Properties, Advantages and Disadvantages of PP, ABS, PC, PE, PVC, and TPR Plastics

I. Overview of Plastics

1.1 Definition and Classification of Plastics

Plastics are polymeric compounds synthesized through addition or condensation polymerization reactions using monomers as raw materials. Fundamentally, plastics consist of synthetic resins, which constitute approximately 40% to 100% of the total weight and form the basic skeleton. However, plastics are not merely composed of resins; they also contain additives such as fillers, plasticizers, stabilizers, lubricants, and colorants.

Plastics can be classified in various ways. By application, they are divided into General Plastics, Engineering Plastics, and Specialty Plastics. General Plastics, such as Polyethylene (PE) and Polypropylene (PP), are produced in large volumes at low cost for packaging and agriculture. Engineering Plastics, such as Polycarbonate (PC) and Polyamide (PA), possess excellent comprehensive properties for use in machinery and electronics. Specialty Plastics generally exhibit unique properties like heat resistance and corrosion resistance for specific occasions. Physicochemically, they are categorized as Thermoplastics and Thermosets. Thermoplastics, like PE and PVC, can be repeatedly softened by heating and solidified by cooling. Thermosets, like phenolic and epoxy plastics, cannot be reshaped once cured.

1.2 Applications of Plastics in Daily Life

Plastics are widely used in daily life. In the packaging sector, plastic films, containers, bags, and pallets are ubiquitous. Plastic films are lightweight, transparent, moisture-proof, and dust-proof, widely used for food, pharmaceuticals, and cosmetics. Plastic containers hold liquids and solids, such as beverage bottles and shampoo bottles.

In construction, plastics are used to make windows, pipes, and waterproof materials. Plastic windows offer thermal insulation, soundproofing, and aesthetics; plastic pipes are corrosion-resistant, lightweight, and easy to install for drainage and gas transmission.

In automotive manufacturing, plastics play a vital role in interiors, exteriors, and functional components like dashboards and bumpers. The use of plastics reduces vehicle weight, improves fuel economy, and enhances aesthetics and comfort.

Furthermore, plastics are extensively applied in electronics, toys, stationery, and medical devices, significantly enriching people's lives.

II. Properties, Advantages and Disadvantages of PP Plastic

2.1 Property Introduction

PP (Polypropylene) has a specific gravity of 0.9-0.91 g/cm³, making it the lightest among common plastics, only slightly denser than water. Its molding temperature ranges from 160-220°C, offering a wide processing window.

Regarding electrical properties, PP exhibits excellent insulation with a dielectric constant of around 2.1, making it suitable for wire and cable insulation, maintaining stability even in high-frequency environments.

PP retains good toughness at low temperatures and does not easily become brittle below 0°C, allowing for effective performance in cold environments.

Chemically, PP is a crystalline polymer with high heat resistance; its heat distortion temperature is 80-100°C, allowing it to be boiled in water without damage. It also possesses good stress-cracking resistance and a long flexural fatigue life, earning it the nickname "Hundred-fold Rubber" (or "living hinge" material).

2.2 Advantages Analysis

PP’s superior electrical properties make it ideal for the electrical and electronics fields, used for cable sheathing and appliance housings to ensure safety.

Its good low-temperature toughness enables applications in cold regions, such as winter sports equipment and outdoor facilities, without performance degradation due to cold.

The lightweight nature of PP significantly reduces product weight. In automotive manufacturing, PP interior and exterior parts effectively reduce vehicle weight, improve fuel economy, and facilitate transportation and installation.

PP also offers good chemical resistance against acids, alkalis, and salts, making it suitable for chemical containers and pipes. Additionally, its excellent moldability allows for various processing methods like injection and extrusion, meeting diverse shape requirements.

2.3 Disadvantage Discussion

PP has poor weather resistance. Long-term exposure to sunlight and oxygen causes aging, embrittlement, surface cracking, and loss of mechanical properties, limiting its outdoor longevity.

PP has lower dimensional accuracy; its size stability is inferior to engineering plastics due to sensitivity to processing temperature and molds.

PP lacks rigidity; compared to metals, its strength and hardness are lower, making it prone to deformation under heavy loads, unsuitable for structural parts requiring high strength.

PP is susceptible to "copper harm"; contact with copper catalyzes oxidation, accelerating the aging process, requiring caution during use.

2.4 Suitable Products

Due to its heat resistance, PP is commonly used for food containers, water cups, and fresh-keeping boxes, capable of withstanding high-temperature sterilization and microwave heating. It is used for plastic baskets, turnover boxes, and storage bins due to its light weight and durability.

In packaging, PP bottle caps offer good sealing. Its insulation and chemical resistance make it suitable for internal appliance parts and automotive interiors. Its corrosion resistance makes it a primary choice for drainage and gas pipeline systems.

