ABSTRACT
The evaluation of Hot-Gas and Heated-Tool weldments of Polypropylene/Bone composite was conducted. The composites were formulated by incorporating up to 30% by weight of calcined cow bone powder at an interval of 5% and -75μmsieved size was used as reinforcing phase during compounding process. The polypropylene materials (in unreinforced state) and various polypropylene/bone composites were welded, using hot-gas and heated-tool welding processes. Mechanical properties (tensile strength, flexural strength, impact strength and hardness) and physical properties (density, water absorption, degradability and morphology) of polypropylene and polypropylene/bone composite in both unwelded and welded conditions were examined. Results obtained showed increase in density (by 40% at 30% reinforcement); the amount of water absorbed increased as the time of immersion increased. Although the unreinforced polypropylene was saturated after 192 hrs of immersion in water, the reinforced composite's water uptake continued beyond 192 hrs in proportion of filler amount. Similarly, there were marked improvements in mechanical properties in the Unwelded Composite (UWC), which was attributed to the reinforcing ability of the bone. However, relatively lower values were recorded when welded samples were examined. More so, there were drops in tensile strength after 15% (40.91MPa) and 20% (41.54 MPa) in Heated Tool Weldments (HTW) and Hot Gas Weldments (HGW) respectively. On the basis of comparison, these values showed that at 15% reinforcement addition, HTW has strength value 16.70% lower than UWC of the same composition (15% bone), while in composite with 20% of reinforcement, the strength value of HGW was found to be 23.23% lower than UWC of the same composition. Furthermore, flexural strength and hardness witnessed increase as more of polypropylene was replaced by bone powder. Impact energy decreased and then increased; after 10% of reinforcement addition, all but UWC set of samples witnessed drop in their ability to absorb energy on impact as a result of bone additions. These behaviours have been explained in terms of strengthening effect and volume fraction of the reinforcement as well as the effect of welding processes.