A pressure-sensitive adhesive (PSA) is an “adhesive that is permanently tacky when dry at room temperature and easily adheres to surfaces under brief, low pressure“. It is usually applied to various substrates and is often used in self-adhesive tapes and labels. A hot-melt pressure-sensitive adhesive is a pressure-sensitive adhesive that is processed from a melt. In general, pressure-sensitive adhesives are based on four components: primary polymeric ingredient, tackifier, plasticizer, and other additives. The primary polymeric ingredient – also called the base polymer – is a cohesion-determining component (cohesion or “internal cohesion: state in which the parts of a substance are held together by primary or secondary valence forces“). It is responsible for the adhesive strength of a pressure-sensitive adhesive.
Economical production of primary polymeric ingredients
The demand for adhesive products based on renewable raw materials has risen sharply in recent years due to the changed awareness of sustainability and environmental protection. The development of bio-based adhesives is becoming increasingly important.
In order to maintain market access for these products and to secure market shares in a timely manner, the economical production of primary polymeric ingredients is essential for companies in the adhesives industry. Since the properties of PLA differ significantly from those of the polymers used in the adhesives industry to date, it is necessary to develop a completely new formulation. The most important groups of primary polymeric ingredients in the pressure-sensitive adhesive market today are polyacrylates and styrene block copolymers.
Fraunhofer UMSICHT produces various PLA-based primary polymeric ingredients on a laboratory scale. The modified polymer backbone should provide the materials with important adhesive elastomeric properties as well as cohesion capability in the desired range. One challenge is the large number of ingredients in the adhesive formulation (tackifiers, plasticizers, and other mixture components). A further factor is the complexity of the possible interactions with the primary polymeric ingredient.