Ceramic/polymer composites play a significant role in bone reparations, as their properties are very similar to natural bone tissue. 1) Calcium hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterial belongs to this group of composites that can be successfully implemented in bone tissue reparation due to their osteoconductive and biocompatible properties. 2–4) HAp/PLLA consists of a biononresorbable ceramic component (hydroxyapatite, HAp) and a bioresorbable polymer component (poly-L-lactide, PLLA). The structure of the HAp/polymer composite closely imitates natural bone tissues, 5) that enable the successful application of this composite as bone substitute material. However, the work on achieving a better compatibility in mechanical properties is still in progress. Besides biocompatibility, a response from the living organism to an applied implant depends on various factors such as porosity, surface microstructure, elastic modules, compressive strength, etc. 6–8) Addition of biphasic calcium phosphate (BCP) to polymers can significantly improve the polymer bioactivity, 9) while BCP itself can be an exceptional carrier of growth factors which facilitates its wider application in medicine and dentistry. 10) Low content of-tricalcium phosphate,-TCP in BCP assists the rapid bonding of bone substitutes to natural bones via rapid dissolution of-TCP. However, excess content of-TCP in BCP lowers the mechanical properties and chemical stability of bone substitutes. If the BCP component in the composite is highly crystalline then it is bio-nonresorbable and vice versa. 11–14) It can be said that bioresorption is initiated in the amorphous regions of PLLA. Therefore, when BCP is highly crystalline, the time of biocomposite bioresorption depends on the crystallinity/amorphous ratio in PLLA. 15, 16) High-energy mechanical milling is a technique for producing a homogeneous powder, with fine microstructure, by milling a powder mixture. 16–18) The most typical characteristic of mechanical milling is the decreased crystallite size. Some materials become amorphous by milling, while others show the decrease of crystallite size to a minimal value which is characteristic for a given material. 19, 20) HAp or BCP with other bioresorbable polymers has already been studied as well as mechanochemical synthesis of HAp, 21–26) while high energy mechanical processing of composite BCP/PLLA has not been investigated.

This article examines the possible influence of mechanical milling on some properties of BCP/PLLA biocomposite. The influence of the milling time on crystallite size of BCP, on melting temperature, and crystallinity of the polymer has been defined. The influence of the mechanical milling on microstructure evaluation was analyzed by ESEM and TEM analysis. Qualitative stability of the biocomposite during mechanical treatment was defined by IR spectroscopy.