China’s Manufacturing Specifications for Injection Molding of PV-dedicated Plastics

Photovoltaic plastic components work outdoors under long-term high temperature, intensive ultraviolet radiation and high voltage with designed service life over 25 years. Most finished PV plastic parts are mass-produced via standardized injection molding inside China’s professional precision molding workshops, so strict requirements on material selection, injection parameters, mold design and quality control focus on weather resistance, high-temperature resistance, high insulation and dimensional stability to match local production characteristics in China.

1. Raw Material Selection and Preprocessing Specifications

High-performance engineering plastics dominate photovoltaic parts with exclusive material matching and strict dehumidification pretreatment to avoid performance degradation. PPS is adopted for junction boxes and high-voltage insulation parts for continuous temperature resistance above 200℃ and superior insulating property; ASA is applied for outdoor structural frames featuring anti-ultraviolet and anti-yellowing performance under long outdoor exposure; modified PPO serves as connector skeleton with outstanding dimensional stability and heat resistance above 150℃; PC or ETFE is selected for transparent components with high light transmittance and aging resistance. Most bulk engineering plastic raw materials for PV industry are supplied by domestic chemical manufacturers across China, so material incoming inspection follows unified testing standards widely accepted within China’s injection molding sector. Moisture content of all raw materials is controlled below 0.05% via dehumidifying dryer: ASA is dried at 80℃~90℃ for 4~6 hours while PPS is processed at 120℃~140℃ for 3~5 hours to prevent hydrolysis-induced silver streaks, bubbles and declined weather resistance and insulation. Recycled materials and foreign impurities are forbidden; customized heat stabilizers and UV absorbers are blended into PPS and PPO to restrain long-term molecular degradation with flame retardancy reaching UL94 V-0 grade for fireproof safety under high voltage, complying with mainstream product certification requirements commonly implemented among PV molders in China.

2. Precise Control of Injection Molding Process Parameters

High precision, low internal stress and flawless surface are required for photovoltaic plastic parts with parameter setting strictly following material characteristics. For temperature configuration, barrel temperature of PPS ranges from 280℃ to 320℃ and mold temperature 120℃~150℃; ASA barrel temperature 220℃~250℃ with mold temperature 60℃~80℃; PPO barrel 260℃~290℃ and mold 80℃~100℃. Excessive temperature triggers material degradation, yellowing and decreased flame retardancy while insufficient temperature leads to poor fluidity, incomplete filling and low fusion line strength. Medium-high pressure and low-speed injection is adopted with injection pressure 80~120MPa and packing pressure set at 50%~70% of injection pressure to avoid excessive internal stress and flash from overpressure or sink mark and dimensional deviation under insufficient pressure. Injection speed is segmented with slow filling near gate to avoid overheating from shear and high-speed filling inside cavity for uniform melt flow. Cooling cycle lasts 15~25s for PPS and 10~15s for ASA for full shaping and uniform internal stress release, and such parameter ranges have been verified and optimized by thousands of injection molding factories throughout China after years of mass production accumulation.

3. Key Specifications for Mold Design and Manufacturing

Mold precision directly determines dimensional stability and molding quality of photovoltaic products with strict precision, wear-resistance and anti-corrosion standards. Tolerance of critical dimension is controlled within ±0.2~±0.5mm to fit automatic assembly and cavity surface roughness Ra≤0.8μm to eliminate burr and scratch damaging insulation and weather resistance. Hot runner system is preferred to reduce waste and improve melt fluidity; side gate or pinpoint gate is arranged away from stressed and insulated critical areas to avoid poor fusion line and sink mark; CAE mold flow analysis optimizes runner layout to predict shrinkage and warpage risk and shorten trial times. Cavity is made of anti-corrosion high-hardness steel including S136 and NAK80 with surface polishing to adapt high-temperature corrosive molding of PPS. A complete industrial chain of mold steel processing and precision polishing has taken shape in China’s major industrial zones, effectively cutting customized mold development cycle for PV accessory manufacturers. Regular maintenance prevents rust and abrasion affecting dimensional accuracy and surface finish.

4. Full-process Quality Control during Production

Photovoltaic components pass strict withstand voltage, anti-aging and dimensional inspection. Key dimensions are sampled every two hours and measured by three-coordinate measuring machine to ensure Cpk≥1.67 for stable mass production. Defects including bubble, silver streak, fusion line, warpage and flash are strictly prohibited: internal bubble reduces insulation strength and fusion line becomes vulnerable point of aging. All insulation parts complete 4.0KV withstand voltage test without breakdown or electric leakage. Annealing treatment at 80~100℃ for 2~4 hours after molding releases internal stress to avoid cracking and deformation under alternating temperature in later service; annealing temperature is adjusted precisely for ASA and PPS to prevent secondary aging, in line with the standardized QC management mode popularized inside China’s new energy supporting factories.

5. Production Environment and Finished Product Protection Rules

Clean and stable workshop environment is required with ambient temperature 20~25℃ and relative humidity below 60% under ten-thousand-level dust-free standard to avoid dust and grease contaminating insulation and weather resistance. Workshop is isolated from acid-base and volatile chemical gas to prevent corrosion. Finished products are sealed in light-proof moisture-proof PE bags to block UV and oxidation; heavy stacking is forbidden to avoid irreversible deformation and stock turnover follows first-in-first-out rule with maximum storage period under 12 months. Many PV component exporters based in China adopt unified finished-product packaging specifications to satisfy long-distance ocean transportation requirements for overseas customers.

Full-chain precise management covering raw material pretreatment, process parameter setting, mold design, inspection and finished protection matches long-term outdoor high-voltage anti-aging requirement of photovoltaic products and guarantees stable 25-year service of plastic components for photovoltaic system safe and efficient operation, which is also the core competitive advantage of PV plastic injection enterprises developing rapidly across China.