Bio-based thermoplastics are produced from renewable organic materials and can be recycled after use. Their resilience can be improved by blending bio-based thermoplastics with other thermoplastics. However, the interface between the materials in these blends sometimes requires enhancement to achieve optimal properties. A team from the Eindhoven University of Technology in the Netherlands has now investigated at BESSY II how a new process enables thermoplastic blends with a high interfacial strength to be made from two base materials: Images taken at the new nano station of the IRIS beamline showed that nanocrystalline layers form during the process, which increase material performance.
Bio-based thermoplastics are considered environmentally friendly, as they are sourced from non-petroleum-based raw materials and can be recycled just like standard thermoplastics. A thermoplastic base material is Polylactic acid (PLA), which can be produced from sugar cane or corn. Researchers around the world are working to optimise the properties of PLA-based plastics, for example by mixing them with other thermoplastic base materials. However, this is a real challenge.
A new process for better blends
Now, a team from the TU Eindhoven led by Prof. Ruth Cardinaels is showing how PLA can be successfully mixed with another thermoplastic. They developed a process in which certain PLA-based copolymers (e.g. SAD) are formed during production, which facilitate the mixing of the two raw materials by forming particularly stable (stereo)-crystalline layers at the interfaces between the different polymer phases (ICIC strategy).
Insights at the IRIS-Beamline
At BESSY II, they have now discovered which processes ensure that the mechanical properties of the mixed thermoplastic are significantly better. To do so, they examined pure 50% blends of the thermoplastics PLA and polyvinylidene fluoride (PVDF) as well as samples with the PLA-based copolymers at the IRIS beamline of BESSY II.
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Image: In nano-IR imaging, the layer structures of the pure PVDF/PLLA mixture (left) and with the SAD additive (right) are clearly distinguishable. The light and dark colours correspond to the PLLA and PVDF phases, respectively. When SAD is added, the domain sizes of the two phases are reduced.
Credit: TU Eindhoven/HZB