PP (Polypropylene) is a thermoplastic polymer produced by the polymerization of propylene monomers. It is one of the five major general-purpose plastics (along with PE, PVC, PS, and ABS). Key Characteristics: Lightweight: Density of 0.89–0.91 g/cm³, making it the lightest among commodity plastics Heat resistant: Melting point of 160–170°C; can withstand boiling water and high-temperature sterilization Chemical resistance: Resistant to acids, alkalis, and most organic solvents, but vulnerable to concentrated sulfuric and nitric acids Mechanical properties: Good rigidity and excellent flexural endurance (often called the "hinge plastic" because it can be bent repeatedly without breaking) Electrical insulation: Excellent Disadvantages: Becomes brittle at low temperatures, poor aging resistance (requires antioxidants), and difficult to print on Typical Applications: Food containers (microwave-safe lunch boxes, yogurt cups, disposable takeout containers) Medical devices (syringes, IV bottles) Automotive parts (bumpers, interior trim) Home appliances (washing machine drums, fan blades) Woven bags and non-woven fabrics (masks, shopping bags) Recycling Symbol: Code 5 (a triangle with the number 5 inside, with PP printed below). Safety: Food-grade PP is recognized as a safe plastic. It can withstand temperatures up to approximately 120°C and is microwave-safe (though note that some PP lids may be made of different materials). When burned, it produces a yellow flame with a blue base, smells like paraffin (candle wax), and drips like candle wax.

Simply put, PS material (Polystyrene) is a thermoplastic polymer made by polymerizing styrene monomers. You can think of it as a plastic that is as transparent as glass, but lighter in weight and less likely to break. It is very common in daily life — for example, disposable cups, transparent cake boxes, and appliance housings. Below are its key characteristics. 1. Two Most Common Types Type Characteristics Like... Common Examples GPPS (General Purpose Polystyrene) Transparent, hard, but very brittle — easily cracks or breaks Glass or hard ice Transparent CD cases, disposable clear cups, laboratory test tube racks HIPS (High Impact Polystyrene) White or colored, tough, impact-resistant Rigid plastic White air conditioner housings, TV back covers, toys, clothes hangers Note: EPS (Expanded Polystyrene) is also part of the PS family — it's the white foam material (e.g., protective foam in appliance packaging, disposable foam lunch boxes). 2. Key Advantages and Disadvantages Advantages: High transparency (GPPS) — clarity acrylic (PMMA). Good rigidity — hard and not easily deformed. Easy to process — can be injection molded, extruded, thermoformed. Low cost — cheaper than PC or acrylic. Disadvantages: Not heat-resistant — softens above 75°C (167°F), so not suitable for boiling water. Poor outdoor durability — yellows and becomes brittle with prolonged sun exposure. Brittleness (GPPS) — like glass, cracks upon impact. 3. How to Identify PS Material? Recycling symbol: Look for the number 6 inside the triangular recycling symbol. Sound: Tapping a thin-walled PS product produces a crisp, metallic-like sound. Feel: It is relatively hard — not easy to leave a fingernail mark like on PP (polypropylene). 4. Safety and Environmental Impact Food contact: Food-grade PS is safe for food packaging (e.g., yogurt cups, instant noodle bowls). However, it is not recommended for hot, oily foods (e.g., freshly fried fries), as high temperatures may cause trace amounts of styrene monomer to migrate. Environmental impact: PS is technically recyclable, but EPS (foam) is often landfilled because it is bulky and expensive to recycle. It is not biodegradable.

