Have you ever wondered why toys can withstand hurling, bashing, and chewing? Or why can the cap on your shampoo bottle withstand the repeated opening and closing? This incredible toughness is most likely since both goods are polypropylene plastic.

Polypropylene (PP) is a thermoplastic that uses across the world. They use it in various applications, including machinery and equipment parts, plastic packaging, and fibers and textiles. Polypropylene is a semi-crystalline stiff thermoplastic that was initially polymerized in 1951 and is still widely utilized in residential and industrial applications today. They are now expecting the global demand for polypropylene to be over 45 metric tons, and it is growing at an exponential rate.

Brief History

Polypropylene was polymerized initially in 1951 by Paul Hogan and Robert Banks of Phillips Petroleum and later by Natta and Rehn of Italy and Germany. It rose to prominence quickly since commercial manufacturing began just three years after Italian scientist Professor Giulio Natta initially polymerized it.

In 1954, Natta developed and synthesized the first polypropylene resin in Spain, and the capacity of polypropylene to crystallize sparked great interest. By 1957, its popularity had skyrocketed, and massive commercial manufacturing had begun throughout Europe. It is now one of the most widely manufactured polymers on the planet.

What Is Polypropylene Used For

Polypropylene employs in various applications because of its stiffness and low cost. It is chemically resistant and weldable, making it excellent for the automotive sector, consumer products, the furniture market, and industrial applications such as bespoke wire baskets.

These are the typical uses and purposes of Polypropylene:

Packaging Application

Polypropylene’s structure and strength make it an inexpensive and suitable packaging material. It is utilized in various packaging applications and has mostly supplanted conventional materials such as cellophane, paper, and paper. It is also extensively used in the production of jars, pallets, bottles, hot beverage cups, yogurt containers, food packaging, etc.

Consumer Products

Polypropylene utilizes for various consumer goods—including housewares, transparent components, furniture, luggage, appliances, toys, etc.

• Houseware – namely rugs, carpets, and mats. Polypropylene fibers are highly durable, and the material’s colorfastness enables brilliant and robust carpets that withstand heavy use and maintain their colors fresh and vibrant for many years.
• Furniture – PP is used in many sorts of upholstery, and molded polypropylene is critical in indoor and outdoor furniture.
• Luggage – Polypropylene is an incredibly versatile material. Polypropylene may find in duffel bags, tote bags, backpacks, sports bags, and other items in its thin shape. In its stiff form, baggage secures your items securely and withstands severe handling and all of the beatings your bag can endure in an airport.
• Appliances and Household Items – PP is the material of choice for microwave food containers, plates, dishwasher pods, containers, and other kitchen products because of its resistance to oils, heat, solvents, germs, and mold. We use it to produce sauce bottles and jars, food containers, and parts and components for vacuum cleaners, washing machines, dishwashers, pressure cookers, and other appliances.

Fabrics and Fibers

Polypropylene is used in fiber and fabric applications such as raffia/slit-film, tape, strapping, continuous bulk filament, staple fibers, spun bond, and continuous filament.
Industrial Application

Polypropylene’s great tensile strength and resilience to high temperatures and chemicals make it perfect for chemical tanks, pipes, sheets, and Returnable Transport Packaging (RTP).

Medical Application

Due to its chemical and microbiological resistance, polypropylene utilizes in medical applications such as diagnostic devices, medical vials, Petri dishes, specimen bottles, intravenous bottles, food trays, pans, disposable syringes, and pill containers.

Automobile Application

Polypropylene utilizes in car parts because of its low cost, weldability, and mechanical qualities. You can usually find it in bumpers, battery boxes and trays, interior trim, fender liners, instrumentation panels, and door trims.

Sports and Fashion Industry

Knowing the benefits and qualities of polypropylene will help you understand why this material is the material of choice for the sports, clothes, and fashion sectors.

Polypropylene uses to construct outdoor equipment and accessories due to its resistance to sun, elements, wear, tear, bacteria, mold, and, notably, water.

