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7 Need-to-Know Polypropylene Material Properties

Sep. 23, 2024

7 Need-to-Know Polypropylene Material Properties

Custom wire baskets are frequently outfitted with different polymers to improve the basket&#;s structural durability or to better hold and protect delicate parts. Finding the right polymer for your steel wire basket coating is determined by your process. One of the more popular polymers used for basket coatings, polypropylene, has distinct properties that may make it ideal for your needs.

What Is Polypropylene Material?

Polypropylene is a material that is frequently compared to PVC (polyvinyl chloride). While not as frequently used as PVC, polypropylene is still a useful material for coating custom wire baskets.

A rigid, crystalline thermoplastic, polypropylene is produced from propene or propylene monomer. It&#;s one of the cheapest plastics available today and is used in applications both as a plastic and a fiber in industries such as automotive manufacturing, furniture assembly, and the aerospace sector.

What Is Polypropylene Used For?

Due to polypropylene structure&#;s rigidity and relative cheapness, it&#;s used in various applications. It has good chemical resistance and weldability, which makes it ideal for the automotive industry, consumer goods, furniture market, and industrial applications such as custom wire baskets.

Some common uses of polypropylene include:

Packaging Applications: Polypropylene&#;s structure and strength make it a cheap and ideal packing application.
Consumer Goods: Polypropylene is used for many consumer goods&#;including translucent parts, housewares, furniture, appliances, luggage, toys and more.

Automotive Applications: Polypropylene is widely used in automotive parts because of its low cost, weldability, and mechanical properties. It can mostly be found in battery cases and trays, bumpers, fender liners, interior trim, instrumental panels and door trims.
Fibers and Fabrics: Polypropylene is utilized in a host of fiber and fabrics applications including raffia/slit-film, tape, strapping, bulk continuous filament, staple fibers, spun bond, and continuous filament.
Medical Applications: Due to polypropylene&#;s chemical and bacterial resistance, it is used for medical applications including medical vials, diagnostic devices, petri dishes, intravenous bottles, specimen bottles, food trays, pans, pill containers, and disposable syringes.

Industrial Applications: The high tensile strength of polypropylene&#;s structure, combined with its resistance to high temperatures anc chemicals, makes it ideal for chemical tanks, sheets, pipes, and Returnable Transport Packaging (RTP).

What Are the Properties of Polypropylene?

Some of the polypropylene structure and material properties that you should know when choosing a coating for your custom wire basket include:

Chemical Resistance. Polypropylene is generally noted as having a high resistance to chemicals compared to polyethylene (&#;regular&#; plastic). Polypropylene will resist many organic solvents, acids, and alkalines. However, the material is susceptible to attack from oxidizing acids, chlorinated hydrocarbons, and aromatics.
Tensile Strength. Compared to many materials, polypropylene&#;s structure has a good tensile strength&#;somewhere around 4,800 psi. This allows the material to withstand fairly heavy loads, despite being lightweight.
Impact Tolerance. While polypropylene has a good tensile strength, its impact resistance leaves something to be desired when compared to polyethylene.
Water Absorption. Polypropylene is highly impermeable to water. In a 24-hour soak test, the material absorbs less than 0.01% of its weight in water. This makes polypropylene ideal for total immersion applications where the basket material underneath has to be protected from exposure to various chemicals.
Surface Hardness. The hardness of polypropylene is measured on the Rockwell R scale as 92&#;placing it on the high end of the softer materials measured on that scale. This means the material is semi-rigid. This makes it more likely to bend and flex with an impact.
Operating Temperature. The maximum recommended operating temperature for polypropylene is 180°F (82.2°C). Beyond this temperature, the performance values of the material may be compromised.
Melting Temperature. At 327°F (163.8°C), polypropylene will melt. This makes polypropylene unsuited to high-temperature applications of any kind.

What Are the Advantages & Disadvantages of Polypropylene?

Why You Should Use Polypropylene

Liquid Cleaning Processes

An ideal use case for polypropylene would be an aqueous parts washing process where the basket being coated would be submerged in non-oxidizing agents for prolonged periods of time.

In such an environment, the impermeability of polypropylene would allow it to completely protect the coated basket from the liquid cleaning solution. Additionally, so long as the internal temperatures in the wash do not exceed 180°F, the coating would most likely last for many uses.

Additionally, polypropylene is dense enough to make it nearly impervious to water. This makes it an ideal material for sealing custom wire baskets against liquids.

Parts Protection

Another reason to use polypropylene would be to protect delicate parts from getting scratched. While not quite as soft as some formulations of PVC, polypropylene is still a semi-soft material that will absorb impacts&#;helping minimize the risk of parts getting scratched during the agitation cycle of many aqueous-based cleaning processes. Since a polypropylene structure will absorb shock rather than redistribute it, a polymer-coated basket would be ideal for processing delicate parts such as glass tubes or crystal components.

