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Publications (10 of 12) Show all publications
Hietala, M., Rollo, P., Kekäläinen, K. & Oksman, K. (2014). Extrusion processing of green biocomposites: Compounding, fibrillation efficiency, and fiber dispersion (ed.). Paper presented at . Journal of Applied Polymer Science, 131(6)
Open this publication in new window or tab >>Extrusion processing of green biocomposites: Compounding, fibrillation efficiency, and fiber dispersion
2014 (English)In: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 131, no 6Article in journal (Refereed) Published
Abstract [en]

The efficiency of twin-screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch (TPS) with 10 wt % fibers was examined. The effect of the processing setup on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO-oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy, and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the TPS. Moisture uptake study revealed that the material containing TEMPO-oxidized fibers had higher moisture absorption than the other composites

Abstract [en]

The efficiency of twin-screw extrusion process to fibrillate cellulose fibers into micro/nanosize in the same step as the compounding of green bionanocomposites of thermoplastic starch with 10wt% fibers was examined. The effect of the processing set-up on micro/nanofibrillation and fiber dispersion/distribution in starch was studied using two types of cellulose fibers: bleached wood fibers and TEMPO-oxidized cellulose fibers. A composite with cellulose nanofibers was prepared to examine the nanofiber distribution and dispersion in the starch and to compare the properties with the composites containing cellulose fibers. Optical microscopy, scanning electron microscopy and UV/Vis spectroscopy showed that fibers were not nanofibrillated in the extrusion, but good dispersion and distribution of fibers in the starch matrix was obtained. The addition of cellulose fibers enhanced the mechanical properties of the thermoplastic starch. Moisture uptake study revealed that the material containing TEMPO-oxidized fibers had higher moisture absorption than the other composites.

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-7754 (URN)10.1002/app.39981 (DOI)000331004800021 ()2-s2.0-84896542434 (Scopus ID)62ae24f0-fd37-4ba9-8345-bd84d51fbe82 (Local ID)62ae24f0-fd37-4ba9-8345-bd84d51fbe82 (Archive number)62ae24f0-fd37-4ba9-8345-bd84d51fbe82 (OAI)
Note
Validerad; 2014; 20130608 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Hietala, M. & Oksman, K. (2014). Technologies for Separation of Cellulose Nanofibers. In: Kriistina Oksman; Aji P. Mathew; Alexander Bismarck; Orlando Rojas; Mohini Sain (Ed.), Handbook of Green Materials: Processing Technologies, Properties and Applications. Paper presented at . Singapore: World Scientific and Engineering Academy and Society
Open this publication in new window or tab >>Technologies for Separation of Cellulose Nanofibers
2014 (English)In: Handbook of Green Materials: Processing Technologies, Properties and Applications, Singapore: World Scientific and Engineering Academy and Society, 2014Chapter in book (Refereed)
Place, publisher, year, edition, pages
Singapore: World Scientific and Engineering Academy and Society, 2014
Series
Materials and Energy ; 5
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-21436 (URN)e94562a5-585c-49bf-98aa-5e5877d3aced (Local ID)978-981-4566-45-2 (ISBN)978-981-4566-47-6 (ISBN)e94562a5-585c-49bf-98aa-5e5877d3aced (Archive number)e94562a5-585c-49bf-98aa-5e5877d3aced (OAI)
Note

Godkänd; 2014; 20140702 (andbra)

Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved
Hietala, M., Mathew, A. P. & Oksman, K. (2013). Bionanocomposites of thermoplastic starch and cellulose nanofibers manufactured using twin-screw extrusion (ed.). Paper presented at . European Polymer Journal, 49(4), 950-956
Open this publication in new window or tab >>Bionanocomposites of thermoplastic starch and cellulose nanofibers manufactured using twin-screw extrusion
2013 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, no 4, p. 950-956Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate if cellulose nanofiber (CNF) gels with high water contents can be processed to nanocomposites with starch powder using continuous twin-screw extrusion and to improve the mechanical properties and moisture sensitivity of thermoplastic starch. Nanocomposites with 0, 5, 10, 15 and 20 wt% cellulose nanofiber content were prepared. The characterization methods were conventional tensile testing, UV/Vis spectroscopy, scanning electron microscopy and moisture absorption. The cellulose nanofiber gel with high water content was mixed with starch powder, fed to the extruder as powder, performing the gelatinization of starch as well as the mixing of CNF in one step. The microscopy study showed that the CNF aggregated during the process and that the screw configuration needs to be more distributive and dispersive to get homogeneous material. The results showed that the addition of CNF improved the mechanical properties and had a positive effect on moisture uptake of the thermoplastic starch. Also, the translucency of the TPS/CNF composite films remained, even with high CNF content (20 wt%).

