Category: Plastic Machining

Machining Polypropylene (PP): A Plastics Guide

May 18, 2020

An Informational Brief on Polymer Machining

 

Since it was first polymerized in 1954 by Karl Rehn and Giulio Natta, polypropylene (PP) has become one of the leading polymer choices for a wide array of applications from automotive to commercial to medical.

 

Polypropylene plays a significant role in medical applications due to its high chemical resistance, lightweight, radiolucency and repeated autoclavability. Furthermore, medical grade PP exhibits good resistance to steam sterilization and moisture resistance. Disposable syringes, instrument or implant caddies and fluid delivery systems are the most common medical application of polypropylene. Other applications include medical vials, diagnostic devices, petri dishes, intravenous bottles, specimen bottles and surgical trays.

 

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AIP has over 35 years of experience machining complex components from thermoplastics like polypropylene. In this insightful technical brief, we will discuss what goes into machining polypropylene and how it differs from other manufacturing options such as metal machining, injection molding, and 3D printing.

 

Homopolymer vs Copolymer – What’s the Difference?

 

The two main types of polypropylene available on the market are homopolymers and copolymers. Although they share many properties, there are some differences that help guide machinists and engineers in choosing the right material for their PP application. For the purposes of this blog, we will briefly review the differences between PP homopolymer and PP copolymer.

 

PP Homopolymer PP Copolymer
  • High strength to weight ratio and stiffer & stronger than copolymer
  • Good chemical resistance and weldability
  • Good processability
  • Good impact resistance
  • Good stiffness
  • Food contact acceptable
  • Suitable for corrosion resistant structures
  • Bit softer but has better impact strength; tougher and more durable than homopolymer
  • Better stress crack resistance and low temperature toughness
  • High processability
  • High impact resistance
  • High toughness
  • Not preferable for food contact applications

 

Properties of Polypropylene

 

Keeping information about the properties of a thermoplastic beforehand is always beneficial. This helps in selecting the right thermoplastic for an application. It also assists in evaluating if the end use requirement would be fulfilled or not. Here are some of the key properties of polypropylene:

 

Polypropylene is characterized by excellent chemical resistance in corrosive environments, resistance to cleaning agents and solvents and by a high heat deflection temperature.

 

It also has great dimensional stability and is fairly easy to machine. As noted above, it is available in heat-stabilized homopolymer and copolymer grades. At AIP, we machine POLYSTONE P, PROPYLUX HS and HS2, PROTEUS LSG HS PP from MCAM, TECAPRO MT and TECAFINE PP from Ensinger. Interesting to note is that both the PROPYLUX and TECAPRO heat stabilized PP grades are available in both standard and custom colors for medical sorting and sizing organization. Whatever your application, our machinists can help you in material selection, sizing and manufacturing techniques from concept to completion.

 

Melting Point of Polypropylene – The melting point of polypropylene occurs at a range.

 

Homopolymer: 160 – 165°C
Copolymer: 135 – 159°C

 

Density of Polypropylene – PP is one of the lightest polymers among all commodity plastics. This feature makes it a suitable option for lightweight\weight saving applications.

 

Homopolymer: 0.904 – 0.908 g/cm3
Random Copolymer: 0.904 – 0.908 g/cm3
Impact Copolymer: 0.898 – 0.900 g/cm3

 

Machining Polyproylene

 

Annealing Polypropylene

Due to its low annealing temperature, PP, like any polymer under heat and pressure, has a tendency to deform during machining. The annealing process at AIP greatly reduces the chances of these stresses occurring from the heat generated during machining PP and other polymers. Our machinists use computer controlled annealing ovens for the highest quality precision machining.

 

Machining Polypropylene

As a part of the polyolefin family, PP is semi-crystalline, which means that it can be machined at tight tolerances. We recommend non-aromatic, water-soluble coolants because they are most suitable for ideal surface finishes and close tolerances.

 

Bear in mind that polypropylene has variable levels of thermal expansion and will move a great deal with slight temperature changes. Some examples are pressurized air and spray mists. Coolants have the additional benefit of extending tool life as well.

 

Some companies machine both metals and plastics, which has detrimental outcomes for clients. 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 that only machines polymers.

 

Preventing Contamination

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace and medical 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. This allows us to de-risk the process from metallic cross contamination.