When You Shouldn&#;t Use Polypropylene

Extreme Temperatures & Environments

Polypropylene is not recommended for any high-temperature processes because of its low melting point. The integrity of polypropylene structure is compromised in low temperatures as well. Below 20°C, polypropylene embrittles.

Additionally, any processes that use oxidizing acids, chlorinated hydrocarbons (such as trichloroethylene), and aromatic solvents should be avoided. Polypropylene swells rapidly in chlorinated and aromatic solvents.

Limited Impact Durability

Sharp, sudden impacts from other objects can cause damage to a polypropylene coating. So, if you&#;re considering a polypropylene coating, it&#;s important to examine your production process to see if there are any points where such impacts are likely to repeatedly occur.

Besides being susceptible to impacts and scratches, polypropylene has poor resistance to UV and its heat- aging stability can be adversely affected by contact with metals. Additionally, polypropylene has poor paint adhesion.

Is a polypropylene coating right for your custom wire basket or tray? To answer that question, it&#;s important to know about your process! Contact Marlin Steel to learn more about custom wire basket coatings or to get a custom basket quote with our recommendations!

Expert Instructors Share Key Lessons to Be Learned at ...

The Nonwovens Institute (NWI) is offering its popular Fiber and Filament Extrusion Fundamentals Short Course July 23-25 at the Centennial Campus of North Carolina State University in Raleigh. This course, presented in partnership with INDA, The Association of the Nonwoven Fabrics Industry, will be led by expert instructors, including Carl Wust, Ph.D., NWI Emeritus Member and formerly the manager of research and development for FiberVisions® Corporation; an Indorama Ventures Company, and Behnam Pourdeyhimi, Ph.D., professor and executive director of NWI at NC State University.

The Fiber and Filament Extrusion Fundamentals course is designed to provide attendees a firm understanding of the critical variables and process parameters required to optimize extrusion practices to enable nonwoven innovation. In addition to spunbond and meltblown nonwovens, the course will consider staple-fiber applications, the process for crimping and cutting fibers, and fiber finishes, highlighting the differences between filament extrusion and staple-fiber extrusion. The course is designed to be accessible and valuable to attendees who do not have prior hands-on knowledge in fiber extrusion, as well as those who have a strong foundational understanding of extrusion fundamentals.

The following article provides perspectives from Dr. Wust and Dr. Pourdeyhimi on the compelling points that will be covered during this course and why extrusion is such a key variable in the success (or failure) of many nonwoven products.

What can attendees expect to learn from the Fiber and Filament Extrusion Fundamentals Short Course?

Carl Wust, Ph.D., NWI Emeritus Member (formerly FiberVisions)

In nonwovens, we tend to focus on spunbond and meltblowing processes, but a lot of nonwovens are made by carded bonding, and major companies remain focused on making staple fiber today.

Contact us to discuss your requirements of pp staple fiber. Our experienced sales team can help you identify the options that best suit your needs.

My former company, FiberVisions, operates the world&#;s largest PP staple-fiber plant housed under one roof. The plant, which is located in Covington, Georgia, has a nameplate capacity of 110 million pounds per year. During its peak of production, the plant was producing staple fiber for one product targeted at carded thermal bonded cover stock for baby diapers. In the s, baby diaper companies started switching to spunbond for cover stock, so we had to find new applications. Today the Covington plant produces staple fiber for a variety of end-use products &#; none of which are cover stock &#; so we learned a lot over the years about how to optimize staple-fiber production to suit the needs of varied applications.

The versatility in blending of different fiber types and adding finishes is what I think sells staple fiber, and I will provide the Fiber and Filament Extrusion Fundamentals course attendees an understanding for how they can leverage this versatility to the benefit of nonwoven applications.

During the Fiber and Filament Extrusion Fundamentals course, I will share the key learnings I have gained throughout my career. I will walk the attendees through the fiber production process, explaining how a staple-fiber production works, how to process blends and other important factors to consider when spinning and processing staple fiber. I will show-and-tell with extruder screws and spinnerets and describe polymers and finishes. I will explain how to cut and crimp fiber, how to put finish on the fiber, and how to bale the fiber up and prepare it for shipment.

One of the important advantages of carded staple fiber is you have flexibility to make different types of fibers &#; such as trilobal fibers or hollow fibers &#; with relative ease. You can incorporate such capabilities as antimicrobial, ultraviolet protection and electrostatic charging. When producing sheath/core bicomponent fibers, you can adjust the sheath properties to enhance the bonding strength and loft of through-air bonded fabrics. Staple fiber also can lead to nonwovens that blend cotton, viscose, etc.

The versatility in blending different fiber types and adding finishes is what I think sells staple fiber, and I will provide the Fiber and Filament Extrusion Fundamentals course attendees an understanding for how they can leverage this versatility to the benefit of nonwoven applications.