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-14508 (URN)10.1016/j.eurpolymj.2012.10.016 (DOI)000317151600021 ()2-s2.0-84875229726 (Scopus ID)de0ef9a8-ab15-42b8-a92d-cde8978ae408 (Local ID)de0ef9a8-ab15-42b8-a92d-cde8978ae408 (Archive number)de0ef9a8-ab15-42b8-a92d-cde8978ae408 (OAI)
Note
Validerad; 2013; 20121107 (andbra)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Oksman, K., Mathew, A. P., Jonoobi, M., Hietala, M. & Vargas, N. H. (2013). Cellulose nanocomposites processing using extrusion (ed.). In: (Ed.), M.T. Postek; R.J. Moon; A Rudie; M Bilodeau (Ed.), Production and Applications of Cellulose Nanomaterials: (pp. 99-102). Paper presented at . : TAPPI Press
Open this publication in new window or tab >>Cellulose nanocomposites processing using extrusion
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2013 (English)In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 99-102Chapter in book (Refereed)
Abstract [en]

We have been working with development of compounding extrusion process for cellulose nanocomposites, since 2003. Feeding and dispersion of the nanocellulose materials are the main challenges and we have developed two specific processing routes; i) liquid feeding of the nanomaterials into the extruder and ii) dry feeding of nanomaterials as a master batch, to address the feeding problem. Composites with aggregated, partially dispersed or fully dispersed nanocellulose crystals or fibers have been obtained depending on the extent of the separation of cellulose nanocrystals or nanofibers in the liquid medium or in the master batch and the interaction of nanocelluloses with the polymer matrix. We aim to produce nanocomposites with good mechanical properties, thermal stability and transparency and at the same time develop an energy efficient and cost effective processing methodology, which can be up-scaled in industrial level.

Place, publisher, year, edition, pages
TAPPI Press, 2013
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-20091 (URN)1db992f7-ffb5-4475-909c-803359c46b9f (Local ID)978-1-59510-224-9 (ISBN)1db992f7-ffb5-4475-909c-803359c46b9f (Archive number)1db992f7-ffb5-4475-909c-803359c46b9f (OAI)
Note
Godkänd; 2013; 20130608 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved
Oksman, K., Mathew, A. P., Jonoobi, M., Siqueira, G., Hietala, M. & Aitomäki, Y. (2013). Cellulose nanofiber isolated from industrial side-streams (ed.). In: (Ed.), M.T. Postek; R.J. Moon; A Rudie; M Bilodeau (Ed.), Production and Applications of Cellulose Nanomaterials: (pp. 187-190). Paper presented at . : TAPPI Press
Open this publication in new window or tab >>Cellulose nanofiber isolated from industrial side-streams
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2013 (English)In: Production and Applications of Cellulose Nanomaterials, TAPPI Press, 2013, p. 187-190Chapter in book (Refereed)
Abstract [en]

Isolation of cellulose nanofibers from industrial side-streams as raw material is interesting from several reasons; it will not only result in lower overall cost of the nanofibers but also add value for many different processes and products. We have used sludge, a residue from pulp production, carrot residue from juice production, and several agricultural waste products as the starting material to isolate nanofibers. The isolation process was made using a Masuko ultra fine friction grinder and our aim have been to optimize the processing parameters for the lowest energy consumption. In addition to developing the isolation process, the isolated nanofibers structure and properties were characterized. Typically, the isolated nanofibers are bundles with diameters lower than 100 nm. In particular, we found that carrot nanofibers have a uniform fiber size less than 50 nm. Scanning electron microscopy studies showed entangled nanofiber networks and the mechanical properties of nanofiber networks demonstrated a positive impact on modulus and strength when compared to networks with microsized fibers. The improvement is increased with decreased fiber size indicating more efficient fibrillation. From these studies, we have shown that industrial side-streams are excellent raw material sources for nanofiber preparation, being cheaper than other raw materials and consuming less energy for isolation while showing good properties.