 

Polypropylene Machining Guide: Supportive Information

 

ISO 13485:2016 Certification
ISO 9001:2015 Certification

 

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What Makes a Plastic Medical Grade?

May 5, 2020

A discussion with the plastics pros at AIP on how to choose the right plastic for your medical application

 

When it comes to selecting a polymer for a medical application, there are a myriad of factors that play into deciding which grade of polymer is the best candidate. Of course, the number one concern in medical device design is safety of human life.

 

For this reason, trends in medical device design are moving toward miniaturization and portability. Additionally, sterilization and cleanliness continue to lead design considerations globally, requiring devices to withstand a range of chemicals and sterilization techniques.

 

As a precision plastics machining company, AIP has over 35+ years of experience working with medical OEMs to develop parts for critical medical devices. In this issue of our monthly blog, we will discuss what makes a polymer medical grade and how to choose the right polymer for a medical device application.

 

What are medical grade plastics?

 

Let’s begin with what a medical grade plastic is. Medical-grade plastics refer to plastics used to make medical products, products for in vitro diagnostics and primary packaging for pharmaceuticals.

 

Most importantly, plastics used in the medical field are coming in contact with human tissue, fluids, chemicals, drugs and many more substances. There are literally thousands of medical applications from packaging to spinal implants. Based on this information, your supplier should be familiar with the types of polymers and composites you need machined. They should additionally know the best machining process for your application. That’s why design conception is crucial as the first step.

 

1. Design requirements and constraints

 

First and foremost, what is the function of the polymer for the device?

 

Your machine shop should be asking you in depth questions about your medical application. Questions to consider include:

 

  • Should the material be biocompatible?
  • Is the product for single use?
  • Will the component undergo sterilization? If so, which method?
  • Does color and aesthetics matter in the machining process?
  • Is UV resistance needed?
  • What tolerances must be met for temperature, wear, impact, etc?

 

The following material selection flow-chart displays the overall process of developing a medical grade plastic part or device:

 

Market Needs Infographic

 

2. Industry Standards

 

What industry standards and regulations control the production of the material?

 

At AIP, our plastics are processed with strict hygienic procedures to ensure the highest level of sanitation. Make sure that your machining company is compliant and/or registered with the appropriate regulatory organizations. Some common medical certifications include the following:

 

  • ISO 10993
  • ISO 13485:2016
  • FDA Registered

 

3. Biocompatibility

 

How long does the component need to be in contact with the human body or tissue?

 

There are three categories of contact duration if a component is subject to body tissue or fluid:

 

  • Short-term contact (Less than 24 hours)
  • Medium term contact (Between 1-30 days)
  • Long-term or Permanent contact (Greater than 30 days)

 

4. Sterilization/Cleanliness

 

Will the device need to be resistant to chemicals or undergo multiple sterilizations?

 

Whether it’s a feeding tube, a drug delivery device or a surgical implant, the polymer material must be able to withstand chemical degradation and multiple sterilizations.

 

The most common sterilization methods include:

 

  • Radiation (gamma/e-beam)
  • Chemical (ETO)
  • Autoclave (steam)

 

Chemicals to consider for contact with the device could be:

  • Intravenous medications
  • Blood/Fluids/human tissue
  • Hospital cleaners – bleach, isopropyl alcohol, peroxides

 

5. Polymer Characteristics

 

What mechanical properties does the polymer need to fulfill?

 

Selecting a plastic material is based on a number of traditional material requirements such as strength, stiffness or impact resistance. Engineered thermoplastics like PC, PEEK, PPSU, POM, show excellent mechanical properties at low and high temperatures. These properties are required for a variety of climate conditions, including during transportation, where the influence of temperature on drop impact may result in different outcomes for device integrity.

 

Your machinist should be able to give you details about all the plastics in their portfolio such as:

 

  • High wear resistance
  • Tensile strength
  • Temperature resistance
  • Corrosion resistance
  • Durability
  • Dimensional stability

 

6. Aesthetics

 

Does the end product need to be a certain color or have certain qualities?

 

For instance, if it is a prosthetic for a foot, the polymer needs to be machined a certain shade to match skin tone.

 

7. Other Material Selection Factors

 

Anything else?

