Ultra‐flexiblePLA‐based blends for the manufacturing of biodegradable tamper‐evident screw caps by injection molding

Abstract

Mono‐material in the manufacturing of oil‐based plastic bottles has been so far not considered because of the poor flexibility of polyethylene terephthalate (PET). The undercuts of PET caps (i.e., the threads of the screw caps) would be torn‐off during the ejection step of the injection/compression molding processes that are commonly used to fabricate them. In this respect, the present work deals with the design and development of innovative biodegradable polyester‐based blends with high flexibility, intended for the manufacturing of screw‐cap, being this element the most critical in the implementation of the complete bottle. The blend is based on polylactic acid and it is tailored for injection molding of tamper‐evident screw plastic caps by the addition of another biodegradable polyester, that is, polybutylene adipate‐co‐terephthalate. The effect of the addition of a barrier agent, polyvinyl alcohol, on the overall behavior of the blends was also studied in the perspective of the implementation of caps featuring barrier properties against water vapor and oxygen. The same material could be, however, easily tailored for the fabrication of the bottle body and printed label to get to the mono‐material bottle. Twin‐screw corotating extrusion of the compound, injection molding of the plastic material for the fabrication of the screw caps, and evaluation of the thermophysical and mechanical properties of the screw caps are hereinafter discussed. The biodegradable polyester‐based blends are found to be suitable for injection molding of the tamper‐evident screw caps, exhibiting adequate flexibility during ejection from the mold. The screw caps can also boast appreciable mechanical strength and impact resistance as well as good thermal stability.

Evaluation of Mussel Shells Powder as Reinforcement for PLA-Based Biocomposites

“…However, it presents some drawbacks that must be overcome (low thermal resistance, brittleness, low toughness, slow crystallization rate) [ 19 ]. To achieve good values of flexibility and ductility, many attempts have been made and with various methodologies [ 20 , 21 , 22 ]. The addition of PBAT to PLA has been widely investigated in literature [ 23 , 24 , 25 ], also in different temperature conditions [ 26 ], and tailored formulations have been developed and tested in our research group for several applications [ 27 ].…”

Effect of a Bio-Based Dispersing Aid (Einar® 101) on PLA-Arbocel® Biocomposites: Evaluation of the Interfacial Shear Stress on the Final Mechanical Properties

“…Among the biodegradable matrices available on the market, poly (lactic) acid (PLA) is the most attractive thanks to its biodegradability, renewability, mechanical properties (Young modulus of about 3 GPa, tensile strength between 50 and 70 MPa, elongation at break around 3–6% and impact strength close to 2.5–3 kJ/m 2 [ 13 , 14 ]) and low production cost if compared to other biodegradable materials [ 15 , 16 , 17 ]. These features make PLA adaptable in many areas of Engineering and Technology [ 18 , 19 , 20 , 21 ]. However, there are some PLA drawbacks (such as low flexibility, excessive brittleness, low thermal stability, low crystallization rates) that highly restrict its possible applications [ 22 , 23 ].…”