Place, publisher, year, edition, pages
TAPPI Press, 2013
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-19980 (URN)0c91e881-765a-4d19-aeb5-7696f348d6c2 (Local ID)978-1-59510-224-9 (ISBN)0c91e881-765a-4d19-aeb5-7696f348d6c2 (Archive number)0c91e881-765a-4d19-aeb5-7696f348d6c2 (OAI)
Note
Godkänd; 2013; 20130608 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved
Hietala, M. (2012). Extrusion processing of wood-based biocomposites (ed.). (Doctoral dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Extrusion processing of wood-based biocomposites
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Interest in biocomposite materials and their use in various applications has been growing steadily over the past 10-15 years. Increasing environmental awareness and lower material costs are the main driving forces for using renewable materials, such as wood and cellulose fibers, as reinforcement in polymer composites. In addition to the materials used in the composite preparation, the processing has a large impact on the final properties of the composite. Therefore, the main thrust of this work has been on processing of wood-based biocomposite materials using twin-screw extrusion.In the first part of the work (Papers I, II and III), wood-plastic composites were manufactured using twin-screw extrusion. Currently, wood flour consisting of small wood particles with low aspect ratio is used as the main wood raw material in commercial woodplastic composites. A better reinforcement is achieved by using wood fibers with a higher aspect ratio, but individual fibers are seldom used in composite manufacturing due to processing problems and higher cost. Therefore, the objective of the first part of this work was to study the use of wood chips as raw material in wood-plastic composites and the possibility to separate individual fibers from the wood chips during the composite manufacturing process. The effect of extrusion parameters and raw materials on the aspect ratio of the wood particles/fibers and on the mechanical properties of the composites was evaluated. The study showed that wood chips can be used as raw material in a one-step process for manufacturing wood-plastic composites, and that it is possible to separate individual fibers with a higher aspect ratio than wood flour from the wood chips under suitable processing conditions. The second part of the work (Papers IV and V) focused on the twin-screw extrusion of cellulose nanocomposites. The use of nanosized cellulose fibers to reinforce polymer matrices has many benefits over the macrosized fibers, such as the high surface area and large aspect ratio. However, the preparation of cellulose nanocomposites is more complicated due to the high hydrophilicity and aggregation tendency of nanocellulose, meaning that drying of the nanofibers is not recommended when good dispersion of nanofibers is needed. Therefore, the aim was to study the processing of green cellulose nanocomposites with twin-screw extrusion using thermoplastic starch as the matrix polymer and cellulose nanofibers with high water content as the reinforcement (Paper IV). In addition, the effect of twin-screw extrusion on separating micro/nanoscale fibers from cellulose fibers during the compounding of biocomposites was studied (Paper V). The fibrillation of nanocellulose is a highly energy intensive process; therefore, it would be very beneficial if it could be done at the same step as the compounding of the composites. The preparation of thermoplastic starch and composite compounding was performed in one step, and the effects of extrusion compounding on the dispersion of the cellulose nanofibers, on the micro/nanofibrillation of cellulose fibers, and on the composites’ mechanical, optical and moisture absorption properties were studied. The results showed that some aggregation of cellulose nanofibers occurred during the extrusion process, but that the addition of cellulose nanofibers had a positive effect on the properties of the prepared bionanocomposites. Nanofibrillation of cellulose was not accomplished using the selected processing conditions; however, dispersion of the fibers was enhanced.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2012
Series
Doctoral thesis / Luleå University of Technology 1 jan 1997 → …, ISSN 1402-1544
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-26162 (URN)cee396ee-ca6a-4d79-b971-974545fcbebe (Local ID)978-91-7439-541-9 (ISBN)cee396ee-ca6a-4d79-b971-974545fcbebe (Archive number)cee396ee-ca6a-4d79-b971-974545fcbebe (OAI)
Note
Godkänd; 2012; 20121025 (maihie); DISPUTATION Ämne: Trä- och bionanokompositer/Wood and Bionanocomposites Opponent: Professor Kaarlo Niskanen, Institutionen för tillämpad naturvetenskap och design, Mittuniversitetet, Sundsvall Ordförande: Professor Kristiina Oksman, Avd för materialvetenskap, Institutionen för teknikvetenskap och matematik Luleå tekniska universitet Tid: Torsdag den 17 januari 2013, kl 10.00 Plats: E632, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-28Bibliographically approved
Hietala, M. (2011). Extrusion processing of wood raw materials for use in wood-polymer composites (ed.). (Licentiate dissertation). Paper presented at . Luleå: Luleå tekniska universitet
Open this publication in new window or tab >>Extrusion processing of wood raw materials for use in wood-polymer composites
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The interest in wood-polymer composites and their use in different applications has been growing over the last 10-15 years. Environmental issues and demands on lower material costs are the driving forces behind the increasing use of renewable materials such as wood and other natural fibres as reinforcement in polymer composites. Wood flour consisting of small wood particles is currently used as the main wood raw material in commercial wood-polymer composites. However, the reinforcing potential of wood flour is limited. A better reinforcement could be achieved by using wood fibres with a higher aspect ratio as raw material, but individual fibres are seldom used in composite manufacturing due to processing problems and high cost. Therefore, the objective of the work was to study the possibility to use wood chips as raw material and separate individual fibres with higher aspect ratios from the wood chips during the composite manufacturing process. First, the effect of the extrusion process only on wood raw material was studied without a matrix polymer, and then composites using polypropylene as matrix were made. The main goal was to produce wood particles/fibres with high aspect ratio during the manufacturing of wood polymer composites. The effects of extrusion parameters, different screw configurations, raw materials and raw material pre-treatments were evaluated. The size of the separated wood particles and fibres was measured using optical fibre analysis methods. Microstructure of wood particles as well as the fractured surfaces of prepared composites were examined using electron microscopy. The mechanical properties of the composites were measured using flexural and impact testing. The results showed that wood chips can be used as raw material in a one-step manufacturing process of wood-polymer composites. Also, individual fibres with a higher aspect ratio than wood flour were separated from the wood chips with suitable processing conditions

