Mimosa cinerea natural fiber (NFR), ginger waste filler (WF) was incorporated into a Poly(lactic acid) (PLA) matrix to enhance tensile strength (TS), reduce thickness swelling (TSW) property in a corrosive state. The X-ray diffraction (XRD) of WF revealed a 110 plane at 15.8° and a 200 plane at 22.6°, the Fourier-transform infrared spectroscopy (FTIR) identified peaks at 1085 cm ^− 1 and 1520 cm ^− 1 , confirming high cellulose content in treated WF. In the compression moulded PLA composites, TS increased from 47.55 to 55.71 MPa as NFR content rose from 15 to 25 wt% with a constant 5 wt% WF. Improved hydrogen bonding among hydroxyl groups in NFR and WF contributed to this enhancement. The better combination of NFR (25 wt%), WF (5 wt%), NaOH Surface treatment (ST) (9 wt%), fiber length (LF) (1 cm), and 190 °C, attained TS of 58.4 MPa, 22.1% higher than neat PLA matrix. The WF addition reduced voids between NFR and PLA, lowering TSW in corrosive environments. Surface treatment up to 9 wt% produced a cellulose-rich, rough surface that improved PLA-NFR interaction, enhancing compatibility and increasing both TSW and TS. The better results were identified with NFR (15 wt%), WF (5 wt%), ST (3 wt%), LF (3 cm), and 190 °C for minimizing TSW in the hybrid PLA composite with 0.3% under corrosive conditions.

This paper describes a newly developed testing method for determination of the adhesivity of a film sintered from thermoplastic powder. This method is based on the modified EN 15337 standard. Application of this method enables an effective development of thermoplastic composites with enhanced adhesion between reinforcement and matrix and/or high-quality joints between plastics and dissimilar materials. The proposed method was successfully tested on a series of polyethylene powders treated in the oxygen atmosphere for 0–1200 s. Adhesion to metal and glass substrates in dependence on treatment conditions is described along with powder wettability and X-ray photoelectron spectroscopy analysis. The results show an increase in adhesion to metal by 580% and to glass by 1670% for the longest treatment time, compared to a nontreated powder. Sintering of treated powders revealed a strong influence of treatment time on the melting process. The XPS analysis confirmed the formation of new oxygen groups (C–O, C=O, O–C=O). The method reveals a specific behavior of powders based on treatment conditions, which is crucial for the optimization of plasma treatment for the improved adhesion, applicability of polymer powders, and a development of composite materials.

A composite sample with 18% flax fiber flyash (FF) exhibits increased tensile strength (TS) and greater load‐transfer efficiency of the reinforcement under corrosive conditions. Similarly, increasing the biowaste filler (BW) content from 2 to 6 wt% improves bonding between the reinforcement and the polylactic acid (PLA) matrix, resulting in better tensile properties. A high applied load of 15 N in the composite samples led to better contact with EN 31 steel, resulting in a higher wear rate. The 18FF/6BW sample exhibited better wear resistance, similar to that of the 18FF/6BW/5 steel (ST) combination in the corrosive environment. A sliding distance in the range of 500–1500 m demonstrated improved wear resistance, with values between 6.1 and 6.4 × 10 ⁻⁴ mm ³ /Nm, when utilizing a hybrid bio combination containing 5ST. The sliding speed at 1500 rpm resulted in greater interaction between the counter steel plate and the composite specimen, thereby increasing the wear rate. The hybrid combination with FF, ST, and BW has not been tried yet. The application of increased reinforcement at 18FF/6BW/15ST produced a coefficient of friction (CoF) reaching up to 0.43 in the hybrid sample. It can be observed that the 18FF/6BW and 18FF/6BW/5ST combinations have the lower corrosion rate (CR) (0.12 and 0.15 mpy) and better inhibition efficiency (IE) (34% and 30%) among all the combinations. The bio‐combination acted as a corrosion inhibitor, exhibiting improved corrosion properties.

Optimisation of the tensile strength of thermoplastic polymer-matrix composites remains a scientific as well as technological challenge for 3D printing technology due to the mass application of composite materials. Inadequate mechanical properties are due to the mismatch in the surface energies of the polymer and fillers. In this study, an additively manufactured composite was 3D-printed and tested. The composite consisted of a linear low-density polyethylene matrix filled with glass fibres. Composite filaments were extruded from neat and plasma-treated polymer powders. Plasma was sustained in oxygen at 100 Pa by a pulsed microwave discharge, and 250 g of polymer powder of average diameter 150 µm was placed into a dish and stirred during the plasma treatment. The O-atom density at the position of the dish containing polymer powder was about 2 × 10²¹ m⁻³, and the treatment time was varied up to 30 min. A gradual improvement in the composites’ tensile and flexural strength was observed at the plasma treatment time up to about 10 min, and the mechanical properties remained unchanged with prolonged treatment time. The tensile strength of composites prepared from plasma-treated polymer increased by one-third compared to those based on untreated powder. However, reinforcing the modified polyethylene with plasma-treated glass fibres did not result in further significant mechanical improvement compared to untreated fibres. In contrast, strength values doubled using glass fibres with silane sizing in combination with plasma-modified matrix. The results were explained by the increased surface energy of the polymer powder due to functionalisation with polar functional groups during plasma treatment.

Vojtech Novácek1, Petr Špatenka1, Tatana Vacková1,*, Zdenka Jeníková1, Syam Krishna2 and Bedrich Veselý3