Round Robin Tests to Determine Fiber Content of Carbon Fiber-Reinforced Thermoplastic Composites by Combustion and Thermogravimetry

To propose methods to determine the fiber content of carbon fiber-reinforced plastics (CFRP) for the International Organization for Standardization, the fiber contents of CFRP with polyamide-6 were measured using a combustion method based on ISO 14127 and a thermogravimetry method based on the modified ISO 9924-3 under a round robin test managed by the Polymer Subcommittee of the Industrial Technology Cooperative Promotion Committee in Japan. In the combustion method, the fiber contents of the CFRTP (~0.3 g) were determined by the mass of carbon fiber remaining after burning (ISO 14127). The fiber contents in weight of the CFRTP with 8, 9, or 10 plies were determined to be 55.720%, 61.088%, or 65.326%, respectively, by 17 research institutes. In the thermogravimetry method, the fiber contents of the CFRTP (~10 mg) were determined by the mass of carbon fiber remaining after heating it to 600°C in nitrogen gas using thermogravimetry apparatus (modified ISO 9924-3). The fiber contents of the CFRTP with 8, 9, or 10 plies were determined to be 56.908%, 61.579%, or 64.819%, respectively, by 8 research institutes. It was confirmed that thermogravimetry method was as accurate as the combustion method based on ISO 14127.

Characterization of Native and Graft Copolymerized Albizia Gums and Their Application as a Flocculant

The functional properties and flocculation efficiency of purified Albizia saman (AS) and Albizia glaberrima (AG) gum exudates modified by graft copolymerization with acrylamide were investigated. The grafting efficiency of AS and AG was 54 and 58%, respectively. The cold water-insoluble gel of native AS and AG was 38.23 and 35.55%, which increased to 39.75 and 40.55% after graft copolymerization. Graft copolymerization of AS and AG gums reduced their oil binding and emulsion capacity from 4.89 and 3.44% to 3.69 and 2.40%, respectively. The dissolution kinetics of the native gums between 40 and 90°C and 0 and 150 min revealed a steady increase in solubility of the native gums from 6.05 to 9.53 g/L (AS) and 5.90 to 8.78 g/L (AG). The flocculation efficiency of the native AS and AG gums at 50 ppm concentration was 74.30 and 74.73%, which increased to 98.46% and 98.29% in the graft copolymerized gums, respectively.

Variation of the Pole Length in Pole-Oriented Bonded Rings due to the Location and Number of Injection Points

Polymer bonded magnets are compounds consisting of a polymer matrix with embedded hard magnetic filler particles. These materials are mainly used in applications in actor or sensor technology. One example is the application as multipolar encoder wheel in magnetic sensors. Depending on the application different requirements have to be fulfilled, such as a high pole length accuracy and repeatability. This investigation deals with the production of multipolar rings in the injection molding process for sensor applications and influences of the design of the gating system on the pole length accuracy. It is shown that the number of injection points and developing weld lines, as well as the positioning of the injection points, has a major influence on the magnetization characteristics of the molded rings. In general, a positioning of injection points and weld lines in the pole pitch and higher number of injection points lead to rings with a high reproduction accuracy of the pole length of the mold.

Synthesis, Properties, and Humidity Resistance Enhancement of Biodegradable Cellulose-Containing Superabsorbent Polymer

To improve the humidity resistance and water absorption capacity of the superabsorbent polymer (SAP), a biodegradable cellulose-containing polymer was successfully assembled through inverse suspension polymerization, using cellulose, acrylic acid, and acrylamide as monomers, Span-80 as dispersant, and potassium persulfate as initiator. The impact of conditions such as reaction temperature, ratio of oil to water, degree of neutralization, amount of cellulose, and cross-linking agents on the properties of the polymer were evaluated. The results showed that the as-prepared superabsorbent polymer exhibited the best water (859 g/g) and salt water (72.48 g/g) absorption rate, when the reaction temperature was 70°C, monomer ratio was 1 : 10, neutralization degree was 75%, and oil-water ratio was 3 : 1. Moreover, the humidity resistance of the polymer could be enhanced significantly by adding different cross-linking reagents such as epoxy chloropropane or diethylene glycol.

Isolation and Characterization of 1,3-Bis(vinylbenzyl)thymine: Copolymerization with Vinylbenzyl Thymine Ammonium Chloride

A novel bioinspired molecule, 1,3-bis(vinylbenzyl)thymine (bisVBT), was isolated as a by-product during the synthesis of 1-(4-vinylbenzyl)thymine (VBT) and analyzed with various techniques: NMR, IR, and Single-Crystal X-ray Diffraction. In addition to embodying all the desired characteristics of VBT (i.e., having the ability to undergo a 2π+2π photodimerization reaction upon UV irradiation, a derivatization site, hydrogen bonding sites, and aromatic stacking ability) the bisVBT monomer has the added benefit of having two vinyl groups for cross-polymerization. Copolymerizing the bisVBT monomer with the charged monomer vinylbenzyl triethylammonium (VBA) chloride, different copolymers/terpolymers/cross-linked network were obtained, as it was shown by the absence of the vinyl resonance in the NMR spectra. Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) showed an indication of materials with low degree of cross-linking. A Gel Permeation Chromatography (GPC) method was improved to better characterize the molecular weight distributions of the cationic structures. Preliminary qualitative cross-linking studies were performed on bisVBT-VBA copolymers, and a comparison with VBT-VBA copolymers is presented.