Behnam Pourdeyhimi, Ph.D., Professor and Executive Director, NWI

When it comes to the extrusion process, you really need to understand the material, process, performance interactions as they relate to fiber and filament formation.

During the Fiber and Filament Extrusion Fundamentals course, I will explain different polymer characteristics and the requirements for different processes. Filament formation is very similar to what you would experience in a spunbond nonwoven application. Meltblown, on the other hand, is very different from spunbond or filament production. We will highlight the critical material characteristics that need to be considered to enable innovation around fiber and filament formation in different process scenarios.

Filament formation is very similar to what you would experience in a spunbond nonwoven application. Meltblown, on the other hand, is very different from spunbond or filament production. We will highlight the critical material characteristics that need to be considered to enable innovation around fiber and filament formation in different process scenarios.

During the course, I will explain how you can &#;tune&#; fibers to provide unique capabilities such as orientation, crystallinity, strength, uniformity and dyeability. I will answer the question, &#;For a given polymer, how do we control the process to achieve the desired characteristics?&#;

When you look at polypropylene (PP), polyester (PET) and polylactic acid (PLA), for example, these are very different materials. I will consider the unique characteristics of each and how the process should be controlled to enable the end product you are aiming to create. We will consider, for example, how we can enable materials like PLA to overcome challenges such as shrinkage and crystallinity so it can be employed in a wide variety of applications.

Nonwovens can be made up of fully drawn fibers (fibers have a high degree of orientation) or partially drawn (fibers are only partially oriented). The majority of products use fully drawn fibers, but moldable structures, for example, require partially oriented fibers to facilitate molding.

PP is a model material because it offers fast crystallization and has strong bonding characteristics to support partially or fully oriented structures without exhibiting shrinkage. PET and PLA, on the other hand, are slower to crystallize and they don&#;t bond well. When the PET and PLA fibers are partially oriented, they exhibit significant shrinkage, which is a challenge in applications such as moldable structures. However, there are additives and bicomponent options that can overcome such challenges. Some aspects of this will be covered in the class.

So, I think it is safe to say, those who attend the Fiber and Filament Extrusion Fundamentals course will leave with the knowledge to make significant improvements in a variety of nonwoven and filament production scenarios.

Are you interested in attending the July 23-25 Fiber and Filament Extrusion Fundamentals Short Course?

Dr. Wust received his Ph.D. in Polymer Engineering from the University of Tennessee in and joined Hercules Inc. in Wilmington, Delaware, where he initially worked on polypropylene resin developments for fibers, controlled permeability films, and even solid rocket propellants. Over the ensuing 40 years, Dr. Wust transferred to Covington, Georgia, where he is currently located, accepted positions of increasing responsibility, and made numerous contributions to the advancement of fiber and fabric technologies that have benefited our every-day lives. In , Dr. Wust retired as manager of research and development in the Americas at FiberVisions, an Indorama Ventures company.

Since the early s, Dr. Wust has been an active member of NWI. He has served on the Industrial Advisory Board Executive Committee, served on and, most recently, chaired the Strategic Scientific Advisory Board (SSAB) and led the Institute&#;s Materials Research Focus Group (RFG).

Dr. Wust has been a significant contributor to the content of training programs offered by NWI and INDA, The Association of The Nonwovens Industry, and mentors 4-6 Ph.D. candidates in the field of engineered textiles annually. He currently serves as an Emeritus Member at NWI and continues to support the mission of the Institute through participation on Research Focus Groups, student mentoring and as a training course instructor.

Dr. Pourdeyhimi joined North Carolina State University as a Research Associate immediately after completing his Ph.D. at the University of Leeds in . Soon, he left for other opportunities, Cornell (2 years), the University of Maryland (11 years) and Georgia Tech (4 years) before returning to NC State in the - academic year. Dr. Pourdeyhimi joined NC State at the rank of Full Professor and soon after received the Klopman Distinguished Professorship for his work in textile materials.

Early in his career, Dr. Pourdeyhimi focused on the development of tools for characterizing various materials including nonwovens, medical devices, composite materials, etc. For this body of work, he received the ASTM D-13 Dewitt Smith Medal. In particular, his work on image analysis won him the Fiber Society Distinguished Scientist Award in . He also was selected as the Fiber Society Lecturer where he traveled broadly to present his work to industry and academia. He later served as the vice president and then president of the Fiber Society.

Dr. Pourdeyhimi is best known for his contributions to nonwovens and establishment and the growth of nonwovens at NC State. Dr. Pourdeyhimi joined NC State in part to take on a leadership role in the Nonwovens Cooperative Research Center (NCRC). He was appointed as the director of NCRC in and he successfully led the transition of NCRC into what is now known as The Nonwovens Institute (NWI).

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