Zheng-Ian Lin

Preparation and Compatibility Evaluation of Polypropylene/High Density Polyethylene Polyblends

This study proposes melt-blending polypropylene (PP) and high density polyethylene (HDPE) that have a similar melt flow index (MFI) to form PP/HDPE polyblends. The influence of the content of HDPE on the properties and compatibility of polyblends is examined by using a tensile test, flexural test, Izod impact test, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and X-ray diffraction (XRD). The SEM results show that PP and HDPE are incompatible polymers with PP being a continuous phase and HDPE being a dispersed phase. The FTIR results show that the combination of HDPE does not influence the chemical structure of PP, indicating that the polyblends are made of a physical blending. The DSC and XRD results show that PP and HDPE are not compatible, and the combination of HDPE is not correlated with the crystalline structure and stability of PP. The PLM results show that the combination of HDPE causes stacking and incompatibility between HDPE and PP spherulites, and PP thus has incomplete spherulite morphology and a smaller spherulite size. However, according to mechanical property test results, the combination of HDPE improves the impact strength of PP.

Polypropylene/Short Glass Fibers Composites: Effects of Coupling Agents on Mechanical Properties, Thermal Behaviors, and Morphology

This study uses the melt compounding method to produce polypropylene (PP)/short glass fibers (SGF) composites. PP serves as matrix while SGF serves as reinforcement. Two coupling agents, maleic anhydride grafted polypropylene, (PP-g-MA) and maleic anhydride grafted styrene-ethylene-butylene-styrene block copolymer (SEBS-g-MA) are incorporated in the PP/SGF composites during the compounding process, in order to improve the interfacial adhesion and create diverse desired properties of the composites. According to the mechanical property evaluations, increasing PP-g-MA as a coupling agent provides the composites with higher tensile, flexural, and impact properties. In contrast, increasing SEBS-g-MA as a coupling agent provides the composites with decreasing tensile and flexural strengths, but also increasing impact strength. The DSC results indicate that using either PP-g-MA or SEBS-g-MA as the coupling agent increases the crystallization temperature. However, the melting temperature of PP barely changes. The spherulitic morphology results show that PP has a smaller spherulite size when it is processed with PP-g-MA or SEBS-g-MA as the coupling agent. The SEM results indicate that SGF is evenly distributed in PP matrices, but there are distinct voids between these two materials, indicating a poor interfacial adhesion. After PP-g-MA or SEBS-g-MA is incorporated, SGF can be encapsulated by PP, and the voids between them are fewer and indistinctive. This indicates that the coupling agents can effectively improve the interfacial compatibility between PP and SGF, and as a result improves the diverse properties of PP/SGF composites.

Far-infrared emissive polypropylene/wood flour wood plastic composites: Manufacturing technique and property evaluations

This study melt-blends polypropylene (PP), wood flour (WF), and far-infrared masterbatches into PP/WF wood plastic composites with far-infrared emissivity. During the process, maleic anhydride-grafted polypropylene (PP-g-MA) is added as the coupling agent between PP and WF. Mechanical property tests, scanning electron microscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), polarized light microscopy (PLM), and far-infrared emissivity are undertaken to evaluate various properties of the PP/WF wood plastic composites. The test results show that regardless of the WF content, mechanical properties of the composites remain at certain levels. The combination of 3 wt% PP-g-MA increases the interfacial adhesion between WF and PP, which in turn effectively increases the tensile strength by 20% and increases the flexural strength by 35%. The PP/WF wood plastic composites containing 4 phr (parts per hundreds of resin) of far-infrared masterbatches is 0.86 ɛ, which reaches the standard of good health care. The test results of XRD, DSC, and PLM show that the combination of both WF and far-infrared masterbatches helps the heterogeneous nucleating in PP, and increases the crystallization temperature of PP, but does not influence the crystalline structure of PP.

Nonwoven fabric/spacer fabric/polyurethane foam composites: Physical and mechanical evaluations

In the first stage, polyethylene terephthalate (PET) fibers and Kevlar fibers are combined at a blending ratio of 80/ 20 wt% in order to form PET/Kevlar nonwoven fabrics. Two pieces of PET/Kevlar nonwoven fabrics that enclose a carbonfiber (CF) interlayer are then needle punched in order to form PET/Kevlar/CF (PKC) composites. In the second stage, the sandwiches compose PKC composites as the top and the bottom layers, as well as an interlayer that is composed of a spacer fabric and polyurethane (PU) foam. PU foams have different densities of 200, 210, 220, 230, and 240 kg/m3. These resulting nonwoven fabric/spacer fabric/PU foam sandwiches are then tested using a drop-weight impact test, a compression test, a bursting strength test, a sound absorption test, and a horizontal burning test. The test results indicate that the optimal properties of sandwiches occur with their corresponding PU foam density as follows: an optimal residual stress (240 kg/m3), an optimal compressive strength (240 kg/m3), and an optimal bursting strength (220 kg/m3). In addition, the sandwiches reach the HF1 level according to the horizontal burning test results. They also have an average electromagnetic interference shielding effectiveness of -48 dB, as well as a sound absorption coefficient of 0.5 in a frequency between 1500-2500 Hz, which indicates a satisfactory sound absorption effect. The nonwoven fabric/spacer fabric/PU foam sandwiches proposed in this study are mechanically strong, sound absorbent, and fire retardant, and can be used in construction material and electromagnetic shielding composites.

