Plant Based Reinforcements for Thermosets Matrices, Processing and Properties

M. I. ARANGUREN; M.M. REBOREDO

Engineering Biopolymers:Homopolymers, Blends and Composites

Hanser Gradner publications

Lugar: Cincinnati,OH; Año: 2007; p. 193 - 222

INTRODUCTION Natural fibres and woodflour are perhaps the oldest additives utilised in thermoset plastics. Their use dates back to the introduction of Bakelite into the market, in which the fibres were incorporated to phenolics to provide impact resistance, reduce cost and control shrinkage. Bulk fibres with random orientation and no binder (matrix) can have applications as insulating materials and filters. Fibres with random orientation and some binder have applications as fibreboards and medium density fibre panels. Natural fibres included in a polymer matrix lead to composites for potential load-bearing applications. Natural reinforced plastics (NRP) offer an attractive alternative for cost-effective applications; but severe limitations are imposed due to their low strength and modulus. Traditionally, wood-flour filled moulding compounds have been extensively used for products such as pan-handles, electric meter cases, parts of cars. Besides, natural fibre reinforced composites are particularly suited to structural and decorative applications in the transport, marine, offshore and construction industries. The utilisation of cellulose based natural fibres as reinforcement for thermosets in general, can be effectively used in the production of low cost, low weight (due to the low density of the natural fibres) and ecologically friendly composites. The natural fibres are renewable resources, which are abundantly available, especially in tropical areas. On the other hand, their poor dimensional stability, cracking and degradation of mechanical properties because of their moisture sensitivity are the standard problems of these materials. Polymeric materials which will be used as matrices, must be economic, available, easily processed and with low viscosity. One obvious effect of the incorporation of fillers on polymers is a noticeable increment of the viscosity. Then, an increase of energy consumption is expected for some processing methods. The application of natural fibres as reinforcements in composite materials requires, just as for glass fibre composites, a strong adhesion between the fibre and the matrix, regardless of the selected matrix. The processing conditions play, next to the mechanical properties of natural fibres, an important role for the industrial use of these materials. Thermal analysis is an important consideration because processing temperatures involved in composites manufacture approach those where the fibres begin to degrade. The mechanical and other physical properties of the composites are generally dependent on the fibre/filler characteristics, its volume content in the composite, the fibre arrangement or the filler dispersion, the processing method, the selected matrix and the interface/interphase between both components. For special performance requirements, hybrid composites made of natural and conventional fibres can be prepared with desired properties.