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2011
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-26720 (URN)fbceb5a6-c7fb-4ded-baa0-c87feac9b6c0 (Local ID)978-91-7439-229-6 (ISBN)fbceb5a6-c7fb-4ded-baa0-c87feac9b6c0 (Archive number)fbceb5a6-c7fb-4ded-baa0-c87feac9b6c0 (OAI)
Note
Godkänd; 2011; 20110302 (ysko); LICENTIATSEMINARIUM Examinator: Professor Kristiina Oksman, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Diskutant: Associate Professor Roberts Joffe, Institutionen för teknikvetenskap och matematik, Luleå tekniska universitet Tid: Torsdag den 7 april 2011 kl 13.00 Plats: E246, Luleå tekniska universitetAvailable from: 2016-09-30 Created: 2016-09-30 Last updated: 2018-05-28Bibliographically approved
Hietala, M., Niinimäki, J. & Oksman, K. (2011). Processing of wood chip-plastic composites: effect on wood particle size, microstructure and mechanical properties (ed.). Paper presented at . Plastics, rubber and composites, 40(2), 49-56
Open this publication in new window or tab >>Processing of wood chip-plastic composites: effect on wood particle size, microstructure and mechanical properties
2011 (English)In: Plastics, rubber and composites, ISSN 1465-8011, E-ISSN 1743-2898, Vol. 40, no 2, p. 49-56Article in journal (Refereed) Published
Abstract [en]

