【Daily Question】12.30 Types of corrosion in polymer materials (3 wealth points for replies; +3 to +8 wealth points for correct answers)
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This post was last edited by lzy4225925 on 2016-1-2 at 10:53. Topic: List: Please list at least three types of corrosion (aging) of polymer materials Chemical cracking, swelling, dissolution, stress cracking, penetration failure, etc. Requirements for answering questions and hints: Answer carefully. Hint: Basic definitions. Please note: We will close this thread after 24 hours, and at that time we will announce the best response (the best answer), along with the answers and explanations. Other details: Recruitment for moderators & technicians in the [Mechanical Section] – applications and referrals are welcome. 【Valid indefinitely】【If you’re interested, come ahead!】 】(Click to enter) 【Mechanical Zone】Comprehensive guide to preventing equipment freezing over during winter 【Mechanical Zone】Call for collection of essential knowledge 【Seeking manufacturer sponsors】(Ongoing campaign) Rewards for recommending valuable content; the “Active Users and Weekly Stars” competition in the Mechanical Zone has begun. Wealth, metals, corrosion, zones, machinery
Polymer aging phenomena ① Changes in appearance, such as the appearance of stains, spots, silver streaks, cracks, flaking, powdering, and changes in luster and color； ②Changes in physical properties, including solubility, swellability, rheology, as well as resistance to cold, heat, air permeability, light transmission, and water permeability ； ③Changes in mechanical properties, such as tensile strength, bending strength, compressive strength, impact strength, and elongation rate ； ④Changes in electrical properties, such as insulation resistance, dielectric loss, breakdown voltage, etc.
It can be divided into chemical aging and physical aging. Chemical aging can be divided into two types: degradation and cross-linking. Chemical aging is an irreversible chemical reaction that results from changes in the molecular structure, such as the embrittlement of plastics, cracking of rubber, and yellowing of fibers. Degradation refers to the breakage of molecular chains in polymers as a result of factors such as ultraviolet light, heat, and mechanical forces ； Crosslinking refers to the breaking of the carbon-hydrogen bonds in polymers, with the resulting polymer radicals combining with each other to form a network structure. Degradation and crosslinking have a significant impact on the properties of polymers. Degradation reduces the molecular weight of polymers, causing the material to become softer and stickier, as well as decreasing its tensile strength and modulus ； Crosslinking makes polymer materials harder and more brittle, reducing their elongation rate (see Polymer Degradation and Polymer Crosslinking). Physical aging does not involve changes in the molecular structure; it is merely a reversible change resulting from physical effects. For example, some polymer materials experience a decrease in their insulating properties when exposed to moisture, but these properties can be restored after they are dried.
Please list at least three types of corrosion (aging) of polymer materials? 1. Reduced toughness and increased brittleness 2. Degradation 3. The surface changes from smooth to rough
Chemical processes: degradation and cross-linking. Physical processes: swelling and dissolution, environmental stress cracking, permeation failure
Aging is divided into thermal aging and atmospheric aging. Polyvinyl chloride (PVC) tends to decompose when the temperature is raised above 160°C; hydrogen chloride is primarily released, and unsaturated double bonds are formed or cross-linking occurs. Polyethylene terephthalate (PET) degrades when heated to 280–320°C; the main gaseous products of this decomposition are carbon dioxide, carbon monoxide, and acetaldehyde. Other products include terephthalic acid, along with a small amount of water. Polymethyl methacrylate (PMMA), similar to polystyrene, is prone to depolymerization and undergoes thermal decomposition into methyl methacrylate at temperatures ranging from 150 to 500°C. Materials naturally deteriorate slowly when exposed to the atmosphere. When in use, storage, or processing, polymer materials are also exposed to certain climatic factors, which can **affect their properties. The factors that have a significant impact on polymer materials include solar radiation, oxygen, temperature, water, and air pollution.
Biological aging, atmospheric aging, photoaging, photo-oxidative aging, thermal aging, thermo-oxidative aging, humid-thermal aging, etc
Aging can be divided into chemical aging and physical aging.
Biological aging, atmospheric aging, photoaging, photo-oxidative aging, thermal aging, thermo-oxidative aging, wet-thermal aging, ozone aging, etc
Brittleness of plastics, cracking of rubber, yellowing of fibers
Thermal aging, atmospheric aging, mechanical degradation, chemical degradation, stress cracking, ionizing radiation, abrasion