Learn how to recycle HDPE at home to make your own bowls.
Learn how to recycle HDPE at home to make your own bowls.
Plastics are like people. Some of them have great potential and can exist in harmony with the world, while others rapidly accumulate as trash.
This post is all about my favorite synthetic material, high density polyethylene (HDPE), the most commonly recycled plastic in the world. In the second part of this post, Ill tell you how you can recycle HDPE at home to make food safe bowls and cutting boards. But first. . . .
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What separates HDPE from the garbage plastics?
Well, first and foremost HDPE items are more durable than those made from other plastics, and therefore last much longer. But not only that, items made from HDPE can be recycled many more times than those made from most other plastics. In fact, a recent study by ESE World demonstrated that virgin HDPE can be processed, shredded, and reconstituted over ten times, without any detriment in physical property, maintaining its usefulness for 100 to 200 years. This makes HDPE one of the most Eco-friendly of all plastics.
Sadly though, not all items made from HDPE go on to fulfill their 200 year tour of service. According to the EPAs most recent figures (which are from ), only about 31% of HDPE actually gets recycled, and that rate is declining. However, empty HDPE containers are a valuable commodity. South Asian countries may no longer be willing to take the rest of our heavily contaminated plastic, but everyone wants HDPE. Ninety percent of the HDPE that does make it into the recycling bin is reused right here, in the USA. So, if you put any plastics in your recycling bin, it should definitely be your emptied HDPE containers. Encourage companies to utilize HDPE over other types of plastics in their packaging. Colgate has the right idea, having spent considerable resources to make the very first recyclable toothpaste tube. No surprise: its made from HDPE.
HDPE is the ideal surface for food preparation and storage
HDPE will not leach PCB or other chemicals into foods. It is highly resistant to acids and bases and it can be heat sterilized between uses. Combined with its strength and abrasion resistance, its no surprise that HDPE has become the material of choice for most commercial food cutting surfaces.
Its so easy to recycle, you can do it at home
HDPE is a thermoplastic, meaning that it can be melted and reformed. It melts at approximately 355 degrees Fahrenheit, and as long as you dont burn it, it will not release any toxic fumes, so you can actually recycle HDPE at home. A cutting board is achievable with minimal tools. More complex shapes can be more of a challenge without a lathe and other shop tools.
Heres a general overview of how you can reuse this plentiful material to make useful items such as bowls and cutting boards, at home. I made these bowls from milk jugs and caps.
Getting the right plastics
As I mentioned before, HDPE can be heated to its melting point without releasing toxic fumes, but this is not the case for all plastics, so its important to not mix in any other types of plastics.
Best Practice: use only plastics with the #2 recyclable symbol or otherwise identified as HDPE. This well used watering can is clearly labeled.
Milk jugs and caps are usually made from HDPE. Other likely sources: detergent bottles, coffee containers, plastic tool boxes, garbage cans, cutting boards.
Preprocessing
You will definitely want to clean and remove contaminants such as paper labels and glue from your plastics. If those labels are on there really good, consider boiling them off. Or if you have plenty of plastic to work with, just cut the labeled parts away and toss them in the recycling (let the pros take care of them). Dont worry about ink marks (e.g. use by dates). These wont effect the melting or other properties enough to be of any concern.
Even after boiling these milk caps twice and scrubbing them in hot soapy water, a fourth of them retained residual glue. Do we really need a label to remind us to shake the contents?
Should the plastic be ground or left intact?
Professional recycling operations grind HDPE up into tiny pellets before melting it down. I dont actually know why they do this, but I know that increasing a materials surface area allows it to absorb energy more rapidly and therefore melt faster. From my own experience I also know that air bubbles are more likely to become trapped between large pieces and form voids in molded blocks of plastic .
The voids in this bowl were caused by air pockets, trapped between larger chunks of melting plastic. This can have an undesirable effect on the final product if you intend to further shape the HDPE bock with tools and cut into one of these cavities.
Shredding HDPE
Ive come up with several ways to grind HDPE. You may want to simply cut it up with a pair of scissors, or just melt it intact. Give it a try.
You would be surprised how much plastic you can run through a paper shredder before the engine burns out.
The blender didnt last as long. A poor quality plastic coupler broke. If only they had used HDPE
I replaced the paper shredders motor with a hand crank and built a hopper to feed HDPE into the shredder.
Combine different colors to make unique patterns
Beware of Look Alike Plastics
These look like HDPE but are actually Polypropylene (PP). It has a much higher melting point than HDPE, so you dont want to mix them up. They will be marked as #5 or simply PP.
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Preparing to Melting HDPE
As I mentioned before HDPE will melt at around 355 degrees Fahrenheit without releasing any toxic fumes When I started these projects I used a toaster oven in my workshop just in case it produced an objectionable odor. I now use the kitchen oven.
Things you will need before
Gloves
Gloves should be heat resistant and non-woven. Molten plastic will stick to a porous surface. These silicon oven gloves work great.
