From PVC to Silicone: How to Distinguish Raw Materials with or Without Tools
I. Core Differences in 4 Major Materials
1. PVC (Polyvinyl Chloride)
- Visual Traits: Smooth ceramic-like cross-section, blue edge glow under strong light.
- Burn Test: Self-extinguishing, black smoke, pungent hydrochloric acid odor (chlorine release).
- Key Properties:
- Density: 1.3-1.45 g/cm³
- Hardness (Shore A): 60-80
- Risk: May contain phthalates (6P restricted in toys).
2. Natural Rubber (NR)
- Visual Traits: Develops mica-like cracks when stretched, brittle at low temperatures.
- Burn Test: Continuous flame, black smoke, burnt tire smell.
- Key Properties:
- Density: 0.92-0.98 g/cm³
- Rebound rate: ≥85%
- Degrades after 18 months.
3. TPR (Thermoplastic Rubber)
- Visual Traits: Stretches 3x without breaking, no permanent deformation.
- Burn Test: Melts/drips without spreading, paraffin-like odor.
- Safety: Phthalate-free, FDA food-contact certified.
4. Silicone
- Visual Traits: No crease when folded, leaves white ash when burned.
- Density Test: Sinks in water (1.1-1.3 g/cm³).
II. 3-Second Field Tests
1. Scratch & Cold Response Matrix
- PVC:
- Nail scratch leaves white mark
- Natural Rubber:
- No scratch mark
- TPR:
- Minor dent when scratched
2. Burn Test Protocol
- Cut 1cm strip and burn it
- Observe:
- PVC: Self-extinguishes, black smoke, acidic smell
- NR: Keeps burning, black smoke, rubbery odor
- TPR: Melts/drips, yellow flame, candle-like smell
III. Cost vs Safety Analysis
Material Cost Breakdown ($/kg)
- PVC: 1.2material+0.3 processing + $0.5 compliance*
- TPR: 2.8material+0.5 processing
- Silicone: 6.5material+1.2 processing
(*REACH/EN71 certification fees)
Safety Risks
- PVC: Contains phthalates (banned in toys), releases dioxins when burned
- TPR: Food-safe (LFGB certified), 12% annual biodegradation rate
- Natural Rubber: Contains latex allergens, may have excessive zinc oxide
IV. Material Selection Flowchart
Start → Contact with children?
- Yes → Choose TPR or Silicone
- No → Need high precision?
- Yes → PVC (drawing-specific)
- No → Cost priority?
- Yes → Natural Rubber
- No → TPR
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