Polypropylene is a typical representative of synthetic polymers that, for many applications including adhesive joints, requires an increase in wettability and chemical surface reactivity. Plasma processing offers efficient methods for such surface modifications. A particular disadvantage of the plasma jets can be the small plasma area. Here, we present a cold atmospheric plasma radio-frequency slit jet developed with a width of 150 mm applied to polypropylene plasma treatment in Ar, Ar/O2 and Ar/N2 We identified two main parameters influencing the tensile strength of adhesive joints mediated by epoxy adhesive DP 190, nitrogen content, and the amount of low molecular weight oxidized materials (LMWOMs). Nitrogen functional groups promoted adhesion between epoxy adhesive DP 190 and the PP by taking part in the curing process. LMWOMs formed a weak boundary layer, inhibiting adhesion by inducing a cohesive failure of the joint. A trade off between these two parameters determined the optimized conditions at which the strength of the adhesive joint increased 4.5 times. Higher adhesion strength was previously observed when using a translational plasma gliding arc plasma jet with higher plasma gas temperatures, resulting in better cross linking of polymer chains caused by local PP melting.

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In this research, rotomoulded samples of polyethylene (PE) were mechanically tested to find better applications. The mold was kept in an oven at 260 C with forced convection. Total fabrication time depended on peak internal air temperature (PIAT) used with 200, 220 and 240 C to confirm the fabrication conditions. The plasma treatment of PE and recycled carbon fiber (CF) was used for the improvement of properties. Maximum tensile strength (TS) of 23.1 MPa was observed in 10 wt% CF/PE composites. Scanning electron microscope (SEM) results revealed good mechanical interlocking with higher chemical interaction of carbon fiber of up to 10 wt% with plasma polyethylene leading to good mechanical properties in the composites. Flexural strength (FS) of 19.98-26.02 MPa in the properties was observed plasma treated in the PE with CF (3-10 wt%) combination. Agglomeration in the carbon fiber lowered flexural properties of 13, 15 wt% filler with both plasma and non-plasma PE. The CF (3-10 wt%) with plasma PE showed enhanced impact strength (IS) from 6.84 to 8.64 KJ/m 2 . Maximum TS, FS and IS were observed with peak internal air temperature (PIAT) of 200 C. Surface images showed even distribution of fiber and resin in the plasma treated matrix in 5 wt% CF combinations. The differential scanning calorimetry (DSC) results do not show fluctuations in the melting and crystallization temperatures of the samples after plasma treatment.