 

Other factors to consider and discuss with your machinist include additives for increasing the performance of the polymer, manufacturing process as well as the cost. Take into account the following:

 

  • Radiopacity
  • Conductive
  • Lubrication
  • Manufacturing feasibility
  • What manufacturing processes are you using and why?
  • Technical performance
  • Can we make this product with the material, and can we make it well?
  • Economics
  • If we can make it, can we make it for a reasonable cost?

 

At AIP, we are unrivaled experts in medical grade plastic machining.
Talk to our team about how to bring your project from concept to completion.

 

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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-PEIULTEM 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 - PBICELAZOLE 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

 

DURATRON PILike 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

 

TORLONDURATRON 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

 

TECHTRONTECHTRON 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

 

RADELWith 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-FKel-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

 

PEEKPEEK 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

 

KYNAR - PVDFAnother 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’s the deal with the .002 mm precision tolerance?

January 7, 2020

Learn about AIP’s precision machining capabilities for mission-critical components.

 

High-performance precision plastics require high-performance precision CNC machining.  CNC machines, or computer numerically controlled machines, are electro-mechanical devices that use tools at varying axes (usually 3-5) to produce a physical part from a computer design file.

 

Our modern society runs on CNC machined plastic components – from everyday household piping to critical spinal implants.  The breadth of materials, shapes and industries served is endless.

At AIP, we precision machine parts for industries such as the aerospace & defense, medical & life sciences and power & energy.  Each part that is CNC machined comes with design specifications and dimensional tolerances.  Our machinists are capable of crafting parts at .002 mm tolerance, which can make a whole lot of a difference in the performance of a mission-critical part.

 

Let’s back up a moment though.  What are dimensional tolerances? And how do you know if your project should demand a tighter tolerance?  Read on in this month’s blog to find out.

 

Let’s Talk About Tolerance

 

What are machining tolerances?

In CNC machining terms, tolerance, or dimensional accuracy, is the amount of deviation in a specific dimension of a part caused by the manufacturing process.  No machine can perfectly match specified dimensions.  The designer provides these specifications to the machinists based on the form, fit and function of a part.

 

How are tolerances measured?   

CNC machines are precise and measured in thousandths of an inch, referred to as “thou” among machinists.  Any system is usually expressed as “+/-”; this means that a CNC machine with a tolerance of +/- .02 mm can either deviate an extra .02 mm from the standard value or less .02 mm by the standard value.

 

A precision machining tolerance scale
 

Why are tolerances critical?

Tolerances keep the integrity and functionality of the machined part.  If the component is manufactured outside of the defined dimensions, it is unusable, since the crucial features are not fulfilling the intent of the design.

 

How close can a tolerance get?

Tolerance depends on the material that you use and the desired purpose of the design.  In plastics machining, the tolerances can be from +/- 0.10 mm to +/- 0.002 mm.  Tighter tolerances should only be used when it is necessary to meet the design criteria for the part.

 

When .002 mm Matters

 

What is the .002 mm difference?  In many industries, such as the medical industry, it is crucial to machine parts with extreme precision so that they can interact with human tissue or other medical devices.  In fact, when it comes to manufacturing medical applications, subtractive manufacturing (CNC machining) provides tighter tolerances than additive manufacturing (3-D printing).

 

 

Color Pencil compared to precision machining
(AIP PEEK Eye Implant)
 

Tight tolerances like the .002 mm are important because plastics are machined to interact with other parts.  In particular, CNC milled or turned plastics are unique designs for limited quantities, such as custom-made brackets and fasteners, or components for prototyping purposes.

 

One of the most critical considerations when applying tolerances is to take into account fits. This refers to how shafts will fit into bushings or bearings, motors into pilot holes, and so on. Depending on the application, the part may require a clearance fit to allow for thermal expansion, a sliding fit for better positioning, or an interference fit for holding capability.

 

As with anything that is precision machined, tighter tolerances demand time and skill.  Make sure to work with a certified company like AIP that has the infrastructure and expertise to complete your project with unmatched precision and unrivaled experience.

 

Let our team go to work for you

 

With 36+ years of experience in the industry, our dedicated craftsmen and ties to leading plastic manufacturers allow us to provide you with unrivaled knowledge and consulting in material selection, sizing, manufacturing techniques and beyond to best meet your project needs.

