In this study, the effects of chemical foaming agent and nanoclay on the physical, mechanical, and morphological properties of composites based on HDPE and WF were described. To meet this objective, the nanoclay, HDPE and the coupling agent were compounded and granulated and mixed with WF and blowing agent in a twin-screw extruder. Consequently, the foaming process was completed in the injection stage. The amount of WF was fixed at 50 wt% for all samples. For nanoclay (organomodified montmorillonite) and CBA (azodicarbonamide), different levels of 0, 2, 4, 6 per hundred resins (phr) and 0, 0.5, 1, 1.5 phr were considered, respectively. Results indicate that the cell size and the average cell density of samples increased with the increase in the chemical foaming agent content. However, on addition of nanoclay to HDPE/WF composite foams, the cell size was decreased and their cell density increased. SEM confirmed that the chemical foaming agent and nanoclay contents had significant influence on density reduction of foamed composites. Finally, by increase in the chemical foaming agent content, the tensile modulus decreased and the water absorption and thickness swelling of HDPE/WF nanocomposite increased. The nanoclay dispersion quality is quite an important factor for the physical and mechanical properties of both foamed and unfoamed wood plastic nanocomposites. It was found that the optimal condition was attained by incorporating 0.5 phr foaming agent and 4 phr nanoclay in composite formulation.

Cationic rosin has many uses in papermaking; however, its performance as an internal sizing agent differs depending on the circumstance, especially in the recycling of pulps. In this study, a comprehensive laboratory approach was used to investigate the process variables affecting the cationic rosin application in the paper recycling process. In this respect, four levels of alum (0.5, 1.0, 1.5, and 2.0%) and four levels of cationic rosin (0.5, 1.0, 1.5, and 2.0%) were considered to find the best alum/cationic rosin combination in acidic conditions (pH 5). After considering all aspects of the paper, such as the mechanical properties (tensile, burst, and tear indices), wet resistance (Cobb test and dynamic contact angle test), and chemical usage (economically and environmentally-friendly procedures), the 1.0% alum and 0.5% cationic rosin levels were selected for optimum performance. This research also showed that the combined effect of alum with cationic rosin was favorable. Moreover, the sequence of alum and cationic rosin addition, which is a challenge in paper mills, also should be considered. The results indicated that the addition of cationic rosin after alum obtained the best mechanical and wet resistance results. In addition, the results showed that both acidic and neutral pH were acceptable in this sizing process.

Date Palm Fiber (DPF) is one of the most available natural fibers in the Middle East, especially in Iran and the Persian Gulf region. This research provides a new insight into DPF, with consideration of morphological, chemical characteristics, and bulk density, as well as morphological and mechanical properties of DPF/HDPE wood plastic composite. There are three parts of date palm that are used for producing fiber, the trunk, rachis, and petiole. Results indicated that there is significant difference between trunk and petiole on fiber length but rachis has no significant differences relative to the other parts. The aspect ratios have significant differences among of three parts, with the highest and lowest values measured for the petiole and trunk, respectively. The chemical composition of various parts of the date palm tree differed significantly; with the highest amounts of cellulose and lignin content belong to rachis. Bulk density was measured for three parts of date palm, and the lowest amount was 0.082 g/cm3. The highest strengths were achieved in composites with 30 and 40% fiber content, depended on which original parts of the tree were used.