2.5 Mold/Injection Molding Considerations

PP has a relatively high shrinkage rate. Mold design must account for shrinkage allowance to ensure dimensional accuracy. Uneven cooling easily leads to warpage; thus, cooling channels must be rationally designed for uniform cooling.

For thin-walled products, optimizing venting systems and runner designs is crucial to ensure complete cavity filling and avoid defects like short shots or burn marks. Proper flow rates help reduce internal stress.

III. Properties, Advantages and Disadvantages of ABS Plastic

3.1 Property Introduction

ABS (Acrylonitrile Butadiene Styrene) has a specific gravity of approximately 1.05 g/cm³. Its molding temperature is typically between 180-260°C, within which it exhibits good fluidity for easy processing.

The most prominent characteristic of ABS is its extremely high impact strength. It absorbs significant energy upon impact without breaking, providing excellent shock resistance.

It also has excellent chemical stability, resisting various acids, alkalis, and salts. Its electrical insulation is reliable for electronic components. Furthermore, ABS has good surface hardness and wear resistance, preventing scratches and maintaining aesthetics.

3.2 Advantages Analysis

ABS’s superior impact strength makes it widely used in automotive interiors and bumpers, mitigating collision forces to protect occupants and vehicles.

Its chemical stability suits it for chemical equipment and piping, resisting corrosive substances to ensure operational safety.

ABS is easy to process via injection or extrusion with high dimensional precision, suitable for precision parts. It also supports secondary processing like painting and electroplating for varied appearances.

Its insulation and wear resistance benefit electronics and machinery, ensuring safety and extending service life.

3.3 Disadvantage Discussion

ABS has average heat resistance, with a heat deflection temperature of about 93-118°C, making it prone to softening in high-temperature environments, limiting use near open flames.

Weather resistance is subpar; long-term outdoor exposure leads to aging, discoloration, gloss reduction, and mechanical degradation.

Flammability is a concern; ABS burns easily, producing black smoke and toxic gases, often requiring costly flame-retardant treatments.

Cost is higher compared to general-purpose plastics, limiting applications sensitive to budget constraints.

3.4 Suitable Products

ABS is often used for small appliance housings and charger cases, offering protection and aesthetics. In toys, it produces models due to moderate hardness and non-toxicity. Electronic accessories like phone cases utilize its precision and decorative potential. It is also suitable for computer cases, automotive exterior trims, and bathroom fittings.

3.5 Mold/Injection Molding Considerations

ABS has a low shrinkage rate (0.4%-0.7%), resulting in precise dimensions and reduced need for compensation. Its high surface gloss benefits from high-polish molds.

During injection, melt temperature must be strictly controlled (typically 200-240°C); excessive heat causes yellowing/burning, while insufficient heat affects flow. Venting in molds for appearance parts is critical to prevent bubbles and surface defects.

IV. Properties, Advantages and Disadvantages of PC Plastic

4.1 Property Introduction

PC (Polycarbonate) has a specific gravity of 1.18-1.22 g/cm³ and a molding temperature of 260-320°C. It boasts extreme transparency, with a light transmittance of up to 89% (comparable to optical glass) and low haze (0.6%).

Mechanically, PC excels with a tensile strength of 60-70 MPa, flexural strength of 90-110 MPa, and outstanding impact strength, earning it the title "unbreakable glass."

PC has good heat and cold resistance, with a heat distortion temperature of 130-140°C, maintaining stable mechanical properties between -40°C and 120°C.

4.2 Advantages Analysis

PC’s high transparency makes it ideal for optics (eyeglass lenses, camera lenses). Its mechanical strength suits protective gear (face shields, helmets).

Its thermal stability is perfect for automotive lighting, functioning reliably in extreme climates. It is also used for precision electronic parts due to dimensional stability.

In construction, PC sheets serve as glazing panels and partitions, offering lightweight installation and aesthetic appeal.

4.3 Disadvantage Discussion

PC has relatively poor chemical resistance; strong acids, bases, ketones, and esters can cause corrosion and swelling, limiting chemical applications.

PC is highly sensitive to moisture. Water in the raw material causes hydrolysis during high-temperature processing, leading to silver streaks and bubbles. Strict pre-drying is mandatory.

PC has high melt viscosity and poor flowability, requiring high injection pressure/speed and demanding equipment/molds. High internal stress post-molding can lead to stress cracking; sharp corners must be avoided in design.

4.4 Suitable Products

PC is used for transparent light covers, eyeglass frames, and face shields due to toughness. Food-contact items like water bottles benefit from its safety. Explosion-proof housings, precision electronics, and automotive lights utilize its properties. Transparent mechanical parts (gears, bearings) leverage its wear resistance.

4.5 Mold/Injection Molding Considerations

Pre-dry PC at 100-120°C for 3-4 hours to remove moisture. Mold surfaces require high polishing (Ra < 0.2μm) to minimize surface defects.

Due to poor flow, runners and gates must be rationally designed. Product structures should avoid sharp corners; radii transitions are necessary to reduce stress concentration and prevent cracking.

