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Abstract

An amorphous polylactic acid polymer having a weight average molecular weight in the range of about 35,000 to 180,000 is described. The polylactic acid polymer composition can be hammer milled without cryogenics result in the form of particles wherein 90% of the particles have particle size of about 250 μm or less and the material has a glass transition temperature of between about 55° C. to about 58° C. and a relative viscosity of about 1.45 to about 1.95 centipoise. The polymer composition can be used to form an aqueous suspension. The material is ideally suited for use in preparing particleboard. A method is disclosed for preparing such polylactic acid polymers. The method involves obtaining an amorphous polylactic acid polymer having a weight average molecular weight of between about 115,000 to about 180,000. Treating the polylactic acid polymer to reduce the molecular weight to between about 35,000 to 45,000 such that it has a glass transition temperature of between about 55° C. and 58° C. and a relative viscosity of about 1.45 to about 1.95. Material can be formed into particles in a commercial hammer mill with bypass such that 90% of the initial mass results in the particles which can pass thru a sieve having a pore size of about 250 μm. During particle board formation the temperature of around 140-140 C being reached to optimally activate the adhesive; Bond strengths and throughput rates of resulting particle boards can be controlled thereafter, with variable combination of particle sizes, adhesive loading and initial moisture content.

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