PP Injection Moulding

Inox Cast- Your PP Injection Molding Solution Specialist

Inox Cast has been manufacturing PP injection molding for more than 20 years today. We are distributing all kinds of molds by this method to different countries in the world. Together with our highly skilled and devoted engineers, we can custom mold designs with your specific requirements.

Our PP Injection molding offers cost-effectiveness, energy-saving, and higher efficiency operations. It has safe to use features to prevent work-related injuries. Plus, this PP injection molding is fully approved and certificated by TS 16949, CE, and ISO9001 standard inspections.

Inox Cast has the ability to supply standard designs for PP injection molding to our dear clients worldwide and can even create custom-made designs. In actual fact, you can discuss with us your specifications for the designs you desired for the PP injection molding process. Make your ideas come true with Inox Cast assistance.

The Polypropylene material (PP) is divided into 2 main types, copolymers, and homopolymers. Each of these categories certainly fits your applications. This is commonly referred to as “steel” in the field of plastic manufacturing since it can be customized and modified at the same time.

What are the different advantages of polypropylene?

• Polypropylene has a fairly slippery exterior
• Relatively expensive and readily available
• High resistance to absorbing moisture
• High flexural strength due to its semi-crystalline nature
• Owned better fatigue resistance
• Great chemical resistance
• Excellent electrical insulator

Inox Cast implements PP injection molding that is best applied on the packaging of consumer products and plastic parts for the automotive industry, etc. Inox Cast keeps developing more original solutions that provide customer satisfaction.

We also use a technically advanced production system and the latest CNC equipment. All of this equipment are first-class.

Inox Cast can provide you the solutions and services you desired to have a better and successful business. For more information about our company capabilities, contact us!

PP Injection Molding: The Ultimate Guide

In this guide, you will find all information you need about PP injection molding.

Whether you want to learn about injection molding temperature, techniques, benefits, or tips – everything you need is right here.

So, keep reading to learn more.

1. What Is PP Injection Molding?

This is the process of injecting molten or liquefied polypropylene into a plastic mould done by an injection molding machine.

PP injection molding

2. Properties Of Polypropylene For Injection Molding

Some of the main properties include:

Resistance To Chemicals

The diluted acids and bases don’t rapidly react with polypropylene, thus making it the perfect container of acids and bases, e.g. cleaning agents.

Flexibility And Toughness

Polypropylene is elastic on a particular scale of deflection but experiences deformation of plastic early on in the deformation process without breaking.

Fatigue Resistance

Polypropylene will still maintain or retain its shape after a lot of bending and flexing during the molding process of polypropylene.

Better Insulation Properties

It resists electricity transmission, and this is a handy electronic component.

Thermoplastic Heat Resistant

Polypropylene has a melting point of 130 degrees. Celsius; this is where the polypropylene melts, and it can be cooled and heated again.

Instead of burning down like others, polypropylene liquefies for it to be easily injection molded and then be recycled again.

3. Injection Molding Polypropylene Parts

Some of the most common parts include:

• Plastic Containers- shampoo bottles, water bottles, cap seals
• Medical Component- syringes, sharps disposal bin, medical tray.
• Outdoor Furniture- Plastic table and chairs
• Toys – lego
• Luggage- briefcases
• Electronic Housings – remove control, computers, televisions, and medical equipment.
• Household- molded closures, containers, drinkware flower pots, wire ties, air fresher unit
• Commercial product- mop heads and equipment housing.
• Construction- Containers for cements, insulators, and elevated panels of the floor.
• Food Service- Elevated temperature serving pans, bread trays, Foodservice products

4. Advantages of PP Injection Molding

Some of injection molding PP include:

Less Expensive

Maintaining polypropylene plastic generally will not cost you a lot of money; it is very affordable for you.

Moderate Strength And Stability

It is a robust and stable plastic that usually holds up against any general wear and tear, unlike the other.

Heat Insulator

Polypropylene has the property of insulating heat, making this very useful when maintaining food to be hot in storage.

Chemical Resistant

It doesn’t react with chemicals or bases even when in contact; it is utilized to store these chemicals inside.

High Efficiency

The process is speedy compared to other methods, and the production rate is even more efficient and cost-effective.

Design Complex Parts

Because of the property of flexibility of polypropylene, the injection molding process handles every complicated part and in uniform fabrication with accuracy.

Reduced Waste

Material polypropylene doesn’t burn when exposed to heat; instead, it liquefies; this property helps re-use other parts, thus reducing waste.

Ability To Simultaneously Use Multiple Types Of plastics.

It can combine polypropylene with other plastic resins to give out the best quality needed to produce the component.

Accuracy

Injection molding with propylene material gives out a complex design but is very accurate within the much-needed parameters of the component molded.

Short Time Production Cycle

Fast production cycles make the duration of components short and thus reach the market closed, meeting the demands.

Color Control

Injection Molding allows the collaboration of different colors to achieve the desired color effect needed for different types of products being fabricated.

