Sunan Tiptipakorn

Characterization of SiC Whisker-Filled Polybenzoxazine Cured by Microwave Radiation and Heat

Abstract The effect of microwave and thermal curing on the properties of SiCw-filled polybenzoxazine is examined. The benzoxazine resin (BA-a) can be cured thermally above 150°C but was hardly cured by microwave irradiation even using a power up to 1 kW. The presence of only 4% by weight of the SiCw significantly reduces the processing time of the composites from two hours at 200°C using the traditional thermal cure to less than 20 minutes using a microwave cure power of 270 W. The mechanical and thermal behaviors of the SiCw-filled polybenzoxazine show no significant difference with either curing methods.

Characterization of coconut fiber-filled polyvinyl chloride/acrylonitrile styrene acrylate blends

Coconut fiber-filled composites based on PVC/ASA blend were developed. The results reveal that the impact strengths of the PVC/ASA/coconut fiber composites are significantly higher than those of PVC wood composites or polyolefin wood composites when comparison was made at the same fiber content. Dynamic mechanical analysis thermograms exhibit two distinct glass transition temperatures ( T g s ) of the blend matrix, indicating partial miscibility of the blends. The storage modulus at room temperature and T g s of the composites systematically increase with the fiber content. The tensile strength value of the blend as high as 45 MPa was obtained and found to only slightly decrease with the fiber content. The PVC/ASA blend shows a potential use as a matrix of high-impact wood composite products with good thermal dimension stability due to the outstanding impact strength and thermal properties of the blend.

Surface Segregation-typed Polyimide Blends between Silicon-containing Polyimide and Polyimides of Varied Chain Flexibility

Surface segregation behaviors of blending systems between polysiloxane‐block‐polyimide (SPI) and three polyimides with different chain flexibility (PMDA/ODA, s‐BPDA/ODA, and ODPA/ODA) have been investigated. All film samples with 50 μm thickness were characterized by surface profilometer, attenuated total reflection infrared (ATR‐IR), and ATR microscope. In this study, the films with various PSI contents were processed on a glass substrate. At low concentration of PSI (less than 10 phr), three types of the polyimides trended to migrate to the glass‐side surface, while PSI component trended to migrate to the air‐side surface. For high concentration of PSI (i.e., 10 phr and 30 phr), the glass‐side surface was covered with the polyimides, whereas the air‐side surface showed two different colors. ATR microscope revealed PMDA/ODA blending system exhibited the highest segregation level.

Introduction to Commercial Benzoxazine and Their Unique Properties

Since World War II, only few polymers, which have been developed, are able to reach the commercial stage. Polybenzoxazines are one of those few. Their ease of synthesis with tremendous molecular design flexibility allows tailor-made properties with broad range of applications. Their unique characteristics such as self-polymerizability upon heating without a need for a catalyst or curing agent, very low A-stage viscosity, near-zero volumetric shrinkage, fire-resistant behaviors, as well as their outstanding thermal and mechanical properties, make the polymer highly attractive for various applications including electronic packaging or aerospace. As a consequence, some companies start to commercialize the resins and their composites. This chapter summarizes benzoxazine resins and their related products recently commercialized by some major companies. The key properties of the polymers for engineering applications are also concisely discussed.

Effects of Electron Beam on Irradiated Polyimide/Polyaniline Composites

In this study, the composites prepared from polyimide (PI) and polyaniline (PANI) were radiated with electron beam (EB) at the radiation doses of 0, 50, 150, 200, and 300 kGy. The electrical conductivity and thermal properties of the radiated composites were determined and compared with those of the composites doped with 6M HCl. The results revealed that the electrical conductivity was enhanced from 3.42 x 10-16 S/cm (untreated polyimide without polyaniline) to 6.97 x 10-5 S/cm when the PI/PANI composite was doped with HCl at 10 phr of PANI; furthermore, the conductivity was increased to 2.16 x 10-4 S/cm for the composite at 10 phr of PANI with radiation dose of 200 kGy. In addition, it was found that the glass transition temperature of the composite was increased with the increase of PANI content for either EB radiation method or protonic acid doping method. It could be noted that the electrical conductivity values of the radiated composites were higher than those of composites doped with HCl at the same PANI content.

