polymerguru

Today's KNOWLEDGE Share: 𝐖𝐡𝐲 𝐝𝐨 𝐰𝐞𝐥𝐝𝐬 𝐜𝐫𝐚𝐜𝐤? - 𝗔 𝘄𝗲𝗹𝗱𝗶𝗻𝗴 𝗰𝗿𝗮𝗰𝗸 is fracture-type linear imperfection having a sharp tip with a higher length and very small width. - Welding cracks can appear in weld deposits, heat-affected zones (HAZ), and base material. - They occur once the localized stresses exceed the ultimate tensile strength of the base metal. - 𝗜𝗻𝗶𝘁𝗶𝗮𝗹 𝗖𝗿𝗮𝗰𝗸𝗶𝗻𝗴 usually starts at stress concentrations due to other defects or sharp notches (notches work as stress concentration) in the nearby area. - These stresses can be residual stresses caused by the welding or stresses applied due to service or other external loading. - 𝗥𝗲𝘀𝗶𝗱𝘂𝗮𝗹 𝘀𝘁𝗿𝗲𝘀𝘀𝗲𝘀 in welding are caused by weld solidification and thermal expansion properties of the metal. - In welding cracks, there is little plastic deformation as most of the cracks either occur due to high hardness or Stress. Sources:weldguru.com/www.materialwelding.com Visit MY BLOG http://po...

ECHA’s Committee for Socio-Economic Analysis (SEAC) adopts its final opinion supporting a gradual ban on per- and polyfluoroalkyl substances (PFAS) in firefighting foams. The restriction could reduce PFAS emissions into the environment by around 13 200 tons over 30 years. Proposed Restriction to Review Alternatives: SEAC considers that the proposed restriction on the placing on the market, use and formulation of PFAS in firefighting foams is the most appropriate EU-wide measure to address the identified risks. This takes into account available alternatives and the balance between the restriction’s benefits and costs to society. These conclusions follow an opinion on the risks adopted by ECHA’s Committee for Risk Assessment (RAC) in March 2023. SEAC suggests, however, that a review of available fluorine-free alternatives for sites that produce, treat or store dangerous substances (covered by the Seveso Directive) and those neighboring them is carried out before the end of the 10-year tr...

Today's KNOWLEDGE Share: Petrochemical Historical Timeline 3: 1920s-1940s A busy era for petrochemicals with nylon, acrylics and polyester materials developed,as well as new compounds derived from oil-refining by-products entering the market.Other successful materials included polystyrene,polyvinyl chloride (PVC) and polyethylene. Nylon, acrylics and polyester developed for a wide range of uses, such as clothing, sports gear, industrial equipment, parachutes and plexiglass. 1920 German chemist Hermann Staudinger recognised that polystyrene is made up of many styrene molecules joined together in a chain. 1925 US oil production exceeded 1 billion barrels. 1925 Synthetic fuels pioneered with the development of the Fischer-Tropsch process by German researchers Franz Fischer and Hans Tropsch. Coal, biomass or natural gas could now be converted into synthetic fuels. 1926 IG Farben acquired patent rights to the Bergius hydrogenation process. Carl...

The first RNA-guided DNA-cutting enzyme found in eukaryotes, Fanzor could one day be harnessed to edit DNA more precisely than CRISPR/Cas systems. A team of researchers led by Feng Zhang at the McGovern Institute for Brain Research at MIT and the Broad Institute of MIT and Harvard has uncovered the first programmable RNA-guided system in eukaryotes — organisms that include fungi, plants, and animals. In a study published today in Nature, the team describes how the system is based on a protein called Fanzor. They showed that Fanzor proteins use RNA as a guide to target DNA precisely, and that Fanzors can be reprogrammed to edit the genome of human cells. The compact Fanzor systems have the potential to be more easily delivered to cells and tissues as therapeutics than CRISPR-Cas systems, and further refinements to improve their targeting efficiency could make them a valuable new technology for human genome editing. CRISPR-Cas was first discovered in prokaryotes (bacteria a...

Today's KNOWLEDGE Share: #Foam cores are widely used in composite materials for their lightweight and high-strength properties. The finishing techniques applied to foam cores play a crucial role in enhancing their functionality and overall performance within composite structures. As you can see in this picture, there are many different finishes that can be applied to a foam core: including grooved, perforated, grit, double cut. Grooved Finish: Adding grooves to the surface of foam cores creates additional surface area, which improves the bonding and adhesion between the core and the composite layers. The increased contact area also enhances the mechanical interlocking and overall strength of the composite structure. Grooved finishes are commonly used in applications requiring high bond strength, such as aerospace components and marine vessels. Perforated Finish: Perforating foam cores involves creating a pattern of small holes or perforations on the core surface. This finishing t...