In this study, we investigated the physical, mechanical, and thermal properties of polypropylene/old corrugated container fibers and polypropylene/poplar fiber composites, which were treated with 1, 2, 3, and 4 wt% of hexamethylenediisocyanate coupling agent. Compounding was conducted by a counter-rotating twin-screw extruder, and samples for measurements of tensile, flexural, and impact properties were prepared by an injection molding machine. Thermal properties of composite samples were studied by thermogravimetric analysis and differential scanning calorimetry techniques. Thermal stability and crystallinity content of the prepared composites were determined, as well. The obtained results showed that the addition of coupling agent increased the thermal properties of the composites. Mechanical resulting indicated that by the addition of coupling agent, there was improvement in the tensile and flexural properties but there was declination in impact properties. Scanning electron micrographs taken from failed surfaces of the composite samples showed that the addition of coupling agents resulted in the improvement of bonding between wood fibers and polymer matrix at their interface.

The effects of a silane coupling agent such as (N‐(n‐butyl)−3‐aminopropyltrimethoxy silane) on old corrugated container (OCC) fibers, as a recyclable material, were studied on the ultimate strength of the prepared OCC fibers/high density polyethylene composites. Raw materials were mixed in a counter‐rotating twin‐screw extruder and injection molding machine was used to make samples. Various characterization methods, based on ASTM standard, were conducted to evaluate physical properties (water absorption and thickness swelling) and mechanical behavior (tensile, flexural, impact, hardness, and elongation‐at‐break) of the composites. Also, the thermal properties of the specimens were recorded by differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). Finally the results of the treated samples were compared with the non‐treated and pure polymer specimens. The obtained results showed that increasing coupling agents by a maximum of 2 wt% enhanced mechanical behavior (including flexural and tensile strengths), thermal stability, and increased crystallinity of the composites. Moreover, water absorption and thickness swelling of composite materials declined. Morphological studies by scanning electron microscopy methods (SEM) indicated that fiber pull‐out decreased in treated samples and coupling agent facilitated strong adhesion in fiber/polymer interface. The highest flexural strength and modulus were obtained in composites with 2 wt% silane coupling agent and 30 wt% OCC fibers. POLYM. COMPOS., 39:2054–2064, 2018. © 2016 Society of Plastics Engineers

In this study, the effects of adding different coupling agents, e.g. maleic anhydride-grafted polyethylene (MAPE), silane (3-aminopropyltrimethoxy silane) (silane 1189) and isocyanate (hexamethylenediisocyanate) (HDI) on mechanical and morphological properties of composite samples of high density polyethylene/old corrugated container fibres (HDPE/OCC) were studied. The amounts of OCC fibre and coupling agents used were 30% and 2% of dry composite weight, respectively. Mixing of materials was carried out by a two-screw counter extruder and samples were prepared by injection moulding. In order to compare the results of the use of mixture coupling agents, their effects were studied independently, as well. Mechanical properties of prepared composite samples containing coupling agents were measured and the results were compared with those of pure high density polyethylene and those of composite samples without coupling agent. The measured mechanical properties showed that maximum values of tensile and flexural strengths and tensile and flexural modulus could only be obtained in composites containing a mixture of silane1189 and MAPE coupling agents. It was also observed that the Izod impact strength values of composites with coupling agents increased significantly. SEM micrographs of failure surfaces of samples showed that the best homogeneity of composites and bonding between OCC fibres and polymer matrix were obtained for the sample containing 1 wt.% silane and 1 wt.% MAPE.