5. PP Injection Molding Process

First, you have to come up with the design you like to be created, then design the mould so that you can start the injection molding process.

Clamping

Before injecting polypropylene inside the mold, you utilize the clamping unit first to securely close the two halves of clamp.

You then attach each half of the mould to injection molding gadget and allow one half to slide.

Then you utilize the hydraulically powered clamping unit to push the mould halves together giving enough pressure to keep the mould closed while you inject the material.

The time you need to close and clamp mould depends on size of the machine; bigger ones take more time.

Injection

Polypropylene matter is in form of pellets, pour inside the injection molding gadget and proceed to mould by unit of injection.

In the process, matter is liquefied by pressure and heat then you inject it to mould and build up pressure to hold molten.

Cooling

You maintain the molten polypropylene temperature in mould to ensure there is cooling as it penetrates the inside surfaces of mold.

Then it solidifies into shape of the mold, but when cooling component reduction occurs.

You correct this by allowing extra matter in to stage of injection in order to flow into mould to decrease the visible shrinkage.

PP injection molding

You cannot open the mould until the needed cooling period has finished or lapsed to perfect the desired part’s molding.

Ejection

After the component is solidified into mold shape, you eject it from mold using system of ejection that is attached on half of mold rear.

Open the mould with use of mechanism by applying force to eject the component out of mold.

You apply force when ejecting the component because shrinking occurs when cooling, and a component can adhere to mold.

Spray a mold release agent on the surfaces of mold before injection process to facilitate the ejection of component.

Post-processing

Following the process of molding injection, a component usually has some excess material attached to it; you need to trim and re-use material.

6. Types Of Molding PP Techniques

Depending on your production needs, you can choose any of the following:

Die Casting

Die casting is a process characterized by exerting force on melted plastic with use of elevated pressure into the cavity mold.

Die casting

Plastic Injection Molding

This is the process that involves melting pellets of plastic, and injecting at elevated force into   cavity for solidification.

plastic injection molding

Thin Wall Injection Molding PP

This is a unique type of injection molding that concentrates on volume production of plastic components that are slender and underweight.

thin wall injection molding

liquid silicone rubber injection molding

2k Injection Molding PP

Known as two-shot injection molding or two-color injection molding, it consists of two different plastics.

The two plastics or two different colors are molded into one end product using the injection molding method.

2K injection molding

Because of the chemical bond, the 2k injection molding process allows several functions to be integrated into an injection molded component.

Reaction Injection Molding PP

This is a process that involves low pressure and decreased temperature to mold various kinds of plastic parts examples; medical, industrial and automotive industries.

We utilize reaction injection molding most of the time for the molding of robust and lightweight components that are easily painted.

reaction injection molding

7. Limitations Of PP Injection Molding

Because of the property of increased melting point of the plastic, it is tough to evenly   maximize the molding potential of matter.

Polypropylene is very reactive when open to chlorinated solvents and airs out elevated risk to health of consumer.

It cannot be painted easily; thus challenging to rectify the color.

PP injection molding is simple to distort compared to different types of plastics materials.

PP injection isn’t helpful in increased working environment temperatures above 80 degrees the molded components get misalignment.

8. Tips For PP Injection Molding

You should consider these tips for successful injection molding process:

Ensure You Have The Right Molding Equipment

In order to have a successful injection molding you need the right equipment to get quality results.

Pre-dry   You Are Utilizing The Different Kind Of Polypropylene Resins

Other polystyrene polymers are usually wet and require drying before using them, if you are utilizing these kind dry first.

Utilize A Melting Temperature Scale Of 4000 Degree F To 500F.

Utilizing temperature more than 500 F leads to defects like warping, shrinking and burning.

When the temperature is lower than 400 F, it leads to defects like flow marks and low quality products.

Maintain An injection Pressure Scale Of   Around 800 To 1500 PSI

When you maintain the Injection pressure you assist in controlling certain defects that can occur during molding.

The pressure helps in filling 99% of the mold thus help in preventing problems like flashing and sticking.

Don’t Rush The Injection Process

Be ready for process of injection to use the intended period of time to complete one cycle in order to avoid shrinking and other defects problems.

Select Mold Temperature Of Around 50-80 F

Set a mould temperature carefully to assist in reducing stress and imperfection on surface.

Don’t Speed The Hold Time.

This assist to prevent defects like war-page and shrinking, allow the component to cool to the required temperature to produce quality results.

Utilize Less Back Pressure To Improve The Cycle Time

The required backpressure for polypropylene injection molding is on a scale of 50-100 Psi; this helps in improving the cycle time.

Adjust The Mold

Polypropylene possesses superb slippery properties; this feature helps if there is any minor sticking that has occurred to easily correct it.

Seek Intelligence Of Trained Professional

Always seek guidance of a trained industry person to help you with knowledge you need about the polypropylene injection molding industry.

9. Estimating Polypropylene Injection Molding Cost

Some factors determined the estimation of the cost of polypropylene like pats, size, complexity, material and anticipated quantities; all these determined the cost.