Wood chips were used as raw material in extrusion of wood-plastic composites. Wood-plastic composites with similar to 50 wt-% wood content were manufactured by using two different compounding methods. Dried and undried wood chips were used to investigate the effect of wood moisture content on the wood particle size and whether the drying process could be carried out in the same step. Wood particle properties were measured using optical fibre analysis. Microscopical methods were used to examine the microstructure of wood particles. Furthermore, the prepared composites' mechanical properties were studied. The particle size of wood chips was significantly reduced during extrusion in both processing methods. The undried wood chips had higher aspect ratios in comparison with the dried wood chips after extrusion. Despite the higher aspect ratio, the mechanical properties of composites manufactured with undried wood chips were not better than the properties of composites with dried wood chips

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-5850 (URN)10.1179/174328911X12988622800855 (DOI)000288594900002 ()2-s2.0-79953068312 (Scopus ID)409cc390-a462-11df-a707-000ea68e967b (Local ID)409cc390-a462-11df-a707-000ea68e967b (Archive number)409cc390-a462-11df-a707-000ea68e967b (OAI)
Note
Validerad; 2011; 20100810 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Hietala, M., Samuelsson, E., Niinimäki, J. & Oksman, K. (2011). The effect of pre-softened wood chips on wood fibre aspect ratio and mechanical properties of wood-polymer composites (ed.). Paper presented at . Composites. Part A, Applied science and manufacturing, 42(12), 2110-2116
Open this publication in new window or tab >>The effect of pre-softened wood chips on wood fibre aspect ratio and mechanical properties of wood-polymer composites
2011 (English)In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 42, no 12, p. 2110-2116Article in journal (Refereed) Published
Abstract [en]

The objective of this work was to study the effect of chemical pre-treatment and moisture content of wood chips on the wood particle aspect ratio after compounding in a twin-screw extruder and on the mechanical properties of wood-polymer composites (WPC). Composites with 50 wt% wood content were manufactured using pre-treated and untreated wood chips. The effect of wood moisture content on composite properties was studied by using dried and undried wood chips. The mechanical properties and fracture surfaces of the composites as well as the microstructure and aspect ratio of wood particles after compounding were studied. The highest wood particle aspect ratio after extrusion was achieved by using pre-treated, undried wood chips as raw material. The chemical pre-treatment was found to enhance the defibration of wood chips as well as the mechanical properties of the composites.

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-7199 (URN)10.1016/j.compositesa.2011.09.021 (DOI)000297398000028 ()2-s2.0-80055070698 (Scopus ID)58633539-b476-4160-9ba2-a6973f3545e8 (Local ID)58633539-b476-4160-9ba2-a6973f3545e8 (Archive number)58633539-b476-4160-9ba2-a6973f3545e8 (OAI)
Note
Validerad; 2011; 20110525 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-07-10Bibliographically approved
Hietala, M., Niinimäki, J. & Oksman, K. (2011). The use of twin-screw extrusion in processing of wood: The effect of processing parameter and pretreatment (ed.). Paper presented at . BioResources, 6(4), 4615-4625
Open this publication in new window or tab >>The use of twin-screw extrusion in processing of wood: The effect of processing parameter and pretreatment
2011 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 6, no 4, p. 4615-4625Article in journal (Refereed) Published
Abstract [en]

In this study the effect of processing parameters on different types of wood raw material in extrusion was examined. The study consisted of two parts: the first part was to break and separate individual fibers from wood chips during the extrusion process; in the second part the effect of chemical pre-treatment and screw elements on wood raw material was evaluated. Statistical analysis was performed to evaluate the most important factors affecting wood particle size in extrusion. The statistical analysis showed that the screw speed is the main factor affecting wood fiber length in twin-screw extrusion of wood chips. This study showed that a twin-screw extruder can be used to separate individual fibers from wood chips, and the separated fibers have higher aspect ratios than the wood flour particles typically used in wood-polymer composites. When more fibrous and chemically softened wood raw material was used, fibers with even higher aspect ratios were obtained.

National Category
Bio Materials
Research subject
Wood and Bionanocomposites
Identifiers
urn:nbn:se:ltu:diva-15043 (URN)e81826c9-e1f5-4a5b-b78e-23a1373d97eb (Local ID)e81826c9-e1f5-4a5b-b78e-23a1373d97eb (Archive number)e81826c9-e1f5-4a5b-b78e-23a1373d97eb (OAI)
Note
Validerad; 2012; 20110525 (krioks)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2018-05-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9076-931x

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