Melting temperature

Hi,I have built a compression machine…I would like to know something abouth the  temperatures you used. So, for the compression process, it is necesarry to melt the polymer for example to 260 C, or a lower temperature is enough?Repeat , it is a compression process, not an injection one.

Hello @kelemen

It really depends on the plastic you are working with

Try having a look at this topic :

Don’t hesitate to ask any question on specific plastic type; i work on compression machine as well, i could give you more info on what i have been experiencing

Peace !

@imuh thank you so much for your inputs it really help me a lot! by the way, by any chance do you have records on how long does the molding process took in each plastic type?

Thank you for the answers Nicolas!

So here are the temperature i “play” with; depending on the type of plastic.

I have to emphasize the fact that the information i here supply you is what i managed to regroup as intel and what experimenting made me learn

1. PET : I usually go around 150-180°C, you need to be very careful:
DO NOT go above 250°C because it will start releasing hydrocarbons & aldehyds. Also you want to be VERY careful with the PET you use; indeed, you have to be ABSOLUTELY sure it has NO water at all because it will simply brake the polymer bonds and your output will 100% time brake. Some even advise to preheat the PET at around 70-80°C to eliminate the persistant water

2. HDPE : I only went for milk bottles & bottle caps. i go for around 120°C. Milk bottles have a Black Carbon sheet between 2 HDPE sheets so the results is a bit yucky & not 100% HDPE… for bottle caps, it works VERY well !!!

DO NOT GO HIGHER THAN 200°C because of release of hydrocarbons, aldehyds,  ketone & volatile fatty acid

3. PVC : I do NOT work with PVC

4. LDPE : around 105°C; when your LDPE is melted (it reduces a tons so you need to do couple batchs for a compression), i reckon you should wrap it in the next batch so the first batch doesn’t burn from too long contact on the heat-conductant metal it is melting on.
DO NOT GO HIGHER THAN 200°C because of release of hydrocarbons, aldehyds,  ketone & volatile fatty acid


5. PP Haven’t tested yet, i simply do not have enough to start experimenting, but of what i have read :
DO NOT GO HIGHER THAN 200°C because of release of hydrocarbons, aldehyds,  ketone & volatile fatty acid


6. PS (only work with Cristal PS; not expanded PS): around  210°C. from the testing, i have experienced many different fume releases depending on the type of cristal PS used. As of temperature awareness
DO NOT GO HIGHER THAN 250°C because of release of hydrocarbons, aldehyds,  styrene and its oligomers.

Hello Nicolas!

My big problem is that I don’t really have time to make experiments(you know, my machine is a degree work :D) and I have to buy a kind of polymer granulate. My oven’s heating capacity is 250 C. If you have experience on the mealting temperatures, could you tell me something about it. What type of polymer whould you recommend and what temperature did you use to melt it?