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The objective of this study was to synthesize a new bifunctional photoinitiator by the reaction between 1‐hydroxy‐cyclohexyl‐phenyl‐ketone and 3‐isocyanato propyl trimethoxysilane (ICPTMS) and examine its capability in the photoinitiation process comparing it with the unmodified photoinitiator. This new photoinitiator also acts as a coupling agent for inorganic and organic phases. Therefore, its effect on the physical and mechanical properties of UV‐curable transparent organic‐inorganic hybrid coatings was investigated. The presence of the new bifunctional photoinitiator and TEOS, increased the abrasion resistance and also improved the hardness of the polymeric films.magnified image

Isocyanate‐based graphene oxide‐containing polyimide foams were synthesized by a semi‐prepolymer method. In this method, while the first solution containing pre‐polymer was derived from pyromellitic dianhydride and excess polymethylene polyphenylene isocyanate (PM200), the second solution contains dianhydride derivatives, water, catalysts, surfactants, and graphene oxide. PIFs were prepared with 0%, 0.25%, 0.50%, 0.75%, and 1% graphene oxide by weight, respectively. PIFs exhibited a minimum side reaction and urea generation was not seen for all PIFs instead of imide bonding. The addition of graphene oxide (GO) leads to a more close‐packed structure. Therefore, crosslinking density and thermal stability of graphene oxide‐containing polyimide foams increased. Upon the addition of 1% GO, almost seven times higher compression strength was obtained compared to neat PIFs. Also, LOI values supported the theory that thermally stable and flame retardant PIFs can be synthesized via the isocyanate‐based process with GO.

Son yıllarda inorganik partiküllerle takviyelendirilmiş polimer matrisli kompozitler yaygın bir şekilde kullanılmaktadır. Yapılan çalışmaların birçoğu, polimer malzemelere inorganik yapıların ilavesiyle elde edilen hibrid malzemeler üzerine yoğunlaşmıştır. Bu çalışmada, bor nitrür partikül takviyeli vinil ester kompozit malzemeler üretilmiştir. Matris malzemesi olarak vinil ester reçinesi kullanılmıştır. Takviye malzemesi olarak ise ortalama 70 nm boyutlarında olan hegzagonal bor nitrür partikülleri kullanılmıştır. Farklı oranlarda üretilen bor nitrür takviyeli vinil ester kompozit numunelerin çekme dayanımı, eğilme dayanımı, darbe dayanımı, aşınma dayanımı ve sertlik özellikleri incelenmiştir. Test numunelerini hazırlamak için kalıp malzemesi olarak silikon tercih edilmiştir. Reaksiyon başlatıcı olarak %50 aktif metil etil keton peroksit, hızlandırıcı olarak ise % 6'lık kobalt naftalat kullanılmıştır. Partiküllerin homojen dağılımını sağlamak ve topaklanmayı engellemek için partikül miktarının 5 katı oranında MEG (mono etilen glikol) ilavesiyle elde edilen karışım, ultrasonik karıştırıcı içerisinde 30 dakika karıştırılmıştır. Vinil ester reçine içerisine bor nitrür ilavesi işlemine ağırlıkça % 0,5 oranından başlanmış ve % 2'ye kadar devam edilmiştir. Elde edilen kompozit malzemenin darbe ve sertlik değerlerinde artış görülmüştür. Çekme, % uzama ve eğilme özelliklerinde azalma gözlemlenmiştir. Aşınma miktarında ise azalma, dolayısıyla aşınma dayanımında artış olduğu görülmüştür.

In this study, the synergistic effect created by adding Graphene (GE) nanoplatelets and carbon black (CB) fillers to the rubber matrix was used to determine the high stretchable sensor properties. GE and CB-filled rubber nanocomposite (HcN) strain sensors have been shown to detect and trace crack initiation and crack propagation of different sizes under cyclic loading. Tests were performed with four different crack sizes (0, 2.5, 5, and 10 mm) at five different strain levels (0%, 5%, 10%, 15%, and 20%) to determine the strain sensing performance of the specimens. The electrical response of HcNs under loading was measured with the four-point probe technique and recorded with a high-performance data acquisition system. The progression of external cracks created by scalpel on HcNs was examined by measuring electrical resistance changes caused by cyclic strain loading between 0% and 20%. The electrical response of 4 phr and 8 phr filled HcNs behaved qualitatively similar to each other, while 1 phr filled HcNs showed a significantly different response in terms of quality and quantity. In 4 phr GE-filled specimens, the resistance increase was changed steadily depending on the crack length, and unstable conditions occurred at 5 and 10 mm crack lengths at 1 and 8 phr GE filler ratios. The flexible and stretchable elastomer-based conductive strain sensing sensors, developed with the synergistic interaction of well-dispersed carbon-based fillers in the matrix, can detect and record damaged conditions caused by cyclic loading in many application areas.