Wood fiber reinforced polylactide is a biodegradable composite where both fibers and matrix are from renewable resources. In the development of such new materials, information on mechanical behavior on the macroscopic and the molecular level is useful. In this study, dynamic Fourier transform infrared (FT-IR) spectroscopy is used to measure losses at the molecular level during cyclic tensile loading for bonds that are characteristic of the cellulosic fibers and the polylactid matrix. This molecular behavior is compared with measured macroscopic hysteresis losses for different moisture levels. The results show that moisture ingress will transfer the load from the fibers to the matrix, and that a more efficient fiber-matrix interface would diminish mechanical losses. Although the dynamic FT-IR spectroscopy method is still qualitative, this investigation shows that it can provide information on the stress transfer of the constituents in wood fiber reinforced plastics.

Effects of butantetracarboxylic acid (BTCA) modification, choice of matrix, and fiber volume fraction on hygroexpansion of wood fiber composites have been investigated. Untreated reference wood fibers and BTCA-modified fibers were used as reinforcement in composites with matrices composed of polylactic acid (PLA), polypropylene (PP), or a mixture thereof. The crosslinking BTCA modification reduced the out-of- plane hygroexpansion of PLA and PLA/PP composites, under water-immersed and humid conditions, whereas the swelling increased when PP was used as matrix material. This is explained by difficulties for the BTCA- modified fibers to adhere to the PP matrix. Fiber volume fraction was the most important parameter as regards out-of-plane hygroexpansion, with a high-fiber fraction leading to large hygroexpansion. Fiber-matrix wettability during processing and consolidation also showed to have a large impact on the dimensional stability and moisture uptake.

Paper-reinforced plastics are gaining increased interest as packaging materials, where mechanical properties are of great importance. Strength and stress transfer in paper sheets are controlled by fibre-fibre bonds. In paper-reinforced plastics, where the sheet is impregnated with a polymer resin, other stress-transfer mechanisms may be more important. The influence of fibre-fibre bonds on the strength of paper-reinforced plastics was therefore investigated. Paper sheets with different degrees of fibre-fibre bonding were manufactured and used as reinforcement in a polymeric matrix. Image analysis tools were used to verify that the difference in the degree of fibre-fibre bonding had been preserved in the composite materials. Strength and stiffness of the composites were experimentally determined and showed no correlation to the degree of fibre-fibre bonding, in contrast to the behaviour of unimpregnated paper sheets. The degree of fibre-fibre bonding is therefore believed to have little importance in this type of material, where stress is mainly transferred through the fibre-matrix interface.

The stress transfer ability at the fiber-matrix interface of wood fiber composites is known to affect the mechanical properties of the composite. The evaluation of interface properties at the level of individual fibers is however difficult due to the small dimensions and variability of the fibers. The dynamical mechanical properties of composite and constituents, in this case wood fibers and polylactide matrix, was here used together with micromechanical modeling to quantify the stress transfer efficiency at the fiber-matrix interface. To illustrate the methodology, a parameter quantifying the degree of imperfection at the interface was identified by inverse modeling using a micromechanical viscoelastic general self-consistent model with an imperfect interface together with laminate analogy on the composite level. The effect of moisture was assessed by comparison with experimental data from dynamic mechanical analysis in dry and moist state. For the wood fiber reinforced polylactide, the model shows that moisture absorption led to softening and mechanical dissipation in the hydrophilic wood fibers and biothermoplastic matrix, rather than loss of interfacial stress transfer ability.

Delignified chemical wood pulp fibers can be designed to have a controlled structure of cellulose fibril aggregates to serve as porous templates in biocomposites with unique properties. The potential of these fibers as reinforcement for an epoxy matrix (EP) was investigated in this work. Networks of porous wood fibers were impregnated with monomeric epoxy and cured. Microscopy images from ultramicrotomed cross sections and tensile fractured surfaces were used to study the distribution of matrix inside and around the fibers - at two different length scales. Mechanical characterization at different relative humidity showed much improved mechanical properties of biocomposites based on epoxy-impregnated fibers and they were rather insensitive to surrounding humidity. Furthermore, the mechanical properties of cellulose-fiber biocomposites were compared with those of cellulose-nanofibril (CNF) composites; strong similarities were found between the two materials. The reasons for this, some limitations and the role of specific surface area of the fiber are discussed.