A mold
To get a smooth surface on your item, directly out of the oven, the HDPE will need to be pressed into a mold. Again, you want the least porous surface possible. Cake pans or stacking bowls work great.
Melting HDPE
Ive tried a few methods. The most straightforward means is to simply fill the mold with the shredded plastic and slide it into the oven. While that might seem like the easiest, most efficient method, Ive had less than optimal results. The plastic never seems to fully liquify. Rather, it softens and then fuses together once cooled. This is acceptable, but considerable physical pressure must be placed on the semi-molten plastic and throughout cooling to ensure no voids (air pockets) remain in the finished item.
- compressed between molds
- outer mold released
- inner mold released
Another method
As I mentioned, when I simply allowed the shredded HDPE to melt in the bowl I intended to use as a mold, it never fully liquefied, which made it very difficult to compress under the top mold. Air bubbles are also likely to become trapped, leaving an undesirable effect when the plastic has not fully melted. This can be resolved by first melting the plastic on a flat baking sheet, covered in parchment paper, prior to placing the plastic into your mold. You will definitely need the silicon gloves in this case. Also, Ive had problems with the parchment paper getting stuck in the molten plastic. Consider using a silicon baking sheet. I have not yet tested this, but I plan to soon.
The molten plastic can then be transferred to and pressed into a mold using silicon, heat resistant gloves. For best results, the mold should also be heated prior to the transfer. This must be done really fast. HDPE rapidly solidifies once removed from the heat. If you can just transfer the plastic from the sheet to the bowl, youre doing good. Then put it back in the oven and allow it to soften again before pressing it to conform the the bowls inner contour.
Embellishment and Finishing
Ideally, the bowls would come out of the molds ready to use, but mine typically need some machining, to remove flashing and to improve overall usability. Fortunately, HDPE is a highly machinable plastic, meaning its easily cut and shaped using tools. I use the same tools I use for my wood working, and much of the same procedures I use to make wood bowls.
- Removing flashing
- Shaping the lip
- Adding a slight curve to the base
- Further shaping
- Reducing the bowls thickness
- Polishing the exterior
- Polishing the exterior
- The Finished bowl
Thats about it, but the project isnt finished. I plan to continue to improve on these methods and post updates. My goal is to simplify the process so everyone can make use of this wonderful, and readily available resource. Virgin HDPE can give us hundreds of years of of reuse, so none of this precious plastic should ever end up in the land fill.
Efficient HDPE Pipe Shredders: Transforming Discarded ...
Efficient HDPE Pipe Shredders: Transforming Discarded HDPE Pipes into Reusable Resources
An HDPE(High-Density Polyethylene) pipe shredder is a specialized machine designed to shred or break down discarded or unused HDPE pipes into smaller pieces or granules. This shredding process facilitates recycling or repurposing the HDPE material for various applications.
Features of an HDPE Pipe Shredder
- Robust Cutting Mechanism: These shredders typically employ sharp blades or cutters specifically designed to slice through HDPE pipes efficiently.
- High Crushing Capacity: HDPE pipe shredders are equipped with powerful motors and robust structures to handle large volumes of pipes effectively.
- Durable Construction: They are built to withstand the tough demands of shredding HDPE pipes, ensuring long-term operation and reliability.
- Safety Measures: Modern shredders include safety features to prevent accidents and ensure operator safety during operation.
Common Types of HDPE Pipe Shredders
There are various types of HDPE pipe shredders, which can be divided into the following main types according to different processing needs and scale:
- Single-shaft Shredder: This type of shredder usually uses a single rotor and a rotatable blade to tear and crush HDPE pipes. They are suitable for processing small and medium-sized HDPE pipes, and the discharge material is fine.
- Dual-shaft Shredder: It has two rotors and double-sided blades, which can shred pipes more easily. It is suitable for processing HDPE pipes of different sizes or high strength. It has large output and larger discharge size than single-shaft , if there are no finer discharge requirements, the dual-shaft shredder is a very cost-effective HDPE pipe shredder.
- Four-shaft Shredder: HDPE pipe four-shaft shredder is capable of a variety of difficult crushing tasks. Compared with single-shaft or double-shaft crushers, it has stronger crushing capacity and higher working efficiency, and the discharge can control, but the equipment price is higher.
Applications of S
hredded
HDPE Pipe- Raw Material for Production: The shredded HDPE material can serve as raw material for various manufacturing processes, such as extrusion or injection molding, to produce new HDPE products.
- Alternative Fuel Production: Shredded HDPE pipes can be utilized as part of solid recovered fuel (SRF) to generate energy through incineration or other energy recovery methods.
- Composite Material Production: The shredded HDPE material might be used in composite material manufacturing, blending with other materials for specific applications.
HDPE pipe shredders play a crucial role in the recycling and repurposing of HDPE pipes, contributing to the reduction of waste and the conservation of resources. GEP ECOTECH has produced a variety of HDPE pipe shredders for plastic waste recycling, if you want to know more about HDPE pipe shredding and recycling, come and contact us!
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