بررسی ویژگی‌های فیزیکی- مکانیکی و مقاومت بیولوژیکی نسبت به موریانه (isoptera: termitidae) microcerotermes diversus silvestri چوب راش (fagus orientalis) تیمار‌شده به‌روش روغن‌گرمایی

چوب راش (fagus orientalis) که به‌عنوان یکی از چوب‌های مهم در صنعت سلولزی ایران شناخته شده است، دارای بافتی همگن، درجه سختی بالا و مقاومت متوسط نسبت به عوامل مخرب بیولوژیکی است. این گونه چوبی صنعتی پرکاربرد نیز مانند بسیاری از چوب‌های دیگر، علی رغم دارا بودن ویژگی های مثبت، دارای ویژگی های نامطلوب نیز می باشد. مشکلاتی همچون جذب رطوبت و عدم مقاومت کافی در برابر حمله عوامل مخربی مانند موریانه، کاربرد آن را محدود ساخته است و به همین علت در سال‏های گذشته، تلاش برای کاهش معایب چوب افزایش یافته است. اکثر روش‌های حفاظتی چوب بر پایه استفاده از مواد شیمیایی است که باعث ایجاد آلودگی در محیط زیست می‏شوند. در این میان، روش‌های اصلاح حرارتی با استفاده از محیط روغنی به‌عنوان یک روش کاملاً سبز مورد توجه قرار گرفته اند، چرا که روغن‌های مصرفی در این نوع روش اصلاحی، از منابع طبیعی به‌دست می‏آیند و منجر به ایجاد آلودگی زیست محیطی نمی شوند. در مطالعه حاضر با استفاده از روغن کلزا، روغن آفتابگردان و مخلوط هر دو روغن به نسبت مساوی، چوب‌های راش در دمای 130 درجه سانتی‌گراد به‌مدت شش ساعت و سپس در دمای 25 درجه سانتی‌گراد به‌مدت دو ساعت تیمار شدند. سپس از چوب‌های تیمارشده برای اندازه‏گیری خواص فیزیکی، مکانیکی و مقاومت در برابر موریانه استفاده شد. داده های آزمایش با استفاده از آزمون آنالیز واریانس در قالب طرح کاملاً تصادفی و گروه‌بندی میانگین مقادیر آزمایش‌شده با استفاده از آزمون چند دامنه ای دانکن (dmrt)، به‌ کمک نرم‌افزار spss 26، برای ارزیابی تفاوت‌ها مورد بررسی قرار گرفت. مقدار احتمال در این پژوهش برابر با 0.05 در نظر گرفته شد (0.05˂p). نتایج آزمون فیزیکی نشان داد که میزان هم‌کشیدگی و واکشیدگی در تمام نمونه های تیمار‌شده نسبت به نمونه شاهد به‌میزان معناداری کاهش و چگالی افزایش پیدا کرد. همچنین آزمون‌های حفاظتی نشان دهنده کاهش معنادار حملات موریانه به نمونه های تیمار‌شده در مقایسه با نمونه شاهد بود. در آزمون مقاومت به ضربه، نمونه‏های تیمارشده نسبت به شاهد کاهش نشان دادند، امّا در مدول گسیختگی و مدول الاستیسیته، نمونه‏های تیمارشده با شاهد دارای اختلاف معنی‏دار نبودند. هدف این مطالعه، بررسی اثر تیمار روغن-گرمایی به‌روش گرم-سرد بر ویژگی های فیزیکی و مکانیکی و مقاومت بیولوژیک چوب راش نسبت به حمله موریانه microcerotermes diversus silvestri بود.

investigating physical-mechanical characteristics and biological resistance to termites microcerotermes diversus silvestri (isoptera: termitidae) of heat oil-treated beech (fagus orientalis) wood

introductionthe disadvantages such as vulnerability to destructive factors and instability in dimensions create limitations in wood consumption. various methods for improving wood properties using heat treatments have been utilized, with the basis being the chemical alteration of wood through heat. treatment with hot oil can enhance undesirable wood properties by ensuring uniform heat penetration throughout the wood structure, limiting oxygen access to reduce fire risk. environmentally friendly heat treatments use natural and renewable oils without toxic substances. this study aimed to determine changes in biological resistance, physical, and mechanical properties of beech (fagus orientalis) wood samples subjected to hot oil treatment using a warm-cool method, comparing results with control samples.materials and methodsbeech wood specimens were prepared from defect-free air-dried logs, cut to standard dimensions for physical, mechanical, and biological tests. wood samples were treated with sunflower oil, rapeseed oil, and a mixture of both using a warm-cool method. tests for water absorption according to astm d4446-05 standard, three-point bending test and modulus of elasticity per astm d143-94 standard, and impact resistance per astm d256-04 standard were conducted. both selective and non-selective termite feeding tests were performed under controlled laboratory conditions following awpa-e1:06 2008 standard.results and discussioncontrol samples showed the highest weight loss in both tests compared to treated samples, significantly attracting termites. no significant differences in termite feeding percentage were observed among samples treated with different oils. hot oil treatment significantly increased beech wood density compared to control samples. samples treated with sunflower oil had significantly higher density than those treated with rapeseed or mixed oils. the increase in density may be attributed to the replacement of air within the cells with oil. the key factor contributing to this phenomenon is the heating of the air inside the wood cells using hot oil, which initially saturates the wood and subsequently creates a vacuum due to cold treatment. the vacuum created and the rapid contraction of air during cold immersion enhance the suction of oil into the wood cells. a significant difference in volumetric swelling was observed between the control samples and those treated with the mixture of the two oils after two hours of immersion. after 24 hours of immersion in water, the volumetric swelling of the control samples was significantly greater compared to all treated samples. furthermore, impact resistance decreased following the heat treatment; however, no significant differences in impact resistance reduction were observed among the samples treated with different oils in this experiment. additionally, the heat treatment did not have a significant effect on flexural strength and modulus of elasticity.conclusionsunflower oil, rapeseed oil, and their combination significantly influenced beech wood characteristics by reducing termite feeding across all treated woods noticeably. hot oil treatment altered wood chemistry by degrading hemicellulose and increasing cellulose crystallinity while oils acted as barriers against moisture absorption, enhancing biological resistance in wood. oil treatment increased beech wood density significantly depending on the density and viscosity of the oils used during treatment. the absorbed oils reduced empty spaces within the wood structure affecting weight and consequently density positively. blocking moisture reduces the amount of water entering the wood structure, improving dimensional stability. warm oil treatment significantly affects impact resistance but shows minimal changes in properties like modulus of elasticity and flexural strength compared to control samples. research results indicate a decrease in mechanical properties of wooden samples at higher temperatures during laboratory testing, intensifying with treatment temperature increase. high temperatures affect cell wall components, potentially damaging materials like hemicelluloses, leading to reduced mechanical strength, especially impact resistance. lower temperatures have less effect on strength reduction. with a maximum treatment temperature of 130 degrees celsius considered in this study, which is not high compared to other heat treatments, less significant decreases in mechanical strength were observed, showing no significant difference between control and treated samples. based on the conducted studies, the treatment of wood with heat-treated oil from rapeseed and sunflower, as well as a mixture of both oils, significantly increases the resistance of beech wood against termite attacks. on the other hand, the results indicate that the heat treatment can control and improve certain physical properties of wood, such as the degree of swelling, while it leads to a reduction in some mechanical resistances of the wood, including impact resistance.