A composite can be defined as a material composed of two or more components having distinct morphology and chemistry, and giving synergetic effects. In this paper the term biocomposite is used, referring to i) a material having at least one bio-component (e.g. wood pulp fibres and nanofibrils) or ii) biomaterials intended for biomedical applications. The utilization of wood pulp fibres in composite materials has gained major interest during the last years. There are various wood pulp fibres that can be used as reinforcement in composites, e.g. thermo-mechanical pulp (TMP), chemi-thermo-mechanical pulp (CTMP) and kraft pulp fibres. Depending on the pulping process (TMP, CTMP or kraft pulp), the pulp fibres differ greatly with respect to the fibre morphology and chemistry. Kraft pulp fibres have been one of the most used raw materials for producing nanocellulose. Nanocellulose from wood refers to various cellulose nano-materials such as cellulose nanocrystals and nanofibrillated cellulose. Nanofibrillated cellulose is composed of a major fraction of structurally homogeneous nanofibrils having typical widths in the nanometre scale and lengths in the micrometre scale. Wood pulp fibres and nanofibrils have been proposed as reinforcement in composite materials. Some of the major motivations have been the potential improvements by using fibres and nanofibrillated materials with respect to e.g. strength, biodegradability and functionality. The purpose of the present work is to review some advances in biocomposite research and development, including three focus areas; structured biocomposites, flexible biocomposites and biomaterials.

Laminates of compression-molded glycerol-plasticized wheat gluten (WG) films surrounded and supported by poly(lactic acid) (PLA) films have been produced and characterized. The objective was to obtain a fully renewable high gas barrier film with sufficient mechanical integrity to function in, for example, extrusion-coating paper/board applications. It was shown that the lamination made it possible to make films with a broad range of glycerol contents (0-30 wt %) with greater strength than single unsupported WG films. The low plasticizer contents yielded laminates with very good oxygen barrier properties. In addition, whereas the unsupported WG films had an immeasurably high water vapor transmission rate (WVTR), the laminate showed values that were finite and surprisingly, in several cases, also lower than that of PLA. Besides being a mechanical support (as evidenced by bending and tensile data) and a shield between the WG and surrounding moisture, the PLA layer also prevented the loss of the glycerol plasticizer from the WG layer. This was observed after the laminate had been aged on an "absorbing" blotting paper for up to 17 weeks. The interlayer adhesion (peel strength) decreased with decreasing glycerol content and increasing WG film molding temperature (130 °C instead of 110 °C). The latter effect was probably due to a higher protein aggregation, as revealed by infrared spectroscopy. The lamination temperature (110-140 °C) did not, however, have a major effect on the final peel strength.

This paper reports the preparation and characterization of nanocomposite films based on different chitosan matrices and nanofibrillated cellulose (NFC) for the purpose of improving strength properties. The nanocomposite films were prepared by a simple procedure of casting a water-based suspension of chitosan and NFC, and were characterized by several techniques: namely SEM, X-ray diffraction, visible spectrophotometry, TGA, tensile and dynamic-mechanical analysis. The films obtained were shown to be highly transparent (transmittance varying between 90 and 20% depending on the type of chitosan and NFC content), flexible, displayed better mechanical properties, with a maximum increment on the Young’s modulus of 78% and 150% for high molecular weight (HCH) and water-soluble high molecular weight (WSHCH) filled chitosans, respectively; and of 200% and 320% for low molecular weight (LCH) and water-soluble filled (WSLCH) chitosans, respectively. The filled films also showed increased thermal stability, with, for example, an increase in the initial degradation temperature (Tdi) from 227 °C in the unfilled LCH film up to 271 °C in filled LCHNFC50% nanocomposite films, and a maximum degradation temperature (Td1) raising from 304 °C to 313 °C for the same materials.