 

AIP offers a unique combination of CNC machining, raw material distribution, and consultancy as a reliable source for engineering information for materials such as PEEK, TORLON, ULTEM and more.

 

We are AS 9100D compliant; certified and registered with ISO 13485 and ISO 9001 and standards in our commitment to machining quality custom plastic components for specialized industrial sectors. Quality assurance is included as an integral part of our process and is addressed at every step of your project, from concept to completion.

 

READY FOR A CONSULTATION?

Tell us about your power & energy needs and we’ll get the job done quickly and efficiently at a competitive price.

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The Untold Story of Re-Useable Plastics

November 19, 2019

Learn about the re-useable capabilities of precision plastics

 

In the world of recycling, plastic tends to have a bad reputation or it gets whispered like a dirty word.  Indeed, according to the UN Environment Programm, one million plastic drinking bottles are purchased every minute.  This is certainly a disturbing statistic, and we are tasked with addressing the consequences of this waste.  However, it is important to distinguish the type of plastics causing severe pollution.  Plastic bottles and plastic bags are single-use, disposable plastics.  These are the ones that are clogging up the environment.

 

What people don’t discuss often is plastics that are re-usable and recyclable.  At AIP, the plastics that we precision machine are high grade, quality polymers made for durability and continuous use in the following industries: Aerospace and Defense; Medical and Life Sciences; Power and Energy; Specialized Industrial.  That means they are evergreen materials that will not only last, but could be repurposed for a different application altogether.  Read on to find out about some of the high-performance polymers we work with, what they are used for and how they can be recycled.

 

Everyday Sustainable Precision Plastics
Polymer Properties AIP’s Machined Applications
PPS Broadest chemical resistance; zero moisture absorption; dimensional stability; ultra-low wear factors and structural strength

*available in several grades

 Case Study: High-quality PPS wheel bushings for a theme park water ride.

  • Reduced ride downtime
  • Saved on maintenance and inventory costs
  • Lower energy cost
  • Efficient design
  • Low-wear
TORLON Highest performing, melt-processible plastic; maintains strength and stiffness up to 500 F; chemical, thermal and stress resistance

*available in several grades

 Ideal for critical mechanical and structural components for severe levels of temperature and stress

  • Jet Engine Components
  • High Temperature Electrical Connectors
  • Automotive Transmission components
  • Wear Rings in Oil Recovery
  • Valve Seats
PEEK Biocompatible; abrasion and chemical resistant; low moisture absorption; very low smoke and toxic gas emission

*available in several grades

 Case Study: PEEK Dynamic Telescopic Craniotomy (skull plate for brain traumas

  • Reduced ride downtime
  • Saved on maintenance and inventory costs
  • Lower energy cost
  • Efficient design
  • Low-wear
RADEL Impact resistance; hydrolytic stability; excellent toughness; chemical resistance; heat deflection temperature of 405 F (207 C)
ULTEM Excellent heat and flame resistance; high rigidity and strength; low thermal conductivity; highest dielectric strength

*available in several grades

 Used as structural components in several industries

  • High-voltage circuit-breaker housings
  • High-temperature bobbins, coils, fuse blocks and wire coatings
  • Jet-engine components
  • Aircraft interior and electrical hardware parts
  • Microwave applications
  • Replaces glass in medical lamps

 

Thermoplastics – The Green Plastic

 

There are two types of polymers – thermoplastics and thermosets.  The plastics that we work with primarily at AIP are thermoplastics.  So, what’s a thermoplastic and how is it re-usable or recyclable?

 

It’s all about how the polymer reacts to chemicals and temperature.  Thermoplastics soften when heated and become more fluid, which makes them a very flexible polymer.  For this reason, these plastics can be remolded and recycled without losing their mechanical properties or dimensional stability.  Let’s go in depth on some of the common thermoplastics we use for evergreen applications.

 

The AIP case study focusing on the use of PPS for the log flume ride bushing component is an excellent example of a thermoplastic built and machined for continuous use.  The bushing made from PPS could be used over and over again without wear.  Furthermore, it could be immersed in water and other chemicals without losing dimensionality or durability.

