The two-way shape memory behaviour of semicrystalline networks was investigated on systems based on poly(e-caprolactone) featuring significantly different network architecture. Crosslinked poly(e-caprolactone)s were prepared by thermal curing from methacrylic end-capped linear chains having various methacrylation degrees. By conveniently reducing the methacrylation degree, the crosslink density of cured materials was varied over a range of one order of magnitude, leading to comparable changes in the material compliance in the rubbery region, but only to moderate variations in melting and crystallization temperatures (T m and T c ) and in the crystallinity content. When subjected to constant non-zero stress and to cooling-heating cycles from above T m to below T c , the materials undergo a reversible two-way elongation-contraction effect, whose extent depends on material structure and applied stress. The structural changes in the crystalline phase accompanying the cooling-induced elongation were studied through differential scanning calorimetry and X-ray diffraction analyses. The elongation process involves different contributions of entropy-and crystallization-driven processes, whose amounts were investigated as a function of the loading conditions and the molecular architecture. The role of the network density towards a controlled two-way response is evidenced, showing that a proper value of the crosslink density has to be identified to maximize the two-way elongation capabilities.

Weight reduction and material substitution are increasing trends in the automotive industry. High pressure die casting (HPDC) is the conventional casting technology for the high volume production of light alloys; it has recently found wide application in the manufacturing of critical components, such as complex and thin geometry automotive parts. However, the major restriction of this affordable technology is the difficulty to design and realize hollow sections or components with undercuts. An innovative way to further increase the competitiveness of HPDC is to form complex undercut shaped parts through the use of new lost cores that are able endure the high pressures used in HPDC. This paper investigates the use of innovative ceramic lost cores in the production of a passenger car aluminum crossbeam by HPDC. Firstly, process and structural simulations were performed to improve the crossbeam design and check the technology features. The results led to the selection of the process parameters and the production of some prototypes that were finally characterized. These analyses demonstrate the feasibility of the production of hollow components by HPDC using ceramic cores.

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The "two-way" shape memory response of semicrystalline networks was studied on poly(epsilon-caprolactone)-based systems, crosslinked by thermal curing of methacrylic end-capped linear chains. By changing the methacrylation degree of the precursors, it was possible to vary the network density over one order of magnitude, without any remarkable change in their transition temperatures and crystallinity content. When subjected to a constant stress and to a cooling-heating cycle from above T-m to below T-c, the materials display reversible two-way shape memory capabilities, consisting in a cyclic elongation-contraction effect, which involves significant variations of strain. Two different cooling induced elongational processes are evidenced, one due to entropy elasticity and the other to a crystallization driven effect. The amount of elongation that may be achieved depends on the network density and on the applied stress, and it is maximized for systems with a crosslink density that allows to exploit both the entropy-and the crystallization-induced effect