Content: Since hundreds of years, tanners share the opinion that hides from different cattle breeds lead to varying leather qualities. Especially European hides from the alpine region (e. g. Simmentaler or brown origin) are preferred by tanners. These leathers feature a higher thickness, a maximum utilisation induced by a minor thickness difference over the whole area and a lower tensile strength in contrast to leathers from other breeds. However, are these alpine hides better because of their breed affiliation or because they are kept in special regional conditions? It is known that, besides the breed, also other factors can influence the rawhide and leather quality like age, gender, nutrition and climate conditions. In addition, present dairy and beef cattle are high-performance cattle by breeding, which leads to more crossbreeds than 100 years ago. Our intention was to find out, whether leather quality nowadays is still a function of breed or not. For that purpose, 40 rawhides from four different cattle breeds (Angus, Charolais, Simmentaler, Limousin) were collected from the Saxon region. From each breed, five male and five female rawhides were collected. The age of each individual was restricted to two years. All 40 rawhides were tanned with the same technology for furniture leather. Leather quality was characterized by determining chemical and physical parameters. Chemical parameters included collagen content, fat content and ignition lost (DIN 181218). The physical parameters were tensile strength (DIN EN ISO 3376), elongation at break (DIN EN ISO 3376) and stitch tear resistance (DIN EN ISO 23910). The analyses revealed that the chemical parameters were identical for all examined breeds. For this reason, the chemical composition of a cattle skin is irrespective of breed origin. The tensile strength of the leathers showed only a small significant difference between Angus and Limousin (p= 0.05). Leathers from Limousin hides showed significantly different elongations at break compared to Angus, Charolais and Simmentaler. The stitch tear resistance varied in nearly all breeds. Significant differences were detected between all breeds except between Angus and Charolais as well as Angus and Simmentaler. Plotting the measured physical values against gender or age of the individuals showed no correlation. In summary, only minor differences between the cattle breeds were found. But this tendency must be confirmed by a larger quantity of test individuals. For this purpose, an analysis is planed with 100 individuals from different breeds and crossbreeds. Take-Away: Many tanners share the opinion that hides from different attle breeds lead to varying leather qualities. We found only minor differences of the physical parameters between the cattle breeds with a random sample of 10 individuals per breed. To confirm this tendency, an analysis is planed with 100 individuals from different breeds and crossbreeds.

Cette étude vise à mieux comprendre les mécanismes physiques à l'origine des propriétés mécaniques et des propriétés ultimes des caoutchoucs renforcés. Des échantillons de caoutchouc naturel dans lequel sont dispersés des agrégats de Silice précipitée ou de Noir de Carbone et vulcanisés au Soufre ont étés mis en oeuvre. Les principaux paramètres étudiés sont la densité de réticulation et l'interface charge-caoutchouc modifiée au moyen de différents traitements de surface de silice. L'impact des charges et du type d'interface sur les propriétés mécaniques dans le domaine des faibles déformations (effet Payne) et des grandes déformations est présenté. Le phénomène de cristallisation sous étirement dans le caoutchouc naturel est étudié par diffraction des rayons X in-situ au cours d'essais de traction quasi-statiques ou d'essais dynamiques couplés à un système d'acquisition stroboscopique. Nous montrons une corrélation des mesures du module, du degré de gonflement à l'équilibre, de l'orientation des chaînes mesurée par diffusion de rayons X et de la densité de réticulation mesurée par RMN dans le caoutchouc naturel non chargé. Dans le caoutchouc naturel renforcé, les corrélations établies à l'aide de ces mêmes mesures permettent de préciser les mécanismes de renforcement aux faibles et aux grandes déformations. Enfin, la résistance à la déchirure est évaluée en géométrie cisaillement pur sur les matériaux non-renforcés et renforcés. Les effets du type d'interface, de la densité de réticulation et de la vitesse d'essai sur la résistance à la déchirure sont présentés. Nous discutons également les profils de déformation locale obtenus par corrélation d'image / This study aims at better understanding the physical mechanisms responsible for the mechanical and ultimate properties in reinforced rubber materials. Sulfur vulcanized samples made of a Natural Rubber matrix in which aggregates of precipitated Silica or Carbon Black are dispersed have been manufactured. The main control parameters are the crosslink density and the filler/rubber interactions through different silica surface treatments. The effect of fillers and interface type on the mechanical properties in the small strain regime (Payne effect) and large strain regime is presented. X-ray diffraction experiments have been performed to study the phenomenon of strain-induced crystallization (SIC) both during quasi-static tensile tests and dynamical tests coupled to a stroboscopic acquisition device. Mechanical measurements have proved to correlate fairly well to the crosslink density measured by NMR, to equilibrium swelling degree and to the average chain segment orientation measured by X-ray scattering in unfilled natural rubber in agreement with the rubber elasticity theory. In reinforced materials, the correlation of those different measurements of local chain stretching give new insights on the reinforcement mechanisms at small and large strain. Tear experiments have been performed on Pure Shear pre-notched unfilled and filled samples. The influence of interface type, crosslink density and test drawing speed on tear resistance are presented. Local strain profiles obtained from digital image correlation and the crystallized fraction profiles from in-situ X-ray diffraction are also discussed