To measure the modulus of rupture (MOR) of particleboard, a method for determining sample size was developed. First, the MOR of a large number of samples was measured. A total of 10000 sample means were calculated by applying Monte Carlo simulations to the measured MORs, and relationships between sample size and sample mean were analyzed. When the sample size was 15, 9605 sample means among the 10000 sample means were within in the 95% confidence interval. As a result, the sample size was set at 15, and the probability of means occurring within the interval was very high, i.e., 96.05%. Next, the 5, 10, 20, and 30% points of the 9605 sample means were calculated, which reached the 95% confidence interval when the sample sizes were 10, 8, 4, and 2, respectively. For example, when the sample size was 2, the probability of means occurring within the interval was relatively high, i.e., 67.55%. Because the general method calculated a sample size of 28, our method could markedly decrease the sample size.

Partial compressive properties of lateral faces in Cross Laminated Timber (CLT) are important when we calculate the criteria for connections. However, the technical knowledge from studies of compression behavior of lateral faces in CLT is still limited. In this study, we determined partial compressive properties, yield stress, and initial and secondary stiffness for lateral faces when using CLT made of Japanese cedar. There were 24 types of specimens that varied in width of loading plates, location of loading plates, presence or absence of edge bonds or side margins. Results of experiments showed that the width of the applied loading device and of the side margin have a potent influence. It is assumed that the effect of the width of the applied loading device is a size effect. The size margin effect was greater when the width of the loading plates decreased. Specimens with greater than 100 mm side margins can be considered to be of infinite length. The presence of edge bonds contributes to increasing partial compressive strength. On the other hand, the perimeters of the location of the loading plates do not have a potent influence.

Most of the bamboo species in China provide excellent raw materials for producing pulp and paper. However, the bamboo are usually treated by chemical pulping methods. There are no studies previously reported about thermomechanical pulping of bamboo. The objectives of this study are to investigate the effect of chemi-thermomechanical pulping, through chemical pretreatment and pressurized refining, on the chemical characteristic of fiber generated from moso-bamboo (Phyllostachys pubescens) and to improve fiber properties using a thermomechanical refiner for the fabrication of bamboo pulps. Lignin in bamboo thermomechanical pulp (TMP) was characterized by nitrobenzene oxidation, pyrolysis-gas chromatography-mass spectrometry and scanning electron microscopy to better understand the structural changes of TMP long fibers and fines in the process. TMP prepared by the alkaline pretreatment at 100ºC showed higher pulp density, tensile index, tear index and pulp brightness than that prepared at 160ºC. Results of fractionation and chemical analysis showed that shorter fibers contained less lignin and more xylan.

This study aimed to evaluate the economic impacts of increasing the ratio of domestic timber used in wooden framework for residential construction. We performed two assessments: a simulation in which the ratio of domestic timber utilization in Japanese wooden framework residential industry is increased by 1% above the actual ratio, and a case analysis of the leading housing company, T Home. The findings showed that increasing the ratio of domestic timber not only had an overall economic effect but also affected the earnings of the housing manufacturer in some cases. On the other hand, in the simulation, induced production increased by 4.49 billion yen and the gross value added increased by 2.10 billion yen if the ratio of domestic timber utilization in the Japanese wooden-framework residential construction industry increased by 1% above the actual ratio of 2018. The results of the simulation and the case analysis proved that the economic impact on the forest products industry is larger when wood products are processed in Japan, even if they originate from a foreign country and the economic impact on forestry is larger when lumber rather than either plywood or laminated timber is used.

Wood samples treated with water-soluble fire retardants were exposed to natural weathering for up to 36 months at three locations in Japan. Three levels of retentions were applied to the fire-retardant-treated (FRT) wood samples. The duration of maintaining the fire-retardant performance based on the Building Standard Law of Japan was extended by applying excess retention to the initial FRT wood samples. On the other hand, it was presumed that the extended effects from excessive retention of initial FRT wood would be limited. Based on changes in the form of the heat release rate due to weathering and the fire-retardant retentions of weathered FRT wood samples, it was presumed that the fire-retardant retention in the wood samples decreased near the surface after weathering. It was also presumed that the gradient of fire-retardant retention in the wood samples affected the relation between total heat released and fire-retardant retention. Thus, to predict the fire performance of FRT wood after weathering, we suggest that the fire-retardant distribution in the wood be considered.

Dakekanba (Erman's birch) is a pioneer species that has not been used sufficiently in practical applications even though it is the most abundant wood source in the Hokkaido prefecture. We believe that it has potential as a valuable material for use in baseball bats. Assuming that the critical factor for baseball bats is an impact strength, we elucidated the relationships between slope of grain (SoG) and impact strength or impact fracture energy of dakekanba wood by conducting impact bending tests. Results revealed that the Hankinson equation could be used to calculate these relationships to impact strength because they were similar to those considered in previous studies of impact fracture energy. Cylindrical wood specimens such as bat grips were assessed in the impact bending tests, and dakekanba wood was compared with woods used for commercial bats. After impact strength were corrected based on SoG and density, both strength and fracture energy of dakekanba wood were found to be nearly the same as those of commercial wood species for baseball bats. Prototype bats of dakekanba wood were manufactured and experimentally used by a baseball club at Kyoto University. The prototypes were confirmed to have sufficient durability, as no bats broke during their one-week trial use. On a questionnaire survey, players responded with “good” or “normal” regarding bat feeling, flown distance, etc. after hitting with the prototypes. Our study reveals that dakekanba wood has good potential as a baseball-bat material.

In this research, laboratory sheets made from rice straw bleached chemical pulps were impregnated with a ZnCl₂ aqueous solution to prepare high wet-strength paper, and the effects of the concentration of the ZnCl₂ solution, impregnation temperature and period, and ethanol washing period were evaluated through single factor tests, The optimal conditions was determined to be 60%, 65ºC, 10 min, and 12 min, respectively. Under these conditions, the dry tensile and dry burst indices of the sheet prepared from the impregnated laboratory sheets doubled, and both the wet indices quadrupled as compared to those from untreated laboratory sheets. There were no significant changes in the cellulose crystal form and crystallinity. However, the paper surface morphology changed significantly.