Thermal Degradation Kinetics of Polyurethane/polybenzoxazine Alloys

Recently, the alloys of polyurethane (PU)/polybenzoxazine (PBA-a) have been studied due to many interesting properties; however, the thermal degradation kinetics of the system has not been mentioned before. In this study, the degradation temperatures of the obtained alloys were determined using Thermogravimetric Analyzer (TGA) with various heating rate of 10, 20, 25oC/min. The polyurethane /polybenzoxazine alloys at the weight ratios of 30/70 were prepared for determination due to its highest degradation temperature. The first derivative curves of the thermograms (DTG) were deconvoluted with Peak-fit program. The results reveal three main sub-stages of degradation. According to Arrhenius Eq., the activation energies (Ea) of each degradation sub-stage were determined using Kissinger model and Fynn-Wall Ozawa model.

Recovery stress enhancement in shape memory composites from silicon carbide whisker–filled benzoxazine-epoxy polymer alloy:

In this research, the benzoxazine-epoxy shape memory polymers with outstanding recovery stress improvement were prepared by filling with highly adamantine silicon carbide whisker at 0–20 wt%. The results revealed that the storage modulus at room temperature increased with increasing silicon carbide whisker, that is, from 5.1 GPa (without silicon carbide whisker) to 8.8 GPa (at 20 wt%). Glass transition temperatures were increased with increasing silicon carbide whisker in the range of 154°C–170°C. Furthermore, all samples exhibited approximately 99% of shape fixity with recovery time ranging from 8 to 27 min. Interestingly, the incorporation of silicon carbide whisker could significantly increase recovery stress from 3.4 MPa (without silicon carbide whisker) to 11.2 MPa (at 20 wt%). Moreover, the addition of silicon carbide whisker provides microwave actuating ability to the sample. Recovery time under microwave heating was significantly shortened to be in a range of 3–5 min. These results suggest potential use of the composites as microwave-responsive sensors and other shape memory devices.

Effects of Molecular Weight of Chitosan on the Biodegradability and Thermal Properties of Polybutylene Succinate/Chitosan Composites

In this study, the biodegradability and thermal properties the composites of polybutylene succinate (PBS) and chitosan of different molecular weights (Mn = 104,105, and 106 Da) were prepared at chitosan contents of 0-10 wt%. After 10 days of microbial degradation, the results show that the amount of holes from degradation was increased with either decreasing Mn or increasing chitosan contents. However, the size of holes was increased with increasing Mn and chitosan contents. The results from Differential Scanning Calorimeter (DSC) present that the melting temperature (Tm) of PBS was decreased with increasing chitosan contents. Moreover, there was no significant difference between Tm of the composites with different Mn of chitosan. From the TGA thermograms, the decomposition temperature at 10% weight loss (Td10) was decreased with increasing chitosan contents. Moreover, the water absorption of PBS/chitosan composites was increased with increasing Mn and content of chitosan.

Blends and IPNs of Polyurethane Polymers with Thermosetting Polymers

Abstract Polyurethanes (PU) are a versatile class of polymeric materials providing many outstanding properties such as flexibility, toughness, durability, and processability. The applications of the polymers are varied depending on the PU types. However, in order to extend the usage range of applications of the urethane-based polymer, blends and an interpenetrating network (IPN) of these polymeric materials have been proposed. In this chapter, the IPNs of polyurethane with thermosetting polymers based on benzoxazine chemistry are discussed as one good example of a PU-based interpenetrating polymer network.

Effects of Levan on the Biodegradability and Thermal Properties of Polybutylene Succinate

In this study, the biodegradability and the thermal properties of PBS and levan were prepared in the internal mixer with levan contents of 0, 0.5, and 1 wt%. The results from Differential Scanning Calorimetry (DSC) present that the melting temperature of PBS was slightly decreased with increasing levan contents. That means there was no significant effect of levan on melting behavior of the composites at the added content. From the TGA thermograms, it could be seen that there was no significant effect on the thermal stability when adding levan. The degradation temperature at 5% weight loss for all composites were in the rage of 377-379 oC. Furthermore, char yields for all contents were closed to zero. Moreover, the water absorption of PBS/Levan composites was increased with levan content. The biodegradation was observed after 4-day burial period; the holes from degradation were larger with levan contents.