Recent studies on different modification technique to reduce moisture absorption rate of biocompositesa.
| Biocomposites | Modification | Test duration and standard | Results | Ref. |
|---|---|---|---|---|
| Jute/GF/polyester | Inter-layer vs. intra-layer stacking configuration | Saline water for 30 days | Different stacking lamination configuration affecting the properties of the biocomposite significantly | 269 |
| Inter-layer configuration of jute and GF presents the least resistance to moisture compared to the other configurations studied | ||||
| Lyocell/PLA | Silane (PTMS) | Distilled water immersion at room temp. | Significant improvement on water resistance properties was observed with surface treatment | 270 |
| Fibre hemp shivs/corn starch | Hot water treatment | Water (24 h), EN 1609, method A | Water absorption and thermal insulation behaviour are related to shiv size and microstructure | 271 |
| Hot water treated fibre hemp shivs improve moisture properties of the biocomposites | ||||
| Rice husk/PLA | Alkali (NaOH), ionic liquid (IL) | ASTM D570-98 72 h | Treated biocomposites showed lower water uptake as compared to untreated biocomposites | 272 |
| Hydrophilic nature of rice husk is reduced and better interfacial adhesion in the biocomposites was achieved after treatment | ||||
| CF/rosin-based epoxy | — | EN 2823:1998, 70 °C/85% RH 168 h (7 days) | CF/epoxy biocomposites exhibited similar water absorbability with traditional CF/epoxy composites | 273 |
| CF/epoxy biocomposites showed good aging resistance behaviour | ||||
| Sisal fibre/PLA | Mercerization | Distilled water immersion for 10 days | 6% NaOH concentration during mercerization treatment yields good mechanical prop. and water resistance of the biocomposites | 274 |
| Hemp/epoxy | — | Climatic chamber at 25 °C, RH – 9%, 33%, 75% and 98% | Hygroscopic expansion was observed with a higher out-of-plane strain in comparison with transverse (and longitudinal) strain | 250 |
| Moisture sorption is associated with orthotropic hygroscopic expansion which is due to the influence of fibre reinforcement distribution and the generation of residual stresses during manufacturing | ||||
| PLA/cellulose/thermoplastic starch | — | ASTM D570, Distilled water 10, 20, 30, 60 and 240 min | Reinforcement of PLA in cellulose/thermoplastic changed the water absorption rate and increased the water barrier properties of the biocomposites | 275 |
| Jute/PLA | — | Deionized water at 50 °C, 100 : 1 water to samples ratio | Water diffusion into biocomposites during the hygrothermal aging test causes interface failure, which results in matrix embrittlement and reduction of mechanical properties | 276 |
| Wood flour/PLA | Tanalith E – Copper treatment, MAPE coupling agent | ASTM D570, 2 and 24 h | Treated wood flour/PLA biocomposites absorbed more water than untreated wood flour/PLA biocomposites | 277 |
| Addition of MAPE coupling agent in biocomposites decreased the water absorption |
a
Abbreviation: PTMS: phenyltrimethoxysilane; IL: 1-ethyl-3-methylimidazolium acetate; CF: carbon fibre; RH: relative humidity; MAPE: maleic anhydride grafted polyethylene.