Solubility and Stability of polystyrene wastes in an intemperance recycling process



Polystyrene (PS) is one of the most used polymers in everyday life, and as it is thermoplastic, it can be melted and molded into many different plastic items. As a solution to the hardships in the disposal of such popular and widely used material, polystyrene recycling machines are proven to be advantageous and easier. 

PS is most commonly used in the form of expanded PS(EPS), a mixture of about 2% PS and 98% air. It’s a lightweight material in which the voids filled with trapped air gives EPS a low thermal conductivity. Due to its excellent impact strength and easy processing, it has a variety of applications in the food industry, electrical appliances, hardware, etc. To mitigate the problems due to the accumulation of waste and avoid incineration and landfilling as they cause a severe threat to the environment, the machine is a better way to recycle. The EPS recycling machine can solve the recycling problems, such as the area’s limitations to store scraps of EPS foam from the production process and transportation cost of the EPS foam scraps and wastes. Using an EPS recycling machine is an effective method as recycled EPS has broader applications than making items like outdoor furniture, roofing tiles, coat hangers, seedling containers, door and window frames, etc.

Other applications of Recycled EPS

● EPS mixed with concrete can be used to make prefabricated concrete blocks

● In combination with soil and compost, it helps to promote aeration. 

● On blending with plastic, it can be used to make decking and interior trim. 

● Manufacturing insulating concrete forms(ICF) and other structural panels 

● The incorporation of recycled EPS in construction is becoming extremely popular as it makes building practices more sustainable.

People might think that an EPS recycling machine could be expensive. But the cost of landfills is also increasing. Moreover, the recycling process doesn’t compromise the quality of EPS. To understand the recyclability of EPS and the effect of the recycling process on the solubility and stability of the recycled product, it is of great importance to understand the properties of EPS.


Dimensional Stability

EPS offers phenomenal dimensional stability, retaining the properties within a wide range of ambient factors. The maximum dimensional change of EPS foam is observed to be less than 2%. Similar to any other material, EPS also exhibits dimensional change under the thermal influence. We can assess the variations by finding the coefficient of thermal expansion which is not dependent on the density of the material and is placed in the values that oscillate in the range 5-7 x 10 -5 K -1. For example, an expanded polystyrene thermal insulation plate of 2 meters long when subjected to a rise of 20 ° C will show a variation in its length from 2 to 2.8 mm.

Stability against temperature

The effect of temperature on the dimensional changes is discussed above. In addition to that thermal action can also bring variations or alterations to EPS material. The temperature range in which EPS can be used safely without its affected properties has no limitation at the lower end (except dimensional variations by contraction). With respect to the upper end, the use temperature limit is around 100 ° C for short-lived actions and about 80 ° C for continuous actions and with the material subject to a load of 20 kPa.


Aqueous solutions of salts and alkalis and water do not affect expanded polystyrene. Expanded polystyrene is not hygroscopic, unlike other materials in the insulation and packaging sector. Even by completely immersing the material in water, absorption levels are minimal, with values ranging from 1% to 3% by volume (immersion test after 28 days). However, EPS is readily attacked by organic solvents.

Several researchers have performed various studies to test the properties of recycled EPS and made comparative studies too. In many of the studies, they have observed that the recycling process done through an EPS recycling machine has not altered the properties of EPS much. 

Mechanical Strength

Studies performed on mechanical characterization show that recycled EPS has a higher tensile strength than raw PS (32.57 and 30.42 MPa, respectively), and results concerning the strain at break are very similar. This allows recycled EPS to be used in the same applications as raw PS. The mechanical properties of recycled EPS (elongation at break and tensile strength) are better than those of the basic PS.

Melt Flow Index

The MFI test result for recycled EPS was 11.3 g/10 min and for raw polystyrene. STYRONTM 678E was 10 g/10 min – very similar extrusion rate values that are adequate for the injection molding process. The processability of material plays an essential role in determining its use at an industrial level. Thus, the melt flow index test is used to determine the best way to process a polymer.

Test on Degradation

Studies were also performed to determine the Degradation of the Recycled EPS. With recycled materials, before any analysis, it is of great importance to establish the existing levels of degradation, which result from the processing or conditions of use of such materials. Considering all these factors, studies are conducted to analyze the level of degradation in recycled EPS using the FTIR technique. There were no significant differences between the EPS before and after recovery and between recycled EPS and raw PS. Also, it is essential to know that the additives used in the foaming process are not relevant in the recovery process.

In conclusion, recycling EPS will generate wealth from waste. The recycling of EPS is a way of using EPS residue with clear economic benefits and without performance loss. Moreover, recycling is a step towards sustainable development, and we promote recycling polystyrene in UAE.