Tote bags and cinch bags are two of the most common polypropylene applications in the sports and fashion industries. These bags are sturdy, strong, long-lasting, lightweight, reusable, and light. Furthermore, because polypropylene works well with durable colors, you may customize them with logos, images, monograms, prints, etc. Polypropylene bags, duffel bags, and drawstring backpacks are essential for dynamic individuals seeking individualized utilitarianism, comfort, affordability, and beauty.

Polypropylene is an excellent addition to sports apparel, undergarments, and equipment — we see it in cold-weather base layers for winter sports and warm-weather gear for summer activities since it keeps sweat away from the skin.

Do you have a pair of summer beach slippers? You are very likely to own a team made of polypropylene.

Aside from clothing and accessories – with the tote bag and cinch bag industries at the top of the list – current designers began to employ polypropylene for contemporary jewelry. All clothing, luggage, and jewelry share the material’s characteristics. They are long-lasting, adaptable, printable, resistant to fatigue and the weather, hypoallergenic, and trendy.

How to Produce Polypropylene

Propene chain-growth polymerization produces polypropylene.

The three industrial manufacturing techniques are gas-phase polymerization, bulk polymerization, and slurry polymerization. All cutting-edge methods employ either gas-phase or bulk reactor technologies.

The polymer produces heterogeneous catalyst particles in gas-phase and slurry reactors. In a fluidized bed reactor, propene transports over a bed containing a heterogeneous (solid) catalyst. They separate the produced polymer as a fine powder and then turned into pellets. The unreacted gas is recycled and reintroduced into the reactor.

To avoid polymer precipitation during bulk polymerization, liquid propene uses as a solvent. The polymerization occurs at temperatures ranging from 60 to 80 °C and pressures ranging from 30 to 40 atm to preserve the propene in a liquid form. Typically, they use loop reactors for bulk polymerization. Due to the polymer’s poor solubility in liquid propene, the bulk polymerization restricts 5% ethene as a comonomer.

Typically, they use C4–C6 alkanes (pentane, butane, or hexane) as inert diluents in slurry polymerization to sustain the developing polymer particles. They inject propene as a gas into the mixture.

The tacticity of PP, which is the orientation of the methyl groups (CH3) relative to the methyl groups in surrounding monomer units, has a considerable influence on its characteristics. The tacticity of polypropylene can control by using a proper catalyst.

Manufacturing Polypropylene

Polypropylene melting may accomplish by extrusion and molding. Extrusion processes that they usually use include the creation of melt-blown and spun-bond fibers into long rolls for eventual conversion into a variety of valuable items such as filters, face masks, wipes, and diapers.

Injection molding is the most systematic shaping process, and they utilize it for items such as cutlery, cups, caps, vials, kitchenware, containers, and automobile parts such as batteries. They also utilize the related processes of blow molding and injection-stretch blow molding, including extrusion and molding.

Because of the flexibility to design grades with precise molecular characteristics and additives during manufacturing, polypropylene has many end-use applications. Antistatic additives, for example, can be applied to polypropylene surfaces to assist them in resisting dust and filth. Many physical finishing procedures, such as machining, may also employ polypropylene. You can give surface treatments to polypropylene components to improve ink and paint adherence.

Expanded Polypropylene (EPP)

Expanded Polypropylene (EPP) manufactures in solid and melt states. They use melt processing with either chemical or physical blowing agents to make EPP. Because of its highly crystalline structure, PP does not expand in solid form. In this context, they devised two unique ways for PP growth. They discovered that by regulating its crystalline structure or combining it with other polymers, PP might enlarge to form EPP.

Biaxially Oriented Polypropylene (BOPP)

Biaxially oriented polypropylene refers to polypropylene film that has been stretched and extruded in both the machine direction and across the machine direction. The tenter technique and the tubular process are the two most common ways of making BOPP films. Biaxial orientation improves strength and clarity.

