L.A. Granda

Bleached kraft softwood fibers reinforced polylactic acid composites, tensile and flexural strengths

An increasing ecological consciousness in society has led to the development of materials with a lower environmental impact. PLA is a biodegradable polymer with higher mechanical properties than polypropylene. There are a few important works published about PLA-reinforced biocomposites in which satisfactory results were obtained. A good interphase generation when around 30% reinforcement percentages are extruded is, nowadays, an unsolved fact. The main objective of this study is obtaining PLA biocomposite with a good interphase that allows a satisfactory improvement on tensile and flexural strength. Pine bleached fibers were prepared and shred with 1/3 and 2/3 of diglyme, in order to avoid the formation of hydrogen bonds between the cellulose fibers. Afterwards, the composites materials have been obtained through kinetic mixing and injected into the shape of standard specimens in order to submit them to tensile and flexural test. The results show that the addition of diglyme helps the formation of hydrogen bonds between the reinforcement and the PLA. This is achieved by avoiding the generation of hydrogen bonds between the cellulose fibers. Only the fiber treated with 2/3 of diglyme followed a lineal and positive dependence of the tensile strength when increasing reinforcement content was added. The same composite materials also showed a linear behavior of the flexural strength against the fiber content. The intrinsic tensile and flexural strength of the fibers were also modeled. Although the obtained tensile and flexural strength were promising, more research is needed to ensure good results for higher than 30% fiber contents.

Cellulose polymer composites (WPC)

Abstract Cellulose polymer composites have been studied with great results in enhancing mechanical properties compared to matrices. The following chapter gives a global vision of all the components involved in wood plastic composite formulation: the polymer matrix, natural fibres and additives. It makes a special remark to the interface wood–polymer behaviour and how it influences the desired mechanical properties through modelling using a well-known rule of mixtures (RoM) and the Kelly Tyson model. It also explains the main manufacturing process for wood plastic composites, which can be found in the market, and their basic process parameters. Finally, some remarks of future trends are exposed.