 

PEEK and ULTEM are both common polymers we machine at AIP.  With PEEK’s high chemical resistance and biocompatibility, it is ideal for surgical applications such as the Dynamic Telescopic Craniotomy Case Study.  This polymer can withstand the internal temperatures and fluids of the body for extended use.

 

ULTEM is known for its strength and rigidity in extreme environments and temperatures.  This polymer is often used for re-useable medical instruments, since it reacts well to autoclave sterilizations.  Additionally, it’s flammability rating and dimensional stability make it ideal as a weight-saving aerospace component.

 

As the plastics industry continues to innovate, the next generation of research will turn towards more sustainable and environmentally conscious materials.  Thermoplastics are one of the pioneers of this industry – leading plastics into the future as a material that can be reused and recycled.

 

Unrivaled Expertise. Unparalleled Results

 

Helicopter landing on shipWith 36+ years of experience in the industry, our dedicated craftsmen and ties to leading plastic manufacturers allow us to provide you with unrivaled knowledge and consulting in material selection, sizing, manufacturing techniques and beyond to best meet your project needs.

 

AIP offers a unique combination of CNC machining, raw material distribution, and consultancy as a reliable source for engineering information for materials such as PEEK, TORLON, ULTEM and more.

 

We are AS 9100D compliant; certified and registered with ISO 13485 and ISO 9001 and standards in our commitment to machining quality custom plastic components for specialized industrial sectors. Quality assurance is included as an integral part of our process and is addressed at every step of your project, from concept to completion.  Unrivaled Expertise.  Unparalleled Results.

 

 

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Machining Polysulfone (PSU): A Plastics Guide

October 16, 2019

An Informational Brief on Polymer Machining

 

Among the many plastics AIP precision machines, PSU (Polysulfone) is a high-performance thermoplastic made from UDEL Resin.  This particular thermoplastic is able to retain its properties in temperatures ranging from -150°F (-100°C) to 300°F (150°C).  This precision machined plastic also has excellent radiation stability, chemical resistance as well as hydrolysis resistance for continuous use in hot water and steam.

 

In many applications, PSU is used over stainless steel parts or aluminum as the material is seven times lighter than stainless steel and can also be steam-cleaned in areas like chemical labs.  For this reason, it has a wide range of uses in the following industries:  aerospace and defense, medical and life sciences as well as specialized industrial applications.

 

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

 

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that PSU 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 PSU, 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.

 

The table below outlines the main properties of thermoplastics versus thermosets:

 

Thermoplastics

Thermosets
  • Good Resistance to Creep
  • Soluble in Certain Solvents
  • Swell in Presence of Certain Solvents
  • Allows for Plastic Deformation when Heated
  • High Resistance to Creep
  • Insoluble
  • Rarely Swell in Presence of Solvents
  • Cannot Melt

 

From there, thermoplastics are categorized into amorphous or crystalline polymers per the figure below:

 

Source: https://www.ejbplastics.com
 

Based off of the chart, PSU is an amorphous, high performance engineering thermoplastic, meaning its molecular structure is randomly formed.  The result is that amorphous materials soften gradually with temperature increase, making them easy to thermoform.

 

Properties of PSU (Polysulfone)

 

Amorphous thermoplastics are usually translucent in color, but the gradients vary.  PSU, for instance, is amber semi-transparent.

 

Since they are isotropic in flow, they have better dimensional stability than semi-crystalline plastics and are less likely to warp.  Thermoplastics like PSU offer superior impact strength and are best used for structural applications.

 

The materials bond well using adhesives. They also tend to offer excellent resistance to hot water and steam, good chemical resistance, stiffness and strength. PSU and PEI are especially good examples of amorphous thermoplastics offering these qualities.

 

Machining PSU (Polysulfone)

 

Annealing PSU

 

Like many amorphous thermoplastics, PSU is especially sensitive to stress-cracking, so stress-relieving through an annealing process is highly recommended before machining.  Annealing PSU greatly reduces the likelihood that surface cracks and internal stresses will occur from the heat generated. Post-machining annealing also helps to reduce stresses that could potentially contribute to premature failure.  AIP uses computer controlled annealing ovens for the highest quality precision machining of PSU and other thermoplastics.

 

Machining PSU

 

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 amorphous thermoplastics like PSU. 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 only machines polymers.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.