They use BOPP as a packaging material for fresh vegetables, snack foods, and confectionery. It is simple to coat, print, and laminate to provide the desired look and qualities as a packaging material. They often manufacture BOPP in huge rolls sliced into smaller rolls on packaging equipment using slitting machines.

They also use BOPP for stickers and labels, notably by commercial suppliers. Because it is non-reactive, it is ideal for usage in the pharmaceutical and food industries. It is one of the most widely used commercial polyolefin films. However, BOPP films come in a variety of thicknesses and widths. They are open and adaptable.

Recycling and Repairing Polypropylene

Polypropylene is a recyclable material with the resin identification code “5”.

However, you can recycle only around 1% of all polypropylene worldwide.

You can also use polypropylene to make many products since it is solid and resistant to most glues and solvents. Furthermore, there are very few glues particularly for attaching PP. Actual PP items that are not prone to excessive bending, on the other hand, can connect with two-part epoxy glue or hot-glue guns. Preparation is critical, and it is typically beneficial to roughen the surface using a file, emery paper, or other abrasive substance to offer more excellent adhesive anchoring.

Before gluing, it is also advisable to clean with mineral spirits. You can also use similar alcohol to eliminate any oils or other pollution. Some trial and error may be necessary. There are certain industrial glues for PP available. However, they can be challenging to obtain, especially in a retail store.

You can use a speed tip welding technique to melt PP. With speed welding, the plastic welder, which looks and functions similarly to a soldering iron, equips with a feed tube for the plastic weld rod. The speed tip warms the rod and the substrate while pressing the molten weld rod into position.

A bead of softened plastic inserts into the junction, fusing the pieces and weld rod. When fabricating or repairing using polypropylene, the melted rod combines with the semi-melted base material. A speed tip “gun” is a soldering iron with a broad, flat tip that you can use to melt the filler material and weld joint to form a connection.

Why Should You Use Polypropylene

Liquid Cleaning Methods

A good application case for polypropylene would be an aqueous components cleaning procedure where the container immerses in non-oxidizing substances for lengthy periods.

Polypropylene’s impermeability in such an atmosphere would allow it to shield the coated container from the liquid cleaning solution. Furthermore, as long as the internal temperatures in the wash do not exceed 180°F, the coating should survive several applications.

Furthermore, polypropylene is thick enough to be practically impenetrable to water. As a result, it is an excellent material for sealing bespoke wire baskets against liquids.

Spare Parts Protection

Another reason to use polypropylene is to shield sensitive parts from scratch. While not as soft as specific PVC formulations, polypropylene is a semi-soft polymer that absorbs impacts, reducing the danger of scratched components during the agitation cycle of many aqueous-based cleaning techniques. Because a polypropylene framework absorbs rather than redistributes shock, a polymer-coated container is suitable for processing fragile items like glass tubes or crystal components.

When You Should Not Use Polypropylene

Temperatures and Environments at Extremes

Because of its low melting point, polypropylene is not advisable for high-temperature procedures. The structural integrity of polypropylene jeopardizes at low temperatures. It embrittles below 20°C.

Furthermore, avoid chlorinated hydrocarbons (such as trichloroethylene), oxidizing acids, and aromatic solvents. In aromatic and chlorinated solvents, polypropylene expands fast.

Limited Impact Durability

Sharp, unexpected impacts from other items can damage polypropylene. So, if you are considering using polypropylene, you should assess your manufacturing process to determine whether there are any locations where such effects are likely to occur regularly.

Aside from being vulnerable to scratches and impacts, polypropylene has low UV resistance. Its heat-aging stability can also harm by contact with metals. Furthermore, it has weak paint adherence.
Polypropylene as a Material for Your Packaging Solutions

Overall, polypropylene is a fantastic material. It is also known as the “steel” of the plastic industry since you can customize it to best fit a specific function. It is an excellent material for many items because it possesses a unique combination of properties that no other material contains.

Contact one of our experts at Plastic Packaging Solutions if you are interested in acquiring material handling items such as custom corrugated plastic, bulk containers, core boxes, etc.