Where and how to use a PBT regrind

Recycled PBT is normally found in the form of post-industrial ground, especially from food production or from household appliances or machines with electrical components.

Its chemical structure and characteristics have a similarity to PET , as they are both partially crystalline thermoplastic materials but, in PBT, we find a faster crystallization time which puts it in an advantageous situation in injection molding compared to PET.

If we consider a basic PBT , therefore without added fillers, we have the following standard characteristics:

– Density: g/c3 1.30-1.32

– Modulus of elasticity: Mpa 2,500-2,800

– Elongation at yield: % 3.5-7

– Melting temperature: °C 220-225

– HDT deformation temperature: °C 50-65 (1.8 MPa

– Electrical rigidity: kV/mm 25-30

The use of PBT is normally aimed at injection moulding , using a temperature of the melt between 230 and 270 °C and of the mould, defined as ideal, around 110 °C. To join pieces molded with this material, ultrasonic welding is normally used or the temperature of a hot head tool or special glues based on reactive resins are used.

Since PBT is a product comparable to PET, let's see what characteristics differentiate it from this.

First of all, PBT has better toughness at low temperatures than PET, while its strength and rigidity are slightly lower.

If we talk about the flow and shrinkage characteristics, we can say that in PBT they are decidedly good, while from the point of view of the electrical insulation characteristics, the product offers excellent insulation, the characteristics of which are not significantly influenced in the presence of water absorption , high temperatures and frequencies.

The fields of use are normally those of valve components, roller or plain bearings, pump parts, household appliance parts, wheels, coffee machines and pods.

As regards the recycled product, it is very important that in the waste management phase, on board the machine, the product is collected in special containers, clean, which do not contain different plastics and isolated from other waste materials to avoid contamination.

The grinding of the waste trimmings or the unsuitable product, from an aesthetic point of view, must be done taking care to clean the mill carefully , so that there are no foreign plastic parts left inside which could pollute the PBT.

After bagging the ground material, it is recommended to keep it covered and use it after drying it, by passing it through a clean silo, to remove any remaining humidity. The ground PBT can be used both in direct and compound molding, in order to create customer-specific recipes.

These recipes may include increasing mass flow, flame retardant, increasing rigidity through fillers or reinforcing products, increasing resilience or increasing wear resistance.

Category: news - technical - plastic - recycling - PBT - milled