مروری بر رئولوژی نانوالیاف سلولزی در کاغذسازی

نوع مقاله : مقاله کامل علمی پژوهشی

نویسنده

استادیار گروه مهندسی صنایع سلولزی، دانشکده منابع طبیعی، دانشگاه صنعتی خاتمالانبیاء (ص) بهبهان، بهبهان، ایران

چکیده

سابقه و هدف: امروزه کاربرد نانوالیاف سلولزی برای ساخت محصولات مختلف از جمله کاغذ و مقوا، به شدت مورد تحقیق و پژوهش قرار گرفته است. نانوالیاف سلولزی از خمیرکاغذ حاصل از منابع لیگنوسلولزی مختلف و با روش‌های متنوعی ساخته می‌شود. کیفیت این مواد می‌تواند با روش‌های مختلفی مورد ارزیابی قرار گیرد. در این میان، شاخص‌های رئولوژی نانوالیاف سلولزی یکی از ساده‌ترین و کم‌هزینه‌ترین روش‌ها برای پیش‌بینی عملکرد آنها در صورت استفاده برای ساخت کاغذ و مقوا محسوب می‌شود. در این مطالعه، به طور مشخص بر روابط بین شاخص‌های رئولوژی نانوالیاف سلولزی بر خصوصیات نهایی محصولات کاغذی پرداخته می‌شود.
مواد و روش‌ها: در این مقاله، به دسته بندی مواد از لحاظ علوم رئولوژی پرداخته شد و جایگاه نانوالیاف سلولزی در بین آنها مشخص شد. سپس ضمن معرفی شاخص‌های مهم رئولوژی نانوالیاف سلولزی مثل نقطه تسلیم، ضریب میرایی، مدول ذخیره و مدول اتلاف و کرنش بحرانی، با ارائه مواردی از نتایج اندازه‌گیری شاخص‌های رئولوژی نانوالیاف سلولزی ارتباط آنها برای تعیین قابلیت تقویت کنندگی شاخص‌های کششی و ترکیدگی محصولات کاغذ و مقوا مورد بررسی قرار گرفت.
یافته‌ها: مقادیر مدول ذخیره، به‌عنوان حساس‌ترین پارامتر در سنجش‌های ویسکوالاستیکی، هر چه نسبت به مدول اتلاف بیشتر باشد نشان از قابلیت ویسکوالاستیکی با گرایش الاستیک بیشتر می‌باشد که در مورد نانوالیاف سلولزی در صورتی که نسبت مقدار مدول ذخیره حدود 4 برابر مدول اتلاف در غلظت‌های یکسان برسد دلالت بر ویسکوالاستیک بودن ماده با میزان الاستیسیته قابل توجه است. در صورتی که مقدار ضریب میرائی برای ژل‌ نانوالیاف سلولزی کم‌تر از 3/0 بدست آید نشان‌دهنده کشسان بودن زیاد این ژل‌ها با اجزایی در مقیاس نانومتر می‌باشد که این خصوصیات دلالت بر وجود ساختار درهم فرورفته شبکه‌ای نانوالیاف سلولزی و در نتیجه قابلیت تقویتی بیشتر برای کاربردهای مختلف از جمله تقویت استحکام کاغذ و مقوا است. کرنش بحرانی در مورد رفتار رئولوژی نانوالیاف سلولزی، تقریبا مستقل از درصد خشکی آن ظاهر می‌شود که دلالت بر پایداری خصوصیات ویسکوالاستیکی این ژل‌ها است. ژل‌های نانوالیاف تولیدی غلیظ و رقیق‌شده دارای رابطه نمایی با توان 3 با درصد خشکی می‌باشند. رابطه نمایی با توان 3 بین مدول و درصد خشکی، به‌عنوان یکی از معیارهای دست‌یابی به ژل نانوالیاف سلولزی در مقیاس نانومتری می‌باشد.
نتیجه گیری: در مجموع ژل نانوالیاف سلولزی جز سیال‌های ویسکوالاستیک و تیسکوتروپیک محسوب می‌شود که در استفاده برای تولید کاغذ و مقوا هر میزان شاخص‌های الاستیک بیشتری داشته باشد نشان دهنده نانوالیاف با ضریب لاغری بیشتری است که می‌تواند نقش بهتری برای بهبود خواص استحکامی محصولات کاغذ و مقوا ایفاء کند. بنابراین هنگام تولید برای پیش‌بینی دستیابی به ژل نانوالیاف سلولزی در مقیاس نانو، می‌توان از ارزیابی ارزان قیمت تعیین شاخص‌های رئولوژی نانوالیاف سلولزی به جای تهیه تصاویر الکترونی گران قیمت استفاده نمود و حتی در قیاس دو نوع نانوالیاف سلولزی، با ارزیابی خواص رئولوژی آنها عملکردشان را برای تقویت کاغذ و مقوا پیش بینی نمود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Rheology of cellulose nanofibers in paper making: An overview

