Co-authors​ :

 ZICĀNS Jānis (LATVIA), Agnese ĀBELE , Zanda IESALNIECE , Ivan BOČKOVS , Rita BĒRZIŅA (LATVIA), Ritvars BĒRZIŅŠ , Remo MERIJS-MERI (LATVIA) 

Overarching aim of the current research is promotion of resource saving approach towards sustainable development by demonstrating applicability of waste flows’ combination for development of polymer composites. In particular, the research is devoted to utilization of post-consumer polypropylene-polyethylene blend (PPPE) for development of sustainable polymer composites with agricultural residues. On this score, post-consumer PP contributes to the largest part of plastic waste (17%), generating generally from food and non-food packaging, household appliances and automotive sectors. On the other hand, rapeseed covered more than 60% of the EU oilseeds production in 2017 and its amount has been stabilized around 20 Mt. Resultantly, large amounts of agricultural residue from rapeseed cultivation is produced annually. However, it is well known that development and application of natural fibers reinforced polymer composites is limited due to low compatibility between non-polar polymer matrix and polar lignocellulosic reinforcement. Although, maleic anhydride grafted compatibilizers (MAH) had shown commercial acceptance in improving exploitation properties of polymer composites with natural fibers, search for equally efficient biobased compatibilizer alternatives still are in the focus of research. Consequently, in the current research two biobased compatibilizers obtained from stearoyl chloride modified tannic acid (SCTA) or catechin hydrate (SCCA) were synthesized and used for compatibilisation of rapeseed straw microfibers (RS) reinforced post-consumer PPPE composites, intended for injection molding purposes. It was hypothesized that SCTA and SCCA both well be capable to improve also thermal resistance of the investigated PPPE composites. The amount of mercerized RS in the composites was changed in the range from 10 to 40 wt.%. The said PPPE composites have been obtained by melt blending in the presence of conventional thermal stabilizer; it structural, rheological, mechanical and thermal properties have been investigated by using scanning electron microscopy, differential scanning calorimetry, rotational rheometry, tensile and flexural testing, impact testing, thermogravimetric analysis and oxidation induction time test. It has been demonstrated that in the presence of either SCTA or SCCA oxidation induction time of the investigated PPPE composites considerably increased, even exceeding the value achieved by the composites with MAH and conventional thermal stabilizer. Besides it, the composites made with SCTA and SCCA showed smaller fluctuations in mechanical properties before and after accelerated aging tests. Thus SCTA and SCCA both may be suggested as potential modifiers for PPPE based composites with lignocellulosic fibers.