Effect of Urea Concentration on the Viscosity and Thermal Stability of Aqueous NaOH/Urea Cellulose Solutions

Aqueous solutions of sodium hydroxide (NaOH) and urea are a known and versatile solvent for cellulose. The dissolution of cellulose occurs at subambient temperatures through the formation of a cellulose-NaOH-urea “inclusion complex” (IC). NaOH and urea form a hydrate layer around the cellulose chains preventing chain agglomeration. Urea is known to stabilize the solution but its direct role is unknown. Using viscometry and quartz crystal microbalance with dissipation monitoring (QCM-D) it could be shown that the addition of urea reduced the solutions viscosity of the tested solutions by almost 40% and also increased the gelation temperature from approximately 40°C to 90°C. Both effects could also be observed in the presence of additional cellulose powder serving as a physical cross-linker. Using Fourier transform infrared (FTIR) spectroscopy during heating, it could be shown that a direct interaction occurs between urea and the cellulose molecules, reducing their ability to form hydrogen bonds with neighbouring chains.

Experimental Studies on the Bonding Strength and Fracture Behavior of Incompatible Materials Bonded by Mechanical Adhesion in Multilayer Rotational Molding

Rotational molding is a plastic processing method that allows for the production of seamless, hollow parts. Defined shaping of the polymeric material only takes place on the outer surface where contact to the tooling is given. The inner surface forms by surface tension effects. By sequential adding of materials, complex multilayer build-up is possible. Besides pure, single materials, filled, or multiphase systems can be processed as well. In this work, possibilities to generate bonding between supposedly incompatible materials by adding a mix-material interlayer are investigated. Interlock mechanisms on a microscale dimension occur and result in mechanical bonding between the used materials, polyethylene (PE) and thermoplastic polyurethane (TPE-U). The bonding strength between the materials was investigated to reveal the correlations between processing parameters, resulting layer build-up, and bonding strength. The failure behavior was analyzed and inferences to the influence of the varied parameters were drawn.

Radiation Crosslinking of Polyurethanes: Characterization by FTIR, TGA, SEM, XRD, and Raman Spectroscopy

Gamma radiation can be used for enhancing the physical properties of polyurethane (PU). Radiation was used to crosslink a polyurethane at room temperature; four samples of the PU solid film are irradiated at variable four radiation doses 0, 50, 100, and 150 kGy under vacuum conditions. Crosslinking radiation is more common than oxidative degradation and crosslinking is believed to be more efficient in the soft segment of PU. The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR), Thermogravimetric Analysis (TGA-DTG), and X-ray Diffraction (XRD) which have been used to investigate the effect of gamma radiation on the polyurethane (PU). The results showed that the radiation crosslinking of polyurethanes improved the thermal stability and the crystallinity. The microstructure modifications of polyurethane samples have also been studied as a function of the dose using the scanning electron microscope (SEM). The effects of gamma irradiation on the color changes of polyurethane were observed. The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence.

Modelling the Heating Process in Simultaneous Laser Transmission Welding of Semicrystalline Polymers

Laser transmission welding is an established joining process for thermoplastics. A close-to-reality simulation of the heating process would improve the understanding of the process, facilitate and shorten the process installation, and provide a significant contribution to the computer aided component design. For these reasons a thermal simulation model for simultaneous welding was developed which supports determining the size of the heat affected zone (HAZ). The determination of the intensity profile of the laser beam after the penetration of the laser transparent semicrystalline thermoplastic is decisive for the simulation. For the determination of the intensity profile two measurement systems are presented and compared. The calculated size of the HAZ shows a high concordance to the dimensions of the HAZ found using light microscopy. However, the calculated temperatures exceed the indicated decomposition temperatures of the particular thermoplastics. For the recording of the real temperatures during the welding process a measuring system is presented and discussed.

Joining of Metal-Plastics-Hybrid Structures Using Laser Radiation by Considering the Surface Structure of the Metal

Lightweight construction is a central technology in today’s industrial production. One way to achieve the climate goals is the production of hybrid compounds of metal and plastic. The manufacturing process for these hybrid parts can be divided into in-mold assembly and postmold assembly. The postmold assembly includes thermal joining by laser, which is applied in the context of this paper. For the investigations, four plastics (MABS, PA6.6-GF35, PP, and PC), which differ in their properties, and three metals (unalloyed steel, stainless steel, and aluminum) are combined and analyzed. These materials have been used, since they have a huge significance in the automotive industry. Preliminary studies showed that an adhesive bond between the two materials is achieved using metal with a structured surface. According to these studies, three structuring processes for metals (selective laser melting (SLM), NRX, and a welded metallic tissue) are tested. The quality of the material/structure combinations is tested in tensile-shear-tests, microscopy images, and alternating climate tests. Compounds with SLM-Structure achieve highest strength, while compounds with aluminum are much more complex to manufacture.