Isotactic and syndiotactic polymers are made through specific types of polymerization processes that control the arrangement of the substituent groups on the polymer chain. In isotactic polymers, all substituents are on the same side of the polymer chain, resulting in a highly ordered structure that can crystallize more easily, leading to materials with higher density and melting points. Syndiotactic polymers, on the other hand, have substituents alternating sides in a regular pattern, also allowing some degree of crystallinity but with different physical properties compared to isotactic polymers. The production of isotactic and syndiotactic polymers is usually achieved through stereospecific polymerization, using Ziegler-Natta catalysts or metallocene catalysts. These catalysts are crucial as they allow for the control of the molecular microstructure during the polymerization process, enabling the production of polymers with specific stereochemistry. The choice of catalyst and polymerization conditions (temperature, pressure, monomer concentration, etc.) directly influences the tacticity of the resulting polymer, thereby determining its physical and mechanical properties.

JB Weld is indeed considered a structural adhesive, designed for strong, heavy-duty repairs where a permanent bond is required. It's an epoxy adhesive that can bond a wide range of materials including metals, plastics, and ceramics. Its unique formulation allows it to withstand high temperatures and remain waterproof, making it suitable for various applications spanning automotive repairs, plumbing, and general household fixes. Due to its strength and reliability, JB Weld is often a go-to choice for those needing a durable solution that can handle stress and load, much like a solder or welded joint would. However, the effectiveness of JB Weld can depend on the application and the preparation of the surfaces being bonded.

ABS (Acrylonitrile Butadiene Styrene) and PVC (Polyvinyl Chloride) are two types of plastic piping used in plumbing. The main differences lie in their resistance, flexibility, and application. ABS, black in color, offers greater impact resistance and is better suited for exterior, cold environments due to its low-temperature tolerance. PVC, typically white or grey, provides superior chemical resistance and is preferred for high-pressure applications and interior plumbing. While ABS is faster and easier to install due to its one-step joining process, PVC installations might require an additional step for primer. However, local building codes may dictate the specific type of pipe required, making it essential to consult them before making a decision.