS in particular? It’s a semi-crystalline, high-performance thermoplastic that has an extremely stable molecular structure. The chemical resistance of PPS is often compared to PEEK and fluoropolymers.

Properties & Grades of Machined PPS

There’s a lot to like about PPS’s material properties. As we mentioned before, PPS has exceptional chemical resistance that makes its bearing grades especially favorable for the chemical industry or caustic environments. In particular, its resistance to acids, alkalis, ketones, and hydrocarbons lend PPS stellar structural performance in harsh chemicals.

Additionally, PPS materials are inert to steam as well as strong bases, fuels and acids. Combine that with a low coefficient of thermal expansion and zero moisture absorption, and you get a material that is ideal for continuous use in corrosive or hostile environments. PPS has replaced stainless steel for a lot of industrial applications for this reason.

Most impressively, PPS will not dissolve at temperatures below approximately 200 °C, no matter what solvent is used. In fact, all grades of PPS share UL94 V-0 flammability ratings, without requiring flame retardant additives, resulting in an excellent material for aircraft where flame resistance is paramount.

Some grades of PPS that we regularly machine at AIP Precision Machining include Ryton®, Fortron®, TECHTRON®, TECTRON® HPV, TECATRON PVX and TECATRON CMP.

Machining PPS

Annealing PPS

The process of annealing and stress-relieving PPS reduces the likelihood of surface cracks and internal stresses occurring in the material. Post-machining annealing also helps to reduce stresses that could potentially contribute to premature failure. AIP’s special annealing process for PPS is designed to take the specific properties of PPS into account, and we advise anyone working with PPS to hire a manufacturer that understands its unique demands.

Machining PPS

PPS is a fantastic material for machining. Its low shrinkage and stable dimensional properties make it easy to machine to incredibly tight, precise tolerances. A unique characteristic of PPS is that when dropped, it sounds just like a piece of metal hitting the floor.

PPS, like many other thermoplastics, is notch sensitive, so take care to avoid sharp corners in design. We recommend carbide tipped cutting tools for working with PPS as they provide an ideal speed and surface finish.

We also suggest non-aromatic, water-soluble coolants, such as pressurized air and spray mists, to achieve optimum surface finishes and close tolerances. Coolants have the additional benefit of extending tool life as well. No known coolants attack nor degrade PPS.

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats, and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

To learn more, read our article “Three Ways to Ensure Sterilization in Your Plastic Machined Medical Applications.”

PPS Machining Guide: Supportive Information

Chemical Resistant Materials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

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Machining TORLON: A Plastics Guide

May 30, 2018

An Informational Brief on Polymer Machining

AIP Precision Machining has worked with many thermoplastics over the past three decades, including TORLON: a PAI, or polyamide-imide, engineered by Solvay Specialty Polymers.

Due to its reliable performance at severe levels of temperature and stress, TORLON is ideal for critical mechanical and structural components of jet engines, automotive transmissions, oil recovery, off-road vehicles and heavy-duty equipment.

AIP has over 35 years of experience machining complex components from TORLON and various other thermoplastic materials. We are providing this Machining TORLON Guide as yet another insightful technical brief about our polymer component manufacturing process, and how it differs from that of metal machining, injection molding, or 3D printing.

Plastic CNC Machining

Before discussing the process of machining TORLON, it’s important to understand exactly what plastic machining is.

CNC (Computer Numerical Control) machining is a process in the manufacturing sector that involves the use of computers to control machine tools. In the case of plastic machining, this involves the precise removal of layers from a plastic sheet, rod, tube or near net molded blank.

The early history of CNC machining is almost as complex as a modern CNC system. The earliest version of computer numerical control (CNC) technology was developed shortly after World War II as a reliable, repeatable way to manufacture more accurate and complex parts for the aircraft industry. Numerical control—the precursor to CNC—was developed by John Parsons as a method of producing integrally stiffened aircraft skins.

Parsons, while working at his father’s Traverse City, Michigan-based Parsons Corp., had previously collaborated on the development of a system for producing helicopter rotor blade templates. Using an IBM 602A multiplier to calculate airfoil coordinates, and inputting this data to a Swiss jig borer, it was possible to produce templates from data on punched cards.

Parsons’ work lead to numerous Air Force research projects at the Massachusetts Institute of Technology (MIT) starting in 1949. Following extensive research and development, an experimental milling machine was constructed at MIT’s Servomechanisms Laboratory.

Due to the many different kinds of polymers and composites, it’s important to have strong technical expertise of polymer materials when machining plastic components; some plastics are brittle, for example, while others cut similarly to metal. The challenge of plastics is their wide range of mechanical and thermal properties which result in varying behavior when machined. Therefore, it’s important to understand the polymer structure and properties of TORLON if you’re machining it.

Thermoplastics vs Thermosets

When it comes to polymers, you have two basic types: thermoplastics and thermosets. It’s crucial to know which one you’re working with due to distinct differences between how these two main polymer categories react to chemicals and temperature.

Thermoplastics soften when heated and become more fluid as additional heat is applied. The curing process is completely reversible as no chemical bonding takes place. This characteristic allows thermoplastics to be remolded and recycled without negatively affecting the material’s physical properties.

