The influence of spinning temperature on ultrahigh-molecular-weight polyethylene/high-density polyethylene as-spun blend filaments and the influence of drawing temperature on ultrahigh-molecular-weight polyethylene/high-density polyethylene-blend fibers were investigated. The results showed that the optimum spinning and hot-drawing temperatures were 310℃ and 85℃, respectively, and blending with high-density polyethylene improved the orienting ability of the molecular chains and the crystallization ability. The blend filaments spun at 310℃ had the best molecular chain orientation, crystallinity and crystal orientation of the filaments examined; both lower and higher spinning temperatures were detrimental to the crystal structure growth of the as-spun blend filaments. The optimum drawing temperature of the blend fibers was 85℃, which resulted in blend fibers with the best molecular chain orientation, crystallization, and crystal orientation as well as the thinnest grains of the fibers examined. The highest tensile strength and initial modulus were 1204 MPa and 20.4 GPa, respectively; these high values can be attributed to the fibrillar structure, which consisted of extended molecular chains and thin grains. The results in this paper can help disclose the effect mechanism of formation temperature on the melt spinning method used to produce high-strength ultrahigh-molecular-weight polyethylene fibers.

Modified ultra-high-molecular-weight polyethylene (UHMWPE) with calcium stearate (CS) and polyethylene wax (PEW) is a feasible method to improve the fluidity of materials because of the tense entanglement network formed by the extremely long molecular chains of UHMWPE, and a modified UHMWPE sheet was fabricated by compression molding technology. A Fourier-transform infrared spectroscopy test found that a new chemical bond was generated at 1097 cm⁻¹ in the materials. Besides, further tests on the thermal, thermomechanical, mechanical, and shape memory properties of the samples were also conducted, which indicates that all properties are affected by the dimension and distribution of crystal regions. Moreover, the experimental results indicate that the addition of PEW and CS can effectively improve the mechanical properties. Additionally, the best comprehensive performance of the samples was obtained at the PEW content of 5 wt % and the CS content of 1 wt %. In addition, the effect of temperature on the shape memory properties of the samples was investigated, and the results indicate that the shape fixity ratio (R_f) and the shape recovery ratio (R_r) can reach 100% at 115 °C and 79% at 100 °C, respectively, which can contribute to the development of UHMWPE-based shape memory polymers.

Pultrusion of thermoplastic composites has been the hotspot of manufacturing high-performance thermoplastic composites in recent years. The optimization of process parameters in the pultrusion usually needed repeated attempts, which wasted lots of manpower and material resources. A numerical simulation method can accelerate the optimization of process parameters. In this work, the impregnation process of reactive injection pultrusion for glass fiber reinforced nylon 6 (GF/PA6) composites was modeled and numerically simulated by a finite element/controlled volume (Fe/CV) method. Based on Darcy’s law, the impregnation process can be regarded as the two-phase flow (liquid resin and air) in porous media (undirectional glass fibers). The distribution of resin flow during the impregnation was explored. The effects of pulling rate and injection pressure on the impregnation time and resin reflux distance were analyzed, and the appropriate range of relevant process parameters was determined. The results showed that increasing the pulling rate can significantly control the reflux distance of resin in the impregnation mold and shorten the impregnation time, but too high a pulling rate would increase the impregnation time. Increasing the injection pressure can greatly shorten the resin impregnation time, but it would significantly increase the resin reflux distance. This work can effectively guide the subsequent optimization of process parameters of reactive injection pultrusion for GF/PA6 composites.

The polypropylene (PP)/wood flour (WF) composites were prepared using a co-rotating twin-screw extruder followed by a single-screw extruder foaming system in this paper. Polymers, such as polyolefin elastomer (POE), high-density polyethylene (HDPE) or microcrystalline wax, were blended with PP in the preparation of composites to improve the melt strength. And a cavity transfer mixer was introduced to increase the distribution uniformity of components in composites. Meanwhile, the effect of the polymer blends on the microstructure and mechanical properties of samples was investigated. The experimental results show that the addition of POE and HDPE resulted in the second melting peak in the differential scanning calorimeter (DSC) curves and a great decrease in the cell size was caused by the added POE. However, due to the velocity difference of composites in the die, the shape of bubbles gradually became irregular. Moreover, the impact strength of samples significantly increased by 85% for the added POE and the apparent density decreased by 6.7%. And the minimum Vicat softening temperature of 133.7 °C was obtained when the mass ratio of HDPE to PP was 4/6.

All-wood biocomposites were prepared with an efficient method. The ionic liquid of 1-butyl-3-methylimidazolium chloride (BMIMCl) was used to impregnate manchurian ash (MA) before hot-pressing, and the all-wood biocomposites were prepared by controllable dissolving and regenerating the cellulose in MA. The Fourier transform infrared analysis suggested that all the components of MA remained unchanged during the preparation. X-ray diffraction, thermogravimetric and scanning electron microscope analysis were carried out to study the process parameters of hot-pressing pressure and time on the crystallinity, thermal properties and microstructure of the all-wood biocomposites. The tensile strength of the prepared all-wood biocomposites reached its highest at 212.6 MPa and was increased by 239% compared with that of the original MA sample. The thermogravimetric analysis indicated that as the thermo-stability of the all-wood biocomposites increased, the mass of the residual carbon increased from 19.7% to 22.7% under a hot-pressing pressure of 10 MPa. This work provides a simple and promising pathway for the industrial application of high-performance and environmentally friendly all-wood biocomposites.