Low Density Wood Particleboards Bonded with Starch Foam—Study of Production Process Conditions

It has been shown that wood particleboards bonded with sour cassava starch can display low density combined with good physico-mechanical performance, thanks to starch being able to produce a strong foam that fills the interparticular space. Here we optimize the pressing conditions for the production of these panels. The procedure involved hot-plate pressing in two stages: (1) lowering the top platen to a specified thickness for a duration designated as pressing time, followed by (2) raising the top platen to allow panel expansion for a duration designated as hold time. The parameters studied were the pressing time (10 to 150 s), the hold time (290 to 890 s), and the top platen temperature (80 to 190 °C). The hold time and pressing time showed to be crucial parameters. The best operating conditions corresponded to 600 s of press cycle time, comprising 60 s of pressing time and 540 s of hold time. The top platen temperature used was 190 °C. The particleboards produced had a density of 405 kg·m−3, an internal bond strength of 0.44 N·mm−2, and a thickness swelling of 13.2%. This can be considered as very good performance, taking into account the panels’ low density.

Manufacture of laminated strand veneer (LSV) composite. Part 1: Optimization and characterization of thin strand veneers

The forest resources are changing due to fire prevention and depletion of old growth forest. Applications for small-diameter juvenile timber, especially for low-value species, such as ponderosa pine (Pinus ponderosa) are needed. In this study, a novel thin wood strand composite of P. ponderosa, 3.2 mm thick, is introduced as a veneer substitute. Optimization was performed for the processing parameters phenol formaldehyde resin content, platen temperature, and the aspect ratio strand length to thickness (L/t). Mean modulus of elasticity and modulus of rupture values of 10.2 GPa and 79.1 MPa, respectively, were obtained with the optimized formulation (5.5% resin, platen temperature 152°C, and aspect ratio of 430). These values were approximately 2–2.5 times higher than the parent small-diameter ponderosa pine lumber. The results indicate that fast-growing low-density species – such as hybrid poplars, or small-diameter timber with predominantly juvenile wood – could potentially be used to manufacture strand veneers of consistent quality with significantly higher strength and stiffness than parent material.

Property comparisons and bonding efficiency of UF and PMDI bonded particleboards as affected by key process variables

The purpose of this paper was to compare physical properties of conventional particleboard bonded with amounts of UF and PMDI resin and to examine the effect of mat moisture content (MC), wax content and platen temperature on their bonding efficiency, as determined by internal bond strength. It was found that PMDI not only gave superior board properties compared with the UF, but the amount required was reduced considerably as well. The MC of the mat and the platen temperature did not significantly affect the bonding efficiency of PMDI bonded boards, but the bonding efficiency of UF bonded boards. The inclusion of 1% wax significantly affected the bonding efficiency of both resins, however the loss in strength was higher in UF than in PMDI bonded boards.

Tungsten Chemical Mechanical Polishing Endpoint Detection

Conventional methods of controlling tungsten Chemical Mechanical Polishing (WCMP) processes have included blanket wafer polish rate and platen temperature monitoring. In order to enhance process control of WCMP, a second generation motor-current sense endpoint system was chosen as the evaluation tool. The endpoint detection system (Luxtron 9300) was installed on a WCMP polisher (IPEC 472) at the Motorola MOS6 facility. Endpoint algorithms were evaluated under various polishing conditions during time periods between pad changes. The data collected over 3 months led to a reliable endpoint recipe for both the contact and via WCMP process. The endpoint data compared with the conventional timed recipe, indicated that a time reduction at WCMP could be achieved, with a 10% increase in throughput. In addition, contact and via W-plug endpoint data showed a strong signal versus pattern density for given device types. In summary, the motor current endpoint system tested verified reliable endpoint, process control, and characterization capabilities.

Freeze-Drying of Sweet Peppers

Studies were conducted to dehydrate garden sweet peppers by means of hot-air and freeze-drying. Sweet peppers have tough, leathery skins which makes escape of moisture difficult and prolongs drying time. Our data indicates that dehydration of half-cut or slitted fruit is accomplished either by conventional hot-air or by freeze-drying in reasonably shorter periods of time than whole fruit. Change in color or shape was not observed in sweet peppers during freezedrying. Great deterioration in the green color was observed in the samples dehydrated with hot-air at 165° F. The shelf-life of the freeze-dried product is superior to that of the conventionally hot-air dried product. For freeze-drying the sweet peppers within a reasonable period of time, and to obtain a product with shape and color similar to the fresh fruit, a platen temperature of 180° F. should be used during 2 hours and then reduced to 150° F. during the rest of the drying period. Heat treatment to inactivate microbial activity of sweet peppers prior to freeze-drying greatly reduces the microbial count and does not affect the drying rate, quality and shelf-life of the end product. Deterioration of sweet peppers during drying and storage is characterized by development of off-flavor and color. Because the measurement of off-flavor is difficult in a mild pungent fruit such as sweet peppers, these studies indicate that measurement of changes in color can be used as an index of quality.