V. Properties, Advantages and Disadvantages of PE Plastic

5.1 Property Introduction

PE (Polyethylene) has a specific gravity of 0.94-0.96 g/cm³ and a molding temperature of 140-220°C. It offers excellent corrosion resistance against chemicals and superior electrical insulation (especially high-frequency), suitable for wire/cable insulation.

PE is categorized into HDPE, LDPE, and LLDPE. HDPE offers high strength/stiffness for packaging/piping. LDPE provides softness/transparency for films/bags. LLDPE combines toughness/strength for packaging.

5.2 Advantages Analysis

Corrosion resistance allows broad chemical industry use (containers, pipes), preventing damage from corrosive substances and ensuring safety.

Excellent insulation benefits power transmission. Good processability allows low-cost, high-efficiency production via extrusion/injection.

Daily items like bags and wrap are cheap and convenient. These advantages make PE one of the most widely used plastics.

5.3 Disadvantage Discussion

Heat aging resistance is poor; high temperatures cause softening/deformation (e.g., hot water pipes may leak).

Strength/hardness are low compared to metals, deforming under heavy loads, unsuitable for rigid structures.

Flammability produces toxic gases. Environmental persistence (non-biodegradability) raises pollution concerns.

5.4 Suitable Products

HDPE makes buckets and drums for liquids. PE pipes are standard in plumbing/gas. LDPE is used for cling film. Hoses, caps, fishing gear, and chemical containers also utilize PE.

5.5 Mold/Injection Molding Considerations

High shrinkage (1.5-3.6%) requires ample shrinkage allowance in mold design. Cooling optimization is vital to prevent warpage; uniform water flow through channels prevents deformation, especially in uneven wall thicknesses.

VI. Properties, Advantages and Disadvantages of PVC Plastic

6.1 Property Introduction

PVC (Polyvinyl Chloride) has a specific gravity of 1.35-1.45 g/cm³ and a molding temperature typically between 160-190°C.

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VII. Properties, Advantages and Disadvantages of TPR Plastic

7.1 Property Introduction

TPR (Thermoplastic Rubber) has a specific gravity ranging from 0.90-1.20 g/cm³ and a molding temperature of 160-220°C, facilitating various processing methods.

Its most notable characteristics are excellent softness and elasticity. Softness allows adaptation to complex shapes (ergonomic grips, toothbrushes). Elasticity ensures rapid recovery after force application, providing anti-deformation capability crucial for anti-slip buttons and buffer pads.

7.2 Advantages Analysis

Softness benefits baby products (nipples, teethers) requiring safe, comfortable materials. Elasticity suits seals, ensuring leak prevention.

In electronics, TPR provides anti-slip grips. It is environmentally friendly, non-toxic, recyclable, and meets green material standards.

7.3 Disadvantage Discussion

Limited heat resistance; heat deflection temperature is 60-80°C, risking softening/melting in high temperatures (e.g., engine compartments).

Poor weather resistance leads to aging, discoloration, and cracking under UV/rain exposure, reducing lifespan.

7.4 Suitable Products

Widely used for handle overmolding (tools, fitness equipment) for grip and shock absorption. Anti-slip buttons (remotes, keyboards), toothbrush handles, baby items (bottle handles, toys), seals, buffer pads, and electronic soft-grips leverage TPR’s properties.

7.5 Mold/Injection Molding Considerations

Control barrel temperature (180-220°C) and nozzle temperature (slightly lower). Mold temperature set at 40-60°C aids cooling/demolding.

Avoid excessive injection pressure to prevent internal stress/cracking. Use moderate speed to prevent melt fracture (surface defects) or short shots. Optimize holding/cooling times for dimensional accuracy.

VIII. Summary and Selection Recommendations

8.1 Summary of Properties

• PP: Lightweight, heat/chemical resistant, easy to process; but poor weather resistance, low dimensional accuracy, low rigidity.

• ABS: High impact strength, chemically stable, easy to process; but poor heat resistance, poor weather resistance, flammable, expensive.

• PC: Highly transparent, excellent mechanics, wide temperature range; but poor chemical resistance, moisture sensitive, high viscosity.

• PE: Corrosion resistant, good insulation, cheap; but low strength/hardness, flammable, non-biodegradable.

• PVC: Flame retardant, corrosion resistant, high strength; but poor heat resistance, releases hazardous gases when burned.

• TPR: Soft, elastic, eco-friendly; but poor heat resistance, poor weather resistance.

8.2 Selection Advice

• For appearance parts, select ABS for surface quality and precision.

• For food/daily use, choose cost-effective PP for its heat resistance and processability.

• For transparent/explosion-proof premium items (lenses, shields), PC is ideal.

• For corrosion/low-temp resistance, PE is suitable for containers and cold environments.

• For flame-retardant electrical materials, low-cost PVC provides good performance.

• For anti-slip/soft overmolding, TPR offers comfort and reliable elasticity.