نویسنده [English]

  • Pejman Rezayati Charani
Department of Cellulose Industries Engineering, College Natural Resources, Behbahan Alanbia University of Technology Khatam, Beginning of Deylam Road, Behbehan, Khuzestan
چکیده [English]

Background and objectives: Today, the use of cellulosic nanofibers is widely researched for the production of various products, such as paper and paperboard. Cellulose nanofibers are made from pulp produced from various lignocellulosic sources in various methods. The quality of these materials can be evaluated in different ways. Meanwhile, the rheology indices of cellulosic nanofibers are one of the simplest and least costly methods to evaluate the quality of this material. In this paper, specifically, the relationship between indices of rheology of cellulosic nanofibers and their ability to improve paper and board strengths for papermaking are introduced.
Materials and methods: In this article, materials were categorized in terms of rheology sciences and cellulose nanofibers were specified among them. Then, important indices of rheology of cellulose nanofibers such as yield point, damping coefficient, storage modulus, loss modulus, and yield strain were introduced by presenting some of the results of measuring the rheological indices of cellulosic nanofibers. In the following, the relationship between rheological indices and strengthening ability of cellulose nanofibers to improve tensile and burst strengths of paper and paperboard production were investigated.
Results: The more storage modulus, as the most sensitive parameter in viscoelastic measurements compared to the loss modulus, the more viscoelastic ability and more elastic tendency. For cellulose nanofibers, if the ratio of the storage modulus is about 4 times greater than the loss modulus in the same concentrations, this indicates that the material is viscoelastic with considerable elasticity. If the amount of damping coefficient for cellulose nanoparticle gel is less than 0.3, this indicates that these gels are highly elastic with components in the nanometer scale and these characteristics indicate the presence of tangled cellulose nanofiber network and as a result, more strengthening feature is available for a variety of applications as strengthening paper and paperboard products. The critical strain on the behavior of the cellulosic nanofiber’s rheology appears almost independent of its dry matter content which implies the sustainability of the viscoelastic properties of these gels. The thick and dilute produced nanofiber gels have an exponential, with power 3, relationship with dry content (n ∝ G∅). The exponential, with power 3, relationship between the modulus and dry matter percentage is one of the criteria for the achievement of a gel of nanoscale cellulosic fibres.
Conclusion: In general, cellulose nanofibers gel is considered as a viscoelastic and thixotropic fluid and when used in paper and paperboard productions, the higher elastomeric index of it creates more strength properties of products. Therefore, in order to predict the achievement of nanosized fibres gel during production, a cheaper evaluation of the cellulosic rheology indices could be used instead of expensive images and even with the comparison of two types of cellulosic nanofibers, their rheological properties predict their performance for reinforcing paper and paperboard.

کلیدواژه‌ها [English]

  • Paper and paperboard
  • Rheological indices
  • Cellulose nanofibers
  • Viscoelastic gel
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