Preparation of hybrid poly(lactic acid)/flax composites by the insert overmolding process: Evaluation of mechanical performance and thermomechanical properties

Abstract

This article presents research into the development of a new type of composite materials prepared with the use of the overmolding method. The overmolded insert for the tested samples was in the form of composite prepreg. Poly(lactic acid) (PLA)/flax laminate was prepared by the compression molding technique from the commingled fabric. Two types of materials were used during the injection molding stage: pure PLA and PLA/harl composite prepared with 20 wt% of the flax harl particles. Harl straw is a waste byproduct of the flax fiber manufacturing process. All samples were subjected to a detailed analysis of their mechanical properties, dynamic thermomechanical analysis (DMTA), and structure observations. The reinforcing efficiency of the used prepreg overmolding procedure was found to be very high. In addition to the significant increase in sample modulus, the most favorable improvement relates to impact test results. Most of the conducted studies confirm that high adhesion occurs between the composite insert and the injection‐molded material, which confirms the effectiveness of the used methodology.

Development of Toughened Flax Fiber Reinforced Composites. Modification of Poly(lactic acid)/Poly(butylene adipate-co-terephthalate) Blends by Reactive Extrusion Process

“…Unfortunately, the validation of the obtained results is quite a difficult issue, while in the previous research for PLA-based laminates, the authors rarely referred to the thermomechanical properties like HDT or Vicat, sometimes indicating low values (≈ 60 °C) similar to amorphous PLA varieties [ 85 ]. Other studies showing the thermal resistance above 100 °C, and suggest a significant influence of the fiber content [ 71 , 86 ]. It does not change the fact that our research clearly suggests that the PBAT addition causes visible decrease of the composite heat resistance, but the scale of the reduction is still acceptable and the obtained properties are very good.…”

“…The production of composite laminates based on PLA resin has not been the subject of intensive research, so far, but the appearance of this type of materials on the market indicates an interesting trend in the use of biopolymers The use of PLA as a matrix for composites and laminates was already investigated in case of ramie fibers [ 60 , 61 ], bamboo [ 62 , 63 ], cotton [ 64 , 65 , 66 ], kenaf [ 67 ] or flax [ 26 , 68 , 69 , 70 ]. The use of flax fiber (FF) reinforcement was for us the most promising concept, since the reinforcing efficiency for already investigated PLA/FF composite systems was very high, which was confirmed in many studies [ 68 , 71 , 72 , 73 , 74 ].…”

A Novel Manufacturing Concept of LCP Fiber-Reinforced GPET-Based Sandwich Structures with an FDM 3D-Printed Core

“…However, it still does not come close to the results obtained by polymer laminates [ 30 , 31 , 32 ]. Therefore, one of the latest trends in overmolding technologies is the use of composite prepregs as inserts placed inside the mold’s cavity [ 33 , 34 , 35 , 36 , 37 ]. After joining the prepreg with the injection molded material, the properties of the obtained part combine the strength characteristic of reinforced laminates and the possibility of shaping the complex geometries that characterize the injection molding technique.…”

“…After the glass transition temperature is exceeded, the mobility of the polymer chains enables the diffusion process to take place; in the case of other thermoplastic materials (polyolefins and polyamides), it is necessary to melt the bonded layer. The high weldability of materials such as PET, GPET, or PLA copolymers has already been used in previous research on overmolding composite prepregs [ 35 , 37 , 54 ]. The permanent connection of both components of the hybrid part took place without the need to use dedicated heating systems for the joined surface.…”

The Influence of Sub-Zero Conditions on the Mechanical Properties of Polylactide-Based Composites

“…Even though conventional fillers such as glass fiber can be successfully embedded in PLA matrix [ 25 ], environmentally friendly fillers are the most common choice, as they allow us to obtain a fully bio-based biodegradable material. Numerous examples of polylactide-based composites reinforced with sisal fibers [ 26 , 27 ], flax fibers [ 28 , 29 , 30 , 31 ], wood [ 23 , 32 ] or hemp [ 33 ] can be found in the literature, but an even more sustainable solution is the application of the so-called waste fillers, i.e., the by-products mainly from agriculture or food industry such as nutshells, husks, seeds, waste fibers [ 9 , 34 , 35 , 36 , 37 , 38 ] and more. The application of waste fillers is not only in line with the idea of Circular Economy [ 5 , 39 ], but oftentimes improves different properties of the resulting composites [ 40 , 41 ].…”