They possess the following properties:

• Good Resistance to Creep

• Soluble in Certain Solvents

• Swell in Presence of Certain Solvents

• Allows for Plastic Deformation when Heated

Thermosets plastics contain polymers that cross-link together during the curing process to form an irreversible chemical bond. The cross-linking process eliminates the risk of the product re-melting when heat is applied, making thermosets ideal for high-heat applications such as electronics and appliances.

They possess the following properties:

• High Resistance to Creep

• Cannot Melt

• Insoluble

• Rarely Swell in Presence of Solvents

Phenolic, Bakelite, Vinyl Ester and Epoxy materials would be considered examples of a thermoset, while ULTEM, PEEK, DELRIN and Polycarbonate materials are examples of thermoplastics.

The thermoplastic category of polymers is further categorized into Amorphous and Crystalline polymers per the figure below:

TORLON is considered an amorphous, high-performance thermoplastic. Most amorphous polymers are thermoform capable, translucent and easily bonded with adhesives or solvents.

Various Grades of Machined TORLON

What makes TORLON unique is how it possesses both the incredible performance of thermoset polyimides and the melt-processing advantages of thermoplastics. The compressive strength of (unfilled) TORLON PAI is double that of PEEK and 30% higher than that of ULTEM PEI. In fact, TORLON is considered the highest performing, melt-processible plastic.

High-strength grades of TORLON retain their toughness, high strength and high stiffness up to 275°C. This and its impressive wear resistance allow TORLON to endure in hostile thermal, chemical and stress conditions considered too severe for other thermoplastics. TORLON is also resistant to automotive and aviation fluids, making it a favorite of aerospace and automotive engineers.

One concern of using TORLON is that its moisture absorption rate is not as low as other high-performance plastics, so special care should be taken when designing components for wet environments.

There’s more than one particular type of TORLON PAI you can machine, and each has slightly different properties for perfecting this material’s use in different applications.

Here are several grades of TORLON PAI we machine regularly at AIP Precision Machining.

TORLON 4203

TORLON 4203 is the unfilled or natural grade of TORLON PAI that outperforms other grades with the best impact resistance and the most elongation. TORLON 4203 PAI can be used for a variety of applications but due to its good electrical properties, it is commonly machined for electronic equipment manufacturing, valve seals, bearings and temperature test sockets.

TORLON 4301

TORLON 4301 is a wear-resistant grade of TORLON PAI containing PTFE and graphite. It has high flexural and compressive strength with a low coefficient of friction, as well as good mechanical properties. Typical applications of 4301 are anything that requires strength at high temperature with wear resistance and low friction. This material is useful for parts such as thrust washers, spline liners, valve seats, bushings, bearings and wear rings.

TORLON 4XG

TORLON 4XG is a 30% glass-reinforced extruded grade of PAI well suited to higher load structural or electronic applications. When you need a high degree of dimensional control, this grade offers the high-performance you need. Various uses of TORLON 4XG include burn-in sockets, gears, valve plates, impellers, rotors, terminal strips and insulators, among others.

TORLON 4XCF

TORLON 4XCF is a 30% carbon-reinforced extruded grade of PAI that has the lowest coefficient of thermal expansion and the most impressive fatigue resistance of all plastic materials. This uncommon grade works well as a replacement for metal applications as well as mission-critical aerospace components, in addition to impellers, shrouds and pistons.

Machining TORLON

Annealing TORLON
TORLON PAI can be received in the form of rods, sheets, tube or film. Stress-relieving before machining through an annealing process is crucial, as it reduces the likelihood that surface cracks and internal stresses will occur from the heat generated. This also helps prevent any warping or distortion of your plastic materials.

TORLON additionally benefits from post-machining annealing to reduce any stress that could contribute to premature failure. Extruded TORLON parts, such as those machined from TORLON 4XCF and TORLON 4XG, benefit from an additional cure after machining to further enhance wear resistance; this is unique to PAI. Proper annealing of Torlon can require more than seven days in special ovens at AIP.

If the machine shop you are working with does not have a computer controlled annealing oven for plastics, then “head for dee hills” as they are obviously not TORLON machining experts.

Machining TORLON

An important consideration to have when machining TORLON PAI is how abrasive it is on tooling. If you’re machining on a short run, carbide tooling can be used, but polycrystalline (PCD) tooling should be considered for lengthier runs, machining for tight tolerance and any time you are working with reinforced grades.

Another thing to keep in mind when machining extruded TORLON shapes is that they have a cured outer skin, which is harder than interior sections. The outer skin offers the best wear and chemical resistance. If wear resistance and chemical resistance needs to be optimized, extruded TORLON should be re-cured.

TORLON PAI will nearly always require the use of coolants due to its stiffness and hardness. Non-aromatic, water-soluble coolants are most suitable for ideal surface finishes and close tolerances. These include pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

Many metal shops use petroleum-based coolants, but these types of fluids attack TORLON. Many past experiences have shown parts going to customer without cracks, only to develop cracks over time due to exposure to metal machine shop fluids. Be sure to use a facility like AIP who machines polymers and only polymers.

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical. To ensure the highest level of sanitation down to the sub-molecular level, AIP Precision Machining designs, heat-treats and machines only plastics, with any sub-manufactured metalwork processed outside our facility.

TORLON Machining Guide: Supportive Information

Medical Sector Biomaterials Guide

Energy Sector Materials Guide

Aerospace Sector Materials Guide

Amorphous Materials

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