High-Permeability Wood with Microwave Remodeling Structure

This paper presents the development of a microwave puffed wood (MPW) with novel and unique structural features in its internal structure that are based on natural wood (NW). The focus of the research was on the comprehensive visualization of the structural characteristics of MPW from the macroscopic to the microscopic scale followed by an exploration of its impregnation capabilities. The results showed that the volume of MPW increased by about 9% compared to NW due to the presence of a large number of cracked cavities. The CT images indicated that there was a significant difference between the macroscopic cracks produced by microwave processing and the natural cracks in the wood. The mercury intrusion test results showed that macro-pores increased while the micro-pores decreased in the MPW compared to in the NW. The MPW showed good fluid permeability and liquid absorption performance. The phenolic resin penetration rate of the MPW was about 20 times that of the NW, and the material absorption was more than 2 times that of the NW. The crack space enabled the MPW to serve as a fluid transportation and a storage warehouse. MPW is a super container based on natural materials. It has broad potential in more fields, such as in wood composite materials.

A Comparison of Adhesion Behavior of Urea-Formaldehyde Resins with Melamine-Urea-Formaldehyde Resins in Bonding Wood

This paper reports a comparison of adhesion behavior of urea-formaldehyde (UF) with those of melamine-urea-formaldehyde (MU) resins in bonding wood by analyzing the results published in literatures. For this purpose, the adhesion behavior of UF resins prepared by blending low-viscosity resin (LVR) with high-viscosity resin (HVR) at five different blending and two formaldehyde/urea (F/U) molar ratios (1.0 and 1.2) was compared with those of two MUF resins synthesized by either simultaneous reaction (MUF-A resins) or multi-step reaction (MUF-B resins) with three melamine contents (5, 10, and 20 wt%). As the blending (LVR:HVR) ratio increased from 100:0 to 0:100, the viscosity and molar mass (Mw and Mn) of the blended UF resins increased while the gelation time decreased. The interphase features such as maximum storage modulus (E′max), resin penetration depth, and bond-line thickness of the UF resins increased to a maximum and then decreased as the blending ratio increased. In addition, both MUF-A and MUF-B resins also showed an increase in the Mw and Mn as the melamine content increased from 5% to 20%. However, the E′max, resin penetration depth, and bond-line thickness of the MUF resins decreased as the molar mass or melamine content increased. These results indicated that the adhesion of UF resins heavily depends on the interphase features while that of the MUF resins highly depends on the cohesion of the resins.

Effect of Resin Infiltration on Bleached Enamel: An In Vitro Evaluation of Micromorphology, Resin Penetration and Microhardness

Background: Tooth bleaching is a promising aesthetic treatment for shaded teeth; however, demineralized lesions also occur after bleaching, and Icon resin can infiltrate into the demineralized lesions and then improve the color of teeth. This study aims to evaluate the effectiveness of resin infiltration on bleached teeth that are managed with different protocols by assessing the micromorphology of enamel surfaces, the depth of resin penetration and the microhardness of enamel after bleaching and Icon resin infiltration.Methods: A total of 150 noncarious premolars with sound coronal structure, which were extracted for orthodontic purposes, were obtained in this study in three parts: part Ⅰ“micromorphology of enamel surfaces”（n=60）；part II“observation the depth of the resin penetration”（n=30)；part III “Vickers hardness number values”（n=60). Both part Ⅰ and part III were divided into six subgroups. Part II was divided into three subgroups. 10 samples per subgroup. Data were analyzed using SPSS 22.0, Mann-Whitney test.Results: The surface roughness of the teeth increased after bleaching. When etched with 15 % HCl before the resin infiltration, it would result in further increase in roughness, but the surface of the bleached teeth could be as smooth as that of normal teeth after resin infiltration. There was a statistically significant increase in the mean resin penetration depth of the bleached teeth with 5-day delay of resin infiltration over the bleached teeth with resin infiltration immediately (Mann-Whitney test, P<0.05). Otherwise，the VHN values of delayed ones were similar to the normal one.Conclusions: It suggested that Icon resin infiltration treatment should be delayed after tooth bleaching but not performed right after tooth bleaching.

Investigation of closed compartment moulding for pull-winding process

This project investigates the closed compartment moulding design for pull-winding process. This is a continuation of an initial study that involved discovering how the permeability effect inside a close compartment in pull-winding processing. The mould has been designed to ensure resin penetration to the preform. The mould design has been divided into three parts for easy installation, maintenance and also cleaning after use. The mould has been tested on an actual production line at TenAsia Sdn. Bhd. The test is conducted by pulling mechanism where the machine pulls the preform winding forward when it is switched on. In this process, the resin is flowing through the hose and it has been sprayed out by the nozzle inside the mould to the preform. The test has been done using 2, 4 and 6 nozzles with various pressures to determine which one is the most suitable for penetration and covering up the preform. Based on the results, the most economical and productive design has been identified as spray type with 2 upper and lower nozzles running at an appropriate pressure of 20 psi. This pressure has been chosen based on the area covered on the preform surfaces and time taken to penetrate the preform layer. In conclusion, 20 psi pressure works better due to the resin’s deeper penetration in shorter time, less mist and very minimal excess resin.

Low Viscosity Resin Penetration Degree in Incipient Caries Lesions

Resin infiltration is considered a treatment option for initial caries lesions. To prevent enamel lesion s from further demineralization a complete and homogeneous penetration of low-viscosity resins should be accomplished. The aim of this study was to compare the penetration abilities of 3 commercial products: Icon (DMG, Germany), Fluorodose (Centrix Inc. USA) and Tetric flow (IvoclarVivadent, Schaan, Liechtenstein).Artificial white spot lesions were produced in 60 orthodontic extracted human premolars. The samples were randomly divided into 3 groups: F - weeklyapplication of 5%fluoride gel; IC � resin infiltration (Icon1-DMG) and T - treatment with composite resins (Tetric flow). Specimens were studied using confocal microscopy and penetration depths were determined. A good correlation between PC and penetration depth was thereby observed (Pearson correlation coefficient, r=0.820).

Pull Speed Influence on Fiber Compaction and Wetout in Tapered Resin Injection Pultrusion Manufacturing

In the resin injection pultrusion process (RIP), liquid resin is injected into the tapered injection chamber through the injection slots to completely wetout continuously pulled fibers. As the resin penetrates through the fibers, the resin also pushes the fibers away from the wall towards the centerline, causing compaction of the fiber reinforcements. The fibers are squeezed together due to compaction, making resin penetration more difficult; thus at low resin injection pressures, the resin cannot effectively penetrate through the fibers to achieve complete wetout. However, if the resin injection pressure is too high, the fibers are squeezed together to such an extent that even greater injection pressure is necessary to wetout the compacted fibers. The design of the injection chamber significantly affects the minimum injection pressure required to wetout the fiber reinforcements. A tapered injection chamber is considered such that wetout occurs at lower injection pressures due to the taper angle of the injection chamber. In this study, the effect of fiber pull speed on the fiber reinforcement compaction and complete fiber wetout for a tapered injection chamber is investigated.