18Material Science and Technology of Japan, 61（2024）18～22Feb. 2024

Regular Paper
Surface Modification and Plating Adhesion Strength of PLA Polymer
Using Limonene as a Pre-etching Solvent
Ajay DEVRUKHKAR1,2,*, Yuya WAGATSUMA1,2, Fan MO1,2, Katsuhiko TASHIRO1,2,Yasushi UMEDA2, Hideo HONMA2 and Joo-Hyong NOH1,2
1Graduate school of Engineering, Kanto Gakuin University, Yokohama, 236-8501, Japan
2Materials and Surface Engineering Research Institute, Kanto Gakuin University, Yokohama 236-8501,Japan.
Received Sep. 20, 2023; accepted Dec. 14, 2023
Abstract
PLA (polylactic acid) polymer is a sustainable alternative to petrochemical based polymers for various applications. PLA
is biodegradable and recyclable polymer. So, it is considered as an environmentally friendly material. However, when PLA
is exposed to sunlight or moisture for a long time, the PLA properties deteriorates, besides it has low thermal stability.
Although of these negative characteristics, PLA polymer is the preferred choice for manufacturing different parts.
However, plating can overcome these negative characteristics. Pre-treatment (etching) is required on PLA polymer surface
to occur electroless plating. It is known to etch the PLA polymer surface using alkaline treatment. It was believed that
improved adhesion can be achieved through combining the approach of swelling the polymer surface using organic solvent
before etching by alkaline treatment because the organic solvent swells the polymer surface and develops functionalgroups on the polymer surface, thereby it can adsorb more plating catalyst and plates more efficiently. The aim of thisstudy is to determining organic solvent pre-treatment (using along with alkaline etching treatment) effect on adhesion ofplated layer. Limonene was found to be good to use as a pre-etching solvent, as limonene is relatively safe to handle andenvironmentally friendly. Therefore, combined effect of limonene and alkaline etching treatment was used in this study,
besides the modification effect & adhesion strength were investigated. Best results were obtained when using limonene
and alkaline etching treatment together.
Keywords: Organic solvent sensitizer, polymer surface oxidation, Limonene, PLA (Polylactic acid)

1. Introduction

low price [1-3]. Yet, when PLA is exposed to sunlight orPolylactic acid (PLA) is biodegradable and highly useful

moisture for a long time, the PLA properties deteriorates, and it

polymer derived from renewable resources like corn and sugar

has low thermal stability. However, plating can overcome thesebeets, with a high content of starch, which is converted into

negative characteristics. Also, the low temperature resistance ofpolylactic acid during treatment. PLA possesses promising

PLA polymer has some challenges to the advancement of apotential in different fabrication processes, i.e., 3-D printing,technology for its metallisation. The thermal stability of PLA

sheet extrusion, injection moulding, film forming, blow

polymer depends on the molecular weight and crystalline phase.

moulding, and thermoforming etc. Low-cost PLA products are

It is known that crystalline form of PLA polymer has a melting

used in many applications such as packaging, films, fibres, andpoint around 180°C and amorphous PLA has a glass transitionin making of moulded articles. The use of PLA polymers in thesetemperature (Tg) of 50–57°C. Important surface pretreatment forapplications is not only due to its biodegradable properties andthe good adhesion of the deposited metal is the process of

being made from renewable resources. PLA is being usedetching [4-7]. It was believed that including the sensitization

because it works very well and provides excellent properties at atreatment before the etching treatment can improve the adhesion*Corresponding author: (d20J8005@kanto-gakuin.ac.jp)(18)