This study reports on the effect of gamma radiation on morphological, thermal, and water barrier properties of pure ethylene vinyl alcohol copolymers (EVOH29 and EVOH44) and its biocomposites with the nanofiller microfibrillated cellulose (2 wt%). Added microfibrillated cellulose (MFC) preserved the transparency of EVOH films but led to a decrease in water barrier properties. Gamma irradiation at low (30 kGy) and high doses (60 kGy) caused some irreversible changes in the phase morphology of EVOH29 and EVOH44 copolymers that could be associated to crosslinking and other chemical alterations. Additionally, the EVOH copolymers and the EVOH composites reduced the number of hygroscopic hydroxyl functionalities during the irradiation processing and novel carbonyl based chemistry was, in turn, detected. As a result of the above alterations, the water barrier properties of both neat materials and composites irradiated at low doses were notably enhanced, counteracting the detrimental effect on water barrier of adding MFC to the EVOH matrix. © 2008 Wiley Periodicals, Inc.

The SESBE research project aims to develop novel smart sandwich façade elements with high insulating capabilities while providing a reduced thickness in conjunction with superior mechanical and durability properties. The present paper mainly focuses on the verification of the mechanical performance of the glass fibre reinforced polymer (GFRP) connectors in the façade element composed of reactive powder concrete (RPC) panels with foam concrete insulation between them. Because of the reduced thickness of the large façade elements, the performance of the connectors is critical for the entire structural concept. A description of structural performance and results based on experimental methods and finite element (FE) analysis are presented.

Cellulose from wood fibers can be modified for use in flame-retardant composites as an alternative to halogen-based compounds. For this purpose, sulfite dissolving pulp fibers have been chemically modified by phosphorylation, and the resulting material has been used to prepare cellulose nanofibrils (CNF) that have a width of approximately 3 nm. The phosphorylation was achieved using (NH₄)₂HPO₄ in the presence of urea, and the degree of substitution by phosphorus was determined by X-ray photoelectron spectroscopy, conductometric titration, and nuclear magnetic resonance spectroscopy. The presence of phosphate groups in the structure of CNF has been found to noticeably improve the flame retardancy of this material. The nanopaper sheets prepared from phosphorylated CNF showed self-extinguishing properties after consecutive applications of a methane flame for 3 s and did not ignite under a heat flux of 35 kW/m², as shown by flammability and cone calorimetry measurements, respectively.

Bionanocomposites represent an emerging group of nanostructured hybrid materials. Besides the structural and functional properties similar to conventional nanocomposites, the inherent properties, namely, biocompatibility and biodegradability, make these environmentally benign materials highly attractive for both academia and industry. Research on bionanocomposites is an interdisciplinary field that is closely related to packaging and biological systems, such as tissue engineering and drug delivery, and also extended to electronics, sensor, and energy applications, just to name a few. This chapter will give an overview on the research progress of self-assembled bionanocomposites and artificial nanocomposites composed of typical biopolymers and nanoparticles, which exhibit dielectric functions and can have promising potential to be used in biological, electronic, and energy storage applications. 7.1 IntroductionDwindling fossil resources and growing environmental concerns have led to increasing need for sustainable solutions. Overdependence on petroleum resources and environmental impact/carbon footprint can be alleviated by biomaterials development using biological resources or more precisely annually renewable resources. Bionanocomposites are formed by the polymer matrix and reinforcing phase, either of them or both based on renewable resources, and show at least one dimension on the nanometer scale. Bionanocomposites have been the subject of extensive research since the last two decades. These efforts have generated environment-friendly applications for many uses, such as for automotive, packaging, and household products, to name some [1]. Multifunctionality is a trend of development to expand the applications of bionanocomposites.Dielectric bionanocomposites can be utilized for various applications such as conductive elements, heating devices, electromagnetic interference, supercapacitor, shielding and antimicrobial elements, and bio-applications like those of tissue scaffolds for the replacement or restoration of damaged or malfunctioning tissue because a variety of tissue respond to electrical stimulation [2]. On the other hand, an accurate and comprehensive description of structures is of vital importance for the development of high-quality bionanocomposites, which is, however, very difficult because of their nature. Electrical conductivity depends on the micro-and macroscopic states of the composites and gives information on the interaction of individual components inside. Determining the electrical properties of a material is therefore one of the most convenient and sensitive methods for studying the structures of materials [3, 4]. The dielectric properties of bionanocomposites depend on the nature of biopolymer matrix and filler particles, the dimension (mainly include length-to-diameter or aspect ratio) and content of filler particles, and the interfacial characteristics. These issues are taken into consideration in this chapter when reviewing the dielectric performance of bionanocomposites. © 2017 by Pan Stanford Publishing Pte. Ltd.

