Regrind & Recycling
Regrind
Thermoplastics have the ability to be remelted many times, unlike thermosets. However each time a plastic is remelted, it incurs some degradation of the molecular chain, and results in a loss of physical properties. The main properties lost include:
- Environmental stress resistance
- Impact strength
- Abrasion resistance
- Melt strength
- Melt viscosity
- Tensile strength at rupture
- Elongation at rupture
- Resistance to creep
- Resistance to low temperature brittleness
- Environmental stress cracking resistance
- Chemical resistance
- Thermal resistance
- Melt viscosity
- Tensile strength at rupture
- Elongation at rupture
- Resistance to creep
- Resistance to low temperature brittleness
- Environmental stress cracking resistance
- Chemical resistance
- Thermal resistance
Both the thermal cycle and the grinding to reuse the regrind cause degradation, especially to any stabilizers and anti-oxidants in the resin. Most resins have at least one thermal history when formed into pellets. Often the creation of masterbatches and compounds (colors, fillers, talcs, fibers,) creates a second step. The processed waste creates then a third step, and often is added up to 25% in molding, less in extrusion due to gel sensitivity. Blending regrind resin into resins that need drying to avoid hydrolysis during processing, can significantly affect physical properties (PA, PC, PET, PBT).
Tek-Mix can aid in increasing regrind use three ways without further deterioration of physical properties:
1. Tek-Mix can process additives and blends in a low temperature zone, reducing their degradation, and reducing quantity requires.
2. Tek-Mix can break up gels formed by materials of dissimilar melt temperature and molecular weight, by targeting higher molecular weight chains which have an effect disproportionate to their weight percent, on processing conditions.
3. Tek-Mix's use of extensional flow not only disperses particles, it also reduces the particle size, and it does so without the higher temperatures and shear rates normally used by other methods. Tek-Mix's lower temperatures and shear rates help avoid the molecular weight degradation which causes deterioration of physical properties.
Tek-MixTM - Extensional / Elongational Flow Mixing
The Next Step in Mixing & Blending
The Next Step in Mixing & Blending