 

PSU (Polysulfone) Machining Guide Supportive Information

Amorphous Materials Guide

 

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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.

 

Interested to learn more? Read “Plastics in Aerospace: The Secret to Fuel-Efficient Aircraft”

 

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Machining Kynar Resin (PVDF): A Plastics Guide

July 1, 2019

An Informational Brief on Polymer Machining

 

Kynar®, Polyvinylidene Difluoride (PVDF) is a specialty fluoropolymer thermoplastic known for its ease of processing and its versatility in a variety of applications.  PVDF’s manufacturing not only ensures durability in its utility, but also delivers an innate resistance to acids, bases, high temperatures, and solvents.  Harsh industrial environments are no match for PVDF parts, which is why it is commonly used in environments requiring extreme resistance to a broad range of chemicals.

 

Additional demand for fluoropolymers like Kynar® PVDF is driven by the increasing trend of specialized, small-batch production for customized parts and components. Companies developing prototypes find it extremely convenient to have access to a fluoropolymer part manufacturer such as AIP.  Furthermore, AIP’s experience with custom-engineering plastics ensures our customers’ evolving needs are always met with the same level of innovation and excitement for creating new ways to deliver value in fluoropolymer applications.

 

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

 

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that PVDF 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 PVDF, 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 PVDF in particular? PVDF is a semi-crystalline, high purity engineering thermoplastic, meaning its molecular structure is highly ordered.

 

Properties & Grades of Machined Kynar® (PVDF)

 

As a thermoplastic, Kynar® PVDF offers industrial-grade resistance to pH changes due to varying thermal conditions, as well as solvent-resisting capabilities. This can be an advantage in petrochemical industries where fluoropolymer parts are in contact with or exposed to bursts of gases, oil or detergents.

 

It should also be noted that Kynar® PVDF is known for its high degree of crystallinity, which results in a stronger and strain-resisting component. Add to that a natural resistance to fungus, ozone and weather, which makes Kynar® PVDF a great fluoropolymer for coatings and manufactured parts exposed to the elements.

 

Finally, adding to its versatile performance in industrial environments, Kynar® PVDF provides excellent resistance to nuclear radiation, allowing it to be used in both Power Generation and military applications.

 

AIP offers a range of Kynar® and PVDF grades that provide different strength, thermal stability, and corrosion resistance and can help you select the best grade of PVDF for your application..

 

Machining Kynar® (PVDF)

 

Annealing PVDF

 

The process of annealing and stress-relieving PVDF 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.

 

Machining Kynar

 

PVDF offers ease of machining and tight tolerances due to its inherent strength, toughness and dimensional stability. Machining PVDF isn’t too different from machining metals as a result of this; pretend you’re machining brass. Unlike metal, though, PVDF (like all thermoplastics) will deform if you hold it too tightly as it yields easily.

 

We generally recommend Tungsten Carbide Alloy Tooling. Also, keep the part very cool and support it well.

 

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.

 

Case in point, Kynar® PVDF can be manufactured into industrial equipment components that may include piping and tubing, valves, tanks, nozzles, and fittings—among many other formats. It can also be combined with other materials, helping customers innovate and create new product classes with utility that exceeds its original applications.

 

Preventing Contamination

 

Contamination is a serious concern when machining polymer components for technically demanding industries such as aerospace 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.  This allows us to de-risk the process from metallic cross contamination.

 

Kynar® (PVDF) Machining Guide: Supportive Information

 

Chemical Resistant Materials

 

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Machining Vespel (PI): A Plastics Guide

June 3, 2019

An Informational Brief on Polymer Machining

 

Vespel Polyimide (PI) is a high-performance polymer frequently machined for end-use in aerospace, semiconductor and transportation technology. This material thrives in extreme environments with high strength, chemical resistance, high temperatures, and a low coefficient of friction. It also has impressive sealing and wear properties.

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

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that Vespel 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 Vespel, 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 Vespel in particular? PI is a semi-crystalline engineering thermoplastic, meaning its molecular structure is highly ordered.

 

Properties & Grades of Machined Vespel

 

Combining heat resistance, lubricity, dimensional stability, chemical resistance and creep resistance, Vespel works well in hostile and extreme environmental conditions. Vespel is able to overcome severe sealing and wear. As we mentioned before, these properties allow Vespel to be commonly machined for semiconductors and transportation applications.