To help bridge the gap between the science lab and commercial production there is a need for a better understanding of how new bio-based materials are perceived by users. The aim of the studies in this paper was to identify the material expression, sensorial properties and semantic dimensions of a group of pulp-fibre reinforced composites that are still in the research phase and how these relate to other, better-known materials already on the market. The studies involved 21 different materials, divided into different material groups such as metals, solid woods, wood fibre materials, plastic and fibre-reinforced composites in which the pulp-fibre reinforced composites were included. The materials were evaluated for meaning in a product semantic study and for sensory perception in a sensorial study. The results of the semantic study gave two underlining dimensions explaining most of the variations between the materials, Quality and Naturalness. These dimensions also had strong correlations to some of the sensorial properties. The results indicate that the pulp-fibre reinforced composites were not perceived as having high quality or expressing naturalness. They were hard to distinguish from the plastics in the study. The implications for further research and material development are discussed.

Knowledge about consumer perception and preferences on solid wood, wood-based panels, and wood-based composites is important for product development and marketing. The aim of this study was to identify attributes and associations that people use to describe different types of wood materials and to explore how they relate to preferences. The study involved nine samples that were evaluated with the Kelly’s repertory grid technique and content analysis. Based on respondents’ answers, 19 core categories reflecting sample attributes were extracted. General preferences for each sample were also recorded. Principal component analysis generated two factors describing 1) naturalness, wood-likeness, softness, unprocessed origin, living, pleasant, and high value; and 2) solid and homogeneous impression. A third, preliminary factor included categories describing irregular pattern, sleekness, and smoothness. The wood samples were most liked, whereas composites and panels were not appreciated. Preferred core categories were naturalness, wood-likeness, smoothness, living impression, and value. The least liked core categories were processed, hard, and high weight. The implications of the results for product development and marketing are discussed. © 2008 by the Society of Wood Science and Technology.

Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 °C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material's function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 °C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 °C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 °C for 100 h.

This study focuses on the effects of cellulose content and cellulose morphology on the structural and mechanical properties of PP/cellulose fibre composites. A detailed structural characterisation was performed, including SEM-BEI analysis of fibre spatial distribution and X-μCT analysis of fibre orientation. The results indicated that the fibres were well-dispersed and oriented mostly along the main direction of the PP/cellulose test specimen. Based on light microscopy it was found that the cellulose fibres acted as nucleators in the PP matrix. By use of DSC it was shown that addition of cellulose fibres increased both the crystallinity and T_c. The increased crystallinity is mainly a result of the transcrystallinity formation. The tensile properties of the composites were affected by the fibre dimensions and the fibre concentration. The long fibres yielded the highest increase of Young's modulus. Elongation at break was mostly affected by the fibre concentration. The results thus indicate that there is a major potential for improving the mechanical properties of fibre-reinforced composites, provided an adequate concentration of fibres is applied.

In moving towards a cellulose-based society, interdisciplinary effort is required as it is at this interface that new ideas are found and can grow. New bio-based materials will play a key role but getting them into the marketplace is not always straightforward. Many options are available both for sourcing and for producing composite materials from wood-based cellulose and poly-lactic acid (PLA). Depending on how the material is processed, a multitude of properties can be generated. The main goal with this work was to attempt to reduce the research-To-market gap. This was done by testing a new way of working together where we bundled innovation-oriented projects and research-oriented projects around the theme of material experience. We then systematically worked with material demonstrators. In this article, we exemplify the results by focusing on one research-oriented project that did not at the outset have a market context and on one innovation-oriented project with clear market requirements. In addition to introducing a new concept in bundling research-oriented and innovation-oriented projects, this paper contributes several practical examples of what material demonstrators can do. We also present an application and analysis of Moultrie’s extended Science-Technology-Application-Market (STAM) model to analyze the material demonstrators and design phases of the bundled projects. We modified the proposed classification with different types of material demonstrators according to how close they are to an actual product segment. Designers and scientists worked together but with different emphasis in each phase.