In this study, the production of stereocomplex PLA formulations (sc-PLA) by compounding and subsequent injection moulding at different mould temperatures was investigated. Several selective nucleating agents were identified and compounded with different poly(L-lactide)/poly(D-lactide) (PLLA/PDLA) ratios on a co-rotating twin screw extruder. The effect of nucleating agents (NA) on the crystallisation behaviour of the compound was systematically investigated by DSC analysis. The crystallisation behaviour of NA-21 (aluminium complex of a phosphoric ester), also in combination with talc, under cooling rates of up to 70 K/min was analysed. The wide-angle X-ray diffraction (WAXD) results showed a complete stereocomplex (sc) crystal formation on all specimens containing NA-21 even at the highest cooling rates. The thermo-mechanical testing of sc-PLA shows a Young’s modulus of approx. 3 GPa, yield stress of 30–40 MPa, elongation of 1%, and a heat deflection temperature (HDT-B) up to 180 °C. Processing sc-PLA exclusively via the processing route of compounding and injection moulding will open new areas of application for PLA at higher temperatures.

Compounding is the final processing step for quality adjustment and control before recycled thermoplastic polymer material can be introduced into production processes. Motivated by the need for higher recyclate shares, the research question is which quality problems recycling compounders are encountered in practice, where they occur, and which mitigation options might be reasonable. Therefore, an online survey with 20 recycling compounders based in Germany was conducted asking about typical processing steps and processed materials, test procedures for quality assurance, quality problems, and possibilities for reducing quality problems. Results show that compounders mainly name impurities and contaminations of the input material as challenging and the reason for quality problems. The study shows that the problems are not dependent on the material input type. Quality problems occur along the entire secondary value chain, with companies manufacturing components themselves being particularly affected. The composition determination of the input materials helps to minimize quality problems.

Biopolymers such as Polylacticacid (PLA) by politicians and the press are often referred as the materials of the future. However, this overlooks the fact that the material properties of many biopolymers are not yet equal to those of conventional industrial polymers. For this reason, their use is currently limited to the packaging and medical sectors. Unmodified PLA has relatively low heat and impact resistance, which is insufficient for most technical applications. The aim of this work is to improve the characteristics of PLA by optimizing the crystallization properties through the addition of novel nucleating agents (twin-screw compounding). The assessment is carried out using DSC analysis and the resulting calculated thermodynamic parameters. Subsequently chosen compounds are selected for measuring mechanical properties. The methods used for measuring these properties are tensile tests, the Charpy impact test, and the measurement of the heat deflection temperature (HDT). The results show that sorbitol is the most effective nucleating agent for the nucleation of PLA 4032D, with regard to the optimization of the heat resistance and toughness of the material. However the best crystallization rates from the melt can only be achieved by the further addition of polyethylene glycol (PEG) as a plasticizer. The combined influence of sorbitol and PEG in PLA 4032D, can improve the impact properties by more than 500 % to a value of 131.3 kJ/m² (reference sample 21.8 kJ/m²) and the heat resistance by about 20 % to 65.9 °C (reference sample 54.0 °C).

In this paper two promising ways to improve the material characteristics of PLA and PHB-V are presented by showing their positive effects on mechanical, optical, and thermal properties. The optimization is achieved by increasing the crystallization from the melt of the polymer chains and the other by means of a reinforcement of the matrices by bio-based materials. In the case of crystallization specific nucleating agents and optimized process parameters promote optimized crystallization conditions and lead particularly in toughness to significant improvements. In addition to crystallization the introduction of cellulose-based reinforcing materials is also a good alternative to improve the ductility of a biopolymer matrix considerably. Due to their polar surface structure cellulose fibres are favouring a very good interaction to the also polar biopolymers. In addition, the polar surfaces of both materials results in very homogeneous dispersion within the compound.

In this paper a promising way to improve the material characteristics of virgin PLA for technical applications, e. g. profile extrusion, is described. Thereby PLA is combined with other biopolymers such as cellulose esters and different functional additives to create new biobased blend systems. To verify the improved properties of the new materials several mechanical (tensile test, Charpy impact test), thermal (heat deflection temperature) and dimension accuracy tests have been performed. Furthermore a case study shows that the developed PLA materials are suitable to be processed on standard profile extrusion equipment to produce profiles with a good surface geometrical accuracy and quality.