Unlike most plastics, Vespel doesn’t produce significant outgassing, even at high temperatures. This makes it useful for lightweight heat shields and crucible support. Vespel also performs well in vacuum applications and extremely low cryogenic temperatures. However, it does absorb a small amount of water, which results in a longer pump time while placed in a vacuum.

Although there are polymers that surpass individual properties of this polyimide, the combination of these factors is Vespel’s primary advantage.

We regularly machine various grades of Vespel at AIP Precision Machining, including the Vespel SP and Vespel SCP family of products from DuPont. The former group is known for their durability and exceptional thermal resistance, while the latter is known for its mechanical properties and thermal stability.

 

Machining Vespel

 

Annealing Vespel

 

The process of annealing and stress-relieving Vespel 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.

 

Machining Vespel

 

Vespel offers ease of machining and tight tolerances due to its inherent mechanical strength, stiffness and dimensional stability. Machining Vespel isn’t too different from machining metals as a result of this; pretend you’re machining brass. Unlike metal, though, Vespel (like all thermoplastics) will deform if you hold it too tightly.

We generally recommend Tungsten Carbide Alloy Tooling, although we recommend diamond tooling for large volume runs or work requiring close tolerances. Be wary of overheating Vespel when you machine it. It shouldn’t become so hot that you can’t grasp it with your bare hands.

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 aerospace 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.

 

Vespel Machining Guide: Supportive Information

DuPont Machining Vespel Guide

Aerospace Market Materials

Energy Sector Materials

Extreme Performance Materials

 

 

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Machining Celazole PBI: A Plastics Guide

April 29, 2019

An Informational Brief on Polymer Machining

 

Celazole, known as Polybenzimidazole (PBI), is a synthetic fiber characterized by exceptional thermal and chemical stability. PBI is commonly used in electrical insulators and high strength situations, where it shines due to its compressive strength and insulation properties.

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

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

 

Machining Thermoplastics vs Thermosets

 

We’ve already said that Celazole 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 Celazole, 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 Celazole in particular? PBI is an amorphous engineering thermoplastic.

PBI is characterized by high strength; it exhibits excellent thermal stability, is hydrolytically stable after exposure to high-pressure steam or water, is broadly resistant to hydrocarbons, alcohols, weak acids, weak bases, hydrogen sulfide, chlorinated solvents, oils, heat transfer fluids and many other organic chemicals.

 

Properties & Grades of Machined Celazole

 

Celazole PBI is one of the highest performing thermoplastics on the market today; it has the lowest coefficient of thermal expansion of all unfilled plastics. At above 400°F (204°C), Celazole possesses the highest mechanical properties of any thermoplastic. By itself, PBI offers a continuous use operating temperature of 1,004°F (540°C). Even after being submerged in hydraulic fluid at 200°F (93°C) for thirty days, Celazole retains 100% tensile strength.

When you combine those exceptional qualities with excellent wear and frictional properties, as well as extreme resistance to chemicals and hydrolysis, it’s no wonder that Celazole excels in industries that require high-performance in hostile environments. For example, semiconductor parts made with Celazole can last twice as long as those made with polyimides.

Other applications that Celazole is commonly machined for include gas plasma equipment, aircraft engine components and other applications for “hot” section areas or environments with harsh chemicals. Whenever dielectric properties are required or high-strength situations arise, Celazole PBI is an ideal material for your application.

We regularly machine various grades of Celazole at AIP Precision Machining, including Celazol U-60 and Duratron PBI.

 

Machining Celazole PBI

 

Annealing Celazole

The process of annealing and stress-relieving Celazole 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.

 

Machining Celazole

 

Celazole is known for its extreme hardness, which poses a challenge to HSS machining. Instead, carbide and polycrystalline diamond tools are recommended for machining Celazole PBI.

Keep in mind that Celazole PBI is notch sensitive as well and that high tolerance components machined from this thermoplastic should be stored and sealed to prevent any dimensional changes from moisture absorption.

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.

 

Celazole PBI Machining Guide: Supportive Information

 

Extreme Performance Materials

Aerospace Market Materials

Energy Sector Materials

 

 

 

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