10. Conditions For PP Injection Molding

Before injection molding PP, you should ensure you meet the following consitions:

• Must be Dry
• The melting point of 20-280 degrees Celsius
• Mould temperature 20-80 degrees Celsius
• Polypropylene injection molding pressure as high as 180 mph

11. Common PP Injection Molding Defects

Some of the most common defects include:

Flow lines

These are line patterns that are in a slightly different color that shows up on the components because of physical path and also the cooling effect of molten plastic.

This is caused by the different flow speed the molten flows as it changes direction in contours and bends inside the mould.

Another cause to this is molten flowing through sections that has different wall thickness this causes molten to cool at different rates.

Prevent this by elevating injection speed and force to the required level, which enables the cavities be filled correctly in order to prevent flow lines.

Elevate temperature of molten plastic in order to ensure the molten doesn’t cool down insufficiently to create a problem.

Also round the corners and where thickness of wall usually changes to prevent unwanted changes in direction and rate of flow.

Sink Marks

These are small sink holes that occur in bulky parts of the injection molded component when there is shrinkage inside the surface of the product.

They are caused by not having enough cooling time for plastic molten to completely solidify and form the intended shape in mould.

Also, occur because of not having enough pressure inside the mold cavity and also the excess heat at the gate causes this.

Prevent this by decreasing the temperature in mold and also holding increasing pressure and the time for holding increased to ensure sufficient cooling.

Reduce the wall density of the dense part to help maintain quick solidification and assist in decreasing the occurrence of the sink marks.

Vacuum Voids

These are air pockets that are sandwiched between or within the surface of an injection molded component.

Caused by uneven solidification between the surface and the inner sections of the prototype when holding pressure is insufficiently to solidify part.

Prevent by utilizing a less dense plastic, so as to make sure that small amount of gas that is trapped can escape faster.

Elevate the holding pressure, time, and make sure that the molded compartments are precisely arranged.

Surface Delamination

It is a situation where the slender exterior surface layers emerge partly because of pollutant matter, the overlay emerge like coverings and can be scraped off.

They are caused by foreign materials that penetrate liquidized pp, separating from the fabricated component because the contaminants and PP cannot compact together.

Prevent this by pre-drying polypropylene before molding, increasing mould temperature, and smoothing out sharp corners to prevent quick alteration in the molten flow.

Concentrate more on the mechanism of ejection inside the mold to decrease the over-reliance on the mold discharge agents.

Weld Lines

It’s more like a plane that emerges on the component where molten pp comes together to meet one another as they streamlined from two diverse mold parts.

Caused by the insufficient uniting of two stream fronts when there is half cooling of the liquefied pp.

Prevent this by raising the heat of the mold and increasing injection speed, then adjusting the plan for the streamlined model to be a one way flow.

You can always use a minor dense pp or another that has a lower liquefying temperature.

Short Shot

This is when molten PP doesn’t wholly invade the mold cavity following a part of the component having no pp.

Caused by inaccurate setting of shot resulting in polypropylene matter to inadequately load cavities and this results in a mini-shot

Choose a less thick polypropylene with increased stream; this polypropylene occupies the furthest to get to cavities to help prevent this.

You can also increase mould temperature to increase flowability and design mould so that gas is not trapped within the mould.

Increase matter supply inside the molding gadget or utilize a higher material feed device to prevent this defect.

Warping

This deformation comes about when non-uniformity shrinkage occurs in various parts of the molded component twisted and bumpy.

Caused by the uneven solidification of mould matter, diverse solidification rates in other parts cause the polypropylene to solidify unevenly, creating internal stress.

To prevent this, ensure solidification period is adequately long, and it is unhurried to prevent the fabrication of leftovers strain from being confined.

Plot the mould with even wall density that liquefied polypropylene streamlines in one direction and choose plastics matter that doesn’t shrink and also deform.

Burn Marks

These are stains that emerge on the exterior surfaces of the injection molded components.

They are caused by the erosion of the polypropylene matter because of excess torridity or by injection velocity being very fast.

It is caused by increased heating of air that is trapped, it touches the exterior surface of the molded component.

Prevent by reducing the injection velocity, optimizing the use of venting for gas and degasifying thus minimizing mould and melting heat.

Jetting

Known as a liquefied paste that falls to cling on the mould exterior because of injection velocity.

Caused when melting heat is very minimal and the consistency of liquefied polypropylene becomes too elevated, thus elevating resistance of stream.

Prevent this by elevating the mounding and melting heat and elevate the extent of the opening so that injection velocity becomes sluggish.

Flash

When liquefied polypropylene evade from the mold cavity, the common pathway for escaping is through the ejector pin emplacement.

Caused when mold is not fastened securely in unison with sufficient pressure, which allows the liquefied molten to exude through

Prevent this by elevating the clamp pressure to make sure that the mold components stays closed during injection.

Ensure that the mould is adequately maintained and cleaned.

Related Resources:

Injection Mold Tooling

Injection Molding Process

Polymer Injection Molding

For all your PP injection molding needs, contact INOX now.