PC material (Polycarbonate) is an exceptionally high-performance engineering thermoplastic. You can think of it as a transparent material that is lighter than glass, stronger than ordinary plastics, and extremely tough. The key difference between PC and PS or PMMA is that PC has extremely high impact strength and is commonly used in "bulletproof glass." 1. Key Advantages Extremely High Impact Resistance – This is PC's most famous property. Its impact strength is 30–40 times that of PMMA (acrylic) and over 200 times that of ordinary glass. It is very tough and typically deforms rather than shatters under strong impact. Examples: Bulletproof glass, transparent riot shields for police, visors for safety helmets. Excellent Light Transmittance – Though not as high as PMMA (92%), PC still achieves 88–90% light transmission, making it clear enough for optical lenses. Outstanding Heat Resistance – PC maintains its performance over a long-term temperature range of -40°C to 120°C. Its heat deflection temperature reaches 130–140°C, far higher than PS (~75°C) and PMMA (~95°C). Examples: Microwaveable plastic food containers, kettle housings, baby bottles. Good Dimensional Stability – PC does not deform easily under stress or temperature changes, offering high dimensional precision. 2. Main Disadvantages & Precautions Poor Scratch Resistance – PC has low surface hardness and scratches very easily. Many PC products (e.g., eyeglass lenses, phone screen protectors) are coated with a hard coating to improve abrasion resistance. Poor Chemical Resistance – PC is easily attacked by certain organic solvents (e.g., gasoline, alcohol, cleaning agents), leading to surface cracking or "stress cracking." Special care is needed during use and cleaning. Higher Cost – As an engineering plastic, PC is more expensive than commodity plastics like PS, PMMA, and PP. BPA (Bisphenol A) Concerns – This is the most notable safety issue with PC material. BPA is used in PC synthesis. Under high heat or prolonged use, trace amounts of BPA may leach out. BPA is an endocrine disruptor that may affect infant development. As a result, many baby bottles are no longer made from PC and instead use safer materials like PPSU or PP. However, adult-grade water bottles are generally considered safe. 3. Quick Comparison: PC vs. PMMA vs. PS Property PC (Polycarbonate) PMMA (Acrylic) PS (Polystyrene) Impact Resistance Extremely high (bulletproof level) Medium-high (stronger than glass) Low (brittle) Light Transmittance 88–90% (transparent) Highest (92%) 88–90% (transparent) Heat Resistance Best (~130°C) Medium (~95°C) Poor (~75°C) Surface Hardness Soft, scratches very easily Soft, scratches easily Harder, resists scratching Cost High Medium Low Typical Applications Bulletproof glass, helmets, baby bottles, CDs Signage, aquariums, eyeglass lenses Disposable cups, CD cases, appliance housings Safety Concern BPA (Bisphenol A) None Styrene monomer 4. How to Identify PC Material? Recycling Symbol: Look for the number 7 (Other) inside the triangular recycling symbol, which often indicates PC or other mixed plastics. Sound: Tapping a PC product produces a dull, solid sound, unlike the crisp sound of PS. Labeling: Many PC water bottles or food containers are marked "BPA Free," a common label for PC and its alternatives.

PMMA stands for Poly(methyl methacrylate). It is a transparent thermoplastic commonly known by brand names such as acrylic or Plexiglas, and is often referred to as "organic glass." While PS (polystyrene) is also a clear plastic, PMMA is generally considered a higher-performance material and is frequently used as a lightweight, shatter-resistant alternative to glass. Key Characteristics Excellent Transparency – PMMA transmits up to 92% of visible light, even more than standard glass. Impact Resistant – Its impact resistance is 7 to 18 times higher than ordinary glass. Lightweight – Its density is about 1.15–1.19 g/cm³, roughly half the weight of glass. Easy to Process – Can be easily machined (cut, drilled) and thermoformed.   At a Glance Property Value Visible Light Transmission Up to 92% Density 1.17–1.20 g/cm³ Impact Resistance (vs. glass) 7–18x stronger Max Continuous Service Temp 65–95°C (149–203°F) Surface Hardness Low (scratches easily) Limitations Heat sensitive – Softens around 100°C (212°F); not for cookware. Flammable – Burns readily. Scratches easily – Often requires a protective coating. Common Applications Optics (eyeglass lenses, camera lenses) Electronics (LCD screens, light guide panels) Construction (aquariums, skylights) Automotive (rear lights, instrument clusters) Medical (incubators, dental prosthetics) PMMA vs. PS Property PMMA (Acrylic) PS (Polystyrene) Clarity Superior (92%) Good (88–90%) Impact Strength High Low (brittle) Weather Resistance Excellent Poor (yellows outdoors) Typical Use Aquariums, lenses, signage Disposable cups, CD cases