Physico-mechanical and thermal properties of epoxidized natural rubber/polylactide (ENR/PLA) composites reinforced with lignocellulose

Journal of Thermal Analysis and Calorimetry September 2016, Volume 125, Issue 3, pp 1467–1476 | Cite as Physico-mechanical and thermal properties of epoxidized natural rubber/polylactide (ENR/PLA) composites reinforced with lignocellulose AuthorsAuthors and affiliations Anna MasekKarolina DiakowskaMarian Zaborski Open Access Article First Online: 14 July 2016 1.5k Downloads 7 Citations Abstract The aim of the study was to prepare elastic composites of epoxidized natural rubber with polylactide that was reinforced with lignocellulose. To improve the functional properties of an ENR/PLA blend, we used lignocellulose modified with silanes and silica. The addition of silanes, particularly U511-tetraethoxysilane, improved the strength characteristics of ENR/PLA composites, which were primarily shown as a considerable improvement in the elasticity of these materials. According to the thermogravimetric analysis and its derivative and differential scanning calorimetry curves for lignocellulose before and after modification with silane, changes were verified in its thermal profiles. Based on the tests of accelerated ageing, it is observed that all of the ENR/PLA composites with lignocellulose are characterized by a great degradability. The ageing coefficient (K) and parameters of oxidation induction time (OIT/DSC) show that the modification of lignocellulose with silanes increases the resistance of these materials to the action of climatic conditions, particularly UV radiation at 340 nm. KeywordsLignocellulose Polymer Degradation Polylactide Silane  Introduction Conventional polymeric composites consist primarily of synthetic raw materials. Most of the polymers used do not exist in nature and do not undergo degradation. One can now observe an increase in the number of studies published on the technology of degradable polymeric materials. Biodegradable materials have been produced and used in an increasingly wider range. The properties of all heterogeneous materials are determined by their structures, compositions and interfacial interactions. A direct influence on these components is exerted by synthesizing or modifying the materials used in the manufacturing processes of these materials or their types and origin. One can observe with increasing frequency the return to the use of raw materials from renewable sources [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]. The desirable properties of lignocellulose materials encourage one to apply them to make polymeric composites that are designed for use in many industrial branches. One can observe a growing interest in renewable cellulose, hemicellulose or lignocellulose. Lignocellulose biomass is a fibrous portion of plant materials that is attractive because of its renewable origin and large resources. Lignocellulose fibres have some interesting mechanical and physical properties. The term lignocellulose is used to describe the three-dimensional polymeric composites that plants create as structural materials. It is composed of variable parts of cellulose, hemicellulose and lignin [12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]. Renewable raw materials are also used to produce monomers and polymers. The basic biodegradable polymers include PHA, PLA, PHB, PHBV, PGA, PD, PHH, PBAT, PBS, PBSA, PHBH, PVOH, PCL, PES, PKA, BAT and TPS. Among the mentioned polymers, polylactide (PLA) plays a dominating role and constitutes approximately 40 % of all biodegradable polymers. This polymer is called doubly green because it is both biodegradable and is obtained from renewable sources [25, 26, 27, 28, 29, 30]. Materials and methods Reagents The subject of the study, polylactide, was obtained from Nature Works™ (USA) (40phr). Epoxidized natural rubber (Epoxyprene 50; 50 mol% epoxidation) was obtained from Kumpulan Guthrie Berhad, Malaysia (60 phr). Dodecanoic acid (1 phr) 97 % obtained from Sigma-Aldrich was used as a cross-linking agent; 1,2-dimethylimidazole (0.5 phr) was used as a cross-linking catalyst (98 %). Lignocellulose (LC) (Lignocel C 120/HB 120) was characterized by length of fibre 70–150 μm, from Rettenmaier Poland Sp. z o.o. Silanes obtained from Unisil Sp z.o.o. (Poland): U13 (3-aminopropyl)triethoxysilane, U15 [3-(2-aminoethylamino)propyl]trimethoxysilane, U511-tetraethoxysilane, U611-vinyltrimethoxysilane, were used as modificators (4 phr) of lignocellulose. Symbols Polylactide—PLA; epoxidized natural rubber—ENR; lignocellulose—LC, filler; silica Aerosil 380—A380, filler; polylactide/epoxidized natural rubber blend—ENR/PLA; oxygen induction time—OIT (min); a.u.—arbitrary unit; tensile strength—TS (MPa); elongation at the break—EB (%); energy–E (J g−1); ageing coefficient—K (a.u.). Methods for modification of fibres and preparation of ENR/PLA blends with modified lignocelluloseMechanochemical treatment of lignocellulose with silane coupling agents Samples of lignocellulose fibres modified by using silane were obtained by intergrinding the s (...truncated)