Fabrication of poly(vinyl alcohol) nanofibers by wire electrode-incorporated electrospinning

Wire electrodes for needleless electrospinning consist of stainless steel wires in place of cylinder electrodes. The effects of different numbers of constituent stainless steel wires on the morphology and diameter of polyvinyl alcohol (PVA) fibers are examined. With 1, 2, 3, or 4 stainless steel wires being twisted as wire electrodes, an 8, 10, or 12 wt.% polyvinyl alcohol (PVA) solution is electrospun into PVA nanofibers by using a needleless electrospinning machine. The morphology and diameter of PVA nanofibers is observed by scanning electron microscopy. The combination of the number of stainless steel wires (two), PVA solution (10 wt.%), and the collecting distance (10 cm) results in the finest diameter and an evenly formed fiber morphology. In addition, the nanofibers exhibit a wide range of diameters when electrospun with an electrode consisting of more than two stainless steel wires. Compared with the cylinder electrode, the use of a wire electrode can form nanofibers, which results in a more even morphology.

Elastic knits with different structures composed by using wrapped yarns: Function and comfort evaluations

In this study, the wrap yarns are made with antibacterial/green charcoal plied yarns as the wrap material and moisture management yarns as the core by using a rotary twisting machine. The wrap yarns and Tetoron® elastic yarns are then combined with different structures in order to form elastic knits. The elastic knits are then evaluated for their functions in terms of their antibacterial properties, far infrared radiation rate, and anion counts, as well as comfort in terms of settling time, wicking performance, water vapor permeability, softness, and air permeability, in order to examine the influences of jersey structure, stripe structures and mesh structures. The test results indicate that the combination of five green charcoal filaments and a mesh structure provides the elastic knits with the maximum functions and comfort, due to a high content of functional fibers per unit area. The optimal FIR emissivity reaches 0.89, maximum anion amount is 673±21.4, and the highest permeability is 63.9±2.6 cm3/cm2/s. As a result, the proposed elastic knits have an adjustable fabric structure that is feasible to meet any requirements and thus has a broad application range.

Polylactic acid/carbon fiber composites: Effects of polylactic acid-g-maleic anhydride on mechanical properties, thermal behavior, surface compatibility, and electrical characteristics

This study uses a reactive extrusion for the grafting of maleic anhydride on polylactic acid in order to form polylactic acid grafted maleic anhydride that serves as a compatibilizer between polylactic acid and carbon fiber. The effects of different ratios of the free radical initiator to maleic anhydride as well as the amounts of polylactic acid grafted maleic anhydride on the mechanical properties, interfacial compatibility, thermal behaviors, and electrical properties of the polylactic acid/carbon fiber composites are discussed. The test results indicate that using polylactic acid grafted maleic anhydride as compatibilizer improves the interfacial compatibility of polylactic acid/carbon fiber composites, which in turn contributes to a high electrical conductivity and the electromagnetic interference shielding effectiveness, while decreasing the surface resistance and increases. In addition, the amount of polylactic acid grafted maleic anhydride has a positive influence on their tensile properties, flexural strength, and impact strength. The differential scanning calorimetry results indicate that a high polylactic acid grafted maleic anhydride content is also conducive to crystallinity, but is not in related to the melting temperature. According to the scanning electronic microscope observation, the fractured composites that are inflicted by an impact have considerably few traces of the fibers being pulled out, which is ascribed to polylactic acid that can completely enwrap carbon fiber. Therefore, the incorporation of polylactic acid grafted maleic anhydride is proven to strengthen polylactic acid/carbon fiber composites, exemplified by their improved interfacial compatibility and properties.

PP/MWCNTs composites: Effects of length of MWCNTs on isothermal crystallization behaviors, crystalline structure, and thermal stability

This study adopts the melt compounding method to prepare /mutli-walled carbon nanotubes composites. The effects of different lengths of the mutli-walled carbon nanotubes on the isothermal crystallization behaviors, crystalline structure, and thermal stability of the polypropylene/mutli-walled carbon nanotubes composites are examined. The PLM results show that the combination of mutli-walled carbon nanotubes prevents the growth of polypropylene spherulites, and thus results in a small size of spherulites. The differential scanning calorimetry results show that the short (S-) or long (L-) mutli-walled carbon nanotubes can function as the nucleating agent of polypropylene, which accelerates the crystallization rate of polypropylene. Avrami theory analyses indicate that the addition of short-mutli-walled carbon nanotubes particularly provides polypropylene/mutli-walled carbon nanotubes composites with a high crystallization rate. The X-ray diffraction results show that the combination of mutli-walled carbon nanotubes does not pertain to the crystal structure. The TGA test results show that long-mutli-walled carbon nanotubes outperform short -mutli-walled carbon nanotubes in improving the thermal stability of polypropylene, and both can significantly improve it.

Preparation and Electromagnetic Shielding Effectiveness Evaluations of Stainless Steel/Polyester Composite Textiles

Electrically conductive stainless steel wire and synthetic polyester filament are selected as the materials for this study. Composite wrapped yarns and composite woven fabrics are successfully manufactured by* wrapping and weaving processes. The breaking strength, tenacity, elongation and work of composite wrapped yarns exhibit the optimum value at 7-D, 7-S, 14-S and 14-D, which the corresponding value are 149.3(N), 1.6(cN/dtex), 19.5(%) and 46.7(N*cm), respectively. The surface resistivity of 4 composite woven fabrics presents similar results with various weft yarns that are composed of various wrapped counts and wrapped layers. Electromagnetic shielding effectiveness (EMSE) of composite woven fabric, which varied laminated angles and laminated numbers, significantly reveal different results. The EMSE of composite woven fabrics is considerably enhanced after varying laminated angles of 45° or 90° and laminated numbers, and that of composite woven fabric (14-D-W) with a laminated angle of 90°and a laminated number 3 shows the optimum value -46 dB at 2450 MHz.